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Applied Catalysis A, General (v.390, #1-2)

Contents (pp. iii-xi).

Acknowledgement to Reviewers (pp. i-vii).

Editorial Board (pp. co2).

David Trimm 1937–2010 (pp. xii).

Contents (pp. iii-xi).

Acknowledgement to Reviewers (pp. i-vii).

Editorial Board (pp. co2).

David Trimm 1937–2010 (pp. xii).

Structure and morphology of Pd/Al₂O₃ and Pd/CeO₂/Al₂O₃ combustion catalysts in Pd–PdO transformation hysteresis by Sara Colussi; Alessandro Trovarelli; Erik Vesselli; Alessandro Baraldi; Giovanni Comelli; Gianpiero Groppi; Jordi Llorca (pp. 1-10).

Display Omitted▶ PdO decomposition is a thermodynamically driven process, not depending on support. ▶ The nature of support affects only the dynamics of O₂ release in PdO decomposition. ▶ Pd reoxidation is a kinetically driven process, strongly affected by the support. ▶ CeO₂ and residual PdO act as a catalyst for Pd reoxidation. ▶ PdO decomposition and Pd oxidation involve the formation of an intermediate PdO_x.Catalytic combustion of methane has been studied for many years due to its applications in power generation and emissions clean-up. Among different catalysts, Pd-based materials are the most active for the catalytic combustion of methane. In this work we have investigated the Pd–PdO transformation process on Pd–alumina and Pd–ceria–alumina combustion catalysts by combining different analytical techniques. Both decomposition of PdO and reoxidation of Pd take place via the formation of an intermediate, which has been identified as a surface or interfacial PdO_x on the basis of X-ray Photoelectron Spectroscopy analysis. The results obtained by coupling temperature programmed oxidation with high resolution transmission electron microscopy and X-ray photoelectron spectroscopy indicate that PdO decomposition is a thermodynamically driven process, in which the support affects only the amount of PdO species involved in each decomposition step. On the contrary, Pd reoxidation is a kinetically limited process, which is strongly affected by the environment. In particular, the presence of promoters such as CeO₂ or residual PdO significantly speeds up Pd oxidation, thus reducing the characteristic Pd–PdO hysteresis.

Keywords: Catalytic combustion; Palladium; Ceria; Methane

Solid base catalysis of calcium glyceroxide for a reaction to convert vegetable oil into its methyl esters by Masato Kouzu; Jyu-suke Hidaka; Kanako Wakabayashi; Michito Tsunomori (pp. 11-18).

Display Omitted▶ Solid base catalysis of calcium glyceroxide was investigated by IR spectroscopy. ▶ Calcium glyceroxide was combined with methanol used as a molecular probe at 333K. ▶ The produced calcium alkoxide functioned as the solid base catalyst. ▶ The heterogeneous catalytic reaction did not occurred on calcium glyceroxide.When calcium oxide is employed for transesterification of vegetable oil at reflux of methanol, calcium oxide is turned into calcium glyceroxide by combining with glycerol of the by-product. As well as calcium oxide, calcium glyceroxide seemed to catalyze the vegetable oil transesterification. In the present paper, the solid base catalysis of calcium glyceroxide was investigated by IR spectroscopy using methanol as the molecular probe. The measured spectra indicated that calcium glyceroxide was combined with methanol at the temperature of 333K. Chemical composition of the produced calcium compound was estimated at CH₃O-Ca-O(OH)₂C₃H₅. The IR spectrum of the calcium alkoxide indicated that hydrogen bond was formed among the glyceroxyl OH groups and methanol. Data from the soybean oil transesterification, which was carried out at 298K, elucidated that the calcium alkoxide functioned as the solid base catalyst. At the same reaction temperature, calcium glyceroxide did not interact chemically with methanol, and sent out only the homogeneous catalysis.

Keywords: Key words; Solid base catalyst; Calcium glyceroxide; Calcium methoxide; Transesterification; Biodiesel

Solid base catalysis of calcium glyceroxide for a reaction to convert vegetable oil into its methyl esters by Masato Kouzu; Jyu-suke Hidaka; Kanako Wakabayashi; Michito Tsunomori (pp. 11-18).

Keywords: Key words; Solid base catalyst; Calcium glyceroxide; Calcium methoxide; Transesterification; Biodiesel

Increase of reformate yield by using polyacrylic acid as template in preparation of Pt/Re naphtha reforming catalysts by Changkun Liu; Qing Zhu; Zhihua Wu; Zhenhua Zhou; Gaurang Bhargava; Sukesh Parasher; Michael Rueter; Bing Zhou; Jingguang G. Chen (pp. 19-25).

Display Omitted▶ Use of polyacrylic acid template leads to 1.4–2.4% improvement in reformate yield. ▶ Use of polyacrylic acid results in 1.0–2.0wt% less aromatics production. ▶ Platinum particles with reduced surface atom coordination number are disclosed.The need for naphtha reforming to produce high quality reformate for gasoline blend stocks with increased yield has become more urgent due to dwindling crude oil reserves and stringent air pollution regulations. Reforming catalysts prepared using polyacrylic acid (PAA) as a metal ion template exhibited 1.4–2.4% improvement in reformate yield and 1.0–2.0wt% lower aromatic production compared to commercially available catalysts prepared using traditional metal salt coimpregnation methods, while maintaining a comparably high octane number. The catalyst prepared using the PAA template also showed higher liquid recovery with less coke deposition and longer projected catalyst lifetime. Characterization using infrared spectroscopy following the adsorption of CO revealed that catalysts made using the PAA method contained platinum particle surfaces with reduced atom coordination numbers.

Keywords: Nanoparticle; Template; Heterogeneous catalyst; Surface structure; Pt–Re; Naphtha reforming

One-pot synthesized mesoporous Ca/SBA-15 solid base for transesterification of sunflower oil with methanol by Hui Sun; Junxing Han; Yuqi Ding; Wang Li; Jinzhao Duan; Ping Chen; Hui Lou; Xiaoming Zheng (pp. 26-34).

Display Omitted▶ A series of Ca/SBA-15 samples with Ca/Si molar ratio of 0.1, 0.2, 0.3, 0.4 and 0.5 were prepared by using a one-pot synthesis method and used in the transesterification of sunflower oil with methanol. The mesoporous structure of SBA-15 was well preserved with Ca/Si ratio up to 0.5. ▶ Compared with 0.3Ca/SBA-15-IM sample, the Ca/SBA-15 not only showed a better calcium species distribution, but also showed higher BET surface area and larger medium basic sites. ▶ A biodiesel yield of as high as 99.1% was achieved on the 0.5Ca/SBA-15 catalyst at a reaction temperature of 200°C for 8h. At the meantime, no deactivation was found on Ca/SBA-15 sample prepared by one-pot synthesis method in the transesterification reaction, which showed a much better stability than that of prepared by conventional impregnation method. ▶ A water content of up to 5% and/or free fatty acids (FFAs) of 3% did not affect the catalytic activity of Ca/SBA-15 catalyst in the transesterification reaction.A series of Ca/SBA-15 samples with Ca/Si atomic ratios of 0.1, 0.2, 0.3, 0.4 and 0.5 were prepared by using a one-pot synthesis method. They were used in the transesterification of sunflower oil with methanol. For comparison, 0.3Ca/SBA-15 was also synthesized by an incipient impregnation method (0.3Ca/SBA-15-IM). Small-angle XRD, N₂ adsorption, TEM, SEM, TG-DTA, FTIR, CO₂-TPD techniques were used to determine the textual structure and physicochemical properties of Ca/SBA-15 samples. The mesoporous structure of SBA-15 was well preserved with Ca/Si ratios up to 0.5. Compared with 0.3Ca/SBA-15-IM sample, the Ca/SBA-15 showed not only a better calcium species distribution, but also higher BET surface area and larger medium basic sites. A biodiesel yield of as high as 99.1% was achieved on the 0.5Ca/SBA-15 catalyst at a reaction temperature of 200°C for 8h. In the meantime, no deactivation was found after five cycles on Ca/SBA-15 sample prepared by one-pot synthesis method in the transesterification reaction, which showed a much better stability than that of prepared by conventional impregnation method. Besides, a water content of up to 5% and/or free fatty acids (FFAs) content of 3% did not affect the catalytic activity of Ca/SBA-15 catalyst in the transesterification reaction.

Keywords: Ca/SBA-15; CaO; Solid base; Transesterification; Biodiesel

Methanation of CO, CO₂ and selective methanation of CO, in mixtures of CO and CO₂, over ruthenium carbon nanofibers catalysts by Vicente Jiménez; Paula Sánchez; Paraskevi Panagiotopoulou; José Luís Valverde; Amaya Romero (pp. 35-44).

Display Omitted▶ In solo-CO methanation high conversion and selectivity is obtained. ▶ Catalytic performance of CO₂ alone is not affected by type of CNFs. ▶ Addition of 30% water vapour in the feed inhibits the RWGS. ▶ Addition of 30% water vapour enhancing CO hydrogenation.The catalytic performance of ruthenium catalysts supported on carbon nanofibers for the methanation of CO, CO₂ and their mixture has been investigated with respect to the nature of carbon nanofibers (orientation of graphite planes): platelet, fishbone and ribbon. Experiments were conducted in the temperature range of 200–500°C using feed compositions relevant to those of reformate gas streams, both in the absence and in the presence of water. It has been found that, under conditions of solo-CO methanation, all the investigated catalysts are able to completely and selectively convert CO at temperatures around 340°C, with the conversion of CO being somewhat higher for the Ru/platelet sample. For hydrogenation of CO₂ alone, catalytic performance is not affected by the nature of the carbon nanofibers used as support. In combined hydrogenation of CO/CO₂ mixtures, catalytic performance for all the investigated catalysts is poor since they promote the undesired reverse water–gas shift reaction. However, addition of 30% water vapour in the feed inhibits the reverse water–gas shift, thereby enhancing CO hydrogenation. Results of kinetic measurements show that the turnover frequency of CO conversion becomes 2–3 times higher in the presence of steam over Ru/fishbone and Ru/platelet samples over the whole temperature range examined, whereas in the case of Ru/ribbon catalyst temperatures higher than 250°C are required in order to achieve higher turnover frequency values. Carbon dioxide hydrogenation is not affected by the presence of steam. For all experimental conditions investigated, selectivity toward methane increases with increasing temperature at the expense of higher hydrocarbons and is enhanced with the addition of water vapour in the gas mixture.

Keywords: CO methanation; CO; ₂; methanation; Selective methanation of CO; Ruthenium; Fuel cell applications; Carbon nanofibers

Transesterification of ethyl butyrate with methanol over 1-butyl-3-methylimidazolium exchanged mordenite by Eisuke Yoda (pp. 45-50).

Display Omitted▶ Transesterification occurred on the organic cation-exchanged mordenite ([bmim]M20). ▶ Transesterification improved by addition of NaCl. ▶ A reaction mechanism was proposed for the transesterification on [bmim]M20.Transesterification of ethyl butyrate with methanol on the organic cation-exchanged mordenite ([bmim]M20) was studied in order to examine the reactivity of the methoxide ions that were generated on [bmim]M20 by the dissociation of methanol. Since transesterification occurred by addition of NaCl, the methoxide ions on [bmim]M20 were demonstrated to be utilizable in the reaction. The activity improved with a concentration of NaCl below 3mmolL⁻¹, whereas it was constant at concentrations above 3mmolL⁻¹. The adsorption of ethyl butyrate on the partially ion-exchanged [bmim]M20 samples was observed by FT-IR spectroscopy. It was found that it was difficult for ethyl butyrate to enter the micropores of [bmim]M20. From these results, a reaction mechanism was proposed in which the methoxide ions generated in the micropores of [bmim]M20 reacted with ethyl butyrate after they diffused outside of the micropores.

Keywords: HM20; FT-IR; Organic cation; Transesterification

Transesterification of ethyl butyrate with methanol over 1-butyl-3-methylimidazolium exchanged mordenite by Eisuke Yoda (pp. 45-50).

Keywords: HM20; FT-IR; Organic cation; Transesterification

Palladium nanoparticles heterogeneous nucleation within organically grafted silica foams and their use as catalyst supports toward the Suzuki–Miyaura and Mizoroki–Heck coupling reactions by S. Ungureanu; H. Deleuze; O. Babot; M.-F. Achard; C. Sanchez; M.I. Popa; R. Backov (pp. 51-58).

Display Omitted▶ Palladium nanoparticles have been heterogeneously nucleated within hybrid organic–inorganic foams. ▶ The new as-synthesized “Pd@organo-Si(HIPE)” open-cell catalysts have been tested for the Suzuki–Miyaura and Mizoroki–Heck coupling reactions. ▶ Thiphenylphosphine (PPh₃) is favouring nanoparticles stabilization and activation. ▶ The catalysts Pd@gMercapto-Si(HIPE)-P4 and Pd@g3Amino-Si(HIPE)-P4 under addition of (PPh₃) are offering high yields, turnover and cycling performances for the Mizoroki–Heck coupling reaction.Palladium nanoparticles supported within hybrid organic–inorganic foams have been generated. The as-synthesized catalysts, labeled “Pd@gOrgano-Si(HIPE)” (high internal phase emulsion), have been tested with or without addition of triphenylphosphine (PPh₃), considering both the Suzuki–Miyaura and Mizoroki–Heck coupling reactions. Particularly, the catalysts Pd@gMercapto-Si(HIPE)-P4 and Pd@g3Amino-Si(HIPE)-P4 under addition of (PPh₃) in a molar ratio 4:1 relative to palladium, are offering good yields, turnover and cycling performances for the Mizoroki–Heck coupling reaction.

Keywords: Foams; Silica; Hybrid materials; Nanoparticles; Catalysis

Study of the selectivity in FCC naphtha hydrotreating by modifying the acid–base balance of CoMo/γ-Al₂O₃ catalysts by David J. Pérez-Martínez; Pierre Eloy; Eric M. Gaigneaux; Sonia A. Giraldo; Aristóbulo Centeno (pp. 59-70).

Display Omitted▶ CoMo/γ-Al₂O₃ catalysts were modified with the introduction of a dopant (B, Na or K). ▶ Dopants influence the acid–base balance and the Co and Mo oxide species distribution. ▶ Double-bond isomerization reaction from terminal to internal positions was promoted. ▶ Improvements in the selectivity HDS/HYDO were related to double-bond isomerization. ▶ HDS activity reductions were related to Co and Mo oxide species distribution.CoMo catalysts supported on a commercial γ-Al₂O₃ modified with B, Na or K were prepared in order to analyze the effect of acid–base characteristics on the FCC naphtha hydrotreatment. Catalysts were characterized by NH₃ TPD, IR of pre-adsorbed pyridine and CO₂, XPS, Raman, and XRD. In general, with either boron or alkaline metal modification the HDS/HYDO selectivity did not significantly improve. However, it is remarkable that when the alumina was modified to be either more acidic (B) or more basic (K, Na), improvements in the ratio between the HDS and the conversion of the internal branched olefin as well as in the ratio double-bond isomerization to HYD of linear olefins were observed. For both modifications, this fact was related to the promotion of the double-bond isomerization reaction from external to internal positions. For alkaline-doped catalysts, it was found that the double-bond isomerization was related to the existence of basic sites. For the boron, there is a range of boria content (2–3wt.%) where the double-bond isomerization was promoted selectively over the cracking and alkylation reactions because only weak Brönsted acid sites are present. Additionally, both modifications (Boron or alkaline metals) of alumina led to a decrease in the HDS activity, which was found to be related to changes in the distribution of Co and Mo species in the oxide state. Alkaline metal introduction led to the formation of alkaline metal molybdates, whereas boron introduction increased the proportion of octahedral polymeric Mo species, consequently, decreasing the dispersion of the Mo phase.

Keywords: FCC naphtha; CoMo; HDS/HYDO selectivity; Acid–base balance; Double-bond isomerization

A comparative study of “standard”, “fast” and “NO₂” SCR reactions over Fe/zeolite catalyst by Masaoki Iwasaki; Hirofumi Shinjoh (pp. 71-77).

Display Omitted▶ NO_x conversion decreased in the following order: fast SCR>NO₂SCR>standard SCR. ▶ N₂O production reached a maximum at ca. 250°C and was responsible for NO₂ SCR. ▶ NO_x conversion that excluded N₂O production was ranked: fast>standard>NO₂ SCR. ▶ Standard and NO₂ SCR progressed once fast SCR was completed. ▶ NO₂ SCR conversion began to increase below 180°C with no N₂O production.In order to elucidate the contributions of standard (NO₂/NO_x=0%), fast (=50%) and NO₂ (=100%) SCR reactions under conditions where they occur simultaneously, the NO_x conversion rate and N₂O production rate over Fe/zeolite were investigated while varying both NO₂/NO_x ratio and temperature, in small increments. The NO_x conversion rate decreased in the following order: fast SCR>NO₂ SCR>standard SCR, although after excluding the contribution of N₂O production, the order was changed to fast SCR>standard SCR>NO₂ SCR. When the fast SCR conversion was subtracted from the total NO_x conversion, the remaining “apparent” conversion of standard SCR (NO₂/NO_x<50%) or NO₂ SCR (>50%), was independent of NO₂/NO_x ratio. This indicates that standard or NO₂ SCR progressed once fast SCR was completed. N₂O production reached a maximum at ca. 250°C and was determined responsible for NO₂ SCR. At temperatures below 200°C, the NO_x conversion behaviors of fast and NO₂ SCR changed drastically; the fast SCR conversion dropped suddenly with decreasing temperature, and the NO₂ SCR conversion went through a minimum and then began to increase with no N₂O production.

Keywords: SCR; Zeolite; Fe; Ammonia; Reaction mechanism

A comparative study of “standard”, “fast” and “NO₂” SCR reactions over Fe/zeolite catalyst by Masaoki Iwasaki; Hirofumi Shinjoh (pp. 71-77).

Keywords: SCR; Zeolite; Fe; Ammonia; Reaction mechanism

Synergetic effect of a mixture of activated carbon+Ni/Al₂O₃ used as catalysts for the CO₂ reforming of CH₄ by Beatriz Fidalgo; Ana Arenillas; José Ángel Menéndez (pp. 78-83).

Display Omitted▶ A synergetic effect exists between the carbon fraction and the metal-based fraction. ▶ Conversions over FY5+Ni/Al₂O₃ are higher than those expected from the mixtures law. ▶ The decomposition of CH₄ occurs preferentially over the Ni/Al₂O₃. ▶ The CO₂ tends to gasify the initial carbon, as well as, the carbon deposits from CH₄.In this work the catalytic activity of heterogeneous mixtures of an activated carbon, FY5, and an in-lab prepared Ni/Al₂O₃ in the CO₂ reforming of CH₄ reaction was investigated. Initially, the reaction was carried out over FY5 and Ni/Al₂O₃ separately. Under the operating conditions employed, the CO₂ and CH₄ conversions obtained over FY5 were negligible, whereas they were high and steady over Ni/Al₂O₃. In the latter case, it was found that the spinel NiAl₂O₄ was formed due to the interaction between the reduced Ni and the support during heating under a N₂ atmosphere. The reaction was also carried out over different mixtures of FY5+Ni/Al₂O₃. The experimental conversions thus attained were higher than the conversions calculated by adding the weighted individual conversions (mixtures law). Therefore, a synergetic effect exists between the carbonaceous fraction and the metal-based fraction. This effect was found to increase with temperature. Differences between the experimental and theoretical CO₂ conversion were also observed to increase when the proportion of FY5 in the mixture was increased, whereas in the case of CH₄ conversion, the increase depended on the proportion of Ni/Al₂O₃ added. It was also observed that, when a heterogeneous mixture FY5+Ni/Al₂O₃ was used as catalyst for the CO₂ reforming of methane, the decomposition of CH₄ occurred preferentially over the Ni-based fraction and that CO₂ tended to gasify both the initial carbonaceous fraction and the carbon deposits from methane.

Keywords: Synergy; Carbon-based catalyst; Dry reforming

Synergetic effect of a mixture of activated carbon+Ni/Al₂O₃ used as catalysts for the CO₂ reforming of CH₄ by Beatriz Fidalgo; Ana Arenillas; José Ángel Menéndez (pp. 78-83).

Keywords: Synergy; Carbon-based catalyst; Dry reforming

Catalytic reaction characterization using micromachined nanocalorimeters by Keith D. Hurley; Brian G. Frederick; William J. DeSisto; Adriaan R.P. van Heiningen; M. Clayton Wheeler (pp. 84-93).

Display Omitted▶ 4-Element nanocalorimeter arrays with 50nJ/K sensitivity have been evaluated as catalyst screening platforms. ▶ Combined heat and mass transfer models using both a 2-D finite element method and a 1-D mathematical method were used to model calorimeter response to reaction power. ▶ Reaction rate for catalytic hydrogen oxidation was measured using ramped temperature programming and hysteresis and oscillations in reaction rates were observed. ▶ The 1-D model was used to determine model parameters for mass transfer and reaction kinetics for a range of hydrogen concentrations. ▶ Unique millisecond pulsed temperature programming method suggests that the hysteresis and oscillations result from kinetic surface coverage phase transitions. ▶ Results were used to discuss the utility of the method for catalyst screening.Nanocalorimeters based on a micromachined hotplate platform were characterized for potential applications in catalyst screening and reaction mechanism studies. The nanocalorimeters were designed to limit heat loss to the surroundings, resulting in a small heat capacity (50nJK⁻¹) and thermal time constant (1ms). This greatly increases the sensitivity of the device, allowing reaction heat flows on the order of <1μW to be measured in air. The Pt catalyzed combustion of hydrogen in air was used as a model reaction. A relatively-simple heat and mass transfer model was developed which accurately described the data from the microscale system, and the rate-limited and mass transfer-limited regimes of the ignition traces were clearly distinguished. An average activation energy of 48±4kJmol⁻¹ was determined for the Pt catalyzed combustion of hydrogen in air. However, unique rapid temperature programmed calorimetry methods convincingly demonstrate that the activation energy is influenced by kinetic phase transitions which also result in reaction rate bistabilities and oscillations.

Keywords: Calorimetry; Catalyst screening; Temperature programmed reaction; Light-off; Ignition; Diffusion limited; Reaction limited

Catalytic reaction characterization using micromachined nanocalorimeters by Keith D. Hurley; Brian G. Frederick; William J. DeSisto; Adriaan R.P. van Heiningen; M. Clayton Wheeler (pp. 84-93).

Keywords: Calorimetry; Catalyst screening; Temperature programmed reaction; Light-off; Ignition; Diffusion limited; Reaction limited

Silylcarbonylation of styrenes catalyzed by iridium(I) siloxide complexes by Ireneusz Kownacki; Bogdan Marciniec; Peter Eilbracht (pp. 94-101).

Display Omitted▶ Application of iridium(I) siloxide complexes for catalytic silylcarbonylation of olefins. ▶ [{Ir(μ-OSiMe₃)(cod)}₂] effectively catalyzes formation of acylsilane silyl enolates. ▶ Exemplary syntheses of acylsilane derivatives are presented. ▶ Scheme of catalysis of styrene silylcarbonylation by [{Ir(μ-OSiMe₃)(cod)}₂] is also presented.This paper reports the study of iridium(I) catalyzed the incorporation of HSiMe₂Ph and carbon monoxide to styrene and its derivatives. Comparative catalytic tests performed for the various iridium(I) precursors [{Ir(μ-X)(diene)}₂] (where X=OMe, OAc, OSiMe₃; diene=1,5-cyclooctadiene (cod), tetrafluorobenzobarrelene (tfb)) and [Ir(CO)₃(PCy₃)(SiPh₃)] showed that the binuclear complex [{Ir(μ-OSiMe₃)(cod)}₂] is the most efficient catalyst of the process studied and gives the main silylcarbonylation product, i.e. enol silyl ethers of acylsilanes (RCH₂CHC(OSiMe₂Ph)SiMe₂Ph, where R=Ph, aryl) with relatively good yield. It enabled us to synthesize and isolate the exemplary acylsilane silyl enolates illustrating the potential application of binuclear siloxide iridium(I) complex in the synthesis of so useful in organic synthesis unsaturated organosilicon derivatives. Catalytic results as well as the detailed study of stoichiometric reaction of [{Ir(μ-OSiMe₃)(cod)}₂] and [Ir(CO)₂(PCy₃)(OSiMe₃)] with the reaction substrates also under pressure of CO enabled us to propose a general catalytic scheme of the silylcarbonylation process including the formation of enol silyl ethers of acylsilanes as a main product accompanied by silyl enol ethers of aldehydes and products of styrene hydrosilylation.

Keywords: Silylcarbonylation; Iridium(I) siloxide complexes; Enol silyl ethers of acylsilanes

Silylcarbonylation of styrenes catalyzed by iridium(I) siloxide complexes by Ireneusz Kownacki; Bogdan Marciniec; Peter Eilbracht (pp. 94-101).

Keywords: Silylcarbonylation; Iridium(I) siloxide complexes; Enol silyl ethers of acylsilanes

Synthesis of zeolite crystals with unusual morphology: Application in acid catalysis by F. Ocampo; J.A. Cunha; M.R. de Lima Santos; J.P. Tessonnier; M.M. Pereira; B. Louis (pp. 102-109).

Display Omitted▶ Synthesis of ZSM-5 zeolite having a peculiar crystal growth into nano-French fries shaped nanocrystals, 50–100nm in size. ▶ Use of cheap sugar cane bagasse as a sacrificial exo-template. ▶ Microscopic design of zeolite crystal assemblies. ▶ Twice higher reactivity for rectangular nanocrystal when compared to conventional prismatic micro-sized crystals in the cracking reaction. ▶ High selectivity toward propylene.ZSM-5 zeolite nanocrystals having a rectangular morphology (French fries-like) and a size comprised between 50 and 100nm were prepared using cheap sugar cane bagasse as a sacrificial template. Two sugar cane biomass types, un-treated and acid hydrolyzed bagasse, were used. A relationship has been established between the chemical composition of the sacrificial vegetal and the morphology of grown zeolite crystals. Aligned zeolite nanocrystals were allowed to grow on non hydrolyzed sugar cane substrate, using a combination of supramolecular templating and conventional self-assembly of template cations and silica species. The latter material allowed enhanced diffusional properties in comparison with purely microporous zeolite, as well as ZSM-5 crystals grown on hydrolyzed bagasse. Their catalytic behavior in n-hexane cracking reaction led to a higher selectivity toward light olefins. The double novelty consists in the manufacture of hierarchical zeolite microspheres (diameter about 1μm) formed by the self-aggregation of rectangular subunits. In addition, a renewable vegetal source can be used as a supramolecular template in replacement of expensive polymers.

Keywords: Sugar cane bagasse; ZSM-5; Nanocrystals; Zeolite; n-Hexane cracking; Thiele–Weisz modulus

Synthesis of zeolite crystals with unusual morphology: Application in acid catalysis by F. Ocampo; J.A. Cunha; M.R. de Lima Santos; J.P. Tessonnier; M.M. Pereira; B. Louis (pp. 102-109).

Keywords: Sugar cane bagasse; ZSM-5; Nanocrystals; Zeolite; n-Hexane cracking; Thiele–Weisz modulus

Heterogeneous photodegradation catalysis of o-phenylenediamine using CuO/X zeolite by Alireza Nezamzadeh-Ejhieh; Zahra Salimi (pp. 110-118).

Display Omitted▶ Aqueous solution of o-phenylendiamil was degraded by zeolite X incorporated CuO under UV irradiation. ▶ CuO inside the zeolite is active center for degradation. ▶ The results of TOC and COD and UV–vis indicate complete degradation of pollutant.In this paper, the photocatalytic degradation of o-phenylenediamine as the deputy of organic pollutant in aqueous solutions with CuO/X zeolite as a photocatalyst under UV irradiation has been studied. Photocatalyst was prepared by ion exchanging process of parent synthetic zeolite NaX with copper(II) nitrate aqueous solution (0.1M) for 8h followed by drying and calcination at 450°C for 4h. The parent zeolite, ion exchanged media, and photocatalyst were characterized by X-ray diffraction, infrared spectroscopy, atomic absorption spectroscopy, BET and thermal analysis methods. The degradation process was monitored during the experimental runs through UV/vis absorption as well as COD and TOC concentration determination and HPLC methods. The effects of various key operating parameters and the effect of hydrogen peroxide and potassium bromate on the degradation rate of o-phenylenediamine were studied. The optimum values were 0.1gL⁻¹ of photocatalyst, 10ppm of o-phenylenediamine, pH of 9, 25°C, 20.0mM of H₂O₂ and 10.0mM of KBrO₃. The results showed that the degradation kinetic of OPD can be described by Langmuir–Hinshelwood equation.

Keywords: Photocatalytic degradation; o; -phenylenediamine; Heterogeneous catalysis; Copper(II) oxide; NaX zeolite

Heterogeneous photodegradation catalysis of o-phenylenediamine using CuO/X zeolite by Alireza Nezamzadeh-Ejhieh; Zahra Salimi (pp. 110-118).

Keywords: Photocatalytic degradation; o; -phenylenediamine; Heterogeneous catalysis; Copper(II) oxide; NaX zeolite

Selective hydrogenolysis of glycerol to 1,3-propanediol over a Pt/WO₃/TiO₂/SiO₂ catalyst in aqueous media by Leifeng Gong; Yuan Lu; Yunjie Ding; Ronghe Lin; Jingwei Li; Wenda Dong; Tao Wang; Weimiao Chen (pp. 119-126).

Display Omitted▶Pt/WO₃/TiO₂/SiO₂ was selective for glycerol hydrogenolysis to 1,3-propanediol. ▶ The presence of TiO₂ species in the catalyst favored the dispersion of platinum. ▶ The addition of WO₃ regulated acidity of the catalyst. ▶ Water preferably served as the reaction medium.SiO₂-supported Pt/WO₃/TiO₂ catalysts were prepared; they were found to be more active and selective than the Pt/WO₃/TiO₂ catalyst for glycerol hydrogenolysis to 1,3-propanediol in a slurry batch reactor. The influences of catalyst component, reaction medium, reaction temperature, H₂ pressure and reaction time on glycerol hydrogenolysis over the Pt/WO₃/TiO₂/SiO₂ catalyst were investigated. XRD, TEM, NH₃-TPD and Py-IR characterization were employed to reveal the roles of WO₃ and TiO₂ in the performance of the Pt based-catalysts. XRD patterns and TEM images showed that the presence of TiO₂ species in the catalyst favored the dispersion of platinum. The weak Brønsted acid sites formed by addition of WO₃ to the catalyst were concluded to play a key role in selective formation of 1,3-propanediol, based on the results of NH₃-TPD and Py-IR characterization.

Keywords: Glycerol; Hydrogenolysis; 1,3-Propanediol; Acidity

Quantitative determination of acid sites on silica–alumina by I.S. Pieta; M. Ishaq; R.P.K. Wells; J.A. Anderson (pp. 127-134).

Display Omitted▶ Quantification of both Lewis and Brønsted acid sites by combined FTIR and gravimetric measurement. ▶ Three nitrogen bases describe the distribution of sites of different acid strength and accessibility. ▶ Correlation between site density and activity for acetone condensation show the latter to be catalysed by Lewis acid sites.The density of acid sites on amorphous silica alumina has been determined using a combination of gravimetric and spectroscopic analysis using pyridine and 2,4-lutidine and 2,6-lutidine for surfaces treated at different calcination temperatures. An attempt was made to correlate the number of acid sites determined by the different base molecules with the activity for liquid phase reaction of acetone to produce diacetone alcohol at 298K. The best correlation was obtained with the number of Lewis acid sites which were able to retain pyridine after evacuation at 473K. The lutidines underestimated the number of Lewis sites on the oxide surface. In particular, 2-6-lutidine was only able to detect Lewis acid sites in geometries at edges and other geometric imperfections on the solid and these were mainly generated after low temperature (573K) calcination treatment.

Keywords: Solid acid; Silica alumina; Acid site determination; Lutidines; Pyridines; Quantitative FTIR

Quantitative determination of acid sites on silica–alumina by I.S. Pieta; M. Ishaq; R.P.K. Wells; J.A. Anderson (pp. 127-134).

Keywords: Solid acid; Silica alumina; Acid site determination; Lutidines; Pyridines; Quantitative FTIR

Copper- and solvent-free Sonogashira coupling reactions of aryl halides with terminal alkynes catalyzed by 1-phenyl-1,2-propanedione-2-oxime thiosemi-carbazone-functionalized polystyrene resin supported Pd(II) complex under aerobic conditions by Mohammad Bakherad; Ali Keivanloo; Bahram Bahramian; Saeedeh Jajarmi (pp. 135-140).

Display Omitted▶ Efficient heterogeneous catalyst for the Sonogashira reactions was prepared. ▶ PS-ppdot-Pd(II) was fully characterized. PS-ppdot-Pd(II) is active for the copper- and solvent-free coupling reactions of aryl halides and terminal acetylenes. ▶ The catalyst can be reused several times without a noticeable change in activity.A polystyrene-supported palladium(II) 1-phenyl-1,2-propanedione-2-oxime thiosemi-carbazone (PPDOT) complex is found to be a highly active catalyst for the Sonogashira coupling reactions of aryl halides with terminal alkynes. The reactions can be performed under copper- and solvent-free conditions in an air atmosphere. The palladium catalyst is easily separated, and can be reused for several times without a significant loss in its catalytic activity.

Keywords: Copper-free; Sonogashira coupling; Supported catalyst; Aryl halides

Hydrogenation versus isomerization in the reaction of cis-2-butene-1,4-diol over supported catalysts: The role of Group VIII transition metals in driving the products selectivity by Maria Grazia Musolino; Cinzia V. Caia; Francesco Mauriello; Rosario Pietropaolo (pp. 141-147).

Display Omitted▶ Effect of Group VIII transition metals on the activity and selectivity on the cis-2-butene-1,4-diol hydrogenation. ▶ σ-Alkyl as key intermediate explaining the products selectivity in the mechanism of the reaction. ▶ Discrimination between Pt, Ir and Ni metals favouring the hydrogenation and Rh, Pd and Ru promoting the isomerization. ▶ Relation between electronic factors and selectivity of metals.Silica supported Group VIII metal catalysts (Pd, Pt, Ru, Rh and Ir) have been tested at 303K in liquid-phase reaction of cis-2-butene-1,4-diol with hydrogen at atmospheric pressure. The catalysts have been characterized by TPR, XRD and TEM. The catalytic activity changes in the order: Pd≫Rh>Pt>Ru>Ir. Significant differences were observed in products distribution. Ir/SiO₂ and Pt/SiO₂ favour the hydrogenation reaction to butane-1,4-diol, whereas Rh/SiO₂, Pd/SiO₂ and Ru/SiO₂ significantly promote double bond and geometric isomerization processes, leading to 2-hydroxytetrahydrofuran and trans-2-butene-1,4-diol, respectively. Formation of products, deriving from isomerization and hydrogenation reactions, is explained on the basis of a mechanism involving a common σ-alkyl metal bonded intermediate and the variation in products distribution among the various metals is rationalized taking into account electronic factors.

Keywords: Supported Group VIII metal catalysts; Cis-2-butene-1,4-diol hydrogenation; Isomerization; σ; -Alkyl intermediate; Electronic parameters

Ni–Nb–O catalysts for ethane oxidative dehydrogenation by B. Savova; S. Loridant; D. Filkova; J.M.M. Millet (pp. 148-157).

Display Omitted▶ High catalytic properties of NiO based catalysts in the oxidative dehydrogenation of ethane are reported. ▶ Catalytic properties are related to the reduction of the surface over-stoichiometry of NiO. ▶ The reduction of the surface over-stoichiometry of NiO can be obtained by addition of Nb or oxalic acid. ▶ The study of the catalysts over long periods of time showed that they underwent a slow but systematic deactivation.Ni–Nb–O catalysts with various Nb contents (0–19%) have been studied as catalysts for the oxidative dehydrogenation of ethane. An optimum ethane conversion of 33% with 78% of selectivity to ethylene was obtained for a Ni–Nb–O catalyst containing 15% of Nb at 350°C with a weight to flow W/F ratio of 0.54gsmL⁻¹. The catalysts have been characterized using various techniques allowing to show that the efficiency of the catalysts was related to a surface interaction between the NiO active phase and an amorphous Nb₂O₅ phase. Because ammonium oxalato niobate was used as niobium precursor, oxalate ions were present; concomitantly to the surface interaction described, the thermal decomposition of these oxalate ions induced a reduction in NiO oxygen over-stoichiometry which also influences the catalytic properties. It was demonstrated that only a small percent of Nb was necessary to have these effects and the optimal activity observed for 15% of Nb had to be related to another process which corresponds to the decrease in the active phase particle size induced by the amorphous Nb₂O₅ phase; this phase prevents the sintering of the active phase particles during the thermal transformation of the catalysts precursors. It was also shown that the thermal decomposition of oxalates limits NiO crystal growth. Above 15% of Nb the amorphous phase reacted with the nickel oxide to form an inactive mixed niobium and nickel oxide phase NiNb₂O₆. The study of the catalytic properties over long periods of time showed that the Ni–Nb–O catalysts underwent a slow but systematic deactivation. This deactivation has been attributed both to the continuous reduction of the NiO oxygen over-stoichiometry in the reaction conditions and to the formation of the NiNb₂O₆ phase thermodynamically stable at the catalytic reaction temperature. Attempt to regenerate the catalysts has failed.

Keywords: Ethane oxidative dehydrogenation; Ethylene; Ni–Nb–O mixed metal oxides; Active sites isolation; Oxygen over-stoichiometry; O; ⁻; electrophilic species; Catalyst deactivation

Ni–Nb–O catalysts for ethane oxidative dehydrogenation by B. Savova; S. Loridant; D. Filkova; J.M.M. Millet (pp. 148-157).

Keywords: Ethane oxidative dehydrogenation; Ethylene; Ni–Nb–O mixed metal oxides; Active sites isolation; Oxygen over-stoichiometry; O; ⁻; electrophilic species; Catalyst deactivation

Synthesis of nopol via Prins condensation of β-pinene and paraformaldehyde catalyzed by sulfated zirconia by Sumit V. Jadhav; Krishna Mohan Jinka; Hari C. Bajaj (pp. 158-165).

Display Omitted▶ Application of sulfated zirconia as an efficient solid acid catalyst. ▶ Synthesis of nopol via Prins condensation of β-pinene and paraformaldehyde. ▶ SZ-2N_Calcn catalyst resulted in 99% conversion of β-pinene with∼99% selectivity. ▶ Catalyst can be recycled with little loss in activity up to five cycles.The present work describes the novel application of sulfated zirconia (SZ) solid acid catalysts for the synthesis of nopol via Prins condensation of β-pinene and paraformaldehyde. SZ catalysts with different percentages of sulfur loadings have been synthesized and characterized using various physico-chemical techniques like PXRD, FT-IR, surface area analysis and NH₃–TPD studies. The influences of various reaction parameters such as sulfur loading, reaction temperature, molar ratio of reactants, reaction time, solvent effect and reusability of the catalyst have been investigated. SZ catalyst synthesized by impregnation of 2N sulfuric acid solution over Zr(OH)₄ was found to be a highly selective catalyst for β-pinene conversion (>99%) with ∼99% selectivity to nopol. The catalyst could be reused up to five cycles with minor loss in catalytic activity for β-pinene conversion, while the nopol selectivity remains unaffected.

Keywords: Solid acid; Sulfated zirconia; Prins condensation; β-pinene; Paraformaldehyde; Nopol

Synthesis of nopol via Prins condensation of β-pinene and paraformaldehyde catalyzed by sulfated zirconia by Sumit V. Jadhav; Krishna Mohan Jinka; Hari C. Bajaj (pp. 158-165).

Keywords: Solid acid; Sulfated zirconia; Prins condensation; β-pinene; Paraformaldehyde; Nopol

New composite materials as support for selective hydrogenation; egg-shell catalysts by J.M. Badano; C. Betti; I. Rintoul; J. Vich-Berlanga; E. Cagnola; G. Torres; C. Vera; J. Yori; M. Quiroga (pp. 166-174).

Graphical description of the procedure impregnation of the new composite supports to obtain Pd egg-shell catalyst.Display Omitted▶ New Composites Supports were developed to obtain egg-shell catalysts. ▶ Composites Supports combine hydrophilic-hydrophobic dual properties. ▶ Composite Supports have higher mechanical resistance than commercial supports. ▶ Synthesized egg-shell catalysts with Composites Supports have a thin active layer. ▶ Pd-Composite are more active than Pd-commercial in pelletized supports form.It has been demonstrated that using low-cost materials and a relatively simple process, complex supports with a mixed inorganic–organic structure can be synthesized. These supports combine hydrophilic–hydrophobic dual properties and are especially suited for preparing egg-shell supported metal catalysts to be used in highly exothermal catalytic reactions or in systems of consecutive reactions where diffusive problems decrease the selectivity. The synthesized supports have an extremely thin active layer. They also proved to be more mechanically resistant than other commercial supports thus being amenable for use in continuous processes with long packed beds. Pd catalysts supported over the new composite materials were found to be highly active for the selective hydrogenation of styrene, a representative compound of pyrolisis gasolines. They also displayed smaller diffusive constraints than other Pd catalysts prepared from commercial supports.

Keywords: Heterogeneous catalysis; Palladium; Egg-shell catalysts; Composite materials

Solvothermal carbon-doped TiO₂ photocatalyst for the enhanced methylene blue degradation under visible light by Juan Matos; Andreína García; Li Zhao; Maria Magdalena Titirici (pp. 175-182).

Display Omitted▶ Synthesis of solvothermal C-TiO₂ as a new kind of dyade structure. ▶ Photodegradation of methylene blue on C-TiO₂ and on TiO₂ was studied. ▶ C-TiO₂ exhibits very strong photo activity in the visible range. ▶ Carbon photoassist the TiO₂ in the photodegradation of methylene blue.Photodegradation of methylene blue on a carbon-doped TiO₂ and on pure TiO₂ was studied. The materials were prepared by solvothermal synthesis and by calcinations. N₂ adsorption, XRD, SEM and TEM characterization was performed. Both nanomaterials exhibited mesoporous textures and the TiO₂ frameworks consist mainly of anatase phase. SEM images showed spherical microparticles while the TEM images showed hierarchically nanostructured morphologies on both samples. C-TiO₂ exhibited higher apparent first-order rate constants for the degradation of methylene blue than those obtained on pure TiO₂. It could be concluded that under visible light, the photoactivity of carbon-doped TiO₂ was clearly higher than that of a commercial TiO₂ photocatalyst suggesting that the carbon part photo assist the TiO₂ in the photodegradation of methylene blue.

Keywords: Photocatalysis; Methylene blue photodegradation; Carbon-doped TiO; ₂; Synergy

Solvothermal carbon-doped TiO₂ photocatalyst for the enhanced methylene blue degradation under visible light by Juan Matos; Andreína García; Li Zhao; Maria Magdalena Titirici (pp. 175-182).

Keywords: Photocatalysis; Methylene blue photodegradation; Carbon-doped TiO; ₂; Synergy

Esterification of free fatty acids to biodiesel over heteropolyacids immobilized on mesoporous silica by A.I. Tropecêlo; M.H. Casimiro; I.M. Fonseca; A.M. Ramos; J. Vital; J.E. Castanheiro (pp. 183-189).

Display Omitted▶ Esterification of free fatty acids with methanol were carried out over heteropolyacids immobilized on SBA-15. ▶ High heteropolyacid dispersion on SBA-15 was obtained. ▶ High catalytic activity with low amount of tungstophosphoric acid immobilized on SBA-15 was observed.Tungstophosphoric acid (PW), molybdophosphoric acid (PMo) and tungstosilicic acid (SiW) immobilized on SBA-15 were used, as catalysts, in the esterification of palmitic acid with methanol, at 60°C. Catalysts were characterized by N₂ adsorption, FTIR, X-ray diffraction, ICP-AES and TEM.All catalysts exhibited high catalytic activity in palmitic acid esterification with methanol. It was observed that the catalytic activity decreases in the follow series: PW1-SBA-15>SiW-SBA-15>PMo-SBA-15.A series of PW immobilized on SBA-15 with different PW loadings from 2.7wt% to 8.3wt% were prepared. It was observed high catalytic activity with low amount of tungstophosphoric acid immobilized on SBA-15.In order to optimize the reaction conditions, the effect of different parameters, such as catalyst loading, carbon length of the alcohol and temperature, molar ratio of fatty acid to methanol in the presence of PW3-SBA-15 were studied.PW3-SBA-15 catalyst can be separated from reaction system for re-use. It was observed a small leaching of the PW from SBA-15 to liquid phase.PW3-SBA-15 catalyst was also used in the esterification of stearic and oleic acid with methanol. High catalytic activity was observed.

Keywords: Biodiesel; Heteropolyacids; Esterification; Free fatty acids; SBA-15

The effect of oxalic acid and glyoxal on the VO( acac)₂-catalyzed cyclohexane oxidation with H₂O₂ by Alexander Pokutsa; Yulia Kubaj; Andriy Zaborovskyi; Dariya Maksym; Jacques Muzart; Andrzej Sobkowiak (pp. 190-194).

Display Omitted▶ The benign process of cyclohexane oxidation by H₂O₂ was studied. ▶ Vanadyl(IV)-acetylacetonate, oxalic acid and glyoxal additives have been explored. ▶ The efficiency of such system in the enhancing of aimed products yield was revealed. ▶ The putative mechanism of the oxidation process was suggested.A new protocol for the effective oxidation of cyclohexane in acetonitrile at 40°C and atmospheric pressure into cyclohexanol, cyclohexanone and cyclohexyl hydroperoxide using hydrogen peroxide as the oxidant, vanadyl(IV)-acetylacetonate as the catalyst, oxalic acid and glyoxal as additives is presented with some reaction mechanism proposals.

Keywords: Cyclohexane; Oxidation; Hydrogen peroxide; Vanadyl(IV)-acetylacetonate; Vanadium(V)-oxide; Oxalic acid; Glyoxal

Photocatalytic hydrogen evolution over SiO₂-pillared and nitrogen-doped titanic acid under visible light irradiation by Xiukai Li; Bing Yue; Jinhua Ye (pp. 195-200).

Display Omitted▶ Silica-pillared and non-pillared H₂Ti₄O₉ samples were doped with nitrogen for visible light photocatalysis. ▶ SiO₂–H₂Ti₄O₉–N has expanded interlayer spacing and better retained layered structure than H₂Ti₄O₉–N. ▶ The SiO₂–H₂Ti₄O₉–N sample showed much higher photocatalytic activity for H₂ evolution than non-pillared H₂Ti₄O₉–N.Silica-pillared and non-pillared H₂Ti₄O₉ samples were doped with nitrogen from urea as a nitrogen precursor for visible light photocatalysis. The photocatalytic activities of the nitrogen-doped samples were evaluated for hydrogen evolution from aqueous methanol solution. Techniques such as XRD, FT-IR, TG-DSC, SEM, XPS, and UV–visible diffuse reflectance spectroscopy were adopted to explore the characteristics of the materials. The silica-pillared H₂Ti₄O₉ sample is more stable than the non-pillared one, and its layered structure was retained well at temperatures up to 500°C. The interlayer spacing of H₂Ti₄O₉ was expanded from 2.7Å to 7.2Å after being pillared with silica. Silica pillaring could have a profound impact on nitrogen doping and the resultant photocatalytic activity. The interlayer spacing of the silica-pillared H₂Ti₄O₉ did not change after nitrogen doping; in contrast, that of the non-pillared H₂Ti₄O₉ was reduced by 44% after the same doping process, despite the fact that the non-pillared sample showed better nitrogen doping properties. With expanded interlayer spacing and better retained layered structure, the silica-pillared and nitrogen-doped H₂Ti₄O₉ performed much better than the non-pillared counterpart for hydrogen evolution under visible light irradiation.

Keywords: Photocatalysis; Visible light; Titanic acid; Nitrogen doping; Hydrogen evolution

Photocatalytic hydrogen evolution over SiO₂-pillared and nitrogen-doped titanic acid under visible light irradiation by Xiukai Li; Bing Yue; Jinhua Ye (pp. 195-200).

Keywords: Photocatalysis; Visible light; Titanic acid; Nitrogen doping; Hydrogen evolution

A comparative study of CeO₂–La₂O₃-based Cu catalysts for the production of hydrogen from simulated coal-derived syngas by Y. Sun; S.S. Hla; G.J. Duffy; A.J. Cousins; D. French; L.D. Morpeth; J.H. Edwards; D.G. Roberts (pp. 201-209).

Display Omitted▶ High catalyst activity is approximately proportional to the magnitude of Cu% dispersion. ▶ CeO₂ plays an important role in maintaining high activity and stability. ▶ The high catalyst activity and stability might originate from the synergistic effect of the interaction between metal and support as well as the redox behaviour of catalyst support.CeO₂–La₂O₃-based Cu catalysts were investigated for their ability to produce hydrogen from simulated coal-derived syngas via the water–gas shift reaction in the temperature range of 450–600°C. CeO₂–La₂O₃-based Cu catalysts exhibited high activity and stability at high temperatures ( T≥550°C) with dry-gas hourly space velocity=239,000ml/hg_cat. and at atmospheric pressure. Furthermore, the activity of CeO₂–La₂O₃-based Cu catalysts was found to be proportional to the magnitude of Cu% dispersion and Cu metal surface area with the highest Cu% dispersion and Cu surface area appearing at the La/Cu atomic ratio of 2.7, achieving the highest activity with 7.8% CO conversion at 550°C and 21.5% CO conversion at 600°C, much higher than commercial iron–chromium high temperature shift catalyst with 5.9% conversion at 450°C. Substitution of Ce by Al in CeO₂–La₂O₃-based Cu catalysts decreased catalyst activity and stability in the temperature range 550–600°C, indicating that CeO₂ plays an important role in maintaining high activity and stability. Addition of Ni to CeO₂–La₂O₃-based Cu catalysts improved their activity at 450°C, but led to reduced activity at temperatures of 550°C and above. The high activity and stability observed may originate from the synergistic effect of the interaction between Cu²⁺ species and catalyst support as well as the redox behaviour of the catalyst support.

Keywords: CeO; ₂; –La; ₂; O; ₃; -based Cu catalyst; Water–gas shift (WGS) catalyst; High temperature (HT); Hydrogen; Coal-derived syngas

Sulfur poisoning of CeO₂–Al₂O₃-supported mono- and bi-metallic Ni and Rh catalysts in steam reforming of liquid hydrocarbons at low and high temperatures by Chao Xie; Yongsheng Chen; Yan Li; Xiaoxing Wang; Chunshan Song (pp. 210-218).

Display Omitted▶ The metal type and reforming temperature have a major impact on the nature of sulfur species on the used Rh and Ni catalysts. ▶ The sulfur tolerance of the Rh and Ni catalysts may be closely correlated with the different sulfur species on their surfaces after hydrocarbon steam reforming with sulfur. ▶ Superior catalyst performance can be achieved by selecting a proper metal formulation and a reforming temperature for sulfur-containing liquid fuels.In order to develop a better understanding on sulfur poisoning of reforming catalysts in fuel processing for hydrogen production, steam reforming of liquid hydrocarbons was performed over CeO₂–Al₂O₃ supported monometallic Ni and Rh and bimetallic Rh–Ni catalysts at 550 and 800°C. XANES was used to identify the sulfur species in the used catalysts and to study their impacts on the metal surface properties probed by XPS. It was found that both monometallic catalysts rapidly deactivated at 550°C, and showed poor sulfur tolerance. Although ineffective for the Ni catalyst, increasing the temperature to 800°C dramatically improved the sulfur tolerance of the Rh catalyst. XANES revealed that metal sulfide and organic sulfide are the dominant sulfur species on the used Ni catalyst, while sulfonate and sulfate predominate on the used Rh catalyst. The presence of sulfur induced severe carbon deposition on the Ni catalyst at 800°C. The superior sulfur tolerance of the Rh catalyst at 800°C may be associated with its capability in sulfur oxidation. It is likely that the formation of the oxygen-shielded sulfur structure of sulfonate and sulfate can suppress the poisoning impact of sulfur on Rh by inhibiting direct rhodium–sulfur interaction. Moreover, XPS indicated that the metal surface properties of the Rh catalysts after the reaction without and with sulfur at 800°C are similar, suggesting that sulfur poisoning on Rh was mitigated under the high-temperature condition. Although the Rh–Ni catalyst exhibited better sulfur tolerance than the monometallic catalysts at 550°C, its catalytic performance was inferior compared with the Rh catalyst in the sulfur-containing reaction at 800°C probably due to the severe carbon deposition on the bimetallic catalyst.

Keywords: Steam reforming; Liquid hydrocarbon; Hydrogen; Rh; Ni; Rh–Ni; Catalyst; Deactivation; Sulfur poisoning; Carbon deposition

α-Pinene isomerisation over heteropoly acid catalysts in the gas-phase by Ali Alsalme; Elena F. Kozhevnikova; Ivan V. Kozhevnikov (pp. 219-224).

Display Omitted▶ The isomerisation of α-pinene, yielding camphene as the main product, was studied in the gas phase over solid heteropoly acid (HPA) catalysts in a fixed-bed continuous flow reactor at 200°C and ambient pressure. ▶ Bulk and SiO₂-supported H₃PW₁₂O₄₀ and bulk Cs_2.5H_0.5PW₁₂O₄₀ possessing strong Brønsted acid sites exhibited high initial activities, but suffered from catalyst deactivation, resulting in low camphene yields. ▶ HPA catalysts supported on Nb₂O₅, ZrO₂ and TiO₂, possessing weaker Brønsted and Lewis acid sites, showed more stable performance in α-pinene isomerisation, with the HPA/TiO₂ giving a camphene yield of 51% and a total camphene and limonene yield of 58%.The isomerisation of α-pinene was studied in the gas phase over solid heteropoly acid (HPA) catalysts in a fixed-bed continuous flow reactor at 200°C and ambient pressure. The catalysts included bulk and SiO₂-supported H₃PW₁₂O₄₀ and bulk Cs_2.5H_0.5PW₁₂O₄₀ possessing strong Brønsted acid sites, as well as composites prepared by supporting 15wt% H₃PW₁₂O₄₀ on Nb₂O₅, ZrO₂ and TiO₂ possessing both Brønsted and Lewis acid sites of moderate strength. The reaction yielded camphene as the main product in a mixture with monoterpene by-products such as limonene, terpinolenes, terpinenes, β-pinene, p-cymene and others. The HPA catalysts with strong Brønsted acid sites exhibited high initial activities, but suffered from catalyst deactivation, resulting in low camphene yields. Conversely, the HPA catalysts supported on Nb₂O₅, ZrO₂ and TiO₂, although weaker acids, showed more stable performance in α-pinene isomerisation. The HPA catalyst supported on TiO₂ gave a camphene yield of 51% and a total camphene and limonene yield of 58%.

Keywords: Heterogeneous acid catalysis; Heteropoly acid; α-Pinene isomerisation

α-Pinene isomerisation over heteropoly acid catalysts in the gas-phase by Ali Alsalme; Elena F. Kozhevnikova; Ivan V. Kozhevnikov (pp. 219-224).

Keywords: Heterogeneous acid catalysis; Heteropoly acid; α-Pinene isomerisation

Ethylbenzene dehydrogenation over binary FeO_x –MeO_y/Mg(Al)O catalysts derived from hydrotalcites by Rabindran J. Balasamy; Alam Khurshid; Ali A.S. Al-Ali; Luqman A. Atanda; Kunimasa Sagata; Makiko Asamoto; Hidenori Yahiro; Kiyoshi Nomura; Tsuneji Sano; Katsuomi Takehira; Sulaiman S. Al-Khattaf (pp. 225-234).

Display Omitted▶ Styrene production by ethylbenzene dehydrogenation. ▶ FeO_x –CoO_y/Mg(Al)O catalyst derived from hydrotalcites. ▶ Fe³⁺ active species assisted by Co²⁺. ▶ Reduction–oxidation mechanism between Fe³⁺ and Fe²⁺.A series of FeO_x– MeO_y/Mg(Al)O catalysts were prepared from hydrotalcite-like compounds as precursors and were tested in the ethylbenzene dehydrogenation to styrene in He atmosphere at 550°C. The hydrotalcite-like precursors of the metal compositions of Mg₃Fe_0.25 Me_0.25Al_0.5 ( Me=Cu, Zn, Cr, Mn, Fe, Co and Ni) were coprecipitated from the nitrates of metal components and calcined to mixed oxides at 550°C. After the calcination, the mixed oxides showed high surface area of 150–200m²g_cat⁻¹, and were mainly composed of (Mg Me)(Fe³⁺Al)O periclase in the bulk, whereas the surface was enriched by (Mg Me)(Fe³⁺Al)₂O₄ pinel. Among the Me species tested, Co²⁺ was the most effective, followed by Ni²⁺. Co²⁺ addition increased the activity of original FeO_x/Mg(Al)O catalyst, whereas Ni²⁺ increased the activity at the beginning of reaction, but deactivated the catalyst during the reaction. The other metals formed isolated MeO_x species in the catalyst, resulting in a decrease in the activity compared to the original FeO_x/Mg(Al)O catalyst. The active Fe species exists as metastable Fe³⁺ on the FeO_x/Mg(Al)O catalyst. By the addition of Co²⁺, the reduction–oxidation between Fe³⁺ and Fe²⁺ was facilitated and, moreover, the active Fe³⁺ species was stabilized. It is likely that the dehydrogenation proceeds on the active Fe³⁺ species via its reduction–oxidation assisted by Co²⁺.

Keywords: Ethylbenzene dehydrogenation; Styrene; FeO; _x; –; Me; O; _y; /Mg(Al)O catalyst; Hydrotalcite

Etherification of glycerol by isobutylene: Tuning the product composition by Hee Jong Lee; Doyoung Seung; Kwang S. Jung; Hwayong Kim; Igor N. Filimonov (pp. 235-244).

Display Omitted▶ Glycerol etherification is characterized by slow equilibration of higher ethers. ▶ Product distribution does not follow simplified kinetic model. ▶ Ionic liquid with Brønsted acid sites and heteropolyacid suppress tri-ether formation. ▶ Partial neutralization of Amberlyst 15 suppresses isobutene oligomerization.Etherification of glycerol by isobutylene was conducted in a batch mode using acidic and partially neutralized Amberlyst-15 ionic resin, p-toluenesulfonic acid, silicotungstic acid, cesium salt of silicotungstic acid, and ionic liquid containing sulfonic acid groups. All the catalysts are comparable in terms of the initial rate of glycerol conversion into mono-ether (except cesium salt of heteropolyacid), but differ substantially with respect to the yields of higher ethers of glycerol.Ionic liquid and heteropolyacid are immiscible/insoluble in higher ethers of glycerol. As a result they have unique capability of suppressing the formation of tri-ether during the initial stage of glycerol conversion.Acidic Amberlyst-15 in the form of fine powder has the highest activity per unit weight for glycerol etherification and relatively high activity in isobutene oligomerization. Partial exchange of acidic protons with cations Na⁺, Ag⁺, Mg²⁺, and Al³⁺ decreases the rates of all the processes, but isobutylene oligomerization is suppressed more efficiently. Ag⁺- and Al³⁺-modified Amberlyst demonstrates higher yields of tri-ether and has specific pattern of interaction with gaseous isobutene distinctive to other metal-substituted Amberlysts.

Keywords: Abbreviations; IB; isobutylene; HSiW; silicotungstic acid H; ₄; SiW; ₁₂; O; ₄₀; G; glycerol; Cs; _2.5; SiW; cesium salt Cs; _2.5; H; _1.5; SiW; ₁₂; O; ₄₀; DIB; diisobutylene (mixture of 2,4,4-trimethyl-1- and 2,4,4-trimethyl-2-pentenes); IL-6; 1-(4-sulfobutyl)-3-hexylimidazolium trifluoromethanesulfonate; GTBE; glycerol tert-butyl ethers; TsOH; para-toluenesulfonic acid; MTBGE; mono-tert-butyl glycerol ether; TBA; tert-butyl alcohol; DTBGE; di-tert-butyl glycerol ether; Na(50)Amb; 50% ion-exchanged Amberlyst-15 sodium form; TTBGE; tri-tert-butyl glycerol ether; H-Amb; acidic form of Amberlyst-15Etherification; tert-Butylation; Isobutylene; Glycerol; Ion-exchange resin; Amberlyst; Partial neutralization; p; -Toluenesulfonic acid; Heteropolyacid; Silicotungstic acid cesium salt; Ionic liquid; Pulse chemisorption

Etherification of glycerol by isobutylene: Tuning the product composition by Hee Jong Lee; Doyoung Seung; Kwang S. Jung; Hwayong Kim; Igor N. Filimonov (pp. 235-244).

Role of support on the photocatalytic activity of titanium oxide by R. Sasikala; A.R. Shirole; V. Sudarsan; V.S. Kamble; C. Sudakar; R. Naik; R. Rao; S.R. Bharadwaj (pp. 245-252).

Display Omitted▶ Photocatalytic activity of TiO₂ gets altered when it is supported on various oxides. ▶ Improved optical absorption is observed for TiO₂-ZrO₂, TiO₂-zeolite and TiO₂-CeO₂. ▶ Photocatalytic activity of TiO₂ shows a strong dependence on the acidity of support. ▶ Life time of the charge carriers in supported TiO₂ is different from pristine TiO₂. ▶ Surface acidic sites enhance the charge separation leading to enhanced activity.We demonstrate an enhanced photocatalytic activity for TiO₂ when it is dispersed on ZrO₂ and zeolite compared to that dispersed on Al₂O₃ and CeO₂. In these composite systems, TiO₂ exists as a dispersed particulate phase and the extent of dispersion is the highest on ZrO₂ support. Na–Y zeolite possesses the maximum Lewis acidity followed by ZrO₂, Al₂O₃ and CeO₂. Optical absorption property of TiO₂ dispersed on ZrO₂, zeolite and CeO₂ is better than that of unsupported TiO₂. In the above mentioned systems, photocatalytic activity of TiO₂ shows a strong dependence on the surface acidity of the support. A significantly high photocatalytic activity for hydrogen generation from water–methanol mixture is observed for the TiO₂–ZrO₂ system. The enhanced activity of TiO₂ dispersed on ZrO₂ is attributed to the enhanced optical absorption and increased life time of the photogenerated charge carriers assisted by the surface acidic sites. Present study leads to a new result that a highly dispersed phase of TiO₂ on a support having higher surface acidity exhibits enhanced photocatalytic activity. This strategy may be useful for the design of new catalysts yielding high photocatalytic activity. Presence of a co-catalyst like Pd metal enhances the photocatalytic activity further.

Keywords: Photocatalysis; Titanium oxide; Support; Hydrogen; Surface acidity

Role of support on the photocatalytic activity of titanium oxide by R. Sasikala; A.R. Shirole; V. Sudarsan; V.S. Kamble; C. Sudakar; R. Naik; R. Rao; S.R. Bharadwaj (pp. 245-252).

Keywords: Photocatalysis; Titanium oxide; Support; Hydrogen; Surface acidity

Ni₂P and CoP catalysts prepared from phosphite-type precursors for HDS–HDN competitive reactions by A. Infantes-Molina; J.A. Cecilia; B. Pawelec; J.L.G. Fierro; E. Rodríguez-Castellón; A. Jiménez-López (pp. 253-263).

Display Omitted▶ Ni₂P catalyst shows a higher activity than CoP one in the HDS and HDN reaction. ▶ The catalytic activity and stability is higher in the HDS reaction than in the HDN one. ▶ The competitive HDS–HDN reactions reveal that Ni₂P catalyst is highly active. ▶ N-removal is affected by the presence of sulfur containing molecules. ▶ HDN and HDS reaction must occur on different sites.Silica-supported nickel and cobalt phosphide catalysts were synthesized with low metal-loading (5wt%). The formation of Ni₂P and CoP phases was achieved by temperature-programmed reduction of phosphite-based precursors, Ni(HPO₃H)₂ and Co(HPO₃H)₂, respectively. The catalysts were characterized by X-ray fluorescence (XRFS), N₂ adsorption–desorption, X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and elemental analysis (CNHS). These catalysts were tested in the individual reactions of hydrodesulfurization (HDS) of dibenzothiophene (DBT) and hydrodenitrogenation (HDN) of quinoline (Q), and also in the simultaneous HDS and HDN reactions. These tests were conducted by feeding 3000ppm of DBT or 3000ppm of Q. Additional tests were performed with the aim to evaluate S-removal capability by keeping constant Q concentration in the feed (3000ppm) and varying DBT concentration (200 and 2000ppm). The catalytic results show that these phosphide catalysts achieve high DBT and Q conversion values at high temperatures though the rate of HDS reaction is higher than that of HDN. In all cases Ni₂P is more active than CoP. Moreover, the presence of N-containing molecules in the feed does not affect the S-removal as sulfur is almost completely removed after 48h on-stream.

Keywords: Commercial silica; Nickel phosphide (Ni; ₂; P); Cobalt phosphide (CoP); Dibenzothiophene; HDS; Quinoline; HDN

Dehydrogenation of propane over Pt/KL catalyst: Investigating the role of L-zeolite structure on catalyst performance using isotope labeling by Khalid G. Azzam; Gary Jacobs; Wilson D. Shafer; Burtron H. Davis (pp. 264-270).

Display Omitted▶ An NKIE exists during propane (H and D labeled) dehydrogenation over Pt/KL. ▶ Catalyst deactivation occurred from carbon deposition due to bimolecular reactions. ▶ The unique structure of Pt/KL did not enhance performance with C₃ as with C₆.Dehydrogenation of propane using an equimolar mixture of propane- d₀ and propane- d₈ was investigated over 1%Pt/KL and 1%Pt/SiO₂ at atmospheric pressure and different reaction temperatures. A normal kinetic isotope effect exists ( k_H/ k_D=1.4–1.5) when the reaction is conducted on Pt/KL at different temperatures (400, 500, and 600°C), suggesting that C–H bond activation is involved in the kinetically relevant steps. Furtheremore, there is hardly any H–D exchange in the recovered propane during dehydrogenation at temperatures above 400°C, suggesting that adsorption and subsequent dehydrogenation of propane are essentially irreversible and that C–H bond activation is the rate determining step. Unlike the case of hexane aromatization, the unique structure of L-zeolite does not help in controlling the entry of propane molecules into the lobes of the L-zeolite containing the active sites; hence, bimolecular reactions do occur, leading to coke formation and catalyst deactivation.

Keywords: Dehydrogenation; Propane; C; ₃; H; ₈; C; ₃; D; ₈; Pt/KL; L-zeolite; Isotope effect; Diffusion; H–D exchange

Characterization and activity of perovskite catalysts for autothermal reforming of dodecane by Rajender R. Kondakindi; Arunabha Kundu; Kunal Karan; Brant A. Peppley; Aidu Qi; Chris Thurgood; Pier Schurer (pp. 271-280).

.Display Omitted▶ The LaFeO₃-based perovskite catalysts were prepared by the glycine-nitrate process. ▶ The Pd-doped perovskite resulted in 100% conversion at 750°C at a GHSV of 132000h⁻¹. ▶ The yield of H₂ for La_0.95Ce_0.05Fe_0.77Co_0.17Pd_0.06O₃ was the highest (∼25) at 850°C. ▶ The La_0.95Ce_0.05Fe_0.77Co_0.17Pd_0.06O₃ resulted in higher conversion and selectivity to H₂ compared to that of Pd/laFe_0.8Co_0.2O₃.In this study, LaFeO₃-based perovskites prepared by the glycine-nitrate process (GNP) were investigated as potential candidates for diesel surrogate, dodecane, reforming to generate hydrogen-rich reformate. The perovskites were characterized by various techniques such as X-ray diffraction (XRD), transmission electron microscopy (TEM), temperature-programmed reduction (TPR) and Mossbauer spectroscopy. The catalytic experiments were conducted over a range of operating conditions by varying space velocity, steam-to-carbon ratios, oxygen-to-carbon ratios and temperatures. LaFeO₃ perovskite modified at the B-site with Co exhibited improved performance in terms of higher conversion and H₂ yield compared to LaFeO₃ catalyst. Further modification of the LaFeO₃ perovskite with Pd at the B-site showed improved performance to that of Co-doped LaFeO₃. Among all modifications of LaFeO₃ catalysts investigated, the effect of substituting Ce for La at the A-site and Co/Pd at the B-site yielded the best performance in terms of conversion at lower operating temperature, higher yield of hydrogen and lower amounts of other products (CH₄ and ethylene).

Keywords: Perovskite; XRD; TPR; TEM; Mossbauer spectroscopy; Dodecane; Autothermal reforming

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Applied Catalysis A, General (v.390, #1-2)