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Applied Catalysis B, Environmental (v.134-135, #)

Editorial Board (pp. i).

Contents (pp. co4).

Editorial Board (pp. co2).

Contents (pp. i).

Synthesis and characterization of Ag₃PO₄ immobilized in bentonite for the sunlight-driven degradation of Orange II by Jianfeng Ma; Jing Zou; Liangyin Li; Chao Yao; Tianli Zhang; Dinglong Li (pp. 1-6).

Display Omitted► Fine Ag₃PO₄ crystalline grains (smaller than 0.45nm) were immobilized in bentonite. ► Ag₃PO₄ photocatalytic activity and stability were improved. ► The content of silver in the photocatalyst decreased from 77.3wt% to 10.7wt%.A novel method for intercalating silver salt into bentonite interlayers is described. The very fine Ag₃PO₄ crystalline grains (less than 0.45nm) were obtained in the interlayers of bentonite (Ag₃PO₄-Ben). Ag₃PO₄-Ben was characterized by XRD, FTIR, XRF, XPS and UV–vis diffuse reflectance spectroscopy. Ag₃PO₄-Ben particles exhibited high catalytic efficiency for Orange II degradation under visible light irradiation. The photocatalytic activity is attributed to the small-sized Ag₃PO₄ crystal immobilized in bentonite and the strong adsorption of dye on bentonite. The special structure of bentonite and the microenvironment around the catalysis enhanced the stability.

Keywords: Photocatalysis; Visible light; Silver phosphate; Wastewater treatment

Heterogeneous activation of oxone with CoMg/SBA-15 for the degradation of dye Rhodamine B in aqueous solution by Longxing Hu; Fan Yang; Wencong Lu; Ying Hao; Hang Yuan (pp. 7-18).

Display Omitted► Co/SBA-15 was effective for the activation of oxone to generate sulphate radicals for degradation of the refractory Rhodamine B. ► Recyclable CoMg/SBA-15 showed much higher catalytic activity and acceptable Co leaching compared with Co/SBA-15 and Co/MgO. ► The first-order kinetics was established in heterogeneous cobalt catalyst–oxone–Rhodamine B system.A novel heterogeneous Co catalyst CoMg/SBA-15 was prepared through a two-step incipient wetness impregnation of Mg and Co into mesoporous silica SBA-15 and used for the activation of oxone to generate sulphate radicals for degrading Rhodamine B (RhB) in aqueous solution. The CoMg/SBA-15 was characterized by several techniques such as XRD, N₂ adsorption–desorption, CO₂-TPD, TEM and SEM. It was found that the CoMg/SBA-15 existed as agglomerates with the particle size more than 0.3μm, and Co and Mg occurred mainly both inside and outside the support pores in the form of cubic spinel Co₃O₄ and Mg oxide crystallites, respectively. Loading Mg into the support increased the dispersion of Co₃O₄ on the support and generated the remarkable basicity of the catalyst surface promoting the formation of surface Co–OH complex. The CoMg/SBA-15 still displayed the long-range ordered arrangement of the channels in structure with the reduced pore diameter and surface area compared with the SBA-15. The Co/SBA-15–oxone–RhB system, as a test control, was demonstrated to be efficient for the activation of oxone producing sulphate radicals for the degradation of RhB in solution. And the increase of Co/SBA-15 and oxone dosages had the positive effect on the degradation efficiency and rate, with the almost complete RhB degradation in 60min and the Co leaching concentration less than 43μg/L and the leaching percent less than 0.40% at appropriate Co/SBA-15 and oxone dosages. In addition, the degradation followed the first-order kinetics. The CoMg/SBA-15 exhibited much higher activity than Co/SBA-15 and Co/MgO with the same Co loading in degrading RhB by sulphate radicals from oxone, with nearly 100% degradation in 5min, the Co leaching concentration of 80μg/L and the leaching percent of 0.96%, and almost 100% TOC removal under appropriate conditions achieved. The CoMg/SBA-15 also displayed stable performance during 25 runs of reuse. Based on the UV–vis spectra and TOC measurement, the degradation mechanism of RhB in the presence of CoMg/SBA-15 and oxone was proposed. It is believed that CoMg/SBA-15 can be widely applied in the catalytic oxidation with oxone for the degradation of the refractory organic pollutants such as dye RhB in water.

Keywords: Heterogeneous Co catalysts; Magnesium modified catalysts; Sulphate radicals; Rhodamine B degradation; Oxone activation

Titanium dioxide photocatalytic decomposition of ethyl-S-dimethylaminoethyl methylphosphonothiolate (VX) in aqueous phase by Asuka Komano; Tsutomu Hirakawa; Keita Sato; Shintarou Kishi; Chifumi K. Nishimoto; Nobuaki Mera; Masahiro Kugishima; Taizo Sano; Nobuaki Negishi; Hiromichi Ichinose; Yasuo Seto; Koji Takeuchi (pp. 19-25).

Display Omitted► The decomposition rate of VX in TiO₂ photocatalysis in aqueous phase was accelerated with increase in alkalinity, the quantity of TiO₂ and the concentration of VX. ► The decomposition mechanism of VX was mainly controlled by P–S, C–N cleavage and oxygenation. ► The decomposition rate of VX was 30 times faster than that of DMMP.The TiO₂ photocatalytic decomposition of ethyl-S-dimethylaminoethyl methylphosphonothiolate (VX) as a real chemical warfare agent (CWA) in liquid phase has been investigated by gas chromatography/mass spectrometry (GC/MS) and liquid chromatography–tandem mass spectrometry (LC–MS/MS) analysis. The TiO₂ photocatalytic decomposition rate, r_VX, was accelerated with increase in alkalinity. The several kinds of by-products such as diisopropylamine, ethyl methylphosphonic acid, oxygenated VX and partially oxidized VX were observed. On the basis of the by-products, the TiO₂ photocatalysis were proposed as the P–S, C–N cleavage and oxygenation of VX molecule carried out mainly. The difference between r_VX and vaporized dimethyl methylphosphonate (DMMP), r_DMMP as CWA simulant was also investigated and the r_VX was 30 times faster than the r_DMMP. On the basis of the decomposition mechanism of VX and DMMP molecules, the results of the acceleration of r_VX in alkaline condition and of the comparison of r_VX and r_DMMP were also discussed.

Keywords: TiO; ₂; Photocatalysis; VX; DMMP; CWA; Decontamination

In situ growth of gold nanoparticles onto polydopamine-encapsulated magnetic microspheres for catalytic reduction of nitrobenzene by Tao Zeng; Xiao-le Zhang; Hong-yun Niu; Yu-rong Ma; Wen-hui Li; Ya-qi Cai (pp. 26-33).

Display Omitted► A core–shell Fe₃O₄@PDA–Au nanocatalyst was prepared by a simple and green method. ► PDA serves as a reductant as well as a stabilizer for the deposition of Au NPs. ► The concentration of the precursor controls the size and amount of Au NPs. ► The catalyst shows high catalytic activity and reusability in the reduction of o-NA.A simple and green method for the deposition of gold nanoparticles (Au NPs) on the surface of polydopamine (PDA)-encapsulated Fe₃O₄ nanoparticles is proposed to fabricate a core–shell Fe₃O₄@PDA–Au nanocatalyst. In the current approach, Fe₃O₄ core, about 400nm in diameter, is enveloped in a PDA coating with a thickness of about 45nm on which plenty of small Au NPs are immobilized subsequently. PDA serves as a reductant as well as a stabilizer so that additional reagents and thermo treatment are not necessary. In addition, both the size of Au NPs and the thickness of PDA layer are tunable to load more Au NPs with appropriate size on the PDA coating. The Au content on Fe₃O₄@PDA–Au nanocomposites is about 4.3wt.%, which endows the nanocatalyst with high catalytic performance in the reduction of o-nitroaniline to benzenediamine by NaBH₄ (with a conversion of 99% in 7min). Most importantly, the catalyst can be easily recycled by using an external magnetic field due to the high magnetization (39.6emug⁻¹) and shows excellent reusability (8 cycles with a conversion of >98% for o-nitroaniline). The as-prepared catalyst also show good activity for the reduction of other nitrobenzene analogs. These facilitate the practical application of the catalyst in reduction of nitroaromatic compounds.

Keywords: Gold nanoparticles; Magnetic microspheres; Dopamine; Catalyst; Nitrobenzene

Nickel cerium olivine catalyst for catalytic gasification of biomass by Singfoong Cheah; Katherine R. Gaston; Yves O. Parent; Mark W. Jarvis; Todd B. Vinzant; Kristin M. Smith; Nicholas E. Thornburg; Mark R. Nimlos; Kimberly A. Magrini-Bair (pp. 34-45).

Display Omitted► Catalytic biomass gasification with modified olivine reduces tar by 80% and char by 40%. ► The catalyst was reduced in situ by the syngas produced functioning in a chemical looping mode. ► Molecular beam mass spectrometry shows significant reduction of hydrocarbon type tars. ► The catalyst is less effective in reducing oxygenated tars or pyrolysis vapor type species.A nickel cerium modified olivine was used as a fluidized bed material in a biomass gasifier and the impact of the modification on biomass conversion, product gas composition, and tar speciation at different temperatures of oak gasification was measured. The experiments were conducted in the pyrolysis mode, without additional input of steam or oxygen (e.g., from air) into the system. In both plain and modified olivine, carbon- and hydrogen-based yields in light gases produced increased as temperature increased from 600 to 800°C. Using modified olivine resulted in significant improvement in carbon- and hydrogen-based yields and substantial reduction in tars and methane. With modified olivine, the biochar produced at 800°C was 40% less than that with plain olivine. Characterization of the fresh and post-reaction catalyst showed that a fraction of the NiO was reduced in situ in the gasifier by the syngas. In addition, the catalyst was also contributing oxygen to the environment inside the gasifier in a chemical-looping like mode, resulting in less char and coke formation than that of gasification of biomass without an additional oxygen source. Statistical analysis of molecular beam mass spectrometry data provided detailed tar speciation information under different gasification conditions. At both 650 and 800°C, the modified olivine was effective in producing more syngas either through conversion of hydrocarbon rich tars into syngas or blocking the pathway for hydrocarbon rich tar formation. However, the impact of the modified olivine in converting oxygenates (that are primarily derived from deconstruction of biomass) into deoxygenated compounds was probably minimal.

Keywords: Gasification; Tar; Olivine; Chemical looping; Syngas; Tar reforming; Pyrolysis; Biomass gasification; Biofuel

A novel high-efficiency visible-light sensitive Ag₂CO₃ photocatalyst with universal photodegradation performances: Simple synthesis, reaction mechanism and first-principles study by Hongjun Dong; Gang Chen; Jingxue Sun; Chunmei Li; Yaoguang Yu; Dahong Chen (pp. 46-54).

Display Omitted► A novel visible-light sensitive Ag₂CO₃ synthesized by a simple method. ► Universal and high-efficiency photodegradation performance. ► Evidence of photooxidation ability are provided by theory calculation. ► Mechanism and approaches of dyes are studied in detail.A novel high-efficiency visible-light sensitive Ag₂CO₃ semiconductor photocatalyst was prepared by a simple ion-exchange method based on a strategy incorporating of p-block C element into a narrow bandgap Ag₂O. This photocatalyst exhibits universal high-efficient degradation ability for typically several RhB, MO and MB dyes. Getting insight into degradation patterns of dyes over Ag₂CO₃ identifies they are self-oxidation behavior of semiconductor rather than the effect of photosensitization. The reaction mechanism investigated by a series of radical trapping experiments, not only ascertains the major photoreaction approaches of dyes on the surface of Ag₂CO₃, but also reveals the unique universality advantage that arises from selective using one of many activated species to decompose many kinds of dyes such as RhB, MO and MB. The theoretical calculation based on first-principles provides inherently essential evidences for high-efficient oxidation performance of Ag₂CO₃ photocatalyst.

Keywords: High-efficiency visible-light photocatalyst; Silver carbonate; Universal degradation performance; Theory calculation; Photodegradation mechanism; Photoreaction approach

Kinetics of the NO/NO₂ equilibrium reaction over an iron zeolite catalyst by V. Bacher; C. Perbandt; M. Schwefer; R. Siefert; T. Turek (pp. 55-59).

NO oxidation activity of iron zeolite in the presence of water vapor.Display Omitted► NO oxidation and reverse reaction over a commercial iron zeolite were studied. ► Reaction orders of 1 and 0.75 for NO and O₂, respectively, were determined. ► The reaction rate is inhibited by both NO₂ and H₂O. ► The new kinetic equation is applicable to a water concentration range from 0.1 to 2.1vol%.The steady-state kinetics of NO oxidation and its reverse reaction were studied by systematic measurements in an integral reactor at a range of temperatures, reactor pressures and reactant concentrations on a commercial iron zeolite catalyst. A Langmuir–Hinshelwood type rate equation was found to describe the experimental results with very good accuracy. The reaction orders for NO and O₂ were found to be 1 and 0.75, respectively, while the reaction was inhibited by both NO₂ and H₂O. For the first time, the kinetics developed allow the influence of water vapor on the rate of the NO/NO₂ equilibrium reaction both in the concentration range above and below 1vol% H₂O to be described.

Keywords: NO oxidation; Iron zeolite; Kinetics

The replacement of {101} by {010} facets inhibits the photocatalytic activity of anatase TiO₂ by Liqun Ye; Jinyan Liu; Lihong Tian; Tianyou Peng; Ling Zan (pp. 60-65).

When {101} was replaced by {010} facets, the most photoinduced electron and hole transfer to {001} facets and cannot be separated well under UV light irradiation. The photocatalytic oxidation and reduction all happened on {001} or {101} facets synchronously. So, the replacement of {101} by {010} facets inhibits the photocatalytic activity of anatase TiO₂.Display Omitted► Synthesis of TiO₂ crystals with {101}–{001} or {010}–{001} two facets coexistence. ► The replacement of {101} by {010} facet inhibits the photocatalytic activity of TiO₂. ► Possible charge transfer mechanism photocatalytic mechanism was suggested.Anatase TiO₂ crystals with {101}–{001} and {010}–{001} two facets coexistence were synthesized by (NH₄)₂TiF₆ acting as titanium and fluorine sources and the photocatalytic activity of the samples were investigated. The replacement of {101} by {010} facets inhibits the photocatalytic activity of anatase TiO₂. The mechanism was examined by photoluminescence spectrum, time-resolved photoluminescence spectra, field emission scanning electron microscope (FESEM) images of selected deposition of Ag, surface atoms structures and electronic band structures of anatase TiO₂ facets. The results demonstrated that photoinduced charge transfer properties between {101} facets and {001} facets resulted in the efficient charge separation. Replacing {101} by {010}, the charge transfer mechanism was altered and the photoinduced electron–hole pairs cannot be separated well. The photocatalytic activity of it has thus been inhibited.

Keywords: TiO; ₂; Photocatalytic; Facet; Time-resolved PL

NO_X storage and reduction over a perovskite-based lean NO_X trap catalyst by Crystle Constantinou; Wei Li; Gongshin Qi; William S. Epling (pp. 66-74).

Display Omitted► NO oxidation reaction orders were ∼1, 1, and −1 for NO, O₂ and NO₂, respectively, with Ea=82kJ/mol. ► Low temperature performance was limited by NO oxidation or surface diffusion. ► In comparing to a Pt-based catalyst, most of the reaction chemistry observed was the same; except. ► Low temperature region was not limiting and OSC consumption was inhibited by nitrates.Typical lean NO_X trap (LNT) catalysts contain Pt, which catalyzes NO oxidation and NO_X reduction, and an alkali or alkaline earth material for NO_X storage via nitrate formation. The catalyst is operated in a cyclic mode, with one phase of the cycle under oxidizing conditions where NO_X is trapped, and a second phase, which is reductant-rich relative to O₂, where stored NO_X is reduced to N₂. A recently developed catalyst uses a perovskite material as part of the LNT formulation for the oxidation reactions thereby eliminating the need for Pt. Pd and Rh are still added, to accommodate hydrocarbon oxidation and NO reduction, respectively. NO oxidation kinetics over the fully formulated and bare perovskite material were determined, with NO, O₂ and NO₂ orders being at or near 1, 1 and −1, respectively for both samples. The fully formulated sample, which contains Ba supported on the perovskite, was evaluated in terms of NO_X trapping ability and NO_X reduction as a function of temperature and reduction phase properties. Trapping and overall performance increased with temperature to 375°C, primarily due to improved NO oxidation, as NO₂ is more readily trapped, or better diffusion of nitrates away from the initial trapping sites or into the Ba particles. At higher temperatures nitrate stability decreased, thus decreasing the trapping ability. At these higher temperatures, a more significant amount of unreduced NO_X formed during the reduction phase, primarily due to nitrate instability and decomposition and the relative rates of the NO_X and oxygen storage (OS) component reduction reactions. Most of the chemistry observed was similar to that observed over Pt-based LNT catalysts. However, there were some distinct differences, including a stronger nitrate diffusion resistance at low temperature, a more significant reductant-induced nitrate decomposition reaction and nitrate inhibition of OSC reduction at the onset of the regeneration phase.

Keywords: NO; _X; reduction; NO; _X; trap; NO oxidation

Facile synthesis of MoS₃/carbon nanotube nanocomposite with high catalytic activity toward hydrogen evolution reaction by Tsung-Wu Lin; Chia-Jui Liu; Jeng-Yu Lin (pp. 75-82).

Display Omitted► The MoS₃/CNT nanocomposite can be easily synthesized using wet chemistry process. ► The amorphous MoS₂ reduced from MoS₃ was identified as the actual catalyst for HER. ► The HER activity of nanocomposite was highly correlated to MoS₃ morphology on CNTs. ► Nanocomposite showed an overpotential of 0.13V and a Tafel slope of 40mV/decade. ► Amorphous MoS₃ and conductive CNTs impart high HER activity and stability to the catalyst.Hydrogen has been proposed as a future energy carrier in the transition from the current hydrocarbon economy. Exploring advanced materials for electrocatalytic and photoelectrochemical water splitting has become one of the most important issues for bulk and inexpensive hydrogen production. In this study, the nanocomposite of MoS₃ and multi-walled carbon nanotubes (MWCNTs) with the high catalytic activity toward hydrogen evolution reaction (HER) was easily synthesized using wet chemistry process. With the aid of functional groups present in MWCNTs, amorphous MoS₃ nanoparticles were highly dispersed over MWCNT surface. It was found that MoS₃ on the MWCNTs was electrochemically reduced to MoS₂ before HER and thus the amorphous MoS₂ was identified as the actual catalyst for HER. Furthermore, MoS₂ with amorphous structure exhibited the higher HER activity than crystalline MoS₂ due to the fact that the former had a higher number of exposed edges. In addition, the catalytic activity of nanocomposite of MoS₃ and MWCNTs was increased with decreasing the loading amount of MoS₃ on MWCNTs and the optimal MoS₃ loading on MWCNTs was 33wt%. Based on the extensive transmission electron microscopy analysis and capacitance measurements, the catalytic activity of the nanocomposite was highly correlated to its active surface area which was controlled by MoS₃ morphology on MWCNT surface. The nanocomposite of MoS₃ and MWCNTs exhibited excellent HER activity with a small overpotential of ∼0.13V, large cathodic currents and a Tafel slope as small as 40mV/decade. The impedance measurements suggested that the high catalytic activity of nanocomposite of MoS₃ and MWCNTs was stemmed from the synergistic effect from the highly exposed edges of amorphous MoS₃ nanoparticles and the excellent electrical coupling to the conductive MWCNT network. Furthermore, it was found that the current density of this hybrid catalyst was decreased to 88% of the initial value after the continuous 500 cycling, which showed the reasonable stability in the long-term operation. The present work suggested that the highly active and stable nanocomposite of MoS₃ and MWCNTs showed a great potential as a low cost alternative to Pt in water splitting.

Keywords: Molybdenum sulfide; Carbon nanotubes; Nanocomposite; Electrocatalyst; Hydrogen evolution

Role of pH on photolytic and photocatalytic degradation of antibiotic oxytetracycline in aqueous solution under visible/solar light: Kinetics and mechanism studies by Chun Zhao; Miguel Pelaez; Xiaodi Duan; Huiping Deng; Kevin O'Shea; Despo Fatta-Kassinos; Dionysios D. Dionysiou (pp. 83-92).

Display Omitted► The photolytic and photocatalytic degradation of oxytetracycline was investigated. ► A self-photosensitization path was found at pH 8.5 and 11.0 during OTC photolysis. ► Only OTC at pH 8.5 and 11.0 had emission spectra by photo excitation. ► The internal electrostatic force of OTC was proposed as the critical mechanism. ► Five pathways were verified during the photocatalytic degradation of OTC.In this study, the photochemical degradation of the antibiotic oxytetracycline (OTC) at different pH values was investigated in aqueous solution under visible and solar light irradiation. Particular emphasis was given to the kinetics and mechanism during the photolytic and photocatalytic degradation of OTC. A comparative study of the photolysis of OTC under solar light, with different initial concentrations and in the presence of scavengers of reactive oxygen species (ROS), revealed a self-photosensitization pathway with evidence of singlet oxygen generation at pH 8.5 and 11.0 during OTC photolysis. The three-dimensional fluorescence spectra of OTC at different pH values demonstrate that OTC only exhibits significant emission spectra at pH 8.5 and 11.0. The change of the internal electrostatic force between the electron withdrawing group and the dehydrogenation moiety of OTC as a function of solution pH values was proposed as a critical factor influencing the energy states and observed reaction pathways of OTC under light irradiation. Moreover, the mechanism of photochemical degradation of OTC was investigated with nitrogen and fluorine doped titanium dioxide (NF-TiO₂) film at different pH values under visible and solar light in the presence of tert-butyl alcohol (TBA), sodium azide (NaN₃), potassium iodine (KI) and catalase as scavengers. Five pathways, including direct photolytic degradation, UV/vis light-induced photocatalytic oxidation and reduction, and visible light-induced self-photosensitized oxidation and reduction, were proposed and verified during the photocatalytic degradation of OTC with NF-TiO₂ film.

Keywords: Titanium dioxide; Fluorine doping; Nitrogen doping; Oxytetracycline; Photocatalysis; Photosensitization; Solar light; Visible light

Degradation of diclofenac by pyrite catalyzed Fenton oxidation by Sungjun Bae; Dongwook Kim; Woojin Lee (pp. 93-102).

Display Omitted► Pyrite provided proper pH condition (3–4) and appropriate amount of aqueous Fe(II). ► Diclofenac was rapidly degraded (within 120s) in pyrite suspension with H₂O₂. ► Diclofenac was finally mineralized to HCl and CO₂ by pyrite Fenton system. ► HO was identified as a main reactive radical for diclofenac degradation. ► Continuous dissolution of Fe(II) from pyrite surface enhanced diclofenac degradation.We demonstrated that diclofenac can be rapidly and completely oxidized in Fenton reaction system using pyrite as catalyst. The pH of the solution dropped from 5.7 to 4.1–3.2 with addition of different amounts of pyrite (0.5–4.0mM) as Fe(II) concentration increased to 0.07–0.52mM. Complete degradation (100%) of diclofenac was observed by pyrite Fenton system within 120s, while only 65% of diclofenac was removed by classic Fenton system in 180s. Degradation of diclofenac was significantly inhibited (100–51%) by addition of HO scavenger ( t-butanol) but not by O₂⁻ scavenger (chloroform), indicating that diclofenac was dominantly oxidized by HO produced during pyrite Fenton reaction. It was suggested that continuous dissolution of aqueous Fe(II) by pyrite Fenton reaction supported the complete degradation of diclofenac. The rate of diclofenac degradation increased as pyrite and H₂O₂ concentrations increased. 2,6-dichlorophenol, 2-chloroaniline, and 2-chlorophenol were detected as major intermediates but they were rapidly degraded in 120s. Chloride ions, ammonium, and total organic carbon measurements confirmed that diclofenac finally degraded to further oxidized forms (organic acids, HCl, and CO₂).

Keywords: Diclofenac; Pyrite; Aqueous Fe(II); Hydroxyl radical; Fenton reaction

Steam treatment on Ni/γ-Al₂O₃ for enhanced carbon resistance in combined steam and carbon dioxide reforming of methane by In Hyuk Son; Seung Jae Lee; Aloysius Soon; Hyun-Seog Roh; Hyunjoo Lee (pp. 103-109).

The steam pretreatment on Ni/γ-Al₂O₃ catalyst enhanced the carbon resistance of the catalyst, resulting in improved activity and long-term stability for combined steam and carbon dioxide reforming of methane.Display Omitted► The combined steam and carbon dioxide reforming of methane was studied. ► Carbon coke was diminished by steam treatment on conventional Ni/Al₂O₃ catalyst. ► Steam pretreatment reduced aluminum leaching which caused severe coke formation. ► Steam pretreatment improved activity and long-term stability for the reaction. ► H2/CO ratio was closer to two, which is desirable for Fischer–Tropsch reaction.Coke deposition on reforming reaction catalysts, typically Ni particles deposited on alumina supports, has been a major obstacle barring their practical industrial application. In this work, a Ni/γ-Al₂O₃ catalyst was stabilized by a pretreatment with steam at high temperature of 850°C. The steam-treated Ni/γ-Al₂O₃ catalyst showed thermodynamically possible highest conversion (98.3% for methane and 82.4% for carbon dioxide) and H₂/CO ratio of 2.01 for combined steam and carbon dioxide reforming of methane, and operated stably for 200h. The amount of deposited carbon coke was 3.6% for steam-treated catalysts whereas conventional catalysts had 15.4% of coke after 200h of the reaction. The steam pretreatment removed unstable aluminum that can otherwise leach out, which causes severe carbon deposition at the early stage of the reaction. This novel steam pretreatment enhanced the carbon resistance of the catalysts significantly, resulting in improved activity and long-term stability.

Keywords: Methane; Reforming; Nickel; Alumina; Steam; Coke

High pressure kinetics of CH₄, CO and H₂ combustion over LaMnO₃ catalyst by Gianluca Landi; Paola Sabrina Barbato; Almerinda Di Benedetto; Raffaele Pirone; Gennaro Russo (pp. 110-122).

Display Omitted► Combustion kinetics of CH₄, H₂ and CO have been studied over a LaMnO₃-based catalyst. ► Conditions relevant to GT ignition ( P up to 10bar, T up to 620°C). ► One step reaction rate expression based on MVK mechanism has been derived for each fuel. ► CO shows the highest combustion rate, methane is the less reactive.A high pressure kinetic study was carried out in a wide range of operating conditions to study the effects of pressure, temperature, fuel concentration and equivalence ratio on the catalytic combustion of methane, hydrogen and carbon monoxide over a perovskite-based catalyst. A plate type reactor configuration was chosen. This geometry allowed working in a kinetic control avoiding mass transfer limitations if appropriate experimental conditions are chosen. Since especially for GT application it is important to study the ignition phenomenon, which results to be ruled by kinetics, the study of the kinetics of CH₄, H₂ and CO catalytic combustion was carried out in a range of temperature consistent with the ignition temperatures and global reaction rate equations were derived.

Keywords: Catalytic combustion kinetics; Methane; Hydrogen; Carbon monoxide; Syngas; Perovskite catalyst; High pressure

Preparation of alumina-supported gold-ruthenium bimetallic catalysts by redox reactions and their activity in preferential CO oxidation by O.A. Kirichenko; E.A. Redina; N.A. Davshan; I.V. Mishin; G.I. Kapustin; T.R. Brueva; L.M. Kustov; Wei Li; Chang Hwan Kim (pp. 123-129).

.Display Omitted► Au⁰ nanoparticles were redox deposited on alumina-supported Ru⁰ nanoparticles. ► Au/Ru/θ-Al₂O₃ catalysts are more active in CO oxidation than Au/θ-Al₂O₃ and RuO₂/θ-Al₂O₃; Au⁰–Ru⁰ interaction suppresses the NH₃ oxidation.Lean-burn engine technology offers improved fuel economy; however, the reduction of NO_x during lean-operation continues to be a major technical hurdle in the implementation of energy efficient technology. Recently reported passive NH₃-SCR system (PASS)– a simple, low-cost, and urea-free system – has the potential to enable the implementation of lean-burn gasoline engines; however, the system suffers from CO slips during extended rich operations. The slipped CO can be easily oxidized with supplemental oxygen feed over platinum group metal (PGM)-based catalysts; however the PGM-based catalysts simultaneously oxidize the generated NH₃. This work focuses on the preparation of catalysts that can preferentially oxidize CO in the presence of NH₃.Highly active bimetallic Au-Ru/Al₂O₃ catalysts were prepared by the method of [AuCl₄]⁻ reduction by hydrogen preadsorbed on a parent monometallic Ru/Al₂O₃ catalyst serving as a carrier. The temperature-programmed reduction studies confirmed a strong interaction between the Au and Ru particles in the samples prepared by this redox method. The average size of crystallites was less than 7nm and 20nm for Au and Ru, respectively. The activity of the catalysts was studied in the reaction of oxidation of a mixture of CO with NH₃. The catalytic activity in CO oxidation was found to be higher over the bimetallic Au-Ru/Al₂O₃ catalyst compared to the monometallic Ru/Al₂O₃ and Au/Al₂O₃ catalysts. On the contrary, in NH₃ oxidation, the bimetallic Au-Ru/Al₂O₃ catalyst exhibited a decreased activity compared to the relevant monometallic catalysts. Preparation of Au-Ru/Al₂O₃ samples by the commonly used method of deposition-precipitation with urea resulted in the less catalytically active samples due to the formation of larger Au particles and their separate deposition from Ru.

Keywords: Bimetallic catalysts; Gold-ruthenium/alumina; CO oxidation; Ammonia oxidation

Air purification by gold catalysts supported on PET nonwoven fabric by Makoto Ikegami; Takanori Matsumoto; Yuka Kobayashi; Yohei Jikihara; Tsuruo Nakayama; Hironori Ohashi; Tetsuo Honma; Takashi Takei; Masatake Haruta (pp. 130-135).

Display Omitted► A shape flexible gold catalyst has been developed by using PET nonwoven fabrics. ► The whole surfaces of PET fibers were homogeneously coated with the fine Au/ZrO2 particles. ► The catalyst was active enough at room temperature for the oxidation of CO and HCHO in air. ► High catalytic activity for the removal of 0.5 ppm HCHO could be maintained longer than 136 h.A new filter-type Au/ZrO₂ catalyst was fabricated by using poly(ethylene terephthalate) (PET) nonwoven fabric as a support. Owing to its flexibility, thinness, lightness, and easy handling, this form of a catalyst is advantageous in practical use for air purification over the existing catalyst forms such as pellets and honeycombs. Zirconium oxide fine particles were first deposited on PET nonwoven fabric in the presence of 3-methacryloxypropyltrimethoxysilane to form thin layer like a fish scale and then gold nanoparticles (NPs) were deposited on ZrO₂ fine particles by deposition–precipitation method. The catalyst was active enough at room temperature and oxidized 1000ppm CO and removed 140ppm HCHO in air. The catalytic activity of Au/ZrO₂ supported on PET nonwoven fabric was also measured under similar conditions to those for practical air purification in offices and houses for the oxidation of 0.5ppm HCHO and high HCHO conversion (close to 100%) was maintained up to 136h.

Keywords: Au/ZrO; ₂; catalyst; PET nonwoven fabric; Gold nanoparticles; Air purification; Formaldehyde; CO

Low-temperature ultrasound-promoted synthesis of Cr–TiO₂-supported photocatalysts for valorization of glucose and phenol degradation from liquid phase by Juan C. Colmenares; Agnieszka Magdziarz; Krzysztof Kurzydlowski; Justyna Grzonka; Olga Chernyayeva; Dmytro Lisovytskiy (pp. 136-144).

Display Omitted► Novel supported Cr–TiO₂ photocatalysts synthesized by ultrasound-assisted impregnation technique. ► High glucose selective photo-oxidation to glucaric acid and gluconic acid. ► Photocatalysts with high potential for aqueous phase phenol selective total mineralization and solar chemicals production. ► Production of valuable compounds by a one-pot photocatalytic pathway.Novel chromium doped titania zeolite or silica supported photocatalysts were prepared via ultrasonically modified wet impregnation method. In this method, rotary evaporator was coupled with ultrasonic bath. The resulting nanomaterials were characterized by several techniques such as XRD, DR UV–vis, N₂ physisorption, XPS, ICP-MS, XRF, HRTEM–EDS and they were subsequently tested for their photocatalytic activities in liquid phase processes: selective oxidation of glucose and total mineralization of phenol. Two carboxylic acids (glucaric acid and gluconic acid) were detected as the liquid phase products in the glucose photo-oxidation and better selectivity was achieved for the photocatalyst supported on zeolite. In phenol photodegradation, although conversion rate was not meaningful (ca. 30% after 4h illumination time), negligible amounts of harmful phenol-derived compounds were detected in water compared with photodegradation using the commercial P-25 photocatalyst. This ultrasonically improved photocatalysts synthesis method was found to have a significant effect on textural properties, spherical shape, good dispersion and visible-light responsiveness of nanophotocatalysts.

Keywords: Selective glucose photo-oxidation; Phenol mineralization; Sonication; Ultrasound-assisted impregnation; Cr–TiO; ₂; Solar chemicals

Au/carbon as Fenton-like catalysts for the oxidative degradation of bisphenol A by Xuejing Yang; Peng-Fei Tian; Chengxi Zhang; Ya-qing Deng; Jing Xu; Jinglong Gong; Yi-Fan Han (pp. 145-152).

An active carbon supporting Au (Au/SRAC) catalyst has proved to an effective Fenton catalyst for the degradation of BPA.Display Omitted► A highly effective Fenton-like system consisting of Au/active carbon and hydrogen peroxide. ► Rapid degradation of organic compounds without extra energy. ► The plausible mechanism for the creation of active sites envisaged using techniques such as EPR, O₂-TPD and XPS.The development of a new method for the degradation of bisphenol A (BPA) in aqueous solution is highly desired. Oxidative degradation using hydroxyl radicals (OH) is an efficient approach for the remedy of toxic organic compounds. This paper describes the design and utilization of a new Fenton system consisting of the Au/styrene based activated carbon catalyst and hydrogen peroxide (H₂O₂) for the degradation of BPA under non-photo-induced conditions. Transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) results showed that the negatively charged Au nanoparticles were evenly distributed in a range 3.9–6.4nm dominated with (110) facet. The generation of OH over Au catalysts through the decomposition of H₂O₂ was evidenced using 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) trapped electron paramagnetic resonance (EPR). The experimental results suggested that the conversion of BPA was affected by several factors such as the loading amount of Au, pH value, reaction temperature and the initial concentration of H₂O₂. In an optimum experiment, BPA could be degraded from 110 to 10ppm within 12h. The active sites was envisaged to be negatively charged Au atoms at the interface between Au particles and carbon support, the carbon surface is enriched with dangling carbon atoms as evidenced by the O₂-temperature programmed desorption (TPD) technique. A mechanism including the redox between Au δ⁻↔Au° during the decomposition of H₂O₂ has been proposed.

Keywords: Heterogeneous Fenton catalyst; Au catalysts; Active carbon; Degradation of bisphenol A

Selective catalytic oxidation of ammonia to nitrogen over CuO-CeO₂ mixed oxides prepared by surfactant-templated method by Zhong Wang; Zhenping Qu; Xie Quan; Zhuo Li; Hui Wang; Rui Fan (pp. 153-166).

Display Omitted► Surfactant-templated method gave CuO-CeO₂ catalyst best activity for NH₃ oxidation. ► The finely dispersed CuO provided active sites for NH₃ chemisorption and activation. ► The Cu-O-Ce solid solution served as an oxygen supplier in NH₃-SCO. ► Gaseous oxygen refilled oxygen vacancy to form lattice oxygen to keep oxygen cycles.The selective catalytic oxidation of ammonia to nitrogen (NH₃-SCO) has been studied over CuO-CeO₂ mixed oxides. The active Cu component was doped into the CeO₂ by surfactant-templated method. The finely dispersed CuO, Cu-O-Ce solid solution and bulk CuO species were detected in CuO-CeO₂ mixed oxides. When the Cu loading was 10wt% and the calcination temperature was 500°C, CuO-CeO₂ catalyst exhibited the highest molar ratio of the finely dispersed CuO species and the smallest CeO₂ particles in size, and simultaneously possessed the highest level of activity. The finely dispersed CuO species was the main adsorbed sites of NH₃ molecules, and the NH_3(ad) could be further activated and transformed into NH_x species by ceria under the roles of quick change of chemical state in near-surface region and the strong electron state interaction in CuO-CeO₂ catalysts. The synergetic interaction between the two components played an important role in NH₃ activation and oxidation. In addition, the activated intermediates (NH_x) could also react with lattice oxygen provided by Cu-O-Ce solid solution to form N₂, N₂O and H₂O, which was confirmed by XPS, EPR and NH₃-TPR analysis. Moreover, gas oxygen could refill the oxygen vacancies to replenish the lattice oxygen consumed by NH_x species. The Cu-O-Ce solid solution promoted the activation of gas oxygen as well as the formation and migration of lattice oxygen in NH₃-SCO reaction, and the formed rapid reduction–oxidation cycle was essential for the higher activity of NH₃ oxidation.

Keywords: Selective catalytic oxidation of ammonia; CuO-CeO; ₂; mixed oxides; NH; ₃; activation; Oxygen migration; Active species

Inactivation of Aspergillus niger spores from indoor air by photocatalytic filters by S. Pigeot-Remy; P. Real; F. Simonet; C. Hernandez; C. Vallet; J.C. Lazzaroni; S. Vacher; C. Guillard (pp. 167-173).

Optical microscopy of the inside of a photocatalytic AC filter after the coating of fungal spores and 8 days of incubation in the dark at 25°C and 98% RH.Display Omitted► Effects of UV irradiated filters with or without TiO₂ were studied on fungal spores. ► Total inactivation of spores in TiO₂ filters without activated charcoal was observed. ► Ergosterol amount significantly decreased in TiO₂ filters after UV exposure. ► Photocatalytic filters induced a durable inhibition of the spore germination. ► Contact between TiO₂ and spores was a critical point for inactivation efficiency.The effects of UV-A and UV-C radiation on fungal spores were investigated before and after their germination in photocatalytic and non-photocatalytic air filters commonly used in heating, ventilating, and air conditioning (HVAC) systems.Immediately after the coating of spores on filters, exposure to both types of UV radiation induced the appearance of an inactivation threshold for long durations of exposure probably resulting from the presence of Aspergillus niger spores inside the activated charcoal layer. The use of a thin photocatalytic filter without activated charcoal demonstrated a better disinfection efficiency with total inactivation of the spores, due to an optimal contact between spores and TiO₂ coating.The effects of UV radiation were then assessed on spore germination for both types of filters. The inactivation of spores in illuminated photocatalytic filters resulted in an irreversible inhibition of the fungal germination under UV-A or UV-C radiation. In contrast, fungal spores were able to germinate in non-photocatalytic filters despite previous exposure to both types of UV radiation. The monitoring of ergosterol amounts, the major sterol of fungal membranes, corroborated these results.Finally, UV-A or UV-C radiation exposure of filters after spore germination had a lesser disinfection efficiency than experiments whereby spores had just been applied onto the filters, due to the absence of contact between the biological pollutants and the photocatalyst coating.Our results thus demonstrated the interest to use photocatalytic filters ensuring optimal contact between pollutants and TiO₂ coating to lead to a total inactivation of fungal spores in filters of HVAC systems.

Keywords: Indoor air; Air filtration; Disinfection; Photocatalysis; Fungal spores

Thorn-ball shaped TiO₂ nanostructures: Influence of Sn²⁺ doping on the morphology and enhanced visible light photocatalytic activity by Kishore Sridharan; Tae Joo Park (pp. 174-184).

Display Omitted► Novel strategy to prepare thorn-ball shaped TiO₂ nanostructures is demonstrated. ► Sn²⁺ doping influences both morphology and visible light photocatalytic activity. ► TiO₂ thorn-ball nanostructures have a large surface area ∼244m²g⁻¹. ► Photodegradation of Rhodamine B under visible light follows N-de-ethylation. ► TiO₂ thorn-balls are potential candidates for other important applications.A novel solution based route to synthesize thorn-ball shaped Sn²⁺ doped TiO₂ nanostructures in a large scale without the use of any reducing agents is demonstrated. White precipitates are formed instantaneously when a solution of cetyltrimethylammonium bromide with milli-molar quantities of stannous chloride dihydrate (SnCl₂·2H₂O) is mixed to a solution of titanium isopropoxide in hydrochloric acid. The morphology of the precipitates analyzed using scanning electron microscope and transmission electron microscope reveal a complex morphology with crystalline nanorods grown uniformly over the balls. When the precipitates were treated hydrothermally by suspending in ethylene glycol (EG), further reduction takes place and “Thorn-ball shaped nanostructures” with very thin and long nanorods are formed. The thorn-ball samples (ST2-HTB) showed a large surface area of ∼244m²g⁻¹ and the band-gap was ∼0.3eV narrower than that of pure TiO₂, P25 (∼3.2eV), enhancing its visible light absorption. The samples exhibited a superior efficiency in the photocatalytic degradation of Rhodamine B (RhB) under visible light irradiation to P25, and the efficiency was comparable to P25 under UV irradiation despite of their polycrystalline nature. Under visible light irradiation the degradation of RhB using thorn-ball nanostructure photocatalysts was accompanied by a gradual shift in the absorption peak owing to formation of several N-de-ethylated intermediates of RhB. Photodegradation reaction mechanism of RhB under visible light irradiation, was proposed to be initiated by the valence band holes or through the conduction band electrons. The novel strategy demonstrated here for preparing thorn-ball nanostructures opens a new horizon to design complex structures of TiO₂ for various applications.

Keywords: Thorn ball shaped nanostructures; Sn; ²⁺; doping; Titanium dioxide; Rutile; Hydrothermal; Photocatalysis; Visible light active; Photocatalyst; Rhodamine B; N de ethylation; Environmental remediation

Photoelectrocatalytic properties of Cu²⁺-doped TiO₂ film under visible light by Meihong Zhang; Shuai Yuan; Zhuyi Wang; Yin Zhao; Liyi Shi (pp. 185-192).

Display Omitted► Cu²⁺-doped TiO₂ film on stainless steel substrates was prepared. ► Cu²⁺-doped TiO₂ can be excited under visible light irradiation. ► The photo-generated electron–hole pairs can be separated efficiently by applying an external bias.Cu²⁺-doped TiO₂ film on stainless steel substrates was prepared using sol–gel method. Based on XRD and SEM analysis results, the as-prepared film was mainly in anatase phase. The film was smooth and the thickness of the film was about 2μm. The UV–vis absorption of Cu²⁺-doped TiO₂ was extended to visible range, which is favorable for the utilization of solar light. The photoelectrochemical properties of the samples were investigated via electrochemical impedance spectrum (EIS). The EIS plots demonstrated that the Cu²⁺-doped TiO₂ can be excited under visible light irradiation and the photo-generated electron–hole pairs can be separated efficiently by applying an external bias. The degradation experiments for methylene blue and methyl orange in different processes showed that the photo-response range of TiO₂ could be extended by doping Cu²⁺ ion and the photocatalytic activity of TiO₂ could be enhanced with the help of a forward bias.

Keywords: Photoelectrocatalysis; Cu; ²⁺; ion doping; TiO; ₂; film; Visible light

Stoichiometric production of aminobenzenes and ketones by photocatalytic reduction of nitrobenzenes in secondary alcoholic suspension of titanium(IV) oxide under metal-free conditions by Kazuya Imamura; Takayuki Yoshikawa; Keiji Hashimoto; Hiroshi Kominami (pp. 193-197).

Display Omitted► Photocatalytic reduction of nitrobenzenes in 2-propanol was investigated. ► Bare titanium(IV) oxide was used as photocatalyst. ► Anilines and stoichiometric amount of acetone were simultaneously obtained. ► Nitro group of nitroaromatics having other reducible group was selectively reduced. ► Nitrobenzene was reduced even under air.Photocatalytic conversion of nitrobenzenes in 2-propanol suspensions of bare titanium(IV) oxide (TiO₂) under various conditions was examined. Aniline and acetone were simultaneously produced almost stoichiometrically from a 2-propanol suspension of TiO₂ containing nitrobenzene under deaerated conditions without the use of a precious metal. Nitrobenzenes having another reducible group such as vinyl, chloro and bromo were chemoselectively reduced to corresponding aminobenzenes in 2-propanol suspensions of a TiO₂ photocatalyst with an almost stoichiometric amount of acetone. Photocatalytic reduction of nitrobenzene and oxidation of 2-propanol occurred even in the presence of oxygen, and no re-oxidation of anilines occurred.

Keywords: Photocatalyst; Titanium(IV) oxide; Stoichiometry; Nitrobenzene; Chemoselective

Synchronical pollutant degradation and H₂ production on a Ti³⁺-doped TiO₂ visible photocatalyst with dominant (001) facets by Jinguo Wang; Peng Zhang; Xi Li; Jian Zhu; Hexing Li (pp. 198-204).

An in situ Ti³⁺-doped single-crystal TiO₂ in mesoporous nanosheets with exposed (001) facets was synthesized via supercritical technology, which served as a visible photocatalyst in synchronical degradation of organic pollutants and water splitting to produce H₂. The high activity could be attributed to the enhanced light harvesting, facilitated adsorption and diffusion of reactants, and low recombination rate between photoelectrons and holes. Meanwhile, the photodegradation of organic compounds promoted the H₂ evolution from water splitting by capturing photogenerated holes.Display Omitted► Preparation of photocatalyst under supercritical conditions. ► Single-crystal TiO₂ in mesoporous nanosheets with dominant (001) facets. ► In situ Ti³⁺-doped TiO₂ visible photocatalyst. ► Synchronical pollutant degradation and H₂ production. ► Synergistic effect between photocatalytic oxidation and reduction. In situ Ti³⁺-doped TiO₂ crystal in mesoporous nanosheets with dominant (001) facets was prepared by supercritical treatment of the precursor obtained from sol–gel hydrolysis of mixed Ti(n-OC₄H₉)₄ and TiF₄. This photocatalyst exhibited high activity in synchronical pollutant degradation and water splitting to produce H₂ under visible light irradiation owing to synergistic promoting effects. On one hand, the narrowed energy band gap resulted from Ti³⁺-doping and the high surface area enhanced light harvest and reactant adsorption. On the other hand, the high crystallization degree accelerated electron transfer and thus, inhibited photoelectron–hole recombination. Furthermore, the exposed (001) facets with high surface energy favored the activation of reactant molecules. The photocatalytic degradation of organic pollutants promoted the H₂ production by consuming photogenerated holes, which inhibited their recombination with photoelectrons used for reducing H⁺ during water splitting.

Keywords: Synchronical pollutant degradation and H; ₂; production; In situ; Ti; ³⁺; -doped TiO; ₂; crystal; Mesoporous nanosheets; Exposed (0; 0; 1) facets

Photocatalytic activity of TiO₂–SiO₂ nanocomposites applied to buildings: Influence of particle size and loading by Luís Pinho; Maria J. Mosquera (pp. 205-221).

Display Omitted► Mesoporous TiO₂–SiO₂ photocatalysts have been successfully synthesized. ► A surfactant acts to coarsens the porous gel network, providing better access to photoactive sites. ► The photocatalysts give self-cleaning properties to stone and improve its robustness. ► Addition of larger and sharper titania particles with 4% (w/v) content improves effectiveness.Atmospheric pollution has an evidently adverse impact on the esthetics of urban buildings and structures. Thus, the synthesis of photocatalysts capable of removing pollutants deposited on the surface of stone and other building materials is a challenge to researchers. By a simple and low cost process we have synthesized mesoporous TiO₂–SiO₂ photocatalytic coatings that meet the requirements of outdoor application. These are new materials designed to give to the building material long-term self-cleaning and strengthening properties.We have varied the loading and size of TiO₂ nanoparticles in order to investigate their effect on the photocatalytic activity. We find that the integration of larger and sharper titania particles in a silica network with a titania content of around 4% (w/v) significantly improves self-cleaning effectiveness, due to the enhanced availability of surface photoactive sites. For a higher TiO₂ content (10%, w/v), photocatalytic action decreases because the porous volume is drastically reduced and consequently, access to photoactive sites is more difficult.

Keywords: TiO; ₂; photocatalyst; Mesoporous SiO; ₂; support; Surfactant-synthesized material; Self-cleaning properties; Building materials; Outdoor applications

Reductive removal of chloroacetic acids by catalytic hydrodechlorination over Pd/ZrO₂ catalysts by Juan Zhou; Yuxiang Han; Wenjuan Wang; Zhaoyi Xu; Haiqin Wan; Daqiang Yin; Shourong Zheng; Dongqiang Zhu (pp. 222-230).

Display Omitted► Chloroacetic acids were readily dechlorinated to acetic acid by the liquid phase catalytic hydrodechlorination over Pd/ZrO₂ catalysts. ► Pd/ZrO₂ catalyst prepared by the deposition precipitation method exhibited higher catalytic activity than that by the impregnation method. ► Dichloroacetic acid and trichloroacetic acid were dechlorinated via a combined stepwise and concerted pathway.Chloroacetic acids are common disinfection byproducts in drinking water and are of significant concern due to their strong carcinogenic, mutagenic and hepatotoxic effects. In the present study, the catalytic hydrodechlorination of chloroacetic acids (monochloroacetic acid, dichloroacetic acid and trichloroacetic acid) was investigated over supported Pd catalysts on SiO₂, ZrO₂, and activated carbon (AC) prepared by the impregnation method (denoted as im-Pd/support) and/or the deposition-precipitation method (denoted as dp-Pd/support). The catalysts were characterized by X-ray diffraction, transmission electron microscopy, measurement of point of zero charge, N₂ adsorption–desorption isotherm, H₂ chemisorption, and X-ray photoelectron spectroscopy. Characterization results showed that the points of zero charge of the supports varied. In contrast to im-Pd/ZrO₂, strong metal–support interaction was identified in dp-Pd/ZrO₂. Accordingly, im-Pd/ZrO₂ was found to be more active than im-Pd/AC and im-Pd/SiO₂, and dp-Pd/ZrO₂ exhibited higher catalytic activity than im-Pd/ZrO₂. Complete dechlorination of chloroacetic acids to acetic acid could be achieved on dp-Pd/ZrO₂ within 120min of hydrodechlorination. The hydrodechlorination rate constants of trichloroacetic acid, dichloroacetic acid, and monochloroacetic acid over dp-Pd(1.74)/ZrO₂ were 0.22, 0.16, and 0.044min⁻¹, respectively, reflecting an increase in dechlorination activity with increasing number of chlorine atoms in chloroacetic acids. It was further demonstrated that the catalytic hydrodechlorination was accomplished via a combined stepwise and concerted pathway for both trichloroacetic acid and dichloroacetic acid.

Keywords: Chloroacetic acids; Catalytic hydrodechlorination; Supported Pd catalyst; Metal–support interaction

On the role of the activation procedure of supported hydrotalcites for base catalyzed reactions: Glycerol to glycerol carbonate and self-condensation of acetone by M.G. Álvarez; A.M. Frey; J.H. Bitter; A.M. Segarra; K.P. de Jong; F. Medina (pp. 231-237).

Display Omitted► Synthesis and activation of HT supported on carbon nanofibers, ascertained by XRD. ► In the synthesis of glycerol carbonate these solids show a high activity. ► These solids are noteworthy more basic than bulk HT. ► These solids could be reused several times maintaining high activity. ► The polarity difference between bulk and supported HT is important for the activity.Bulk and carbon nanofiber supported MgAl hydrotalcites have been investigated as solid base catalysts for the synthesis of glycerol carbonate and dicarbonate and for the self-condensation of acetone. The supported materials exhibited a 300 times higher activity compared to bulk activated hydrotalcites for the transesterification. The materials could be reused while maintaining a high yield of glycerol carbonate. The activity of the mixed oxide, i.e., hydrotalcite materials after high temperature activation was considerably higher than both gas-phase and liquid phase rehydrated samples for the glycerol reactions. In contrast in the acetone self-condensation reaction the rehydrated samples were more active. This indicates that the polarity of the catalyst related to the reactant properties has a huge impact on the performance of a solid base catalyst.

Keywords: Supported hydrotalcite; Carbon nanofibers; Glycerol; Glycerol carbonate; Transesterification; Aldol condensation; Polarity

Characterization and evaluation of Ni/SiO₂ catalysts for hydrogen production and tar reduction from catalytic steam pyrolysis-reforming of refuse derived fuel by Paula H. Blanco; Chunfei Wu; Jude A. Onwudili; Paul T. Williams (pp. 238-250).

Display Omitted► Ni/SiO₂ catalysts have been used in a novel pyrolysis-catalytic reforming system. ► Impregnation type catalysts gave amorphous carbon, sol-gel gave filamentous carbon. ► Sol-gel catalysts gave highest H₂ (57.9vol.%) and lowest tar (0.24mg_tar/g_RDF). ► Tars contained mainly alkenes and alcohol functional groups. ► Major PAH were styrene, phenol, indene, cresols, naphthalene, fluorene, phenanthrene.A series of Ni/SiO₂ catalysts have been prepared and investigated for their suitability for hydrogen production and tar reduction in a two-stage pyrolysis-reforming system, using refuse derived fuel (RDF) as the raw material. Experiments were conducted at a pyrolysis temperature of 600°C, and a reforming temperature of 800°C. The product gases were analysed by gas chromatography (GC) and the condensed fraction was collected and quantified using gas chromatography-mass spectrometry (GC–MS). The effects of the catalyst preparation method, nickel content and the addition of metal promoters (Ce, Mg, Al), were investigated. Catalysts were characterised using BET surface area analysis, temperature programmed oxidation (TPO), and scanning electron microscopy (SEM). The TPO and SEM analysis of the reacted catalysts showed that amorphous type carbons tended to be deposited over the Ni/SiO₂ catalysts prepared by impregnation, while filamentous type carbons were favoured with the sol-gel prepared catalysts. The influence of catalyst promoters (Ce, Mg, Al) added to the Ni/SiO₂ catalyst prepared by the sol-gel method was found not to be significant, as the H₂ production was not increased and the tar formation was not reduced with the metal-added catalyst. The highest H₂ concentration of 57.9vol.% and lower tar amount produced of 0.24mg_tar/g_RDF; were obtained using the 20wt.% Ni/SiO₂ catalyst prepared by sol-gel. On the other hand a low catalytic activity for H₂ production and higher tar produced were found for the impregnated series of catalysts, which might be due to the smaller surface area, pore size and due to the formation of amorphous carbons on the catalyst surface. Alkenes and alcohol functional groups were mainly found in the analysed tar samples, with major concentrations of styrene, phenol, indene, cresols, naphthalene, fluorene, and phenanthrene.

Keywords: Tar; Nickel catalysts; Pyrolysis; Reforming; RDF; Syngas

The influence of nonstoichiometry on LaMnO₃ perovskite for catalytic NO oxidation by Jiahao Chen; Meiqing Shen; Xinquan Wang; Gongshin Qi; Jun Wang; Wei Li (pp. 251-257).

Display Omitted► The La_xMnO₃ ( x=0.9, 0.95, 1, 1.05, 1.11) perovskites are applied as catalysts for NO oxidation to NO₂. ► Phase transition of crystal system appears by nonstoichiometry in LaMnO₃. ► The Mn⁴⁺ content increases with lower La/Mn ratio ( x value). ► The same mechanism of NO oxidation over the La-Mn-O perovskites is observed. ► The oxygen species associated with modified Mn⁴⁺/Mn³⁺ sites of the La-Mn-O perovskites catalyzes the low temperature NO oxidation.A series of structural modified La_xMnO₃ ( x=0.9, 0.95, 1, 1.05, 1.11) perovskites used for NO oxidation was synthesized by a sol–gel method and characterized by XRD, BET, XPS, EPR and H₂-TPR. La_0.9MnO₃ sample exhibits superior activity, and a 50% NO conversion at 250°C is obtained. XPS and EPR results reveal a higher Mn⁴⁺/Mn³⁺ ratio in Mn-rich samples, which induce more active oxygen bonding to Mn⁴⁺ due to the need for balancing the chemical states and stabilizing the structure. Easily regenerated oxygen associated with Mn⁴⁺ catalyzes the low-temperature NO oxidation. The constant activation energy (44.8kJ/mol) obtained in the kinetics tests indicates the same mechanism of NO oxidation operated on all the samples.

Keywords: NO oxidation; Mn; ⁴⁺; /Mn; ³⁺; ratio; Nonstoichiometry; LaMnO; ₃; perovskite

Hydrothermal activation of silver supported alumina catalysts prepared by sol–gel method: Application to the selective catalytic reduction (SCR) of NOx by n-decane by Carolina Petitto; Hubert P. Mutin; Gérard Delahay (pp. 258-264).

Display Omitted► The preparation of mesoporous silver alumina catalysts by sol–gel process is reported. ► Most active catalysts were achieved after hydrothermal treatment at high temperature. ► Water vapour is a redispersing agent of silver particles at high temperature. ► The addition of niobium increases the density of acid sites. ► A low temperature active catalyst has been designed for the HC-SCR.2wt% Ag– and 2wt% Ag–1.5wt% Nb mesoporous alumina catalysts were prepared by non-hydrolytic sol–gel process. Silver accessibility is enhanced by calcination at high temperature. By performing calcination in presence of water vapour, silver particles are well dispersed and interact more strongly with the alumina surface and activity in n-decane-SCR of NOx is greatly improved. Moreover, the addition of niobium in the starting material leads to more efficient catalysts and enhances mainly the low temperature activity.

Keywords: Hydrothermal activation; Sol–gel catalysts; HC-SCR; Nitrogen monoxide; n; -Decane; Supported alumina; Silver

Catalytic reforming of activated sludge model compounds in supercritical water using nickel and ruthenium catalysts by Pooya Azadi; Elie Afif; Hooman Foroughi; Tingsong Dai; Faraz Azadi; Ramin Farnood (pp. 265-273).

Display Omitted► Higher gas yields obtained from model compounds compared to sludge. ► Methane and carbon dioxide are almost at a quasi-equilibrium state. ► Humic substances are relatively more difficult to decompose.We report the catalytic supercritical water reforming of model compounds of activated sludge at 380°C using Raney nickel, Ni/α-Al₂O₃, Ru/C, and Ru/γ-Al₂O₃ catalysts. The model compounds were glucose, glycine, glycerol, lauric acid and humic acid, representing carbohydrates, proteins, alcohols, fatty acids and humic substances, respectively. Using Raney nickel as the catalyst, the carbon conversions decreased with the following order: glycerol>glucose>glycine>lauric acid>humic acid. The conversion generally increased with reduction in the number of CC bonds presented per unit mass of the molecules, except for the glycine that contains a nitrogen atom in its structure. Comparison of the experimental yields of methane with the equilibrium values calculated at the corresponding conversions revealed that, in the presence of Raney nickel, methane is almost at a quasi-equilibrium state. Moreover, using binary mixtures of the above model compounds as feedstock, the interactions between these model compounds were investigated. At low catalyst loadings, the presence of humic acid in the binary mixtures resulted in lower carbon conversions compared to the expected values based on the rule of mixtures. Higher gas yields were obtained from the decomposition of these model compounds compared to an activated sludge feedstock. Addition of sludge ash decreased the gasification yields of glucose and glycerol and increased the yields obtained from glycine. Furthermore, since algae are comprised of lipids, proteins, and carbohydrates, the findings of this study also provide a better understating of the catalytic gasification of such feedstock in supercritical water.

Keywords: Activated sludge; Heterogeneous catalysis; Hydrogen; Gasification; Supercritical water

The influence of the Ti⁴⁺ location on the formation of self-assembled nanocomposite systems based on TiO₂ and Mg/Al-LDHs with photocatalytic properties by E.M. Seftel; M. Mertens; P. Cool (pp. 274-285).

Display Omitted► TiO₂/LDH nanocomposites were obtained using the memory effect property of LDH materials. ► The influence of the Ti⁴⁺ location on the quality of the products was investigated. ► Up to 93% of dye could be removed by the obtained TiO₂/LDH nanocomposites.Herein, we report the formation of TiO₂/LDH self-assembled nanocomposite systems using the memory effect property of the layered clay-type materials. Two different synthesis approaches, based on the modification of the initial brucite-like sheets composition, were used in order to investigate the influence of the Ti⁴⁺ location on the quality of the final products: the reconstruction of a calcined MgAl-LDH in a TiOSO₄· xH₂O aqueous solution and the reconstruction of a calcined MgAlTi-LDH in aqueous solution. The reconstruction process, monitored using X-ray diffraction, IR spectroscopy, UV–vis diffuse reflectance spectroscopy, SEM and thermal analysis, produced different structural changes strongly related with the brucite-like sheets composition. The photocatalytic activity of the obtained nanocomposite systems was evaluated for the degradation of the methyl-orange (MO) dye. An intimate contact has been created between the anatase and the brucite-like sheets in the nanocomposite systems, which had a direct influence on the HO radical production enhancing thus the photocatalytic performances. When comparing the as-synthesized catalysts, the MgAlTi-LDH solid manifests very powerful photocatalytic effect due to the segregation of small, well defined TiO₂ nanoparticles on the highly hydroxilated layered surface. Up to 93% of the dye could be removed by a TiO₂/LDH-type nanocomposite system. Controlled thermal treatment of photocatalytic systems allowed us to tailor the quality of the photocatalytic active sites deposited on the layered support. The use of the TiO₂/LDHs nanocomposites showed multiple advantages highlighted by the increased activity per mass, higher efficiencies at a decreased solid/liquid ratio, decreased reaction times, reduced agglomeration and easy to separate at the end of the processes.

Keywords: Layered double hydroxides; Brucite-like sheets composition; Anatase; Nanocomposites; Photocatalysis

A new heterojunction Ag₃PO₄/Cr-SrTiO₃ photocatalyst towards efficient elimination of gaseous organic pollutants under visible light irradiation by Jianjun Guo; Shuxin Ouyang; Peng Li; Yuanjian Zhang; Tetsuya Kako; Jinhua Ye (pp. 286-292).

Display Omitted► A new photocatalyst Ag₃PO₄/Cr-SrTiO₃ was successfully synthesized and characterized. ► High efficiency in IPA photodegradation was obtained under visible light irradiation. ► The mechanism relies on electron-transfer and a new chemical reaction process. ► Mass ratio and calcination temperature are important for constructing heterojunction. ► Proper band structures and well interfacial connection should be controlled.A new heterojunction Ag₃PO₄/Cr-SrTiO₃ was designed to eliminate the gaseous pollutants under visible light irradiation. The phase compositions, optical properties, and morphologies of the heterojunction photocatalysts were systematically investigated via powder X-ray diffraction, UV–Visible absorption spectroscopy, scanning electron microscopy and energy-dispersive X-ray spectroscopy, and transmission electron microscopy. The photodegradation of Isopropyl alcohol (IPA) was carried out to test the photocatalytic activity of the heterojunction. The results revealed that the heterojunction exhibited considerably improved efficiency in IPA photodegradation (CO₂, 13.2ppmh⁻¹) in comparison with pure Ag₃PO₄ (CO₂, 0.4ppmh⁻¹) and Cr-SrTiO₃ (CO₂, 1.9ppmh⁻¹) under visible light irradiation. In addition, the effects of mixing ratio and calcination temperature of the heterojunction were studied. The highest activity was observed in the Ag₃PO₄/Cr-SrTiO₃ heterojunction with the mass ratio of 1:4 (Ag₃PO₄:Cr-SrTiO₃) sintered at 500°C. An investigation of energy-band structure via valence-band X-ray photoelectron spectrum indicates that the conduction band (CB) and valence band (VB) of Ag₃PO₄ are both more positive than that of Cr-SrTiO₃, which facilitates the separation and transfer of photogenerated electrons and holes between the two photocatalysts.

Keywords: Ag; ₃; PO; ₄; /Cr-SrTiO; ₃; Heterojunction; IPA photodegradation; Photocatalysis

Preparation of p–n junction Cu₂O/BiVO₄ heterogeneous nanostructures with enhanced visible-light photocatalytic activity by Wenzhong Wang; Xiangwei Huang; Shuang Wu; Yixi Zhou; Lijuan Wang; Honglong Shi; Yujie Liang; Bin Zou (pp. 293-301).

Display Omitted► Cu₂O/BiVO₄ heterogeneous nanostructures were firstly realized. ► Cu₂O/BiVO₄ was used for photocatalytic degradation of methylene blue. ► The photocatalytic activity of heterogeneous nanostructures is greatly enhanced. ► Photocatalytic mechanism on Cu₂O/BiVO₄ under visible light irradiation was proposed. ► The p–n junction retards the recombination of photo-induced charges.p–n junction Cu₂O/BiVO₄ heterogeneous nanostructures for enhancement of visible-light photocatalytic properties of BiVO₄ nanocrystals have been successfully prepared through coupling a hydrothermal process with polyol strategy. The assembly of p-type Cu₂O nanoparticles produces a large number of nano p–n junction heterostructures on the surface of the BiVO₄ nanocrystals, where Cu₂O and BiVO₄ form p- and n-type semiconductors, respectively. The experimental results reveal that these p–n junction Cu₂O/BiVO₄ heterogeneous nanostructures exhibit much higher visible-light photocatalytic activities than the individual BiVO₄ nanocrystals for the degradation of model dyes methylene blue and colorless organic phenol under visible light irradiation. The enhanced photocatalytic efficiencies are attributed to the charge transfer from n-type BiVO₄ to the attached p-type Cu₂O nanoparticles, which effectively reduces the recombination of electrons and holes, leading to the enhancement of the photocatalytic properties of the heterostructure nanostructures. These new p–n junction heteronanostructures are expected to show considerable potential applications in solar-driven wastewater treatment.

Keywords: p–n junction; Degradation; Photocatalysis; Preparation; Cu; ₂; O/BiVO; ₄; heterogeneous nanostructures

From biomass to pure hydrogen: Electrochemical reforming of bio-ethanol in a PEM electrolyser by A. Caravaca; A. de Lucas-Consuegra; A.B. Calcerrada; J. Lobato; J.L. Valverde; F. Dorado (pp. 302-309).

Display Omitted► A bioethanol PEM electrolysis cell was developed for pure H₂ production. ► The main reaction conditions were optimized in order to maximize the H₂ production. ► The system was able to be in situ regenerated after some polarization cycles. ► EIS characterization demonstrated the nature of the cell deactivation/regeneration. ► XRD demonstrated the unchanged morphology of the electrodes after the cell operation.This study reports, for the first time in literature, the electrochemical reforming of a 2nd generation bio-ethanol solution (a real waste of the wine industry) for pure hydrogen production in a low temperature PEM electrolysis cell. Thereby, the main reaction parameters were studied and optimized in order to enhance the hydrogen production rate at the cathodic side of the cell. Moreover, long-term reaction experiments were carried out, together with some regeneration steps, in order to study the behavior of this system for its possible practical application. The observed reversible deactivation was discussed and supported by the electrochemical and the physico-chemical characterization of the electrodes. The results demonstrated that the origin of the observed deactivation was due to an increase in the polarization resistance of the anode due to the adsorption of reaction intermediates that can be removed by electro-oxidation during the regeneration step of the anode. The durability of the electrodes under the bioethanol electro-reforming conditions was also demonstrated in terms of thermal degradation and catalyst morphology modification. These results demonstrate the potential interest of a novel route for pure hydrogen production from biomass via electrochemical reforming.

Keywords: H; ₂; production; Electro-reforming; Electrolysis; Bioethanol; PEM electrolysis; Electrocatalysis

The effect of A-site substitution by Sr, Mg and Ce on the catalytic performance of LaMnO₃ catalysts for the oxidation of vinyl chloride emission by Chuanhui Zhang; Wenchao Hua; Chao Wang; Yanglong Guo; Yun Guo; Guanzhong Lu; Alexandre Baylet; Anne Giroir-Fendler (pp. 310-315).

Display Omitted► LaMnO₃ and La_0.8A_0.2MnO₃ (A=Sr, Mg and Ce) were prepared by co-precipitation method. ► The A-site substitution modified the amounts of Mn⁴⁺ and adsorbed oxygen on the surface. ► No by-products were formed but only CO₂, H₂O and HCl. ► La_0.8Ce_0.2MnO₃ presented the best catalytic performance for vinyl chloride abatement. ► Reducibility and surface adsorbed oxygen were the main parameters.Catalytic oxidation of vinyl chloride (VC) emission was carried out over LaMnO₃ and La_0.8A_0.2MnO₃ (A=Sr, Mg and Ce) perovskite oxides synthesized via co-precipitation method. Numerous characterization techniques were performed to investigate the relationship between the catalytic performance and its physicochemical properties. It was found that the partial substitution of lanthanum by cerium and magnesium had a positive effect on the catalytic performance for VC oxidation, whereas strontium involved a negative effect. Under the reaction conditions (VC concentration=1000ppm, GHSV=15,000h⁻¹), the overall catalyst ranking in terms of the catalytic activity from the best to the worst performance was La_0.8Ce_0.2MnO₃>La_0.8Mg_0.2MnO₃>LaMnO₃>La_0.8Sr_0.2MnO₃ with regard to the temperature of T₅₀ and T₉₀. The Ce-doped perovskite catalyst showed the optimum catalytic performance due to its higher specific surface area and its ability to promote the low-temperature reducibility. Moreover, as the active species, the increased surface adsorbed oxygen was also responsible for the enhancement of the catalytic performance.

Keywords: Vinyl chloride; Catalytic oxidation; Perovskite catalyst; Reducibility; Adsorbed oxygen

Adsorption and catalytic thermolysis of gaseous urea on anatase TiO₂ studied by HPLC analysis, DRIFT spectroscopy and DFT calculations by Andreas M. Bernhard; Izabela Czekaj; Martin Elsener; Oliver Kröcher (pp. 316-323).

Display Omitted► High-purity gaseous urea was adsorbed onto anatase TiO₂ at 100°C. ► Urea adsorption was confirmed by HPLC analysis and by DRIFT spectroscopy. ► DFT calculations indicated two different adsorbed states of urea.High-purity gaseous urea was generated by passing a carrier gas at 100°C through an inert cordierite monolith impregnated with urea, and the gaseous urea adsorbed onto anatase TiO₂ catalyst samples. Urea adsorption on the catalysts was confirmed by two independent methods: high performance liquid chromatography (HPLC) analysis and diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy. Moreover, urea adsorption at the anatase (101) surface was studied by density functional theory (DFT) calculations. In combination with the DRIFT spectra, the DFT calculations indicated that two different adsorbed states of deprotonated urea were present on the catalyst simultaneously: in one adsorbed state, urea bound at one Ti site, and in the other adsorbed state urea was rotated and bound at two Ti sites. The confirmation of urea adsorption on anatase supports our previous finding that urea thermolysis is a catalytic reaction.

Keywords: Urea adsorption; Anatase TiO; ₂; Urea thermolysis; HPLC; DRIFT; DFT; Urea-SCR

Catalytic degradation of caffeine in aqueous solutions by cobalt-MCM41 activation of peroxymonosulfate by Fei Qi; Wei Chu; Bingbing Xu (pp. 324-332).

Cobalt was incorporated into the structure of MCM41 (i.e. Co-MCM41). As a catalyst, Co-MCM41 not only activated PMS to degraded caffeine, but also mineralizes the corresponding intermediates. Less cobalt leaching was observed, indicating that the heterogeneous reaction dominated the caffeine decay rather than the homogeneous one that made the reuse of catalyst highly feasible. Furthermore, nine major intermediates generated in this process were identified and the degradation pathway was proposed. Among detected intermediates, three were firstly detected as intermediates of caffeine.Display Omitted► Co-MCM41/peroxymonosulfate exhibited an effective performance and low leaching. ► The heterogeneous reaction dominated the caffeine decay. ► Intermediates and pathway of caffeine were identified.^{In this study, the performance of caffeine degradation and mineralization in aqueous phase by a catalyst that was prepared by incorporating cobalt into the structure of MCM41 (i.e. Co-MCM41) in activating peroxymonosulfate (PMS) was explored. Experimental results showed that Co-MCM41 activated PMS not only degraded caffeine, but also mineralized the corresponding intermediates successfully. The surface and structure properties of Co-MCM41 were characterized by several analytical methods. The leaching of cobalt ions in this process was very low, and the heterogeneous reaction dominated the caffeine decay rather than the homogeneous one, which made the reuse of catalyst highly feasible. According to the result of using quenchers, both OH} and SO₄⁻ were found in this process and the latter was the major oxidant species. Furthermore, nine major intermediates generated in this process were identified and the degradation pathway was proposed.

Keywords: Co incorporated MCM41; Peroxymonosulfate activation; Advanced oxidation process; Caffeine; Sulfate radicals

Photocatalytic oxidation of propene in gas phase at low concentration by optimized TiO₂ nanoparticles by M. Ouzzine; M.A. Lillo-Ródenas; A. Linares-Solano (pp. 333-343).

Display Omitted► Crystalline TiO₂ nanoparticles can be obtained by sol–gel at low temperature. ► The hydrolyzing agent and thermal treatment have an important effect. ► These samples have been used for gas phase propene oxidation at low concentration. ► Prepared nanoparticles posses higher photocatalytic activity than Degussa P-25. ► These samples are very active, especially with the 365nm light source.In the present study, nanocrystalline titanium dioxide (TiO₂) was prepared by sol–gel method at low temperature from titanium tetraisopropoxide (TTIP) and characterized by different techniques (gas adsorption, XRD, TEM and FTIR). Variables of the synthesis, such as the hydrolyzing agent (acetic acid or isopropanol) and calcination temperatures (300–800°C), were analyzed to get uniform size TiO₂ nanoparticles. The effect that these two variables have on the structure of the resultant TiO₂ nanoparticles and on their photocatalytic activity is investigated. The photocatalytic activities of TiO₂ nanoparticles were evaluated for propene oxidation at low concentration (100ppmv) under two different kinds of UV light (UV-A∼365nm and UV-C∼257.7nm) and compared with Degussa TiO₂ P-25, used as reference sample. The results show that both hydrolyzing agents allow to prepare TiO₂ nanoparticles and that the hydrolyzing agent influences the crystalline structure and its change with the thermal treatments. Interestingly, the prepared TiO₂ nanoparticles possess anatase phase with small crystalline size, high surface area and higher photocatalytic activity for propene oxidation than commercial TiO₂ (Degussa P-25) under UV-light. Curiously, these prepared TiO₂ nanoparticles are more active with the 365nm source than with the 257.7nm UV-light, which is a remarkable advantage from an application point of view. Additionally, the obtained results are particularly good when acetic acid is the hydrolyzing agent at both wavelengths used, possibly due to the high crystallinity, low anatase phase size and high surface oxygen groups’ content in the nanoparticles prepared with it, in comparison to those prepared using isopropanol.

Keywords: Titanium dioxide; Sol–gel method; Photocatalyst; Propene

A highly efficient process for transforming methyl mercaptan into hydrocarbons and H₂S on solid acid catalysts by Edouard Huguet; Bernard Coq; Robert Durand; Catherine Leroi; Renaud Cadours; Vasile Hulea (pp. 344-348).

Display Omitted► A new process for the conversion of CH₃SH into H₂S and hydrocarbons (M2TH) is described. ► Protonic zeolites are very active in the M2TH process. ► At 823K, CH₃SH is fully converted into H₂S, C1–C3 alkanes, aromatics and coke on H-ZSM-5. ► Product distribution and stability of the catalysts depend on the zeolite topology.The catalytic conversion of CH₃SH and CH₃SCH₃ (DMS) on protonic zeolites H-ZSM-5, H-Y and H-ferrierite was studied in a gas flow reactor from 423 to 823K. Below 700K, CH₃SH is converted at equilibrium into DMS and H₂S. Above 700K, light alkanes (C1–C3), benzene, toluene and xylene appear alongside H₂S in the gas phase, and a carbonaceous deposit builds up on the catalyst. DMS is assumed to be the intermediate in the CH₃SH transformation into H₂S and hydrocarbon species. At 823K, the CH₃SH conversion is total on H-ZSM-5, and only partial on H-Y and H-ferrierite. These are selective to alkanes, and produce large quantities of coke. In contrast, much less coke builds up on H-ZSM-5, which is also more selective to aromatics. After calcination in air flow at 823K, the spent H-ZSM-5 sample recovers the properties of the fresh catalyst. Similarities and differences with the methanol-to-hydrocarbons process are discussed.

Keywords: Methyl mercaptan; Zeolites; Natural gas; Catalysis; Desulfurization

Tailoring Cu valence and oxygen vacancy in Cu/TiO₂ catalysts for enhanced CO₂ photoreduction efficiency by Lianjun Liu; Fei Gao; Huilei Zhao; Ying Li (pp. 349-358).

Display Omitted► Cu/TiO₂ photocatalysts are fabricated for CO₂ photoreduction with water vapor. ► Cu valence and oxygen vacancy are tailored by thermal treatment in He or in H₂. ► Photo-activity in the order: H₂-pretreated>He pretreated>unpretreated. ► Mixed Cu⁺/Cu⁰ promote electron–hole separation more effectively than Cu⁺ and Cu²⁺. ► CO₂⁻ species is a CO₂ reduction intermediate according to in situ DRIFTS.The incorporation of Cu species in TiO₂ photocatalysts is critical in photocatalytic CO₂ reduction to fuels, but the effect of Cu valence is poorly understood. In this work, Cu/TiO₂ (P25) nanoparticle catalysts were prepared by a simple precipitation and calcination method. The as-prepared Cu/TiO₂ sample was dominated by Cu²⁺ species. Thermal pretreatment of the as-prepared samples in He and H₂ atmosphere resulted in the transition to a surface dominated by Cu⁺ and mixed Cu⁺/Cu⁰, respectively, confirmed by in situ X-ray photoelectron spectroscopy (XPS) and diffuse-reflectance infrared Fourier transform spectroscopy (DRIFTS) analyses. These thermal pretreatments in reducing atmospheres also induced the formation of defect sites such as oxygen vacancies and Ti³⁺. The various Cu/TiO₂ catalysts were tested in CO₂ photoreduction with water vapor under simulated solar irradiation, and their activities were in the order of as-prepared (unpretreated)2-pretreated. Compared with unpretreated TiO₂ (P25), the H₂-pretreated Cu/TiO₂ demonstrated a 10-fold and 189-fold enhancement in the production of CO and CH₄, respectively. This significant enhancement was mainly attributed to the synergy of the following two factors: (1) the formation of surface defect sites promoting CO₂ adsorption and subsequent charge transfer to the adsorbed CO₂; (2) the existence of Cu⁺/Cu⁰ couples that facilitate electron and hole trapping at different sites.

Keywords: CO; ₂; reduction; Photocatalysis; Cu valence; TiO; ₂; Oxygen vacancy

Autothermal steam reforming of ethanol over La₂Ce2−_xRu_xO₇ ( x=0–0.35) catalyst for hydrogen production by Sheng-Feng Weng; Yun-Hsin Wang; Chi-Shen Lee (pp. 359-366).

Pyrochlore phase La₂Ce_1.8Ru_0.2O₇ is a new catalyst for autothermal steam reforming reaction. The catalyst as prepared shows stable hydrogen production rate 2.01×10⁻³mols⁻¹g_cat⁻¹.Display Omitted► Pyrochlore phases La₂Ce2−_xRu_xO₇ ( x=0–0.35) were prepared by sol–gel method. ► The metal–metal interaction between Ru and La ions was observed on XPS analyses. ► La₂Ce_1.8Ru_0.2O₇ revealed the better activity on autothermal steam reforming of ethanol. ► The amount of Ru loading was reduced while the catalytic activity was maintained. ► The catalysts as prepared kept evenly distributed Ru ions before and after the tests.Pyrochlore phases solid solutions, La₂Ce2−_xRu_xO₇ ( x=0–0.35) were prepared with a sol–gel process and used as catalysts for the autothermal steam reforming of ethanol. The samples as prepared were characterized with powder X-ray diffraction (PXRD), X-ray photoelectron spectra (XPS), and temperature-programmed reduction (TPR). The XPS and TPR spectra revealed the effect of doped Ru n⁺ to oxidation states of La and Ce sites. The low temperature reduction ability and relative concentration of Ce⁴⁺ ions are increased as the cell-dimension decreased. Tests of catalytic activity showed that the reforming performance of La₂Ce2−_xRu_xO₇ catalysts was affected by the Ru/Ce loading ratio. For all catalysts, partial oxidation was favored at a large C/O composition; incomplete ethanol conversion was observed for C/O≥0.7. The optimized catalyst was La₂Ce_1.8Ru_0.2O₇ with hydrogen production rate (rH2) 2.01×10⁻³mols⁻¹g_cat⁻¹ (autothermal temperature ∼600°C and 97% ethanol conversion at C/O=0.6). The catalyst exhibited stablerH2 over 26h of the reaction with ethanol conversion >95%.rH2 of the catalyst gradually decreased thereafter because LaAlO₃ started to formed and affected catalytic process. For the catalyst, the Ru ions remained well dispersed before and after the AESR reaction.

Keywords: Autothermal steam reforming of ethanol; Pyrochlore; Solid solution; Ruthenium

Selective catalytic reduction of NO with NH₃ over Cr-ZSM-5 catalysts: General characterization and catalysts screening by F. Ayari; M. Mhamdi; J. Álvarez-Rodríguez; A.R. Guerrero Ruiz; G. Delahay; A. Ghorbel (pp. 367-380).

. Cr-ZSM-5 catalysts exhibited promising catalytic properties in SCR of NO with NH3 at low temperatures. Higher catalytic activities of Cr-ZSM-5 catalysts provided from a synergy between two crucial preparation parameters: Si/Al molar ratio and the nature of Cr precursor.Display Omitted► Cr-ZSM-5 catalysts (Cr/Al=1) were tested in SCR of NO with NH₃. ► Cr₂O₃ morphology was elucidated by UV–vis DR spectroscopy ( B and μ-parameters). ► Agglomerates of crystalline and amorphous Cr₂O₃ are inefficient in SCR of NO. ► Poly and/or monochromates, Cr₂O₃ clusters and Cr oxo-cations are active species. ► Cr-ZSM-5 catalysts, being abandoned, are promising in low-temperature SCR.Cr exchanged ZSM-5 catalysts (Cr/Al=1) prepared by solid-state ion exchange were tested in SCR of NO with ammonia. Since CrCl₃ precursor sublimates during the solid-state reaction, chromate species were stabilized in the exchange sites of H⁺-ZSM-5 (Si/Al=15) and Cr₂O₃ formation is, therefore, limited. However, using Cr nitrate and NH₄⁺-ZSM-5 (Si/Al=26) zeolite, massive particles of α-Cr₂O₃ occupied the catalyst surface. At the contrary, well-dispersed particles of Cr₂O₃ were detected with H⁺-ZSM-5 and Cr nitrate precursor. Starting from Cr acetate precursor, agglomerates of amorphous oxide were detected with H⁺-ZSM-5 like support. In the temperature range 50–300°C, Cr chloride and Cr nitrate precursors and H⁺-ZSM-5 led to highly active catalysts, while Cr nitrate and NH₄⁺-ZSM-5 led to a poorly active catalyst. However, catalysts issued from Cr acetate are promising in SCR but inefficient agglomerates of oxide (amorphous or crystalline chromia) could be avoided with NH₄⁺-ZSM-5 like support.

Keywords: Ammonia; Cr-ZSM-5; Selective catalytic reduction (SCR); Solid-state ion exchange; UV–vis DRS; XPS spectroscopy

Magnesia modified H-ZSM-5 as an efficient acidic catalyst for steam reforming of dimethyl ether by Xu Long; Qijian Zhang; Zhao-Tie Liu; Ping Qi; Jian Lu; Zhong-Wen Liu (pp. 381-388).

Display Omitted► H-ZSM-5 modified with MgO was investigated as an acidic catalyst for SRD. ► MgO highly dispersed on H-ZSM-5 deteriorated its stronger acidic sites. ► Sharply decreased selectivity of hydrocarbon byproducts over MgO modified H-ZSM-5. ► Over 90% H₂ yield obtained over H-ZSM-5 modified with optimal amount of MgO.To develop an efficient acidic catalyst for steam reforming of dimethyl ether (DME), H-ZSM-5 was modified with a series amount of MgO (0–8.16wt.%) via the incipient impregnation method by using Mg(NO₃)₂ as a precursor. Irrespective of the MgO loadings studied, it was highly dispersed over H-ZSM-5, and very limited impact on the structure and crystallinity of the zeolite was unambiguously revealed by the techniques of XRD, FT-IR, and N₂ adsorption at low temperatures. On the contrary, significant effects of MgO on the acidity of H-ZSM-5, especially the stronger acidic sites, were clearly manifested from the temperature-programmed desorption of ammonia (NH₃-TPD). The amount of the stronger acidic sites was sharply decreased after loading 0.61wt.% MgO on H-ZSM-5, and it was continuously decreased when the MgO loading was further increased until 8.16wt.%. In contrast, the maximum amount of weaker acidic sites was observed between 1.41 and 2.92wt.% MgO loaded samples. The MgO-modified H-ZSM-5 physically mixed with a commercial Cu/ZnO/Al₂O₃ was investigated as a bifunctional catalyst for steam reforming of DME (SRD). The reaction was performed in a fixed-bed reactor under the conditions of T=290°C, P=1atm, and GHSV=4000h⁻¹. SRD results indicate that the DME conversion, H₂ yield, and selectivity of the carbon-containing products were strongly dependent on the MgO loadings over H-ZSM-5, and the highest H₂ yield of about 93% was achieved over the bifunctional catalyst by using 1.98wt.% MgO modified H-ZSM-5 as a solid acid. Together with the reaction and characterization results of the Mg²⁺-exchanged H-ZSM-5, the property of the stronger acidic sites over the MgO-modified H-ZSM-5 was revealed to be a crucial factor in determining the SRD performance of the bifunctional catalyst. The simple impregnation procedure and the high efficiency in versatile tailoring the acidity make MgO-modified H-ZSM-5 a practical, highly efficient, and promising solid acid for hydrogen production via SRD.

Keywords: Hydrogen production; Steam reforming; Dimethyl ether; Magnesia; ZSM-5

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Applied Catalysis B, Environmental (v.134-135, #)