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Applied Catalysis B, Environmental (v.106, #3-4)

Editorial Board (pp. i).

Contents (pp. co4).

Contents Continued (pp. i-ii).

Editorial Board (pp. co2).

Urea decomposition and HNCO hydrolysis studied over titanium dioxide, Fe-Beta and γ-Alumina by Andreas Lundström; Thomas Snelling; Per Morsing; Pär Gabrielsson; Enric Senar; Louise Olsson (pp. 273-279).

Thermogram and evolved NH₃, HNCO and CO₂ for the TiO₂ monolith impregnated with a 30% solution of urea and water with a sweep flow rate of 80mL/min of humid Ar. The first event on the DSC curve is the evaporation of water between approximately 25 and 100̊C. The second event is the melting of urea which occurs at 130–140̊C, this is followed closely by the decomposition and hydrolysis of the urea between 150 and 210̊C. The hydrolyses is enhanced by the titania coating.Display Omitted► TiO₂ exhibited the best hydrolysis performance compared to inert cordierite, alumina and Fe-Beta ► All samples performed the hydrolysis better under humid conditions, as was expected. ► Fe-Beta produced huge amounts of ammonia and CO₂ (higher than accounted for by the weighing procedure). This was attributed to selective accumulation of urea within the zeolite during impregnation ► One experiment with lower flow, higher urea loading and increased ramp speed conducted in dry Ar over TiO₂ showed a large formation of biproducts. ► In the presence of water titania negated the formation of biuret and CYA. This was attributed to the effective hydrolysis of HNCO preventing it to act as a pre-cursor in the formation of biuret and CYA.The catalytic effect of titanium dioxide, Fe-Beta, γ-Alumina, on the thermal decomposition of urea and hydrolysis of HNCO, was investigated using differential scanning calorimetry (DSC) and mass spectrometry (MS). The catalytic materials were coated on cordierite substrates and a pure cordierite sample was also used for comparison. The urea was administered by impregnating the monoliths with an urea/water solution. The experiments were performed using a constant heating rate of 10K/min and over a temperature range of 25–500°C. A sweep gas flow rate of 80mL/min of either dry or humid Ar was used. The results show that TiO₂ is the best hydrolysis catalyst. Fe-Beta showed a very large ammonia production, due to selective adsorption of urea during the impregnation of the monolith in the urea solution. One experiment with lower flow, higher urea loading and increased ramp speed conducted in dry Ar over TiO₂ showed a large formation of biproducts. This experiment was repeated in the presence of water and this decreased the formation of CYA and biuret significantly. The reason for this is the effective hydrolysis of the HNCO over titania, which hindered the bi-product formation.

Keywords: Urea decomposition; HNCO hydrolysis; CYA; Biuret; SCR; TiO; ₂; Fe-Beta; Zeolite; γ-Al; ₂; O; ₃; Micro-calorimetry; MS

Steam reforming of phenol over Ni-based catalysts – A comparative study by B. Matas Güell; I.V. Babich; L. Lefferts; K. Seshan (pp. 280-286).

.Display Omitted► The nickel catalysts studied are very active for the reforming of biomass-derived tars. ► Ni/CeO₂-ZrO₂ exhibited better catalyst stability than Ni/K₂O-La₂O₃-ZrO₂. ► The coke location on the catalyst is key to explain the different catalyst stability. ► The red-ox properties of CeO₂-ZrO₂ explain the difference in coke location.The influence of the support in the steam reforming of phenol at 700°C has been examined over Ni/K-La-ZrO₂ and Ni/Ce-ZrO₂. Both catalysts exhibited high activity and good stability in terms of phenol conversion. However, Ni/K-La-ZrO₂ showed a pronounced change in product distribution with TOS, which was related to deactivation for the water–gas shift. The high activity observed for the water- gas shift over the unsupported nickel and the difference in the location of coke between the two nickel catalysts are suggested to be the key reasons for the difference in catalyst stability. The red-ox properties of Ce-ZrO₂ are proposed to result in more oxygenated species (O and OH) than the non-red-ox K-La-ZrO₂. These oxygenated species, which are suggested to undergo back-spillover from the support to the nickel surface, could be responsible for keeping the nickel surface clean by gasifying the carbonaceous species accumulated on nickel.

Keywords: Hydrogen; Steam reforming; Phenol; Nickel; Catalyst; Red-ox

Facile synthesis of N-doped TiO₂ nanoparticles by a modified polymeric precursor method and its photocatalytic properties by Gabriela B. Soares; Bruno Bravin; Carlos M.P. Vaz; Caue Ribeiro (pp. 287-294).

Display Omitted► A facile and simple route to produce N-doped TiO₂ nanoparticles using urea was described. ► Characterization results indicated that the doping process was effective. ► Unmodified TiO₂ nanoparticles indicated higher UV-C photocatalytic activity than doped ones. ► The N-doped TiO₂ nanoparticles showed better visible photocatalytic activity than in UV light.In recent years, significant effort has been focused on the production of visible-light activated photocatalysts such as N-doped TiO₂ for advanced oxidation processes. Thus, this paper describes a facile and simple route to produce N-doped TiO₂ nanoparticles by a modified polymeric precursor method using urea. In addition, the paper describes the characterization and photocatalytic activity evaluation of N-doped TiO₂ nanoparticles. The predominance of the anatase phase and the modification of band-gap energies in N-TiO₂ indicate that the doping process is effective; Raman spectroscopy shows bands related to TiO_xN1−_x. The presence of N in higher amounts in the doped nanoparticles confirms the doping process which was also confirmed by X-ray photonelectron spectroscopy (XPS). Unmodified TiO₂ nanoparticles indicate higher UV-C photocatalytic activity, and the N-doped TiO₂ nanoparticles show better visible photocatalytic activity, suggesting a useful way to operate those catalysts under visible light and/or sunlight.

Keywords: Nanoparticle; TiO; ₂; Photocatalysis

Steam reforming of ethanol/gasoline mixtures: Deactivation, regeneration and stable performance by Amanda Simson; Robert Farrauto; Marco Castaldi (pp. 295-303).

Display Omitted► Small amounts of sulfur deactivate the catalyst. ► Air regeneration restores activity but subsequent deactivation occurs more rapidly. ► Sulfur is not the sole cause of irreversible deactivation. ► Catalyst chemistry altered with extended periods of time reforming. ► Intermediates of acetaldehyde and ethylene detected during deactivation.The steam reforming of 85% pure ethanol, 15% gasoline (E85) with and without sulfur was studied over a bimetallic precious metal (Rh/Pt) catalyst deposited on a ceramic monolith. Tests performed at low space velocities (22,000h⁻¹) confirmed that the catalyst could achieve 100% ethanol and gasoline conversion to equilibrium concentrations of H₂, CO, CO₂ and CH₄ with no signs of deactivation for at least 110h reforming a sulfur-free E85 fuel. In the presence of 5ppm sulfur the catalyst maintained 100% ethanol and 100% gasoline conversion for approximately 22h before rapid deactivation resulted in ethanol conversion values below 21%. TPO analysis established large carbon deposits had formed on the catalyst surface demonstrating that sulfur promoted carbon formation. Following such extensive deactivation full activity was recovered after treating the catalyst with air; however subsequent deactivation occurred more rapidly indicating that some amount of permanent damage had occurred. A process with preemptive regeneration via air treatment was studied and it was found to extend the period of stable activity.

Keywords: Ethanol steam reforming; E85; Sulfur deactivation; Catalyst regeneration; Precious metal catalysts

Hydrogen from urea–water and ammonia–water solutions by Andrew N. Rollinson; Gavin L. Rickett; Amanda Lea-Langton; Valerie Dupont; Martyn V. Twigg (pp. 304-315).

Display Omitted► Urea shown as novel H₂ carrier via renewable route and ease of steam reforming. ► Equilibrium shows 500–620°C best to approach max H₂ yield of 10wt% of urea feed. ► Experiments close to equilibrium for molar H₂O:C ratio of 6 and 7 and above 550°C. ► Negligible NH₃ by-product at above 550°C, easily removed by condensation. ► BET, SEM/TEM, EDX and Rietveld refinement powder XRD show no catalyst deactivation.The conversion of urea–water into hydrogen was investigated in a downward flow packed-bed reactor using a Ni–Al₂O₃ catalyst. This was conducted at atmospheric pressure under molar steam to carbon ratios (S:C) of 4–7, and at temperatures between 500 and 700°C. The urea and water conversions, selectivity to the hydrogen containing products H₂, CH₄ and NH₃, selectivity to the carbon containing products CO₂, CO and CH₄, and the hydrogen yield, were very close to the calculated equilibrium values at and above S:C of 5 and temperatures at and above 600°C. CO₂ dominated the carbon products, in agreement with equilibrium trends. The selectivity to ammonia decreased abruptly from 20% to below 5% when the temperature increased from 500 to 550°C, and exhibited a small sensitivity to the steam to carbon ratio. High selectivity to NH₃ was accompanied by a low urea conversion to CO, CO₂ and CH₄, and poor hydrogen yield below 500°C. Up to 99.3% of the ammonia generated was easily separated from the syngas by condensation in the excess water. Experiments replacing the Ni-bed with Al₂O₃ pellets showed no significant H₂ yield, while the main H-product was overwhelmingly NH₃. Aqueous ammonia cracking experiments indicated a reaction further away from equilibrium than the equivalent urea–water experiments, indicative of a hydrogen formation mechanism from urea to water that was more than just a sequence of urea decomposition, HNCO hydrolysis and NH₃ cracking. Looking for signs of deactivation, the catalyst was characterised with N₂ adsorption, TEM–EDX, and powder XRD. NiO was shown to be present in negligible amounts after the experiments, while crystallite sizes and surface area were not affected significantly, and no coking was observed, evidencing a robust catalyst for this reaction.

Keywords: Urea; Ammonia; Water; Hydrogen; Nickel

Titanium dioxide photocatalysis to decompose isopropyl methylphosphonofluoridate (GB) in gas phase by Keita Sato; Tsutomu Hirakawa; Asuka Komano; Shintarou Kishi; Chifumi K. Nishimoto; Nobuaki Mera; Masahiro Kugishima; Taizo Sano; Hiromichi Ichinose; Nobuaki Negishi; Yasuo Seto; Koji Takeuchi (pp. 316-322).

Display Omitted► Sarin (GB) quickly adsorbed at surface of TiO₂ and was decomposed by TiO₂ photocatalysis. ► Decontamination of vaporized GB was then strongly controlled by adsorption rate. ► The ability to decontaminate GB molecules on TiO₂ photocatalyst can be estimated to be 42 molecules/nm² which correspond to 17 layers/nm². ► Organic solvent which is coexistent with GB affects the TiO₂ photocatalytic decontamination rate, such as adsorption and decomposition.The adsorption and photocatalytic degradation of nerve agent, isopropyl methylphosphonofluoridate, Sarin (GB) as a real Chemical Warfare Agent (CWA) on powdery Titanium dioxide (TiO₂) film have been investigated using Gas chromatography/mass spectrometry (GC/MS) analysis in ambient atmosphere. We found that the ability to decontaminate GB molecules on TiO₂ photocatalyst can be estimated to be 42 molecules/nm², indicating that 1g of TiO₂ photocatalyst can decontaminate 3.4mmol of GB molecules as the limitation value to maintain the photocatalytic activity. We also elucidated a plausible photocatalytic decontamination mechanism of GB at the surface of TiO₂ photocatalyst on the basis of the results obtained in this study.

Keywords: Titanium dioxide; Sarin; GB; CWA; Photocatalytic decontamination

Conventional versus lattice photocatalysed reactions: Implications of the lattice oxygen participation in the liquid phase photocatalytic oxidation with nanostructured ZnO thin films on reaction products and mechanism at both 254nm and 340nm by Arshid M. Ali; Emma A.C. Emanuelsson; Darrell A. Patterson (pp. 323-336).

.Display Omitted► Relationship established between surface morphologies of thin film ZnO, reaction intermediates and products, and liquid phase and solid phase reaction mechanisms. ► Highest overall degradation rates occur with 340nm UV irradiation with highly aligned, more defect free nanostructured morphologies. ► Competition between two different photocatalytic mechanisms: conventional photocatalysed radical oxidation and lattice oxygen driven oxidation. ► Dominant reaction mechanism depends on the thin film morphology, crystallinity, availability of oxidant and the wavelength of the incident UV.This study aimed to investigate the relationship between surface morphologies of nanostructured ZnO thin films, the reaction intermediates and products produced, and the liquid phase and solid phase reaction mechanisms under both oxygen rich and oxygen limited conditions at two different wavelengths (254nm and 340nm). Four different ZnO morphologies were prepared by hydrothermal deposition on two different substrates – clean glass (CG) and direct current magnetron sputtered ZnO glass (MS). The two films grown on the MS templates were highly vertically aligned columnar structures and those grown without templates (CG) had little or no structural alignment. Methylene blue (MB) was used as the reactant, since its reaction intermediates and products are well defined and measurable, allowing predictable comparison between these catalysts.Results showed that there was a significant difference in MB degradation rates as well as reaction intermediate formation and destruction rates correlated to the morphologies and crystallinity at both UV wavelengths, with the highest reaction rates at 340nm. Reaction analysis indicates that there may be a competition between two different photocatalytic mechanisms: conventional photocatalysed radical oxidation and lattice oxygen driven oxidation. The dominant reaction mechanism present depended on the thin film morphology, crystallinity, availability of oxidant and the wavelength of the incident UV. The surface photocatalysed radical formation is thought to be predominant for more highly aligned and more crystalline morphologies, where there was plentiful oxygen and UV irradiation at 340nm. Lattice oxygen photodegradation is thought to be predominant for less aligned more amorphous morphologies and UV irradiation at 254nm. Based on these results a new MB ZnO photocatalysed oxidation mechanism is proposed.

Keywords: Photocatalysis; Zinc oxide; Morphology; Reaction mechanism; Methylene blue; Mars–Van Krevelen

On the mechanism of enhanced photocatalytic activity of composite TiO₂/carbon nanofilms by Raja Sellappan; Augustinas Galeckas; Vishnukanthan Venkatachalapathy; Andrej Yu. Kuznetsov; Dinko Chakarov (pp. 337-342).

Display Omitted► Designed and fabricated model photocatalyst systems of TiO₂ and graphitic carbon. ► Charge carrier dynamics obtained from photoluminescence (PL) measurements. ► The higher photocatalytic activity is primarily related to charge carrier leakage.In the search for the origin of the enhanced photocatalytic activity of composite TiO₂–carbon systems, we have fabricated and analyzed well-defined model samples consisting of anatase and graphitic carbon with and without modifying the interface between them by a thin SiO₂ space layer. The films with a TiO₂/C interface show noticeably lower photoluminescence intensity and shorter carrier life times compared to single TiO₂ films with the same thickness and composition. The stronger non-radiative recombination is mainly assigned to charge carrier leakage (transfer) at the interface between TiO₂ nanocrystallites and the carbon film.

Keywords: Photocatalysis; TiO; ₂; –carbon composites; Photoluminescence; Charge carriers lifetime; Charge transfer mechanism

Oxidative desulfurization of dibenzothiophene with dioxygen and reverse micellar peroxotitanium under mild conditions by Caiyun Jiang; Jingjing Wang; Shengtian Wang; Hong yu Guan; Xiaohong Wang; Minxin Huo (pp. 343-349).

The reverse micellar peroxotitanium-containing catalyst [C₁₈H₃₇N(CH₃)₃]₇[PW₁₀Ti₂O₃₈(O₂)₂] was assembled in organic solvent decalin. Direct oxidation of dibenzothiophene (DBT) with O₂ was performed by this reverse micellar catalyst, which exhibits high selectivity and activity in the oxidation of DBT to sulfone with ∼100% selectivity and could catalytically decrease sulfur level in diesel from 500ppm to 1.0ppm at ambient pressure and moderate temperature.Display Omitted► The reverse micellar peroxotitanium-containing catalyst [C₁₈H₃₇N(CH₃)₃]₇[PW₁₀Ti₂O₃₈(O₂)₂] was assembled and characterized. ► Direct oxidation of dibenzothiophene with O₂ was performed by the reverse micellar catalyst. ► Direct oxidation of dibenzothiophene exhibits high selectivity and activity in the oxidation of DBT to sulfone with ∼100% selectivity. ► Direct oxidation of dibenzothiophene could catalytically decrease sulfur level in diesel from 500ppm to 1.0ppm at ambient pressure and moderate temperature.The reverse micellar peroxotitanium-containing catalyst [C₁₈H₃₇N(CH₃)₃]₇[PW₁₀Ti₂O₃₈(O₂)₂] was assembled in the organic solvent and the structure was characterized by Fourier transform infrared spectroscopy(FT-IR), Diffuse reflectance UV–vis spectrum (DR-UV–vis), X-ray photoelectron spectrum (XPS), transmission electron microscopy (TEM), Energy dispersive X-ray analysis (EDAX), and Matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry. Direct oxidation of dibenzothiophene (DBT) using O₂ was performed by this reverse micellar catalyst with ∼100% selectivity in the oxidation of DBT to sulfone. By this catalyst, it could catalytically decrease sulfur level in diesel from 500ppm to 1.0ppm at ambient pressure and moderate temperature.

Keywords: Desulfurization; Dibenzothiophene; Polyoxometalates; Reverse-micelles; Oxidation

A study of the effect of microwave treatment on metal zeolites and their use as photocatalysts toward naptalam by Sofian M. Kanan; Naser Abdo; Maham Khalil; Xiaobo Li; Imad A. Abu-Yousef; Francois Barilrobert; Howard H. Patterson (pp. 350-358).

Display Omitted► We have developed a novel highly active catalyst for the photodegradation of the pesticide naptalam. ► This catalyst is prepared by doping Ag and Au nanoparticles into Y zeolite and then digested by microwave treatment. ► The microwave process, which enhances the formation of mixed Ag and Au nanoclusters, is crucial for the catalytic activity. ► The largest catalytic activity was observed for the AgAuYm catalyst where a 20-fold increase in the decomposition rate was observed. ► The untreated sample (Ag-AuY) provides a selective surface that completely adsorbs naptalam from solution.A new route to fabricate silver and gold-based material incorporated into the Y zeolite framework is reported. X-ray fluorescence (XRF), X-ray photoelectron spectroscopy (XPS), UV–vis diffuse reflectance, and low-temperature steady-state photoluminescence spectroscopic results indicate the formation of metallic silver and gold as well as ionic clusters on the zeolite framework. Microwave treatment affects the surface morphology and the metal content of different catalyst systems. The photodecomposition of the pesticide naptalam is enhanced in the presence of silver and gold exchanged into zeolite Y catalysts. The largest catalytic activity was observed for the AgAuYm catalyst where an increase in the decomposition rate by 20-fold was observed compared to the uncatalyzed irradiated naptalam solution. While the microwave treated mixed sample (Ag-AuYm) acts as a good catalyst for the degradation of naptalam, the untreated sample (Ag-AuY) provides a selective surface that completely adsorbs naptalam from solution. GC–MS, HPLC, and synchronous scan luminescence spectra (SSLS) results show the formation of three products namely, α-naphthylamine, phthalic acid, and N-1-naphthylphthalimide for the photodecomposition of naptalam irradiated at 254nm in aqueous solution. This is in contrast to the catalyzed reactions where N-1-naphthylphthalimide is the major product.

Keywords: Naptalam; Silver; Gold; Nanoclusters; Zeolite; Microwave treatment; Catalysts

The effect of zirconia additive on the activity and structure stability of V₂O₅/WO₃-TiO₂ ammonia SCR catalysts by Anju Shi; Xinquan Wang; Tie Yu; Meiqing Shen (pp. 359-369).

Display Omitted► ZrO₂ improves thermal stability and activity of aged V₂O₅/WO₃-TiO₂ SCR catalyst. ► This durability results from diffusion barriers by ZrO₂ and Zr_xTi1−_xO₂ formation. ► Increased surface acid strength by ZrO₂ contributes to high temperature SCR activity. ► Kinetic study shows ZrO₂ does not change reaction mechanism of V₂O₅/WO₃-TiO₂ catalyst.The NH₃-SCR activities of zirconia containing V₂O₅/WO₃-TiO₂ catalysts have been studied before and after aging treatment. On fresh catalysts, the addition of zirconia increases high temperature activity and N₂ selectivity but decreases low temperature activity. Interestingly, zirconia prominently enhances the NH₃-SCR activities of aged catalysts, with 10wt% ZrO₂ containing catalyst exhibits the highest NO conversions and N₂ selectivity in the temperature range of 150–550°C. The catalysts were characterized by XRD, SEM, XPS, DRIFTS and NH₃-TPD. SCR kinetic studies were also conducted to understand the mechanistic features of the zirconia modified catalysts. The main results show that the addition of zirconia inhibits the shrinking of catalyst surface area and the growth of TiO₂ crystallite size, and therefore improves the thermal stability of V₂O₅/WO₃-TiO₂ catalysts. These advantages of zirconia additive can essentially benefit the catalysts performance with high temperature durability.

Keywords: Ammonia SCR; Vanadia-tungsta-titania catalysts; Zirconia; Thermal stability; Nitrogen selectivity

Oxidative degradation of azo dye by hydrogen peroxide electrogenerated in situ on anthraquinonemonosulphonate/polypyrrole composite cathode with heterogeneous CuO/γ-Al₂O₃ catalyst by Guoquan Zhang; Shuai Wang; Sha Zhao; Lei Fu; Guohua Chen; Fenglin Yang (pp. 370-378).

Display Omitted► AQS/PPy composite can cause efficient electrocatalytic reduction of O₂ to produce H₂O₂. ► Heterogeneous CuO/γ-Al₂O₃ catalyst can efficiently activate H₂O₂^{to produce}OH. ► Heterogeneous electrocatalytic oxidation of dye follows the second-order kinetics. ► Heterogeneous CuO/γ-Al₂O₃ catalyst can be recovered and reused.Heterogeneous electrocatalytic wet H₂O₂ oxidation technique for the removal of azo dye amaranth from aqueous solution was studied in the presence of solid CuO/γ-Al₂O₃ catalyst and anthraquinonemonosulphonate/polypyrrole (AQS/PPy) composite cathode able to electrogenerate H₂O₂ in situ. The spherical CuO/γ-Al₂O₃ catalysts with various CuO loadings and calcined at different temperatures were characterized by BET, ESEM-EDS, XRD and XPS. Several parameters affecting H₂O₂ electrogeneration and dye degradation such as solution pH, cathode potential ( E_ca), oxygen flow rate(VO2), CuO loading, reaction temperature as well as catalyst calcination temperature were investigated. Experimental results revealed that the optimal condition for H₂O₂ electrogeneration on the AQS/PPy composite modified cathode isVO2=0.4 ml min−1, E_ca=−0.4V and pH 4.3. On this occasion, ca. 90% chroma decay and 60% TOC removal of dye were achieved with 450°C-calcined 5.78wt%-CuO/γ-Al₂O₃ catalyst and 70°C reaction temperature. Dye degradation follows the second-order kinetics. Leaching tests showed that the leaching copper amount during the oxidation is only 4.0–7.0% per run and the role of heterogeneous activity is dominant. The catalytic activity of CuO/γ-Al₂O₃ catalyst could be recovered after multiple runs by a re-calcination step. Furthermore, the stability of the AQS/PPy composite after consecutive operation was also investigated by chronoamperometric and EIS techniques.

Keywords: Anthraquinone; Copper oxide; EAOPs; Heterogeneous; Hydroxyl radical

Preparation and characterization of Pt on modified multi-wall carbon nanotubes to be used as electrocatalysts for high temperature fuel cell applications by A. Orfanidi; M.K. Daletou; S.G. Neophytides (pp. 379-389).

Display Omitted► Towards the development of catalytic layers with increased catalyst utilization. ► Introduction of pyridine groups on MWCNTs by surface covalent functionalization. ► Optimization of Pt deposition by reduction of its salt in ethylene glycol solution. ► Uniformly dispersed Pt catalysts with particle size in the range of 2.5–4nm.A new approach towards the development of electrocatalytic layers for use in high temperature polymer electrolyte membrane fuel cells (PEMFCs) is reported. Modified carbon nanotubes were used as the support. The aim was to achieve a uniform distribution of polar groups, which can interact with phosphoric acid, on the surface of the modified carbon support. Multi-wall carbon nanotubes were selected due to their unique properties regarding electronic conductivity and specific surface area. They were surface modified introducing pyridine based groups on the side walls which are known to interact with phosphoric acid. The different supports were thoroughly characterized by means of relevant techniques such as Raman and XPS. Platinum was deposited on the new carbon supports resulting in the newly synthesized catalysts, which were also thoroughly characterized by means of XRD, EDX, TEM and H₂ Chemisorption. Stable and finely distributed Pt catalysts with nanoparticles size ranging between 2 and 4nm were obtained using the chemically modified nanotubes as supports. Measurements of the catalytic activity towards oxygen reduction were also performed in order to evaluate the potential use of these materials as catalytic layers in PEMFCs.

Keywords: PEM fuel cell; Catalyst utilization; MWCNT functionalization; Pt deposition; Oxygen reduction reaction

The role of activated carbons functionalized with thiol and sulfonic acid groups in catalytic wet peroxide oxidation by Helder T. Gomes; Sandra M. Miranda; Maria J. Sampaio; José L. Figueiredo; Adrián M.T. Silva; Joaquim L. Faria (pp. 390-397).

Display Omitted► Activated carbons are successfully modified with thiol and sulfonic acid groups. ► Modified activated carbons show increased efficiency in CWPO of Chromotrope 2R. ► Higher acidic strength of modified activated carbons increases efficiency in CWPO. ► Thiol groups on activated carbons promote the production of hydroxyl radicals.Norit ROX 0.8 commercial activated carbon was subjected to liquid phase treatments with sulfuric acid at different concentrations (5–18M) and temperatures (353 and 423K), to generate different amounts (760–1000μmolg⁻¹) of sulfur groups (thiol and sulfonic acid), with varying surface acidity. The prepared materials were chemically characterized by the determination of the point of zero charge (2.0–5.8) and by mass titration, temperature programmed desorption and X-ray photoelectron spectroscopy, to evaluate the nature and concentration of acidic surface functionalities. The materials were tested as catalysts in the catalytic wet peroxide oxidation of aqueous solutions of the acid dye Chromotrope 2R. A correlation between the surface acidic strength and the efficiency for dye removal from solution was found, which was ascribed both to adsorption and to reaction. In general, dye removal by adsorption is increased when using adsorbents with lower acidic character, due to enhanced electrostatic attraction between the acid dye and the catalyst surface. In addition, the introduction of sulfur containing groups promotes the decomposition of hydrogen peroxide, leading to increased production of hydroxyl radicals close to the pollutant and subsequent improved dye degradation.

Keywords: Activated carbon; Surface chemistry; Sulfur containing functional groups; Thiols; Sulfonic acids; Catalytic wet peroxide oxidation

Hydroxyapatite/titanium dioxide nanocomposites for controlled photocatalytic NO oxidation by Anastasios Mitsionis; Tiverios Vaimakis; Christos Trapalis; Nadia Todorova; Detlef Bahnemann; Ralf Dillert (pp. 398-404).

Sample HT01 (with volume ratio TiO₂/HA=1:1) has not only photonic efficiency in NO oxidation twice bigger than pure TiO₂, but also higher efficiency in NO_x removal as well.Display Omitted► The composite with volume ratioVHA/VTiO2 equal to one demonstrated higherOH production than pure TiO₂. ► The photocatalytic activity in NO→NO₂ oxidation was higher for all composites in comparison to the pure components. ► The photocatalytic activity in the NO₂→NO₃⁻ oxidation was low for all composites except for the sample with volume ratioVHA/VTiO2 equal to one. ► The unique behavior of the HA/TiO₂ composites was attributed to the dispersion between the components and the influence of residual acidic groups due to the HA precipitation procedure applied.Biphasic photocatalytic powders consisted of hydroxyapatite (HA) and titanium dioxide (TiO₂) were prepared by precipitation of HA in presence of TiO₂ (Evonik-Degussa P25). Depending on the volume ratio between HA and TiO₂ in the initial solution the materials showed different textural properties. Aggregates consisted of spherical particles were formed at low HA/TiO₂ ratio, while the decrease of the TiO₂ amount resulted in formation of needle and lath like particles. The specific surface area (ssa) of the composites was higher than the ssa of the pure components and increased with the decrease of the TiO₂ amount. The novel materials exhibited excellent activity in photocatalytic NO oxidation, while the activity in NO₂ removal, either by oxidation or by adsorption to the HA, was extremely low for the composites with volume ratioVHA/VTiO2 more than 1. The selective behavior of these composites towards the two steps of the NO_x oxidation process was related to the preparation procedure followed. The composite with 50% (v/v) TiO₂ revealed higherOH formation ability and photocatalytic activity in overall NO_x removal than the pure TiO₂ component that was ascribed to the specificVHA/VTiO2 ratio and growth of HA on the TiO₂ surface.

Keywords: Hydroxyapatite; Titanium dioxide; Nanocomposites; Photocatalysis; NO oxidation

Catalytic hydroreforming of the polyethylene thermal cracking oil over Ni supported hierarchical zeolites and mesostructured aluminosilicates by J.M. Escola; J. Aguado; D.P. Serrano; A. García; A. Peral; L. Briones; R. Calvo; E. Fernandez (pp. 405-415).

Display Omitted► The liquid from LDPE thermal cracking contains many unwanted olefins. ► These olefins were saturated by hydroreforming over Ni containing catalysts. ► Ni/h-Beta and Ni/h-ZSM-5 led towards the highest share of gasoline (54%). ► Ni/Al-MCM-41 and Ni/Al-SBA-15 yielded the highest share of light diesel (33%). ► RON index of the gasolines and cetane index of the diesel show promising values.The hydroreforming of the liquid product resulting from LDPE thermal cracking at 400°C (C₅–C₄₀) has been studied using Ni supported hierarchical zeolites (Ni/h-ZSM-5, Ni/h-Beta) and mesostructured materials (Ni/Al-MCM-41 and Ni/Al-SBA-15) as catalysts. Hydroreforming experiments were carried out at 310°C under 20bar of hydrogen. All the catalysts were synthesized with a Si/Al atomic ratio of 30 and a Ni content of 7wt%. According to XRD, TPR and TEM data, the activated catalysts displayed Ni particles both over the external surface and inside the catalyst pores in different percentages depending on their porous structure and nature. Complete hydrogenation of the olefins was observed over both mesostructured catalysts (Ni/Al-SBA-15 and Ni/Al-MCM-41) and hierarchical Ni/h-Beta. In contrast, over Ni/h-ZSM-5, there is always left about 30% of olefins, due to an imbalance in the acid and metal function. Ni/h-ZSM-5 led towards significant amounts of gases (∼18%) while gasoline range hydrocarbons were the main products (55%) over Ni/h-Beta, at the expense of diesel fractions. In contrast, the hydrocracking extent was far lower over Ni/Al-MCM-41 and Ni/Al-SBA-15, the latter showing additionally the appearance of a slight degree of oligomerization, which led towards an increase in the heavy diesel fraction (C₁₉–C₄₀). Hydroisomerization reactions also occur, mostly in the case of Ni supported hierarchical zeolites. Likewise, aromatics were formed over these catalysts in a large extent. The RON number of the gasolines obtained at 310°C was within 81–89 depending on the chosen catalysts while the cetane index (CCI) of the diesel fraction was around 70–80. On the other hand, Ni leaching was not detected.

Keywords: LDPE; Hydroreforming; Hierarchical zeolites; Al-MCM-41; Al-SBA-15

Direct nitrous oxide decomposition with CoO_x-CeO₂ catalysts by Ewa Iwanek; Krzysztof Krawczyk; Jan Petryk; Janusz W. Sobczak; Zbigniew Kaszkur (pp. 416-422).

Display Omitted► CoO_x-CeO₂ catalysts are more active in N₂O decomposition than Co₃O₄. ► Influence of feed composition on CoO_x-CeO₂ activity depends on Ce/Co ratio. ► Two types of CoO species form in the presence of ceria. ► Oxygen on CeO₂–CoO_x interface is important for the activity in N₂O decomposition.The focus of the performed studies were CoO_x-CeO₂ oxide catalysts for nitrous oxide decomposition. All CoO_x-CeO₂ systems exhibit similar or higher activity than the undoped cobalt catalyst. It has been found that in temperatures up to 800°C in a N₂O–Ar stream cobalt in these catalysts is in the form of Co₃O₄. At higher temperatures it is reduced to CoO. In a N₂O–O₂–Ar stream Co₃O₄ is the main cobalt-containing phase in the entire studied temperature range. The obtained results revealed that the activity of CoO_x-CeO₂ systems with a high cobalt loading increases with temperature only up to 800°C in a N₂O–Ar stream. Upon further temperature increase the activity of these catalysts decreases, as in the case of the undoped cobalt catalyst. This is due to the reduction of Co₃O₄ to CoO. Hence, when oxygen is present in the feed and cobalt is in the form of Co₃O₄, the activity is higher. In contrast, the activity of catalysts with the cobalt molar ratio no greater than 0.64 is the same in both N₂O–Ar and N₂O–O₂–Ar streams and increases with temperature in the entire studied range (700–850°C). It has been demonstrated that at 850°C in a N₂O–Ar stream CoO_x-CeO₂ systems contain two types of CoO, which require different conditions to be oxidized. This is a result of a different strength of interaction with CeO₂. It can be concluded that the activity of CoO_x-CeO₂ systems results from the activity of Co₃O₄ and of the cobalt oxide–ceria interface. The share of each component is determined by the cobalt content.

Keywords: Nitrous oxide decomposition; Co; ₃; O; ₄; -CeO; ₂; catalysts; Catalyst state; Reduction; Phase interface

Selective oxidation of glycerol with oxygen in a base-free aqueous solution over MWNTs supported Pt catalysts by Dan Liang; Jing Gao; Hui Sun; Ping Chen; Zhaoyin Hou; Xiaoming Zheng (pp. 423-432).

Display Omitted► Unique sized and highly dispersed Pt catalysts was prepared on S-pretreated MWNTs. ► Pt/S-MWNTs was active for selective oxidation of glycerol in base-free solution. ► Activation of glycerol on Pt/S-MWNTs was investigated via Raman. ► Cleavage of C–C bond in glycerol is low on Pt/S-MWNTs catalyst in base-free solution.Selective oxidation of glycerol with molecular oxygen was studied over different functionalized MWNTs supported Pt catalysts in base-free aqueous solution. N₂ adsorption, IR, Raman and SEM–EDS analysis confirmed that the tubular structure of MWNTs is stable during HNO₃ and H₂O₂ pretreatment and the surface of MWNTs was successfully functionalized by HNO₃, H₂O₂ and NH₂–CH₂–CH₂–SH. XRD, SEM and TEM analysis demonstrated that unique sized Pt particles formed on S-pretreated MWNTs. Pt/S-MWNTs catalyst with small Pt particles was more active than Pt/MWNTs, Pt/HNO₃-MWNTs and Pt/H₂O₂-MWNTs for glycerol oxidation in base-free aqueous solution. Free glyceric acid formed (with 68.3% selectivity and 90.4% conversion of glycerol) on Pt/S-MWNTs in base-free solution. While dihydroxyacetone formed firstly in an aqueous solution of NaOH/glycerol=2:1 and the cleavage C–C bonds (catalyzed by alkali) arise severely.

Keywords: Glycerol oxidation; Glyceric acid; Pt/MWNTs; Base-free; Raman

Catalytic conversion of wastes from the bioethanol production into carbon nanomaterials by Joner O. Alves; Chuanwei Zhuo; Yiannis A. Levendis; Jorge A.S. Tenório (pp. 433-444).

Display Omitted► Pyrolyzates of bioethanol production residues were generated in an inert environment. ► Using a low-cost catalyst, the gaseous pyrolyzates were converted into carbon nanomaterials. ► Bagasse pyrolyzates generated MWCNTs, whereas DDGS pyrolyzates generated nano-ropes. ► A hydrogen-enhanced bio-syngas is also generated using the low-cost catalyst.This work addressed the production of carbon nanomaterials (CNMs) by catalytic conversion of wastes from the bioethanol industry, in the form of either sugarcane bagasse or corn-derived distillers dried grains with solubles (DDGS). Both bagasse and DDGS were pyrolysed at temperatures in the range of 600–1000°C. The pyrolyzate gases were then used as CNM growth agents by chemical vapor deposition on stainless steel meshes, serving as both catalysts and substrates. CNM synthesis temperatures of 750–1000°C were explored, and it was determined that their growth was most pronounced at 1000°C. The nanomaterials produced from pyrolysis of bagasse were in the form of long, straight, multi-wall nanotubes with smooth walls and axially uniform diameters. Typical lengths were circa 50μm and diameters were in the range of 20–80nm. The nanomaterials produced from pyrolysis of DDGS were in the form of long, entangled, rope-like structures with rugged walls, and axially non-uniform diameters. Typical diameters were in the range of 100–300nm and their lengths were in the tens of microns. This process also produces a bio-syngas byproduct that is enriched in hydrogen.

Keywords: Nanomaterials; Catalysis; Pyrolysis; Bioethanol; Sugarcane bagasse; DDGS

Nanocomposite of Ag–AgBr–TiO₂ as a photoactive and durable catalyst for degradation of volatile organic compounds in the gas phase by Yanhui Zhang; Zi-Rong Tang; Xianzhi Fu; Yi-Jun Xu (pp. 445-452).

Ag–AgBr–TiO₂ nanocomposites can be used as highly active and durable photocatalyst toward the gas-phase degradation of volatile organic pollutants of aromatic benzene and non-aromatic acetone that are notorious volatile organic compounds (VOCs) present in indoor and outdoor air. Synergetic effects between Ag–AgBr and TiO₂ suggest that there is a wide scope to optimize the photocatalytic performance of Ag–AgX (X=Cl, Br and I) loaded onto different kinds of semiconductor supports. This in turn would advance the application of Ag–AgX-semiconductor nanocomposites as photocatalyst for the destruction of harmful or toxic VOCs in air that is of significant concern regarding environmental health.Display Omitted► Ag–AgBr–TiO₂ nanocomposites as photoactive and durable photocatalyst for degradation of volatile organic compounds (VOCs), benzene and acetone, in the gas phase. ► Ag–AgBr–TiO₂ exhibits enhanced activity and stability than bare TiO₂ toward degradation of VOCs. ► Loading of a few amount of Ag–AgBr onto TiO₂ offers a way to inhibit the deactivation of TiO₂ toward degradation of VOCs.The nanocomposites of Ag–AgBr–TiO₂ photocatalyst have been prepared by a simple deposition–precipitation method, which is used for the gas-phase degradation of volatile organic pollutants of aromatic benzene and non-aromatic acetone that are notorious volatile organic compounds (VOCs) present in indoor and outdoor air. A collection of joint techniques, including X-ray diffraction (XRD), transmission electron microscopy (TEM) and ultraviolet/visible diffuse reflectance spectra (UV/vis DRS) have been employed to determine the structure, morphology and optical properties of the as-prepared Ag–AgBr–TiO₂ nanocomposite. The presence of surface Ag species existed as Ag (0) and Ag (I) in Ag–AgBr–TiO₂ is confirmed by the analysis of X-ray photoelectron spectroscopy (XPS). The Fourier transformed infrared spectroscopy (FT-IR) analysis shows the enhanced chemical bonding of O–Ti and O–Ti–O after the deposition of AgBr and Ag species onto the surface of TiO₂. It is found that the Ag–AgBr–TiO₂ nanocomposite exhibits much higher photocatalytic activity and stability under both UV light and visible light irradiation as compared with that over commercial titania (Degussa P25) toward the gas-phase degradation of both aromatic benzene and non-aromatic acetone. The active radical species involved for degradation reactions over the Ag–AgBr–TiO₂ photocatalyst have been investigated by the spin-trapping electron paramagnetic resonance (EPR) spectra and theOH-trapping photoluminescence (PL) spectra. Synergetic effects between Ag–AgBr and TiO₂ have been observed and discussed for the gas-phase degradation of volatile organic compounds on the basis of joint results of characterization and photocatalytic activity.

Keywords: Photocatalytic degradation; Volatile organic compounds; Ag–AgBr–TiO; ₂; Synergetic effect

Effect of inorganic ions, H₂O₂ and pH on the photocatalytic inactivation of Escherichia coli with silver impregnated combustion synthesized TiO₂ catalyst by Sharad Sontakke; Jayant Modak; Giridhar Madras (pp. 453-459).

Display Omitted► Effect of ions, H₂O₂ and pH on photocatalytic inactivation of Escherichia coli with Ag/TiO₂. ► Addition of ions shows negative effect on the inactivation. ► H₂O₂ addition improves the inactivation of E. coli. ► The inactivation remains unaffected by variation in pH.The photocatalytic antibacterial activity of Ag impregnated combustion synthesized TiO₂ (0.25g/L) was studied against Escherichia coli in presence of UV irradiation. The effect of various parameters, such as anions, cations, hydrogen peroxide and pH, on the photocatalytic inactivation was investigated. The addition of inorganic ions showed a negative effect on inactivation. Among anions, the presence of chloride ions was observed to have a maximum negative effect and reduced the inactivation considerably. Among cations, the bacterial inactivation reduced significantly in the presence of Ca²⁺ ions. Hydrogen peroxide addition in combination with Ag/TiO₂ photocatalysis, however, improved the inactivation. Photocatalysis with high concentration of H₂O₂ yielded complete bacterial inactivation within few minutes. The photocatalytic inactivation of E. coli was not affected by variation in pH.

Keywords: Photocatalysis; Escherichia coli; Combustion synthesis; Ag/TiO; ₂; Anions; Cations; H; ₂; O; ₂; pH

2.8NiO–H_1.8Ni_0.6(OH)MoO₄—Novel nanocomposite material for the reactive adsorption of sulfur-containing molecules at moderate temperature by Jonathan Skrzypski; Igor Bezverkhyy; Olga Safonova; Jean-Pierre Bellat (pp. 460-468).

We report preparation of novel mesoporous nanocomposite 2.8NiO–H_1.8Ni_0.6(OH)MoO₄ consisting of Ni–Mo (hydr)oxide layers pillared with NiO particles. Due to enhanced HDS activity the material exhibits much higher reactivity towards sulfur-containing molecules than Ni/ZnO.Display Omitted► New layered material is synthesized: 2.8NiO–H_1.8Ni_0.6(OH)MoO₄. ► The material is mesoporous with BET surface area of 230m²/g. ► NiO nanoparticles play the role of pillars between the Ni molybdate layers. ► In H₂ flow at 300°C the solid is reduced to Ni_3.4Mo nanoparticles. ► The solid reacts with thiophene at 300°C 10 times faster than Ni/ZnO.It has been found that a poorly crystalline green precipitate that forms in boiling ammonia solution of Ni(NO₃)₂ and (NH₄)₆Mo₇O₂₄ yields on annealing a Ni-rich material (Ni/Mo=3.4) containing slit shaped mesopores and exhibiting the BET surface area of 230m²/g. Characterization of the material by TGA, XRD, TEM, SEM, and EXAFS allowed to determine that it is a nanocomposite consisting of Ni–Mo (hydro)oxide layers H_1.8Ni_0.6(OH)MoO₄ which are pillared by NiO nanoparticles ( D=3nm). The structure of the layers appears to be similar to that found in the previously described crystalline molybdate (NH₄)HNi₂(OH)₂(MoO₄)₂ prepared in the similar conditions. The obtained nanocomposite 2.8NiO–H_1.8Ni_0.6(OH)MoO₄ can be completely reduced in H₂ flow at 300°C yielding unsupported Ni_3.4Mo bimetallic nanoparticles ( D=3.6nm) which are stable towards sintering. The material shows remarkable activity in a moderate temperature reactive adsorption of thiophene: at 300°C the rate of its sulfidation in the presence of thiophene is an order of magnitude higher than that of conventional Ni/ZnO sorbent. Such increase of activity is attributed to formation (after partial sulfidation) of the mixed Ni–Mo–S phase, which is known to be highly active in catalytic hydrodesulfurization of sulfur-containing molecules. Also, due to its open structure the nanocomposite reacts rapidly and completely with H₂S even at 200°C, while only the surface sulfidation is observed for ZnO nanoparticles under the same conditions.

Keywords: Ni molybdate; Ni–Mo mixed oxide; Thiophene reactive adsorption; H; ₂; S removal; Oxide sulfidation

Comparison of activated carbon-supported Pd and Rh catalysts for aqueous-phase hydrodechlorination by Elena Diaz; Angel F. Mohedano; Jose A. Casas; Luisa Calvo; Miguel A. Gilarranz; Juan J. Rodriguez (pp. 469-475).

Display Omitted► A higher activity and stability was exhibited by Pd and Rh/AC own-made catalysts. ► Rh catalysts showed a high selectivity to the most advisable product. ► The highest activity was associated with metal particle sizes within 3–4nm. ► The HDC reaction with these catalysts is structure sensitivity.Different commercial and own-made catalysts, synthesized by incipient wetness impregnation, based on Pd and Rh supported on activated carbon have been investigated for hydrodechlorination (HDC) in aqueous phase using 4-chlorophenol as target compound at 100mg/L starting concentration. The experiments were performed in a continuous stirred basket tank reactor at 30°C and 1atm, fairly mild conditions for a potential application to industrial wastewater. Although all the catalysts tested showed a high dechlorination activity (X_4-cp≥95% except for the commercial Rh/AC catalyst) which remained practically stable during long-term experiments, the own-made catalysts yielded a higher selectivity (>40%) to the most hydrogenated reaction products, cyclohexanone and cyclohexanol. This last is by far the main reaction product with the own-made Rh catalyst, which is important given its lower toxicity and higher biodegradability. The highest catalytic activity was associated with metal particle sizes within the 3–4nm range, indicating that the HDC reaction with these catalysts is structure sensitive. Modification of the surface composition of the active carbon support upon HNO₃ oxidation entailed a more homogeneous distribution of the active phase with improved metallic dispersion. However, the catalyst with the smallest metal particle (<2nm) was not the most active, resulting these particle sizes less effective for HDC.

Keywords: Hydrodechlorination; 4-Chlorophenol; Pd and Rh carbon supported catalysts; Structure sensitivity

Autothermal reforming of low-sulfur diesel over bimetallic RhPt supported on Al₂O₃, CeO₂–ZrO₂, SiO₂ and TiO₂ by Xanthias Karatzas; Kjell Jansson; Angélica González; Jazaer Dawody; Lars J. Pettersson (pp. 476-487).

Display Omitted► ATR of low-sulfur diesel. ► Incipient wetness (IW) prepared catalysts; RhPt supported on alumina, ceria–zirconia, silica and titania. ► RhPt/CeO₂–ZrO₂ most active; a diesel conversion close to 98% obtained. ► Possible correlation between the diesel conversion and the reducibility of Rh_iO_x species remarked. ► Highest reducibility of Rh_iO_x species, using H₂-TPR, noticed for RhPt/CeO₂–ZrO₂.The objective of this paper is to study and clarify the role of selected supports (both reducible and non-reducible) on the activity, selectivity and stability of RhPt-based catalyst for diesel reforming. Autothermal reforming (ATR) of low-sulfur diesel (S ∼6ppm, C/H ∼6.43 (w/w)), H₂O/C ∼2.5, O₂/C ∼0.49, was tested at bench scale to detect differences in activity for catalysts consisting of 1wt% Rh and 1wt% Pt supported on alumina, ceria–zirconia (17.5wt% ceria), silica and titania. Promoters in the form of MgO, Y₂O₃, La₂O₃, CeO₂ and ZrO₂, ranging from 4wt% to 10wt%, were also added onto the supports to detect differences in catalyst activity in terms of diesel conversion, CO₂ selectivity, and hydrogen and ethylene production. All metals were added sequentially onto the support by the incipient wetness technique and washcoated on 400cpsi cordierite monolithic carriers with dimensions d=17.8mm, l=30.5mm.The product gas analysis, using FTIR and NDIR, showed that RhPt/CeO₂–ZrO₂ was found to be most active for ATR of diesel since a fuel conversion close to 98% was obtained. Furthermore, the catalyst activity of the unpromoted samples, in terms of diesel conversion, increased in the following order: RhPt/SiO₂22O₃2–ZrO₂. The addition of promoters was found to be insignificant as well as having a negative impact on the catalyst performance in most cases, except for the alumina-promoted sample. The addition of 10wt% La₂O₃ on RhPt/Al₂O₃ was found to enhance diesel conversion, hydrogen productivity as well as lower the ethylene concentration from 3700ppm to less than half that value. The latter observation was confirmed by O₂-TPO analysis of aged powder samples where lower loads of coke were present than on the La-promoted sample.The morphology, surface and bulk properties of RhPt/CeO₂–ZrO₂ were closely examined in order to provide a possible correlation between the activity and characterization results. N₂-BET analysis showed that the surface area of RhPt/CeO₂–ZrO₂ was ∼64m²/g, while the silica samples exhibited the highest area, ∼137–185m²/g. Hence, the difference in the surface areas was not enough to explain the trends observed in the activity measurements. XRD analysis of RhPt/CeO₂–ZrO₂ showed crystalline phases characteristic of zirconia, most likely tetragonal. Also, the diffractogram did not reveal any Rh or Pt peaks indicating that the noble metal particles are highly dispersed on the support. In contrast, peaks ascribed to metallic Pt (∼30–46nm) were clearly visible on the XRD patterns taken from all the other supported samples. H₂-TPR analysis of RhPt/CeO₂–ZrO₂ showed reduction peaks ascribed to Rh_iO_x species as well as a minor hydrogen spillover effect on the support to be present at T=120°C and 450°C, respectively. Also, the hydrogen consumption of the Rh_iO_x species was the highest compared to the other supported RhPt samples. TEM analysis performed on fresh RhPt/CeO₂–ZrO₂ showed that the Rh_iO_x and Pt particles were highly dispersed on the support, both with particle sizes in the vicinity of ∼5–15nm. Rh species was found on ceria and zirconia, while Pt was present mainly on the ceria layer possibly in the form of Pt–O–Ce bonds. H₂-chemisorption analysis measured at T ∼40°C shows similar Rh dispersion results.To summarize, the higher activity results of RhPt/CeO₂–ZrO₂ for ATR of diesel, compared to other supported catalysts, may be ascribed to the higher reducibility of Rh_iO_x species as well as the superior Rh and Pt dispersion. Also, the support contribution, in particular ceria, is believed to promote water gas-shift activities as well as reduce coke deposits on the catalyst surface.

Keywords: Alumina; Ceria–zirconia; Diesel reforming; Rhodium–platinum; Silica; Titania

Renewable fine chemicals from rice and citric subproducts: Ecomaterials by M.A. Martin-Luengo; M. Yates; M. Diaz; E. Saez Rojo; L. Gonzalez Gil (pp. 488-493).

Display Omitted► Limonene (or orange peel oil) to oxygenates. ► Rice derived silica and FeO_x. ► Sustainable technology.A vast amount of work has been carried out regarding the preparation of fine chemicals, with oxidation being one of the main paths followed. Based on those literature data, renewable value added chemicals were prepared in this work using solid and liquid agro-industrial wastes from rice and citrus production, as renewable raw materials, avoiding the use of substances toxic to the environment and achieving a reduction in energy expenditure. The whole process is consistent with a sustainable development.A combination of catalysts based on rice husk derived silica (RHS), iron oxide as source of active basic sites that act as antennae for dielectric heating, allows an environmentally sound transformation of limonene, a byproduct of the citrus industry, into value-added chemicals, which are also renewable, given their origin. Thus, the present investigation has demonstrated how the transformation of a low value subproduct into high value materials can be achieved with similar conversions and selectivities to those found in the literature for catalysts that have higher toxicities and are less environmentally friendly. Through the use of dielectric heating the process is rapid and thus avoids the formation of unwanted secondary byproducts and furthermore the energy requirements are greatly reduced.

Keywords: Renewable raw materials; Fine chemicals intermediates; Waste; Sustainable development; Rice husk silica; Ecomaterials; Citrus juice waste; Limonene; Carvone; Carveol; Limonene oxide; Carvacrol

Influence of thermally induced structural changes of 2wt% Pd/LaFeO₃ on methane combustion activity by Arnim Eyssler; Alexander Winkler; Peter Mandaliev; Paul Hug; Anke Weidenkaff; Davide Ferri (pp. 494-502).

Display Omitted► Calcination of Pd/LaFeO₃ at T_calc=300, 500, 700, 1000°C creates two Pd species. ► Pd is present as Pd²⁺ within surface PdO and Pd n⁺ ( n>2) in solid solution with LaFeO₃. ► The Pd²⁺/Pd n⁺ ratio is determined by T_calc and influences catalytic CH₄ oxidation. ► CH₄ oxidation between 200 and 900°C also changes Pd²⁺/Pd n⁺ due to the PdO↔Pd equilibrium. ► Pd/LaFeO₃ ( T_calc=500°C) has stronger PdO high temperature stability than Pd/Al₂O₃.The influence of the calcination temperature on the structure and catalytic activity of 2wt% Pd/LaFeO₃ for methane combustion has been investigated. LaFeO₃ (calcined at 700°C) was impregnated with Pd(NO₃)₂ and subsequently calcined at temperatures between 300°C and 1000°C. Characterization using TPR, XPS, DRIFTS and XAS revealed the presence of Pd in at least two different coordination environments. A fraction of Pd²⁺ in PdO-like particles coexists with Pd n⁺ ( n>2) dissolved in LaFeO₃. The relative fraction of the two species appears to change depending on the calcination temperature as a result of incorporation of Pd into LaFeO₃. The effect of this variation is discussed in relation to the catalytic activity.Pd/LaFeO₃ calcined at 500°C exhibited the best methane combustion activity during a heating-cooling cycle performed in the temperature range of 200–900°C. The strong interaction between Pd and LaFeO₃ renders Pd/LaFeO₃ calcined at 500°C stable against repeated cycles of thermal aging under the reactants atmosphere. At high temperature the relative distribution of Pd²⁺ and Pd n⁺ species and therefore catalytic activity are further affected by the occurrence of the thermal PdO↔Pd equilibrium suggested by the activity loss during the cooling segment.

Keywords: Catalytic combustion; Methane; Palladium; LaFeO; ₃; Thermal aging

Ultra-low loading Pt–Rh/Sn_0.9In_0.1P₂O₇ three-way catalyst for propane+NO+O₂ reaction by Xue Dong; Kota Tsuneyama; Takashi Hibino (pp. 503-509).

Display Omitted• Propane oxidation and NO reduction at the interface of a proton-conducting Sn_0.9In_0.1P₂O₇ and a Pt electrocatalyst were investigated. • H₂O dissociated into protons and electrons at an anodic site of the interface and the resultant active oxygen oxidized propane to CO₂. • NO reacted with protons and electrons to form N₂O at a cathodic site of the interface.Propane oxidation and NO reduction at the proton conductor–electrocatalyst interface were investigated using electrochemical cells and impregnated catalysts. Sn_0.9In_0.1P₂O₇ and Pt or Pt–Rh were used as the proton conductor and electrocatalyst, respectively. In a gaseous mixture of propane, H₂O, and NO, H₂O is dissociated into protons and electrons at anodic sites at the interface and the resultant active oxygen oxidizes propane to CO₂. Separately, NO reacts with protons and electrons to form N₂O at cathodic sites at the interface. Under stoichiometric conditions, including 1000ppm propane, 1000ppm NO, 3% H₂O, and 4500ppm O₂, the temperatures at which the above series of reactions could successfully achieve 50% conversion ( T_50%) was reduced to 310 and 385°C for propane and NO, respectively, over a 0.01wt.% Pt/Sn_0.9In_0.1P₂O₇ catalyst. These were much lower than T_50% of 430 and 535°C for propane and NO, respectively, over a 0.01wt.% Pt/γ-Al₂O₃ catalyst. Moreover, the addition of 0.005wt.% Rh to the Pt/Sn_0.9In_0.1P₂O₇ catalyst enhanced NO reduction by promoting the dissociative adsorption of NO, thus providing a further reduction of T_50% for the NO reaction to 355°C.

Keywords: Three-way catalyst; Ultra-low Pt and Rh content; Proton conductor; Propane oxidation; NO reduction

Adsorption and dissociation of ammonia on clean and metal-covered TiO₂ rutile (110) surfaces: A comparative DFT study by Daojian Cheng; Jianhui Lan; Dapeng Cao; Wenchuan Wang (pp. 510-519).

Display Omitted• Comparative study on dissociation of NH₃ on clean and Pt-covered TiO₂ surfaces. • Pt adatom on rutile TiO₂ enhances the adsorption of the species. • Pt adatom on rutile TiO₂ can vary the reaction pathways of NH₃ dissociation.We have used density functional theory (DFT) to investigate the adsorption and first dissociation step of ammonia on both clean and Pt-covered TiO₂ rutile (110) surfaces. On clean rutile TiO₂ (110) surface, NH₃ and NH₂ prefer to chemisorb on the five-coordinated titanium (Ti5c) site, and H is adsorbed favorably on the bridging oxygen (O1) site, while a single Pt atom prefers to adsorb on the hollow (H2) site. It is found that the preadsorbed Pt atom enhances significantly the adsorption of NH₃, NH₂ and H species on rutile TiO₂ (110) surface by binding with Pt adatom directly. It is also found that the first dissociation step of ammonia (NH₃≥NH₂+H) on the clean rutile TiO₂ (110) surface is endothermic by 0.89eV, and no transition state exists. In addition, the first dissociation step of ammonia on Pt-covered rutile TiO₂ (110) surface is found to be endothermic by only 0.43eV, but presents an activation energy barrier of 1.82eV. A comparison of the adsorption and first dissociation step of ammonia on rutile TiO₂ (110) surface with and without Pt adatom has been discussed. Investigations indicate that the adsorbed Pt adatom on clean rutile TiO₂ (110) surface not only changes the surface electron structure, but also varies the reaction pathways by participating in the reaction. It is expected that our results would provide useful information for the development of catalyst for NH₃ dissociation.

Keywords: PACS; 68.43.Bc; 82.45.Jn; 82.65.+rRutile TiO; ₂; Dissociation of ammonia; Platinum; DFT calculation

An FTIR study of Rh-PtSn/C catalysts for ethanol electrooxidation: Effect of surface composition by S. García-Rodríguez; S. Rojas; M.A. Peña; J.L.G. Fierro; S. Baranton; J.M. Léger (pp. 520-528).

Display Omitted• Ethanol electrooxidation is promoted on Rh-modified Pt₃Sn/C electrocatalysts. • The production of CO₂ is not greater on those electrodes as compared to Pt₃Sn/C. • The higher activity accounts to a higher production of acetic acid and acetaldehyde.The effect of adding various amounts of Rh to a carbon-supported Pt₃Sn electrocatalyst for the electrooxidation of ethanol is evaluated by electrochemical methods and single potential alteration infrared reflectance spectroscopy (SPAIRS). This technique was used to identify intermediate species and the final products of ethanol electrooxidation and to track their evolution with the reaction potential. Rh addition to Pt₃Sn/C was accomplished by impregnation, and this process resulted in Rh-modified catalysts of controlled composition. The Pt₃Sn stoichiometry of the original sample was maintained after Rh addition, as demonstrated by analysis with X-ray diffraction (XRD) and transmission electron microscopy (TEM). The selectivity for partially oxidized products, acetaldehyde and acetic acid is promoted on the Rh-PtSn/C electrocatalysts; however, the electrooxidation of ethanol to CO₂ is only marginally promoted by the addition of Rh to PtSn/C. The higher production of acetic acid on the Rh-modified PtSn/C electrodes, rather than the production of CO₂, is responsible for the higher current density recorded during the electrooxidation of ethanol on Rh-PtSn/C.

Keywords: Ethanol electrooxidation; Rh; Pt; ₃; Sn; SPAIRS; EC-FTIR

Effect of Ti(IV) loading on CH₄ oxidation activity and SO₂ tolerance of Pd catalysts supported on silica SBA-15 and HMS by A.M. Venezia; G. Di Carlo; L.F. Liotta; G. Pantaleo; M. Kantcheva (pp. 529-539).

Display Omitted• Ti(IV) enhances the silica HMS total acidity inducing Brønsted acid sites. • Direct synthesis of Ti xSBA-15 gives rise to segregation of anatase TiO₂. • Superior CH₄ combustion activity and SO₂ tolerance of Pd supported on Ti xSBA-15. • The creation of Bronsted acid sites are detrimental for Pd/Ti xHMS catalysts.Pure silica SBA-15 and HMS and corresponding Ti(IV) modified mesoporous silica, with 5 and 10wt% of TiO₂, were prepared and used as support for palladium (1wt%) catalysts. The materials, analysed by XPS, XRD, BET, NH₃-TPD and FT-IR techniques, were tested in the total oxidation of methane. The catalytic activity was measured in lean conditions at WHSV=60,000mlg⁻¹h⁻¹ in the absence and presence of 10vol.ppm SO₂. Moreover, the effect of a prolonged reaction aging and severe SO₂ poisoning on the catalytic performance of the best performing catalyst was investigated. The addition of TiO₂ improved the catalytic performance of the SBA-15 supported catalysts by increasing the sulfur tolerance and most importantly by favoring the regeneration of the catalyst in subsequent SO₂-free runs. An opposite behavior was observed with the palladium supported on Ti(IV)-modified HMS support which exhibited lower activity and a substantial worsening of the SO₂ tolerance as compared to palladium supported on pure HMS. On the bases of the structural and chemical investigation, the differences between the two series of catalysts were ascribed to the distinct structural and acidic properties of the supports. In particular, the good performance of the Ti(IV) doped SBA-15 supported catalysts was due to the combination of Ti(IV) structurally incorporated into the silica lattice and present as surface dispersed TiO₂ particles. The negative effect of the Ti(IV) over the HMS supported catalysts was related to the high acidity induced by the more homogeneous incorporation of Ti(IV) into the silica structure.

Keywords: Pd catalyst; CH; ₄; oxidation; TiO; ₂; -SBA-15; TiO; ₂; -HMS; SO; ₂; effect

Preferential oxidation of CO over Pt–Sn/AC catalyst: Adsorption, performance and DRIFTS studies by Burcu Selen Caglayan; İ. Ilgaz Soykal; A. Erhan Aksoylu (pp. 540-549).

Preferential CO oxidation over 1% Pt–0.25% Sn/AC-N catalyst was studied for various feed compositions including fully realistic feed. The CO conversion of the catalyst ca. 90% at 110°C for realistic feed conditions.Display Omitted► Bimetallic Pt–Sn supported AC-N with high amount of surface oxygen groups. ► CO adsorption does not lead to surface poisoning on Pt–Sn/AC-N in PROX. ► CO conversion and selectivity increases as temperature decreases within 110–135°C. ► CO₂ is weakly adsorbed on the catalyst limiting CO₂ inhibition in PROX. ► 90% CO conversion is reached with realistic feed at 110°C.Preferential CO oxidation over 1% Pt–0.25% Sn supported on nitric acid treated activated carbon (AC-N) was studied for various feed compositions including fully realistic feed. The real time performance of the catalyst and the effect of reaction parameters on its PROX activity and selectivity were investigated. Factors leading to high performance of the Pt–Sn/AC-N catalyst were scrutinized by CO and O₂ adsorption and PROX tests conducted on an in situ diffuse reflectance IR Fourier transform spectroscopy system connected to a mass spectrometer (FTIR-DRIFTS-MS). CO and CO₂ adsorption properties of Pt–Sn/AC-N and Pt/AC-N samples were also studied by a gravimetric analyzer. FTIR-DRIFTS-MS and adsorption studies confirmed enhanced CO chemisorption on Pt–Sn/AC-N catalyst compared to that on Pt/AC-N. The performance results showed that the presence of CO₂ and H₂O in the feed does not significantly affect the CO conversion performance and CO selectivity of the catalyst. In all tests, CO conversion increased with the decrease in temperature within 135–110°C range, indicating enhancement in CO selectivity as the temperature decreases. The CO conversion of the catalyst reached for the W/ F value tested was ca. 90% at 110°C for the H₂-rich feed including CO₂, water vapor and methane.

Keywords: Preferential CO oxidation; DRIFTS; PROX; Hydrogen purification; Activated carbon

Cinder supported K₂CO₃ as catalyst for biodiesel production by Hui Liu; Lingyan Su; Feifei Liu; Cui Li; Ugwuh Uchechukwu Solomon (pp. 550-558).

Display Omitted• New solid base catalyst using solid waste cinder. • Catalyst shows high activity for biodiesel production. • Optimum conditions for biodiesel production were determined. • High catalyst activity in continuous use last for 9h. • K₂O and Al–O–K are main active compounds in the catalyst.This study aims to explore cheap macroporous solid base catalyst with high transesterification efficiency. Cinder, as solid waste from coal burning industry, with natural macroporous structure and alkalinity, was served as the support for K₂CO₃ to prepare solid base catalyst for biodiesel production. In the present paper, catalysts prepared in different conditions were characterized by base strength, BET surface area, X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS), and the triglyceride (TG) conversion from the transesterification catalyzed by each catalyst was determined using high performance liquid chromatography (HPLC). The effects of various parameters such as concentration of K₂CO₃ impregnating solution, catalyst loading, molar ratio of methanol to oil and reaction time on the activity of catalysts were investigated. A maximum TG conversion of 99.5% was obtained under the optimal conditions as catalyst amount of 17.4%, methanol/oil of 12:1 and reaction time of 1h, which was catalyzed by the catalyst prepared with 0.50gmL⁻¹K₂CO₃ impregnating solution. The results indicated that K₂CO₃ was decomposed into K₂O by the catalysis of metal oxides in cinder or transformed into Al–O–K compounds through reaction with cinder. The formation of K₂O and Al–O–K compounds should be the main reason for the catalytic activity. Continuous use of the catalyst in a tubular reactor showed high TG conversion (>90%) maintained 9h. The deactivation of the catalyst after 9h use was mainly caused by potassium leaching to the glycerol phase.

Keywords: Cinder; Solid catalyst; Tung oil; Transesterification; Biodiesel

Highly efficient photocatalytic oxidation of phenol over ordered mesoporous Bi₂WO₆ by Songmei Sun; Wenzhong Wang; Jiehui Xu; Lu Wang; Zhijie Zhang (pp. 559-564).

Display Omitted• Ordered mesoporous Bi₂WO₆ is firstly realized by nanocasting method. • It is used for photocatalytic oxidation of organic contaminants. • Its photocatalytic activity is significantly better than nonporous powder. • Electrochemical studies reveal the reasons for its high photocatalytic activity.Ordered mesoporous Bi₂WO₆ (M-Bi₂WO₆) with nanocrystalline walls was fabricated for the first time by a silica-templated nanocasting method with bismuth nitrate and phosphotungstic acid as precursors. The as-prepared mesoporous Bi₂WO₆ sample exhibited a much higher photocatalytic activity than the conventional hydrothermally synthesized nanoscale Bi₂WO₆ (HR-Bi₂WO₆) on the degradation of phenol which is quite toxic but widely used and slowly degradable in the environment. Almost 97% of the phenol molecules were degraded within 60min along with the sharp decrease of total organic carbon (TOC) in 100mL of phenol solution (20mg/L) under visible-light irradiation. Compared with HR-Bi₂WO₆ sample, the M-Bi₂WO₆ sample exhibited a negative shift of conduction band edge potential and faster charge transfer property which helped to improve the photocatalytic performance.

Keywords: Phenol oxidation; Mesoporous Bi; ₂; WO; ₆; Photocatalysis; Electrochemical study

Iron redox cycling in hydroxyl radical generation during the photo-Fenton oxidative degradation: Dynamic change of hydroxyl radical concentration by Masahiro Tokumura; Risa Morito; Rurika Hatayama; Yoshinori Kawase (pp. 565-576).

.Display Omitted• TheOH radical concentration during the photo-Fenton process was measured. • The change inOH radical concentration could be described by the Fe-redox cycle. • The oxidation of iron–organic complexes accelerated the rate of Fe-redox cycle. • The Fe–organic complexes led to decrease in Fe ions available for the degradation.Effects of Fenton reagents, iron and hydrogen peroxide, on the generation of hydroxyl radicals (OH) during photo-Fenton degradation of acetaldehyde dissolved in water were examined. The dynamic change inOH radical concentration during the acetaldehyde degradation by the photo-Fenton process was measured using a coumarin fluorescence probing technique. TheOH radical concentrations increased with increasing initial Fe concentrations within the Fe dosage range examined in this study. With increasing acetaldehyde loading theOH radical concentration decreased. TheOH radical concentration changed rather complicatedly as the acetaldehyde degradation by the photo-Fenton oxidation process proceeded. The dynamic change inOH radical concentration could be divided into four phases: theOH radical concentration instantaneously and significantly increased just after the start of photo-Fenton oxidation process (Phase I), subsequently decreased (Phase II), increased again after reaching its minimum value (Phase III), and gradually decreased after theOH radical concentration reached a maximum point (Phase IV). This complicated change inOH radical concentration during photo-Fenton degradation of acetaldehyde could be rationally described by the Fe-redox cycle via the Fe–organic complex formation and its oxidation by dissolved oxygen besides the Fenton and photo-Fenton reactions. It was found that the oxidation of iron–organic complexes formed by ferric iron with acetaldehyde and its degradation products accelerated the rate of Fe-redox cycle. On the other hand, the formation of Fe–organic complexes led the decrease in Fe ions available for the Fenton and photo-Fenton reactions.

Keywords: OH radical concentration; Fe-redox cycle; Photo-Fenton degradation; Fe–organic complexes; Acetaldehyde

In situ formation of large-scale Ag/AgCl nanoparticles on layered titanate honeycomb by gas phase reaction for visible light degradation of phenol solution by Yuxin Tang; Vishnu P. Subramaniam; Teck Hua Lau; Yuekun Lai; Dangguo Gong; Pushkar D. Kanhere; Yu Hua Cheng; Zhong Chen; Zhili Dong (pp. 577-585).

Display Omitted• In situ formation of large-scale and uniformly distributed Ag/AgCl nanoparticles on titanate honeycomb (THC) surface nanostructures. • The formation of uniform and dense AgCl nanoparticles on THC is by a facile technique combining ion-exchange and vapor phase reaction. • The Ag/AgCl/THC plasmonic photocatalysts are grown on a substrate so there is no concern about the catalyst separation as in the particle system. • The degradation mechanism of phenol is discussed based on the high performance liquid chromatography and gas chromatography–mass spectrometry.Highly uniform AgCl nanoparticles (NPs) were grown in situ on a titanate honeycomb (THC) structure. The honeycomb structure is composed of vertically grown, intertwined one dimensional (1D) titanate nanowires from its side walls. This unique morphology of the THC surface structure was prepared by a modified hydrothermal approach within a short autoclave treatment time. The growth of AgCl crystals on the THC firstly makes use of a facile ion-exchange process by soaking the as-prepared THC in HNO₃ solution and AgNO₃ in sequence, during which Na⁺ ion in the interlayer of titanate is consequently replaced by H⁺ and Ag⁺ ions without changing its morphology. The obtained Ag-THC then readily reacts with HCl vapor to form the AgCl particles on THC. Finally, the visible-light-driven plasmonic photocatalyst Ag/AgCl/THC is obtained by partially reducing Ag⁺ ions from AgCl particles with the aid of Xe lamp illumination. The as-prepared photocatalyst exhibited high activity in the visible region of the solar spectrum for the degradation of phenol solution. The degradation performance and mechanism were discussed based on the high performance liquid chromatography (HPLC) and gas chromatography-mass spectrometry (GC–MS).

Keywords: In situ formation; Ag/AgCl nanoparticles; Titanate; Phenol degradation; Visible light degradation

Novel luminescent photocatalytic deNO_x activity of CaAl₂O₄:(Eu,Nd)/TiO2−_xN_y composite by Huihui Li; Shu Yin; Tsugio Sato (pp. 586-591).

Display Omitted• We firstly developed an effective full-time active luminescent photocatalyst system. • It is a new concept for the photocatalyst synthesis and application. • The composite displayed excellent photocatalytic deNO_x activity under UV-light irradiation as well as persistent activity after turning off light. • A promising strategy involves coupling of visible light responsive photocatalyst with long afterglow phosphor was established.The systematic experiments of photocatalytic degradation of NO gas were carried out by using novel composites containing TiO2−_xN_y loaded on a long afterglow phosphor, CaAl₂O₄:(Eu,Nd). The composites were prepared in a sequence of procedures, which involved reactions of TiCl₃ and hexamethylenetetramine (HMT) mixed solution at 190°C for 2h to precipitate nano-size TiO2−_xN_y particles, followed by mixing the TiO2−_xN_y with a micro-size CaAl₂O₄:(Eu,Nd) particles by a soft planetary ball milling to yield CaAl₂O₄:(Eu,Nd)/TiO2−_xN_y composites. Photocatalytic degradation of NO was monitored both under UV light irradiation and in the dark after turning off the light. The composite displayed excellent photocatalytic activity under UV-light irradiation as well as persistent activity after turning off light. A promising strategy involves coupling of visible light responsive photocatalyst with long afterglow phosphor was established. It is a new concept for the photocatalyst synthesis implying a possibility of a novel persistent active photocatalytic system.

Keywords: Luminescent photocatalyst; DeNO; _x; Composite; Persistent photocatalytic system

Antibacterial performance of a novel photocatalytic-coated cordierite foam for use in air cleaners by Yanyan Yao; Tsuyoshi Ochiai; Hitoshi Ishiguro; Ryuichi Nakano; Yoshinobu Kubota (pp. 592-599).

A TiO₂ film with highly crystalline mesoparticles was synthesized on the rough surface of a ceramic (cordierite) by a simple impregnation and calcination procedure. When treated by relatively low-intensity UV-A irradiation (0.25mWcm⁻²) for 24h, the TiO₂-coated cordierite foam reduced by over 99.9% the number of viable cells of three gram-negative strains of bacteria ( Escherichia coli, Legionella pneumophila, and Klebsiella pneumoniae), and also the gram-positive methicillin-resistant Staphylococcus aureus, all of which are extremely important airborne infectious bacteria. The bactericidal activity assessment was carried out by an original test method developed for the three-dimensional porous structures seen in various ceramic and metal foams.Display Omitted• TiO₂-coated cordierite foam with highly crystalline meso-particles. • Strong photocatalytic antimicrobial against four strains of airborne pathogens. • An original bactericidal test method for porous structures was applied. • High photocatalytic degradation on gaseous acetaldehyde to generate CO₂ and H₂O. • TiO₂/cordierite foam is a promising material for air disinfection and purification.A novel titanium dioxide-coated cordierite foam (TiO₂/cordierite foam) was developed for use in air cleaners. By a simple impregnation procedure, TiO₂ nanoparticles were immobilized firmly onto the surface of a cordierite foam substrate through high-temperature (500°C) calcination. The strong bactericidal performance of the fabricated foam was evaluated by a newly developed test method for complex three-dimensional through-pore structures. This method could trace 5–6log units of decrease in bacterial cell numbers in an air environment, thus meeting the criteria of both the JIS and ISO standard test methods. With 0.25mWcm⁻² of UV-A irradiation for 24h, the bactericidal rate of the TiO₂/cordierite foam exceeded 99.9% for five types of airborne or droplet-based infectious pathogens: Escherichia coli ( E. coli), Pseudomonas aeruginosa ( P. aeruginosa), Legionella pneumophila ( L. pneumophila), Klebsiella pneumoniae ( K. pneumoniae), and methicillin-resistant Staphylococcus aureus (MRSA). The results of repeat testing, where the same sample was used three times, revealed that the bactericidal rate for E. coli was maintained at 99.9% in the second and third use, indicating that the TiO₂/cordierite foam possesses a long-term bactericidal action. The TiO₂/cordierite foam also exhibited a high photocatalytic degradation capability on gaseous acetaldehyde, which is associated with sick building syndrome, and volatile organic compounds to generate CO₂ and H₂O. The results demonstrated that TiO₂-coated cordierite foam has great potential for use in air-cleaning filters with not only high bactericidal performance to remove pathogens in the air and in droplets, but also strong decontaminating and deodorizing functionality.

Keywords: TiO; ₂; -coated cordierite foam; Photocatalytic degradation; Airborne pathogens; Air-cleaning filters

Toluene photocatalytic oxidation at ppbv levels: Kinetic investigation and carbon balance determination by O. Debono; F. Thevenet; P. Gravejat; V. Hequet; C. Raillard; L. Lecoq; N. Locoge (pp. 600-608).

Display Omitted• Toluene batch photocatalytic abatement on the ppb range. • Simultaneous investigation: (i) toluene removal, (ii) reaction intermediate, (iii) CO & CO₂ formation at ppb levels. • Gaseous organic reaction intermediates represent only from 1 to 1.5% of the carbon mass balance during the photocatalytic process. • CO and CO₂ formation mainly occur once toluene was removed from the batch reactor: thus mineralization is mainly performed through adsorbed species oxidation. • CO₂ formation is highly improved by 50% RH.An investigation of toluene photocatalytic oxidation was conducted with initial concentrations of toluene ranging from 50 to 800ppbv under dry and wet (50% RH) atmosphere in order to characterize photocatalysis performances close to indoor air conditions. A batch reactor system was developed in order to perform kinetic studies of (i) toluene removal, (ii) organic reaction intermediate formation and removal, (iii) CO and CO₂ formation, at ppbv levels. The monitoring of CO and CO₂ produced by a photocatalytic reaction in the air with ppbv levels of pollutant is reported for the first time. It appears that toluene removal follows, even at ppbv levels, a pseudo first order kinetic slightly improved by the presence of water vapour (50% RH). The determination of reaction intermediate temporal profiles confirmed that oxidized aromatic compounds (benzaldehyde, cresols) are toluene primary reaction intermediates. The fact that no benzoic acid was evidenced in the gas phase, and that benzaldehyde maximum concentration remains below 4ppbv indicate that several consecutive oxidation steps take place in the adsorbed phase with a low desorption of reaction intermediate. The diversity of aliphatic reaction intermediates obtained after toluene ring opening is coherent with former results obtained at ppmv initial levels of toluene. Nevertheless, the removal of the lightest carbonyls (acetone, acetaldehyde and formaldehyde) is not observed within 14h of reaction. Carbon mass balance calculations performed with all the quantified gas phase reaction intermediates evidenced that those compounds represent only from 1 to 1.5%. This portion is almost constant during the whole oxidation process. The precise determination of CO and CO₂ concentrations gives a good overview of the oxidation/mineralization process. CO and CO₂ measurements evidenced that the presence of water vapour (50% RH) considerably improves the formation of CO₂ corresponding to a better mineralization of organic matter and an improved conversion of CO into CO₂. Temporal profiles of CO₂ concentration reveal that CO₂ formation rate is highly dependent on the nature of the compounds to be treated. Between 10 and 12h of reaction, corresponding to 95% conversion of toluene, CO and CO₂ represent only from 25 to 35% of the carbon mass balance. If the reaction is performed on longer times, the mineralization percentage constantly increases until 23h of irradiation, mainly corresponding to oxidation of compounds adsorbed on photocatalyst surface. After 22h of irradiation, the mineralization (CO+CO₂) finally exceeds 70% of the carbon mass balance.

Keywords: Photocatalysis; Indoor air; Toluene; Carbon mass balance

Preparation and characterization of Pt/TiO₂ nanotubes catalyst for methanol electro-oxidation by Bochra Abida; Lotfi Chirchi; Stève Baranton; Teko Wilhelmin Napporn; Hafedh Kochkar; Jean-Michel Léger; Abdelhamid Ghorbel (pp. 609-615).

TEM images of Pt/TiO₂ nanotubes catalyst which clearly demonstrate a typical structure of nanotubes and uniform platinum particles well dispersed on titanium dioxide nanotubes.Display Omitted• Studies of adsorption isotherms showed the presence of TiO₂ nanotubes higher specific surface area which is preferable for the electro-catalyst. • The TEM and the XRD proved that TiO₂ nanotubes exhibit uniform distribution in length and diameter. • The TGA–DTA results illustrated that the amount of H₂O contained in the TiO₂ nanotubes was higher than that of TiO₂. • Pt/TiO₂ nanotubes/C catalyst exhibits the best activity for methanol oxidation and was favorable for improving the tolerance to poisoning species in comparison with Pt/TiO₂ (Degussa P25) and Pt/C (XC72) electrocatalysts.Titanium dioxide nanotubes were prepared via a hydrothermal treatment of TiO₂ powder (Degussa P25). Obtained samples were analyzed by various techniques, such as transmission electron microscopy (TEM) and X-ray diffraction (XRD), which revealed that the crystal structure of the obtained materials was similar to that of H₂Ti₂O₅·H₂O nanotubes, and were about 50nm in length and 20nm in diameter. Nitrogen adsorption–desorption isotherms indicated that synthesized solids are mesoporous materials with a multi-walled nanotubular structure and high specific surface area. The methanol oxidation reaction was investigated on platinum nanoparticles supported TiO₂ nanotubes (XC72). The electrocatalytic activity of the catalyst was measured by cyclic voltammetry. CO stripping voltammetry in acidic solutions was investigated to study the reaction of the catalysts towards poisoning by carbonyl compounds. The results demonstrated that Pt/TiO₂ nanotubes catalyst exhibits the best activity for methanol oxidation and were favorable for improving the tolerance to poisoning species.

Keywords: Electrocatalysts; Hydrothermal process; Platinum nanoparticles; Titanium dioxide nanotubes; Methanol electro-oxidation

Plasma-assisted methane reduction of a NiO catalyst—Low temperature activation of methane and formation of carbon nanofibres by Helen J. Gallon; Xin Tu; Martyn V. Twigg; J. Christopher Whitehead (pp. 616-620).

Carbon nanofibre produced on a Ni catalyst by a low temperature methane plasma.Display Omitted• A low temperature methane plasma is used to reduce a NiO catalyst for the first time. • The reduced catalyst is used for the low temperature reforming of methane into hydrogen. • Carbon nanofibres are produced on the Ni catalyst by a low temperature methane plasma.The low temperature reduction of a NiO catalyst by CH₄ was performed in a coaxial double dielectric barrier discharge (DBD) reactor for the first time. The reduction involves active surface carbon which is produced via plasma decomposition of CH₄. On the reduced Ni catalyst, activation of CH₄ and its fragments to form H₂ and carbon nanofibres occurred at 330°C. CH₄ conversions of 37% were achieved in the plasma-catalytic reaction at atmospheric pressure, with 99% selectivity towards H₂ and solid carbon. These results demonstrate a synergistic effect where both the plasma and catalyst are vital for the production of H₂ and carbon nanofibres. In the absence of the catalyst stable plasma could not be ignited with a pure CH₄ flow and thermal studies showed that in the absence of the plasma CH₄ conversion was minimal.

Keywords: Carbon nanomaterials; Dielectric barrier discharge; Methane activation; NiO reduction; Plasma-catalysis

Fe-doped ceria solids synthesized by the microemulsion method for CO oxidation reactions by O.H. Laguna; M.A. Centeno; M. Boutonnet; J.A. Odriozola (pp. 621-629).

The synthesis of Fe-doped ceria oxides was carried out by microemulsions method, employing different Fe atomic percentages (at.%). The 10at.% Fe allows obtaining Ce–Fe solid solution with the higher oxygen vacancies content. This system presents the higher CO conversion during the TOX and PROX reactions.Display Omitted• A series of Ce–Fe mixed oxides were synthesized by the microemulsions method. • Solid solution formation was established for all the Fe-doped systems. • The oxygen exchange is improved for all the Fe-doped systems. • The 10at.% Fe allows obtaining the maximum oxygen vacancies concentration.A series of Ce–Fe mixed oxides as well as the pure oxides were synthesized by the microemulsions method. The solid solution formation was established for all the Fe-doped systems and only a hardly noticeable segregation of α-Fe₂O₃ was appreciated for the solid with the maximum iron content (50at.% Fe). The oxygen exchange is improved for all the Fe-doped systems; however the 10at.% Fe appears as the optimal iron content for achieving the maximum oxygen vacancies concentration and the higher reducibility efficiency. The CO oxidation (TOX, PROX) is especially achieved for the solids with the lower iron contents but with a superior oxygen vacancies proportion. These Ce–Fe systems prepared from microemulsions are very attractive to be considered as supports for depositing active phases capable of enhancing oxygen exchange ability of the whole system, allowing higher CO oxidation abilities.

Keywords: Water-in-oil microemulsion; Fe-doped ceria; CO oxidation; Oxygen vacancies

Elucidating the photocatalytic degradation pathway of acetaldehyde: An FTIR in situ study under atmospheric conditions by Birger Hauchecorne; Dieter Terrens; Sammy Verbruggen; Johan A. Martens; Herman Van Langenhove; Kristof Demeestere; Silvia Lenaerts (pp. 630-638).

Display Omitted• FTIR in situ reactor used for real time study of photocatalytic acetaldehyde removal. • Formation of crotonaldehyde and 3-hydroxybutanal upon adsorption of acetaldehyde on TiO₂. • Acetic acid, formic acid, formaldehyde and their respective conjugated bases are found as reaction intermediates.In this paper, new insights of the photocatalytic oxidation pathway of acetaldehyde are obtained by means of an in-house constructed FTIR in situ reactor. It is shown that there are generally three different intermediates present: acetic acid, formic acid and formaldehyde. By means of FTIR in situ spectroscopy, this study revealed that these intermediates are bound on the TiO₂ surface in different ways, resulting in the presence of more intermediate species, such as molecularly adsorbed acetic acid, bidentate acetate, molecularly adsorbed formic acid, monodentate formate, bidentate formate, formaldehyde and dioxymethylene. Furthermore, spectroscopic evidence is obtained concerning the formation of 3-hydroxybutanal and crotonaldehyde upon adsorption of acetaldehyde on TiO₂ prior to UV illumination. The presented results thus give new insights in the photocatalytic oxidation pathway of acetaldehyde.

Keywords: Photocatalysis; Acetaldehyde; In situ FTIR study; Reaction pathway

The ethanol steam reforming over Cu-Ni/SiO₂ catalysts: Effect of Cu/Ni ratio by Li-Chung Chen; Shawn D. Lin (pp. 639-649).

Display Omitted• The prepared 5% CuNi/SiO₂ catalysts showed the highest performance for ESR when Cu/Ni=1. • The CuNi/SiO₂ catalyst with Cu/Ni=1 had low coking and particle sintering tendencies during ESR. • The relative selectivity of each reaction pathway of ESR was quantitatively analyzed. • The CuNi/SiO₂ catalyst with Cu/Ni=1 had the smallest metal particles and Cu and Ni formed alloy.The operating conditions of SRE (steam reforming of ethanol) reaction were evaluated by thermodynamics, in considering of the application requirements in hydrogen concentration and energy consumption. Under the select operating conditions, 5% CuNi/SiO₂ catalysts with different Cu/Ni ratios prepared through incipient-wetness co-impregnation were tested for SRE. The catalysts were reduced with NaBH₄ at room temperature, and again reduced by H₂ at 623K prior to temperature-programmed SRE testing to remove surface oxygen. The SRE reaction products indicate a reaction scheme involving ethanol dehydrogenation to acetaldehyde, wherein acetaldehyde steam reforming and acetaldehyde decomposition compete, and with subsequent CO conversion to CO₂ via water gas shift reaction. The catalysts with Cu/Ni≥1 showed higher ethanol conversion, higher acetaldehyde conversion, higher selectivity of acetaldehyde steam reforming, and lower coking at temperatures below 673K than the Ni-rich catalysts. Analyses by XRD, XPS, and EXAFS indicate that the Cu-rich catalysts had formed an alloy structure with Ni-enriched surface. The catalyst with Cu/Ni=1 showed the highest performance in ethanol conversion, acetaldehyde conversion, the selectivity of acetaldehyde steam reforming, and the stability against particle sintering.

Keywords: Ethanol; Steam reforming; Cu-Ni; Impregnation; Reaction pathway

Preparation of nano-sized Cu from a rod-like CuFe₂O₄: Suitable for high performance catalytic applications by Sheng-Chiang Yang; Wei-Nien Su; Shawn D. Lin; John Rick; Ju-Hsiang Cheng; Jyong-Yue Liu; Chun-Jen Pan; Din-Goa Liu; Jyh-Fu Lee; Ting-Shan Chan; Hwo-Shuenn Sheu; Bing-Joe Hwang (pp. 650-656).

Display Omitted• A mesoporous template was used to produce nano-sized copper, by the thermal hydrogen reduction of spinel CuFe₂O₄nano-crystals. • The resulting copper had an estimated size of 3.6nm and a surface area of 115m²/g and the required reduction temperature is less than 210°C. • Steam reforming of methanol was used as an example to show the capability of the catalyst, whereby a 100% conversionwas achieved at around 240°C. • This proposed synthesis method that produces finely dispersed nanoparticles can be extended to other mixed metal oxide systems and various applications.A space-confined synthesis method, using a mesoporous template that produces nano-sized copper (∼3.6nm crystal size) by the thermal hydrogen reduction (THR) of spinel CuFe₂O₄ nano-crystals, that have a high surface area ∼126m²/g, (c.f. commonly cited literature values <10m²/g) and a rod-like morphology, is described. In situ XRD and temperature program reduction (TPR) results showed that the generation of the copper nanoparticles occurred at 210°C, which is lower than other reported literature values—due to the fine crystal size of the spinel CuFe₂O₄. The generated copper nanoparticles were also characterized by XANES, and FT-EXAFS. We have used the steam reforming of methanol (SRM) as a model reaction to demonstrate the capability of the materials formed in which a 100% conversion of methanol by steam reforming was achieved at approximately 240°C. The proposed synthesis method combines metallurgy and THR while at the same time effectively resolving issues related to the large crystal sizes, higher calcinations temperature (above 750°C) and low surface areas (below 10m²/g), that commonly occur in conventional solid state methods. The mixed metal oxide synthesis method, using a mesoporous template, can also be applied to other heterogeneous metal oxide systems.

Keywords: Copper; Copper iron oxide; Mesopore; Space confined; Methanol steam reforming; Rod-like; Thermal hydrogen reduction; Mixed metal oxide

Investigations of photocatalytic activities of photosensitive semiconductors dispersed into epoxy matrix by P. Calza; L. Rigo; M. Sangermano (pp. 657-663).

.Display Omitted• Hybrid catalyst coating have been synthesised. • TiO₂ nanoparticles are encapsulated into an epoxy matrix by UV-cured polymerization. • Methylene blue was complete degraded within 90min.New hybrid catalyst coating has been synthesised encapsulating TiO₂ nanoparticles into an epoxy matrix by means of UV-induced polymerization. It was shown that the presence of the titania nanoparticles did not significantly influence the curing process. Morphological analysis of the achieved UV cured coatings containing titania showed an homogeneous distribution of the inorganic particles, with an average size between 130 and 160nm. It is mandatory that the coating will not be itself degraded during UV irradiation. FT-IR measures performed on aged coatings subjected to UV irradiation for 41 days showed that the photodegradation of either the pristine epoxy coating or coating containing the photocatalyst was negligible.The photocatalytic efficiency of these new catalysts was evaluated by studying the degradation of some organic compounds under UV light. Methylene blue was employed as model molecule to investigate the photoactivity toward organic molecule directly adsorbed on the coating surface. Under irradiation, complete dye degradation was achieved within 90min. Phenol and 3,5-dichlorophenol were used as target molecules for studying photoactivity toward organic compounds dissolved in aqueous solution. Also in these cases, complete degradation of the organic compounds was achieved.

Keywords: TiO; ₂; UV-curing; Phenol; Photocatalysis

Spatially resolving LNT desulfation: re-adsorption induced by oxygen storage materials by Jin-Yong Luo; Meshari AL-Harbi; Marcus Pang; William S. Epling (pp. 664-671).

Display Omitted• The desulfation process along a LNT is spatially resolved. • Sulfur desorbed from a commercial catalyst front re-adsorbed at the back. • No readsorption was observed with a model sample. • The reason for re-adsorption was the presence of OSC materials.Spatially resolved gas concentration measurements were obtained along a commercial LNT sample, containing both NO_x storage and oxygen storage components, during exposure to different levels of sulfur and under mild desulfation conditions. For a partially sulfated sample, with sulfur mainly deposited toward the catalyst inlet, during the desulfation some of the sulfur species released from the front were re-adsorbed along the back part of the catalyst, leading to redistribution of the sulfur species. For the fully sulfated sample, no re-adsorption occurred. Interestingly, for a partially sulfated model sample, Pt/BaO/Al₂O₃, no re-adsorption was observed. Based on the data obtained from the model and commercial samples, the ceria-based oxygen storage (OS) material plays a crucial role in this sulfur re-adsorption. The OS material's main function in this process is to provide oxygen for the oxidation of the released sulfur species from the front, so that they re-adsorb at the catalyst back. Besides this sulfur redistribution, these OS materials also influence the desulfation products. More H₂S, relative to SO₂, is released from the OS-containing sample since S ultimately spent more time within the catalyst via re-adsorption and extra reductant consumption by the OS materials. In addition, NO_x re-adsorption during regeneration was also observed, leading to a decreased NO_x release at the transient from the lean to rich phases. However, the extent of NO_x re-adsorption was significantly less relative to sulfur re-adsorption under the test conditions used.

Keywords: Lean NO; _x; trap; Desulfation; Regeneration; Spatial resolution; Sulfur poisoning

Preparation and characterization of SBA-15 supported Pd catalyst for CO oxidation by Houpeng Wang; Chang-jun Liu (pp. 672-680).

Display Omitted• Highly dispersed nanoparticles were synthesized within the uniform channels via a glow discharge plasma treatment. • The activity of the Pd/SBA-15 catalyst on CO oxidation was firstly evaluated. • The highly dispersed nanoparticles remain stable after the reaction. • The Pd/SBA-15 catalysts show a good activity on CO oxidation. • The catalyst preparation method has a significant influence on the catalyst activity.SBA-15 supported noble metal catalysts for CO oxidation have been extensively investigated. However, no reported work on the SBA-15 supported palladium catalyst for CO oxidation can be found in the literature. In this work, highly dispersed palladium nanoparticles were synthesized within the uniform channels of SBA-15 via a glow discharge plasma reduction treatment. The obtained Pd/SBA-15 catalyst shows a good activity for CO oxidation. The activity can be further improved by the hydrogen reduction thermally. The low-angle X-ray diffraction (XRD) patterns and transmission electron microscope (TEM) indicate that the ordered mesoporous structure was well maintained during the catalyst preparation and reaction processes. The wide-angle XRD patterns and TEM images show that the spherical palladium nanoparticles are highly dispersed within the SBA-15 channels and remain stable after the reaction. The diffuse reflectance infrared Fourier transformation (DRIFT) spectroscopy of adsorbed CO confirms that the structure change caused by different preparation conditions has a significant influence on the activity of the catalyst.

Keywords: Mesoporous material; SBA-15; Palladium; CO oxidation; Plasma

Photocatalytic reforming of C3-polyols for H₂ production by Xianliang Fu; Xuxu Wang; Dennis Y.C. Leung; Quan Gu; Shifu Chen; Haibao Huang (pp. 681-688).

Display Omitted► The role of C3-polyols’ OH groups in their photocatalytic reforming (PR) reaction has been investigated. ► The OH groups served as anchors for the chemical adsorption of polyols, and as effective holes scavengers to trigger the reaction. ► OH directly connected segment of polyol can be effectively converted to H₂ and CO₂ via the PR process.TiO₂ photocatalyst was prepared by sol–gel method, and then loaded with 1.0wt.% Pt by impregnation-chemical reduction method (denoted as PT). Photocatalytic reforming (PR) of C3-polyols (glycerol, propyleneglycol, and isopropanol) which have similar carbohydrate structure but possess different number of OH groups for H₂ production over PT was performed to study the role of their OH groups in the reforming reaction. The results indicated that the H₂ evolution rate and the mineralization efficiency of polyols (oxidized to CO₂) are highly correlated with the number of OH groups they contain. The more OH group it has, the higher H₂ evolution rate can be obtained, as well as the generation of CO₂. The roles of the OH group were discussed in terms of providing an anchor for the chemical adsorption of polyols to the PT and serving as an effective holes scavenger to trigger the reforming reaction. For a polyol molecule, only OH directly connected segment can be effectively converted to H₂ and CO₂ via the PR process.

Keywords: Photocatalytic reforming; OH group; Polyols; Hydrogen production; Pt/TiO; ₂

Photocatalytic reforming of C3-polyols for H₂ production by Quan Gu; Xianliang Fu; Xuxu Wang; Shifu Chen; Dennis Y.C. Leung; Xiuqiang Xie (pp. 689-696).

Display Omitted► Both the adsorption complexes and the reforming intermediates formed on the PT and the gas-phase were determined and identified by FTIR spectra. ► The adsorption process and the photocatalytic reforming mechanism of 2-propanol was proposed. ► The OH groups contained in 2-propanol are serve as anchors for their adsorption and involve the formation of charge transport ways, which facilitates their oxidation by photogenerated holes.The adsorption behavior and the photocatalytic reforming (PR) process of 2-propanol over Pt (1wt.%)/TiO₂ (PT) photocatalyst have been investigated by Fourier transform infrared (FTIR) spectroscopy. Both the adsorption complexes and the reforming intermediates formed on the PT and the gas-phase were determined and identified by FTIR spectra. The results indicated that the first layer surface of the PT mainly consisted of chemisorbed 2-propanol (Ti–OCH(CH₃)₂) through the condensation of 2-propanol with surface Ti–OH or dissociative adsorption with undercoordinated Ti atoms, while the second layer consisted of physisorbed 2-propanol by interaction with the chemisorbed one or the formed H₂O via hydrogen-bond. Under UV irradiation, a rapidly deprotonation of 2-propoxide occurred by the attack of holes (h⁺) and resulted in the formation of acetone, which was then slowly oxidized to acetate and formate species by the hydroxyl radicals (OH). The carboxylates finally decarboxylate over the PT to evolve CO₂ and CH₄ via the photo-Kolbe reaction. According to the results, a reforming mechanism was proposed. The role of the OH groups contained in 2-propanol and its intermediates were found to serve as anchors for their adsorption and to involve the formation of h⁺ transport ways.

Keywords: Photocatalytic reforming; Adsorption; FTIR study; 2-propanol; Pt/TiO; ₂

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Applied Catalysis B, Environmental (v.106, #3-4)

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Applied Catalysis B, Environmental (v.106, #3-4)