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Applied Catalysis A, General (v.425-426, #)

Editorial Board (pp. co2).

Contents (pp. iii-ix).

Activity and surface properties of NiMo/SiO₂–Al₂O₃ catalysts for hydroprocessing of heavy oils by Carolina Leyva; Jorge Ancheyta; Arnaud Travert; Françoise Maugé; Laurence Mariey; Jorge Ramírez; Mohan S. Rana (pp. 1-12).

Display Omitted► NiMo/SiO₂–Al₂O₃ catalysts synthesized and characterized by several techniques. ► Catalysts tested at different reaction scales including heavy oil hydrotreating. ► Sulfur removal corresponds to the number of active metal sites. ► Metal removal is affected by dispersion of sulfide phase, porosity and acidity. ► For removal of asphaltenes both acidity and textural properties are important.NiMo/SiO₂–Al₂O₃ mixed oxide supported catalysts were investigated for hydroprocessing of heavy crude oil at moderate reaction conditions. Hydrodesulfurization (HDS), hydrodemetalization (HDM), hydrodeasphaltenization (HDAs) and hydrodenitrogenation (HDN) reactions were studied as function of time-on-stream (TOS). The results indicated that HDS of crude oil corresponds to the number of active metal sites (sulfide phases) present in the catalyst, HDN is enhanced when the catalyst presents a combination of well dispersed sulfide phases and weak to moderate acidity. HDM presented a complex behavior indicating that it is affected significantly not only by the dispersion of the sulfide phase but also by the porosity and acidity of the catalyst. As expected, for HDAs both acidity and textural properties are important. The stability of the catalyst with time-on-stream was affected by coke and metals deposition. The supports and fresh catalysts were characterized by nitrogen physisorption, SEM-EDX, and FT-IR of CO and pyridine adsorption. The results confirm that NiMo/SiO₂–Al₂O₃ catalysts are a good option for the hydrotreatment of heavy oils and that the method used here for support preparation can tune the formation of meso- or macro-porosity and the type and strength of the catalyst acid sites.

Keywords: NiMo/SiO; ₂; –Al; ₂; O; ₃; catalysts; FT-IR; CO adsorption; Hydrotreating; Heavy oil

Dynamic modeling and simulation of hydrotreating of gas oil obtained from heavy crude oil by Fabián S. Mederos; Jorge Ancheyta; Ignacio Elizalde (pp. 13-27).

.Display Omitted► A dynamic heterogeneous one-dimensional reactor model was developed. ► Main reactions occurring in the hydrotreating process are considered. ► Kinetics was extracted from bench-scale unit experimental data. ► Heavy oil-derived gas oil and commercial CoMo catalyst were used for hydrotreating. ► Simulation results showed good agreement with experimental data.This paper describes a dynamic heterogeneous one-dimensional model of trickle-bed reactor used for catalytic hydrotreating of oil fractions. The model takes into consideration the main reactions occurring in the hydrotreating process: hydrodesulfurization, hydrodenitrogenation, hydrodearomatization (mono-, di-, and polyaroamatics), olefins hydrogenation, and mild hydrocracking (gas oil, naphtha, and gases). Kinetic parameters were determined from experimental data obtained in an isothermal bench-scale reactor during hydrotreating of atmospheric gas oil coming from a heavy crude oil over a commercial CoMo catalyst. The developed model was used to predict the dynamic behavior of an industrial hydrotreating reactor within a wide range of reaction conditions. Changes in concentration, partial pressure, and temperature profiles are simulated and discussed as a function of reactor axial position and time. The simulation results obtained with the proposed dynamic model showed good agreement with experimental data.

Keywords: Dynamic modeling; Catalytic hydrotreating; Trickle-bed reactor

Recyclable copper catalysts based on ionic-tagged C₂-symmetric Indabox ligands and their application in asymmetric Henry reactions by Zhi-Huai Li; Zhi-Ming Zhou; Xiao-Yan Hao; Jun Zhang; Xiao Dong; Ying-Qiang Liu; Wen-Wen Sun; Dan Cao (pp. 28-34).

Display Omitted► Novel imidazolium/pyrrolidinium-tagged Indabox ligands were prepared successfully. ► New ligands were applied in copper-catalyzed asymmetric Henry reaction. ► The product could be attained at 94% ee value. ► Catalyst could be recycled 12 times, which makes it a green chemical process.New imidazolium/pyrrolidinium-tagged Indabox ligands were designed and prepared. Catalysts based on these ligands with Cu(OAc)₂·H₂O were applied to the asymmetric Henry reaction using various aldehydes and CH₃NO₂, the products were obtained in high enantioselectivity. Specifically, ( R)-1-(2-methoxylphenyl)-2-nitroethanol was obtained in 94% ee in MeOH. Furthermore, the catalyst based on7 could be recycled at least 12 times by simple wash without an obvious loss of activity or enantioselectivity. This catalytic procedure demonstrated the potential for catalyst recyclability in the asymmetric Henry reaction. Additionally, a theoretical mechanistic study was conducted to explain the origin of the enantioselectivity.

Keywords: Catalyst recycled; Imidazolium/pyrrolidinium-tagged Indabox; Asymmetric Henry reaction; Theoretical mechanistic study

Gold(III) chloride (HAuCl₄·3H₂O) in PEG: A new and efficient catalytic system for the synthesis of functionalized spirochromenes by Mazaahir Kidwai; Anwar Jahan; Neeraj Kumar Mishra (pp. 35-43).

Display Omitted► Eco-friendly method for the synthesis of functionalized spirochromenes. ► Gold(III) chloride (HAuCl₄·3H₂O) is used as soft carbophilic Lewis acid catalyst. ► Recyclability of polyethylene glycol (PEG). ► Multicomponent reaction. ► This protocol is green and advantageous with high yields and less reaction time.Gold(III) chloride (HAuCl₄·3H₂O) in PEG 400 was found to be an efficient catalytic system for the synthesis of biologically important functionalized spirochromene derivatives via one-pot three-component reaction of isatins/acenaphthoquinone, active methylene compounds and cyclic 1,3-diketones/4-hydroxycoumarin. A new catalytic system, recyclability of reaction medium, little reaction times and excellent yields with easy workup render this protocol more attractive and economically viable.

Keywords: Multicomponent reaction (MCR); Isatins or Acenaphthoquinone; Active methylene compounds; Cyclic 1,3-diketones; Gold(III) chloride (HAuCl; ₄; ·3H; ₂; O); Polyethylene glycol (PEG); Spirochromenes

Metal–organic framework MOF-199 as an efficient heterogeneous catalyst for the aza-Michael reaction by Lien T.L. Nguyen; Tung T. Nguyen; Khoa D. Nguyen; Nam T.S. Phan (pp. 44-52).

Display Omitted► MOF-199 was synthesized and characterized. ► MOF-199 was used as catalyst for the aza-Michael reaction. ► High conversions were achieved using catalytic amounts of the MOF-199. ► The catalyst could be reused.A highly porous metal–organic framework (MOF-199) was synthesized from the reaction of copper nitrate trihydrate and 1,3,5-benzenetricarboxylic acid by solvothermal method, and used as a recyclable acid catalyst for the aza-Michael reaction. Physical characterizations of the solid catalyst were achieved by using a variety of different techniques, including X-ray powder diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), Fourier transform infrared (FT-IR), dynamic laser light scattering (DLS), atomic absorption spectrophotometry (AAS), and nitrogen physisorption measurements. Excellent conversions were achieved under mild conditions in the presence of 5mol% catalyst. The MOF-199 catalyst could be reused several times without a significant degradation in catalytic activity. No contribution from homogeneous catalysis of active species leaching into the liquid phase was detected.

Keywords: Metal–organic framework; MOF-199; aza-Michael reaction; Heterogeneous catalyst; Recyclable

Mn–Na₂WO₄/SiO₂ as catalyst for the oxidative coupling of methane. What is really known? by S. Arndt; T. Otremba; U. Simon; M. Yildiz; H. Schubert; R. Schomäcker (pp. 53-61).

Display Omitted► Knowledge on the Mn–Na₂WO₄/SiO₂ was summarized and critically reviewed. ► Stability of the catalyst is proven, which is important because many catalysts deactivate. ► Variations of the content were studied, but, variations of the support are missing in literature.Mn–Na₂WO₄/SiO₂ is one of the very few catalysts for the oxidative coupling of methane, whose stability over extended times on stream has been reported by different research groups. The high stability turned Mn–Na₂WO₄/SiO₂ into an object of research, despite the rather complex composition and structure. The nature of the active site or the active phase is unclear, in spite of the research on this catalytic system. This manuscript tries to critically summarize the literature on this system and to discuss the available information about the relationship of structure and activity.

Keywords: Abbreviations; C; ₂; ethane; +; ethylene; C; ₂₊; ethane; +; ethylene; +; higher hydrocarbons; DFT; Density Functional Theory; EDX; Energy Dispersive X-Ray Spectroscopy; EPR; Electron Paramagnetic Resonance; GHSV; gas hourly space velocity; IR; infrared; OCM; oxidative coupling of methane; TPD; Temperature Programmed Desorption; XAFS; X-ray absorption fine structure; XRD; X-Ray Diffraction; XPS; X-Ray Photoelectron SpectroscopyOCM; Oxidative coupling of methane; Mn–Na; ₂; WO; ₄; /SiO; ₂; Manganese sodium tungstate; Sodium tungstate; Review

Effect of hydrogen spillover in decalin dehydrogenation over supported Pt catalysts by Nanzhe Jiang; K.S. Rama Rao; Myung-Jong Jin; Sang-Eon Park (pp. 62-67).

Display Omitted► Decalin dehydrogenation over Pt supported catalyst. ► Superior activity of “Pt/C” over “Pt/Al₂O₃” catalyst due to hydrogen spillover. ► Phase transformation of alumina boehmite phase of alumina to γ or δ phase.One weight percent Pt impregnated on activated carbon (Pt/AC) and alumina supports (Pt/Al₂O₃) have been tested for decalin dehydrogenation for the production of clean H₂. CO pulse chemisorption results indicate nearly same Pt dispersion in both Pt/AC and Pt/Al₂O₃ catalysts. The comparison of activity between Pt/AC and Pt/Al₂O₃ catalysts revealed superior decalin dehydrogenation activity over Pt/AC both in terms of turn over frequency as well as the yield towards H₂ production which is due to the spill over of H₂ on Pt/AC. The Pt dispersion in Pt/Al₂O₃ is lost due to the phase transformation of support (boehmite phase of alumina to γ phase) during reduction treatment and this is the main reason for the loss of decalin dehydrogenation activity. It is concluded that spill over hydrogen is also an important aspect in addition to Pt dispersion for getting higher H₂ yield from decalin dehydrogenation.

Keywords: Decalin dehydrogenation; Pt/AC; Pt/Al; ₂; O; ₃; CO pulse chemisorption; Spill over H; ₂

Ni–Co–Cu supported on pseudoboehmite-derived Al₂O₃: Highly efficient catalysts for the hydrogenation of organic functional groups by Tianbao Shi; Hui Li; Lianghong Yao; Weijie Ji; Chak-Tong Au (pp. 68-73).

Display Omitted► Ternary Ni–Cu–Co catalysts of low Ni loading supported by Al₂O₃ were developed. ► Catalyst is versatile yet efficient for hydrogenation ofCN,NO₂, andCC groups. ► Complete conversion and high selectivity were observed under mild conditions. ► Reduction of Ni²⁺ and dispersion of Ni⁰ are enhanced due to Cu and Co addition. ► Superior catalytic performance can be attributed to Ni–Cu–Co synergetic interaction.Ni–Co–Cu catalysts supported on pseudoboehmite-derived Al₂O₃ were developed for efficient hydrogenation of organic functional groups: CN and NO₂ associated with benzene as well asCC in butynediol. Factors such as thermo-treatment of pseudoboehmite, Ni loading, Cu and Co content, and catalyst operating parameters were systematically studied. Among the catalysts, 20%Ni–3%Cu–5%Co/Al₂O₃ performed the best, showing 100% feed conversion and 84–99.8% selectivity of target products. Techniques such as N₂ sorption measurement, scanning electron microscope, hydrogen temperature-programmed reduction and desorption, X-ray photoelectron spectroscopy, and in situ X-ray diffraction were used to characterize the catalysts. The superior performance of the catalyst can be attributed to synergetic interaction among the Ni–Cu–Co constitutes as well as enhancement of Ni²⁺ reduction and Ni⁰ dispersion that are resulted due to the co-presence of Cu and Co.

Keywords: Hydrogenation; Nitro, nitrile and alkynyl groups; Dispersed Ni–Cu–Co catalyst

Novel photocatalyst, Bi₂Sn₂O₇, for photooxidation of As(III) under visible-light irradiation by Qinfen Tian; Jiandong Zhuang; Jixin Wang; liyan Xie; Ping Liu (pp. 74-78).

Display Omitted► Bi₂Sn₂O₇ is a promising photocatalyst for As(III) oxidation under visible-light. ► O₂⁻ and h⁺ are recognized to be the main active species in As(III) oxidization. ► A band-gap model is proposed to explain the generation mechanism of active species.Nanocrystalline Bi₂Sn₂O₇, a visible-light photocatalyst synthesized via a facile hydrothermal route, is used to remove arsenite from aqueous solution for the first time. The as-synthesized Bi₂Sn₂O₇ product is characterized by X-ray diffraction, N₂ sorption–desorption, UV–vis diffuse reflectance spectroscopy, transmission electron microscopy, electron spin resonance, X-ray photoelectron spectra, and electrochemistry technology. The results reveal that the sample has an average particle size of approximately 10nm, a specific surface area of 51.3m²/g, and a band gap of 2.88eV. Moreover, the Bi₂Sn₂O₇ nanoparticles exhibit a high photocatalytic activity in the oxidation of As(III) (up to 96.8%) under visible-light irradiation.O₂⁻ and h⁺ are recognized as the primary active species responsible for As(III) oxidation. Meanwhile, a possible mechanism for the photo-oxidation of As(III) over Bi₂Sn₂O₇ is also proposed.

Keywords: Bi; ₂; Sn; ₂; O; ₇; Visible-light photocatalyst; As(III) removal; Hydrothermal process

A new solid acid for specifically cleaving the C_arC_alk bond in di(1-naphthyl)methane by Xiao-Ming Yue; Xian-Yong Wei; Bing Sun; Ying-Hua Wang; Zhi-Min Zong; Xing Fan; Zi-Wu Liu (pp. 79-84).

Display Omitted► A new solid acid by impregnating two active acids into activated carbon is first prepared. ► Strong interactions exist among the two acids and activated carbon. ► Di(1-naphthyl)methane is hydrocracked specifically without any hydrogenation products. ► The addition of H⁺ to ipso-position of di(1-naphthyl)methane could be crucial step.Three catalysts were prepared by impregnating the same volume of pentachloroantimony (PCA), trimethylsilyl trifluoromethanesulfonate (TMSTFMS), or isometric PCA and TMSTFMA into an activated carbon (AC). Di(1-naphthyl)methane (DNM) was used as a coal-related model compound to evaluate their catalytic activity. The results show that C_arC_alk bond in DNM can be specifically cleaved over each catalyst to afford naphthalene and 1-methylnaphthalene under pressurized hydrogen at temperatures up to 300°C, but as a new solid acid (NSA), PCA–TMSTFMS/AC is significantly more active for DNM hydrocracking than the other two catalysts. FTIR and SEM analyses reveal the strong interactions among PCA, TMSTFMS, and the AC in the NSA. NH₃-TPD analysis suggests that the NSA should exhibit appreciably stronger acidity than the other two catalysts. The strong interactions may result in the appreciably stronger acidity of the NSA than that of the other two catalysts and thereby facilitate DNM hydrocracking. It is presumed that H₂ was heterolytically cleaved to immobile H⁻ and mobile H⁺. The addition of mobile H⁺ to ipso-position of DNM should be crucial step for DNM hydrocracking.

Keywords: Coal liquefaction; Di(1-naphthyl)methane; Hydrocracking; Specific cleavage

Metal oxide-catalyzed ammoxidation of alcohols to nitriles and promotion effect of gold nanoparticles for one-pot amide synthesis by Tamao Ishida; Hiroto Watanabe; Takashi Takei; Akiyuki Hamasaki; Makoto Tokunaga; Masatake Haruta (pp. 85-90).

Display Omitted► Manganese dioxide is an excellent catalyst for the ammoxidation of alcohols to produce nitriles. ► Gold deposited on MnO₂ promoted the hydration of a nitrile leading to a one-pot amide synthesis from an alcohol. ► Gold on Al₂O₃ and CeO₂ catalyzed the ammoxidation of benzyl alcohol.Transition metal oxides (MnO₂, Co₃O₄, and NiO) are catalytically active for the ammoxidation of alcohols to nitriles. In particular, MnO₂ exhibited remarkably high catalytic activity and selectivity for the ammoxidation of alcohols to produce nitriles. Benzyl alcohol could also be directly converted to benzonitrile by MnO₂ catalyst by the one-pot ammoxidation and the hydration with water which was formed by the first ammoxidation step. The deposition of gold nanoparticles (Au NPs) onto MnO₂ did not enhance the ammoxidation of benzyl alcohol but promoted the hydration of benzonitrile to produce benzamide with high selectivity. In contrast, Au NPs supported on Al₂O₃, CuO, and CeO₂ catalyzed the ammoxidation of benzyl alcohol, whereas these metal oxides themselves were inactive for the ammoxidation or showed low catalytic activity. These results have demonstrated that gold is intrinsically active as a catalyst for the ammoxidation of alcohols.

Keywords: Metal oxides; Gold nanoparticles; Ammoxidation; Nitrile hydration; Alcohol

A highly efficient, green and recoverable catalytic system for the epoxidation of fatty esters and biodiesel with H₂O₂ by Miriam De Torres; Isabel W.C.E. Arends; José A. Mayoral; Elisabet Pires; Gonzalo Jiménez-Osés (pp. 91-96).

Display Omitted► Fluoroalcohols strongly accelerate the epoxidation reaction of fatty esters with H₂O₂. ► Diselenides are very efficient catalysts for the epoxidation of fatty esters with H₂O₂. ► Quantitative yields and complete stereoselectivity are obtained under mild conditions. ► Se catalyst can be recovered and reused after extracting the products with isooctane. ► Removal of water from the catalytic phase allows reusing it up to seven times.A highly efficient and green strategy for the epoxidation of fatty esters, combining a green oxidant (aqueous hydrogen peroxide) and a recyclable catalyst (a seleninic acid derivative) is presented. The possibility of integrating renewable solvents derived from glycerol in the productive cycle of biodiesel commodities is also explored. Fluorinated solvents (both commercial and glycerol-derived) play a double key role on this methodology: on the one hand, they strongly accelerate epoxidation reaction with respect to common non-fluorinated solvents and, on the other hand, some of them allow catalyst recycling. Mono- and polyunsaturated fatty esters, as well as soy biodiesel have been epoxidized with excellent yields and selectivities towards epoxide under the optimal conditions and with minimum catalyst loads.

Keywords: Epoxidation; Biodiesel; Hydrogen peroxide; Selenium; Fluoroalcohols

Ring opening of decalin via hydrogenolysis on Ir/- and Pt/silica catalysts by Andreas Haas; Sandra Rabl; Marco Ferrari; Vincenzo Calemma; Jens Weitkamp (pp. 97-109).

Display Omitted► Decalin was converted on Ir/silica or Pt/silica at a hydrogen pressure of 5.2MPa. ► On iridium, the six-membered rings are opened without prior isomerization. ► A mechanistic network for the hydroconversion of decalin on iridium is presented. ► The distribution of the hydrocracked products formed on iridium is simulated. ► Pt is less active than Ir, it catalyzes skeletal isomerization and hydrogenolysis.The catalytic conversion of cis-decalin was studied at a hydrogen pressure of 5.2MPa and temperatures of 250–410°C on iridium and platinum supported on non-acidic silica. The absence of catalytically active Brønsted acid sites was indicated by both FT-IR spectroscopy with pyridine as a probe and the selectivities in a catalytic test reaction, viz. the hydroconversion of n-octane. On iridium/silica, decalin hydroconversion starts at ca. 250–300°C, and no skeletal isomerization occurs. The first step is rather hydrogenolytic opening of one six-membered ring to form the direct ring-opening products butylcyclohexane, 1-methyl-2-propylcyclohexane and 1,2-diethylcyclohexane. These show a consecutive hydrogenolysis, either of an endocyclic carboncarbon bond into open-chain decanes or of an exocyclic carboncarbon bond resulting primarily in methane and C₉ naphthenes. The latter can undergo a further endocyclic hydrogenolysis leading to open-chain nonanes. All individual C₁₀ and C₉ hydrocarbons predicted by this “direct ring-opening mechanism” were identified in the products generated on the iridium/silica catalysts. The carbon-number distributions of the hydrocracked productsC9− show a peculiar shape resembling a hammock and could be readily predicted by simulation of the direct ring-opening mechanism. Platinum on silica was found to require temperatures around 350–400°C at which relatively large amounts of tetralin and naphthalene are formed. The most abundant primary products on Pt/silica are spiro[4.5]decane and butylcyclohexane which can be readily accounted for by the well known platinum-induced mechanisms described in the literature for smaller model hydrocarbons, namely the bond-shift isomerization mechanism and hydrogenolysis of a secondary-tertiary carboncarbon bond in decalin.

Keywords: Ring opening; Decalin; Iridium; Platinum; Hydrogenolysis

Catalytic hydrogenation of xylose to xylitol using ruthenium catalyst on NiO modified TiO₂ support by Mithilesh Yadav; Dinesh Kumar Mishra; Jin-Soo Hwang (pp. 110-116).

Display Omitted► The modification of titania (TiO₂) support with nickel chloride used as precursor. ► The catalyst of Ru on (NiO–TiO₂) support is prepared by simple impregnation method. ► Liquid phase hydrogenation of xylose to xylitol over the catalyst Ru/(NiO–TiO₂). ► A catalyst Ru/(NiO–TiO₂) shows high conversion, yield and selectivity to xylitol. ► Comparative study towards xylose hydrogenation with Raney Ni, Ru/C and Ru/TiO₂.The activity of Ru catalyst on a new class of NiO modified TiO₂ support, Ru/(NiO–TiO₂), was studied in the liquid phase catalytic hydrogenation of xylose to xylitol. The TiO₂ support was modified by simple impregnation method using nickel chloride precursor and subsequent oxidation. Various catalysts with different targeted compositions of Ru (1.0 and 5.0wt%) and NiO (1.0, 5.0 and 10wt%) in NiO–TiO₂ were prepared. These catalysts were characterized by using energy dispersive X-ray analysis (EDX/EDS), temperature-programmed reduction (TPR), inductively coupled plasma (ICP) mass spectrometry, transmission electron microscopy (TEM), X-ray powder diffraction (XRD) and CO chemisorption. The novel catalysts are evaluated for selective hydrogenation of xylose and the results compared with those obtained from conventional Raney Ni, Ru/C and Ru/TiO₂ catalysts carried out under identical reaction conditions. The effect of NiO additive in the catalyst Ru/(NiO–TiO₂), clearly found to enhance the conversion, yield and selectivity to xylitol. Furthermore, the order of catalytic activity may be given as Ru (1.0%)/NiO (5.0%)–TiO₂>Ru (1.0%)/TiO₂>Ru (1.0%)/C> Raney Ni. The effects of Ru and NiO loading, xylose concentration (2.5, 15 and 30wt%) and temperature (100, 120 and 140°C) were studied. Although at higher temp 140°C, the conversion of xylose was increased to optimum level, xylose to xylitol selectivity decreased due to formation of by-products.

Keywords: Hydrogenation; Xylose; Xylitol; Ruthenium; NiO modified TiO; ₂; support

Controlling the synergistic effect of oxygen vacancies and N dopants to enhance photocatalytic activity of N-doped TiO₂ by H₂ reduction by Zizhong Zhang; Jinlin Long; Xiuqiang Xie; Huaqiang Zhuang; Yangen Zhou; Huan Lin; Rusheng Yuan; Wenxin Dai; Zhengxin Ding; Xuxu Wang; Xianzhi Fu (pp. 117-124).

Display Omitted► The photocatalytic activity of N-doped TiO₂ is greatly improved by simple H₂ reduction. ► H₂ reduction creates oxygen vacancies and Ti³⁺ ions but without removal of N dopants. ► The formed Ti³⁺ ions largely suppress the photocatalytic activity. ► A synergistic effect of N dopant and oxygen vacancy explains the enhanced activity.This paper focuses on improving photocatalytic activity of N-doped TiO₂ photocatalyst for efficiently utilizing solar energy. A simple H₂ reduction is found to remarkably enhance the photocatalytic activity of N-doped TiO₂ for ethylene oxidation under visible light or simulated solar light irradiation. Ultraviolet/visible diffuse reflectance spectra (UV/vis DRS), X-ray photoelectron spectra (XPS) and electron paramagnetic resonance (EPR) spectra were employed to characterize the surface properties and chemical states of nitrogen dopants in H₂-reduced N-doped TiO₂. The results reveal that H₂ reduction facilitates the creation of oxygen vacancies and Ti³⁺ species in N-doped TiO₂ but without removal of nitrogen species from catalyst surface. The formed oxygen vacancies and Ti³⁺ species seriously influence electron excitation from doped nitrogen species and subsequently tune the generation of active oxygen species O₂⁻ radicals on N-doped TiO₂. The synergistic effect of oxygen vacancies and doped nitrogen species contributes to the enhancement of photocatalytic activity of N-doped TiO₂ samples, but the formed Ti³⁺ ions largely suppress the photocatalytic activity.

Keywords: N-doped TiO; ₂; H; ₂; reduction; Oxygen vacancies; Synergistic effect; Ethylene photooxidation

Sulfated tungstate: An efficient catalyst for synthesis of thioamides via Kindler reaction by Sagar P. Pathare; Pramod S. Chaudhari; Krishnacharya G. Akamanchi (pp. 125-129).

Display Omitted► Sulfated tungstate is mildly acidic, stable, eco-friendly heterogeneous catalyst. ► The catalyst is easy to prepare and well characterized. ► Efficient for synthesis of thioamides via Kindler reaction. ► Protocol is suitable for synthesis of primary, secondary and tertiary thioamides. ► The catalyst can be easily recovered and recycled several times.New application of sulfated tungstate, a mildly acidic solid inorganic acid, as reusable heterogeneous catalyst for efficient Kindler reaction, a three component reactions of aldehydes, amines and sulfur, for synthesis of thioamides is discussed.

Keywords: Kindler reaction; Thioamides; Sulfated tungstate; Heterogeneous catalysis; Amines; Aldehydes; Sulfur

A Single-Event MicroKinetic model for “ethylbenzene dealkylation/xylene isomerization” on Pt/H-ZSM-5 zeolite catalyst by K. Toch; J.W. Thybaut; B.D. Vandegehuchte; C.S.L. Narasimhan; L. Domokos; G.B. Marin (pp. 130-144).

Display Omitted► C₈ aromatics conversion is adequately modeled using single-event microkinetics. ► Combined entropic and energetic effects determine the product distribution. ► ZSM-5 exhibits optimal isomerization versus transalkylation behavior.The Single-Event Microkinetic (SEMK) methodology has been applied towards “ethylbenzene dealkylation/xylene isomerization” under industrially relevant conditions. This includes the isomerization of xylenes towards thermodynamic equilibrium, the dealkylation of ethylbenzene as well as a limited amount of xylene transalkylation into toluene and trimethylbenzenes. By accounting for symmetry effects through the calculation of the number of single events and defining elementary reaction families rather than applying product lumping, a huge reduction in the number of adjustable parameters can be achieved without the loss of the molecular detail in the reaction network. In the kinetic model, 37 components, 78 intermediates and a total of 327 elementary reaction steps, classified in families such as (de-)protonation, alkyl shift, dealkylation, transalkylation and hydrogenation, are considered. Only reactant protonation enthalpies and the activation energies of the considered reaction families, are estimated by model regression to experimental data acquired on a bifunctional Pt/H-ZSM-5 catalyst, while the remaining parameters are determined from first principles or retrieved from literature information. The experimental data are adequately described with physically significant parameter values. Dealkylation is found to be energetically most demanding with an activation energy amounting to 198kJmol⁻¹, while alkyl shift and transalkylation reactions are having the lowest activation energies. Entropic effects result in the lowest rate coefficient for transalkylation, however, and rate coefficients of a similar order of magnitude for alkyl shift and dealkylation. The investigated catalyst is shown to have an adequate acid strength for establishing the thermodynamic equilibrium between the xylene isomers.

Keywords: Xylene isomerization; Ethylbenzene dealkylation; Single-Event Microkinetic modeling; Catalyst optimization; Rational design

Characterization of (Sn and Cu)/Pd catalysts for the nitrate reduction in natural water by Cristina Franch; Enrique Rodríguez-Castellón; Álvaro Reyes-Carmona; Antonio E. Palomares (pp. 145-152).

Display Omitted► Pd/Sn catalysts supported on alumina are characterized by XPS and other techniques. ► The Pd/Sn surface atomic ratio change upon catalyst activation and after reaction. ► The most active catalyst is 0.5% Sn–1% Pd supported on high surface area Al₂O₃. ► Deactivation is due to irreversible Sn–Pd oxidations or to competitive adsorptions.The aim of this work is to characterize different (Cu and Sn)/Pd catalysts, supported on alumina, used for the catalytic removal of nitrates in natural water. The catalysts have been prepared with a Pd/(Cu or Sn) ratio of 2 but with different metal contents. Their activity and selectivity have been studied using a continuous stirred-tank reactor with nitrate polluted water from an aquifer. The catalysts have been characterized both before and after reaction by XPS, XRD, XRF, adsorption–desorption N₂ isotherms at 196°C and TEM. XPS results show changes of the Pd/Sn surface atomic ratio upon catalyst activation and after reaction and the coexistence of different oxidation states for the active metals. The studied catalysts are active, being the catalyst with the best performance that with the highest metallic dispersion and with the lowest phases segregation. The characterization of the catalysts after reaction shows that catalyst deactivation could be related with the non-reversible oxidation of the Sn–Pd couple.

Keywords: Nitrate catalytic reduction; Natural water; Continuous process; Sn–Pd; Cu–Pd, XPS

Three-dimensionally ordered macroporous SrFeO3−_δ with high surface area: Active catalysts for the complete oxidation of toluene by Kemeng Ji; Hongxing Dai; Jiguang Deng; Lei Zhang; Fang Wang; Haiyan Jiang; Chak Tong Au (pp. 153-160).

Display Omitted► 3DOM SrFeO3−_δ with high surface areas are prepared by the PMMA-templating method. ► Surfactant addition results in increase of 3DOM SrFeO3−_δ surface area. ► 3DOM SrFeO3−_δ are high in surface area and O_ads content and good in reducibility. ► 3DOM SrFeO3−_δ catalysts perform well in the combustion of toluene. ► Surface area, O_ads content, and reducibility account for the good catalytic activity.Three-dimensionally ordered macroporous (3DOM) cubic perovskite-type oxides SrFeO3−_δ were prepared using the citrate acid-assisted poly(methyl methacrylate)-templating method in the presence of ethylene glycol, sucrose orl-lysine (denoted as SFO-0, SFO-Sucrose, and SFO-Lysine, respectively). It is found that the SrFeO3−_δ samples possessed a 3DOM architecture and were high in surface area (34–61m²/g). The porous SrFeO3−_δ catalysts performed well in toluene combustion, with the SFO-0 sample exhibiting the highest catalytic activity ( T_50%=292°C and T_90%=340°C at 20,000mL/(gh)). The catalytic activity of the samples showed a good relationship with surface area, oxygen adspecies concentration, and low-temperature reducibility, all decrease in the order of SFO-0>SFO-Lysine>SFO-Sucrose≫SFO-bulk. It is deduced that the good catalytic performance of the porous SrFeO3−_δ materials is due to the good low-temperature reducibility, large surface area, and high oxygen adspecies concentration.

Keywords: Colloidal crystal templating preparation method; Three-dimensional ordered macroporous perovskite-type oxide; Oxygen-deficient strontium ferrite; Low-temperature reducibility; Toluene combustion

Preparation of carbon aerogel supported platinum catalysts for the selective hydrogenation of cinnamaldehyde by Bruno F. Machado; Sergio Morales-Torres; Agustín F. Pérez-Cadenas; Francisco J. Maldonado-Hódar; Francisco Carrasco-Marín; Adrián M.T. Silva; José L. Figueiredo; Joaquim L. Faria (pp. 161-169).

Display Omitted► Selective hydrogenation of cinnamaldehyde is investigated using Pt/carbon aerogels. ► Oxidation of CA's introduces surface groups while preserving the original porosity. ► Pt dispersion is strongly influenced by the acidic oxygenated surface groups. ► Selectivity towards COL depends on both mesopores and acidic character of the CA. ► Thermal treatment in N₂ at 973K is found to favor the hydrogenation of the CC bond.The selective hydrogenation of cinnamaldehyde is investigated using platinum catalysts supported on carbon aerogels with different textural and chemical properties. Despite the large amount of oxygenated surface groups introduced after the oxidation step, the original porosity of the carbon aerogels is maintained. The oxidation treatments performed on the materials are found to strongly influence the surface chemistry which in turn affects the Pt dispersion, yielding larger metal particles after the chemical modifications and the H₂ pre-treatment. The presence of mesopores and the increase of the acidic character in the carbon aerogels lead to a higher catalytic activity and selectivity towards cinnamyl alcohol when compared with that obtained for the untreated materials. A thermal treatment at 973K is found to favor the hydrogenation of the olefinic bond when using carbon aerogels, due to the remaining oxygenated surface groups, at variance with other previously reported carbon supports (xerogels and nanotubes).

Keywords: Carbon aerogel; Surface chemistry; Platinum; Selective hydrogenation; Cinnamaldehyde

Kinetic model of K–Ni/ α-Al₂O₃ catalyst for oxidative reforming of methane determined by genetic algorithm by Kohji Omata; Seishiro Kobayashi; Junpei Horiguchi; Yasukazu Kobayashi; Yuichiro Yamazaki; Muneyoshi Yamada (pp. 170-177).

Display Omitted► K–Ni/ α-Al₂O₃ catalyst was used for methane oxidative reforming at 650°C and 1MPa. ► The reaction network was determined by means of genetic algorithm. ► Direct route was predominant for syngas formation with K–Ni/ α-Al₂O₃ catalyst. ► SVM made a regression model between preparation conditions and rate constants. ► α-Al₂O₃ diluent accelerated methane combustion to decrease syngas selectivity.Effects of preparation conditions of a K–Ni/ α-Al₂O₃ catalyst on the activity and selectivity of high-pressure reforming of methane was investigated. Catalyst preparation parameters such as calcination temperature of boehmite, the amount of NiO and the amount of K loading were designed by L₉ orthogonal array, and the catalysts were prepared by an impregnation method. Each catalyst was used in an activity test where contact time was decreased by increasing the gas feed rate, and conversion was recorded until O₂ conversion was below 30%. Both the conversions and syngas selectivity were used for fitting by Genetic algorithm. The algorithm was applied to determine the kinetic parameters of the reaction network of high-pressure reforming of methane. Then a support vector machine was trained using the nine dataset to correlate the catalyst preparation parameters and the kinetic parameters. After the training, we conducted grid searches to build response surfaces of the kinetic parameters. Thus, the all kinetic rate constants could be predicted as functions of the catalyst preparation conditions. The analysis of the kinetic model suggested that successive oxidation of the syngas was the most influential factor for low syngas selectivity. Whereas the amount of NiO loading influences on hydrogen oxidation, CO oxidation was not accelerated by NiO. High syngas selectivity was attained by using a less amount of diluent in the catalyst bed.

Keywords: Oxidative reforming of methane; NiO–Al; ₂; O; ₃; catalyst; K-promotion; Orthogonal array; Genetic algorithm; Support vector machine

Turning Teflon-coated magnetic stirring bars to catalyst systems with metal nanoparticle trace deposits – A caveat and a chance by Christian Vollmer; Marcel Schröder; Yi Thomann; Ralf Thomann; Christoph Janiak (pp. 178-183).

Display Omitted► Metal nanoparticles can be deposited on a polytetrafluorethylene (PTFE) surface. ► Such a PTFE surface can be a Teflon-coated magnetic stirring bar. ► Trace metal nanoparticle deposits turn a stirring bar into a re-usable catalyst system. ► Traces of Rh-nanoparticles on a stirring bar are active hydrogenation catalysts. ► Stirring bars can turn into re-usable and easily handable catalyst systems.It could be an unintentional effect to deposit metal nanoparticles on a simple Teflon-coated magnetic stirring bar. Rhodium nanoparticles, as an example, were reproducibly deposited onto a standard, commercial Teflon-coated magnetic stirring bar by easy and rapid microwave-assisted decomposition of the metal carbonyl precursor Rh₆(CO)₁₆ in the ionic liquid 1- n-butyl-3-methyl-imidazolium tetrafluoroborate. Such metal nanoparticle deposits are not easy to remove from the Teflon surface by simple washing procedures and present active catalysts which one is not necessarily aware of. Barely visible metal-nanoparticle deposits on a stirring bar can act as trace metal impurities in catalytic reactions. As a proof-of-principle the rhodium-nanoparticle deposits of 32μg or less Rh metal on a 20mm×6mm magnetic stirring bar were shown to catalyze the hydrogenation reaction of neat cyclohexene or benzene to cyclohexane with quantitative conversion. Rhodium-nanoparticle-coated stirring bars were easily handable, separable and re-usable catalyst system for the heterogeneous hydrogenation with quantitative conversion and very high turnover frequencies of up to 32,800mol cyclohexene×(molRh)⁻¹×h⁻¹ under organic-solvent-free conditions.

Keywords: Metal nanoparticles; Rhodium; Teflon surface; Trace metal; Hydrogenation; Stirring bar

Synthesis and characterization of calcium methoxide as heterogeneous catalyst for trimethylolpropane esters conversion reaction by Hassan Masood; Robiah Yunus; Thomas S.Y. Choong; Umer Rashid; Yun H. Taufiq Yap (pp. 184-190).

Possible mechanism for transesterification of POME with TMP catalyzed by calcium methoxide.Display Omitted► Trimethylolpropane esters are promisingly utilized as biolubricant basestock. ► Calcium methoxide was synthesized to use as heterogeneous catalyst for trimethylolpropane esters conversion. ► Calcium methoxide showed effective catalytic properties for transesterification reaction. ► An effective yield of trimethylolpropane triesters was obtained with using calcium methoxide as heterogeneous catalyst.Trimethylolpropane (TMP) esters are potential biodegradable basestock for biolubricant. In order to attain environmental benignity, attention has been focused on utilizing heterogeneous catalysts for production of TMP esters. Alkaline homogeneous catalysts tend to react with free fatty acids to produce unwanted soap, thus reducing the overall product yield. This study had focused on the synthesis of calcium methoxide and investigating its potential as heterogeneous catalyst for the transesterification of TMP and palm oil methyl esters (POME) to TMP esters. The performance of synthesized calcium methoxide as a catalyst was examined by characterizing it through some instrumental techniques. X-ray diffraction (XRD) showed calcium methoxide has been successfully synthesized. Scanning electron microscopy (SEM) displayed thermally resistant surface structure with good porosity; BET showed high surface area; particle size analysis evidenced reasonable size of catalyst particles; and thermogravimetry (TGA) revealed good thermal stability of synthesized calcium methoxide. Moreover, the catalyst was found to possess mesoporous surface by pore size analysis through Barrett–Joyner–Halenda (BJH) method. The results of transesterification reaction indicated satisfactory catalytic activity of synthesized calcium methoxide and the TMP triesters yield obtained was 80.35% after 2h, 87.48% after 4h, 91.30% after 6h and 92.38% after 8h reaction time.

Keywords: Lubricant; Heterogeneous catalyst; Calcium methoxide; Transesterification

A simple and efficient zeolite catalyst for toluene oxidation in aqueous media by Bin Du; Song-Il Kim; Lan-Lan Lou; Aizhong Jia; Gaixia Liu; Ben Qi; Shuangxi Liu (pp. 191-198).

Display Omitted► Alkali-treated zeolites showed good catalytic activity for toluene oxidation. ► Pure water was firstly used as the sole medium for toluene oxidation. ► No heavy metals or their oxides were employed in this catalytic system. ► A probable redox mechanism for toluene oxidation in water media was firstly proposed. ► This heterogeneous catalytic process is environment-friendly.In this work, it was found that alkali-treated zeolites could efficiently catalyze oxidation of toluene with H₂O₂ in aqueous media. No heavy metals or their oxides were employed in the synthesis of catalyst and no additives were used in this catalytic system. Through optimizing the experimental conditions, alkali-treated HZSM-5 exhibited good catalytic activity for toluene oxidation in only 5h at a low temperature (below 100°C): 32.0% conversion of toluene with selective formation of 25.0% benzaldehyde, 20.8% benzyl alcohol and 27.5% benzoic acid. Moreover, the results of reusability studies indicated that alkali-treated HZSM-5 was a durable and green catalyst for toluene oxidation in aqueous media. The changes in acidities and textural features of the zeolites induced by alkali-treatment were characterized by ammonia temperature programmed desorption (NH₃-TPD) and X-ray powder diffraction (XRD), respectively. The results indicated the reactivity for toluene oxidation could be related to the amount of speciesAl andAlOH in this system. A probable redox mechanism for toluene oxidation catalyzed by alkali-treated zeolites in aqueous media was proposed in this work.

Keywords: Aqueous media; Toluene oxidation; Heterogeneous catalysis; Alkali-treatment

Levulinic acid esterification with ethanol to ethyl levulinate production over solid acid catalysts by D.R. Fernandes; A.S. Rocha; E.F. Mai; Claudio J.A. Mota; V. Teixeira da Silva (pp. 199-204).

.Display Omitted► The activity of sulfated oxides for levulinic acid esterification correlates with their acidity. ► Successive sulfations of SnO₂ increase its acidity and activity. ► The pore structure of zeolites plays a role more important than that of the acidity. ► Amberlyst-15 presents a good activity and reusability.Levulinic acid is considered as a versatile building block because it can be used for the synthesis of several organic chemicals. In particular, its esterification with ethanol produces ethyl levulinate that can be used as diesel miscible biofuel (DMB), preventing global warming by decreasing atmospheric CO₂ generated from the consumption of fossil fuels. This article explores the use of two groups of solid acid catalysts (sulfated oxides and zeolites with different pore structures) in the esterification of levulinc acid with ethanol aiming for ethyl levulinate production. It was found that while there is a correlation between the number of acidic sites and activity for the sulfated oxides, the same is not true for the studied zeolites where the pore channels play a more important role. Among the catalysts tested, Amberlyst-15 and sulfated SnO₂ showed a remarkable high yield of ethyl levulinate that was probably due to the strong acidity provided by SO₃H functional groups and SO₄ species, respectively.

Keywords: Levulinic acid; Ethyl levulinate; Esterification; Acid solids; Sulfated stannia; Bio-ethanol

Selective hydrogenation of maleic anhydride to succinic anhydride catalyzed by metallic nickel catalysts by Yonghai Feng; Hengbo Yin; Aili Wang; Tao Xie; Tingshun Jiang (pp. 205-212).

Display Omitted► Maleic anhydride was selectively hydrogenated to succinic anhydride by Ni catalyst. ► Ni nanoparticles had higher catalytic activity than Raney Ni at lower temperature. ► Size and structure of Ni nanoparticles were crucial to the hydrogenation reaction. ► Polar solvent favored the hydrogenation of maleic anhydride to succinic anhydride.Maleic anhydride was selectively hydrogenated to succinic anhydride over metallic nickel catalysts, such as Raney Ni and Ni nanoparticles, in liquid phase at reaction temperature lower than 130°C. When the Raney Ni catalyst in solvents with different polarities catalyzed the hydrogenation of maleic anhydride to succinic anhydride, the solvent with high polarity favored the hydrogenation of maleic anhydride to succinic anhydride as compared to that with low polarity. When the hydrogenation reaction was catalyzed by Raney Ni catalyst at 100°C and H₂ pressure of 2.5MPa for 360min in acetic anhydride, the conversion of maleic anhydride and the selectivity of succinic anhydride were 99.6% and 100%, respectively. In solvent-free reaction system, γ-butyrolactone as a byproduct with the maximum selectivity of 14.8% was produced at 130°C. All of the Ni nanoparticles with average diameters ranging from 8 to 313nm showed higher catalytic activity than Raney Ni in liquid phase hydrogenation of maleic anhydride to succinic anhydride. When the Ni nanoparticles with an average diameter of 8nm were used as the catalysts in the liquid phase hydrogenation at 80°C and 2MPa of H₂ for 150min and the weight ratio of catalyst to maleic anhydride was 1:100, the conversion of maleic anhydride and the selectivity of succinic anhydride were 99.8% and 100%, respectively. The small particle size and the polycrystalline structure of Ni nanoparticles played important roles in the liquid phase selective hydrogenation of maleic anhydride to succinic anhydride.

Keywords: Hydrogenation; Maleic anhydride; Succinic anhydride; Raney Ni; Ni nanoparticles

Effective gold catalyst supported on mesoporous silica decorated by ceria for the synthesis of high value lactobionic acid by Luis-Felipe Gutiérrez; Safia Hamoudi; Khaled Belkacemi (pp. 213-223).

Display Omitted► Rapid and simple synthesis method of very active Au catalyst for the aerobic oxidation of lactose. ► The catalyst presents a regular array of mesopores and well dispersed spherical AuNPs. ► Lactose is almost depleted after 60min of reaction using the 0.7%Au/SBA-15-CeO₂ catalyst. ► The 0.7%Au/SBA-15-CeO₂ is 100% selective towards LBA production.Gold supported on mesoporous SBA-15 and SBA-15-CeO₂ with Ce/Si molar ratios of 0.1, 0.2, 0.4 and 0.6 were synthesized via wet chemical process using a gold cationic complex precursor [Au( en)₂]³⁺ ( en=ethylenediamine), and investigated as catalysts for the partial oxidation of lactose to selectively synthesize lactobionic acid (LBA) for therapeutic, pharmaceutical and food grad applications.These catalysts were characterized by N₂ physisorption, XRD, FT-IR, TEM and XPS. N₂ physisorption and XRD analysis revealed that SBA-15-CeO₂ with the investigated Ce/Si molar ratios support possess ordered hexagonal mesoporous structure, characterized with a high surface area and large pore volume, similar to SBA-15, whereas BET surface area and pore volume of catalyst were significantly decreased upon impregnation. XPS analysis revealed the coexistence of metallic and oxidized gold species (Au⁰, Au⁺ and Au³⁺) in all prepared catalysts and the presence of both Ce³⁺ and Ce⁴⁺ oxidation states for gold supported on mesoporous SBA-15-CeO₂ catalysts.The influence of the pH value on lactose conversion was also investigated. After 60min of reaction, the 0.7%Au/SBA-15-CeO₂ (Ce/Si=0.1 and 0.2) catalysts showed high catalytic activity (100% lactose conversion) and a 100% selectivity towards LBA, when they were used at a catalyst/lactose ratio of 0.2, under alkaline (pH 9.0) and mild reaction temperature (65°C). At the optimized conditions, 0.7% Au/SBA-15-CeO₂ catalysts with Ce/Si of 0.1, 0.2 and 0.4 were more active than 0.7% Au/SBA-15 catalyst. A maximum of activity is reached at Ce/Si of 0.2. The experimental catalytic tests and characterizations show clearly the role of Ce in the enhancement in the catalyst activity was the coordination and agglomeration states of Ce atoms could have an important effect.

Keywords: Gold catalyst; SBA-15; Ceria; Lactose; Oxidation; Lactobionic acid

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Applied Catalysis A, General (v.425-426, #)