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Applied Catalysis B, Environmental (v.117-118, #)

Editorial Board (pp. co2).

Contents (pp. co4).

Editorial Board (pp. i).

Contents Continued (pp. i).

Plasma assisted heterogeneous catalytic oxidation: HCCI Diesel engine investigations by Michael J. Kirkpatrick; Emmanuel Odic; Stéphane Zinola; Jacques Lavy (pp. 1-9).

Display Omitted► Non-thermal plasma was used to assist a Diesel oxidation catalyst in two different engine regimes. ► Two modes of plasma were investigated: direct in-line upstream and ozone injection. ► Thermal effects were observed for in-line and heterogeneous reactions for ozone injection. ► Ozone injection mode presents certain advantages, including lower investment costs.A significant augmentation of the oxidation rate of carbon monoxide and unburned hydrocarbons has been previously demonstrated when the two processes of atmospheric pressure dielectric barrier discharge and Diesel oxidation catalysis were used simultaneously. In the case of carbon monoxide oxidation, the rate increase was attributed to a heterogeneous reaction of ozone with carbon monoxide. Ozone injection is investigated along with the direct application of the plasma to the gas upstream of a Diesel oxidation catalyst on a Diesel engine test bench. When used on the Diesel engine exhaust in steady state conditions, depending on the engine regime, the two processes had different effects on the gas composition. Both processes induced heating of the catalyst: while the plasma treatment of the entire gas flux heated the gas itself, and therefore also heated the catalyst, the injection of ozone heated the catalyst solely through the heat of reaction of ozone with the adsorbed species. Mechanisms for these effects are proposed and the performance of each approach is discussed in terms of energy cost and technical feasibility.

Keywords: Diesel oxidation catalysis; Non-thermal plasma; Ozone; Unburned hydrocarbons; Carbon monoxide

Remediation of PAH-contaminated soils by magnetite catalyzed Fenton-like oxidation by M. Usman; P. Faure; C. Ruby; K. Hanna (pp. 10-17).

Degradation of fluorenone (spiked on sand) during oxidation experiments at circumneutral pH.Display Omitted► Magnetite was effective to catalyze chemical oxidation of PAHs at neutral pH. ► Soluble Fe^II was unable to act as catalyst in soil. ► Significant abatement of PAHs was obtained by Fenton-like oxidation. ► Soil matrix and PAHs availability affect PAH degradation efficiency. ► No toxic by-products were observed during Fenton-like oxidation.This is the premier study reporting the degradation of polycyclic aromatic hydrocarbons (PAHs) through Fenton-like oxidation catalyzed by magnetite. Kinetic degradation of PAHs was studied at circumneutral pH by treatments: (i) H₂O₂+soluble Fe^II (F), (ii) H₂O₂+magnetite as iron source (FL) and (iii) H₂O₂ alone without catalyst (HP). Results show that oxidation of a model PAH compound (fluorenone) spiked on sand resulted in its complete removal by FL treatment but degradation did not exceed 20% in HP or F systems. However, in two PAHs polluted soils (sampled from coking plant sites), negligible oxidation of 16 PAHs was observed regardless of the catalyst used: soluble Fe^II or magnetite. Then organic extract separated from these soils was added to sand and after evaporation of the solvent, oxidation was performed which resulted in more than 90% of PAHs removal by FL as compared to 15% by F or HP systems. These removal extents decreased by a factor of two when the organic extracts were oxidized in the presence of original soil. PAHs degradation extent was improved in soils pre-treated with availability-enhancement agents such as ethanol or cyclodextrin. Degradation was non-selective and no by-products were observed by GC–MS and μFTIR. Treatment efficiency was highly limited by PAHs availability in soils and the soil matrix effect. This study points out the promising efficiency of magnetite for PAHs oxidation at circumneutral pH over soluble Fe^II in contaminated soils, and has important implications in the remediation of contaminated soils.

Keywords: Soil; Polycyclic aromatic hydrocarbons; Fenton; Magnetite; Oxidation

Efficient conversion of 1,2-dichlorobenzene to mucochloric acid with ozonation catalyzed by V₂O₅ loaded metal oxides by Estelle C. Chetty; Venkat B. Dasireddy; Suresh Maddila; S.B. Jonnalagadda (pp. 18-28).

Display Omitted► Conversion of 1,2-dichlobenzene to mucochloric acid (MCA) by O₃ in water. ► V₂O₅ on metal oxide catalysts showed (98–100%) selectivity to MCA. ► Conversion efficiency of the supports was SiO₂>Al₂O₃>TiO₂. ► Efficiency of 5% V₂O₅ loaded catalysts greater than 1% loaded.Ozone initiated oxidation of 1,2-dichlorobenzene (DCB) in aqueous system catalyzed by different loadings of V₂O₅ supported on metal oxides namely; Al₂O₃, SiO₂ and TiO₂ was investigated. Catalyst materials were characterized by different surface techniques including BET, TPD, SEM, FT-IR, ICP, and XRD methods. Mucochloric acid (MCA) was identified to be main oxidation product. The conversion and selectivity of MCA were compared. With 5% V₂O₅, all three supports gave 100% conversion and 100% selectivity after 5h ozonation. Conversion efficiency of the support was SiO₂>Al₂O₃>TiO₂ for 2h ozonation duration and 5% V₂O₅ loaded catalysts registered higher conversions than with 1% loaded. Probable reaction scheme is described.

Keywords: Dichlorobenzene; Ozone; Vanadium pentoxide loaded; Alumina; Silica; Titania; Mucochloric acid

Modified niobia as a bifunctional catalyst for simultaneous dehydration and oxidation of glycerol by Luiz C.A. Oliveira; Marcio F. Portilho; Adilson C. Silva; Hosane A. Taroco; Patterson P. Souza (pp. 29-35).

Display Omitted► Synthetic niobia highly active was obtained by the generation of peroxo groups after treatment with H₂O₂. ► The mass spectrometry showed that ether was mainly produced. ► The catalytic activity of modified niobia was maintained for three reaction cycles.The niobia (Nb₂O₅) obtained in this study was modified by pretreatment with hydrogen peroxide to produce a bifunctional catalyst (Nb₂O₅//H₂O₂) with both acidic and oxidizing properties. The oxidizing properties of niobia were obtained by the generation of peroxo groups on the catalyst surface. The catalytic conversion of glycerin showed high activity using H₂O₂ as the oxidant. The catalytic tests monitored by mass spectrometry (ESI-MS) suggested the formation of ethers obtained by the condensation of glycerol ( m/z=167, 223, 240). Furthermore, it was observed that the modification of the catalyst directs the formation of larger molecules such as triglycerol compared to niobia without pretreatment with H₂O₂.

Keywords: Niobia; Glycerol; Dehydration; Oxidation

Highly active catalysts for the photooxidation of organic compounds by deposition of [60] fullerene onto the MCM-41 surface: A green approach for the synthesis of fine chemicals by John Kyriakopoulos; Manolis D. Tzirakis; George D. Panagiotou; Mariza N. Alberti; Kostas S. Triantafyllidis; Sofia Giannakaki; Kyriakos Bourikas; Christos Kordulis; Michael Orfanopoulos; Alexis Lycourghiotis (pp. 36-48).

Display Omitted► Successive incipient wetness impregnation is an efficient method for dispersing effectively C₆₀ on MCM-41. ► C₆₀ is highly dispersed on MCM-41 due to its high surface area. ► The 6wt.% C₆₀/MCM-41 catalyst is the most active in the photooxidation of organic compounds. ► C₆₀/MCM-41 catalysts retain the advantages of homogeneous and heterogeneous catalysis.A series of C₆₀ catalysts supported on MCM-41 was prepared in the context of developing a highly active heterogeneous catalytic system for the singlet oxygen-mediated oxidation of organic substrates. Successive incipient wetness impregnation was used for preparing 3, 6, 9 and 12wt.% C₆₀ onto MCM-41 surface. N₂ adsorption, FT-IR, XRD, HR-TEM, DRS and TGA, have been used to characterize the photocatalysts.It was found that C₆₀ is highly dispersed (especially in the 3 and 6wt.% C₆₀ catalysts) within the mesopores or on the external surface of MCM-41, as clusters or crystallites/aggregates of very small size and presumably in the form of atomic layers. The mesoporous structure and characteristics (surface area, mesopore size and volume) of MCM-41 remain almost intact upon deposition of C₆₀ on its surface.The photocatalytic activity was assessed in the photocatalytic oxidation of olefins via the singlet oxygen ene reaction by studying the photooxygenation of 2-methyl-2-heptene as a probe reaction. The catalytic tests were carried out at 0–5°C in CH₃CN under oxygen atmosphere and using a 300W xenon lamp as the light source. To investigate further the potential applications of our catalysts we examined various types of photooxidations including the [4+2] or [2+2] cycloaddition, the heteroatom oxidation with sulfur or phosphorus containing compounds and the oxidation of phenols.The heterogeneous photocatalysts obtained were proved to be very active exhibiting higher substrate conversion, TON and TOF values, compared to those of the unsupported (solid) C₆₀ and the corresponding photocatalysts supported on silica or γ-alumina. This was mainly attributed to the better dispersion of C₆₀ on the MCM-41. The conversion achieved over the catalysts increases with the amount of the supported C₆₀ up to a value of 6wt.% and then it decreases whereas the TON and TOF values decrease monotonically as the amount of the supported C₆₀ increases following the increase in the size of the supported C₆₀ crystallites/aggregates. Shadow effects were not observed under our experimental conditions.

Keywords: C; ₆₀; Photocatalysis; Singlet oxygen; Photooxidation; Supported catalysts; C; ₆₀; /MCM-41

Sulfur poisoning and regeneration of the Ag/γ-Al₂O₃ catalyst for H₂-assisted SCR of NO_x by ammonia by Dmitry E. Doronkin; Tuhin Suvra Khan; Thomas Bligaard; Sebastian Fogel; Pär Gabrielsson; Søren Dahl (pp. 49-58).

Display Omitted► SO₂ tolerance testing protocol is developed for NO_x SCR catalysts. ► Catalyst lifecycle in automotive application is modeled in the test setup. ► Ag/Al₂O₃ can be regenerated from sulfur under DPF regeneration conditions. ► Al₂O₃ contain two types of active sites with different regeneration capabilities.Sulfur poisoning and regeneration mechanisms for a 2% Ag/γ-Al₂O₃ catalyst for the H₂-assisted selective catalytic reduction of NO_x by NH₃ are investigated. The catalyst has medium sulfur tolerance at low temperatures, however a good capability of regeneration at 670°C under lean conditions when H₂ is present. These heating conditions can easily be established during soot filter regeneration. Furthermore, two types of active sites could be identified with different regeneration capabilities, namely finely dispersed Ag and larger Ag nanoparticles. The most active sites are associated with the finely dispersed Ag. These sites are irreversibly poisoned and cannot be regenerated under driving conditions. On the other hand the larger Ag nanoparticles are reversibly poisoned by direct SO_x adsorption. The interpretation of the data is supported by DFT calculations.

Keywords: Ag/Al; ₂; O; ₃; SO; ₂; NO; _x; SCR; Poisoning; Regeneration

Hydrothermal synthesis of BiVO₄: Structural and morphological influence on the photocatalytic activity by S. Obregón; A. Caballero; G. Colón (pp. 59-66).

Display Omitted► By a simple hydrothermal method we achieve the BiVO₄ photoactive monoclinic phase. ► Best performances were not associated to the surface area values. ► Photoactivity is strongly affected by the crystallite size and morphology. ► Better photocatalytic performances have been obtained for needle-like m-BiVO₄. ► Irradiation with low power sunlike lamp leads to notably photodegradation of MB.BiVO₄ hierarchical heterostructures are synthesized by means of a surfactant free hydrothermal method having good photoactivities for the degradation of methylene blue under UV–vis irradiation. From the structural and morphological characterization it has been stated that BiVO₄ present the monoclinic crystalline phase with different morphologies depending on the pH value, type of precipitating agent and hydrothermal temperature and treatment time. The best photocatalytic performance was attained for the samples with needle-like morphology.

Keywords: Hydrothermal; BiVO; ₄; Photocatalysis; Methylene blue

Mesoporous PdO–TiO₂ nanocomposites with enhanced photocatalytic activity by Adel A. Ismail (pp. 67-72).

Display Omitted► Mesoporous PdO–TiO₂ nanocomposites have been achieved. ► Addition of PdO into TiO₂ enhanced the photoactivity of TiO₂. ► PdO–TiO₂ nanocomposites showed a more effective ∼4 times than TiO₂-P25. ► Photonic efficiency mesosporous PdO–TiO₂ nanocomposites is ξ=19.5%. ► This ξ value is found to be among the highest reported up to now.Herein, we report a synthesis of mesoporous PdO–TiO₂ nanocomposites at different PdO (0–3wt%) through simple one-step sol–gel reactions. Pd²⁺ ions have been immobilized into TiO₂ networks by cross-linking triblock copolymer (Pluronic F123) as the structure-directing agents to develop highly efficient PdO–TiO₂ photocatalyst. The produced PdO–TiO₂ gel were calcined at 400°C for 4h to remove organic materials. TiO₂ nanoparticles with an average diameter are 8–10nm and PdO nanoparticles are well dispersed and exhibit diameters of about 10–40nm based on the PdO content. Our prepared photocatalysts have been compared with Pd/Aeroxide TiO₂-P25 by the determination of the initial rate of HCHO formation generated by the photooxidation of CH₃OH in aqueous suspensions to calculate the corresponding photonic efficiencies. The newly prepared PdO–TiO₂ nanocomposites showed a more effective and high efficient photocatalytic activities for CH₃OH oxidation to HCHO ∼4 and 2 times than TiO₂-P25 and Pd/TiO₂-P25 respectively. In the present work, the photocatalytic activities of the obtained PdO–TiO₂ nanocomposites were significantly higher than those of previously reported. To the best of our knowledge, the measured photonic efficiency ξ=19.5% of mesosporous PdO–TiO₂ nanocomposites is found to be among the highest ξ-values reported up to now.

Keywords: Mesoporous; PdO–TiO; ₂; Nanocomposites; Photocatalytic; Oxidation; Methanol

Fe–Ti spinel for the selective catalytic reduction of NO with NH₃: Mechanism and structure–activity relationship by Shijian Yang; Junhua Li; Chizhong Wang; Jinghuan Chen; Lei Ma; Huazhen Chang; Liang Chen; Yue peng; Naiqiang Yan (pp. 73-80).

Display Omitted► (Fe₂Ti)_0.8O₄ showed an excellent SCR performance at 300–400°C. ► The SCR reaction through the L–H mechanism was restrained due to Ti incorporation. ► The SCR reaction over Fe–Ti spinel mainly followed the E–R mechanism. ► The SCR reaction through the E–R mechanism was promoted due to Ti incorporation.A series of non-stoichiometric Fe–Ti spinel (Fe3−_xTi_x)1−_δO₄ were synthesized using a co-precipitation method and then developed as environmental-friendly and low cost catalysts for the selective catalytic reduction (SCR) of NO with NH₃. As Ti was incorporated into γ-Fe₂O₃, the SCR reaction over (Fe3−_xTi_x)1−_δO₄ through the Langmuir–Hinshelwood mechanism was restrained. Therefore, the SCR activity of (Fe3−_xTi_x)1−_δO₄ ( x≠0) was less than that of γ-Fe₂O₃ at 150–250°C. However, the SCR reaction over (Fe3−_xTi_x)1−_δO₄ through the Eley–Rideal mechanism was promoted due to the incorporation of Ti. The SCR activity of (Fe3−_xTi_x)1−_δO₄ ( x≠0) was mainly related to the oxidative ability of Fe³⁺ cation on the surface, the concentration of NH₃ adsorbed on the surface and the concentration of reducible Fe³⁺ cation on the surface. Although the oxidative ability of Fe³⁺ cation on the surface decreased due to the incorporation of Ti into γ-Fe₂O₃, the concentration of NH₃ adsorbed on the surface and the concentration of reducible Fe³⁺ cation on the surface both increased. As a result, (Fe₂Ti)_0.8O₄ showed excellent activity, selectivity, and H₂O/SO₂ durability for the SCR reaction at 300–400°C.

Keywords: (Fe; 3−; _x; Ti; _x; ); 1−; _δ; O; ₄; DRIFTS; Structure–activity relationship; Mechanism; Kinetic analysis

Low-temperature conversion of phenol into CO, CO₂ and H₂ by steam reforming over La-containing supported Rh catalysts by Domna A. Constantinou; M. Consuelo Álvarez-Galván; José Luis G. Fierro; Angelos M. Efstathiou (pp. 81-95).

Display Omitted► La³⁺ introduction in Ce–Zr–O promotes phenol steam reforming on supported Rh. ► La³⁺ introduction in Ce–Zr–O promotes Rh dispersion when used as support of Rh. ► La³⁺ introduction in Ce–Zr–O promotes labile oxygen concentration and mobility. ► Rh/Ce–Zr–La–O remarkably hinders lowering of WGSR rate when H₂ is present.The steam reforming of phenol in the low-temperature range of 350–550°C was studied over 0.5wt% Rh supported on Ce_0.15Zr_0.85O₂, Zr_0.93La_0.07O₂, and Ce_0.13Zr_0.83La_0.04O₂ mixed metal oxides. The reforming specific activity (per gram of catalyst basis) was found to depend on (a) Rh dispersion, (b) the concentration (μmolg⁻¹) of labile oxygen species of support, as determined by “oxygen storage capacity” measurements, and (c) the promotion of the water–gas shift (WGS) reaction rate, all of which largely influenced by the support chemical composition. The addition of 4atom% La³⁺ into the Ce_0.15Zr_0.85O₂ crystal structure was found to largely promote the dispersion of Rh, to increase significantly (by a factor of 1.75) the concentration of surface basic sites (μmolm⁻²) of Ce_0.13Zr_0.83La_0.04O₂ compared to Ce_0.15Zr_0.85O₂ support, to prevent to a large extent the inhibiting role of hydrogen in the rate of WGS reaction, and to influence significantly the concentration and structure of surface reaction intermediates of the WGS, namely: formate (HCOO–) and –OH groups formed on the support, and adsorbed CO formed on the Rh metal. The 0.5wt% Rh/Ce_0.13Zr_0.83La_0.04O₂ catalyst led to a significantly better performance towards steam reforming of phenol in terms of phenol conversion, H₂-yield, and CO/CO₂ product ratio in the 350–450°C range compared to a commercial Ni-based catalyst (44wt% Ni) used for steam reforming reactions. At 400°C, the 0.5wt% Rh/Ce_0.13Zr_0.83La_0.04O₂ catalyst exhibited approximately 54% and 50%, respectively, higher phenol conversion and hydrogen yield, compared to the Ni-based industrial catalyst. The significantly lower CO/CO₂ product ratio obtained in the case of Rh/Ce_0.13Zr_0.83La_0.04O₂ compared to that obtained in the other supported-Rh catalysts is in agreement with the higher kinetic rate for the WGS reaction observed in the former catalyst.

Keywords: Phenol steam reforming; Hydrogen production; Supported-Rh catalysts; HRTEM; XPS; CO; ₂; -TPD; CO-TPD; CO; ₂; -DRIFTS; H; ₂; O-DRIFTS; Operando; DRIFTS-mass spectrometry WGS

Photocatalytic degradation of olanzapine in aqueous and river waters suspension of titanium dioxide by Elżbieta Regulska; Joanna Karpińska (pp. 96-104).

Display Omitted► The photostability of olanzapine was investigated. ► Two irradiation sources were applied. ► Olanzapine was found to undergo a complete decomposition. ► A simple and promising way of olanzapine removal from river waters was presented.The photostability of olanzapine, recently most commonly used atypical antipsychotic agent, was investigated. Two irradiation sources were applied, namely solar simulated light ( E=250 and 500W/m²) and monochromatic ultraviolet light ( λ=254 and 366). The olanzapine adsorption on a titanium dioxide surface was confirmed by differential scanning calorimetry and infrared spectroscopy. Kinetic studies were performed on a basis of a spectrophotometric method. Degradation efficiency was assessed by applying high performance liquid chromatography with an ultraviolet detection. HPLC analysis did not show any degradation products. Olanzapine was found to degrade under photocatalytic conditions with the creation of low molecular products. Disappearance of olanzapine from titanium dioxide surface after degradation was confirmed by IR spectra. A simple and promising way to apply the photocatalytic removal of olanzapine in titanium dioxide suspension was presented.

Keywords: Heterogeneous photocatalysis; Photodegradation; Titanium dioxide; Olanzapine

Catalytic hydrotreatment of fast-pyrolysis oil using non-sulfided bimetallic Ni-Cu catalysts on a δ-Al₂O₃ support by A.R. Ardiyanti; S.A. Khromova; R.H. Venderbosch; V.A. Yakovlev; H.J. Heeres (pp. 105-117).

Display Omitted► Ni-Cu catalysts are active catalysts for fast pyrolysis oil hydrotreatment. ► Synergic effects were observed compared to the monometallic catalysts. ► The catalysts are interesting alternatives for expensive noble metal catalysts. ► Product properties of the upgraded oils are better than the pyrolysis oil feed.Fast pyrolysis oil from lignocellulosic biomass is an attractive energy carrier. However, to improve the product characteristics such as a reduced polarity and higher thermal stability, upgrading is required. We here report activities on the catalytic hydrotreatment of fast pyrolysis oil using bimetallic NiCu/δ-Al₂O₃ catalysts with various Ni/Cu ratios (0.32 to 8.1 w/w) at a fixed total metal intake of about 20wt% with the objective to improve product properties for co-feeding applications in conventional oil refineries. Hydrotreatment reactions were initially carried out for a model compound (anisole, continuous set-up, 300°C, 10bar) and subsequently for fast pyrolysis oil (batch autoclave, 1h at 150°C followed by 3h at 350°C, at 100bar initial pressure). Best results, i.e. the highest hydrodeoxygenation yield for experiments with anisole (75mol%), and an upgraded oil with the most favorable properties for fast pyrolysis oil (high H/C ratio, low M_w of 500g/mol, low thermogravimetric residue of 6.8wt%), were obtained for a catalyst with a Ni to Cu wt% ratio of eight (16Ni2Cu). For this catalyst, hydrogen consumption was the highest (146NL/kg_PO). The findings were rationalized using a reaction network model earlier developed for Ru/C. Analysis of catalyst (ICP, HRTEM, XRD and TGA) before and after reaction showed the occurrence of leaching of both active metals (Ni and Cu) and support, as well as coke deposition on the support. The most active catalyst in the series (16Ni2Cu) also gave lowest leaching and coking levels in the series.

Keywords: Hydrotreatment; Hydrodeoxygenation; Fast pyrolysis oil; Bio-oil; Anisole; Nickel catalyst; Characterization; Bimetallic nickel-copper catalysts

Development of attapulgite/Ce1−_xZr_xO₂ nanocomposite as catalyst for the degradation of methylene blue by Xiazhang Li; Chaoying Ni; Chao Yao; Zhigang Chen (pp. 118-124).

.Display Omitted► Ce1−_xZr_xO₂ and attapulgite (ATP) interact and evolve as a function of loading and molar fraction x. ► Catalytic oxidation property of ATP/Ce1−_xZr_xO₂ is superior to either ATP or ATP/CeO₂. ► Molar fraction x in ATP/Ce1−_xZr_xO₂ has significant impact on the degradation of methylene blue. ► A remarkable 99% decomposition of methylene blue is achieved in 240min when x=0.2 ► A mechanism is proposed for the generation of OH.Novel attapulgite (ATP)/Ce1−_xZr_xO₂ nanocomposite was prepared by a facile homogeneous deposition method using hexamethylenetetramine as precipitator. The catalytic activity of ATP/Ce1−_xZr_xO₂ was investigated by oxygenating methylene blue dye wastewater using O₃ as oxidant. HRTEM, XRD, FT-IR, Raman and H₂-TPR data reveal significant interactions between CeZrO oxides and ATP support, the evolution of textural, structural and oxidation state as a function of the composition, and the formation of more oxygen vacancies in Ce1−_xZr_xO₂. The molar fraction of Zr⁴⁺ demonstrates considerable influence on the degradation rate of the methylene blue. Compared with pure ATP and ATP/CeO_2, the ATP/Ce1−_xZr_xO₂ composite remarkably enhances catalytic activity, and a maximum degradation rate of methylene blue at 99% is achieved when the molar fraction x is 0.2.

Keywords: Attapulgite; Cerium oxide; Methylene blue; Catalytic activity

Catalytic oxidation of VOCs over mixed Co–Mn oxides by Zhen-Yu Tian; Patrick Hervé Tchoua Ngamou; Vincent Vannier; Katharina Kohse-Höinghaus; Naoufal Bahlawane (pp. 125-134).

Display Omitted► Binary spinel-type oxides were synthesized by pulsed spray evaporation (PSE) CVD process. ► The doping effect was evaluated in terms of chemical components and redox properties. ► The solids promote the thermal stability and catalytic activity. ► The Co–Mn oxides suppress the formation of intermediates and favor the selectivity toward CO₂ at low temperatures. ► The enhanced catalytic activity benefited from the abundant presence of oxygen vacancies.This work reports the synthesis and characterization of single-phase cobalt manganese oxide (CMO) spinels Co3−_xMn_xO₄ (0≤ x≤0.34) prepared by the pulsed-spray evaporation chemical vapor deposition (PSE–CVD) method. Structure and cationic distribution of the obtained films were characterized by XRD, FTIR, XPS and Raman spectroscopy. Temperature-programmed reduction/re-oxidation (TPR/TPO) was used to elucidate the redox properties of the deposited films. The electrical resistivity was measured in the temperature range of 27–450°C. XRD, FTIR and Raman spectra reveal the formation of single-phase cubic spinel structures up to x=0.34. With the substitution of cobalt cations with Mn³⁺ and Mn⁴⁺ ions, the unit cell of the cubic spinel shows a linear increase; the TPR results indicate a lower reducibility while the TPO results display no evident change; also, the ratio Co³⁺/Co²⁺ decreased and both electrical resistivity and thermal stability showed increasing trends. The observed behavior is attributed to the progressive incorporation of manganese, which induces structural defects favoring the formation of anionic vacancies and the restriction of the oxygen mobility. The catalytic activities of the doped spinels were investigated for the deep oxidation of unsaturated hydrocarbons (C₂H₂ and C₃H₆). The introduction of a slight amount of manganese shifted the light-off curves toward lower temperatures. Based on the XPS results, the enhanced catalytic activity is thought to benefit from the abundant presence of oxygen vacancies in the doped oxide.

Keywords: Catalytic oxidation; Cobalt manganese oxide; Spinel; Pulsed-spray evaporation; Chemical vapor deposition

Structure evolution of nanocrystalline Ce1−_xPd_xO2−_y mixed oxide in oxidizing and reducing atmosphere: Reduction-induced activity in low-temperature CO oxidation by M. Kurnatowska; L. Kepinski; W. Mista (pp. 135-147).

Display Omitted► Thermally stable, nanocrystalline Ce1−_xPd_xO2−_y oxide with x up to 0.2 was obtained by microemulsion method. ► Reversible extraction–dissolution of Pd occurs during successive reduction–oxidation cycles at 500°C. ► Reduction treatment in H₂ at 400°C enhances activity of Ce1−_xPd_xO2−_y in low-temperature CO oxidation.Nanocrystalline (4–8nm) Ce1−_x Pd_x O 2−_y mixed oxide (0< x<0.3), active in low temperature CO oxidation, has been prepared by microemulsion method. Thorough XRD, TEM, SEM-EDS, BET and FT Raman studies revealed that the oxide with x<0.2 is a homogeneous solid solution structurally stable up to 800°C in oxidizing atmosphere. In hydrogen, already at 500°C segregation of Pd particles occurs, which exhibit preferential Pd (111)∥CeO₂ (111) orientation, preserved even after reduction at 800°C. Ce_0.89Pd_0.11O2−_y oxide showed reversible extraction–dissolution of Pd upon successive reduction–oxidation cycles at 500°C, which is an example of “self-regenerative” property important for potential catalytic applications. Doping with Pd strongly hinders the sintering of ceria at high temperatures and enhances its reducibility at low temperatures (below 500°C).“As prepared”, oxidized Ce_0.89Pd_0.11O2−_y sample demonstrates moderate activity in CO oxidation (reaching 85% conversion at ∼250°C) similar to that of 3% Pd/CeO₂ prepared by impregnation. The activity improves dramatically (measurable CO conversion below room temperature and 100% conversion at ∼120°C) after pre-reduction at 400°C in H₂. It appears that partially reduced Pd species, or extremely small particles (<1nm) at the surface of ceria are responsible for the low temperature activity in CO oxidation. Such Pd species could be strongly bonded to the surface, e.g., exhibiting a special epitaxial orientation observed for larger Pd crystallites (∼2nm) formed during reduction at higher temperatures.

Keywords: Ce; Pd; O mixed oxide; Nanocrystalline Pd doped ceria; CO oxidation; Reducibility; TEM

A novel class of heterojunction photocatalysts with highly enhanced visible light photocatalytic performances: yBiO(Cl_xBr1−_x)–(1− y) bismuth oxide hydrate by Sanaa Shenawi-Khalil; Vladimir Uvarov; Sveta Fronton; Inna Popov; Yoel Sasson (pp. 148-155).

Display Omitted► Synthesis of new visible light sensitive photocatalysts based on heterojunction of BiOCl_xBr1−_x–bismuth oxyhydrate. ► Effective separation of photoexcited electrons and holes. ► 14.6 times higher photocatalytic activity compared to TiO₂. ► Research of relationship between photocatalytic properties and chemistry and structure of photocatalyst.A novel class of heterojunctioned bismuth oxyhalide photocatalysts yBiO(Cl_xBr1−_x)–(1− y)BHO (bismuth oxide hydrate) has been prepared by a simple hydrothermal method. The new materials are highly efficient under visible light irradiation ( λ≥420nm) for the degradation of Rhodamine B (RhB), Acetophenone (AP) and photooxidation of iodide. Even though BHO shows very low photocatalytic efficiency, its combination with BiO(Cl_0.5Br_0.5) provides exceptional high photocatalytic activity due to more effective photo-excited electron–hole separation by the heterojunction semiconductor. The relationship between BHO amounts and the photocatalytic activities was investigated. Compared to Degussa P25 the composite with x=0.5 and y=0.9 demonstrated 14.6 times higher activity in removing aqueous RhB under visible light irradiation. The possible photodegradation mechanism was studied by the examination of different active species through adding appropriate scavengers. Furthermore, the photogenerated charge transfer process was proposed based on the bands positions of BiO(Cl_0.5Br_0.5) and BHO. After five cycles, the catalyst did not exhibit any significant loss of photocatalytic activity, confirming the photocatalyst is essentially stable. The excellent activity and photostability reveal that yBiO(Cl_xBr1−_x)–(1− y)BHO is a promising visible-light-responsive photocatalyst.

Keywords: Visible light photocatalysis; Heterojunction; Bismuth oxyhydrate; Bismuth hydrate oxide; Bismuth oxyhalide

Structural investigation of LaCoO₃ and LaCoCuO₃ perovskite-type oxides and the effect of Cu on coke deposition in the partial oxidation of methane by Fabio Souza Toniolo; Robert Newton S.H. Magalhães; Carlos André C. Perez; Martin Schmal (pp. 156-166).

Display Omitted► Preparation of perovskite-type LaCoO₃ and LaCoCuO₃ catalysts. ► Dynamic structural transformation of the perovskite. ► LaCoCuO₃ perovskite showed better performance in the partial oxidation of methane. ► Copper had significant effect against carbon deposition on the catalyst. ► High activity to syngas for LaCoO₃ catalyst with formation of carbon filaments.LaCoO₃ and LaCo_0.8Cu_0.2O₃ perovskite-type oxides prepared by the polymerizable complex route were obtained as single phase and investigated in the partial oxidation of methane through temperature-programmed surface reactions (TPSR). Characterizations were carried out before and after the reactions under different feed streams CH₄/O₂/He=2/1/37 and 5/1/64, and revealed a dynamic structural transformation in which the perovskite is collapsed towards lanthanum-based matrix and metal cobalt and copper. The copper-substituted perovskite showed better performance in the partial oxidation of methane leading to higher CH₄ conversion and higher syngas production than LaCoO₃ during the transient reaction. Furthermore, copper had significant effect against carbon deposition on the catalyst and it is suggested to be a very important dopant for perovskites applied in reactions with hydrocarbons.

Keywords: Perovskite; Partial oxidation; Copper; Coke inhibition; Methane

Sulfate storage and stability on representative commercial lean NO_x trap components by Nathan A. Ottinger; Todd J. Toops; Josh A. Pihl; Justin T. Roop; Jae-Soon Choi; William P. Partridge (pp. 167-176).

Display Omitted► Supporting Ba on ceria–zirconia rather than alumina decreases the sulfate stability. ► Oxygen storage in ceria–zirconia impacts sulfur distribution during cycling. ► Pt proximal to sulfate sites not essential for sulfation or desulfation. ► MgAl₂O₄ can store sulfur in physical mixtures and may protect Ba-phase.Components found in a commercial lean NO_x trap have been studied in order to determine their impact on sulfate storage and release. A micro-reactor and a diffuse reflectance infrared Fourier transform spectrometer (DRIFTS) were used to compare components MgAl₂O₄, Pt/MgAl₂O₄, Pt/Al₂O₃, Pt/Ba/Al₂O₃, Pt/CeO₂–ZrO₂, and Pt/Ba/CeO₂–ZrO₂, as well as physical mixtures of Pt/Al₂O₃+MgAl₂O₄ and Pt/Ba/CeO₂–ZrO₂+MgAl₂O₄. Desulfation temperature profiles as well as DRIFTS NO_x and SO_x storage spectra are presented for all components. This systematic approach highlighted the ability of the underlying support to impact sulfate stability, in particular when Ba was supported on ceria–zirconia rather than alumina the desulfation temperature decreased by 60–120°C. A conceptual model of sulfation progression on the ceria–zirconia support is proposed that explains the high uptake of sulfur and low temperature release when it is employed. It was also determined that the close proximity of platinum is not necessary for much of the sulfation and desulfation chemistry that occurs, as physical mixtures with platinum dispersed on only one phase displayed similar behavior to samples with platinum dispersed on both phases.

Keywords: Sulfur; Lean NO; _x; trap; DRIFTS; Ceria–zirconia; MgAl; ₂; O; ₄

Transformations of thiophene compounds under catalytic cracking conditions by Oleg V. Potapenko; Vladimir P. Doronin; Tatyana P. Sorokina; Valentin P. Talsi; Vladimir A. Likholobov (pp. 177-184).

Display Omitted► Reduction of the sulfur content in catalytic cracking gasoline. ► Transformations of various organosulfur compounds in catalytic cracking conditions. ► Different hydrocarbons as hydrogen donors. ► Impact of acid–base properties of the additives to the cracking catalysts on sulfur content reduction.A method for in situ reduction of the sulfur content in catalytic cracking gasoline is reported. A comparison of thermal and catalytic transformations of sulfide and thiophene sulfur is presented. Main transformations of various organosulfur compounds are demonstrated. The effect of [H]-donor activity of hydrocarbons on conversion of thiophene sulfur into hydrogen sulfide is revealed. The impact of acid–base properties of the additives to the cracking catalysts on sulfur content reduction in the liquid products is examined in detail (TPD-NH₃,²⁷Al NMR, CO₂ adsorption). The choice of optimal qualitative composition of a modifying additive for reducing the sulfur content in catalytic cracking gasoline is substantiated.

Keywords: Organosulfur compounds; Thiophene; Catalytic cracking; Hydrogen transfer; Acid–base properties; TPD-NH; ₃; ²⁷; Al NMR; CO; ₂; adsorption

Effect of Cl/Ni molar ratio on the catalytic conversion of polypropylene into Cu–Ni/C composites and their application in catalyzing “Click” reaction by Jiang Gong; Jie Liu; Li Ma; Xin Wen; Xuecheng Chen; Dong Wan; Haiou Yu; Zhiwei Jiang; Ewa Borowiak-Palen; Tao Tang (pp. 185-193).

Display Omitted► Catalytic conversion of polypropylene into Cu–Ni/C composites by Ni₂O₃ and CuCl. ► The yield and morphology of Cu–Ni/C were modulated by Cl/Ni molar ratio. ► Cl/Ni determines the degraded products of polypropylene for growth of CNTs. ► Cu–Ni/C catalyzed “Click” reaction as a heterogeneous catalyst.A one-pot approach to prepare Cu–Ni/C heterogeneous composites by carbonization of polypropylene (PP) using combined catalysts of Ni₂O₃ and CuCl was proposed. TEM, SEM, TGA and Raman measurements were performed to investigate the effects of Cl/Ni molar ratios on the yield and morphology of the resultant carbon materials. The yield of carbon materials in Cu–Ni/C first increased and then decreased as the Cl/Ni molar ratio increased, and the maximum yield was achieved at Cl/Ni molar ratio of 0.125. Longer and thinner carbon nanotubes (CNTs) were obtained at low Cl/Ni ratios while shorter carbon fibers were formed at high Cl/Ni ratios. The effect of Cl/Ni molar ratio on the active sites for the growth of carbon materials and degraded products of PP were investigated by XRD, GC and GC–MS. Interestingly, the resultant Cu–Ni/C showed the catalysis to “Click” reaction. As a result, the initial catalytic substances (Ni₂O₃ and CuCl) could be effectively used twice as catalysts in the carbonization of PP and in the later application of the resultant Cu–Ni/C composites. More importantly, this approach is a new potential method to transform waste polymer materials into valuable metal/carbon heterogeneous composites.

Keywords: Carbon materials; Catalysis; Composites; Polypropylene

A KrCl exciplex flow-through photoreactor for degrading 4-chlorophenol: Experimental and modelling by M. Gomez; M.D. Murcia; J.L. Gomez; E. Gomez; M.F. Maximo; A. Garcia (pp. 194-203).

Display Omitted► KrCl exciplex flow-through photoreactor successfully used to remove 4-chlorophenol. ► Analysis of influence of operational conditions. ► Photo-Fenton process allowed total degradation of substrate and by-products. ► Mechanism and kinetic model for substrate and by-products proposed and validated.A KrCl exciplex flow-through photoreactor has been used for the removal of 4-chlorophenol. UV/H₂O₂ and photo-Fenton processes were tested. Considering the degradation of the different compounds, the molar ratio H₂O₂:4-chlorophenol did not show a significant influence on 4-chlorophenol while an optimum ratio of 25:1 was established for the photoproducts. The presence of the Fenton reagent led to a considerable improvement in the photodegradation of both the substrate and by-products, and an optimum Fe²⁺ concentration of 5mgL⁻¹ was determined. Under these conditions, total degradation was attained for a range of substrate concentrations between 50 and 150mgL⁻¹ and for reaction volumes of 500ml. A photodegradation mechanism was also proposed, based on the formation of two intermediate compounds that quickly degrade to the primary photoproducts previously identified. A kinetic model was developed and theoretical conversion values of the 4-chlorophenol and the photoproducts were compared with the experimental ones, reaching a high degree of agreement ( x_calc=0.9964 x_exp, R²=0.9986) and validating the proposed model. This system simulation using relatively high reaction volumes and including the by-products in the kinetic equations represents a first approach with a view to operating in continuous or semi-continuous systems that allow the scaling up of the process.

Keywords: 4-Chlorophenol; Kinetic model; Photodegradation; UV; Excilamp; KrCl photoreactor

Methanol-tolerant Pd nanocubes for catalyzing oxygen reduction reaction in H₂SO₄ electrolyte by Chien-Liang Lee; Hsueh-Ping Chiou (pp. 204-211).

Display Omitted► Pd nanocubes were successfully used as methanol-tolerant catalysts for acidic oxygen reduction. ► Based on XPS and HRTEM analyses, the surface of the smallest Pd nanocubes was easily oxidized to PdO. ► Despite working in methanol-tolerant solutions, these cubic catalysts have a high activity. ► The greatest activity was occurred on the 48nm nanocube in the methanol electrolyte.New methanol-tolerant catalysts in the form of 27nm, 48nm, and 63nm palladium nanocubes enclosed by {100} facets were successfully used for the oxygen reduction reaction (ORR) in a 0.5M H₂SO_4(aq) solution. Based on X-ray photoelectron spectroscopy and high resolution transmission electron microscopy analyses, the surface of the smallest Pd nanocubes was easily oxidized to PdO. The data provided by the analysis of a mass-transfer-corrected Tafel curve in a free methanol electrolyte showed that the specific activities of the 27nm, 48nm, and 63nm Pd nanocubes at 0.65V (vs. Ag/AgCl) in terms of the kinetic current density ( j_k) were 11.51×10⁻²mAcm⁻², 12.32×10⁻²mAcm⁻², and 10.06×10⁻²mAcm⁻², respectively. In contrast, Pd and Pt nanoparticles featured specific activities of 3.7×10⁻²mAcm⁻² and 13.2×10⁻²mAcm⁻², respectively. Further Tafel analyses conducted using a rotating ring-disk electrode in a methanol electrolyte showed that the j_ks of the 27nm, 48nm, and 63nm Pd nanocubes at 0.65V (vs. Ag/AgCl) were 14.87×10⁻²mAcm⁻², 16.55×10⁻²mAcm⁻², and 12.98×10⁻²mAcm⁻², respectively. The nanocubes have a high activity toward the ORR; the greatest j_k was occurred on the 48nm nanocube even larger than 5.65×10⁻²mAcm⁻², the j_k of the Pd nanoparticles in the methanol electrolyte, where Pt nanoparticles effected methanol oxidation in preference to the ORR. Despite working in methanol-tolerant solutions, the prepared 48nm Pd nanocubes exhibited high electroactivity.

Keywords: Pt nanoparticles; Cathodic catalysts; Crystal face

The SCR of NO with methane over In,H- and Co,In,H-ZSM-5 catalysts: The promotional effect of cobalt by Ferenc Lónyi; Hanna E. Solt; József Valyon; Alicia Boix; Laura B. Gutierrez (pp. 212-223).

Display Omitted► NO-SCR by methane requires two balanced catalytic functions. ► Zeolite Brønsted acid sites catalyze the NO oxidation to NO₂ by O₂ (NO-COX). ► Cobalt-oxide clusters promote the NO-COX activity of H- and In,H-zeolite catalysts. ► N₂-froming reaction (CH₄/NO-SCR) proceeds on Co²⁺/[Co-OH]⁺ or [InO]⁺/[InOH]²⁺ sites. ► Accelerated NO-COX speeds up surface NO₃⁻ formation, methane activation and NO-SCR.Zeolite In,H-, Co,H-, and Co,In,H-ZSM-5 were characterized by operando diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), temperature-programmed reduction by hydrogen (H₂-TPR), X-ray photoelectron spectroscopy (XPS), and activity in the selective catalytic reduction of NO (NO-SCR) by methane. The catalysts were shown to contain indium as [InO]⁺/[InOH]²⁺ cations, whereas cobalt was in the form of Co²⁺/[Co-OH]⁺ cations or Co-oxide clusters in amounts controlled by the applied preparation method. The NO-SCR by methane was shown to proceed in two coupled processes on distinctly different catalytic sites. One of the processes is the oxidation of NO to NO₂ by oxygen over Brønsted acid sites and/or cobalt-oxide species giving NO/NO₂ gas mixture (NO-COX reaction). The other process is the N₂ formation, which is the result of the reaction of methane and the NO/NO₂ mixture (CH₄/NO-SCR reaction). Molecules of NO and NO₂ were shown to become activated together as NO⁺/NO₃⁻ ion pair in reaction with [InO]⁺/[InOH]²⁺ or Co²⁺/[Co-OH]⁺ sites. Operando DRIFTS results suggested that the reaction of methane and NO₃⁻ generates an intermediate that rapidly reacts with the NO⁺ to give N₂. The promoting effect of the cobalt was related to the significantly higher NO-COX activity of Co-oxide clusters than that of the Brønsted acid sites. The accelerated NO-COX reaction speeds up the formation of NO⁺/NO₃⁻ species and the rate of the methane activation, being the rate-determining step of the NO-SCR reaction. It was also shown that the NO-SCR reaction can proceed if NO-COX and CH₄/NO-SCR active sites are separated in space. In order to avoid rate controlling NO₂ transport between the sites close proximity of the sites is favorable.

Keywords: In,H-ZSM-5; Promotion by Co; NO-SCR by CH; ₄; Operando DRIFTS

On the true morphology of highly photoactive anatase TiO₂ nanocrystals by M. Čaplovičová; P. Billik; Ľ. Čaplovič; V. Brezová; T. Turáni; G. Plesch; P. Fejdi (pp. 224-235).

Display Omitted► Highly photoactive anatase nanocrystals were prepared by mechano-chemical synthesis followed by heating at 700°C. ► 3D morphology of anatase determined by WBDF method under TEM. ► Mixture of polygonal shapes in BF images correspond to anatase bipyramidal morphology. ► High crystallinity and bipyramidal morphology faceted by {101} planes responsible for high photoactivity of anatase nanocrystals.Nanosized titania photocatalysts were prepared from a TiOSO₄·2H₂O–Na₂CO₃ mixture via high-energy milling for 5min, and subsequent annealing at a temperature range of 300–700°C/1h. Photoactivity of all samples monitored by electron paramagnetic resonance (EPR) spectroscopy was correlated with phase composition, crystallinity, crystal size and morphology of the annealed products. The anatase nanocrystals with an XRD average size of 24nm and well-faceted bipyramidal morphology exposed mainly by {101} type planes obtained on heating at 700°C, exhibited markedly higher photoactivity than the Aeroxide^® P25 TiO₂ standard and sample annealed at 600°C. The rapid increase in photoactivity was assigned to complete crystallization of the sample, optimal size, but mainly to the well-developed bipyramidal morphology of anatase nanocrystals and enlargement of the {101} type plane area due to final growth of bipyramids in the 〈001〉 direction.The weak beam dark field (WBDF) transmission electron microscopy (TEM) method was used to characterize morphology of the nanocrystals. Based on the thickness changes along the electron beam incidence inside the individual nanocrystals yielded by WBDF images, it was demonstrated that the mixture of polyhedral shaped anatase projections, such as square-like, hexagonal-like, rhomboid-like, rhombic-like, and rectangular-like prevailing in bright-field (BF) images, corresponds exclusively to tetragonal bipyramidal shape projected along different crystallographic directions. WBDF images of the most often occurring anatase nanocrystal projections are summarized and compared with both the schematic depictions of similarly oriented anatase bipyramids and that recorded in BF images. The difficulties of 3D morphology assessment from the projected nanocrystal shapes are highlighted. Attention is paid to the determination of facets limiting the nanocrystals, using the high resolution (HR)TEM method.

Keywords: TiO; ₂; Anatase; Nanocrystal; Crystal growth; Morphology characterization; Transmission electron microscopy; Weak-beam dark field method; Photocatalyst; EPR; Mechano-chemical synthesis

Gas-phase hydrodechlorination of trichloroethylene over Pd/NiMgAl mixed oxide catalysts by B.T. Meshesha; N. Barrabés; K. Föttinger; R.J. Chimentão; J. Llorca; F. Medina; G. Rupprechter; J.E. Sueiras (pp. 236-245).

.Display Omitted► Pd/NiMgAl mixed oxides with different compositions synthesized from hydrotalcites. ► Used for selective gas-phase hydrodechlorination of trichloroethylene to ethylene. ► Performance depends on Ni/Mg/Al ratio, reduction temperature and preparation route. ► Better selectivity with more surface metallic Ni upon high temperature reduction. ► For Pd on pre-reduced NiMgAl Ni metal promoted by Pd-Ni alloy was detected by HRTEM.Hydrotalcite derived NiMgAl mixed oxide (NiHT) catalysts with different NiMgAl molar ratio were synthesized and tested in the selective gas-phase hydrodechlorination of trichloroethylene to ethylene. The mixed oxide was further promoted by Pd in order to obtain Pd/NiHT catalysts. The catalysts performances for hydrodechlorination of trichloroethylene depend on the Ni/Mg/Al molar ratio, reduction temperature, and method of noble metal incorporation. The main products obtained were ethylene, methane, ethane, chloroethylene and traces of dichloroethylene. The higher the Ni amount in the NiHT support was, the higher were the catalytic activity and ethylene selectivity. Introduction of Pd increases the catalytic activity. Application of higher reduction temperatures improved the selectivity towards ethylene formation due to an increase in the concentration of surface metallic Ni. A better Pd-Ni surface interaction was obtained by impregnation of Pd on a previously reduced (823K) NiHT catalyst, resulting in higher ethylene selectivity (80%). The higher selectivity was associated to metallic Ni promoted by a Pd-Ni alloy, which was detected by HRTEM.

Keywords: Hydrodechlorination; Trichloroethylene; Pd; NiMgAl mixed oxides; Ni Hydrotalcite

Catalytic ozonation of toxic pollutants over magnetic cobalt-doped Fe₃O₄ suspensions by Aihua Lv; Chun Hu; Yulun Nie; Jiuhui Qu (pp. 246-252).

Display Omitted► Magnetic cobalt-doped Fe₃O₄ showed high, stable activity for catalytic ozonation. ► A hydroxyl radical reaction mechanism was verified for catalytic ozonation on cobalt-doped Fe₃O₄. ► Ozone was found to adsorb on the catalyst surface competing with water molecules by in situ ATR-FTIR. ► The introduction of Co enhanced the interfacial electron transfer.Magnetic cobalt-doped Fe₃O₄ (FeCo) was prepared using a co-precipitation method and characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV), and in situ attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy. The catalyst showed high, stable catalytic activity for the degradation and mineralization of toxic persistent organic pollutants, as demonstrated with the herbicides 2,4-dichlorophenoxyacetic acid, 2,4-dichlorophenol, and 2,4,6-trichlorophenol and pharmaceutical phenazone in aqueous solution with ozone. FeCo was very effective at the mineralization of refractory oxalic acid produced in the degradation of organic compounds. The ozone was adsorbed on the surface of FeCo competing with water molecules in the aqueous phase, and converted into hydroxyl radical, meanwhile the catalyst surface underwent oxidation and reduction as demonstrated by in situ ATR-FTIR, CV and other experimental data obtained. Furthermore, the characterization studies indicated that the introduction of Co increased the rate of FeCo oxidation and reduction during the decomposition of ozone, enhancing the activity and stability of Fe₃O₄.

Keywords: Adsorption of ozone; Magnetic catalyst; Multivalence; Redox; Toxic pollutant

Hydrogenolysis of glycerol to obtain 1,2-propanediol on Ce-promoted Ni/SBA-15 catalysts by I. Jiménez-Morales; F. Vila; R. Mariscal; A. Jiménez-López (pp. 253-259).

Display Omitted► Bifunctional catalysts were prepared by impregnation of SBA-15 silica with nickel and cerium. ► The catalysts are active in the hydrogenolysis of glycerol at 473K and 2.4MPa of H₂ pressure. ► The presence of cerium ions is essential to produce 1,2-PDO. ► Cerium ions act as strong acid sites producing acetol as intermediate.Metallic Ni (10wt.%) supported on SBA-15 silica and promoted with cerium loading ranged between 2.5 and 10wt.%, reduced at 723K during 1h, were used as catalysts in the hydrogenolysis of a glycerol aqueous solution (80wt.%) at 473K and 2.4MPa of H₂ pressure. Whereas pure Ni catalyst mainly produces volatile products by CC hydrogenolysis reaction, the promoted cerium catalysts lead to the formation of 1,2-propanediol (1,2-PDO) as majority product. After 8h of reaction the catalyst with 10wt.% of Ni and 7.5wt.% of Ce gives the maximum glycerol conversion and selectivity to 1,2-PDO, with yield of this substance of 24.2%/g of catalyst. The presence of cerium species is essential to produce 1,2-PDO. The effect of cerium oxide is to act as strong acid sites (TPD-NH₃), improve the metallic Ni dispersion (XRD, H₂ chemisorption and XPS) and to make more difficult their reduction (TPR). The stronger acidity suggests that the formation of acetol takes place easier in these catalysts and subsequently this intermediate is reduced by activated hydrogen from the nearby Ni metallic sites.

Keywords: Glycerol; Hydrogenolysis; SBA-15; Acid catalysts; Metallic nickel; Ceria

Study of potassium-supported TiO₂ catalysts for the production of biodiesel by Daniela Salinas; Paulo Araya; Sichem Guerrero (pp. 260-267).

Display Omitted► A hydrotreated TiO₂ supported potassium catalyst showed high activity to biodiesel. ► The calcination led to a form of potassium titanate with an increase in activity. ► Leached species into the reaction media had only minor activity. ► The recovered catalyst was used in successive reactions with stable conversions. ► A maximum conversion was achieved with the catalyst calcined at 700°C.A hydrotreated TiO₂ supported potassium catalyst, K/TiHT, was studied on the transesterification reaction of canola oil for the production of biodiesel. It was found that the calcination at different temperatures led to the transformation of the supported potassium catalyst into a titanate form of oxide. This was accompanied by a substantial increase in activity. Leaching studies found that although some potassium and titania was left in the products, the reaction mainly occurred in heterogeneous conditions. The contribution of the leached components to the activity was only minor. The recovered catalyst was then used in successive reactions producing stable conversions. A maximum conversion was achieved with the catalyst calcined at 700°C. Optimum reaction conditions were obtained when using a catalyst loading of 6% (w/w), a methanol to oil ratio of 54:1, and a temperature of reaction of 55°C.

Keywords: Heterogeneous transesterification; Biodiesel; Canola oil; Potassium; TiO; ₂

Synthesis of MWNTs/g-C₃N₄ composite photocatalysts with efficient visible light photocatalytic hydrogen evolution activity by Lei Ge; Changcun Han (pp. 268-274).

Display Omitted► Novel MWNTs/g-C₃N₄ composite photocatalysts were prepared for the first time. ► The MWNTs/g-C₃N₄ shows significantly enhanced H₂ evolution activity. ► Photocatalytic mechanism is proposed based on the experimental results. ► The mechanism is confirmed by PL spectra and transient photocurrent curves.Novel multi-walled carbon nanotubes (MWNTs) and graphitic carbon nitride (g-C₃N₄) composite photocatalysts were synthesized via a facile heating method. The resulting MWNTs/g-C₃N₄ composite photocatalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), ultraviolet–visible diffuse reflection spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS) and photoluminescence (PL) spectroscopy. The photoelectrochemical I– t curves were tested using several on–off cycles of visible light irradiation. The visible light photocatalytic hydrogen evolution was investigated for MWNTs/g-C₃N₄ in methanol aqueous solutions. The optimal MWNTs content is determined to be 2.0wt%; and corresponding H₂ evolution rate is 7.58μmolh⁻¹, about 3.7 folds that of pure g-C₃N₄. A possible mechanism of MWNTs on the enhancement of visible light performance is proposed. It suggests that MWNTs play key roles, which may lead to efficiently separation of the photo-generated charge carriers and, consequently, enhance the visible light photocatalytic H₂ production activity.

Keywords: Photocatalysis; Carbon nanotubes; Carbon nitrides; Hydrogen evolution

NO_x reduction by H₂ on WO_x/ZrO₂-supported Pd catalysts under lean conditions by Melanie Leicht; Florian J.P. Schott; Michael Bruns; Sven Kureti (pp. 275-282).

Display Omitted► Pd/WO_x/ZrO₂ catalyst developed for lean H₂-deNO_x. ► Substantial H₂-deNO_x performance with high N₂ selectivity. ► Operation window ranges from 100 to 250°C. ► H₂-deNO_x mainly occurs on the Pd component.This work addresses the H₂-deNO_x reaction representing a prospective tool for the low-temperature NO_x abatement under lean conditions. A novel Pd/WO_x/ZrO₂ catalyst with a W content of 8.7% was developed. The screening of the Pd load performed by temperature-programmed reaction on a laboratory bench provided highest efficiency at a Pd content of 0.41% (0.41Pd/W/ZrO₂). This catalyst showed considerable H₂-deNO_x activity between 125 and 280°C with an outstanding overall N₂ selectivity of 96%. Drastically higher performance was observed when 0.41Pd/W/ZrO₂ was evaluated under steady-state conditions resulting in 90% deNO_x at 160°C and a space velocity of 80,000h⁻¹. At this temperature, the apparent turnover frequency of Pd amounted to 8.1×10⁻⁵s⁻¹, which was very close to that of Pt existing in the highly active Pt/W/ZrO₂ system. The variation of the H₂ and O₂ feed concentration indicated that growing H₂ led to increasing H₂-deNO_x performance accompanied by decreasing N₂ selectivity. O₂ did not affect the selectivity, but clearly limited the operation window of the catalyst at O₂ contents above 6vol.%. The presence of H₂O as well as hydrothermal exposure at 750°C declined both activity as well as N₂ selectivity.The characterisation of the 0.41Pd/W/ZrO₂ catalyst by XRD, HRTEM/EDX and XPS showed tetragonal ZrO₂, whilst tungsten likely exists in sub-monolayer WO_x entities as well as amorphous WO₃ nanoparticles. Pd was predominately present in the form of PdO with particle sizes below 2nm.Mechanistic studies conducted by DRIFT spectroscopy indicated that the lean H₂-deNO_x reaction 0.41Pd/W/ZrO₂ occurs on the Pd sites. The reaction is considered to follow the mechanism according to Burch implying pre-reduction of the active sites by H₂ followed by NO dissociation and formation of N₂ with minor production of N₂O. However, some participation of NO_x species located on the W/ZrO₂ substrate cannot be ruled out completely.

Keywords: NO; _x; reduction by H; ₂; Catalyst; Pd; WO; _x; ZrO; ₂

Solar photocatalysis for the abatement of emerging micro-contaminants in wastewater: Synthesis, characterization and testing of various TiO₂ samples by Helen Dimitroula; Vasileia M. Daskalaki; Zacharias Frontistis; Dimitris I. Kondarides; Paraskevi Panagiotopoulou; Nikolaos P. Xekoukoulotakis; Dionissios Mantzavinos (pp. 283-291).

Display Omitted► Estrogenicity in municipal wastewaters is a serious environmental problem. ► Platinized titania can efficiently degrade xeno-estrogens under solar radiation. ► Doping with metals and non-metals does not enhance photoactivity under visible light. ► Reaction rates increase linearly with increasing catalyst and estrogen concentrations and photon flux. ► The complexity of water matrix impedes degradation.The photocatalytic degradation of a mixture of three compounds spiked in secondary treated wastewater by means of simulated solar radiation over titania suspensions was investigated. Bisphenol-A (BPA) and 17α-ethynylestradiol (EE2) were chosen as representatives of emerging micro-contaminants, while phenol was chosen as a reference contaminant. Ten titania samples were synthesized and employed to evaluate the effect of doping with nitrogen, phosphorous, calcium, silver, sodium and potassium, as well as platinum dispersion on photocatalytic activity. The catalysts were characterized by X-ray diffraction, diffuse reflectance UV–vis spectroscopy, nitrogen physisorption and selective chemisorption of CO or hydrogen.A 0.5% Pt/TiO₂ catalyst (38m²/g surface area, 72:28 anatase:rutile, 20 and 2nm crystallite size for TiO₂ and Pt, respectively) was highly active for the degradation of the contaminants, whose reactivity increased in the order: phenol2 exhibited comparable activity.The effect of various operating conditions, such as 0.5% Pt/TiO₂ concentration (125–1000mg/L), initial contaminant concentration (100–300μg/L each), photon flux (17.4×10⁻⁸–58×10⁻⁸einstein/(Ls) provided by a 150W Xenon lamp) and the water matrix (wastewater and ultrapure water), on degradation was then assessed. Reaction rates increased linearly with catalyst concentration and photon flux, confirming the photo-induced nature of the activation of the catalytic process; likewise, a linear dependence of rate on initial concentration occurred denoting first order kinetics. Degradation in wastewater was slower than in pure water by an order of magnitude, implying the scavenging behavior of effluent's constituents against hydroxyl radicals.The implications for tertiary wastewater treatment (e.g. mineralization, disinfection and removal of estrogenicity) are also discussed.

Keywords: Characterization; Degradation; Estrogenicity; Kinetics; Preparation

Tailored investigation and characterization of heterogeneous {Mn,Cu}/TiO₂ catalysts embedded within a ceria-based framework for the wet peroxide oxidation of hazardous pollutants by Rodrigo J.G. Lopes; M.L.N. Perdigoto; Rosa M. Quinta-Ferreira (pp. 292-301).

Normalized total organic carbon concentration as function of time for a sequential batch experiment with phenolic mixture injection each 60min.Display Omitted► We investigate the CWPO of phenol-like pollutants under milder operating conditions. ► {Mn/Cu}TiO₂–CeO₂ were characterized by means of XRD, BET, SEM, and TEM. ► Embedded lanthanide frameworks were the most active toward the complete mineralization. ► Mn/TiO₂–CeO₂ exhibited worthy properties concerning long term catalytic stability.In this work, novel catalyst frameworks including Mn/TiO₂–CeO₂, Cu/TiO₂–CeO₂, Mn–Ce–O, Mn–Cu–O, and TiO₂–CeO₂ were investigated for the catalytic wet peroxide oxidation of phenol-like pollutants. Aiming to gain further insights into the heterogeneous catalysis of manganese and copper metals supported on titanium and cerium oxides, the abatement efficiency was evaluated under different operating conditions and in terms of individual phenolic compounds depletion. Here, Mn/TiO₂–CeO₂ was found as the most active promoter for the highest detoxification rate. Second, pH profiles and reaction intermediates unveiled a free-radical mechanism and underlined the synergism behavior in catalytic wet peroxide oxidation. The titanium based oxides exhibited the strongest catalytic stability by the quantification of metal leaching and carbon adsorption. Afterwards, the integrated metal framework encompassed by Mn/TiO₂–CeO₂ and Cu/TiO₂–CeO₂ catalysts was realized in X-ray diffraction analysis and the TEM pattern gave rise to superior homogenous structures for Mn/TiO₂–CeO₂, which has been ascribed to the integration of the lanthanide into the lattice framework of titanium oxide. Finally, several sequential feed-batch trials were carried out emphasizing that 67% of pollutant conversion can be retained after long term catalytic runs.

Keywords: Catalytic wet peroxide oxidation; Hazardous pollutants; SEM; XRD; TiO; ₂; CeO; ₂

Single-stage medium temperature water-gas shift reaction over Pt/ZrO₂ – Support structural polymorphism and catalyst deactivation by Carlos A. Franchini; Andréa M. Duarte de Farias; Elise M. Albuquerque; Renata dos Santos; Marco A. Fraga (pp. 302-309).

Zirconia polymorphism does play an imperative role in determining the catalyst activity, being the monoclinic structure the one rendering the more active system. The deactivation of water-gas shift catalysts may be reasonably described by considering the drastic changes in the metal phase dispersion along reaction as determined over both polymorphic samples presented in this work.Display Omitted► Platinum catalysts prepared over commercial monoclinic and tetragonal ZrO₂. ► Polymorphic catalysts for single-stage medium temperature water-gas shift reaction. ► The monoclinic structure renders the more active system. ► Deactivation is associated with the decrease of platinum dispersion upon reaction.Influence of zirconia polymorphism on water-gas shift reaction was investigated. The study was carried out over catalysts with similar features, which allowed assessing any effect brought about by the support crystalline structure. It was found that zirconia polymorphism determines the catalyst activity and the monoclinic structure renders a more active system. It is most likely due to the presence of hydroxyl groups, which have been claimed to be involved in the formation of important reaction intermediates. Catalyst deactivation was also addressed and it could be concluded that the changes in metal phase dispersion along reaction play a quite important role on the ZrO₂-supported catalyst stability.

Keywords: Deactivation; Polymorphism; Zirconia; Monoclinic; Tetragonal; Fuel cell

Iron–sulfur codoped TiO₂ anatase nano-materials: UV and sunlight activity for toluene degradation by Konstantinos C. Christoforidis; Santiago J.A. Figueroa; Marcos Fernández-García (pp. 310-316).

Display Omitted► S affected significantly the morphological characteristics of TiO₂ catalysts. ► S/Fe co-doped TiO₂ show enhanced photoactivity compared to Fe single-doped TiO₂. ► Selectivity of partial oxidation products was increased with increasing S-content. ► The differences in photoactivity and selectivity are surface properties related.Iron and sulfur single- and co-doped TiO₂ nanocrystals were prepared and characterized by a multitechnique approach. The presence of sulfur affected drastically the crystal size of anatase as well as other morphological characteristics such as BET surface area, pore volume and pore size. Significant differences were also detected on the isolated OH species concentration as a function of sulfur content. On the contrary, X-ray absorption spectroscopy (XAFS) showed that sulfur did not alter substantially the structural and electronic properties of Fe on TiO₂. The photocatalytic activity of the synthesized TiO₂ powders was studied in the gas-phase oxidation of toluene. The trials showed that the co-doped S/Fe-TiO₂ nanomaterials have enhanced photo-activity compared to the reference single-doped Fe-TiO₂ under both sunlight and UV-light irradiation. This is not however the case if compared with the single S-doped materials. Sulfur additionally modifies the selectivity of toluene photo-oxidation toward partial oxidation products. The partial vs. total oxidation yield ratio increased with increasing S content in both co-doped S/Fe-TiO₂ or single-doped S-TiO₂ series and was attributed to differences in surface properties related to both S-containing and OH entities.

Keywords: Photocatalysis; Titania; Anatase; Iron; Fe; Sulfur; Co-doping; Selective partial oxidation; Toluene; Benzaldehyde

Polymer electrolyte fuel cell supplied with carbon dioxide. Can be the reductant water instead of hydrogen? by Motoharu Morikawa; Naveed Ahmed; Yuta Ogura; Yasuo Izumi (pp. 317-320).

Display Omitted► PEFC current was obtained by supplying H₂ to Pt/C and CO₂ to Zn-Cu-Ga catalyst. ► Utilizing PEFC, methanol was formed even from water and CO₂. ► Methanol synthesis using PEFC was compared to a test for Pt/C and Zn-Cu-Ga mixture. ► Negligible methanol was formed from water and CO₂ for the mixed catalysts. ► Water was partially decomposed and protons apparently moved in Nafion to cathode.Polymer-electrolyte fuel cell supplying CO₂ was demonstrated. Using a PEFC, 95mol% of methanol was selectively formed by supplying H₂ to Pt catalyst and CO₂ to Zn-Cu-Ga layered double hydroxide catalyst accompanying protons and electrons transfer, i.e. H₂→2H⁺+2e⁻ at anode followed by CO₂+6H⁺+6e⁻→CH₃OH+H₂O at cathode. Using PEFC, CO₂ reduction with water was also enabled to methanol (100–86mol%) in contrast that negligible amount of methanol was formed if mixed oxidation and reduction catalysts were under CO₂ and moisture. At anode, water was dissociated over Pt catalyst to provide protons (H₂O→OH(adsorbed)+H⁺+e⁻) that transferred to Zn-Cu-Ga catalysts at cathode on which CO₂ was progressively reduced to methanol (CO₂+6H⁺+6e⁻→CH₃OH+H₂O).

Keywords: Carbon dioxide; Water; Methanol; Fuel cell; PEFC; Reductant; Proton transfer

RuSn bimetallic catalysts for selective hydrogenation of levulinic acid to γ-valerolactone by Stephanie G. Wettstein; Jesse Q. Bond; David Martin Alonso; Hien N. Pham; Abhaya K. Datye; James A. Dumesic (pp. 321-329).

Display Omitted► Ru–Sn catalysts can hydrogenate levulinic acid to gamma-valerolactone in presence of alkylphenol solvents. ► Several phases exist for Ru–Sn systems: monometallic Ru and Sn and bimetallic RuSn. ► The monometallic Ru phase is the most active, but deactivates with time on stream. ► Addition of Sn to Ru/C forms alloys that improve catalyst selectivity and stability. ► RuSn₄/C has proven to be stable even using levulinic acid produced from corn stover.Carbon-supported ruthenium catalysts containing different amounts of tin were studied for the hydrogenation of levulinic acid (LA) to gamma-valerolactone (GVL) in a 2-sec-butyl-phenol (SBP) solvent. Results from reaction kinetics measurements (453K and 35bar H₂) showed that the Ru/C catalyst was initially more active for hydrogenation of both LA and SBP (i.e., 0.051s⁻¹ for conversion of LA to GVL), followed by continuous deactivation versus time on stream. In contrast, the catalyst containing equal amounts of Ru and Sn had a lower activity for LA to GVL conversion (0.005s⁻¹), but displayed stable activity versus time on stream and showed 100% selectivity for hydrogenation of LA versus the SBP solvent. Increasing the amount of Sn to a 1 to 4 Ru:Sn atomic ratio creates an additional phase, β-Sn, that is not active for hydrogenation, leaches into the SBP solvent, and sinters under reaction conditions. Results from CO and O₂ chemisorption and electron microscopy measurements indicated that the Ru-based metal particles did not leach or sinter at reaction conditions, and that the surfaces of these particles became progressively enriched with Sn as the Sn-loading increases. In addition, Sn did not significantly leach from the catalysts when present as an intermetallic alloy with Ru, such as Ru₂Sn₃ and Ru₃Sn₇. Using LA produced from corn stover, the RuSn₄/C catalyst was stable and demonstrated that it is a promising catalyst to produce valuable chemicals and fuels from real biomass.

Keywords: Alkylphenol; Biomass; Heterogeneous catalysis; Renewable resources; Bimetallic

Hydrogen production from cellulose, lignin, bark and model carbohydrates in supercritical water using nickel and ruthenium catalysts by Pooya Azadi; Sami Khan; Friederike Strobel; Faraz Azadi; Ramin Farnood / (pp. 330-338).

Display Omitted► Supported nickel catalysts had a high hydrogen selectivity. ► Ru/C was found to be more active than Ru/γ-Al₂O₃. ► Metal dispersion significantly affected the methane formation rate.In this study, the catalytic activity and hydrogen selectivity of Ni/α-Al₂O₃, Ni/hydrotalcite, Raney nickel, Ru/C and Ru/γ-Al₂O₃ catalysts for hydrothermal hydrogen production from lignocellulosic biomass have been evaluated. The feedstocks included glucose, cellulose, fructose, xylan, pulp, lignin and bark. The experiments were carried out at 380°C in a batch reactor with 2wt% feed concentration. It was found that the gasification of glucose, fructose, cellulose, xylan and pulp resulted in comparable gas yields (±10% at 60min), whereas lignin was substantially harder to gasify. Interestingly, gasification yield of bark which has a high lignin content was comparable to those of carbohydrates after 60min reaction time. For a given feedstock, catalyst type affected both the gasification yield and the product distribution. Ni/α-Al₂O₃ and Ni/hydrotalcite catalysts were not only highly active for the gasification of carbohydrates, but also had better hydrogen selectivity when compared to Raney nickel, Ru/C and Ru/γ-Al₂O₃. In particular, gasification of bark in the presence of these catalysts resulted in negligible amounts of alkanes.

Keywords: Supercritical water gasification; Catalyst; Biomass; Model compounds; Hydrogen

SO₂ adsorption and transformation on calcined NiAl hydrotalcite-like compounds surfaces: An in situ FTIR and DFT study by Ling Zhao; Xinyong Li; Ce Hao; Colin L. Raston (pp. 339-345).

Display Omitted► Flower-like hydrotalcite-based NiAl mixed oxides showed excellent SO₂ adsorption. ► The SO₂ adsorbed on the NiAlO catalyst is converted into SO₃^2–, HSO₃^–, and SO₄^2–. ► Density functional theory confirmed a binuclear bidentate binding configuration.Flower-like hydrotalcite-based NiAl mixed oxides with high surface area were synthesized by urea hydrolysis approach, and employed for SO₂ removal. The catalyst was well characterized by TGA, ICP, XRD, SEM, TEM and N₂ adsorption/desorption isotherm analyses. The calcined NiAlO showed excellent SO₂ adsorption and its adsorption equilibrium was of a type I isotherm, which significantly improved the adsorption performance for low-concentration SO₂. XPS and TPD methods were conducted to identify the sulfate species. Specifically, in situ Fourier transform infrared spectroscopy revealed that adsorbed SO₂ molecules formed surface bidentate binuclear sulfate. Density functional theory based computations interpreted the vibrational data associated with the NiAlO surface and confirmed that sulfate species adopted a binuclear bidentate binding configuration on the surface of NiAlO catalyst.

Keywords: NiAl mixed oxides; SO; ₂; removal; In situ; FTIR; DFT

Selective catalytic oxidation of ammonia to nitrogen over CuO/CNTs: The promoting effect of the defects of CNTs on the catalytic activity and selectivity by Shaoqing Song; Shujuan Jiang (pp. 346-350).

CuO/CNTs were prepared as catalysts for the selective catalytic oxidation of ammonia to nitrogen. The supported CuO could be activated by the surface defects of CNTs, and the defects can promote electron transfer in the catalysis. Thus, CuO/CNT catalysts demonstrated high activity and N₂ selectivity, indicating a potential application for the selective catalytic oxidation of ammonia.Display Omitted► CuO/CNTs catalysts. ► CuO could be activated by the surface defects of CNTs. ► The surface defects could also promote electron transfer in the catalysis. ► The temperature for ammonia SCO shifted to 189°C with high N₂ selectivity. ► The CuO/CNTs are promising catalysts for ammonia SCO.CuO/CNTs were prepared as catalysts for the selective catalytic oxidation of ammonia and demonstrated high catalytic activity and N₂ selectivity. The study results showed that the surface defects of carbon nanotubes (CNTs) could not only activate CuO, but also promote the electron transfer in the catalysis. Thus, along with increasing the defect density of the CNTs, the temperature for the complete ammonia oxidation could be decreased from 235°C to 189°C and the corresponding N₂ selectivity increased from 93.8% to 98.7%. Moreover, there was no apparent decrease in the catalytic activity at prolonged reaction time, indicating CuO/CNT catalysts are promising for the selective catalytic oxidation of ammonia.

Keywords: CuO/CNTs; Ammonia oxidation; N; ₂; selectivity; Defects

Surface properties and visible light activity of W-TiO₂ photocatalysts prepared by surface impregnation and sol–gel method by Ewelina Grabowska; Janusz W. Sobczak; Maria Gazda; Adriana Zaleska (pp. 351-359).

Display Omitted► W-TiO₂ powders showed higher photoactivity under visible light. ► The preparation method effect on photoactivity/surface properties was investigated. ► Different phenol degradation mechanism in the presence of W-TiO₂/Vis was observed. ► Phenol oxidation under Vis light leads to formation of hydroxyproduct. ► The presence of OH radical in W-TiO₂ system was confirmed by methanol oxidation.Preparation route of new tungsten-containing TiO₂ powders (W-TiO₂) and their activity under visible light are reported. The photocatalysts were prepared by the sol–gel method and by grinding anatase powder with a dopant precursor followed by calcinations (surface impregnation method). Tungsten oxide and tungsten hexacarbonyl were used as tungsten sources in both photocatalyst preparation procedure. The obtained photocatalysts were subsequently characterized by a BET method, X-ray photoelectron emission spectroscopy (XPS) and X-ray powder diffraction analysis (XRD). Degradation efficiency of phenol and formation of phenol degradation by-products were compared for two systems: W-doped TiO₂ under visible light and P-25 under UV irradiation. The highest photoactivity under visible light was observed for 3%-W-TiO₂ and it was three times higher than photoactivity of pure TiO₂. Phenol oxidation in the presence of W-TiO₂ and visible light leads to formation of hydroxyproduct (catechol) and phenol ring cleavage products (muconic aldehyde).

Keywords: W-TiO; ₂; Modified-TiO; ₂; Doped-TiO; ₂; Tungsten; Visible light photocatalysis; Heterogeneous photocatalysis

Catalysis oxidation of 1,2-dichloroethane and ethyl acetate over ceria nanocrystals with well-defined crystal planes by Qiguang Dai; Hao Huang; Yu Zhu; Wei Deng; Shuxing Bai; Xingyi Wang; Guanzhong Lu (pp. 360-368).

Display Omitted► The ceria nanorods, nanocubes and nano-octahedrons are synthesized via hydrothermal method. ► The catalysis oxidation of DCE and EA is investigated over ceria exposed well-defined crystal planes. ► A possible reaction mechanism for the catalytic oxidation of DCE and EA over the ceria was proposed.The ceria nanorods, nanocubes and nano-octahedrons exposed crystal planes of (110)/(100), (100) and (111), respectively, are synthesized via simple hydrothermal method, and characterized by XRD, N₂ adsorption, TEM/HRTEM, Raman, OSC and H₂-TPR. Comparing with nanocubes and nano-octahedrons, the ceria nanorods showed higher surface area, smaller crystallite size, more oxygen vacancies, higher OSC and mobility of oxygen. The catalysis oxidation of DCE and EA was investigated over these ceria exposed well-defined crystal planes for the first time. The results indicated that ceria nanorods showed the highest catalysis activities, followed by nanocubes and nano-octahedrons. Moreover, a possible reaction mechanism for the catalytic oxidation of DCE over the ceria catalyst was proposed.

Keywords: Catalysis oxidation; 1,2-Dichloroethane; Ethyl acetate; Ceria; Crystal planes

Alumina-supported In₂O₃, Ga₂O₃ and B₂O₃ catalysts for lean NO_x reduction with dimethyl ether by Sara Erkfeldt; Martin Petersson; Anders Palmqvist (pp. 369-383).

Display Omitted► γ-Alumina-based catalysts were studied for lean NO_x reduction with dimethyl ether. ► In₂O₃/Al₂O₃, Ga₂O₃/Al₂O₃ and B₂O₃/Al₂O₃ gave higher NO_x conversion than pure Al₂O₃. ► In₂O₃/Al₂O₃ catalysts showed the highest NO_x conversion at low temperature. ► Pure In₂O₃ was inactive for NO_x reduction with dimethyl ether. ► Ga₂O₃/Al₂O₃ and B₂O₃/Al₂O₃ gave the highest NO_x conversion at high temperature.Alumina-supported In₂O₃, Ga₂O₃ and B₂O₃ were investigated as catalysts for lean NO_x reduction with DME as reducing agent and compared to pure Al₂O₃ and In₂O₃. The In₂O₃-promoted alumina catalysts showed the highest NO_x conversion at low temperatures, although with a narrow temperature window. Pure In₂O₃, on the other hand, was inactive for NO_x reduction with DME. The Ga₂O₃- and B₂O₃-promoted alumina catalysts gave the highest NO_x conversion at higher temperatures, showed a temperature window similar to pure alumina, but were less sensitive to H₂O inhibition. Possible reasons for these observations are discussed.

Keywords: Hydrocarbon-SCR; NO; _x; reduction; Alumina; Alternative fuel; Dimethyl ether; Indium; Gallium; Boron

Ni/SiO₂ and Ni/ZrO₂ catalysts for the steam reforming of ethanol by Ilenia Rossetti; Cesare Biffi; Claudia L. Bianchi; Valentina Nichele; Michela Signoretto; Federica Menegazzo; Elisabetta Finocchio; Gianguido Ramis; Alessandro Di Michele (pp. 384-396).

Conversion, products distribution and C balance during the steam reforming of bioethanol depended on both surface acidity and on the stability of the Ni clusters. The latter was in turn dependent on the metal–support interaction and tuneable during catalyst synthesis.Display Omitted► Set up and comparison of different synthesis methods for reforming catalysts. ► Comparison of activity and stability under different reaction conditions. ► Correlation of activity and stability with surface acidity and metal dispersion. ► 80% of equilibrium conversion reached at 625°C with stable performance.SiO₂ and ZrO₂ supported Ni catalysts were prepared for use in the steam reforming of ethanol. The catalytic performances, in terms of both H₂ productivity and stability towards coking and sintering, were related to the physico-chemical properties of the catalysts.The samples were prepared either by synthesis of the support by precipitation and subsequent impregnation with the active phase, or by direct synthesis through flame pyrolysis. The latter has been chosen because it leads to nanostructured oxides, often quenched in very disperse or metastable form, characterised by high thermal resistance, important for this high temperature application.Many techniques have been used to assess the physico-chemical properties of the catalysts. The samples showed different textural, structural and morphological properties, as well as different reducibility and thermal resistance, depending on the preparation method and support. Therefore, besides evaluating the effect of catalyst formulation and preparation method on the catalytic performance, the influence of all such properties has been considered. The fundamental parameter governing the final catalyst properties was metal–support interaction. In particular, the stronger the latter parameter, the higher was metal dispersion, leading to small and stable Ni clusters. This influenced both activity and the resistance towards coking. Surface acidity was also taken into account considering the effect of the different nature of acid sites (silanols or Lewis a.s.) of both support and metal phase on catalyst deactivation. The best results were obtained with a 10wt% Ni/SiO₂ sample, prepared by FP, when tested at 625°C. H₂ productivity of 1.44molH₂/minkg_cat was reached, corresponding to ca. 80% of the maximum value achievable under the selected conditions. This result was accompanied by the lowest CO/CO₂ ratio and 100% carbon balance without by-products in the outflowing gas.

Keywords: Ethanol steam reforming; Flame pyrolysis; Ni/ZrO; ₂; Ni/SiO; ₂; Metal–support interaction

Cobalt based emission control catalysts with high resistance towards halide poisoning by Markus Hammes; Klaus Stöwe; Wilhelm F. Maier (pp. 397-405).

Display Omitted► High throughput technology composed of automated library preparation, emissivity corrected IR-thermography for screening. ► Conventional gas phase catalysis with GC-analysis for validation of potential hits. ► From over 250 materials studied, three catalysts emerged as best and most promising: Ce₂₀Co₄₀Cr₄₀O_x, Co₃₀Cr₁₀Ni₆₀O_x and Ce₅Ni₅Co₉₀O_x. ► Materials of interest characterized by BET, XRD and XRF. ► Effect of various oxides or dopands on the catalytic performance.Halide poisoning is a common problem in industrial exhaust control. In this study new catalysts have been searched, which effectively oxidize hydrocarbons in the presence of methyl bromide as halide containing pollutant. The search focused on low cost mixed metal oxides based on Ce, Co, Cr and Ni. Noble metals, Cu and Mn were neglected. High throughput technologies have been applied to accelerate the development process. Screening was based on emissivity corrected IR-thermography. Potential hits were validated using conventional gas phase flow catalysis. The tested catalysts were arranged in four ternary metal oxide composition spreads: Ce–Co–Cr, Ce–Co–Ni, Ce–Cr–Ni and Co–Cr–Ni. Out of the screening, Co–Ni mixed oxides had high CO conversion rates in the presence of methyl bromide. Further these catalysts were optimized by catalyst doping and composition variation. In a 50h long term experiment the CO oxidation in the presence of methyl bromide was checked for our best catalyst Ce₅Co₉₀Ni₅O_x. Additionally, the effect of various metal oxide additives on catalytic performance and BET surface is described.

Keywords: Emission control; Halide poisoning; Mixed oxides; Noble metal free; Heterogeneous catalysts

Evaluation of ion exchange-modified Y and ZSM5 zeolites in Cr(VI) biosorption and catalytic oxidation of ethyl acetate by B. Silva; H. Figueiredo; O.S.G.P. Soares; M.F.R. Pereira; J.L. Figueiredo; A.E. Lewandowska; M.A. Bañares; I.C. Neves; T. Tavares (pp. 406-413).

Display Omitted► The acidity of HY and HZSM5 zeolites was modified by ion exchange treatments with NaNO₃. ► Cr-Y and Cr-ZSM5 zeolites were obtained by biosorption of Cr(VI) from water. ► These zeolites were reused as catalysts in the oxidation of ethyl acetate. ► Cr-ZSM5 zeolites were considerably more active and selective towards CO₂ than Cr-Y zeolites. ► The structure and the acidity of the supports were the main factors affecting the catalytic performance.The aim of this work was the evaluation of the performance of two zeolites with different structures (FAU and MFI) and acidity properties in the biosorption of Cr(VI) and catalytic oxidation of ethyl acetate. The starting zeolites, Y (FAU) and ZSM5 (MFI), were modified by ion exchange treatments with NaNO₃ in order to obtain zeolites with different acidity and sodium content. A biosorption system consisting of a bacterium, Arthrobacter viscosus, supported on the different zeolites was used for Cr(VI) reduction and removal from solution. The best removal efficiencies and uptake of chromium, above 90% and 14mg_Cr/g_zeolite respectively, were achieved for Y zeolites due to their higher ion exchange capacity in comparison with ZSM5 zeolites. The ion exchange treatment did not produce considerable changes on the uptake process performed by the modified zeolites. Y and ZSM5 zeolites were characterized by ICP-AES, SEM, NH₃ chemisorption, XRD and N₂ adsorption. Y and ZSM5 zeolites obtained after biosorption presented chromium loadings between 0.92 and 1.20%, and were successfully reused as catalysts in the oxidation of ethyl acetate. The chromium-loaded ZSM5 zeolites were considerably more active and selective towards CO₂ than chromium-loaded Y zeolites, essentially due to their different framework structure, textural and acidity properties. The different sodium content of Y and ZSM5 zeolites did not produce marked changes in the catalytic behaviour of these catalysts.

Keywords: Y zeolite; ZSM5 zeolite; Ion exchange; Cr(VI) biosorption; Catalytic oxidation; Ethyl acetate

Pumice-catalyzed ozonation degradation of p-chloronitrobenzene in aqueous solution by Lei Yuan; Jimin Shen; Zhonglin Chen; Yu Liu (pp. 414-419).

Display Omitted► Natural pumice as catalyst for ozonation. ► Pumice-catalyzed ozonation degradation of pCNB in aqueous solution. ► Pumice enhances the efficiency of pCNB degradation. ► Pumice has a synergistic effect with ozone for pCNB degradation.The use of pumice for heterogeneous catalytic ozonation significantly enhances the degradation efficiency and the total organic carbon (TOC) removal of p-chloronitrobenzene ( pCNB) in aqueous solution compared with ozonation alone because of the synergistic effect between ozone and the catalyst. The pCNB adsorption was too small to contribute significantly to the pCNB degradation during pumice-catalyzed ozonation. The decomposition rate of the aqueous ozone increased 1.374-fold in the presence of pumice. High pH also positively affected the pumice-catalyzed ozonation, as nearly uncharged surfaces (the solution pH was close to the point of zero charge) are favorable for catalytic pCNB ozonation. tert-Butanol remarkably decreases the removal efficiency of catalytic pCNB ozonation, which suggests that pCNB degradation follows the mechanism of hydroxyl radical oxidation. Increasing both the pumice and ozone concentrations enhanced the removal effectiveness of pCNB. Pumice is an efficient green catalyst for pCNB degradation in aqueous solution.

Keywords: Catalytic ozonation; p; -Chloronitrobenzene; Pumice; Hydroxyl radical

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Applied Catalysis B, Environmental (v.117-118, #)