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Applied Catalysis B, Environmental (v.101, #3-4)

IFC Editorial Board (pp. co2).

Contents (pp. co4).

Editorial Board (pp. i).

Contents Continued (pp. i-ii).

Effect of potassium addition on catalytic activity of SrTiO₃ catalyst for diesel soot combustion by B. Ura; J. Trawczyński; A. Kotarba; W. Bieniasz; M.J. Illán-Gómez; A. Bueno-López; F.E. López-Suárez (pp. 169-175).

Display Omitted▶ The positive effect of potassium addition on the catalytic activity of strontium titanate in soot oxidation can be interpreted in terms of two mechanisms of potassium action: enhancement of oxygen surface mobility and oxygen vacancies formation in the oxygen sublattice of perovskite structure depending on the potassium localization. ▶ The experimental results (potassium volatility, work function changes, basicity, XPS spectroscopy) revealed that the vacancy mechanism is the most efficient in stimulating the soot combustion catalytic reactivity of strontium titanate.SrTiO₃ based mixed oxides with perovskite-like structure were prepared by sol–gel citric method. The potassium promoter (2mol%) was introduced into the material during the synthesis as well as via post-impregnation, leading to two different catalytic systems: Sr_0.8K_0.2TiO₃, and K/SrTiO₃, respectively. The obtained materials were characterized by XRD, S_BET, cyclohexanol (CHOL) decomposition, XPS and SR-TAD (species resolved thermal alkali desorption), whereas their catalytic activity in soot combustion was examined in laboratory conditions. It has been shown that introduction of potassium substantially promotes the catalysts activity, which can be gauged by the lowering of the soot ignition temperature by 100°C for K/SrTiO₃ and 120°C for Sr_0.8K_0.2TiO₃. The effect is discussed in terms of potassium volatility, work function changes and basicity, however the experimental data revealed that the indirect effect is also involved. The most active system was obtained when potassium partially substituted strontium in the perovskite structure. As a consequence oxygen vacancies were created, leading to higher concentration of basic surface oxygen species. Since in the case of Sr_0.8K_0.2TiO₃, K⁺ ions are located in the structural positions, this catalyst apart from the highest activity exhibits also the highest potassium stability.

Keywords: Strontium titanate; Perovskite; Soot combustion; Potassium stability; Catalyst

Behaviour of TiO₂–SiMgO_x hybrid composites on the solar photocatalytic degradation of polluted air by S. Suárez; T.L.R. Hewer; R. Portela; M.D. Hernández-Alonso; R.S. Freire; B. Sánchez (pp. 176-182).

Display Omitted▶ TiO₂–SiMgO_x hybrid composites are evaluated for the photodegradation of trichloroethylene in gas phase with a CPC solar reactor. ▶ Combination of an adsorbent and a photocatalyst widens the operating conditions window of the system. ▶ CO₂ selectivity is promoted at high solar irradiance conditions. ▶ TiO₂–SiMgO_x composite allows total TCE degradation at severe operating conditions.The photocatalytic performance of TiO₂–SiMgO_x ceramic plates for trichloroethylene abatement in gas phase has been evaluated under sun irradiance conditions. A continuous flow Pyrex glass reactor fixed on the focus of a compound parabolic collector has been used. The performance of the hybrid photocatalyst has been evaluated as the variation of TCE conversion and reaction products formation with the solar irradiance at different total gas flow, TCE concentration, and water vapour content. SiMgO_x not only provides adsorbent properties to the photocatalyst, but it also allows the effective use of the material during low solar irradiance conditions. The adsorption–desorption phenomena play a pivotal role in the behaviour of the system. Thus, TCE conversion curves present two different branches when the sun irradiance increases (sunrise) or decreases (sunset). CO₂, COCl₂ and DCAC were the most relevant products detected. Meanwhile CO₂ concentration was insensitive to the branch analysed, COCl₂ or DCAC were not indicating the ability of these compounds to be adsorbed on the composite. An increase of the UV irradiation at total TCE conversion promotes the CO₂ selectivity. The excess of energy arriving to the reactor favours the direct reaction pathway to produce CO₂. The photonic efficiency, calculated as a function of the rate of CO₂ formation, decreases linearly with the solar irradiance up to around 2mWcm⁻², where it becomes constant. For decontamination systems high TCE conversion is pursuit and then high solar irradiance values are required, in spite of lower photonic efficiency values. The present photocatalyst configuration, with only 17% of the reactor volume filled with the photoactive material, allows total TCE conversion for 150ppm and 1Lmin⁻¹ in a wide sun irradiance window from 2 to 4mWcm⁻². The incorporation of water vapour leads to an increase of the CO₂ selectivity keeping the TCE conversion around 90%, although significant amounts of COCl₂ were observed.

Keywords: TiO; ₂; –SiMgO; _x; Sepiolite; Hybrid photocatalysts; Trichloroethylene (TCE); Adsorption; VOC; Compound parabolic collector (CPC); Sunlight irradiance; Solar photocatalysis; Ceramic plates

Alkali resistant Cu/zeolite deNO_x catalysts for flue gas cleaning in biomass fired applications by Siva Sankar Reddy Putluru; Anders Riisager; Rasmus Fehrmann (pp. 183-188).

.Display Omitted▶ Promising catalysts for flue gas cleaning in biomass fired applications. ▶ Cu/zeolites are less toxic, highly active and alkali poison resistant. ▶ Cu/zeolites can perform within SCR operating temperature region.Cu/zeolite catalysts have been prepared by wet impregnation and characterized by N₂ physisorption, EPR, H₂-TPR and NH₃-TPD methods. The Cu content was varied to optimize the loading as well as surface acidity. Optimized Cu/zeolite catalysts showed high surface acidity and excellent activity in the selective catalytic reduction (SCR) of NO with NH_3. Furthermore, Cu/zeolite catalysts showed high SCR activity even after doping with potassium (0–500μmol/g) compared to a commercial vanadium catalyst which deactivated at lower potassium content. Fresh and deactivated catalysts were further examined to investigate the redox and acidic properties of the catalysts. The poisoning resistivity seems to be due to a combination of high surface area and strong acidity of the Cu/zeolite catalysts. The catalysts might be attractive alternatives to conventional catalysts for deNO_x of flue gases from biomass fired power plants and other stationary industrial installations.

Keywords: SCR of NO with NH; ₃; H; ₂; -TPR; NH; ₃; -TPD; Cu/zeolite; Potassium poisoning

Tuning the size and shape of Fe nanoparticles on carbon nanofibers for catalytic ammonia decomposition by Xuezhi Duan; Gang Qian; Xinggui Zhou; Zhijun Sui; De Chen; Weikang Yuan (pp. 189-196).

Display Omitted▶ Fe catalysts were prepared by catalytic CVD growth of CNFs. ▶ Well faceted Fe nanoparticles were obtained on top of the CNFs. ▶ They are highly active and stable for ammonia decomposition to hydrogen. ▶ The activity of Fe particles on platelet CNFs is better than on fishbone CNFs.Fe nanoparticles on the top of carbon nanofibers (CNFs) were synthesized by catalytic CVD on a purpose as catalysts for ammonia decomposition. The size and shape of Fe particles on the top of CNFs depended on the Fe particle reconstruction and CNF morphology. On a mica support Fe catalyst, platelet structure of CNFs was obtained with small, uniform, and unwrapped Fe particles on the top. HRTEM illustrated that the Fe particle surface is covered by a few graphene layers, which redissolves into the Fe particle and does not prevent the access of NH₃ to active surface sites at reaction conditions. The catalyst is highly active and stable because the Fe particles are highly dispersed and physically isolated by CNFs, and the surfaces are largely exposed to the reactants.

Keywords: Ammonia decomposition; Hydrogen generation; Iron catalyst; Carbon nanofibers; Mica

Degradation of Acid Orange 7 using a saponite-based catalyst in wet hydrogen peroxide oxidation: Kinetic study with the Fermi's equation by J. Herney-Ramirez; Adrián M.T. Silva; Miguel A. Vicente; Carlos A. Costa; Luis M. Madeira (pp. 197-205).

Display Omitted▶ Acid Orange 7 is degraded by a heterogeneous catalytic wet hydrogen peroxide process in less than 4h. ▶ The catalyst, a pillared saponite clay impregnated with Fe(II) acetylacetonate (16wt.% of iron), is very active (and also stable-low leaching). ▶ Temperature has a dominant effect in the process performance. ▶ Kinetics is based on the Fermi's equation, with remarkable adherence of the model to the experimental data.In the current work, the degradation of Acid Orange 7 (also called Orange II – OII) by a heterogeneous catalytic wet hydrogen peroxide process has been described by a simple semi-empirical kinetic model, based on the Fermi's equation, which captures simultaneously the influence of all the reaction conditions with few adjustable parameters. Complete decolorization was reached in less than 4h, using as catalyst a pillared saponite clay impregnated with Fe(II) acetylacetonate (16wt.% of iron) in a slurry batch reactor. The model was fitted to the dye concentration histories, being the kinetic parameters determined by non-linear regression. The adherence of the model to the data was remarkable, and the effect of the operating conditions (temperature, catalyst dose and both pollutant and hydrogen peroxide concentration) on the fitting parameters – apparent rate constant and transition time – was analyzed.

Keywords: Acid Orange 7 (Orange II); Hydrogen peroxide; Oxidation; Fe-containing pillared clay; Reaction kinetics; Fermi's equation

Photocatalytic degradation of 2-propanol over metal-ion-loaded titanium(IV) oxide under visible light irradiation: Effect of physical properties of nano-crystalline titanium(IV) oxide by Sho Kitano; Keiji Hashimoto; Hiroshi Kominami (pp. 206-211).

Display Omitted▶ Metal-ion modified TiO₂ samples (M⁺/TiO₂'s) were prepared using adsorption method. ▶ M⁺/TiO₂'s were used for photocatalytic degradation of 2-propanol. ▶ Rh³⁺/TiO₂ exhibited higher levels of activity under visible light irradiation. ▶ Balance of surface area and crystallinity of TiO₂ is important in Rh³⁺/TiO₂.Using the adsorption method, small amounts of rhodium ion (Rh³⁺) or copper ion (Cu²⁺) were loaded on nanocrystalline titanium(IV) oxide (TiO₂) with various physical properties prepared by the HyCOM (hydrothermal crystallization in organic media) method and subsequent calcination at various temperatures. In photocatalytic degradation of 2-propanol under visible light irradiation, Rh³⁺-modified HyCOM-TiO₂ samples exhibited higher levels of activity than did Cu²⁺-modified HyCOM-TiO₂ samples and the nitrogen-doped TiO₂ sample. The Rh³⁺-modified HyCOM-TiO₂ samples showed a volcano-like tendency with calcination temperature, suggesting that the balance of surface area and crystallinity of TiO₂ is important in an Rh³⁺/TiO₂ photocatalyst. Rutile-type TiO₂ modified with Cu²⁺ exhibited the highest level of activity among the Cu²⁺/HyCOM-TiO₂ samples.

Keywords: Photocatalyst; Visible light; Rhodium ion; Copper ion; TiO; ₂; Degradation of 2-propanol

Photocatalytic inactivation of microorganisms using nanotubular TiO₂ by Nir Baram; David Starosvetsky; Jeana Starosvetsky; Marina Epshtein; Robert Armon; Yair Ein-Eli (pp. 212-219).

Display Omitted▶ When working with Escherichia coli bacteria, regeneration treatment is needed after several cycles. ▶ E. coli bacteria were deactivated efficiently under a direct sunlight irradiation. ▶ The solution pH mainly affects on the incubation period at the initial step of the photocatalysis.Photocatalysis is a well known process for deactivation contaminations in aqueous solutions. However, enhancing the photocatalytic process efficiency remains a challenge and a subject of extensive research. In this paper, nanotubular TiO₂ oxide layer with high surface area was grown and was used as a photocatalyst, inactivating Escherichia coli bacteria and other microorganisms, as well. The photocatalytic process was studied and optimized, subsequent to filtration of the nutrient broth, using saline solution. The double layer capacitance in the interface between the oxide and the solution was measured with the use of electrochemical impedance spectroscopy method and the isoelectric point was found to be at a pH value of 6.8. This result was correlated to the photocatalytic bacteria's inactivation rate in different pH solution. One of the advantages of using immobilized TiO₂ over a powdery photocatalyst is its ability to be recycled and reused. This was well studied with photocatalytic inactivation cycles of the E. coli bacteria along with MeO degradation. It was found that while no concern of reusing the TiO₂ during MeO degradation do exist, the need for a regeneration treatment after several cycles of inactivation E. coli bacteria emerges. Finally, E. coli bacteria were deactivated under a direct sunlight irradiation. This process is proven to be an efficient method for a future commercial photocatalytic cell fabrication.

Keywords: Anodization; Photocatalysis; Escherichia coli; TiO; ₂; Nanotubes

Co promotion of sonochemically prepared MoS₂/Al₂O₃ by impregnation with Co(acac)₂·2H₂O by Sang Il Lee; Ara Cho; Jae Hyun Koh; Seung Hoon Oh; Sang Heup Moon (pp. 220-225).

Display Omitted▶ CoMoS/Al₂O₃ catalyst prepared by impregnating sonochemically synthesized MoS₂/Al₂O₃ catalyst with Co(acac)₂·2H₂O is very active in the HDS of DBT and 4,6-DMDBT. ▶ Co(acac)₂·2H₂O preferentially deposits on the MoS₂ species. ▶ Co(acac)₂·2H₂O promotes the formation of the catalytically active CoMoS phases and suppresses the formation of the inactive Co₉S₈ phases.A highly active CoMoS/Al₂O₃ catalyst was prepared by sonochemically synthesizing MoS₂ crystallites dispersed on Al₂O₃ and subsequently impregnating the prepared MoS₂/Al₂O₃ with Co(acac)₂·2H₂O. The formation of the catalytically active CoMoS phase was promoted when Co(acac)₂·2H₂O, instead of relatively common Co(NO₃)₂·6H₂O, was used as a Co precursor. As a result, the newly prepared catalyst exhibited about two times higher activity for the hydrodesulfurization (HDS) of dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT) than in the case of a catalyst prepared by the sonochemical synthesis of MoS₂/Al₂O₃ followed by impregnation with Co(NO₃)₂·6H₂O, and even about four times higher than the activity of a catalyst prepared by sequential impregnation with Mo and Co compounds. The newly prepared catalyst enhanced the direct desulfurization (DDS) route to a greater extent than the hydrogenation route (HYD).

Keywords: Hydrodesulfurization; CoMo; Sonochemical synthesis; Co-acetylacetonate; Dibenzothiophene; 4,6-Dimethyldibenzothiophene

Zone-coated Rh-based monolithic catalyst for autothermal reforming of diesel by Xanthias Karatzas; Jazaer Dawody; Ann Grant; Erik Elm Svensson; Lars J. Pettersson (pp. 226-238).

Display Omitted▶ The zone-coated monolithic catalyst, covered with the two washcoats Rh_1.0Pt_1.0–Ce₁₀La_5.0/δ-Al₂O₃ and Rh_3.0–Ce₁₀La₁₀/δ-Al₂O₃, respectively, was found to be most active for ATR of commercial low-sulfur and Fischer–Tropsch diesel both during bench-scale and industrial-scale operations. ▶ XRD, H₂-TPR and XPS analyses made on Rh_1.0Pt_1.0–Ce₁₀La_5.0/δ-Al₂O₃ and Rh_3.0–Ce₁₀La₁₀/δ-Al₂O₃, showed the presence of dispersed lanthanum cerium oxides (CeO₂), metallic platinum and rhodium oxides in the washcoats. ▶ XPS analysis made on the aged zoned catalyst showed clear evidence of initial partial oxidation followed by steam reforming occurring in situ. The analysis also showed the presence of C₁-species in the first washcoat (Rh_1.0Pt_1.0–Ce₁₀La_5.0/δ-Al₂O₃) and severe sintering and migration of the active metal particles. These effects and mechanisms were less prominent in the second washcoat layer (Rh_3.0–Ce₁₀La₁₀/δ-Al₂O₃) of the catalyst.In this work we present results of hydrogen generation from diesel via autothermal reforming (ATR) obtained with monolithic catalysts consisting of either one or two layers of monometallic Rh and bimetallic RhPt washcoats. The Rh metal loading of the monometallic washcoats was varied between 0.5, 1.0 and 3.0wt%, while the weight ratio of Rh:Pt in the bimetallic washcoats was kept constant at 1:1. Furthermore, non-doped and CeLa-doped catalysts were also tested to detect differences in catalyst activity. The catalysts consisting of two layers of washcoats were termed zoned catalysts and each layer was applied to some given length in the axial direction of the monolith. All catalysts were prepared by impregnation using the incipient wetness technique with δ-Al₂O₃ as support and deposited onto 400cpsi cordierite monoliths. A total of eight catalysts, including both single layered and zone-coated, were tested in a bench-scale reactor using low-sulfur diesel as fuel at operating conditions H₂O/C=2.5, O₂/C=0.49 ( λ=0.33), GHSV=17,000h⁻¹ and P=1atm. The results showed that the zoned catalyst, covered with the two washcoats Rh_1.0Pt_1.0–Ce₁₀La_5.0/δ-Al₂O₃ and Rh_3.0–Ce₁₀La₁₀/δ-Al₂O₃, respectively, was most active in terms of fuel conversion and hydrogen production. The zoned catalyst's long-term performance and stability was also evaluated in a full-scale reactor using low-sulfur and Fischer–Tropsch diesels at operating conditions H₂O/C=2.5, O₂/C=0.49 ( λ=0.33), GHSV=10,800h⁻¹, P=1atm, and at H₂O/C=2.4, O₂/C=0.39 ( λ=0.26), GHSV=10,200h⁻¹, P=1atm, respectively. The results showed that high fuel conversion and hydrogen production were obtained from both fuels. In addition, partial oxidation and steam reforming reactions were identified by closely studying the distribution of the analyzed product gas composition and the temperature measurements. Fresh and aged samples of the catalysts were characterized by N₂-BET, H₂ chemisorption, XRD, H₂-TPR, O₂-TPO and XPS analyses.

Keywords: Autothermal reforming; Diesel; Rhodium; Zone-coated monolithic catalyst

Hydrodeoxygenation of guaiacol with CoMo catalysts. Part I: Promoting effect of cobalt on HDO selectivity and activity by Van Ngoc Bui; Dorothée Laurenti; Pavel Afanasiev; Christophe Geantet (pp. 239-245).

Display Omitted▶ Bulk and γ-alumina-supported MoS₂ and CoMoS catalysts have been evaluated in guaiacol HDO. ▶ Co promotion favored DDO pathway in guaiacol transformation. ▶ With CoMoS catalysts guaiacol can be converted directly to phenol by demethoxylation step.Unsupported and alumina-supported MoS₂ and CoMoS catalysts have been compared in the hydrodeoxygenation (HDO) reaction of guaiacol (2-methoxyphenol), a typical model molecule for bio-oils coming from the pyrolysis of ligno-cellulosic biomass. The goal of this work was to understand the cobalt promoting effect on MoS₂ phase in this type of catalytic reaction. It appeared clearly that in the presence of the CoMoS phase, the direct deoxygenation (DDO) pathway involved in guaiacol conversion was strongly increased as compared to the non-promoted MoS₂ in the bulk or supported state. This effect is similar to the well-known increase of direct desulfurization (DDS) pathway by cobalt promoter in the hydrodesulfurization (HDS) of refractory sulfur compounds over molybdenum sulfide catalysts.

Keywords: Abbreviations; DME; demethylation; DMO; demethoxylation; GUA; guaiacol; CAT; catechol; PHE; phenol; Me-CAT; methyl-catechol; Me-PHE; methyl-phenolHydrodeoxygenation; Guaiacol; MoS; ₂; CoMoS; MoS; ₂; /Al; ₂; O; ₃; CoMoS/Al; ₂; O; ₃

Hydrodeoxygenation of guaiacol by Van Ngoc Bui; Dorothée Laurenti; Pierre Delichère; Christophe Geantet (pp. 246-255).

Display Omitted▶ γ-Alumina, titania and zirconia supported MoS₂ and CoMoS catalysts have been used in guaiacol HDO. ▶ Fantastic catalytic activity when ZrO₂ was used as support for CoMoS phase. ▶ With CoMoS/ZrO₂ guaiacol was transformed successively into phenol and benzene.Bio-oils coming from ligno-cellulosic biomass are suitable material for the production of second generation biofuels. The oxygenated compounds have to be eliminated to confer good properties to these bio-oils and to permit their addition to traditional fuels. Hydrodeoxygenation (HDO) process which allows O-elimination by C–O bond cleavage under H₂ can be realized with the same type of catalysts as those used in HDS, supported CoMoS or NiMoS phases. In this work, the support effect associated with CoMoS catalysts has been investigated in guaiacol HDO reaction. Zirconia and titania supports have been compared with the traditional industrially used γ-alumina and it appeared that zirconia as support gave very efficient conversion of guaiacol into deoxygenated hydrocarbons with a totally different selectivity. The difference in selectivity allowed us to propose a different reaction scheme compared to γ-alumina and titania supported CoMoS.

Keywords: Abbreviations; DME; demethylation; DMO; demethoxylation; GUA; guaiacol; CAT; catechol; PHE; phenol; Me-CAT; methyl-catechol; Me-PHE; methyl-phenolGuaiacol; Hydrodeoxygenation; Support effect; CoMoS/Al; ₂; O; ₃; CoMoS/TiO; ₂; CoMoS/ZrO; ₂

CO-free hydrogen production over Au/CeO₂–Fe₂O₃ catalysts: Part 1. Impact of the support composition on the performance for the preferential CO oxidation reaction by T. Tabakova; G. Avgouropoulos; J. Papavasiliou; M. Manzoli; F. Boccuzzi; K. Tenchev; F. Vindigni; T. Ioannides (pp. 256-265).

Activity and selectivity towards CO₂ production over gold catalysts supported on mixed Ce–Fe oxides.Display Omitted▶ Mixed Ce–Fe oxides are used as support of gold catalysts. ▶ The support composition influences strongly the performance for the PROX reaction. ▶ The variation of the support composition causes different gold particles size. ▶ Fe₂O₃ in the supports composition improves the resistance towards deactivation by CO₂.Ce–Fe mixed oxides were prepared by urea gelation coprecipitation method and used as supports of gold catalysts. The impact of the support composition on the catalytic performance for the preferential CO oxidation (PROX) was studied by varying the Ce/(Ce+Fe) ratio. A deep characterization study by different tools such as XRD, HRTEM, TPR and FTIR spectroscopy was undertaken in order to correlate the structural characteristics of the catalysts and the gold oxidation state and dispersion with the catalytic properties. The results revealed that the variation of the support composition led to significant differences in the gold particles size (in the range 1–25nm), which affected strongly the CO oxidation activity of Au/CeO₂–Fe₂O₃ catalysts under PROX conditions. The following activity order was observed: Au/CeO₂≈Au/Ce50Fe50>Au/Ce75Fe25>Au/Ce25Fe75>Au/Fe₂O₃. The support with composition 50wt.% CeO₂–50wt.% Fe₂O₃ appeared beneficial not only for nucleation and growth of highly dispersed gold particles (1–1.8nm), but also for activation of oxygen and its mobility. Moreover, the presence of Fe₂O₃ in the supports composition improved the resistance towards deactivation by CO₂. The CeO₂–Fe₂O₃ supports comprised different amount of two phases: cubic CeO₂-like solid solution and hematite. The analysis of the characterization data suggested that the solid solution formation probably proceeded via a dopant interstitial compensation mechanism.

Keywords: Gold catalysts; CeO; ₂; –Fe; ₂; O; ₃; Preferential CO oxidation; Hydrogen production; PROX; HRTEM; FTIR

CO-free hydrogen production over Au/CeO₂–Fe₂O₃ catalysts: Part 2. Impact of the support composition on the performance in the water-gas shift reaction by T. Tabakova; M. Manzoli; D. Paneva; F. Boccuzzi; V. Idakiev; I. Mitov (pp. 266-274).

Display Omitted▶ The support composition affects strongly the WGS activity of Au/mixed Ce–Fe oxides. ▶ The WGS activity order was: Au/CeO₂>Au/Ce50Fe50>Au/Ce75Fe25>Au/Ce25Fe75>Au/Fe₂O₃. ▶ Difference in gold particles size and Ce³⁺ defects controlled the performance in the WGSR. ▶ Higher amount of Ce³⁺ sites was registered by FTIR on the surface of Au/CeO₂.Gold catalysts were prepared by deposition-precipitation method on mixed Ce–Fe composite oxides, synthesized by the urea gelation coprecipitation pathway. The impact of the support composition on the catalytic performance for the water-gas shift reaction was studied by varying the Ce/(Ce+Fe) ratio. The following activity order was observed: Au/CeO₂>Au/Ce50Fe50>Au/Ce75Fe25>Au/Ce25Fe75>Au/Fe₂O₃. The differences in the gold particle size (1–25nm) and in the concentration of surface Ce³⁺ defect sites could explain the WGS activity order. The analysis of the HRTEM data combined with a FTIR study suggested the presence of highly dispersed gold clusters on the surface of Au/CeO₂. Additionally, a higher amount of Ce³⁺ sites was registered by FTIR spectroscopy on the surface of this catalyst. Mössbauer spectra collected at room temperature and 90K evidenced that different amounts of cubic CeO₂-like solid solution (CeO₂Fe_SS) and hematite coexisted in CeO₂–Fe₂O₃ supports. The analysis of the characterization data suggested that Fe³⁺ were distributed at Ce⁴⁺ and interstitial sites by a dopant compensation mechanism. This mechanism of solid solution formation accounted for the lower oxygen vacancy concentration and Ce³⁺ amount on all gold catalysts supported on mixed CeO₂–Fe₂O₃ materials, which affected the performance in the WGSR.

Keywords: Gold catalysts; CeO; ₂; –Fe; ₂; O; ₃; Water-gas shift reaction; Hydrogen production; HRTEM; FTIR; Mössbauer spectroscopy

DeNOx performance of Ag/Al₂O₃ catalyst by n-dodecane: Effect of calcination temperature by Dal Young Yoon; Joo-Hyoung Park; Ho-Chul Kang; Pyung Soon Kim; In-Sik Nam; Gwon Koo Yeo; Jeong Ki Kil; Moon-Soon Cha (pp. 275-282).

Display Omitted▶ The higher the catalyst calcination temperature, the higher deNOx activity has been achieved below 300°C. ▶ A larger amount of metallic Ag_n clusters was formed on the catalyst surface as the catalyst calcination temperature increased. ▶ The metallic Ag_n clusters may be also responsible for the high deNOx performance below 300°C as well as the ionic Ag.The effect of the calcination temperature of Ag/Al₂O₃ catalyst on NO removal activity by n-dodecane as a diesel simulant has been examined with respect to the Ag loading and C₁/NO feed ratio under a feed gas condition containing both excess H₂O and oxygen. The higher the catalyst calcination temperature and Ag loading, the higher deNOx activity that has been achieved in the reaction temperature range lower than 300°C. 56% of the NO conversion to N₂ has been attained over Ag(2)-800 catalyst at 300°C when the C₁/NO feed ratio to the reactor is 6. The amount of the metallic Ag formed on the catalyst surface responsible for the high deNOx performance in the temperature region lower than 300°C increases upon the increase of the catalyst calcination temperature from 550 to 800°C and of the Ag loading from 1 to 3wt.%, as determined by UV–vis and XPS. The –NCO species formed on the catalyst surface with acetate, formate and carbonate compounds produced from the partial oxidation of n-dodecane is a critical reaction intermediate for the present reaction system, as identified by in situ IR study. The formation of the –NCO species on the catalyst surface becomes apparent, particularly at 300°C as the catalyst calcination temperature increases.

Keywords: HC–SCR; n; -Dodecane; Ag/Al; ₂; O; ₃; Calcinations temperature; UV–vis; XPS; In situ IR

Operando FTIR study of the photocatalytic oxidation of methylcyclohexane and toluene in air over TiO₂–ZrO₂ thin films: Influence of the aromaticity of the target molecule on deactivation by María D. Hernández-Alonso; Isabel Tejedor-Tejedor; Juan M. Coronado; Marc A. Anderson (pp. 283-293).

Display Omitted▶ Simultaneous analysis of operating photocatalyst and composition of the gas phase. ▶ Methylcyclohexane intermediates do not lead to deactivation of the photocatalysts. ▶ Aromaticity of toluene plays a key role in the deactivation of the photocatalysts. ▶ Accumulation of benzoate species on the photocatalyst surface leads to deactivation.The main objective of the present study is to gain further insight into the mechanism of toluene and methylcyclohexane photocatalytic oxidation on TiO₂–ZrO₂ thin-films, in order to understand the influence of the chemical nature of the pollutants on the deactivation process. Despite the significant differences in the physicochemical characteristics of these two molecules, the parallel study of their photocatalytic degradation can contribute to ascertain relevant aspects of the mineralization mechanism. This knowledge could be used for developing feasible solutions for this deactivation problem, which hinders a wider use of photocatalysis for air purification. The operando study of toluene photooxidation, a simultaneous analysis of surface and gas phase during reaction by using two FTIR spectrometers in tandem, allowed us to correlate the deactivation process with the formation of benzoic acid, strongly adsorbed on the surface as benzoate complexes. These species block the access of new organic molecules to the active sites and simultaneously hinder charge transfer from the photoactivated surface. As a consequence, the degradation rate of toluene considerably decreases after a few minutes of reaction. In contrast, intermediate surface complexes can be almost completely removed during the photocatalytic oxidation of methylcyclohexane. Therefore, it seems that the aromaticity of toluene plays a key role in the performance of photocatalysts during its degradation. The high stability of benzyl radicals favors the photocatalytic oxidation of this volatile organic compound (VOC) and the formation of recalcitrant oxygenated aromatic molecules which accumulate on the photoactive surface.

Keywords: Thin-film; Photocatalysis; Operando; FTIR; Toluene; Methylcyclohexane; TiO; ₂; ZrO; ₂

Hydrotreating of coker light gas oil on Ti-modified HMS supports using Ni/HPMo catalysts by P.E. Boahene; K. Soni; A.K. Dalai; J. Adjaye (pp. 294-305).

Display Omitted▶ Presence of Ti and HPA into the HMS increases the reducibility of catalysts. ▶ Keggin structure was preserved during impregnation of TiHMS and calcination steps. ▶ NiPMo/Ti–HMS catalysts showed better performance in deep HDS and HDN of CLGO.In the present investigation, Ti–HMS materials with variable Si/Ti molar ratios of 20, 40, and 80 were synthesized and employed as supports for Ni-promoted 12-molybdophosphoric acid (NiPMo) catalysts. The effect of the Ti ions and the immobilization of 12-molybdophosphoric acids on mesoporous materials were studied. Supports and catalysts were thoroughly characterized by using XRD, N₂ adsorption analysis, FT-IR, Raman, TPR, DRIFT, SEM and TEM techniques. Results from XRD and IR measurements confirm the hexagonally ordered mesoporous structure and incorporation of Ti into the HMS support, respectively. It was found that incorporation of Ti and presence of HPA into the HMS structure increased the reducibility of the catalysts. Hydrotreating experiments were conducted using coker light gas oil under industrial conditions of temperature, pressure, LHSV, and gas to oil ratio of 330–370°C, 8.8MPa, 1h⁻¹, and 600mL/mL, respectively. It was found that NiPMo catalysts prepared from heteropolyacids showed better performance in HDS and HDN of coker light gas oil (CLGO) than the NiMo catalysts prepared by conventional method using ammonium hepta molybdate (AHM) as Mo source.

Keywords: Ti–HMS; 12-Molybdophosphoric acid; Keggin structure; HDS; HDN; Coker light gas oil

Sewage sludge based catalysts for catalytic wet air oxidation of phenol: Preparation, characterisation and catalytic performance by R.R.N. Marques; F. Stüber; K.M. Smith; A. Fabregat; C. Bengoa; J. Font; A. Fortuny; S. Pullket; G.D. Fowler; N.J.D. Graham (pp. 306-316).

Display Omitted▶ Sewage sludge based activated carbons (SBACs) were produced from two sludges. ▶ The SBACs all exhibited catalytic activity. ▶ The SBACs’ significant Fe content appeared to facilitate their catalytic properties. ▶ The SBACs’ performance strongly correlated with their BET surface area. ▶ The acid washed SBACs’ phenol conversion values were ca. 96% of the commercial AC's.In this study the use of novel CWAO catalysts, namely potentially low cost, sewage sludge derived activated carbons was explored. Two types of municipal sludge were used: dewatered raw filter cake and dewatered mesophilic anaerobically digested sludge. The carbons were produced by: carbonisation; physical activation (steam or CO₂) and chemical activation (K₂CO₃). Hydrochloric acid washing of some of the carbons was also investigated. The carbons were characterised in terms of their surface area, contact pH, propensity towards metal leaching, surface chemistry (via FTIR), ash content and inorganic elemental composition. Their CWAO performance was assessed at 160°C and a partial oxygen pressure of 4.2bar (25bar of air) within a stirred batch reactor containing a 5g/L phenol solution. All the carbons exhibited catalytic activity, with the K₂CO₃ activated and HCl washed carbons attaining a phenol and TOC removal that matched the performance of an activated carbon specifically manufactured for oxidative wastewater treatment applications. A strong correlation was found between surface area and phenol or TOC conversion, suggesting that surface area is a primary requisite for their performance in the first batch cycle. Thus, the oxidation of phenol is thought to proceed via a free radical driven mechanism. The active sites necessary to facilitate this mechanism, whether present as surface functional groups or active metals ( e.g., Fe), were detected on all of the sludge based activated carbons. However, no clear correlation between phenol conversion and these active sites could be established.

Keywords: Catalytic wet air oxidation; Activated carbon; Sewage sludge; Wastewater treatment; Phenol; Batch reactor

Structural characterisation of Ce_0.5Zr_0.5O₂ modified by redox treatments and evaluation for chlorinated VOC oxidation by Beatriz de Rivas; Rubén López-Fonseca; Miguel Ángel Gutiérrez-Ortiz; José I. Gutiérrez-Ortiz (pp. 317-325).

Display Omitted▶ Catalytic activity of Ce_0.5Zr_0.5O₂ is enhanced by redox treatments. ▶ Pyrochlore-type ordering (κ phase) is responsible for this enhanced performance. ▶ Oxygen mobility at low temperatures depends on the extent of cations ordering.In this work the application of a redox treatment consisting of a high-temperature reduction with 5%H₂/Ar in the range 950–1075°C for 0.5–3h followed by mild oxidation at 550°C with 5%O₂/He was evaluated as a tool for improving the catalytic performance of Ce_0.5Zr_0.5O₂ mixed oxide in the combustion of chlorinated compounds. Structural, morphological and physico-chemical changes caused by the redox treatment were analysed by X-ray diffraction, Raman spectroscopy, BET measurements, NH₃-temperature programmed desorption, temperature programmed reduction with hydrogen, and oxygen chemisorption. Interestingly, after reduction at a temperature as high as 1050°C during at least 1.5h, a substantially enhanced redox behaviour was noticed which resulted in a significant promotion of the catalytic activity in comparison with the unmodified parent sample. Hence, the value of temperature of half conversion at 30,000h⁻¹ decreased from 300 to 275°C for the combustion of 1,2-dichloroethane, which was selected as a model chlorinated feed. This active performance was assigned to the formation of a new κ-CeZrO₄ phase after redox aging characterised by a markedly increased capacity of providing active oxygen species at low temperatures. For comparative purposes two additional Ce_0.5Zr_0.5O₂ samples calcined at 750 and 1000°C were also characterised and catalytically tested.

Keywords: Chlorinated VOCs; Catalytic combustion; Ce; _0.5; Zr; _0.5; O; ₂; mixed oxide; Pyrochlores; Redox aging

Promoted CO oxidation activity in the presence and absence of hydrogen over the TiO₂-supported Pt/Co–B bicomponent catalyst by Zhengxin Ding; Haiyan Yang; Junfeng Liu; Wenxin Dai; Xun Chen; Xuxu Wang; Xianzhi Fu (pp. 326-332).

Display Omitted▶ This work is based on the viewpoint that increasing the surface electron density of Pt can promote the oxidation of CO over the bimetallic Pt/Co/TiO₂ catalyst. ▶ An amorphous CoB alloy instead of Co or CoO_x was firstly introduced into Pt/TiO₂ catalyst. The electron donation by B to Co atoms in CoB can keep a high surface electron density of Pt in Pt/Co–B/TiO₂ via inhibiting the electron transfer from Pt to Co atoms. Thus, a higher activity of oxidizing CO and a higher preferential oxidation of CO in the presence of H₂ is obtained. ▶ This work implies that any way to increase the surface electron density of Pt in Pt/Co/TiO₂ (such as electrochemical, photochemical method) maybe also promotes the oxidation of CO over the bimetallic Pt/Co/TiO₂. ▶ This work maybe develops a new approach to prepare a novel catalyst of selectively oxidizing CO for a prospective of purifying H₂ steam in fuel cell systems.A Pt and Co–B bicomponent catalyst supported on TiO₂ (Pt/Co–B/TiO₂) is prepared by a two-step impregnation-reduction method. This Pt/Co–B/TiO₂ catalyst exhibits a higher activity for CO oxidation in the absence of H₂ and for preferential CO oxidation in the presence of H₂, as compared to the Pt/Co bimetallic component catalyst (Pt/Co/TiO₂) prepared by H₂ reduction. Based on the results of the X-ray photoelectron spectroscopy analysis, the CO adsorption over different catalysts and the density functional computation of Co–B, it is proposed that the electron transfer from B to Co atoms in Co–B with an amorphous structure may be responsible for the promoted oxidation of CO over Pt/Co–B/TiO₂. This electron transfer can keep a high surface electron density of Pt in Pt/Co–B/TiO₂ via inhibiting the electron transfer from Pt to Co atoms, which is favorable for the activation of CO species adsorbed at Pt surface.

Keywords: Oxidation of carbon monoxide; Platinum cobalt bicomponent catalyst; Cobalt boron compound; Electron transfer

Surface doping is more beneficial than bulk doping to the photocatalytic activity of vanadium-doped TiO₂ by Sue-min Chang; Wei-szu Liu (pp. 333-342).

Display Omitted▶ Uneven doping of V ions in the surface lattice improves the photocatalytic activities of micrometer-sized TiO₂. ▶ Bulk doping has detrimental effects on the photocatalytic activities except for a slight improvement happening at trace doping amounts. ▶ Deep trapping of charge carries at inner defects results in severe annihilation which reduces substantial quantities of effective charges for surface photocatalytic reactions. ▶ Surface defects retard recombination and facilitate interfacial charge transfer to enhance photocatalytic activity.In this study, we examined the effects of surface and bulk doping on the photocatalytic activity of vanadium (V)-doped TiO₂ on the basis of charge trapping, separation, and interfacial transfer. Moreover, we characterized the microstructures and electronic structures of the two types of doped TiO₂ and the chemical states of the doped V ions to elucidate the causes of the different physicochemical properties. The photocatalytic activity of the doped TiO₂ was enhanced by 1.9 times when the V ions were doped only in the surface lattice at a surface V/Ti molar ratio of 3.0×10⁻¹, in contrast, bulk doping caused detrimental effects. Reduced species, including V³⁺ and V⁴⁺ ions, were formed in the interstitial anatase lattice. These impurities introduced occupied and unoccupied energy levels, which were close to and in the conduction band of TiO₂, respectively. The V³⁺/V⁴⁺ ions within the TiO₂ lattice inhibited charge diffusion to the surface through deep trapping. In contrast, the impurities present only in the surface lattice increased the number of surface trapped holes and facilitated the interfacial charge transfer from the photoactivated TiO₂ to adsorbates. Heavy doping at the surface resulted in the formation of V₂O₅. The p–n junction between the TiO₂ and V₂O₅ separated charge carriers and additionally promoted the photocatalytic activity of the surface-doped TiO₂.

Keywords: Surface- and bulk-doping; V-doped TiO; ₂; Charge trapping; p–n junctions; Photocatalytic activity

Chloralkanes as chlorinating agents: An efficient approach to acyl chlorides and destruction of chlorinated hydrocarbons by Changhu Chu; Renhua Liu (pp. 343-347).

Display Omitted▶ A novel approach to preparation of acyl chlorides. ▶ The exploitation of CCl₄ as a chlorine resource for chlorination of organic acids. ▶ An interesting method to dispose low value CCl₄.Carbon tetrachloride, a low value and banned compound, was utilized to chlorinate organic acids in the presence of catalytic amount of FeCl₃. A wide range of organic acids were smoothly transferred to corresponding acyl chlorides, while the carbon tetrachloride itself was consumed. Further more, some substituted benzoic acids which are not easy to be chlorinated by normal chlorination reagents are efficiently transferred to acyl chlorides by this chlorination method.

Keywords: Carbon tetrachloride; Ferric chloride; Chlorination; Acyl chloride

Partial oxidation of n-hexadecane into synthesis gas over a Pd-based metal monolith catalyst for an auxiliary power unit (APU) system of SOFC by HakJoo Kim; JungIl Yang; Heon Jung (pp. 348-354).

Display Omitted▶ Fast start-up accomplished with a novel fuel injection and vaporization system. ▶ Partial oxidation on Pd catalyst proceeds via two-stage redox mechanism. ▶ Triply promoted Pd catalyst shows enhanced instant re-oxidation ability. ▶ Triply promoted Pd catalyst shows higher synthesis gas productivity.The developed diesel fuel reformer presented in this study consists of three components: a fuel injection part working with an air-blown nozzle; a fuel vaporizing part; catalytic converting part. The injected diesel fuel was vaporized on the surface of the electrically heated cylindrical metallic monolith cell (EHC; electrically heated cell). With our injection and vaporization systems, fast start-ups within 4min were accomplished at low energy consumption in the stand-alone mode; this proved practicable for transportation applications. The palladium-based catalyst was prepared by the dip coating method. All SEM, TEM, and XPS analyses showed that an intensive and uniform catalyst layer was formed on the metallic monolith surface, composed of palladium oxide crystallite impregnated on alumina support. The catalytic partial oxidation of n-hexadecane was carried out by varying the C/O ratio and steam/C ratio within the GHSV in the range of 30,000–100,000h⁻¹. Both TPO and XPS analyses were performed for tracing the reaction mechanism of the partial oxidation of n-hexadecane into synthesis gas under the palladium-based catalyst. Partial oxidation over the palladium catalyst was proposed to proceed via the Mars & van Krevelen two-stage redox mechanism. Addition of CeO₂, BaO, and SrO promoters to the Pd/Al₂O₃ catalyst improved thermal stability, as well as the ability of instant re-oxidation of metallic Pd to PdO during the redox cycles, which gave rise to an increase in catalytic activity for higher synthesis gas productivity of higher H₂/CO ratios and lower CO₂ selectivity.

Keywords: Diesel reformer; Catalytic partial oxidation; Synthesis gas production; Pd catalyst; Redox mechanism

Modified textures and redox activities in Pt/Al₂O₃+BaO/Ce_xZr1−_xO₂ model NSR catalysts by Chao Lei; Meiqing Shen; Ming Yang; Jun Wang; Jie Wang (pp. 355-365).

.Display Omitted▶ The BaO/Ce_xZr1−_xO₂ and Pt/Al₂O₃ mixtures were investigated as NSR catalysts. ▶ Higher Ce content favors rapid NO_x up-taking and stable adsorption. ▶ Higher Zr content brings the risk of BaZrO₃ formation during the ageing. ▶ The catalyst with strong redox activity limits the NH₃ release.The present work investigates the catalytic performances of 20wt.% Ba supported Ce_xZr1−_xO₂ ( x=0, 0.3, 0.5, 0.7, 1) NO_x storage catalysts, where 2wt.% Pt/Al₂O₃ part was blended in as physical mixtures. The interests were focused on the effects of Ce–Zr compositions as support oxides to barium species in NO_x storage and release cycles. Higher Ce content favors rapid NO_x up-taking and stable adsorption in adequate amount of small BaCO₃ particles. The increasing amount of Zr in Ce_xZr1−_xO₂ may benefit the formation of porous texture, but it brings the higher risk of BaZrO₃ formation during the ageing. It not only consumes active Ba sites for NO_x storage, but induces even severe sintering to these materials. Additionally, the introduced ZrO₂ may increase oxygen mobility to improve redox activities of the catalysts. This improvement could lower the NH₃ release in rich period. However, to another extreme, a too strong oxidative activity is going to inhibit the NO_x reduction due to its stabilization to intermediate NO₂ δ⁺ species.

Keywords: NO; _x; storage reduction; Support oxides; Ceria–zirconia; Barium carbonate; Barium zirconate; Ageing; Redox activity

Highly active and stable PtRuSn/C catalyst for electrooxidations of ethylene glycol and glycerol by Hyung Ju Kim; Sung Mook Choi; Sara Green; Geoffrey A. Tompsett; Seon Hwa Lee; George W. Huber; Won Bae Kim (pp. 366-375).

Display Omitted▶ The PtRuSn/C enhanced the catalytic activities for EG and Gly electrooxidations. ▶ Efficient oxidative removals of CO or CO-like species were also possible. ▶ Thus, high catalytic activity and stability over the PtRuSn/C could be achieved.Electrocatalytic oxidations of ethylene glycol and glycerol were studied over a carbon-supported PtRuSn catalyst (PtRuSn/C), which was prepared with a Pt:Ru:Sn atomic ratio of 5:4:1 using a colloidal method combined with a freeze-drying procedure at room temperature. The ternary PtRuSn/C catalyst was characterized by various physicochemical analyses such as X-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS), thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS) and X-ray absorption-near-edge spectroscopy (XANES). The ternary PtRuSn catalyst showed noticeable modifications on the catalyst phases from Pt or PtRu in regards to structural and electronic features, such as a change in lattice parameter and electronic modification in unfilled d band states of Pt atoms. The structurally and electronically modified PtRuSn/C catalysts substantially enhanced the electrocatalytic activities for ethylene glycol and glycerol oxidations, resulting in larger peak currents and lower onset potentials of the electrooxidations. By incorporating the Ru and Sn elements onto the ternary PtRuSn/C catalyst, efficient oxidative removals of CO or CO-like carbonaceous intermediate species produced during the reaction were also possible, thus preventing poisoning of the active Pt sites. Consequently, significant enhancements of electrocatalytic activity and stability over the ternary PtRuSn/C catalyst could be achieved for the electrooxidations of ethylene glycol and glycerol.

Keywords: PtRuSn catalyst; Electrocatalytic oxidations; Ethylene glycol; Glycerol; Fuel cells

Improving the thermal stability and photocatalytic activity of nanosized titanium dioxide via La³⁺ and N co-doping by Ye Cong; Baozhu Tian; Jinlong Zhang (pp. 376-381).

Display Omitted▶ Nitrogen and La³⁺ doping inhibits the phase transformation of TiO₂. ▶ Nitrogen and La³⁺ doping inhibits crystallite growth of TiO₂. ▶ Nitrogen and La³⁺ doping enhances the thermal stability of TiO₂ structure. ▶ Nitrogen/La³⁺ co-doped TiO₂ shows the highest photocatalytic activity.The microstructure and properties of nitrogen and lanthanum co-doped nanocrystalline titania photocatalysts have been studied. The catalyst samples were prepared in a homogeneous precipitation–hydrothermal process and characterized by XRD, XPS, UV–DRS and BET analyses. The results indicated that the nitrogen and La³⁺ doping could inhibit the phase transformation and crystallite growth of TiO₂ and enhance the thermal stability of TiO₂ structure. In addition, the experiment results showed that the thermal stability of TiO₂ increased with the increasing of La³⁺ doping. The photocatalytic activities of samples for photodegradation of rhodamine B under visible light irradiation using different La³⁺ doping contents were also studied. There were optimal values of La³⁺ doping content for the La³⁺ doped and nitrogen/La³⁺ co-doped TiO₂ corresponding the highest photodegradation percentages. The nitrogen and La³⁺ co-doped titania could greatly improve the photocatalytic activity in visible light irradiation, whose probable mechanism is a synergistic effect of co-doping. The nitrogen doping could narrow the band gap of titania and enhance the utilization efficiency of visible light, while the La³⁺ doping could accelerate the separation of photo-generated electrons and holes. Furthermore, the La³⁺ doping could increase the adsorption of organic pollutants on the surface of photocatalyst.

Keywords: Lanthanum; Nitrogen; Co-doping; Phase transformation; Photocatalytic activity

Significantly enhanced photocatalytic performance of ZnO via graphene hybridization and the mechanism study by Tongguang Xu; Liwu Zhang; Hanyun Cheng; Yongfa Zhu (pp. 382-387).

Display Omitted▶ ZnO is surface modified with graphene. ▶ The photocatalytic activity of ZnO is greatly increased by more than 3 times. ▶ The optimum loading amount of graphene is 2.0wt%. ▶ The electronic interaction retards the recombination of photo-induced charges.Graphene hybridized with ZnO could produce an efficient photocatalyst. The ZnO nanoparticles were firstly coated with an appropriate amount of graphene oxide, the graphene oxide was then in situ reduced to form the ZnO/graphene composite. Graphene hybridized ZnO photocatalyst showed enhanced photocatalytic activity for the degradation of organic dye. The degree of photocatalytic activity enhancement strongly depended on the coverage of graphene on the surface of ZnO nanoparticles. The sample of 2wt% graphene hybridized ZnO showed the highest photocatalytic activity, which was about 4 times as that of pristine ZnO. The enhancement of photocatalytic activity was attributed to the high migration efficiency of photo-induced electrons and the inhibited charge carriers recombination due to the electronic interaction between ZnO and graphene. The electronic interaction was systematically studied and confirmed by the photoelectrochemical measurements.

Keywords: Graphene; Photocatalysis; ZnO; Photoelectrochemical

The effect of gold addition on the catalytic performance of copper manganese oxide catalysts for the total oxidation of propane by Benjamin Solsona; Tomas Garcia; Said Agouram; Graham J. Hutchings; Stuart H. Taylor (pp. 388-396).

Display Omitted▶ Hopcalite catalysts containing gold have been prepared by coprecipitation. ▶ Gold-containing Hopcalite demonstrates high and stable activity for propane total oxidation. ▶ Hopcalite-based catalysts show higher activity than supported palladium catalysts.Mixed copper manganese oxide catalysts (Hopcalite) have been studied for the total oxidation of propane, as a model for hydrocarbon volatile organic compound emission control. Catalysts were prepared using coprecipitation with and without gold. Calcination temperature influenced the catalyst activity and those prepared at 300°C were the most active. Characterization showed that the catalysts had a nanowire-type morphology, and for those containing gold it was present as metallic particles occluded within the nanowires. The incorporation of gold into the catalyst enhanced the activity for propane conversion, but the presence of gold did not noticeably enhance the light-off activity. Although the addition of gold enhanced the propane total oxidation activity, the amount of gold incorporated did not greatly influence the catalytic activity. Significantly the Hopcalite-based catalysts, particularly those containing gold, showed total propane oxidation activity far greater than palladium-based catalysts. The improved activity on the incorporation of gold into Hopcalite is related to the reducibility of the catalysts, which is increased by gold addition. The gold-containing catalyst demonstrated stable activity through cycling and with time-on-line and it exhibited increased stability over the equivalent Hopcalite catalyst.

Keywords: VOCs; CO; Catalytic oxidation; Gold; Copper manganese oxides

Hydrogen production through alcohol steam reforming on Cu/ZnO-based catalysts by Barbara Lorenzut; Tiziano Montini; Loredana De Rogatis; Patrizia Canton; Alvise Benedetti; Paolo Fornasiero (pp. 397-408).

Display Omitted▶ Cu/ZnO/Al₂O₃ is highly active in methanol steam reforming. ▶ Cu/ZnO/Al₂O₃ shows poor H₂ selectivity in the ethanol steam reforming. ▶ Addition of Ni or Co to Cu/ZnO/Al₂O₃ significantly improves ethanol reforming reaction. ▶ Formation of an alloy between Ni and Cu reduces carbon deposition during ethanol steam reforming.Hydrogen production by steam reforming of methanol and ethanol is studied over a series of Cu/ZnO/Al₂O₃ catalysts prepared by different coprecipitation procedures and modified with the introduction of Ni and Co. The catalysts are characterized using N₂ physisorption, X-ray diffraction (XRD), temperature programmed reduction (TPR) techniques, N₂O decomposition, high resolution transmission electron microscopy (HR-TEM) and thermogravimetric analysis (TGA). Despite the influence of the preparation method on the texture and structure of Cu/ZnO/Al₂O₃ catalysts, their catalytic behavior appears not significantly affected. While Cu/ZnO/Al₂O₃ shows poor H₂ selectivity in the ethanol steam reforming reaction, the presence of a second metal (Ni or Co) significantly improves the reforming reaction. Although coke deposition remains a drawback for these systems, formation of an alloy between Ni and Cu appreciably reduces carbon deposition with respect to the Co/Cu-based system.

Keywords: Ethanol reforming; Hydrogen production; Cu/Zn/Al; ₂; O; ₃; based catalysts

High-temperature steam reforming of methanol over ZnO–Al₂O₃ catalysts by Mei Yang; Shulian Li; Guangwen Chen (pp. 409-416).

Display Omitted▶ ZnO–Al₂O₃ is an efficient catalyst for high-temperature steam reforming of methanol. ▶ The catalyst is inexpensive and environmental benign. ▶ No deactivation of ZnO–Al₂O₃ with ZnO/(ZnO+Al₂O₃) molar ratio of 0.50 is observed during the 200h continuous operation. ▶ The octahedral Zn²⁺ ions in Zn-rich non-stoichiometric ZnAl₂O₄ favor the formation of CO. ▶ Reverse water gas shift and methanol decomposition reactions are involved in the formation of CO.In this study, a series of ZnO–Al₂O₃ catalysts with various ZnO/(ZnO+Al₂O₃) molar ratios have been evaluated for the high-temperature steam reforming of methanol, and the optimizing catalyst composition consists in the range of 0.50–0.67. The catalysts were characterized by N₂ adsorption–desorption, X-ray diffraction and UV–vis spectra. In the case of ZnO/(ZnO+Al₂O₃)>0.5, a significant proportion of Zn could dissolve in ZnAl₂O₄, resulting in Zn-rich non-stoichiometric spinel, in which the Zn²⁺ ions located both at the tetrahedral and octahedral sites. It was noticed that such a coordination of Zn²⁺ ions in the octahedral position brought about a higher CO selectivity. Further investigation illuminated water gas shift and methanol decomposition reaction were both involved in the formation of CO. There was no noticeable deactivation for ZnO–Al₂O₃ with the ZnO/(ZnO+Al₂O₃) molar ratio of 0.50 during the 200h continuous operation (GHSV=17930h⁻¹, T=420°C). The H₂ space time yield is 55Lh⁻¹g_cat⁻¹ and the concentration of CO in the dry gaseous products was lower than 0.8%.

Keywords: Methanol steam reforming; Microreactor; Hydrogen; ZnO–Al; ₂; O; ₃; CO formation

Mechanism of catalytic degradation of 2,4,6-trichlorophenol by a Fe-porphyrin catalyst by Konstantinos C. Christoforidis; Eleni Serestatidou; Maria Louloudi; Ioannis K. Konstantinou; Elena R. Milaeva; Yiannis Deligiannakis (pp. 417-424).

Display Omitted▶ Efficient catalytic oxidation of TCP was achieved by a Fe-porphyrin catalyst. ▶ Initial oxidation products were DCQ and Cl ions. ▶ Final oxidation products were five chlorinated dimmers produced via radical polymerization. ▶ Homogeneous [FeR₄P] is more efficient vs. the heterogenized (FeR₄P–SiO₄) catalyst. ▶ A complete catalytic mechanism is proposed.The catalytic oxidation of 2,4,6-trichlorophenol (TCP) by a homogeneous Fe-porphyrin catalyst (FeR₄P) and the corresponding heterogeneous one (immobilized on silica, FeR₄P–SiO₂) was studied by analytical and EPR spectroscopic methods. The homogeneous catalyst was found to be more efficient for oxidative decomposition and dechlorination of TCP, compared to the heterogeneous FeR₄P–SiO₂ catalyst. The main, initial and final, oxidation products were identified and a general catalytic mechanism was proposed concerning TCP oxidation and the by-products formation, in relation with the catalyst's redox cycle.

Keywords: Chlorophenol; TCP; DCQ; Radical; EPR; LC–MS; Oxidation products; Dehalogenation; Heme catalyst; Heterogeneous catalyst; Catalytic mechanism

Heterogeneous and homogeneous Fenton processes using activated carbon for the removal of the herbicide amitrole from water by M.A. Fontecha-Cámara; M.A. Álvarez-Merino; F. Carrasco-Marín; M.V. López-Ramón; C. Moreno-Castilla (pp. 425-430).

Display Omitted▶ Homogeneous Fenton activity without activated carbon was lower than heterogeneous one. ▶ Iron leaching with heterogeneous Fenton catalysts was very low. ▶ Highest AMT degradation was with homogeneous FeSO₄ in presence of activated carbon. ▶ Activated carbon and FeSO₄ showed a synergic effect on hydroxyl generation from H₂O₂.The study objective was to investigate the removal of amitrole (AMT) by oxidation using the decomposition of hydrogen peroxide in heterogeneous and homogeneous Fenton reactions. For this purpose, an activated carbon cloth was used to prepare supported iron catalysts with different iron salts (sulfate, acetate and nitrate) and iron metal loadings. Homogeneous Fenton reactions were carried out by using iron sulfate or acetate in the absence or presence of the activated carbon cloth. In the heterogeneous Fenton reaction, the amounts of TOC (total organic carbon) and AMT removed depended on the iron metal loading and the Fe/H₂O₂ molar ratio; iron leaching was very low. The highest AMT degradation (∼90%) was achieved with the homogeneous Fenton reaction using FeSO₄ in the presence of the activated carbon cloth, which may be due to a synergic effect between activated carbon and iron salt; with this procedure, ∼60% of the TOC was removed. The synergic effect was not observed when iron acetate was used as homogeneous catalyst. The presence of sulfate ions favored the oxidation of AMT to urazole. Nitrate and ammonium ions were observed but at negligible concentrations.

Keywords: Amitrole oxidation; Fenton processes; Activated carbon cloth; Carbon–Fe catalysts

Hydrogenolysis of glycerol over homogenously dispersed copper on solid base catalysts by Zhenle Yuan; Lina Wang; Junhua Wang; Shuixin Xia; Ping Chen; Zhaoyin Hou; Xiaoming Zheng (pp. 431-440).

Display Omitted▶ Homogenously dispersed copper on layered solid base catalyst was synthesized. ▶ The dispersion of Cu was characterized by TEM, N₂O adsorption and in-situ XRD. ▶ This catalyst is extremely effective for hydrogenolysis of glycerol at 180°C. ▶ The conversion of glycerol depends strongly on the particle size of copper. ▶ Solid base can suppress the cleavage of C–C bond in glycerol.Homogenously dispersed copper on layered solid base (Cu_0.4/Mg_5.6Al₂O_8.6-CP, with 80.1% dispersion of copper) was synthesized via thermal decomposition of the as-synthesized Cu_0.4Mg_5.6Al₂(OH)₁₆CO₃ layered double hydroxides. This bi-functional highly dispersed Cu-solid base catalyst is extremely effective for hydrogenolysis of aqueous glycerol. The detected conversion of glycerol reached 80.0% with a 98.2% selectivity of 1,2-propanediol at 180°C, 3.0MPa H₂ and 20h. But copper dispersed poorly in those catalysts prepared via impregnation and ion-exchange, and their activities were lower. These precursors and catalysts were characterized by N₂-adsorption, X-ray diffraction, scanning electronic microscope, transmission electronic microscope, thermo-gravimetry, temperature-programmed reduction with H₂, in-situ XRD, dissociative N₂O adsorption and CO₂ temperature-programmed desorption. It was confirmed that the as-synthesized Cu_0.4Mg_5.6Al₂(OH)₁₆CO₃ showed a well crystallized layer-structure of hydrotalcite and copper dispersed homogenously on the layer-structure of hydrotalcite after thermal decomposition and H₂ reduction.

Keywords: Biodiesel; Glycerol; Hydrogenolysis; Cu-solid base; 1,2-Propanediol

Studies of N-demethylation oxidative and degradation of methylene blue by thin layers of birnessite electrodeposited onto SnO₂ by M. Zaied; S. Peulon; N. Bellakhal; B. Desmazières; A. Chaussé (pp. 441-450).

Display Omitted▶ Interest of using thin layer for understanding mechanism at solid–liquid interfaces. ▶ Study of spontaneous reactivity of birnessite towards phenothiazine dyes. ▶ Rapid degradation without supply energy. ▶ Increasing of mineralisation with interaction duration. ▶ Highlighting of the good spontaneous reactivity of a non-toxic material.This paper describes the successful use of thin layers of birnessite to degrade methylene blue (MB) contained in aqueous solutions. This dye is a representative of a class of dyestuffs resistant to biodegradation. The thin layers of birnessite, electrodeposited onto a cheap transparent semiconductor substrate (SnO₂), in neutral aerated sulphate solutions at room temperature, are very homogeneous, adherent and well crystallised. We showed that these thin layers can discolor the MB solutions totally at room temperature after only 2h. Total organic carbon (TOC) analyses report the absence of organic compounds in solutions after treatment, in the best conditions. Mass spectrometry reveals the presence of intermediate reaction products (azure A, azure B, azure C, and thionin) during interaction confirming the real degradation of dye. Nitrate and ammonium ions were quantified showing that thin layer of birnessite can mineralise MB. To understand mechanism, interaction experiments were made with each intermediary compound. The electron transfers lead to a rapid N-demethylation oxidative reaction to form colored intermediary compounds. In all cases, thionin was identified as the last adsorbed organic compound onto the birnessite external surface, which is then mineralised slowly into nitrate and ammonium ions. These results suggest that birnessite thin layers may be envisaged as a new non-toxic material for treatment of diluted colored wastewater.

Keywords: Layered manganese oxide; Mn; ₇; O; ₁₃; Phenothiazine dyes; Mass spectroscopy; Mineralisation

Catalytic wet hydrogen peroxide oxidation of para-chlorophenol over Al/Fe pillared clays (AlFePILCs) prepared from different host clays by Cezar Catrinescu; Daniela Arsene; Carmen Teodosiu (pp. 451-460).

Display Omitted▶ The nature of the host clay influences the structural, textural and catalytic properties on the mixed Al-Fe pillared clays. ▶ The oxidation of 4-chlorophenol proceeds with the formation of 4-chlorocatechol (main intermediate), hydroquinone and other chlorinated benzenediols and triols. ▶ Diffuse-reflectance UV–vis spectroscopy can be used to investigate the solid iron speciation in mixed Al-Fe pillared clays. ▶ The low-nuclearity ferric oxides seem to be responsible for the iron leaching and for the differences in the catalytic activity.In this work, three AlFePILCs prepared from different host clays were synthesized, characterized and tested in the catalytic wet hydrogen peroxide oxidation of 4-chlorophenol. Two reference clays, with widely different cation exchange capacities (1.2meq/g for SAz-1 and 0.87meq/g for SWy-2), and a Romanian montmorillonite (Mt) were used for the preparation of the catalysts, their structural and textural properties being determined by X-ray diffraction and nitrogen adsorption-desorption isotherms. The catalyst based on SAz-1 has a more ordered structure and a higher surface area than the other two catalysts, prepared from SWy-2 and Mt, and this was attributed to its higher layer charge. The 4-chlorophenol oxidation proceeds with the formation of 4-chlorocatechol (main reaction intermediate) and hydroquinone. Other chlorinated benzenediols and triols as well as dimerization products have been also identified by derivatization and GC–MS analysis. All the catalysts allowed the total elimination of 4-chlorophenol and significant removal efficiencies for the total organic carbon, of 60, 52 and 45%, for Mt, SWy-2 and SAz-1 based catalysts, respectively. The iron leaching was very low, but the most active catalyst produced the higher amount of dissolved iron (1ppm), as compared with AlFePILCs based on SWy-2 and SAz-1 (0.5ppm). To explain the differences in the catalytic properties, Mössbauer and diffuse-reflectance UV–vis spectroscopies were used to investigate the nature of the active sites. Both methods suggested the presence of two iron species: low-nuclearity ferric oxides and well-ordered hematite-like nanoparticles. The low-nuclearity ferric oxides seem to be responsible for the iron leaching and for the differences in the catalytic activity.

Keywords: 4-Chlorophenol; Hydrogen peroxide; Oxidation; Fe-containing pillared clay

The influence of rapid heat treatment in still air on the photocatalytic activity of titania photocatalysts for phenol and monuron degradation by Zs. Pap; V. Danciu; Zs. Cegléd; Á. Kukovecz; A. Oszkó; A. Dombi; K. Mogyorósi (pp. 461-470).

Display Omitted▶ Rapid heat treatment results in high activity photocatalysts. ▶ Hydrophilic samples perform better than the aggregating ones. ▶ Ten minutes of calcination provides efficient phenol and monuron degradation. ▶ Reaction rate is higher by a factor of 2 compared to traditionally treated samples. ▶ Best specific reaction rates are significantly higher than that of Aeroxide P25.Titanium dioxide photocatalysts were prepared by a new synthesis method that involves rapid heating with short and medium exposures of the sol–gel prepared amorphous starting materials at different temperatures and calcination times (RHSE and RHME series). Samples were also synthesized using conventional calcination methods (applying slow heating and long exposure times, SHLE series). Both sets of samples were characterized by various methods, such as TG-DTA, XRD, SEM, TEM, DRS, FT-IR, TOC and XPS techniques and by sedimentation experiments. The RHSE and RHME samples have good crystallinity and consist of anatase and rutile mixtures. The photocatalytic activity of catalysts was studied in suspensions using phenol and monuron as model substrates. The best UV performance was found for the RHME sample prepared at 600°C with 60min of exposure. This sample has high UV activity and is comparable to Aeroxide P25 TiO₂ reference photocatalyst for both substrates. The RHSE and RHME samples significantly exceeded the performance of SHLE samples. The loss of surface OH groups during long time calcination was assumed to have a negative effect on the activity of SHLE samples due to a high degree of aggregation of the particles in aqueous solutions. The improved photocatalytic performance is attributed to the higher level of absorption of light in the near-UV range. This new more economic treatment strategy could have major impact on materials engineering of UV and VIS active photocatalysts prepared via sol–gel methods, especially using acetic acid and aqueous solution of ammonia.

Keywords: Titania; Anatase; Rutile; Nanoparticles; Phenol; Monuron; Photocatalysis; Sol–gel method; Rapid crystallization; UV irradiation

Photocatalytic decomposition ofl-phenylalanine over TiO₂: Identification of intermediates and the mechanism of photodegradation by Erzsébet Szabó-Bárdos; Katalin Somogyi; Norbert Törő; Gyula Kiss; Attila Horváth (pp. 471-478).

Display Omitted▶ UV-A excitation of TiO₂ particles induces concerted electron transfers. ▶ Electron transfers lead to the release of NH₃ and CO₂. ▶ Anaerobic photocatalytic performance results in hydroxylation of aromatic ring. ▶ Hydroxylated intermediates are identified. ▶ Aromatic ring opening occurs in aerobic conditions.The purpose of this study was to get a better understanding on the key reaction steps of photocatalytic decomposition ofl-phenylalanine. Therefore the reactions ofl-phenylalanine occurring over UV excited TiO₂ particles were investigated under anaerobic and aerobic conditions. Silver ions were used as electron traps and H₂O₂ molecules were applied as species reacting with conduction band electrons and valence band holes in argon-saturated aqueous suspensions. The photocatalytic performances were followed by measuring the concentration ofl-phenylalanine, the formation of NH₄⁺ and the total organic carbon (TOC) content of the reaction mixtures. In addition, UV–vis absorption and luminescence spectra and the pH of the aqueous phase of suspensions were also monitored. The initial rate of the NH₄⁺ formation was found to be the same in the argon saturated(v0,Ar=(9.1±0.4)×10−7Mmin−1) and in the air saturated(v0,air=(9.3±0.4)×10−7Mmin−1) reaction mixtures, while significantly different values were obtained for the rate of disappearance of the phenylalanine(v0,Ar=18.5×10−7Mmin−1andv0,air=65×10−7Mmin−1) and for the rate of TOC decrease(v0,Ar=17.5×10−7M min−1andv0,air=142×10−7Mmin−1) in anaerobic and aerobic condition, respectively. Among the key intermediates of the photocatalytic decomposition thel-4-hydroxyphenylalanine (l-tyrosine) and thel-3,4-dihydroxyphenylalanine (l-DOPA) were identified by HPLC–MS method. Moreover, other hydroxyphenylalanines (3-hydroxyphenylalanine and 2-hydroxyphenylalanine) and dihydroxyphenylalanine isomers were also assigned by this technique. Ring opening reaction has been observed in conditions where oxygen containing reactive species, such as O₂⁻, HO₂ and singlet oxygen form and can attack the dihydroxyphenylalanines. Mechanisms for the photocatalytic degradation of phenylalanine in anaerobic and aerobic conditions have been proposed.

Keywords: TiO; ₂; photocatalysis; l; -Phenylalanine; Intermediates; Scavengers; Mechanism

Wet oxidation of benzoic acid catalyzed by cupric ions: Key parameters affecting induction period and conversion by Theodora Velegraki; Ekaterini Nouli; Athanasia Katsoni; Ioannis V. Yentekakis; Dionissios Mantzavinos (pp. 479-485).

Display Omitted▶ An induction period occurs implying organic radical mechanisms. ▶ The statistical analysis points to the reaction temperature being the most decisive factor of catalytic wet oxidation. ▶ Oxygen partial pressure, initial substrate concentration and their interaction may also influence induction period. ▶ Oxidation proceeds through the hydroxylation of the aromatic ring.The catalytic wet oxidation (CWO) of aqueous solutions of benzoic acid (BA) has been thoroughly investigated using various copper- and iron-containing catalysts with emphasis on cupric nitrate. The influence of BA concentration ranging from 50 to 150mg/L, catalyst loading varying between 50 and 150mg/L (i.e. 14 and 40mgCu/L), reaction temperature in the range 150–180°C and oxygen partial pressure in the range 10–30bar on the induction period of the reaction and BA conversion has been extensively studied. A factorial experimental design methodology has been implemented to assess the significance of the aforementioned parameters and a mathematical model has been proposed. The induction period observed during the CWO of BA is strongly affected by the reaction temperature and to a lesser extent by the initial BA concentration, the oxygen partial pressure, as well as by the second order interaction between initial BA concentration and oxygen partial pressure. Differences in chemical structure account for different reactivities: electron-donating substituents (i.e. methoxy- or hydroxyl-group) seem to increase the reactivity of benzoic acid, whereas the presence of electron-withdrawing substituents, such as nitro-group, decreases the reactivity of the molecule. Hydroxylation of the aromatic ring is an important pathway during the CWO of BA.

Keywords: Advanced oxidation processes; Benzoic acid; Catalytic wet oxidation; Induction period; Cupric ions; Experimental design

Effect of lean/rich high temperature aging on NO oxidation and NO_x storage/release of a fully formulated lean NO_x trap by Nathan A. Ottinger; Todd J. Toops; Ke Nguyen; Bruce G. Bunting; Jane Howe (pp. 486-494).

Display Omitted▶ Thermal aging of commercial-intent lean NO_x traps combined with extensive materials characterization. ▶ NO oxidation to NO₂ shown to increase with increasing precious metal sintering; although overall NO_x conversion decreases. ▶ Ba phase shown to lose crystallinity either forming an amorphous phase or dispersing over the alumina support when aging above 900°C. ▶ Nitrate stability shown to increase with aging; impacts product selectivity and N₂ to NH₃ ratios.Commercial-intent lean NO_x traps (LNTs) containing Pt, Pd, Rh, Ba, Ce, Zr, and other proprietary additives were thermally aged at 750, 880, 930, and 1070°C using lean/rich cycling and then investigated for effects of aging on NO_x storage capacity, NO oxidation, NO_x reduction, and materials properties. Additionally, DRIFTS analysis was used to determine the effects of high temperature aging on surface chemistry and NO_x storage. As platinum group metal (PGM) dispersion decreases with aging, the NO turnover frequency (TOF) for NO oxidation at 200, 300, and 400°C is shown to increase. The fraction of stored NO_x that is successfully reduced also increases with aging, and it is suggested that this is accounted for by a slower release of more stable NO_x species resulting from thermal aging. NO_x storage and NO_x release experiments performed with DRIFTS at 200, 300, and 400°C indicate that a substantial amount of NO_x is stored on Al₂O₃ as nitrates at 200 and 300°C before aging. However, almost no nitrates are seen on alumina after aging at 900 and 1000°C, resulting in a significant reduction in NO_x storage capacity. This is most likely due to a 45% reduction in total surface area and a high temperature redispersion of Ba over remaining alumina sites. No evidence of BaAl₂O₄ was observed with XRD.

Keywords: DRIFTS; Lean NO; _x; trap; Thermal aging; Fully formulated; PGM dispersion; NO; _x; storage capacity; NO; _x; release; STEM; XRD

Esterification of oleic acid over solid acid catalysts prepared from Amazon flint kaolin by Luís Adriano S. do Nascimento; Laura M.Z. Tito; Rômulo S. Angélica; Carlos E.F. da Costa; José R. Zamian; Geraldo N. da Rocha Filho (pp. 495-503).

Display Omitted▶ The best catalyst (MF9S4) was prepared at 950°C, using after H₂SO₄ 4M. ▶ MF9S4 presented the higher values of acidity and surface area. ▶ MF9S4 reached 98.9% of conversion of oleic acid at 160°C. ▶ Esterification of oil palm/oleic acid mixture reached 84.8% of conversion over MF9S4. ▶ MF9S4 is a new eco-friendly catalyst for the esterification.The esterification of free fatty acids (FFA) can be used to produce biodiesel from high FFA oils. In this work, a new eco-friendly catalyst for the esterification of oleic acid with methanol has been prepared from a waste material, Amazon flint kaolin, that was thermally treated (at 850 and 950°C) and activated with sulfuric acid solutions (1M and 4M). The activated metakaolin samples were characterized by X-ray diffraction, scanning electron microscopy, N₂ adsorption–desorption and adsorption studies of pyridine using TG/DTG and FTIR analysis. The leached metakaolin treated at 950°C and activated with 4M sulfuric acid solution showed the highest surface area (406m²/g), the highest number of acid sites (237.7μmol/g) and offered the maximum esterification activity (98.9%) at 160°C, an acid:methanol molar ratio of 1:60 and 4h reaction time. The influences of reaction parameters such as the molar ratio of the reactants, alcohol chain length, temperature and time have also been investigated. Based on the catalytic results, Amazon flint kaolin is found to be a promising raw material for the production of new solid acid catalysts for the esterification of FFAs.

Keywords: Acid activation; Metakaolin; Microporous; Esterification; Oleic acid

Preparation and characterization of monometallic (Au) and bimetallic (Ag/Au) modified-titania photocatalysts activated by visible light by Anna Zielińska-Jurek; Ewa Kowalska; Janusz W. Sobczak; Wojciech Lisowski; Bunsho Ohtani; Adriana Zaleska (pp. 504-514).

Display Omitted▶ A reverse micelles environment promotes formation of Au- and Ag/Au-modified titania photocatalysts active in visible light. ▶ Composites with bimetallic nanoparticles showed higher level of photoactivity than composites with both metals deposited individually. ▶ Enhanced photoactivity is promoted with increase of gold size nanoparticles. ▶ The size of TiO₂ particles introducing into the microemulsion reaction environment determined gold nanoparticles size.The Au-TiO₂ and Ag/Au-TiO₂ nanoparticles have been prepared using a water-in-oil microemulsion system of water/AOT/cyclohexane and water/Triton X-100/cyclohexane. The obtained photocatalysts were subsequently characterized by a BET method, DRS spectroscopy, X-ray photoelectron emission spectroscopy (XPS), scanning transmission electron microscopy (STEM) and X-ray powder diffraction analysis (XRD). For gold-doped titanium (IV) oxide nanoparticles the effect of reducing agent and stabilizer on gold particles size and photocatalytic activity were observed. The effect of crystalline form of TiO₂ and gold nanoparticles size on photocatalytic activity of Au-TiO₂ and Ag/Au-TiO₂ in visible light were also investigated. The photocatalytic activity of noble metals modified-TiO₂ powders under visible light irradiation was estimated by measuring the decomposition rate of phenol in an aqueous solution. The best photocatalytic activity revealed samples with large gold particles (∼90nm) deposited on small titania nanoparticles. It was also found that the bimetallic samples (Ag/Au-TiO₂) showed a higher photodegradation rate in visible region than monometallic photocatalysts.

Keywords: Au nanoparticles; Bimetallic (Ag/Au) nanoparticles; Modified-TiO; ₂

Kinetics of dodecylbenzenesulphonate mineralisation by TiO₂ photocatalysis by Montserrat Sanchez; Maria J. Rivero; Inmaculada Ortiz (pp. 515-521).

Display Omitted▶ The mineralisation kinetic curves presented two different zones with different slopes. ▶ Data in the two zones fitted to second order kinetic models. ▶ High concentration of DBS followed a second order kinetic model.In this work, the kinetics of mineralisation of sodium dodecylbenzenesulphonate (DBS) by TiO₂ photocatalysis has been studied. Although several works have studied the kinetics of photodegradation of the primary pollutant, the formation of organic intermediates brings a worse situation when those compounds are hardly oxidised. Total mineralisation is thus the desired objective in any oxidation process, being the kinetics a good indicator of the process efficacy. Working between 50mgL⁻¹ and 200mgL⁻¹ of DBS and catalyst loadings between 0.5gL⁻¹ and 5gL⁻¹, the mineralisation kinetics of DBS degradation by TiO₂ photocatalysis has been experimentally and theoretically analysed. The mineralisation kinetic curves presented two different zones with different slopes, the second one attributed to the intermediate compounds and with a lower rate. Data in the two zones fitted to second order kinetic models with different values of the kinetic parameters. Additionally, the kinetics of DBS removal has also been analysed observing that kinetic data corresponding to high surfactant concentration followed a second order trend similar to the mineralisation results.

Keywords: DBS; TiO; ₂; Mineralisation kinetics

SBA-15 supported Ni-Co bimetallic catalysts for enhanced hydrogen production during cellulose decomposition by Ming Zhao; Tamara L. Church; Andrew T. Harris (pp. 522-530).

Display Omitted▶ Ni and Co showed varied selectivity in the reactions during cellulose decomposition. ▶ Ni–Co alloy gave a synergetic enhancement in catalyzing H₂ generation reactions. ▶ Ni:Co=1:2 showed better activity for the formation of NiCo₂O₄ than 1:1 and 2:1. ▶ 10wt.% NiCo₂ on SBA-15 performed the best in H₂ yield and selectivity. ▶ 10wt.% NiCo₂/SBA-15 also showed much better better coke resistance than other catalysts.SBA-15 supported Ni-Co bimetallic catalysts with various loadings and Ni/Co ratios were prepared by incipient wetness impregnation and tested as catalysts in the pyrolytic decomposition of methyl cellulose. A thermogravimetric analyser coupled with a mass spectrometer (TG–MS) was used to examine the activity and selectivity for H₂ production by semi-quantitative analysis, and the new catalysts were compared with monometallic Ni and Co supported on SBA-15 and MCM-41. Catalysts were characterized by physisorption, chemisorption, reducibility test, X-ray diffraction, and scanning and transmission electron microscopy. 10wt.% NiCo₂/SBA-15 was the most active bimetallic catalyst, yielding 295mlH₂/g cellulose. The addition of water further enhanced the H₂ yield to 405ml/g cellulose and gave an H₂ selectivity of up to 28.9vol.%. This superior performance over monometallic catalysts indicated a synergy between Ni and Co, combining and enlarging individual activity and selectivity upon the main heterogeneous reactions. The improved reducibility and dispersion of Ni-Co alloying sites also contributed to this enhancement.

Keywords: Hydrogen production; Cellulose; SBA-15; Ni-Co bimetallic catalyst; TG–MS

Effect of nickel nano-particle sintering on methane reforming activity of Ni-CGO cermet anodes for internal steam reforming SOFCs by D. Hari Prasad; H.-I. Ji; H.-R. Kim; J.-W. Son; B.-K. Kim; H.-W. Lee; J.-H. Lee (pp. 531-539).

Display Omitted▶ ISRM over Ni-CGO cermet catalysts prepared by single-step GNP was investigated. ▶ Steam lean conditions showed a continuous and moderate reforming activity. ▶ Steam rich conditions showed high reforming activity which decreased with time. ▶ TEM/EDS analysis evidenced nickel nano-particle sintering effect.In the present study, a single step synthesis of nano-sized NiO–Ce_0.9Gd_0.1O₂ (NiO–CGO) composite powder was successfully accomplished by a glycine-nitrate-process (GNP) and its catalytic activity for steam reforming of methane (SRM) was investigated in the absence of electrochemical effects. From XRD, SEM and CHN analysis on the spent Ni-CGO cermet catalysts after the test with different flow rates and S/C ratios, we found that the main reason for the decrease in the reforming activity was not due to oxidation or sintering of bulk Ni catalyst and carbon formation on the catalyst surface. Time-on-stream analysis at 800°C for 80h showed a continuous decease in the reforming activity for steam rich conditions (S/C=1.5) whereas a constant and moderate reforming activity was observed for steam lean conditions (S/C=0.5). From TEM analysis it is clearly evidenced that the reason for continuous decrease in the reforming activity under steam rich conditions was due to nickel nano-particle sintering whereas no sintering occurred under steam lean conditions which indicated that the steam was primary cause for nickel nano-particle sintering. Furthermore, TEM/EDS analysis confirmed that the nickel nano-particles were mainly located on the surface of the CGO support which can suppress the carbon formation by maintaining good metal (Ni)–support (CGO) interaction even under steam lean conditions.

Keywords: Nickel nano-particle sintering; Methane steam reforming activity; SOFC; Ni-CGO cermet anodes; Glycine-nitrate-process

UV-A and UV-C induced photolytic and photocatalytic degradation of aqueous ciprofloxacin and moxifloxacin: Reaction kinetics and role of adsorption by Xander Van Doorslaer; Kristof Demeestere; Philippe M. Heynderickx; Herman Van Langenhove; Jo Dewulf (pp. 540-547).

Display Omitted▶ pH plays a significant role in both photolysis and heterogeneous photocatalysis of the emerging contaminants ciprofloxacin and moxifloxacin in water. ▶ The third generation fluoroquinolone moxifloxacin is more susceptible to photocatalytic degradation than the second generation fluoroquinolone ciprofloxacin. ▶ First-order degradation rate constants and partition ratios of the different fluoroquinolone species reveal that the photocatalytic degradation rate is strongly determined by the pH dependent adsorption on the TiO₂ catalyst surface.UV-A (485μWcm⁻²) and UV-C (389μWcm⁻²) induced photolysis and TiO₂-P25 mediated heterogeneous photocatalysis are investigated as advanced oxidation technologies for the removal of fluoroquinolone (FQ) antibiotics ciprofloxacin (CIP) and moxifloxacin (MOX) in aqueous solution. Experiments performed in a thermostated (298K) lab scale batch reactor show that pH is of main importance for FQ degradation kinetics with both processes. Whereas apparent first-order kinetics of UV-A photolysis were slow for both FQs in the entire investigated pH range ( k_1,CIP≤0.015min⁻¹; k_1,MOX≤0.006min⁻¹ at 3≤pH≤10), UV-C photolysis was faster with maximum k-values obtained at pH 7 and pH 10 for CIP ( k_1,CIP=0.072min⁻¹) and MOX ( k_1,MOX=0.058min⁻¹), respectively. The highest removal rates, however, are obtained at pH 7 in the presence of TiO₂ (0.5gL⁻¹) as a photocatalyst ( k_1,CIP,UV-A=0.137min⁻¹, k_1,CIP,UV-C=0.163min⁻¹; k_1,MOX,UV-A=0.227min⁻¹; k_1,MOX,UV-C=0.236min⁻¹). Both the difference in reaction kinetics between photolysis and heterogeneous photocatalysis and the observed pH dependency indicate that surface reactions are of main importance during TiO₂/UV photocatalysis. A positive relationship is noticed between the photocatalytic FQ degradation rate and the fraction of FQ adsorbed onto the catalyst surface, with the latter being strongly pH dependent. Adsorption experiments reveal that FQ adsorption is favoured at neutral pH. Explanations are proposed based on the amphoteric nature of the FQ molecules and the pH dependent catalyst surface charge. Based on reported pK_a values and experimental adsorption data, partition ratios are calculated for the different FQ species. These indicate that mainly the single positively charged and zwitter FQ ion participate in the adsorption process, explaining the highest photocatalytic degradation at pH 7.

Keywords: Abbreviations; AOP; advanced oxidation process; CIP; ciprofloxacin; CB; conduction band; DDD; defined daily dose; ESAC; European Surveillance of Antimicrobial Consumption; HPLC; high pressure liquid chromatography; ISC; inter system crossing; FQ; fluoroquinolone; MOX; moxifloxacin; ODR; orthogonal distance regression; PDA; photodiode array detector; PZC; point of zero charge; ROS; reactive oxygen species; RSSQ; residual sum of squares; VB; valence band; VDW; van der WaalsHeterogeneous photocatalysis; Photolysis; Adsorption; Moxifloxacin; Ciprofloxacin

Microstructure characterization and propane oxidation over supported Ru nanoparticles synthesized by the microwave-polyol method by Janina Okal; Mirosław Zawadzki; Włodzimierz Tylus (pp. 548-559).

Display Omitted▶ The supported Ru nanoparticles are very active and stable for propane oxidation. ▶ The 1.6nm Ru nanoparticles exhibit higher activity than 6nm nanoparticles. ▶ In oxygen atmosphere Ru nanoparticles possesses good stability up to 250°C. ▶ The metallic and oxide Ru species plays important role for propane oxidation.Ruthenium nanoparticles deposited on γ-Al₂O₃ were prepared in one step by a microwave-polyol method and tested in the complete oxidation of propane. The oxidation reaction was carried out under oxygen rich-conditions over the as prepared colloidal 4.9wt.% Ru/γ-Al₂O₃ catalyst and heated in H₂ at 500°C for 15h. The as prepared catalyst contained Ru nanoparticles with mean size of 1.6nm and narrow size distribution, while hydrogen treated metal particles with mean size of 6nm. Before examining catalytic properties, the Ru nanoparticles were subjected to heat treatment in oxygen atmosphere to study their microstructure evolution. HRTEM, SAED, XRD, BET, XPS, as well as hydrogen chemisorption and O₂ uptake techniques were applied to characterize the supported Ru nanoparticles. It was established that catalyst with the 1.6nm Ru nanoparticles exhibited slightly higher specific activity than the catalyst with the 6nm Ru nanoparticles. The superior catalytic performance of the Ru nanoparticles could be correlated with a high metallic dispersion and low particle sizes. It was evidenced that the most active sites in the propane oxidation reaction, consist small Ru_xO_y clusters without well-defined stoichiometry. Such surface species were formed at 100–200°C, and as a result the as prepared Ru/γ-Al₂O₃ catalyst reached 100% propane conversion below 200°C. Moreover, the Ru nanoparticles under oxidative atmosphere up to 250°C, both in oxygen and in reaction of propane oxidation, possesses good stability and the ruthenium phase was not agglomerated. In consequence, recycling of the supported Ru nanoparticles results only in an insignificant loss of the catalytic activity. The very good catalytic performances of supported Ru nanoparticles prepared under microwave-polyol conditions, preserved after consecutive runs, make them promising for practical application in the purification of environmental pollutions.

Keywords: Metal nanoparticles; Propane oxidation; Ru nanocatalyst; TEM; XPS; O; ₂; uptake

Gold nanoparticles supported on hydroxylapatite as high performance catalysts for low temperature CO oxidation by Jun Huang; Lu-Cun Wang; Yong-Mei Liu; Yong Cao; He-Yong He; Kang-Nian Fan (pp. 560-569).

Display Omitted▶ Calcination atmosphere strongly influences the activity of gold on hydroxylapatite. ▶ Highest initial activity is obtained for inertly He-calcined Au/HAP-He. ▶ Calcination in oxidative O₂ environment leads to highest steady-state activity.A series of gold supported on hydroxylapatite (HAP) catalysts were prepared by deposition–precipitation with urea to study the influence of calcination atmosphere, i.e., H₂, He and O₂, on the performance of the catalyst in low-temperature CO oxidation. Calcination atmosphere was found to have an important influence on the catalytic activity and stability of Au/HAP. The highest initial activity was obtained for Au/HAP-He obtained by inert He-calcination, which, however, suffered the most severe deactivation with time on stream. Calcination in oxidative O₂ environment resulted in the best stability and highest steady-state activity among the three catalysts. TEM results revealed that inert He-calcination can produce the smallest Au nanoparticles over the HAP support, which was suggested to be responsible for the highest initial activity of Au/HAP-He. Based on the CO₂-TPD and in situ DRIFTS studies, the superior stability of Au/HAP-O₂ can be attributed to a limited surface basicity in this material.

Keywords: Hydroxyapatite; Supported gold catalysts; Calcination atmosphere; CO oxidation; Catalyst stability

Catalytic oxidation of toluene over Pd/Co₃AlO catalysts derived from hydrotalcite-like compounds: Effects of preparation methods by Peng Li; Chi He; Jie Cheng; Chun Yan Ma; Bao Juan Dou; Zheng Ping Hao (pp. 570-579).

Display Omitted▶ Hydrotalcite-derived Pd/Co₃AlO catalysts were prepared by various synthesis methods. ▶ The preparation methods had a s

Keywords: ignificant influence on toluene catalytic activity. ▶ Pd/Co₃AlO (COP) with highly dispersed Pd species exhibits the highest activity. ▶ The synergistic effect of Pd and Co₃O₄ is a decisive factor in catalyst activity.A series of novel Pd/Co₃AlO catalysts derived from hydrotalcite-like compounds (HTlcs) have been prepared and investigated for total oxidation of toluene. The HTlcs phase Co–Al precursors were prepared by coprecipitation method and Pd active species were introduced by different approaches, i.e., impregnation (IMP), wet ion exchange (WIE) or directly at coprecipitation stage (COP). It is found that all hydrotalcite-derived Pd/Co₃AlO catalysts are much more active than the Pd/Co₃AlO catalyst prepared via traditional thermal combustion method (TCB) in toluene elimination. The activities of all synthesized catalysts obey the following sequence: Pd/Co₃AlO (COP)>Pd/Co₃AlO (WIE)≥Pd/Co₃AlO (IMP)>Pd/Co₃AlO (TCB). Excellent catalytic activities of the novel hydrotalicite-derived Pd/Co₃AlO catalysts could be contributed to their high surface area, small mean crystallized size of support and highly dispersed PdO particles. Besides, they are well positively associated with catalyst reducibilities and the amounts of oxygen vacancies. According to the XPS, TEM and TPR results, it was found that the strong synergistic effect between Co₃O₄ and PdO, but not the amount of the surface palladium species which are generally believed to be the active sites, is the main factors determining the catalytic activity in this work. The stability tests indicate that all Pd/Co₃AlO catalysts have no obvious deactivation, and some catalysts even show improved activities during the reaction process due to the emergence of metal Pd.

Photodegradation of rhodamine B and 4-chlorophenol using plasmonic photocatalyst of Ag–AgI/Fe₃O₄@SiO₂ magnetic nanoparticle under visible light irradiation by Jian-Feng Guo; Bowen Ma; Anyuan Yin; Kangnian Fan; Wei-Lin Dai (pp. 580-586).

Display Omitted▶ A new plasmonic photocatalyst of Ag–AgI/Fe₃O₄@SiO₂ was prepared by deposition–precipitation and photoreduction method. ▶ The catalyst exhibited efficient activity for the degradation of RhB and 4-CP under visible light irradiation. ▶ The degradation rate over this catalyst was about 10 times higher than that of N–TiO₂. ▶ The catalyst could be easily recovered owing to its paramagnetic property.A new plasmonic photocatalyst of Ag–AgI/Fe₃O₄@SiO₂ was prepared by deposition–precipitation and photoreduction method. The catalyst exhibited efficient photocatalytic activity for the degradation of rhodamine B dye and 4-chlorophenol under visible light irradiation. The degradation rate of rhodamine B and 4-chlorophenol over Ag–AgI/Fe₃O₄@SiO₂ was about 10 times and 4.1 times faster than that of N–TiO₂, respectively. The catalyst could be easily recovered due to its paramagnetic property. X-ray diffraction, X-ray photoelectron spectroscopy and transmission electron microscope were used to characterize the catalyst. The specified photocatalytic reaction and the study of electron paramagnetic resonance verified that both the O₂⁻ andOH radicals were the main active species in this reaction.

Keywords: Photocatalyst; Visible-light-driven; Plasmon resonance; Magnetic nanoparticle; Rhodamine B dye; 4-Chlorophenol

Challenges in the production of sustainable fuels from pyrolysis oil – Design of efficient catalysts for gasification of char by B. Matas Güell; G. van Rossum; W.P.M. van Swaaij; S.R.A. Kersten; L. Lefferts; K. Seshan (pp. 587-597).

Display Omitted▶ Ceria–zirconia allows gasification of char from pyrolysis oil with steam/CO₂ at low temperatures. ▶ The proposed catalyst mechanism involved in the gasification of char is red-ox type. ▶ The ceria–zirconia catalyst makes char more reactive. ▶ Ceria–zirconia facilitates the contact between char and catalyst, essential for char gasification.The catalytic performance of a ceria–zirconia based catalyst for (i) steam/CO₂ gasification and (ii) combustion of char produced during pyrolysis oil evaporation was investigated and compared with the non-catalytic scenario in the temperature range 600–800°C. Kinetic studies revealed that the presence of the ceria–zirconia catalyst enhanced char gasification rates significantly, up to one order of magnitude at 800°C, for both steam and CO₂ gasification. It is suggested that the red-ox properties of the ceria–zirconia catalyst play a significant role in char gasification, by allowing oxygen mobility and activation of H₂O and CO₂. Furthermore, XPS and SEM characterization studies showed that the catalyst also influences the nature of char formed during pyrolysis-oil evaporation to a great extent, by forming oxygenated species which are expected to be more reactive.

Keywords: Char; Gasification; Catalyst; Ceria; Pyrolysis-oil; Activation energy

Surface structure sensitivity of manganese oxides for low-temperature selective catalytic reduction of NO with NH₃ by Chao Wang; Liang Sun; Qingqing Cao; Bingqing Hu; Zhiwei Huang; Xingfu Tang (pp. 598-605).

Display Omitted▶ NH₃–SCR reactions occurring on external surface of hollandite manganese oxides. ▶ Semitunnel structured external surfaces suitable for adsorption of NH₃. ▶ Active surface oxygen atoms facilitating activation of NH₃.Hollandite-type manganese oxides with K⁺ or H⁺ cations in the tunnels (K-Hol or H-Hol) were successfully synthesized and investigated in low-temperature selective catalytic reduction of NO by NH₃. The results of the catalytic tests revealed that both K-Hol and H-Hol with almost same catalytic activities had much higher reaction rates than β-MnO₂ under the same conditions, and even at a high gas hourly space velocity of 160,000h⁻¹, K-Hol obtained more than 90% conversions of NO in a wide temperature window of 100–300°C. The high resolution transmission electron microscopy observations showed that both K-Hol and β-MnO₂ were tetragonal prism-shaped nanorods with same exposed {110} planes, and the atoms in the {110} planes of K-Hol arranged to form semitunnel structures, while the {110} planes of β-MnO₂ were relatively smooth surfaces. The temperature-programmed reduction by H₂ and thermal gravimetric analyses indicated that active surface lattice oxygen atoms of K-Hol were around 1.6% with respect to total lattice oxygen atoms. The transition reactions of NH₃ demonstrated that K-Hol with special semitunnel structured surface and active surface lattice oxygen showed much stronger ability to efficiently adsorb and activate NH₃ molecules than β-MnO₂. Hence, both efficient semitunnel structured external surfaces and high active surface lattice oxygen atoms predominantly accounted for the high catalytic activities.

Keywords: Hollandite-type manganese oxides; Selective catalytic reduction of NO; Ammonia; Semitunnel structured external surface; Active surface lattice oxygen

Catalytic destruction of chlorinated aromatic pollutants over mesoporous Cu_xMg1−_xAl₂O₄ spinel oxides by Yun Fan; Xianbo Lu; Yuwen Ni; Haijun Zhang; Meiwen Zhu; Yun Li; Jiping Chen (pp. 606-612).

Display Omitted▶ The Cu_xMg1−_xAl₂O₄ spinel-type catalysts exhibit high catalytic activity for the dechlorination of polychlorinated aromatics. ▶ The low copper content spinel-type catalyst Cu_0.2Mg_0.8Al₂O₄ presents a good potential for the thermal treatment of polychlorinated aromatics at lower temperatures. ▶ The Cu_0.2Mg_0.8Al₂O₄ spinel-type catalyst inhibits the chlorination reaction.Destruction of chlorinated aromatic compounds was carried out over mesoporous Cu_xMg1−_xAl₂O₄ spinel oxides with x=0, 0.2, 0.5 and 0.8, which were prepared by the coprecipitation method. All the catalyst samples were characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM) and nitrogen adsorption–desorption isotherms. The performances of these catalysts on the decomposition of hexachlorobenzene (HCB) and the catalytic formation of polychlorinated dibenzodioxin and dibenzofuran (PCDD/F) were evaluated in a closed system. The activities of these catalysts for dechlorination of HCB increased with increasing the magnesium content in them. The Cu_0.2Mg_0.8Al₂O₄ presented a higher catalytic activity for the hydrodechlorination of HCB than CuO, Al₂O₃, as well as the other Cu_xMg1−_xAl₂O₄ spinels. More than 99% dechlorination efficiency of HCB was achieved at low temperatures (≤300°C) for a short time (30min) under air atmosphere over Cu_0.2Mg_0.8Al₂O₄ spinel. In comparison to air atmosphere, nitrogen atmosphere seemed to be more beneficial for the dechlorination of HCB with a dechlorination efficiency of 90% at 250°C for 10min. For the Cu_0.2Mg_0.8Al₂O₄ catalyst, the I-TEQ of PCDD/F formed was 4.5pg/g, far below the value of 15122.5pg/g on CuO. The Cu_0.2Mg_0.8Al₂O₄ catalyst inhibited the chlorination reaction and enhanced the dechlorination reaction. The catalytic behavior including catalytic dechlorination of HCB and catalytic formation of PCDD/F related to the physical characteristics of Cu_xMg1−_xAl₂O₄ spinel was discussed.

Keywords: Spinel; Hexachlorobenzene; Polychlorinated dibenzodioxin and dibenzofuran; Hydrodechlorination; Catalytic formation

Catalytic cracking in the presence of guaiacol by I. Graça; J.M. Lopes; M.F. Ribeiro; F. Ramôa Ribeiro; H.S. Cerqueira; M.B.B. de Almeida (pp. 613-621).

Display Omitted▶ When gasoil is cracked at 535°C in the presence of guaiacol, overall conversion increases. ▶ An increase in benzene, toluene and xylene (BTX) was observed in the presence of guaiacol. ▶ At constant conversion, the ZSM-5 additive reduces the xylene yield without affecting benzene and toluene.The use of renewable fuels is expected to grow in the coming years. A possibility to achieve this consists in blending renewable bio-oils with conventional refining streams to further process in existing refineries. A key aspect of bio-oils is the presence of oxygenate molecules in significant amounts. To shed light into the effect of these compounds on Fluid Catalytic Cracking (FCC), guaiacol was chosen as model compound. Data on the transformation of n-heptane in the presence of small quantities of guaiacol over pure HY and HZSM-5 zeolites at 450°C is presented and compared to gasoil+guaiacol blend tests using an industrial FCC equilibrium catalyst (E-CAT) pure and blended with a commercial ZSM-5 additive. Guaiacol has a negative influence on both n-heptane and gasoil conversions, since it is responsible for an increase of the coke retained on the catalysts. In the presence of n-heptane and with pure zeolites, guaiacol increases the methane yield, in line with its transformation into phenol. With industrial FCC E-CAT, the presence of guaiacol increases gasoline yield and reduces coke yield, however, increases coke on catalyst. Detailed GC analysis of the liquid product shows presence of phenols in the gasoline cut, suggesting the partial conversion of guaiacol (with methane and water formation). HZSM-5 zeolite was more severely deactivated than HY zeolite in the n-heptane transformation, which agrees with the observed reduction of the ZSM-5 additive effect on the transformation of gasoil.

Keywords: Fluid Catalytic Cracking; Bio-oils; Guaiacol; Co-processing; Deactivation; FCC industrial catalysts; Zeolites

Effect of water on the oxidation of dichlorobenzene over V₂O₅/TiO₂ catalysts by Casey E. Hetrick; Florian Patcas; Michael D. Amiridis (pp. 622-628).

Display Omitted▶ The presence of water during the oxidation of m-DCB over a 3.6wt.% V₂O₅/TiO₂ catalysts results in a bimodal activation/deactivation behavior depending on the reaction temperature. ▶ The magnitude of these water effects is proportional to the water concentration added to the feed. ▶ These water effects are completely reversible, although the transient behavior differs at different temperatures. ▶ The formation of some partial oxidation byproducts was also observed and the selectivities towards such products, although in general remained low, increased in the presence of water.The addition of water during the oxidation of m-dichlorobenzene over a 3.6wt.% V₂O₅/TiO₂ catalyst resulted in an unusual bimodal activation/deactivation behavior at different temperatures. Catalyst activity increased at temperatures up to 300°C, with a maximum observed at 270°C, while it decreased at temperatures above 300°C with a minimum observed at 350°C. This effect was proportional to the concentration of water in the feed stream. At lower reaction temperatures (i.e., <270°C), the addition of water resulted in a lower concentration of surface chloride and carbonaceous deposits. In contrast, at higher reaction temperatures (i.e., >350°C), the presence of water did not affect the surface carbon and chlorine contents, but resulted in the deactivation of the catalyst due to the competitive adsorption on the active sites. Characterization of used catalyst samples indicated no changes in bulk characteristics, suggesting that the effect of water was limited to only reversible changes taking place on the catalyst surface. Finally, the presence of water also favored the formation of partial oxidation products, although the overall selectivity towards such products still remained low (i.e., yields below 3%).

Keywords: Polychlorinated aromatics; m; -Dichlorobenzene; Catalytic oxidation; V; ₂; O; ₅; /TiO; ₂; Water effect

Supported Au catalysts for low-temperature abatement of propene and toluene, as model VOCs: Support effect by M. Ousmane; L.F. Liotta; G.Di Carlo; G. Pantaleo; A.M. Venezia; G. Deganello; L. Retailleau; A. Boreave; A. Giroir-Fendler (pp. 629-637).

Conversion (%) of (■) propene and (●) toluene versus temperature over Au/CeO₂ catalyst.Display Omitted▶ Au/CeO₂ is the best performing catalyst in the full oxidation of propene and toluene. ▶ Stable propene conversion was registered in a long-run over Au/CeO₂ at 135̊C for 50h. ▶ The activity of Au/Al₂O₃ was highly improved by doping with CeO₂ (7.5wt%). ▶ The oxygen vacancies present in the (7.5wt%) CeO₂/Al₂O₃ stabilize gold nanoparticles. ▶ The interaction of gold nanoparticles with the support enhances the activity.In this work gold nanoparticles supported over ceria (Au/CeO₂), titania (Au/TiO₂), alumina (Au/Al₂O₃) and Ce doped alumina (Au/7.5Ce/Al₂O₃) were prepared by deposition–precipitation (DP) method with NaOH solution and characterized by BET, XRD, H₂-TPR, TEM and XPS techniques. The catalytic activity was evaluated in the total oxidation of propene and toluene, chosen as model VOC molecules. The attention was focused on the catalyst stability. To this aim, three consecutive catalytic cycles in propene and toluene oxidation were performed for each catalyst. The activity trend was Au/CeO₂>Au/7.5Ce/Al₂O₃>Au/TiO₂>Au/Al₂O₃. Over Au/CeO₂, the most active catalyst, a long-term propene oxidation test running for 50h, at low-temperature, 135°C was also carried out. Characterizations XRD and XPS were carried out on the spent catalyst after three catalytic runs in propene oxidation.The results were discussed in terms of structural, electronic, catalytic and reduction properties as a function of the nature of the support.

Keywords: Au; CeO; ₂; Ce-doped Al; ₂; O; ₃; Propene; Toluene oxidation; Stability tests; Role of oxygen vacancies

Catalytic and structural properties of co-precipitated Mg–Zr mixed oxides for furfural valorization via aqueous aldol condensation with acetone by I. Sádaba; M. Ojeda; R. Mariscal; J.L.G. Fierro; M. López Granados (pp. 638-648).

Display Omitted▶ Zr⁴⁺ presence at the surface of MgO generates the most active sites for aldol condensation of furfural with acetone: Mg–O–Zr species. ▶ This reaction is the initial step to synthesize second generation biofuels from lignocellulosic biomass.A series of MgO–ZrO₂ mixed oxides with different nominal Mg/(Mg+Zr) atomic ratios (0, 0.1, 0.3, 0.5, 0.75, 0.85 0.92) were prepared by co-precipitation and calcined at 873K. The catalytic activity in aldol condensation of furfural with acetone was tested in aqueous medium. These solids were systematically characterized by XRD, TEM, XPS, N₂ adsorption–desorption isotherms and thermal analysis.Mg_xZr1−_xO2−_x solid solution with cubic ZrO₂ structure was the only phase observed for the mixed solids with Mg/(Mg+Zr) atomic ratio ≤0.3, which had very low activity. Two different phases were observed in solids with a nominal Mg/(Mg+Zr) atomic ratio ≥0.5: cubic MgO and c-Mg_xZr1−_xO2−_x. Moreover, the relative concentration of the latter phase decreases as the Mg concentration increases. Zr⁴⁺ cations are present at the surface of the c-MgO, the concentration of which is lower in the Mg-richer samples. No significant differences were found between the overall catalytic activity of these samples. Therefore, three different active surface sites can be found in these solids: Mg–O–Mg sites co-existing with Mg–O–Zr sites at the surface of c-MgO, and Mg–O–Zr sites at the surface of c-Mg_xZr1−_xO2−_x. The Mg–O–Zr sites on c-MgO are much more active than the other two sites, which show similar intrinsic activity. The overall activity of each catalyst depends on the amount of each of these surface sites and on their intrinsic activity. Reutilization tests and characterization of the used catalysts suggests that the most probable causes of deactivation are fouling and/or poisoning of the surface sites by furfural derived heavy compounds, leaching of Mg²⁺ and Zr⁴⁺ cations, or hydration of the Mg oxide.

Keywords: Biomass; Furfural; Claisen-Schmidt condensation; Biofuels; Furfurylidene

Hydrothermal deactivation of Fe-ZSM-5 catalysts for the selective catalytic reduction of NO with NH₃ by Sandro Brandenberger; Oliver Kröcher; Maria Casapu; Arno Tissler; Roderik Althoff (pp. 649-659).

Display Omitted▶ The hydrothermal breakdown of Fe-ZSM-5 is dominated by three parallel processes:•The rapid dealumination of Al–OH–Si sites.•The rapid depletion of dimeric iron species.•The slow migration of isolated iron ions.The hydrothermal deactivation of Fe-ZSM-5 catalysts for the reduction of NO with NH₃ in the presence of 10% H₂O was studied. Aged and fresh catalysts were characterized by H-TPR, DRIFTS,²⁷Al NMR,²⁹Si NMR, XAS and nitrogen physisorption. The analysis of deactivated catalysts indicated that, under moderately aging conditions, dealumination due to hydrolysis occurs only on Al sites that bear a Brønsted acidic proton. Furthermore, the results showed that the cause of hydrothermal aging is Fe migration, which leads to the formation of FeO_x clusters that increase in size as the age of the catalyst increases. This Fe migration was not strongly related to the process of dealumination and the stability with respect to SCR activity depends more on the stability of the active iron species in ion exchange sites than the stability of the framework itself. The hydrothermal stability of these active iron sites was not significantly influenced by the presence of Brønsted acid protons. The remaining activity after hydrothermal aging is caused by isolated iron ions located at ion exchange sites. Based on these results a general mechanism for aging under hydrothermal conditions was developed that differentiates between dealumination, migration and clustering of Fe oxides and the temporal sequence of these processes.

Keywords: Selective catalytic reduction (SCR); Ammonia; NO; _x; Hydrothermal aging; Deactivation; NO; _x; reduction efficiency; DeNOx; Fe-ZSM-5; Zeolite

Preleached Pd–Pt–Ni and binary Pd–Pt electrocatalysts for oxygen reduction reaction in proton exchange membrane fuel cells by Juan Zhao; Arumugam Manthiram (pp. 660-668).

Display Omitted▶ Formation of a Pd-rich core and Pt-rich shell structure results in catalytic activity enhancement. ▶ Pre-leaching the catalyst in acid effectively enhances the overall performance and durability. ▶ The preleached catalyst shows an improved Pt-mass activity twice of that of commercial Pt.Ternary preleached Pd–Pt–Ni and binary Pd–Pt catalysts have been synthesized, characterized, and evaluated as oxygen reduction reaction (ORR) electrocatalysts in single cell proton exchange membrane fuel cells (PEMFC), and the data have been compared with those of Pd–Pt–Ni catalyst. All the three catalysts show much improved Pt-mass activity compared to the state-of-the-art Pt catalyst. The preleached catalyst shows surface catalytic activity improvement by a factor of 2 in terms of Pt-mass activity and 3.5 in terms of specific activity compared to commercial Pt. Based on compositional analysis before and after the fuel cell test, the enhanced activity is attributed to an active phase with a Pd-rich core and Pt-rich shell structure. The strain introduced in the outer shell layer by the lattice parameter mismatch between the core and shell could downshift the metal d-band center, reduce the adsorption energy of hydroxyl species, and thus increase the intrinsic activity. The surface morphology and geometric effect induced by compositional and structural changes may also play a role.

Keywords: Fuel cells; Electrocatalysts; Acid-leached catalysts

Low-temperature oxidation of carbon monoxide and methane over alumina and ceria supported platinum catalysts by Per-Anders Carlsson; Magnus Skoglundh (pp. 669-675).

Display Omitted▶ Heterogeneous distribution of active material for improved low-temperature activity. ▶ Utilizing the interplay between diffusion and reaction for design of efficient catalysts. ▶ Highly active sites for oxidation of CO and CH₄ at Pt–ceria interface.The ignition and extinction processes for total oxidation of CO, CH₄ and CO+CH₄ mixture in oxygen excess over Pt/Al₂O₃ and Pt/CeO₂ catalysts with the platinum phase distributed either homogeneously or heterogeneously (i.e., locally high platinum concentration) in the support have been studied by temperature programmed oxidation experiments. Following the preparation methods by Arnby et al. , the samples have the same Pt load and dispersion. Generally the catalytic activity follows the order: Pt/CeO₂ (heterogeneous)>Pt/CeO₂ (homogeneous)>Pt/Al₂O₃ (heterogeneous)>Pt/Al₂O₃ (homogeneous) as indicated by lower ignition and/or extinction temperatures. For Pt/Al₂O₃, the addition of NO₂ to the reactant stream increases the rate of oxidation of CO in the pre-ignition regime although the light-off temperature T₅₀ is shifted towards higher temperatures (except for low CO concentrations). In the case of the Pt/CeO₂, the CO conversion generally decreases. For CH₄ oxidation in the presence of NO₂, the conversion increases for Pt/Al₂O₃ and decreases for Pt/CeO₂. The addition of CO₂ in the reactant stream has minor influence on CO oxidation over Pt/Al₂O₃ while for Pt/CeO₂, T₅₀ is shifted towards higher temperatures. For the simultaneous oxidation of CO and CH₄, a reverse hysteresis for methane oxidation is observed, i.e., the extinction process occurs at higher temperature than the corresponding ignition process. The improved activity for CO oxidation over samples with heterogeneous Pt distribution is likely due to less tendency towards CO self-poisoning through the development of steeper concentration gradients in the Pt containing regions in the porous support material. The significant increase of activity for both reactions over ceria-supported Pt is here assigned to highly active sites at the platinum–ceria boundary but also, to some extent, the oxygen storage and release function and dynamics of the transport of oxygen in the Pt/CeO₂ system.

Keywords: Catalytic ignition; Catalytic extinction; Metal–support interactions; Diffusion

Photocatalytic activity of TiO₂ thin films deposited by cathodic arc by A. Kleiman; A. Márquez; M.L. Vera; J.M. Meichtry; M.I. Litter (pp. 676-681).

Display Omitted▶ Anatase films grown by cathodic arcs ( CA) were tested as photocatalysts for Cr(VI) reduction. ▶ Films grown by CA showed lower photoactivity than TiO₂ P-25 films obtained by dip-coating. ▶ Adhesion properties of CA films were much better. ▶ The reaction efficiency of CA films was improved by increasing the film thickness. ▶ CA films are very suitable for application in gas and aqueous photocatalytic systems.In this work, the photocatalytic activity and the kinetic behavior of anatase TiO₂ films deposited by cathodic arc ( CA films) on glass substrates are reported and compared with those of TiO₂ Degussa P-25 films obtained by dip-coating immersion ( DC films). The mass density of films, determined by X-ray reflectometry was 20% lower for DC films compared with CA films, indicating a higher porosity of DC samples. The activity was evaluated from the efficiency to reduce Cr(VI) in the presence of EDTA. Although the response of CA films resulted lower compared with that of P-25 films of the same TiO₂ content ( e.g. 90% vs. 50% Cr(VI) reduction after 180min irradiation for samples with 0.03mgcm⁻² of TiO₂), a fact associated to the lower porosity, adhesion properties of the new materials were much better. CA film photoactivity improved by increasing the coating thickness; after 180min, a sample with 0.03mgcm⁻² of TiO₂ presented 50% of Cr(VI) reduction vs. 80% for a sample with 0.28mgcm⁻². These photocatalysts, whose preparation is simple and affordable, are very promising to be used as immobilized materials in photoreactors for the treatment of pollutants in gaseous and aqueous systems.

Keywords: TiO; ₂; Thin films; Cathodic arc deposition; Heterogeneous photocatalysis; Cr(VI) photocatalytic reduction

Influence of controlled spatial deposition of Pt and Pd in NO_x storage-reduction catalysts on their efficiency by Robert Büchel; Sotiris E. Pratsinis; Alfons Baiker (pp. 682-689).

Display Omitted▶ Novel NSR catalysts have been prepared by flame spray pyrolysis using a twin nozzle system. ▶ The noble metals (Pt, Pd) were selectively deposited on storage component and support. ▶ The NSR efficiency of these catalysts depends strongly on the location of the noble metal. ▶ Bimetallic Pt/Pd systems showed superior NSR performance at temperatures >300°C. ▶ Palladium only catalysts were inefficient at lower temperatures (<250°C).Catalysts for NO_x storage and reduction (NSR) were prepared with a twin flame spray pyrolysis (FSP) unit allowing the preferential deposition of Pd and/or Pt nanoparticles on the catalyst's storage (K₂CO₃) or support (Al₂O₃) components. The structural properties of the catalysts were characterized by nitrogen adsorption, CO chemisorption combined with diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), X-ray diffraction, and electron microscopy. Various combinations with Pt and Pd either deposited on the storage component (K₂CO₃) or the support (Al₂O₃) were tested by fuel lean/rich cycling exhibiting NO_x conversion above 90% at 300°C. At 250°C the best performance was achieved when Pt was deposited on K₂CO₃, whereas Pd was more active when deposited on Al₂O₃, albeit the activity of Pd to reduce NO_x was low. Mixing Pd with Pt, that is depositing both noble metals on the same component (storage component or support), lowered the NO_x conversion, in some cases even below that of Pt only catalysts. In Pt/Pd/Ba/CeO₂ catalysts, where Pd was deposited on the Ba storage component and Pt on the CeO₂ support, Pd became active above 300°C showing best reduction performance. At these temperatures Pt/Pd/Ba/CeO₂ catalysts where the two noble metals were separated by deposition on the storage and support components showed superior behavior compared to corresponding single noble metal catalysts.

Keywords: NO; _x; storage-reduction; Potassium carbonate; Flame spray pyrolysis; Lean NO; _x; trap; Palladium; Platinum; Selective noble metal deposition

Hydrogen production by steam reforming of dimethyl ether over Pd-based catalytic monoliths by Cristian Ledesma; Umit S. Ozkan; Jordi Llorca (pp. 690-697).

Display Omitted▶ Pd-based catalytic monoliths are active for DME steam reforming for hydrogen production. ▶ The most active formulations are Pd/Al₂O₃, Pd/ZrO₂, Pd/CeO₂ and Pd/WO₃. ▶ The highest hydrogen yield and low CH₄ production is obtained over Pd/ZrO₂. ▶ Intermediate DME formate species are identified over Pd/ZrO₂.Catalytic monoliths based on palladium supported on several inorganic oxides were prepared and characterized by XRD, HRTEM and NH₃-TPD. The role of palladium and support in the dimethyl ether steam reforming reaction under a steam-to-carbon S/C=1.5 at 473–823K was evaluated. The best catalytic performance in terms of hydrogen yield and low CH₄ production was obtained over Pd/ZrO₂ catalytic monolith. There is no apparent correlation between the hydrogen yield and acidity of the support and/or palladium dispersion, indicating that the interaction between Pd particles and the support may be a key factor in determining the catalytic performance. The reaction mechanism was studied by DRIFTS experiments. In addition to favor hydrogen recombination, Pd facilitates the formation of a methoxy intermediate species and its subsequent evolution into a reactive formate species.

Keywords: Hydrogen; Dimethyl ether; Steam reforming; Catalytic monolith; Palladium

Remarkable effect of the incorporation of titanium on the catalytic activity and SO₂ poisoning resistance of magnetic Mn–Fe spinel for elemental mercury capture by Shijian Yang; Yongfu Guo; Naiqiang Yan; Daqing Wu; Hongping He; Jiangkun Xie; Zan Qu; Jinping Jia (pp. 698-708).

Display Omitted▶ Hg⁰ capture by Mn–Fe spinel can be promoted by the incorporation of Ti. ▶ Ti in Mn–Fe spinel can improve its SO₂ poisoning resistance. ▶ Fe–Ti–Mn spinel can be magnetically separated from the fly ash.Tiantium (Ti) was incorporated into non-stoichiometric Mn–Fe spinel to improve its performance for elemental mercury capture. Although the number of Mn⁴⁺ cations on (Fe₂Ti_xMn1−_x)1−_δO₄ was less than that on the corresponding (Fe3−_xMn_x)1−_δO₄, the number of usable cation vacancies for elemental mercury oxidization obviously increased. As a result, elemental mercury capture by Mn–Fe spinel was generally promoted by the incorporation of Ti. Furthermore, SO₂ mainly reacted with ≡Fe^III–OH and few Mn⁴⁺ cations on the surface reacted with SO₂ at lower temperatures (100–150°C), so SO₂ poisoning resistance improved at lower temperatures due to the incorporation of Ti. Especially, (Fe₂Ti_0.5Mn_0.5)1−_δO₄ showed an excellent capacity (4.2mgg⁻¹) for elemental mercury capture in the presence of a high concentration of SO₂ at 150°C. Meanwhile, (Fe₂Ti_0.5Mn_0.5)1−_δO₄ with the saturation magnetization of 30.6emug⁻¹ can be readily separated from the fly ash using magnetic separation, leaving the fly ash essentially free of catalyst and adsorbed HgO. Therefore, nanosized (Fe₂Ti_0.5Mn_0.5)1−_δO₄ may be a promising candidate catalyst for elemental mercury capture.

Keywords: Fe–Ti–Mn spinel; Elemental mercury; Capture capacity; Magnetic catalyst; SO; ₂; poisoning

Effect of aqueous matrix species on synergistic removal of bisphenol-A under solar irradiation using nitrogen-doped TiO₂/AC composite by Pow-Seng Yap; Teik-Thye Lim (pp. 709-717).

Display Omitted▶ A bi-functional composite, namely N–TiO₂/AC was synthesized via sol–gel method. ▶ Provision of activated carbon support abated the detrimental effects of SO₄²⁻. ▶ Addition of 0.01–0.1mM H₂PO₄⁻ enhanced bisphenol-A photodegradation efficiency. ▶ Addition of C₂O₄²⁻ revealed that bisphenol-A could also be photodegraded by holes.A bi-functional composite, namely nitrogen-doped titanium dioxide anchored on activated carbon (N–TiO₂/AC) was synthesized using the sol–gel method with two-stage calcination procedure. Bisphenol-A (BPA) was used as a model contaminant. The effects of co-existing aqueous species viz. prevalent inorganic anions (Cl⁻, NO₃⁻, SO₄²⁻, HCO₃⁻, H₂PO₄⁻ and silica), organic anion (C₂O₄²⁻), photocatalysis inhibitor (CH₃OH) and oxidant (H₂O₂) were comprehensively studied using the best performing composite, i.e. N–TiO₂/AC (400M-700T). Introduction of H₂PO₄⁻ (0.01–0.1mM) led to a slight enhancement in the photocatalytic degradation (PCD) efficiency for BPA removal. Provision of AC support for N–TiO₂ abated the inhibitory effect induced by SO₄²⁻ at high concentration (up to 100mM). Decreased BPA photodegradation was observed with increasing concentrations of C₂O₄²⁻, thus suggesting that direct hole (h⁺) oxidation occurred. Variation of pH (from 4 to 10) in the presence of 0.1mM of silica induced little effect on BPA photodegradation. Addition of H₂O₂ into N–TiO₂/AC system apparently resulted in decreased BPA removal because some adsorbed BPA was released from surface-degraded AC.

Keywords: Activated carbon; Nitrogen doping; Titanium dioxide; Anions; Aqueous matrix species; Solar photocatalysis

Mesoporous-molecular-sieve-supported nickel sorbents for adsorptive desulfurization of commercial ultra-low-sulfur diesel fuel by Cigdem Sentorun-Shalaby; Shyamal Kumar Saha; Xiaoliang Ma; Chunshan Song (pp. 718-726).

Display Omitted▶ MCM-48 improves the dispersion of Ni in sorbent, and increases its ADS capacity. ▶ Incipient wetness impregnation with ultrasonic aid improves the dispersion of Ni. ▶ Sulfur in commercial diesel can be removed to <1ppmw on Ni20/MCM-48 sorbent. ▶ The reactivity of alkyl DBTs is dependent on both number and size of the alkyl groups.A high-performance nickel-based sorbent was developed by loading nickel on a mesoporous molecular sieve, MCM-48, for adsorptive desulfurization (ADS) of commercial ultra low sulfur diesel (ULSD) for fuel cell applications. The prepared sorbents were characterized by the N₂ adsorption–desorption, X-ray diffraction (XRD), H₂ chemisorption, and transmission electron microscope (TEM), and the ADS performance was evaluated in a fixed-bed flow sorption system at 220°C using a commercial ULSD with a sulfur content of 14.5ppmw. Effects of the ultrasonic aid in incipient wetness impregnation (IWI), nickel loading amount and support materials on the sorbent performance were examined. It was found that the incipient wetness impregnation with the ultrasonic aid improved significantly the ADS performance of the sorbent by increasing the dispersion of nickel on the surface. Using MCM-48 as a support with 20wt% nickel loading (Ni20/MCM-48) can lead to an excellent nickel-based sorbent with a breakthrough capacity of 2.1mg-S/g-sorb for ADS of the ULSD at a breakthrough sulfur level of 1ppmw. The alkyl dibenzothiophenes are likely adsorbed on the sorbent surface directly through an interaction between the sulfur atom and the exposed nickel atoms, and a part (∼6%) of the adsorbed alkyl dibenzothiophenes react further with the surface nickel to release the corresponding hydrocarbons. The desulfurization reactivity of the alkyl dibenzothiophenes is dependent on not only the number, but also the size of the alkyl substituents at the 4- and 6-positions of alkyl dibenzothiophenes.

Keywords: Desulfurization; Adsorption; Diesel; Dibenzothiophene; Mesoporous silica; Nickel

Effect of catalysts acidity on residues hydrotreatment by João Marques; Denis Guillaume; Isabelle Merdrignac; Didier Espinat; Sylvette Brunet (pp. 727-737).

Display Omitted▶ Catalysts acidity enhances residues hydrotreatment performances. ▶ HDS, HDN, HDV, HDNi, and asphaltenes conversion are enhanced. ▶ HDT catalysts performances improvement is attributed to strong Brønsted acid sites. ▶ No supplemental coke is obtained if a strong hydrogenating activity is present.The impact of hydrotreatment catalysts acid properties in residues hydrotreatment activities (hydrodemetallization (HDM), hydrodesulfurization (HDS), hydrodeasphaltenization (HDAsC₇), hydrodenitrogenation (HDN) and Conradson carbon conversion (HDCCR)) was evaluated. NiMoP based catalysts carried on multimodal/bimodal alumina were used. Within this framework, the acid properties of alumina carriers were modified (in terms of nature, number and strength of acid sites) in a wide range of acidity. This was achieved by doping the carriers using different additives (fluorine, SiO₂, zeolite) at different contents introduced by impregnation (for F and SiO₂) or co-mixing (for SiO₂ and zeolite).Acidity additives effect on sulfide active phase was followed by means of a toluene hydrogenation catalytic test (to characterize the hydrogenating function), transmission electron microscopy and infrared spectroscopy using CO as probe molecule. Sulfided catalysts acidity was quantified through a cyclohexane isomerization catalytic test. The distribution of Brønsted and Lewis acid sites were distinguished by infrared spectroscopy using respectively lutidine and pyridine as probe molecules.It was shown that only fluorine introduced after the active metals impregnation, allowed to develop the most enhanced Brønsted acidity without a major impact in the active phase.A catalytic test was performed in a lab scale batch reactor at hydrotreatment conditions and using a Safaniya vacuum residue feedstock. Hydrotreatment functions were followed showing that among the acidity additives that were used, fluorine enhanced most the asphaltenes conversion. This was attributed to the higher number of strong Brønsted acid sites.

Keywords: Hydrotreatment; Residues; Catalyst; Acidity; NiMoP/Al2O3; Asphaltenes

Effects of promotion of TiO₂ with alkaline earth metals on the chemisorptive properties and water–gas shift activity of supported platinum catalysts by Paraskevi Panagiotopoulou; Dimitris I. Kondarides (pp. 738-746).

Display Omitted▶ WGS activity of Pt/TiO₂ is affected by the presence of alkaline earth promoters. ▶ Activity depends on the nature and loading of the promoter. ▶ TOF of Pt/TiO₂( x%CaO) goes through a maximum for catalyst loaded with 2% CaO. ▶ Optimized catalyst is very active and stable under realistic reaction conditions.The effects of promotion of TiO₂ with Group II alkaline earth metals on the chemisorptive properties and water–gas shift (WGS) activity of dispersed platinum have been investigated over Pt/TiO₂( x%MO) catalysts of variable promoter type (M=Mg, Ca, Sr, Ba) and loading ( x=0–4wt.%). DRIFTS experiments carried out using CO as a probe molecule showed that the presence of calcium does not affect appreciably adsorption on sites located on the surface of Pt crystallites, but results in the development of new, low-frequency bands in the ν(CO) region attributed to the creation and population of sites with increased electron density located at the metal–support interface. Results of H₂-TPD experiments indicated a weakening of the adsorption strength of these sites toward hydrogen with increasing CaO content. Catalytic performance tests and kinetic measurements showed that activity of alkaline earth metal-promoted catalysts depends appreciably on the nature and loading of the promoter, as well as on the calcination temperature employed for the preparation of doped TiO₂ supports. Optimal results were obtained for Pt catalyst supported on TiO₂ promoted with 1–2wt.% CaO, the specific activity of which is 2–3 times higher, compared to that of the unpromoted catalyst. Optimized catalysts are characterized by increased activity and excellent stability under realistic reaction conditions and may be used efficiently in practical applications, provided that promoter loading, calcination temperature and operating conditions are properly selected.

Keywords: Water–gas shift; Noble metal; Platinum; Titanium dioxide; Alkaline earth; Promotion; TPD; FTIR; Kinetic measurements; Stability

Corrigendum to “Assessing optimal photoactivity on titania nanotubes using different annealing temperatures” [Appl. Catal. B: Environ. 100 (1–2) (2010) 47–54] by J.A. Toledo-Antonio; M.A. Cortes-Jacome; S.L. Orozco-Cerros; E. Montiel-Palacios; R. Suarez-Parra; C. Angeles-Chavez; J. Navarete; E. López-Salinas (pp. 747-747).

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Applied Catalysis B, Environmental (v.101, #3-4)