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Applied Catalysis B, Environmental (v.89, #1-2)

Contents (pp. co4).

Editorial Board (pp. i).

Contents Continued (pp. i).

IFC Editorial Board (pp. co2).

Examining the surface of a synergistic Pt-Rh/γ-Al₂O₃ catalyst using NO as a probe molecule by Paul S. Dimick; John L. Kross; Erin G. Roberts; Richard G. Herman; Harvey G. Stenger; Charles E. Lyman (pp. 1-11).

The interaction of NO and NO+H₂ with reduced γ-Al₂O₃, Pt/γ-Al₂O₃, Rh/γ-Al₂O₃, Pt(90%)-Rh/(10%)/γ-Al₂O₃ (90/10), and Pt(95%)-Rh(5%)/γ-Al₂O₃ (95/5) was monitored with FTIR spectroscopy to better understand the surface of a synergistic Pt-Rh catalyst (95/5). The surface of the alloy nanoparticles on the synergistic 95/5 catalyst contained both Pt and Rh due to the presence of FTIR peaks representing linear NO on Pt and NO on Rh. The presence of Pt and Rh on the surface of 90/10 was confirmed through the observation of the linear NO-on-Pt peak and the Rh nitrosyl peak, respectively. The presence of the Rh nitrosyl peak at 150°C and 200°C on 90/10 indicates the presence of partially oxidized Rh on the surface of the supported Pt-Rh alloy particles at these temperatures. The following relative order of NO reduction activity was observed for the prepared catalysts: 95/5>Pt/γ-Al₂O₃≈90/10≫Rh/γ-Al₂O₃. The maximum synergistic performance of 95/5 was a five-fold increase over the activity of Pt/γ-Al₂O₃, and this was only observed after conditioning the catalyst by equilibrating to reaction conditions for 10h at 250°C. A discussion of the reaction mechanism and the observed surface species reveals that the differing performance of 95/5 and 90/10 is related to the amount of Rh on the surface of the supported alloy nanoparticles.

Keywords: Nitric oxide probe molecule; Platinum–rhodium; Bimetallic nanoparticle; Surface segregation; Synergistic catalyst

Oxidation of α-methylphenylglycine under Fenton and electro-Fenton conditions in the dark and in the presence of solar light by Anna Serra; Xavier Domènech; Conchita Arias; Enric Brillas; José Peral (pp. 12-21).

The oxidation of α-methylphenylglycine (α-MPG, S-2-amino-2-phenylpropionic acid) amino acid in aqueous solution by means of Fenton, solar photo-Fenton (SPF), electro-Fenton (EF), and solar photoelectro-Fenton (SPEF) reactions is studied. Several H₂O₂ initial concentrations were used in the chemical systems, while different currents were tested in the electrochemical ones where H₂O₂ was electrogenerated from O₂ reduction at a gas diffusion cathode. α-MPG concentration and total organic carbon (TOC) removals along time were ascertained, and the electrochemical reactions turned out to be faster than the chemical ones. The presence of light was beneficial for both configurations. Reaction intermediates were detected using high-performance liquid chromatography, gas chromatography–mass spectrometry, and liquid chromatography–mass spectrometry analysis. A special attention was paid to the nature and time course of the carboxylic acids generated, being oxalic and oxamic acids those detected at higher concentrations. Apart from oxamic acid, NH₄⁺ and NO₃⁻ ions were the nitrogen containing species detected and the nitrogen mass balance was not closed, probably due to the generation of NO_x or other volatile nitrogen species. Taking into account all the collected information about the reaction intermediates, a comprehensive reaction mechanism for α-MPG oxidation to aromatic intermediates is proposed.

Keywords: α-Methylphenylglycine; Fenton; Electro-Fenton; Solar light; Carboxylic acids; Aromatic intermediates; Degradation pathway

Catalytic combustion of butane on Ru/γ-Al₂O₃ catalysts by Janina Okal; Mirosław Zawadzki (pp. 22-32).

Ru/γ-Al₂O₃ catalysts were prepared by incipient wetness method from RuCl₃ precursor and their performance in oxidation of iso- and n-butane was investigated. The catalytic activity was examined on the calcined–reduced and on the directly reduced catalysts, with and after removing Cl ions, as well as after the oxidation at 250°C. All catalysts have been characterized by various methods such as BET, XRD, TEM, XPS, H₂ chemisorption and O₂ uptake in order to correlate their performance with their physiochemical properties. It was found that pre-treatment procedure has a significant influence on activity of the Ru/γ-Al₂O₃ catalysts. The considerable contamination of Ru particles by chlorine ions results in lowering activity of the Ru/γ-Al₂O₃ catalysts. It was established that reduced nearly Cl-free Ru/γ-Al₂O₃ catalysts exhibited higher activity than catalysts oxidized at 250°C. It was shown by XRD, TEM and O₂ uptake data that at this temperature, very small Ru particles were transformed completely into RuO₂, while the large Ru particles were partly covered by a thin RuO₂ film (1.6nm). Catalytic and characterization results revealed that the most active sites in the butane oxidation reaction, consist probably of a few layers of thick surface oxide on the large Ru particles and small Ru_xO_y clusters without well-defined stoichiometry. Such surface species were formed at 100–200°C in all catalysts and in the most active reduced Cl-free 4.6% Ru catalyst which reached 100% butane conversion below 200°C. The catalytic performance of Ru declined as the catalysts were oxidized at higher temperature. The activity loss was attributed to the formation of crystalline RuO₂ phase and to some sintering of the active phase. In the used catalysts, small Ru particles were oxidized to RuO₂ while the large Ru particles were covered with RuO₂ layer, with a thickness of 2–3nm, as shown by TEM and XRD.

Keywords: Catalytic combustion; Butane; Ru/γ-Al; ₂; O; ₃; catalysts; Chlorine; Pre-treatment effect

The effect of sulphation on the catalytic activity of CoO_x/ZrO₂ for NO reduction with NH₃ in the presence of O₂ by Daniela Pietrogiacomi; Alessandro Magliano; Paolo Ciambelli; Diana Sannino; Maria Cristina Campa; Valerio Indovina (pp. 33-40).

Selective catalytic reduction (SCR) of NO with NH₃ in the presence of O₂, and NH₃ oxidation with O₂ (NH₃+O₂) were studied on CoO_x/ZrO₂ and sulphated-CoO_x/ZrO₂ catalysts. Monoclinic CoO_x/ZrO₂ (Co/Z_m) containing 2.0 or 4.6Co-atomsnm⁻² were prepared by dry impregnation of monoclinic ZrO₂ (Z_m) with Co(CH₃COO)₂ aqueous solutions. Three sulphated catalysts, all having roughly the same surface density of cobalt (2Co-atomsnm⁻²) were prepared by (i) exposure of Co/Z_m to a gaseous stream SO₂+O₂ (Co/Z_mS_g), (ii) impregnation of Z_m with CoSO₄ aqueous solution (CoS/Z_m), and (iii) impregnation of Zr(OH)₄ with CoSO₄ aqueous solution (CoS/Z_t, tetragonal). Calcined samples were characterized by means of XRD, UV–vis DRS and FT-IR (using CO and NO as probe molecules).In Co/Z_m, isolated Co²⁺ anchored to the ZrO₂ surface and small Co₃O₄ particles coexisted. In Co/Z_m, upon exposure to CO at 298K, isolated Co²⁺ and cobalt ions on the surface of Co₃O₄ easily underwent reduction, yielding Co n⁺-carbonyls ( n<2). Conversely, in sulphated samples, nearly all cobalt was present as isolated Co²⁺, which was far less reducible with CO at 298K than isolated Co²⁺ in Co/Z_m. Specifically, the reducibility of isolated Co²⁺decreased in the order Co/Z_m>CoS/Z_t>CoS/Z_m≅Co/Z_mS_g. On all sulphated samples, surface covalent sulphates formed. The structure of surface covalent sulphates on CoS/Z_t differed from those on CoS/Z_m and Co/Z_mS_g. On Co/Z_mS_g, covalent and ionic sulphates coexisted.In the temperature range 425–600K, Co/Z_m samples were poorly active for NO reduction and highly active for NH₃ oxidation. In this temperature range, sulphated samples were inactive for both reactions. They became highly active for NO reduction above 600K, and for NH₃ oxidation above 675K. We conclude that the catalytic activity and selectivity of CoO_x/ZrO₂ depend crucially on (i) the presence of isolated Co²⁺ endowed with the proper redox behaviour and (ii) the absence of Co₃O₄.

Keywords: Selective catalytic reduction; NO reduction; Sulphated-ZrO; ₂; Supported cobalt oxide

Structure and NO_x storage behaviour of flame-made BaCO₃ and Pt/BaCO₃ nanoparticles by M.O. Symalla; A. Drochner; H. Vogel; R. Büchel; S.E. Pratsinis; A. Baiker (pp. 41-48).

BaCO₃ and Pt/BaCO₃ nanoparticles with high specific surface area (SSA) were prepared by flame spray pyrolysis (FSP). Their structure and behaviour during NO_x storage were investigated with special focus on the mechanistic and kinetic details. NO exposure of BaCO₃ (BET: 45m²g⁻¹) at various temperatures resulted in simple NO adducts. Low NO storage rate and NO_x storage capacity (NSC) were observed up to 400°C. In the presence as well as the absence of oxygen, NO was stored on BaCO₃ showing the same IR-adsorption bands at 100–300°C. Higher NSC and storage rates were observed for NO₂ adsorption. DRIFT spectra showed that NO₂ adsorption is accompanied by the formation of small amounts of NO which could be stored and subsequently oxidised again to NO₂ adducts.Pt/BaCO₃ prepared under identical conditions resulted in higher SSA (110m²g⁻¹) and showed increased NSC especially at higher temperatures. Enhanced DRIFT adsorption bands indicated the same NO adducts as obtained for the Pt-free BaCO₃ during NO treatment. In the presence of oxygen and above the light-off temperature for NO oxidation, the consecutive reaction of stored nitrite to nitrate could be observed by in situ DRIFTS. NO₂ adsorption led again to the highest NSC and storage rate. An optimal operation temperature window around 300°C was found where the NO₂ storage rate was high and the catalysed competing NO₂ conversion to NO was low enough to afford maximal NSC. Structural investigations indicate that only prolonged NO_x treatment leads to bulk barium nitrate: solid state conversion occurs after few hours. This supports the contention that the main contribution to NO_x storage during technical application in NSR catalysis occurs in the surface and subsurface regions of BaCO₃.

Keywords: Lean NO; _x; trap; NO; _x; storage; Flame spray pyrolysis; Nanoparticles; BaCO; ₃; Pt/BaCO; ₃; Platinum; BaO; In situ; DRIFTS; NO; ₂; NO breakthrough curve; Barium nitrate; Barium nitrite

Electrochemical investigation of a propane-fed solid oxide fuel cell based on a composite Ni–perovskite anode catalyst by Massimiliano Lo Faro; Daniela La Rosa; Isabella Nicotera; Vincenzo Antonucci; Antonino Salvatore Aricò (pp. 49-57).

A composite Ni–perovskite anode was investigated for operation in dry propane-fed intermediate temperature solid oxide fuel cells (IT-SOFC). A La_0.6Sr_0.4Fe_0.8Co_0.2O₃ (LSFCO) perovskite, characterized by mixed electronic–ionic conductivity, was used to support a highly dispersed Ni-phase. However, the catalyst structure was modified during SOFC operation. X-ray diffraction analysis of the electrocatalyst showed that, after operation, Ni was mainly present as La₂NiO₄; whereas, the LSFCO structure was partially modified into a lanthanum-depleted SrFe1−_xCo_xO3−_y (SFCO) perovskite structure. These results were corroborated by X-ray photoelectron spectroscopy (XPS). Transmission electron microscopy (TEM) analysis showed the presence of a suitable dispersion of a nanosized Ni-phase and a strong interaction of Ni-enriched particles with the perovskite substrate. High reaction rates for the propane reaction were achieved with this electrocatalyst while minimizing carbon deposition. Power densities of about 300mWcm⁻² for dry propane oxidation were obtained at 800°C in the presence of a thick gadolinia-doped ceria electrolyte. Fuel cell time-tests indicated promising electrochemical stability.

Keywords: Propane; Direct oxidation; La; ₂; NiO; ₄; Gadolinia-doped ceria; IT-SOFC

Kinetic and process study for ethanol reforming using a Rh/Pt washcoated monolith catalyst by Amanda Simson; Earl Waterman; Robert Farrauto; Marco Castaldi (pp. 58-64).

The reforming of pure ethanol was studied over a bi-metallic precious metal (Rh/Pt) catalyst deposited on a ceramic monolith in order to analyze reforming process conditions. High ethanol conversion tests performed at low space velocities (<20,000h⁻¹) confirmed that the catalyst could achieve 100% ethanol conversion to equilibrium concentrations of H₂, CO, CO₂ and CH₄. Low conversion tests at high space velocities (≥50,000h⁻¹) were conducted to produce an overall rate expression with an activation energy of 85kJmole⁻¹. The reaction was found to have a 1.2 reaction order for ethanol and zero order for water for stoichiometric ethanol and water ratios. In addition, the impact of non-catalytic reactions was studied. The results showed that the catalyst was capable of reforming ethanol as well as the by-products from non-catalytic reactions at 500–700°C.This work is part 1 of a series to develop a process for steam reforming E85 (85% ethanol+15% gasoline) to generate hydrogen for a fuel cell.

Keywords: Ethanol steam reforming; Hydrogen production; Rh/Pt catalysts; Monoliths; Non-catalytic ethanol decomposition

Sintering and redispersion of platinum catalysts supported on tin oxide by Naoto Kamiuchi; Keiichi Taguchi; Toshiaki Matsui; Ryuji Kikuchi; Koichi Eguchi (pp. 65-72).

CO oxidation activities of platinum/tin oxide catalysts prepared by impregnation have been investigated in relation with their nano-structural changes in various reduction–oxidation treatments. Variously treated Pt/SnO₂ catalysts were characterized by XRD, XPS, and TEM. In 1wt.% Pt/SnO₂ catalyst calcined at 400°C, crystallized fine particles of Pt were highly dispersed on SnO₂ due to strong chemical interaction between two components. After the heat-treatment in a reducing atmosphere, the sintered Pt particles with grown size were frequently observed. Furthermore, unique texture of particles with core–shell structure was produced in the catalyst exposed in air after the reduction treatment at 400°C. These large particles with the peculiar shape were re-dispersed by the reoxidation treatment at 400°C to fine particle with similar size to the as-calcined catalysts. The reversibility of the microstructural changes between growth and redispersion of deposited particles was confirmed after the several reduction–oxidation cycles. It was revealed that the structural changes on the interface of Pt/SnO₂ catalysts were closely related to the catalytic activity for CO oxidation.

Keywords: CO oxidation; Chemical interaction; Platinum; Tin oxide; Catalyst; Sintering; Dispersion; TEM

Microkinetic modeling of steady-state NO/H₂/O₂ on Pt/BaO/Al₂O₃ NOx storage and reduction monolith catalysts by Jin Xu; Michael P. Harold; Vemuri Balakotaiah (pp. 73-86).

A steady-state microkinetic model for NO reduction by H₂ and NH₃ in O₂ on alumina supported Pt/BaO monolith catalysts is developed based on the measurements from a parallel experimental study (R. Clayton, M.P. Harold, V. Balakotaiah, Selective catalytic reduction of NO by H₂ in O₂ on Pt/BaO/Al₂O₃, Appl. Catal. B: Environ. 81 (3–4) (2008) 161–18). The microkinetic model describes pertinent Pt-catalyzed regeneration chemistry during NOx storage and reduction with H₂. Kinetic parameters not available from the literatures are estimated to capture the experimental trends and to meet thermodynamic constraints. The kinetic model is incorporated into a short monolith reactor model to simulate the steady-state NH₃/O₂, NH₃/NO and NO/NH₃/H₂ reaction systems. The predicted conversion and product distribution are in excellent qualitative and good quantitative agreement with the experimental data. Among other features, the model predicts for the three reaction systems the non-linear light-off, and the product selectivity dependencies on temperature and feed composition. The model predicted trends in the species surface coverages with operating conditions help to elucidate the selectivity trends. A sensitivity analysis of the rate constants identified the critical steps in the reaction network. The effects of external mass transfer on the conversions and product distributions are assessed and discussed.

Keywords: NOx; Hydrogen; Platinum; Barium; Selective catalytic reduction; NOx storage and reduction; Lean NOx trap

Preparation, characterization, and catalytic properties of NdSrCu1−_xCo_xO4−_δ and Sm_1.8Ce_0.2Cu1−_xCo_xO4+_δ ( x=0, 0.2 and 0.4) for methane combustion by Jiguang Deng; Lei Zhang; Hongxing Dai; Hong He; Chak Tong Au (pp. 87-96).

Single-phase perovskite-like oxides NdSrCu1−_xCo_xO4−_δ and Sm_1.8Ce_0.2Cu1−_xCo_xO4+_δ ( x=0, 0.2, and 0.4) were prepared using the citric acid complexing method coupled with ultrasonic treatment. We characterized the materials by a number of analytical techniques. It was found that the NdSrCu1−_xCo_xO4−_δ and Sm_1.8Ce_0.2Cu1−_xCo_xO4+_δ catalysts possess T and T′ crystal structures, respectively. There are Cu³⁺/Cu²⁺ ions and oxygen vacancies in the former and Cu²⁺/Cu⁺ ions and extra (over-stoichiometric) oxygen in the latter. We examined the catalytic activity of the materials for methane combustion. Methane conversion increased with a rise in the amount of nonstoichiometric oxygen over the two series of catalysts. It is concluded that oxygen nonstoichiometry and Cu³⁺/Cu²⁺ or Cu²⁺/Cu⁺ redox couples facilitate the oxidation of methane over the NdSrCu1−_xCo_xO4−_δ and Sm_1.8Ce_0.2Cu1−_xCo_xO4+_δ catalysts.

Keywords: Perovskite-like oxide catalysts; NdSrCu; 1−; _x; Co; _x; O; 4−; _δ; Sm; _1.8; Ce; _0.2; Cu; 1−; _x; Co; _x; O; 4+; _δ; Methane combustion; Oxygen nonstoichiometry

Thermally stable Pt/K₂Ti₂O₅ as high-temperature NO_x storage and reduction catalyst by Qiang Wang; Ji Hyang Sohn; Jong Shik Chung (pp. 97-103).

Pt/K₂Ti₂O₅ is developed as a high-temperature NO_x storage and reduction (NSR) catalyst. K₂Ti₂O₅, in place of alkali metals and γ-Al₂O₃, works as both support and NO_x adsorber; and, unlike alkali-doped NSR catalysts that tend to deactivate at temperature higher than 500°C, K₂Ti₂O₅ shows stable NO_x adsorption in a high temperature range of 500–600°C. The NO_x storage and reduction performance over Pt/K₂Ti₂O₅ is studied by various means, including temperature-programmed adsorption, isothermal storage, and lean–rich cycling experiments. A maximum value of adsorbed NO_x species (close to 1.2mmol/g catalyst) is achieved at 550°C. Temperature-programmed de-sorption reveals that the adsorbed NO_x on Pt/K₂Ti₂O₅ is highly stable, with a peak at 720°C. Thermal stability investigations indicate Pt/K₂Ti₂O₅ has a much higher stability than Pt–K/TiO₂. Mechanism studies reveal that KNO₃-like compound is formed after NO_x adsorption, and that NO_x storage and reduction process on K₂Ti₂O₅ is accompanied by a structure transformation between K₂Ti₂O₅ and K₂Ti₆O₁₃.

Keywords: High temperature; NO; _x; storage-reduction; Pt/K; ₂; Ti; ₂; O; ₅; Thermal stability; Structure transformation

Zeolite framework stabilized rhodium(0) nanoclusters catalyst for the hydrolysis of ammonia-borane in air: Outstanding catalytic activity, reusability and lifetime by Mehmet Zahmakıran; Saim Özkar (pp. 104-110).

Zeolite framework stabilized rhodium(0) nanoclusters were prepared by a two steps procedure: incorporation of Rh³⁺ ions into the Zeolite-Y by ion-exchange followed by in situ reduction of Rh³⁺ ions during the catalytic hydrolysis of ammonia-borane. They are stable enough to be isolated as solid materials and characterized by HRTEM, XPS, XRD, SEM, EDX, and N₂ adsorption. These nanoclusters are isolable, bottleable, redispersible, and reusable as an active catalyst in the hydrolysis of ammonia-borane even at low temperatures. Zeolite framework stabilized rhodium(0) nanoclusters provide exceptional catalytic activity (TOF=92molH₂/molRhmin) and unprecedented lifetime (TTON=47200molH₂/molRh) in the hydrolysis of ammonia-borane at 25±0.1°C.

Keywords: Ammonia-borane; Hydrogen generation; Hydrolysis; Zeolite; Rhodium; Nanoclusters

Comparative study on electrochemical degradation of 2,4-dichlorophenol by different Pd/C gas-diffusion cathodes by Hui Wang; Jianlong Wang (pp. 111-117).

Pd/C catalysts used for the Pd/C gas-diffusion cathodes were prepared by the hydrogen gas and/or formaldehyde reduction, and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and cyclic voltammetry (CV). The electrochemical degradation of 2,4-dichlorophenol was investigated in a diaphragm electrolysis system, feeding with hydrogen gas then with air, using three different self-made gas-diffusion cathodes. The results indicated that the Pd/C gas-diffusion cathodes can not only reductively dechlorinate 2,4-dichlorophenols by feeding hydrogen gas, but also accelerate the two-electron reduction of oxygen (O₂) to hydrogen peroxide (H₂O₂) by feeding air. Therefore, both the removal efficiency and the dechlorination degree of 2,4-dichlorophenol all reached about 100% after 80min by using Pd/C gas-diffusion cathode, which were better than that of the carbon/polytetrafluoroethylene (C/PTFE) gas-diffusion cathode (no catalyst). The Pd/C catalyst prepared by the hydrogen reduction method had higher stability and catalytic activity than that prepared by the formaldehyde reduction method. By high-performance liquid chromatogram (HPLC), the main intermediates of 2,4-dichlorophenol dechlorination in the cathodic compartment were identified as 4-chlorophenol and 2-chlorophenol, which could be further dechlorinated to form phenol. Hydroquinone was the first intermediate formed from the oxidation of phenol, which was subsequently dehydrogenated to benzoquinone. The further oxidation of benzoquinone, after benzene ring cleavage, led to the formation of aliphatic carboxylic acids such as maleic, fumaric, and oxalic acids.

Keywords: Electrochemical oxidation; Gas-diffusion cathode; Pd/C catalyst; Chlorophenol; Priority pollutant

Synthesis of high-activity TiO₂ photocatalyst via environmentally friendly and novel microwave assisted hydrothermal process by Peilin Zhang; Shu Yin; Tsugio Sato (pp. 118-122).

This work focused on the synthesis of high-activity titania photocatalysts through an environmentally friendly and novel process. A high energy-efficient microwave-assisted hydrothermal method was employed to prepare TiO₂ from commercially available K₂Ti₄O₉ particles without using any organic species. The obtained titania consisted of small particles around 5nm in diameter and high specific surface areas above 200m²/g. The photocatalytic activities were evaluated by the photo-decomposition of acetaldehyde. The titania prepared through this process showed high photocatalytic activities equal to the commercial one, AEROXIDE^® TiO₂ P 25.

Keywords: Photocatalyst; Titanium dioxide; Titanate; Microwave; Hydrothermal; Acetaldehyde

Effect of chromium migration from metallic supports on the activity of diesel exhaust catalysts by W. Kaltner; M. Veprek-Heijman; A. Jentys; J.A. Lercher (pp. 123-127).

Fe–Cr–Ni and Fe–Cr–Al sintered spheres are explored as alternative support structures for automotive exhaust catalysts. Initially the activity of Pt supported on the metal support and on ceramic monoliths (cordierite) for the oxidation of CO and NO is comparable. However, after thermal aging at elevated temperatures (800°C) and extended reaction times (24h) the activity for the oxidation of NO of the catalysts supported on the Fe–Cr–Ni spheres decreases significantly, which is attributed to the migration of chromium from the metal bulk phase into washcoat. In the contrary, the aluminium present in the Fe–Cr–Al steel alloy formed a protective alumina barrier inhibiting the degradation of the catalyst after aging by blocking the migration of chromium to the surface.

Keywords: Metallic support structures; Oxidation catalysts; Cr diffusion

CO oxidation on Au nanoparticles supported on wormhole HMS material: Effect of support modification with CeO₂ by José A. Hernandez; S. Gómez; B. Pawelec; T.A. Zepeda (pp. 128-136).

This paper describes the performance of Au catalysts supported on wormhole hexagonal mesoporous silica (HMS) for the CO oxidation reaction, and the effect of support modification with cerium on the catalysts for this reaction. Supports and catalysts were characterized by N₂ adsorption–desorption, XRD, HRTEM, DRS UV–vis, TPR and XPS. The HMS material was prepared by the surfactant neutral S⁰I⁰ templating route, and its modification with cerium was performed by direct synthesis (Ce-HMS) and impregnation (Ce/HMS) methods. Gold was deposited via the deposition–precipitation method. After calcination at 573K for 3h, the Au nanoparticles with sizes in the range 3.8–4.9nm were formed. The smallest Au particles were formed on the Ce/HMS support with small crystals of CeO₂ phase on its surface, as shown by XRD. In general, Ce-containing Au catalysts were found to be more active in CO oxidation than the Ce-free Au/HMS counterpart, with the direct synthesis method of the cerium incorporation being less effective than the impregnation method. The highest activity of the Au/Ce-HMS catalyst in CO oxidation was associated with its higher gold dispersion and larger degree of coverage of HMS by CeO₂, thereby increasing the effectiveness of oxygen mobility.

Keywords: HMS; Cerium; Supported Au catalyst; CO oxidation; Support effect; Physical characterization

Ionic liquid-catalyzed selective production of hydrofluoroether: Synthesis of a third generation CFC alternative, CF₃CH₂OCHFCF₂CF₃ by Jin Hyung Kim; Sunju Kwak; Je Seung Lee; Huyen Thanh Vo; Chang Soo Kim; Ho-Jung Kang; Hoon Sik Kim; Hyunjoo Lee (pp. 137-141).

An imidazolium-based catalyst, 1-butyl-3-methylimidazolium acetate ([BMIm]AcO), was highly effective for the hydroalkoxylation reaction of hexafluoropropene with 2,2,2-trifluoroethanol to produce 1,1,2,3,3,3-hexafluoropropyl-2′,2′,2′-trifluoroethylether in high yield and selectivity.A hydrofluoroether, one of the third generation chlorofluorocarbon (CFC) alternatives, CF₃CH₂OCF₂CHFCF₃ was obtained in high yield and selectivity from the hydroalkoxylation reaction of hexafluoropropylene and 2,2,2-trifluoroethanol conducted in the presence of an imidazolium-based ionic liquid catalyst such as 1-butyl-3-methylimidazolium acetate, 1-butyl-3-methylimidazolium bicarbonate, or 1-butyl-3-methylimidazolium carbonate. By using these ionic liquids, the formation of difficult-to-remove unsaturated side products was effectively suppressed.

Keywords: Hydroalkoxylation; Hexafluoropropene; 2,2,2-Trifluoroethanol; Ionic liquid; CFC alternatives

Efficient photochemical water splitting and organic pollutant degradation by highly ordered TiO₂ nanopore arrays by Yanbiao Liu; Baoxue Zhou; Jing Bai; Jinhua Li; Jialing Zhang; Qing Zheng; Xinyuan Zhu; Weimin Cai (pp. 142-148).

The highly ordered TiO₂ nanopore arrays (TNPs) were fabricated by anodization of titanium under potentiostatic conditions at low temperature in a fluorinated dimethyl sulfoxide electrolyte with a post-sonication treatment. The TNPs possess excellent separation and transport properties of photo-generated electron/hole pair and reveal enhanced photocurrent responses and photochemical properties for water splitting and organic compound degradation. ▪We synthesized highly ordered TiO₂ nanopore arrays (TNPs) with controllable pore size and good uniformity by anodization at low temperature in fluorinated dimethyl sulfoxide (DMSO) solution with a post-sonication treatment. TNPs possess excellent separation and transport properties of photo-generated electron/hole pair and hence reveal enhanced photocurrent response and photochemical properties for water splitting and organic compound degradation. The TNPs present maximum photo-conversion efficiency for water splitting of 0.28% under AM1.5 irradiation. This value compares favorably with a maximum photo-conversion efficiency of 0.21% for TiO₂ nanotube arrays (TNAs) under the same conditions. When illuminated with 1.0mWcm⁻² UV light, the maximum photo-conversion efficiency can be increased to 22% for TNPs, which is 5% higher than TNAs. The kinetic constant of photoelectrocatalytic (PEC) degradation of methyl orange (MO) for TNPs is found to be 1.27 times as high as that for TNAs when biased at 0.5V. The visible light response of TNPs might be further improved by relevant surface modification technology.

Keywords: TiO; ₂; nanopore arrays; Water splitting; Organic compound degradation

The effect of CeO₂ on the surface and catalytic properties of Pt/CeO₂–ZrO₂ catalysts for methane dry reforming by S. Damyanova; B. Pawelec; K. Arishtirova; M.V. Martinez Huerta; J.L.G. Fierro (pp. 149-159).

The CO₂ reforming of CH₄ over Pt catalysts supported on nanocrystalline mesoporous ZrO₂ and CeO₂–ZrO₂ carriers was investigated at atmospheric pressure. The effect of CeO₂ content (1–12wt%) on the surface and catalytic properties of the catalysts was studied. It was found that the pre-treatment temperature and the concentration of CeO₂ influence on the morphology of Pt particles. The calcination temperature as high as 1073K leads to sintering of Pt particles deposited over zirconia- and CeO₂-loaded zirconia substrates. Temperature-programmed reduction (TPR) results showed good reductive properties for Pt/CeO₂–ZrO₂ catalysts due to both, the high surface shell reduction of zirconia and the synergetic effect between Pt and CeO₂. X-ray photoelectron spectroscopy (XPS) of reduced catalysts revealed the presence of different Pt oxidation state depending on the catalyst composition. Stabilization of partially oxidized platinum species by ceria was detected for the reduced Pt/CeO₂–ZrO₂ samples. An activation period was required for the stabilization of the activity of Pt/CeO₂–ZrO₂ catalysts. The high stability of Pt/CeO₂–ZrO₂ catalysts was related to the close contact between Pt and CeO₂.

Keywords: Dry reforming; Methane; Pt catalysts; Zirconia; Ceria–zirconia substrates

Spray-hydrolytic synthesis of highly photoactive mesoporous anatase nanospheres for the photocatalytic degradation of toluene in air by Minghua Zhou; Jiaguo Yu; Shengwei Liu; Pengcheng Zhai; Baibiao Huang (pp. 160-166).

Mesoporous titania nanospheres with high specific surface area and good photocatalytic activity were fabricated on a large scale by a simple spray-hydrolytic method at 90°C. The as-prepared TiO₂ spherical powders were characterized by X-ray diffraction, N₂ adsorption–desorption measurements, field emission scanning electron microscope, transmission electron microscopy, UV–visible diffuse reflectance spectra and photocurrent measurements. The photocatalytic activity was evaluated by photocatalytic decomposition of toluene in air. The effects of calcination temperatures on the microstructures and photocatalytic activity of the TiO₂ powders were investigated and discussed. The results revealed that a large amount of mesoporous titania nanospheres could spontaneously form by self-assembly of countless tiny TiO₂ primary nanoparticle during the spray hydrolysis at 90°C. The calcination temperature exhibited a strong effect on the microstructures and photocatalytic activity of the prepared titania. The 400°C-calcined sample showed the highest photocatalytic activity and was about two times higher than that of Degussa P25. At 600°C, the photocatalytic activity decreased because of the destruction of bimodal mesoporous structure of the titania and the drastic decrease of specific surface areas.

Keywords: Titania; Mesoporous; Nanospheres; Spray hydrolysis; Photocatalytic activity; Photocurrent; Toluene

Hydrocarbon production via Fischer–Tropsch synthesis from H₂-poor syngas over different Fe-Co/γ-Al₂O₃ bimetallic catalysts by Sara Lögdberg; Dewi Tristantini; Øyvind Borg; Lars Ilver; Börje Gevert; Sven Järås; Edd A. Blekkan; Anders Holmen (pp. 167-182).

Fischer–Tropsch synthesis (FTS) at 20 bar and 483K, with H₂-poor syngas (H₂/CO ratio=1.0) in order to simulate gasified biomass, was performed over Al₂O₃-supported catalysts with various ratios of Fe:Co (12wt% bimetal) prepared by co-impregnation. Co was found to be incorporated into the Fe₂O₃ phase after calcination, at least for the iron-rich samples, while no evidence of Fe incorporated into Co₃O₄ was found. Upon reduction, most probably FeCo alloys were formed in the iron-rich bimetallic samples. The degree of reduction of the catalysts showed a non-linear behavior with respect to the Fe:Co ratio, but it is obvious that Co increases the reducibility of Fe. Alloying Co with small/moderate amounts of Fe improved the FT activity compared to the 100% Co catalyst at low conversion levels. Alloying Fe with small/moderate amounts of Co lowered the FT activity, but increased the relative water–gas-shift (WGS) activity compared to the 100% Fe catalyst. However, the overall WGS activity was very low for all catalysts, even with external water addition to the feed, resulting in low FT productivities (per gram catalyst) due to the low partial pressure of H₂. A higher Fe:Co ratio in the bimetallic catalyst generally resulted in higher relative WGS activity, but did not lower the H₂/CO usage ratio to the desired value of 1.0. For the Fe-containing catalysts, the space–time yield of hydrocarbons (HCs) decreased with increasing partial pressure of water or reduced space velocity, indicating an inhibition of water on the FT activity, most often resulting in low FT productivity under the conditions with highest relative WGS activity (usage ratios closest to the inlet H₂/CO ratio). Moreover, the co-impregnation technique resulted in a surface enrichment of Fe, at least for the Co-rich samples, covering the Co sites. For the bimetallic catalysts, both FT and WGS activities rapidly declined at high partial pressure of water due to deactivation by oxidation and sintering. However, the results indicate that WGS and FT proceeded over sites of different nature in the bimetallic catalysts.The bimetallic catalysts showed essentially no synergy effects with respect to HC selectivities and olefin/paraffin ratios, which partly can be explained by the use of a sub-stoichiometric H₂/CO ratio as feed. The higher the Fe content, the lower were the C₅₊ selectivity and C₃ olefin/paraffin ratio. Water addition increased the C₅₊ selectivity and C₃ olefin/paraffin ratio and reduced the CH₄ selectivity.

Keywords: Fischer–Tropsch synthesis; H; ₂; -poor synthesis gas; Low H; ₂; /CO ratio; Water–gas-shift; Cobalt; Iron; Bimetallic catalysts; Alloy

Oxygen storage capacity of CuMO₂ (M=Al, Fe, Mn, Ga) with a delafossite-type structure by Sumio Kato; Ryu Fujimaki; Masataka Ogasawara; Takashi Wakabayashi; Yuunosuke Nakahara; Shinichi Nakata (pp. 183-188).

Delafossite-type CuMO₂ (M: trivalent cation) compounds were synthesized and found to exhibit oxygen storage capacity under oxidation/reduction cycle. The oxygen storage capacity values of CuFeO₂ and CuMnO₂ at lower temperature were larger than those of CuAlO₂, CuGaO₂- and CeO₂-based materials. The large OSC includes an oxygen uptake at low temperature attributed to formation of metallic Cu by decomposition of the delafossite phase for CuFeO₂ and CuMnO₂. In the case of CuAlO₂, which remained without decomposition below 800°C, the oxygen uptake increased with temperature up to 0.13mol-O/mol-CuMO₂. The stability of the delafossite-type CuMO₂ against oxidation/reduction cycle is affected by M³⁺. In this study, it was found that the oxygen storage behavior of CuMO₂ can be controlled by a combination of Cu and M ions.

Keywords: Oxygen storage capacity; Delafossite; Oxidation/reduction cycle

Adsorption and photocatalysed destruction of cationic and anionic dyes on mesoporous titania films: Reactions at the air–solid interface by Andrew Mills; Mubeen Sheik; Christopher O’Rourke; Michael McFarlane (pp. 189-195).

Cationic dyes, such as methylene blue (MB), Thionine (TH) and Basic Fuschin (BF), but not anionic dyes, such as Acid Orange 7 (AO7), Acid Blue 9 (AB9) and Acid Fuschin (AF), are readily adsorbed onto mesoporous titania films at high pH (pH 11), i.e. well above the pzc of titania (pH 6.5), due to electrostatic forces of attraction and repulsion, respectively. The same anionic dyes, but not the cationic dyes, are readily adsorbed on the same titania films at low pH (pH 3), i.e. well below titania's pzc. MB appears to adsorb on mesoporous titania films at pH 11 as the trimer ( λ_max=570nm) but, upon drying, although the trimer still dominates, there is an absorption peak at 665nm, especially notable at low [MB], which may be due to the monomer, but more likely MB J-aggregates. In contrast, the absorption spectrum of AO7 adsorbed onto the mesoporous titania film at low pH is very similar to the dye monomer. For both MB and AO7 the kinetics of adsorption are first order and yield high rate constants (3.71 and 1.48lg⁻¹min⁻¹), indicative of a strong adsorption process. Indeed, both MB and AO7 stained films retained much of their colour when left overnight in dye-free pH 11 and 3 solutions, respectively, indicating the strong nature of the adsorption. The kinetics of the photocatalytic bleaching of the MB–titania films at high pH are complex and not well-described by the Julson–Ollis kinetic model [A.J. Julson, D.F. Ollis, Appl. Catal. B. 65 (2006) 315]. Instead, there appears to be an initial fast but not simple demethylation step, followed by a zero-order bleaching and further demethylation steps. In contrast, the kinetics of photocatalytic bleaching of the AO7–titania film give a good fit to the Julson–Ollis kinetic model, yielding values for the various fitting parameters not too dissimilar to those reported for AO7 adsorbed on P25 titania powder.

Keywords: Photocatalysis; Dye; Methylene blue; Acid orange 7; Adsorption; Air–solid

Role of tetrahedral Co(II) sites of CoSiBEA zeolite in the selective catalytic reduction of NO: XRD, UV–vis, XAS and catalysis study by Janusz Janas; Tetsuya Shishido; Michel Che; Stanislaw Dzwigaj (pp. 196-203).

The CoSiBEA zeolites are prepared by a two-step postsynthesis method which allows to incorporate cobalt in BEA zeolite as isolated tetrahedral Co(II) species. The incorporation of Co ions in vacant T-sites and their reaction with silanol groups are evidenced by XRD and FTIR respectively. It does not generate acidic Brønsted sites as shown by FTIR of adsorbed pyridine. The state of cobalt species is characterized by DR UV–vis and XAS. These techniques allow to show that for low Co content (0.8wt%) the cobalt is present as lattice tetrahedral Co(II) species. For much higher Co content (11wt%) mainly extra-lattice octahedral Co(II) species and/or cobalt oxides are evidenced by DR UV–vis spectroscopy. Zeolite with isolated tetrahedral Co(II) species is active in SCR of NO by ethanol with selectivity towards N₂ exceeding 85% for NO conversion from 30 to 70%. When extra-lattice octahedral Co(II) species and/or cobalt oxides appear, the full oxidation of ethanol and NO by dioxygen to CO₂ and NO₂ respectively, are the main reaction pathways. Possible way of the formation of lattice tetrahedral Co(II) species in the BEA structure is proposed.

Keywords: SiBEA zeolite; Cobalt; SCR; NO; Ethanol; XRD; FTIR; DR UV–vis; XAS

FTIR study of photocatalytic degradation of 2-propanol in gas phase with different TiO₂ catalysts by J. Araña; A. Peña Alonso; J.M. Doña Rodríguez; G. Colón; J.A. Navío; J. Pérez Peña (pp. 204-213).

The photocatalytic efficiency of different TiO₂ catalysts in the degradation of 2-propanol in gas phase has been studied. The obtained efficiencies have been compared considering the distribution of rutile–anatase phases, surface area, particle size, distribution of surface hydroxyl groups and Brönsted or Lewis acid centres. The catalysts used were Degussa-P25 (TiO₂-P25), Hombikat, Millennium, Kemira and s/g-TiO₂, a catalyst prepared by a sol–gel method.The best photocatalytic behaviours have been obtained with those catalysts with higher surface area and the presence of only anatase phase (Hombikat and Millennium). A progressive deactivation of TiO₂-P25 and s/g-TiO₂ has been observed during the photocatalytic process.FTIR studies indicated that degradation mechanisms depended on the catalyst employed. Deactivation processes observed in TiO₂-P25 have been correlated with the formation of carboxylates.

Keywords: TiO; ₂; Photocatalysis; Gas phase; 2-propanol and FTIR

Effects of some carboxylic acids on the Fe(III)/UVA photocatalytic oxidation of muconic acid in water by Eva M. Rodríguez; Beatriz Núñez; Guadalupe Fernández; Fernando J. Beltrán (pp. 214-222).

Aqueous solutions of muconic acid, taken as model compound, have been exposed to UVA radiation in the presence of Fe(III) and some carboxylic acids: citric, maleic, malic, malonic, succinic, tartaric and oxalic acids. Both black light lamps and solar light were used as a source of UVA radiation. Carboxylic acids studied can be classified into three groups according to the formation or not of photocatalytic or non-photocatalytic active ferricarboxylate complexes. Only carboxylic acids forming ferricarboxylate complexes that absorb in the UVA region are able to improve the photocatalytic oxidation rate of muconic acid since their photolysis likely yields free radicals that act as oxidants. Thus, citric, tartaric, malic and oxalic acids form photoactive ferricarboxylate complexes in the UVA region while malonic acid forms complexes that do not absorb light above 320nm. Finally, succinic and maleic acids do not form complexes and, as a consequence, their presence do not improve muconic acid oxidation rate. Also, the presence of photoactive ferricarboxylate complexes improves the mineralization rate. Thus, working with black light, after 2h reaction, TOC conversion increases from about 25% in the absence of carboxylate complexes up to approx. 48 and 75% in the presence of tartrate and oxalate complexes, respectively. The results are even better when solar light is used since total mineralization is reached after 2h treatment. In this case, a linear correlation between muconic acid half life and 365nm average intensity of solar radiance was observed. Fe(III)/UVA photocatalytic oxidation resulted to be more effective than TiO₂/UVA photocatalytic oxidation at the conditions applied in this work.

Keywords: Muconic acid; UVA photocatalytic oxidation; Ferricarboxylate complexes; Fe(III)/solar light photocatalytic oxidation; Water treatment

High surface area tungsten carbide microspheres as effective Pt catalyst support for oxygen reduction reaction by Yi Wang; Shuqin Song; Vasiliki Maragou; Pei Kang Shen; Panagiotis Tsiakaras (pp. 223-228).

In the present work, the preparation of high surface area (256m²g⁻¹) tungsten carbide microspheres (TCMSs) by the aid of a simple hydrothermal method is realized and the performance of the Pt electrocatalyst supported on the as-prepared TCMSs towards the oxygen reduction reaction (ORR) is investigated. The SEM micrographs indicated that both the synthesized carbon microspheres (CMSs) and TCMSs showed perfect microsphere structure and uniform size. The EDX measurements confirmed that when the C/W mass ratio is ∼2.5/1, tungsten and carbon coexist in the microspheres. Moreover, from the XRD results, it can be found that both W₂C and WC are detected and W₂C exists as the main phase. It was found that the Pt particles are uniformly dispersed on the supports, while the corresponding average particle size is ∼3.7, 4.1 and 4.3nm for Pt/C, Pt/CMSs and Pt/TCMSs, respectively. It was also found that in terms of ORR onset potential and mass activity, the Pt/TCMSs catalyst exhibits superior performance to that of Pt/CMSs and Pt/C, enhancing the ORR catalytic activity by more than 200%. The above behavior could be attributed to its higher electrochemical surface area (ESA), as well as to the synergistic effect between Pt and tungsten carbides.

Keywords: Tungsten carbides; Proton exchange membrane fuel cells; Oxygen reduction reaction

Microkinetic modeling for hydrocarbon (HC)-based selective catalytic reduction (SCR) of NO_x on a silver-based catalyst by Ashish B. Mhadeshwar; Benjamin H. Winkler; Boris Eiteneer; Dan Hancu (pp. 229-238).

Modeling of aftertreatment systems for NO_x abatement from fuel combustion is a critical step in catalyst design. Selective catalytic reduction (SCR) is a key component in the overall aftertreatment system. In this paper, we focus on developing a detailed elementary reaction mechanism for hydrocarbon (HC)-based SCR on a silver-impregnated monolith catalyst. Rather than developing a single rate expression based on power-law fitting or Langmuir–Hinshelwood kinetics, a detailed microkinetic modeling approach is utilized to capture the essential physics of this problem. Even though the system is complicated, with more than 10 reductants along with some promoting or inhibiting effects of other species, a hierarchical approach for mechanism development is used to retain the simplicity of the mechanism in terms of computational implementation. The HC-SCR mechanism is shown to capture experimental data for all reductants, in most cases, quantitatively.

Keywords: NO; _x; SCR; Microkinetic model; Ethanol; Hydrocarbon; Silver

Efficient oxidation of thiophene derivatives with homogeneous and heterogeneous MTO/H₂O₂ systems: A novel approach for, oxidative desulfurization (ODS) of diesel fuel by Andrea Di Giuseppe; Marcello Crucianelli; Francesco De Angelis; Claudia Crestini; Raffaele Saladino (pp. 239-245).

The oxidation of benzothiophene (BTs) and dibenzothiophene (DBTs) derivatives, of model fuel (MF) and authentic diesel fuel (ADF) with homogeneous and heterogeneous rhenium catalysts and H₂O₂ has been studied to design an alternative environmentally benign oxidative desulfurization process (ODS), for oil industry. The quantitative conversion of both BTs and DBTs derivatives was obtained in several of the cases investigated, to afford the corresponding sulfones as the only recovered products in very high yield. Excellent results in terms of both conversion of substrates and yields of sulfones were also obtained during oxidation of MF and ADF. Heterogeneous rhenium catalysts were stable systems to be used for several runs without any appreciable reduction of reactivity and selectivity.

Keywords: Oxidative desulfurization; Hydrogen peroxide; Methyltrioxorhenium; Catalysis; Diesel; Sulfur

Mechanistic study of acidic and basic sites for CO oxidation over nano based Co2−_xFe_xWO₆ catalysts by A.V. Salker; S.J. Naik (pp. 246-254).

This paper deals with systematic study of M^IM^IIWO₆ (M^I=Co and M^II=Fe) mixed oxide catalysts for carbon monoxide (CO) oxidation. The catalysts were prepared by polymer based citrate sol–gel method and characterized by X-ray diffraction, thermal analysis, infrared spectroscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The average particle size calculated using TEM studies were found to be in the range 20–40nm. DC electrical conductivity showed phase transition from extrinsic to intrinsic behaviour. The ammonia and carbon dioxide adsorption over these catalysts surfaces were used as a probe to confirm the acidic and basic sites. The acidic and basic sites ascertained by temperature programmed desorption (TPD) studies carried out using thermogravimetry and differential scanning calorimetry technique. The presence of acidic and basic sites in equal ratio on the catalyst surface exhibited better CO oxidation activity as compared to unequal number of sites. The equal affinity for CO adsorption over acidic and O₂ on basic sites were found to be essential criteria for catalytic CO oxidation reaction.

Keywords: Citrate precursor; Cobalt tungstate; Iron tungstate; Temperature programmed desorption; Carbon monoxide oxidation; Acidic sites; Basic sites

Solar photocatalytic degradation of persistent pharmaceuticals at pilot-scale: Kinetics and characterization of major intermediate products by Jelena Radjenović; Carla Sirtori; Mira Petrović; Damià Barceló; Sixto Malato (pp. 255-264).

The technical feasibility and performance of photocatalytic degradation of anti-inflammatory drug acetaminophen (ACTP) and β-blocker atenolol (ATL) have been studied in a well-defined system of a pilot-plant scale Compound Parabolic Collectors (CPCs) under natural illumination. Heterogeneous photocatalysis with titanium dioxide (TiO₂) and homogeneous photocatalysis by photo-Fenton were investigated with two different matrices: distilled water and synthetic municipal wastewater treatment plant effluent (S.E.). The initial concentrations of the pharmaceuticals studied were 10mgL⁻¹, whereas the concentrations of the catalysts employed were 200mgL⁻¹ of TiO₂ and 5mgL⁻¹ of iron. Total disappearance of the parent compounds and discreet mineralization were attained in all experiments. Furthermore, kinetic parameters, release of heteroatoms and formation of carboxylic acids are discussed. The main intermediate products of photocatalytic degradation of atelonol has been structurally elucidated by tandem mass spectrometry (MS²) experiments performed at quadrupole-time of flight (QqToF) mass analyzer coupled to ultra-performance liquid chromatograph (UPLC). Six transformation products were characterized, formed by consecutive attacks of hydroxyl (OH) radical in concomitance with the disappearance of the primary compound. The proposed TiO₂ and photo-Fenton degradation route of ATL is reported for the first time.

Keywords: Acetaminophen; Atenolol; Intermediate products; Solar TiO; ₂; photocatalysis; Solar photo-Fenton; UPLC-QqToF–MS

Leaching and homogeneous contribution in liquid phase reaction catalysed by solids: The case of triglycerides methanolysis using CaO by M. López Granados; D. Martín Alonso; I. Sádaba; R. Mariscal; P. Ocón (pp. 265-272).

This work investigates two fundamental aspects faced in the heterogeneous catalytic reaction in liquid phase: leaching of species from the solid and the participation of these species in the catalytic reaction. Particularly we have focused on the transesterification of triglycerides with methanol catalysed by solid CaO to produce biodiesel. The first aspect affects the industrial application as extensive leaching may threaten the reusability and the environmental sustainability of catalyst. A method based on in situ conductivity measurements has been used to quantify the amount of solid that is solubilised. This in situ methodology is very helpful in the case of solids sensitive to CO₂ and H₂O present in ambient atmosphere, as it is the case of CaO. The amount of CaO that can be solubilised in methanol, and for the first time, in glycerol–methanol and in biodiesel–glycerol–methanol mixtures has been investigated. Larger amount of leached species was observed when glycerol is present because Ca diglyceroxide is formed due to the reaction between CaO and glycerol and this is a more soluble compound than CaO. Notwithstanding this, the solid can be reutilised for a reasonably large number of runs under the catalyst loading frequently used (larger than 1wt% referred to oil). The second investigated aspect refers whether the solid can be considered just a source of leached active homogeneous species. It was found that the homogeneous contribution arising from the leached species can be considered negligible provided that the catalyst loading is that often used (close to or larger than 1wt% referred to oil). The methodology and principles used in this work may be also relevant to other heterogeneous reaction carried out in liquid phase.

Keywords: Biodiesel; Transesterification; Deactivation; Leaching; Ca diglyceroxide; CaO; Solubility

Synthesis, characterization and activity of photocatalytic sol–gel TiO₂ powders and electrodes by Javier Marugán; Paul Christensen; Terry Egerton; Herry Purnama (pp. 273-283).

The efficiency of photoelectrocatalytic processes is strongly influenced by the electrode type and synthesis procedure. This work reports the sol–gel synthesis and characterization of TiO₂ and Fe-doped TiO₂ powders and electrodes as a function of pH and preparation temperatures and the correlation of their photoelectrochemical properties with their activity for azo dye decolourisation. pH is shown to be the variable that most influences the formation of the TiO₂ crystalline phases, the photocurrents of the electrodes, and consequently their photocatalytic activity.Electrodes synthesized at low pH and heated at temperatures below ∼600°C show a significant increase in the photocurrent recorded in the presence of methanol. This is attributed to suppression of the charge recombination rather than to a conventional current-doubling mechanism. The photocatalytic activities of the electrodes show a good correlation with the photocurrent measured in the presence of methanol. The mechanistic implications of this correlation are discussed.Iron doping reduces the activity of the sol–gel electrodes for dye decolourisation. This contrasts with previous results for bacteria disinfection, which is believed to proceed by a hydroxyl radical mechanism. Consequently, it may be that the behaviour of iron as recombination centres or as trapping sites that improve the separation charges may depend on whether the photoelectrocatalytic reaction proceeds by a hydroxyl radical mechanism, as was shown for deactivation of Escherichia coli or by direct hole-transfer, as is suggested by the parallels between dye decolouration and the electrode response to methanol that are reported in this paper.

Keywords: Sol–gel; Titania; Iron doping; Electrodes; Photocatalysis; Photoelectrocatalysis; Reactive Orange 16

Influence of alcoholic and carbonyl functions in microwave-assisted and photo-assisted oxidative mineralization by Satoshi Horikoshi; Masahiko Abe; Nick Serpone (pp. 284-287).

The microwave specific effect was examined for the TiO₂-photoassisted mineralization of substrates with alcoholic and carbonyl functions. Process enhancement was expected from the predominant absorption of microwaves by the substrates in the aqueous medium from determination of dielectric loss factors.The tendency of water-soluble organics to be photomineralized under microwave and UV irradiation was examined using model substrates bearing alcoholic (methanol, ethanol 1-propanol, ethylene glycol and glycerin) and carbonyl functions (acetone, formic acid and acetic acid). Trends were seen from the decrease of the kinetics of loss of total organic carbon (TOC) with irradiation time. Microwave thermal and specific (non-thermal) effects were probed for the photomineralization process on irradiation of TiO₂ suspensions with 2.45-GHz microwaves and UV irradiation with conventional heating under otherwise identical temperatures, and relative to UV irradiation alone to assess the thermal (TH) and microwave (MW) factors. Dielectric properties of each substrate were also determined under the experimental conditions used.

Keywords: Microwaves; Photoassisted mineralization; TiO; ₂; Alcohols; Carbonyl substrates

UVA and solar light assisted photoelectrocatalytic degradation of AO7 dye in water using spray deposited TiO₂ thin films by P.S. Shinde; P.S. Patil; P.N. Bhosale; A. Brüger; G. Nauer; M. Neumann-Spallart; C.H. Bhosale (pp. 288-294).

The degradation of the azo-dye acid orange 7 (AO7) was performed in a photoelectrochemical reactor module consisting of up to nine photoelectrochemical cells equipped with TiO₂ electrodes deposited on transparent conducting substrates. These electrodes were illuminated from the backside by UVA broadband light or sunlight. Electrical bias was applied for efficient separation of photogenerated charge carriers.Solutions of AO7 (≤1mM) in dilute supporting electrolyte (10mM HClO₄ or Na₂SO₄) were recirculated through the reactor(s) at a fixed flow rate of 12.2lh⁻¹ (mean flow velocity of 4.24cms⁻¹). AO7 disappeared following first-order kinetics. During solar irradiation, using a total electrode area of 576cm², and 1.5V bias with respect to a stainless steel counter electrode, a decay rate constant normalized to unit volume, k′, of 0.23cm³s⁻¹ was found under a photocurrent of 0.1 A. Concentrations could be decreased to the micromolar range within 1h.

Keywords: TiO; ₂; Thin film; Spray pyrolysis; Acid Orange 7; Photoelectrocatalysis

VOC oxidation over CuO–CeO₂ catalysts prepared by a combustion method by Dimitrios Delimaris; Theophilos Ioannides (pp. 295-302).

CuO–CeO₂ catalysts were prepared via a urea combustion method and their performance in the oxidation of ethanol, ethyl acetate and toluene was evaluated. XRD, H₂-TPR and N₂ physisorption were employed in catalyst characterization. The specific surface area of mixed materials was higher than the one of single oxides. In ceria-rich materials, crystalline copper oxide phases are absent and segregation of a CuO phase takes place at atomic Cu/(Cu+Ce) ratios higher than 0.25. The mixed oxides get reduced by H₂ at lower temperatures than the corresponding single oxides and copper ions promote reduction of ceria. Ethanol gets more easily oxidized than ethyl acetate, which in turn gets more easily oxidized than toluene. CuO–CeO₂ catalysts of low copper content produce very low amounts of acetaldehyde during ethanol and ethyl acetate oxidation at all conversion levels. This is augmented by the presence of water in the feed. The specific activity of Cu_xCe1−_x catalysts in the oxidation of ethanol, ethylacetate and toluene (specific rate of volatile organic compound (VOC) consumption) is lower than the one of pure CuO and CeO₂, i.e. combination of the two phases leads to suppression of intrinsic activity. On the other hand, the specific rate of CO₂ production during ethanol and ethyl acetate oxidation is also lower over CuO–CeO₂ than over CeO₂, but higher than over CuO. The larger surface area of CuO–CeO₂ catalysts counterbalances their smaller specific activity allowing complete VOC conversion at lower temperatures compared to the single oxides.

Keywords: VOC; Oxidation; Ethanol; Ethyl acetate; Toluene; Ceria; Copper oxide

Investigation on gold dispersion of Au/ZrO₂ catalysts and activity in the low-temperature WGS reaction by F. Zane; V. Trevisan; F. Pinna; M. Signoretto; F. Menegazzo (pp. 303-308).

Gold over zirconia and sulfated zirconia catalysts were tested in the water–gas shift (WGS) reaction at temperatures between 423 and 453K. Samples were characterized by N₂ adsorption analysis, XRD, TPO, TG-DTA and pulse-flow CO chemisorption. A very good linear relationship between catalytic activity and dispersion determinated by chemisorption has been evidenced. Sulfated catalysts showed higher activities than samples over plain zirconia. SO₄⁼ do not behave as promoters of the gold active phase, but they yield a larger specific surface area of the zirconia, thus favouring a better dispersion of gold nanoparticles on the support. CO amount at the reactor outlet has been checked and will be discussed.

Keywords: Chemisorption; Dispersion; Gold; Sulfated zirconia; Zirconia; WGS reaction

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Applied Catalysis B, Environmental (v.89, #1-2)