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Applied Catalysis A, General (v.445-446, #)

Contents (pp. iii-xiv).

Editorial Board (pp. co2).

Heats of adsorption of linearly adsorbed CO species on Co²⁺ and Co° sites of reduced Co/Al₂O₃ catalysts in relationship with the CO/H₂ reaction by Julien Couble; Daniel Bianchi (pp. 1-13).

Display Omitted► Adsorption equilibrium infrared spectroscopy method. ► Heats of adsorption of linear CO species on reduced Co/Al₂O₃ solids. ► Impacts of C_ads species formed by the CO disproportionation. ► Impacts of the H₂/CO ratio.IR spectra in transmission mode are used to measure the heats of adsorption at different coverages θ: E( θ), of two linearly adsorbed CO species formed on Co²⁺ and Co° sites (notedLCo2+ and L_Co°) of reduced x% Co/Al₂O₃ (wt%, x≤10) catalysts according to the adsorption equilibrium infrared spectroscopy procedure developed previously. ForLCo2+ species characterized by an IR band at 2151cm⁻¹,ELCo2+(θ) varies linearly with θ fromELCo2+(1)=45kJ/mol toELCo2+(0)=52kJ/mol. These values are modified by the presence of neither Co° particles nor carbon deposition (from CO disproportionation reaction) nor H₂ using CO/H₂ gas mixtures. During the CO adsorption at high temperatures (i.e. 538K), C deposition on the surface and in the bulk of the cobalt particles modifies the Co° adsorption sites. This leads to a transformation L_Co° (IR band at 2020cm⁻¹)→L_Co°C (IR band at 2060cm⁻¹) where L_Co°C denotes a linear CO species formed on Co° sites modified by the C deposition. The heat of adsorption of the L_Co°C species varies linearly with its coverage fromELCo°C(1)=93kJ/mol toELCo°C(0)=165kJ/mol. In the presence of H₂ with a ratio H₂/CO=10, the C deposition is strongly decreased and the L_Co° species dominates the surface of the cobalt particles. However, in these conditions its hydrogenation into CH₄ disturbs its adsorption equilibrium in a large coverage range and onlyELCo°(1)=108kJ/mol has been determined. For a ratio H₂/CO=3, the carbon deposition cannot be prevented leading to the formation of the L_Co°C species. It is shown that theELCo°C(θ) values are not modified by the presence of adsorbed hydrogen. The heats of adsorption of the different adsorbed CO species on Co° sites are consistent with some literature data on DFT calculations and experimental values obtained on model cobalt surfaces (i.e. single crystals). In particular, they confirm DFT calculations which indicate that the C deposition on reduced cobalt particles decreases slightly the heats of adsorption of the linear CO species adsorbed on Co° sites.

Keywords: FTIR; AEIR method; CO adsorption; Cobalt catalysts; Heats of adsorption; Carbon deposition; CO/H; ₂; reaction

Citral hydrogenation on high surface area mesoporous TiO₂–SiO₂ supported Pt nanocomposites: Effect of titanium loading and reduction temperature on the catalytic performances by Mourad Bidaoui; Catherine Especel; Naïma Bouchenafa-Saib; Daniel Duprez; Ourida Mohammedi; Sébastien Royer (pp. 14-25).

Display Omitted► Pt-based catalysts supported on TiO₂-modified mesostructured silica were prepared. ► Direct co-condensation of silica and titania precursors was used for the synthesis. ► Mixed oxides present very particular morphology with high surface areas. ► Unsaturated alcohol selectivity: Pt/Ti-SBA15≫Pt/SBA15∼Pt/TiO₂ P25 (reduction 300°C). ► On Pt/Ti-SBA15, nano-anatase particles favor a strong metal–support interaction with Pt.Platinum-based catalysts supported on TiO₂-modified mesostructured silica were prepared using the direct co-condensation of silica and titania precursors to synthesize the mixed-oxide support. The physico-chemical properties of the Pt/ xTi-SBA15 samples with various xTi contents (in mol%) were further evaluated using several techniques, including elemental analysis, X-ray diffraction, N₂-physisorption, H₂-chemisorption, transmission electronic microscopy and the probe reaction of cyclohexane dehydrogenation to evaluate the metal–support interaction (SMSI effect). All the Pt/ xTi-SBA15 samples display high specific surface areas (650–820 m²g⁻¹) and high mesopore volumes (0.44–0.68cm³g⁻¹), with the formation of TiO₂ anatase nanoparticles since the low titanium content, i.e. 2mol%. The hexagonal organized pore structure of SBA silica is also strongly altered by the titanium adding, but mixed oxides so obtained present very particular morphology with maintaining of high surface areas.The catalytic performances of the Pt/ xTi-SBA15 catalysts were estimated for the citral hydrogenation performed at 70°C under hydrogen pressure (7MPa), and discussed in terms of activity and unsaturated alcohols (UA: nerol and geraniol) selectivity. A synergetic effect on the UA selectivity was obtained on the Pt/ xTi-SBA15 catalysts, compared to both Pt/SBA15 and Pt/TiO₂ P25 reference samples (reduction temperature=300°C), and was explained by the specific role of the reducible TiO₂ species, which under the nano-anatase form generate a strong metal–support interaction (SMSI effect) with platinum after reduction at 300°C. The formation of partially reduced support species was finally modulated by varying the reduction temperature of the catalysts. It is then possible to achieve high selectivity after reduction at 350°C, while maintaining high conversions.

Keywords: Titania; Silica; Platinum; Mesoporous materials; Citral hydrogenation; Nanocomposites

Microkinetic modeling of the hydrogenation of nitrate in water on Pd–Sn/Al₂O₃ catalyst by Adagneves O. Costa; Luciana S. Ferreira; Fabio B. Passos; Mônica P. Maia; Fernando C. Peixoto (pp. 26-34).

Display Omitted► Microkinetic model for nitrate hydrogenation in water on Pd–Sn/Al₂O₃ catalyst. ► The kinetic model showed good adherence to experimental data. ► Coverage of active sites was followed along reaction time.An alumina supported palladium–tin catalyst was investigated in the nitrate catalytic hydrogenation in water and was active and selective for the reaction. A reaction mechanism was proposed using a microkinetic model without assuming the rate-determining step of the process. Kinetics measurements were performed in a semi-batch reactor varying the temperature in a range 278–318K. A statistical fit was achieved with concentration data, obtained from the microkinetic modeling and the experimental practice, providing satisfactory statistical variance.

Keywords: Pd–Sn/Al; ₂; O; ₃; Nitrate reduction; Microkinetic modeling

Autothermal reforming of butanol to butenes in a staged millisecond reactor: Effect of catalysts and isomers by Hui Sun; Samuel Blass; Edward Michor; Lanny Schmidt (pp. 35-41).

Display Omitted► Dehydration/isomerization of butanol to butene in an autothermal staged reactor (∼95% yield). ► Integration of exothermic and endothermic chemistry to maintain adequate bed temperature. ► The effect of catalyst is studied by comparing H-ZSM5, H-FER and γ-Al₂O₃. ► The effect of butanol isomers is explored by feeding 4 different isomers.Dehydration and isomerization of butanol is studied in an autothermal short contact-time reactor containing a 1wt% Pt stage followed by a zeolite or γ-Al₂O₃ stage downstream to convert butanol into butenes with up to 95% yield at residence times on the order of 100ms. CH₄ is fed as a sacrificial fuel to the Pt stage and butanol is fed between the stages to avoid undesired oxidation and reforming reactions of butanol over Pt. The energy released by CH₄ catalytic partial oxidation drives downstream butanol dehydration and isomerization.The effect of catalyst is studied by comparing the performance of HZSM-5, HFER, and γ-Al₂O₃ catalysts. Higher yields (20%) of butenes were obtained with γ-Al₂O₃ and HFER than with HZSM-5. The absence of Br∅nsted acid sites in γ-Al₂O₃ and the small pore structure of HFER lead to reduced yields of large side products such as higher hydrocarbons that promote oligomerization reactions. A 95% butene yield is obtained with HFER at temperatures ranging from 280–350°C and a 95% yield with γ-Al₂O₃ at temperatures between 320 and 350°C. Only a 75% butene yield was obtained with HZSM-5 at 230°C.The effect of hydrocarbon structure on product formation is studied by comparing conversions of each butanol isomer using a heated tube reactor at temperatures between 200 and 400°C. The reactivity of butanol follows as: t-butanol>2-butanol>iso-butanol>1-butanol. trans-2-Butene and cis-2-butene are primarily formed from linear butanol isomers, while isobutene forms from branched butanol isomers. Conversions and product distributions of butanol isomers formed over HZSM-5 in a staged reactor are comparable (<10% difference across all species) with data using a heated tube reactor at similar temperatures.We successfully demonstrate an alternative pathway to dehydrate butanol into butenes with an autothermal staged reactor compared to conventional methods for applications in small-scale biomass utilization. The largest advantage of this reactor is the integration of highly exothermic autothermal stage and endothermic alcohol dehydration stage which provides an alternative processing technique to maintain the bed temperature.

Keywords: Biomass; Butanol; Butene isomers; Dehydration; Isomerization; Autothermal

Development of an efficient catalyst from magnetite ore: Characterization and catalytic potential in the ozonation of water toxic contaminants by Gholamreza Moussavi; Rasoul Khosravi; Nematollah Rashidnejad Omran (pp. 42-49).

Display Omitted► The work is the first to demonstrate the preparation of the calcined magnetite from magnetite ore. ► The calcined magnetite was very active in catalyzing the ozonation of the reactive azo dyes. ► The ozonation with calcined magnetite achieved a mineralization degree much greater than does single ozonation. ► The calcined magnetite powder could be efficiently reused and thus is a stable catalyst.This study presents the preparation, characterization and activity of a novel natural mineral-based catalyst for the ozonation of water recalcitrant compounds. The raw and calcined magnetite had the specific surface area of 27m²/g and 34m²/g, respectively. The effects of solution pH, catalyst dose, model dye concentration, and reaction time on the degradation and mineralization of a selected reactive azo dye viz. Reactive Red-120 (RR-120) were evaluated. Calcined magnetite attained greater catalytic potential than the raw ore in the degradation of RR-120. Oxidation via radical species on the surface of the catalyst was the main mechanism of RR-120 degradation in the developed catalytic ozonation process, occurring with a pseudo-first-order reaction rate at a constant of 0.082min⁻¹ under the optimum pH of 11 and catalyst dose of 3g/L. Accordingly, considering its abundance in nature together with its very high catalytic potential, calcined magnetite is a promising and reliable catalytic material for the ozonation of inhibitory and recalcitrant compounds in water and wastewater.

Keywords: Toxic compounds; Reactive dyes; Ozonation; Catalyst; Degradation

Comprehensive kinetic study for pyridine hydrodenitrogenation on (Ni)WP/SiO₂ catalysts by Jan Kopyscinski; Jinsoon Choi; Josephine M. Hill (pp. 50-60).

Display Omitted► Adding Ni to WP/SiO₂ increases pyridine conversion and pentane yields. ► Adding Ni to WP/SiO₂ does not change the HDN reaction mechanism. ► Hydrogenation and CN bond cleavage reactions occur on different active sites. ► Adding Ni to WP/SiO₂ does change the type of adsorbed species on both sites.In this work the reaction kinetics for pyridine hydrodenitrogenation on (Ni)WP/SiO₂ catalysts were determined. The experiments were conducted at 17.2bar and between 573K and 633K for various flow rates of hydrogen and pyridine. Adding Ni to the WP/SiO₂ catalyst enhanced the hydrogenation reaction and gave higher pentane and pentylamine yields. A trend in terms of selectivity was not evident on either catalyst. The results were fit to several models and a Bayesian approach was applied for parameter estimation and model discrimination. Adding Ni to the WP/SiO₂ catalyst did not change the reaction mechanism – both catalysts favor the same Langmuir–Hinshelwood model with different active sites for hydrogenation and CN bond cleavage. Ni did, however, influence the type of adsorbed species, the heat of adsorption and the activation energies.

Keywords: Pyridine hydrodenitrogenation; HDN; Bayesian parameter estimation; Kinetic study; WP/SiO; ₂; NiWP/SiO; ₂

Synthesis gas production to desired hydrogen to carbon monoxide ratios by tri-reforming of methane using Ni–MgO–(Ce,Zr)O₂ catalysts by Devin M. Walker; Sandra L. Pettit; John T. Wolan; John N. Kuhn (pp. 61-68).

Display Omitted► Ni–MgO–(Ce,Zr)O₂ catalysts optimized for tri-reforming. ► Ni:Mg and Ce:Zr ratios important to limit coking. ► Ideal formulation was Ce_0.6Zr_0.4O₂–8Ni8Mg prepared by wet impregnation. ► Optimized gas feed ratios were CH₄:CO₂:H₂O:O₂=1:0.7:0.5:0.2. ► Hydrogen-to-carbon monoxide ratio increased with space velocity.This paper highlights the performance of Ni–MgO–(Ce,Zr)O₂ tri-reforming catalysts under various reaction conditions and explains results using catalyst characterization. Testing under controlled reaction conditions and the use of several catalyst characterization techniques (BET, XRD, TPR, SEM-EDS, and XPS) were employed to better explain the effects of the synthesis parameters on the reaction performances. The support Ce:Zr ratio, metal loading techniques, metal wt%, and Ni:Mg ratios all had a pronounced influence on the catalyst performance. An even ratio of Ce:Zr for the support and an even ratio of Ni:Mg gave the best performance. The wet impregnation method consistently showed more resistance to coke formation when compared to the deposition precipitation method, but the difference was attributed to a better ability to load Mg by wet impregnation. Lower than previously reported H₂O concentrations in the feed gas composition also led to desired H₂:CO ratios needed for FT synthesis while maintaining high conversions of CO₂ and resistance to coke formation. High GHSV (61,000h⁻¹) yielded significantly higher H₂:CO ratios when compared to reactions run at lower GHSV (25,000h⁻¹). These results suggest that steam reforming reactions are kept further from equilibrium at higher GHSV and result in higher H₂ production. The tested tri-reforming catalyst produced desired H₂:CO ratios with minimal deactivation, high reactant conversions, and extended catalyst lifetime.

Keywords: Gas-to-liquid; Fischer Tropsch synthesis; Energy; Biofuel; Hydrogen production

Hydrogenation of nitriles to primary amines on metal-supported catalysts: Highly selective conversion of butyronitrile to n-butylamine by D.J. Segobia; A.F. Trasarti; C.R. Apesteguía (pp. 69-75).

Display Omitted► Co/SiO₂ and Ni/SiO₂ selectively hydrogenate butyronitrile to n-butylamine. ► Ni/SiO₂ is the most active catalyst for converting butyronitrile to n-butylamine. ► Co/SiO₂ is the most selective catalyst for converting butyronitrile to n-butylamine. ► Co/SiO₂ yields 97% of n-butylamine from butyronitrile hydrogenation.The selective liquid-phase hydrogenation of butyronitrile to n-butylamine was studied in a batch reactor on Co(9.8%)/SiO₂, Ni(10.5%)/SiO₂, Cu(9.2%)/SiO₂, Pt(0.27%)/SiO₂, Pd(0.33%)/SiO₂, and Ru(1.8%)/SiO₂ catalysts. At 373K and 13bar (H₂), the initial butyronitrile conversion rate (rBN0, mmol/hg) followed the order Ni>Co>Pt>Ru>Cu>Pd. Cu/SiO₂ and Pd/SiO₂ did not form n-butylamine and rapidly deactivated during the progress of the reaction. Pt/SiO₂ produced mainly dibutylamine and only minor amounts of n-butylamine and tributylamine. In contrast, Ru/SiO₂ formed preponderantly n-butylamine but also produced significant amounts of dibutylamine and butylidene–butylamine, an intermediate in the formation pathway of the secondary amine. The highest yield to n-butylamine was obtained on Ni/SiO₂ (84%). Co/SiO₂ was initially highly selective to n-butylamine but with the progress of the reaction the butylamine concentration in the reaction mixture diminished because it partially reacted with the solvent (ethanol) to form N-ethylbutylamine. In an attempt to reduce the formation of byproducts, Ni/SiO₂ and Co/SiO₂ catalysts were tested at lower temperatures and higher H₂ pressures. Butyronitrile was selectively converted to n-butylamine on Co/SiO₂ at 343K and 25bar, yielding 97% of n-butylamine, similarly to the highest yields reported on Raney Co catalysts.

Keywords: Butyronitrile hydrogenation; Selective hydrogenation; Primary amines; Metal-supported catalysts

Strontium zirconate heterogeneous catalyst for biodiesel production: Synthesis, characterization and catalytic activity evaluation by José Renato de Oliveira Lima; Yussra Abdul Ghani; Rondenelly B. da Silva; Francisco Marcos C. Batista; Rafael Admar Bini; Laudemir Carlos Varanda; José Eduardo de Oliveira (pp. 76-82).

Display Omitted► Heterogeneous biodiesel catalysts based on Sr and Zr were synthesized. ► Co-precipitation and citrate route were evaluated in synthesis of SrZrO₃ matrix. ► Synthesized catalyst properties were studied upon XDR, TG and IR. ► SrZrO₃ (SZCRA) matrix has showed catalytic activity providing 98% of ester content. ► Employed heterogeneous reaction conditions were similar to those which using NaOH.Strontium zirconate oxide was synthesized by co-precipitation and the citrate route and was evaluated as a heterogeneous catalyst for biodiesel production. The catalyst samples were characterized by XRD, FTIR, and TG, and catalytic activity was measured based on the ester content of the biodiesel produced that was quantified by GC. The co-precipitate samples were obtained in alkaline pH and had a mixture of the perovskite and pure strontium and zirconium oxide phases. Ester conversion using these samples was approximately 1.6%, indicating no catalytic activity. The citrate route was more efficient in producing perovskite when carried out at pH 7–8; excess SrCO₃ was found on the catalyst surface due to CO₂ adsorption, thus demonstrating no catalytic activity. The same synthesis carried out at pH 2 resulted in free OH⁻ groups, with a small amount of the carbonate species that produced ester yield values of 98%. Therefore, matrices based on strontium zirconate produced via the citrate route in acidic media are potential heterogeneous catalysts for transesterification.

Keywords: Strontium zirconate; Citrate route; Heterogeneous catalyst; Biodiesel

Washcoated Pd/Al₂O₃ monoliths for the liquid phase hydrodechlorination of dioxins by Martha Cobo; Andrés Orrego; Juan A. Conesa (pp. 83-91).

Display Omitted► Pd/Al₂O₃ washcoated monoliths were tested on liquid phase HDC of dioxins. ► Slurry and monolith reactors, and bubble loop column configurations were compared. ► The monoliths were active and more resistant to deactivation. ► The spent monoliths were regenerated by washing, oxidation/reduction, and reduction.The catalytic activity and durability of 2wt.% Pd/Al₂O₃ in powder and washcoated on cordierite monoliths were examined for the liquid phase hydrodechlorination (LPHDC) of polychlorinated dibenzo-p-dioxins/polychlorinated dibenzofurans (PCDD/Fs), also known as dioxins. NaOH was employed as a neutralizing agent, and 2-propanol was used as a hydrogen donor and a solvent. Fresh and spent powder and monolith samples were characterized by elemental analysis, surface area, hydrogen chemisorption, scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDX), and transmission electron microscopy/energy dispersive X-ray spectroscopy (TEM/EDX). Three reactor configurations were compared including the slurry and monolith batch reactors as well as the bubble loop column resulting in 100, 70, and 72% sample toxicity reduction, respectively, after 5h of reaction. However, the slurry and monolith batch reactors lead to catalyst sample loss via a filtration process (slurry) and washcoat erosion (monolith batch), as well as rapid deactivation of the powder catalyst samples. The monolith employed in the bubble loop column remained stable and active after four reaction runs. Three preemptive regeneration methods were evaluated on spent monolith catalyst including 2-propanol washing, oxidation/reduction, and reduction. All three procedures reactivated the spent catalyst samples, but the combustion methods proved to be more efficient at eliminating the more stable poisons.

Keywords: Pd/Al; ₂; O; ₃; catalyst; Washcoated monoliths; Catalyst deactivation; Dioxins; Fly ash

Supported ionic liquids on non-porous and porous inorganic materials—A topical review by Thangaraj Selvam; Albert Machoke; Wilhelm Schwieger (pp. 92-101).

.Display Omitted► Non-porous and porous inorganic supports. ► Immobilization of ionic liquids (ILs). ► Concepts emerging from supported ionic liquids (SILs). ► Layered silicates, porous glass, and zeolites. ► Mesoporous (MCM) and periodic mesoporous organosilica (PMO) materials.A topical review of the use of non-porous and porous inorganic materials as supports for the immobilization of ILs and their catalytic applications is given. The basic principles and the supports that are being used in various concepts emerging from supported ionic liquids (SILs) including supported ionic liquid films (SILFs), supported ionic liquid catalysis/catalysts (SILC/SILCAs), solid catalysts with ILs (SCILs), solid catalysts with IL layer (SCILL), supported IL nanoparticles (SILnPs) and supported ionic liquid phase (SILP) catalysts (SILPC) are first discussed. In addition, we provide a comprehensive review of the SILs concept dealing with inorganic supports, such as layered silicates, porous glass, zeolites, mesoporous (MCM) and PMO (periodic mesoporous organosilica) materials; and their applications.

Keywords: Ionic liquids; Supported ionic liquids; Inorganic supports; Non-porous and porous materials

Liquid- and vapor-phase hydrogenation of 1-epoxy-3-butene using self-assembled monolayer coated palladium and platinum catalysts by Karl R. Kahsar; Daniel K. Schwartz; J. Will Medlin (pp. 102-106).

Display Omitted► Thiol SAM coatings alter selectivity on supported Pt and Pd catalysts. ► Thiol SAMs can be used to enhance liquid phase hydrogenation selectivity. ► Solvent–SAM interactions have a strong effect on selectivity. ► More crystalline SAMs are associated with higher catalyst activity.Alkanethiol self-assembled monolayers (SAMs) have recently been shown to be effective catalyst modifiers for increasing the selectivity of the hydrogenation of 1-epoxy-3-butene (EpB) to 1-epoxybutane in the gas phase. In the results reported here, we demonstrate that SAM coatings can similarly be applied to other supported metals (Pt) and in liquid-phase reaction environments. Coating a Pt/Al₂O₃ catalyst with n-octadecanethiol resulted in a large improvement in selectivity during vapor-phase EpB hydrogenation, similar to that observed for supported Pd. The liquid phase hydrogenation of EpB using SAM-coated catalysts showed similar selectivity trends in some cases, but interactions of the solvent with the SAM were also important in controlling selectivity. In particular, using a heptane solvent, epoxybutane selectivity increased from 36% with an uncoated Pd/Al₂O₃ catalyst to 74% with a thioglycerol SAM-coated catalyst. SAM quality was shown to have a strong impact on the rate of reaction but little effect on selectivity. The results generally indicated that selectivity modification with thiol SAMs is extendable to other supported metals and a variety of reaction environments.

Keywords: Selective hydrogenation; Alkanethiols; Surface modification; Supported metal catalysts

Kinetics and reactor modeling of a Pd-Ag/Al₂O₃ catalyst during selective hydrogenation of ethyne by Axel Pachulski; Rainer Schödel; Peter Claus (pp. 107-120).

Display Omitted► Kinetic study with an industrial Pd-Ag/Al₂O₃ catalyst for selective acetylene hydrogenation. ► Integral fixed bed reactor at different process conditions. ► Successful application of modeling results to the industrial reactor.The selective hydrogenation of ethyne is one process to remove traces of ethyne from steam cracker cuts during the production of ethene. Even though Pd-Ag/Al₂O₃ catalysts are predominantly used in industrial C₂-tail end-selective hydrogenation reactors, a detailed kinetic study with this catalyst type has not yet been published in the open literature. For this reason, kinetic measurements were carried out on a Pd-Ag/Al₂O₃ catalyst in an integral fixed bed reactor at different process conditions for the selective hydrogenation of ethyne. The results of these measurements were fitted on different kinetic models ranging from a classical Hougen–Watson, Langmuir–Hinshelwood and Rideal–Eley approach up to simple power law equations. The kinetic model with the best fit was found by statistical and thermodynamical evaluations of all models and their respective kinetic parameters. This model is based on a Langmuir–Hinshelwood reaction mechanism involving two different active sites for the hydrogenation of ethyne and ethene. The kinetic measurements were not dependent on mass and heat transfer as demonstrated by using the criteria from Mears and the Weisz–Prater as well as for the Damkoehler numbers in 3rd and 4th order. Finally the performance of a bypass reactor, running in parallel to an industrial C₂-tail end-selective hydrogenation reactor, was successfully calculated with a reactor model.

Keywords: Ethyne hydrogenation; Ethene; Ethane; Palladium; Silver; Alumina; Kinetic; Mass and heat transfer; Thermodynamic consistency

Catalytic growth of high quality single-walled carbon nanotubes over a Fe/MgO catalyst derived from a precursor containing Feitknecht compound by Yi Jin; Gaowei Wang; Yongdan Li (pp. 121-127).

Display Omitted► A precursor containing Feitknecht compound was prepared via a varied pH co-precipitation method. ► High quality SWCNTs were obtained over the catalyst derived from Feitknecht compound. ► Rinsing the precipitates with ethanol improves the yield of the SWCNTs. ► The metal–support interaction affects the diameter distribution of SWCNTs.A catalyst is derived from a Feitknecht-compound (FC) precursor prepared via a co-precipitation method and is proved to manifest a strong metal–support interaction which facilitates the growth of high quality single-walled carbon nanotubes (SWCNTs) with a narrow diameter distribution. The effect of the rinsing condition of the precipitate on the growth of the SWCNTs is also examined. The pore structure of the catalysts rinsed by ethanol is modified and the carbon yield is enhanced while the diameter distribution of the SWCNTs is unchanged. The correlation between the metal–support interaction and the SWCNT growth is discussed.

Keywords: Methane catalytic decomposition; Single-walled carbon nanotubes; FC compound; High quality carbon nanotubes; Metal–support interaction

Organic amine grafting on mesoporous silica as a hybrid catalyst for heterogeneous three-component one-pot reaction by Kenichi Komura; Yuta Mishima; Mamoru Koketsu (pp. 128-132).

Display Omitted► Heterogeneous multi-component reaction. ► Organic amine grafting on mesoporous silica is a hybrid catalyst. ► The complex molecule can be obtained in one-pot manner.The organic–inorganic hybrid catalyst was prepared by immobilizing 3-methylaminopropyl moiety onto mesoporous silica, MCM-41, and applied for solid base catalyst of three-component one-pot reaction, i.e. Knoevenagel condensation of aldehyde with the active methylene compound to yield an electron deficient alkene which is subjective to be reacted with nitromethane by Michael addition to form tri-substituted primary nitro compound. The catalyst was characterized by powder-XRD, TG–DTA, FT-IR, nitrogen adsorption–desorption measurement and solid-state cross polarization magic angle spinning (CP/MAS) NMR, and exhibited high catalytic activity in three-component one-pot reaction; however, with poor reusability.

Keywords: Mesoporous silica; MCM-41; Three-component reaction; One-pot reaction; Solid base catalyst

Effect of precious metals and NOx storage materials on hydrogen reduction of stored NOx on millisecond time scale by Y. Sakamoto; S. Matsunaga; K. Okumura; T. Kayama; K. Yamazaki; N. Takahashi; T. Tanaka; Y. Kizaki; T. Motohiro; H. Shinjoh (pp. 133-142).

Display Omitted► High speed transient reaction analysis with submillisecond resolution. ► Effect of precious metals (Pt,Rh,Pd) and NOx storage materials (Ba,K,Na) was investigated on a regeneration reaction of stored NOx. ► This figure shows the case of Pt/Ba/Al₂O₃ catalyst.The effect of precious metals (PMs) and NOx storage materials (NSMs) on the reduction of stored NOx over PM/NSM/Al₂O₃ (PM=Pt, Rh, Pd; NSM=Ba, K, Na) catalysts was studied via transient reaction analysis using pulsed gases with submillisecond resolution. The time profiles of the product gases were analyzed with a high time resolution of 0.25ms for the first 50ms after supplying a hydrogen gas pulse.These results were explained with a model that correlates with the spillovers of released NOx species from the NSM and the activated hydrogen on the PM. The catalyst Pt/Na/Al₂O₃ had the highest reduction rate of stored NOx among the nine catalysts examined. This performance is due to both the lowest decomposition temperature of Na and the high reactivity of hydrogen on Pt. On the other hand, the Rh-containing catalysts exhibited a lower NH₃ production capability than the Pt- and Pd-containing catalysts, and the Rh/K/Al₂O₃ catalyst had the least NH₃ production capability and the lowest reduction rate of stored NOx. The lower NH₃ production capability of Rh is caused both by the low hydrogen reactivity on Rh and the lowest reduction rate of stored NOx for Rh/K/Al₂O₃, which has the lowest surface area among the Rh-containing catalysts.

Keywords: Time-of-flight mass spectrometry; Lean-burn engine; NOx storage-reduction catalyst; Platinum; Rhodium; Palladium; Barium; Potassium; Sodium

High conductivity catalyst structures for applications in exothermic reactions by Min Sheng; Hongyun Yang; Donald R. Cahela; William R. Yantz Jr.; Carlos F. Gonzalez; Bruce J. Tatarchuk (pp. 143-152).

Display Omitted► We determined the overall heat transfer coefficient for PB and MFEC. ► We examined the performances of these two catalyst structures in FTS. ► The enhanced heat transfer property of MFEC improved the thermal severity of FTS. ► Uniform temperature profile in MFEC resulted in slow catalyst deactivation. ► It also improved the heavy product selectivity.Highly exothermic catalytic reactions are problematic from a thermal management perspective and often dictate the type of reactor, heat exchanger, level of conversion/recycle and contacting scheme that are employed. To investigate the opportunity for enhanced heat transfer structures, 15wt% Co/Al₂O₃ catalyst particles (149–177μm dia.) were examined in both a packed bed configuration and after being entrapped within a 7.4vol.% network of sintered Cu fibers (12μm dia.). Fischer–Tropsch synthesis (FTS) at 225–255°C, 20bar, H₂/CO of 2.0, was utilized as the probe reaction due to its exothermicity and temperature dependent selectivity. Both the hot spot and runaway state were prevented by utilizing metal microfibrous entrapped catalyst (MFEC) compared to the packed bed. In a 41mm ID reactor, the maximum temperature deviation from the centerline to the reactor wall was only 6.4°C for the copper MFEC. In contrast, the packed bed diluted to the same catalyst density and operated at an equivalent condition had a centerline temperature deviation of 460°C indicating ignition. The more isothermal temperature profile through the catalyst bed of the copper MFEC led to a higher selectivity of heavy products than that of the packed bed. Also, it enabled a larger reactor diameter to be used with more precise and robust temperature control.

Keywords: Microfibrous entrapped catalyst; Packed bed; Fischer–Tropsch synthesis; Overall heat transfer coefficient; Highly exothermic or highly endothermic reaction

Ambient temperature NO_x emission control for lean-burn engines by electro-catalytic tubes by Ta-Jen Huang; Chung-Ying Wu; De-Yi Chiang; Chia-Chi Yu (pp. 153-158).

Display Omitted► Electro-catalytic tube is effective for lean DeNO_x by direct NO_x decomposition. ► Facile oxygen desorption is driven by self-generated electromotive force. ► Effective lean DeNO_x can be performed at ambient temperature. ► Increasing oxygen concentration enhances the DeNO_x activity considerably. ► Increasing NO_x concentration can increase the DeNO_x activity considerably.Lean-burn gasoline and diesel automobiles can have superior fuel efficiency but require advanced DeNO_x technology. For a catalytic converter to be put underneath the passenger cars, it must be compact enough. Effective automotive DeNO_x treatment should start at ambient temperature to avoid a heating period when the pollutant cannot be effectively treated. An electro-catalytic honeycomb, composed of electro-catalytic tubes, would fulfill this size requirement. This work demonstrates that effective lean DeNO_x can be performed at ambient temperature by an electro-catalytic tube. The DeNO_x activity is relatively insensitive to the variation of temperature from 200 to 600°C and increases slightly when temperature decreases from 200°C to ambient, but is quite sensitive to that of either the oxygen concentration or the NO_x concentration. When the oxygen concentration and the NO_x concentration increase from 0.5 to 14% and from 250 to 3800ppm, respectively, the DeNO_x activities increase considerably. The NO conversion also increases with decreasing NO_x concentration below 250ppm, when there is zero NO₂ yield; these can result in zero NO_x emission.

Keywords: Nitrogen oxide; DeNO; _x; activity; Ambient temperature; Lean-burn engine; Emissions control; Electro-catalytic tube

Photoactivity of S-doped nanoporous activated carbons: A new perspective for harvesting solar energy on carbon-based semiconductors by Teresa J. Bandosz; Juan Matos; Mykola Seredych; M.S.Z. Islam; R. Alfano (pp. 159-165).

Display Omitted► Harvesting solar energy on carbon-based semiconductors. ► Photoactivity of S-doped nanoporous carbons. ► Photocatalytic degradation of methylene blue.Photoactivity of S-doped nanoporous carbons was tested using photocurrent generation, cyclic voltammetry and photodegradation of methylene blue (MB) under artificial solar irradiation. The results were compared to those obtained on unmodified carbons and on commercial TiO₂. A significant generation of photocurrent at visible and NIR radiation from 400 to 1200nm was found. An exposure to ambient light has a strong effect on an open circuit potential indicating the strong activity of S-doped carbons in oxidation reactions. The activity in the process of MB degradation was about 2.2 and 1.9 higher than that obtained on a commercial TiO₂. The extent of photoactivity depends both on the composition of the activated carbon and on the sulfur content. The results suggest that incorporation of sulfur decreases the energy band gap in activated carbon.

Keywords: S-doped activated carbon; Photoactivity; Photocurrent; Photocatalysis

Oxidation of asphaltenes adsorbed onto NiO nanoparticles by Belal J. Abu Tarboush; Maen M. Husein (pp. 166-171).

Display Omitted► In situ prepared NiO nanoparticles show high potency as adsorbent and additive. ► Sequential combustion of adsorbed layers model is more founded. ► Activation energy, E_a, calculations reflect lower values for physically adsorbed species. ► Chemically adsorbed species react at high T with higher E_a. ► Role of NiO nanoparticles is surface exposure not catalytic.Differential thermogravimetry (DTG) and differential scanning calorimetry (DSC) plots help identifying reaction zones and enable activation energy calculations. Recently, Nassar et al. [1,2] reported major shifts in the DTG combustion peaks and reaction zones between virgin and adsorbed asphaltenes onto commercial metal oxide nanoparticles. They attributed the accompanying reduction in activation energy to a significant catalytic role played by the nanoparticles, especially for NiO nanoparticles. It should be noted that in these experiments only monolayer adsorption from toluene model solutions was encountered. More recently, our group reported multilayer adsorption of asphaltenes from heavy oils onto in situ prepared and commercial NiO nanoparticles [3]. Contrary to the previous literature, the thermal behavior of these asphaltenes revealed a surface role entailing an enhanced exposure of adsorbed asphaltenes to the oxidant stream. In this work, we critically re-evaluated the claim of catalytic effect of nanoparticles [1,2,4,5] and provide an experimental protocol which demonstrates a surface effect.

Keywords: Asphaltenes; Nanoparticle; Heavy oil; Oxidation; Activation energy; NiO

Fe-MCM-41 nanoparticles as versatile catalysts for phenol hydroxylation and for Friedel–Crafts alkylation by Yanqiu Jiang; Kaifeng Lin; Yining Zhang; Jie Liu; Guanghua Li; Jianmin Sun; Xianzhu Xu (pp. 172-179).

Display Omitted► Fe-MCM-41 nanoparticles as versatile catalyst for phenol hydroxylation and for Friedel–Crafts alkylation of benzene. ► Higher initial reaction rate with Fe-MCM-41 nanoparticles compared with the relevant larger particles. ► More accessible Fe species in the framework via shorter mesopore channels.Iron-containing MCM-41 nanoparticles (Fe-MCM-41 NPs) were successfully prepared using cetyltrimethylammonium bromide (CTAB) in sodium hydroxide medium at ambient temperature from both direct-hydrothermal and post-synthesis methods. The materials were characterized by X-ray diffraction, nitrogen adsorption/desorption isotherms, SEM, TEM, and UV–vis spectroscopy. The characterization results show the existence of highly ordered hexagonal mesopores in the nanoparticles and tetrahedral Fe species in the framework. In phenol hydroxylation with aqueous H₂O₂, Fe-MCM-41 nanoparticles displayed higher initial reaction rate than Fe-MCM-41 with larger particle size. It is proposed that the diffusion of the reactants is accelerated and the accessibility to the catalytic Fe species is enhanced in the shorter mesopore channels in Fe-MCM-41 nanoparticles. The recyclability potential of the nanoparticles was evaluated in the regeneration by room-temperature washing approach. Fe-MCM-41 NPs also appear to be suitable catalysts for the Friedel–Crafts alkylation of benzene with benzyl chloride.

Keywords: Fe-MCM-41 nanoparticles; Shorter mesopore channels; Phenol hydroxylation; Friedel–Crafts alkylation; Higher initial reaction rate

Dried chitosan-gels as organocatalysts for the production of biomass-derived platform chemicals by Henning Kayser; Christoph R. Müller; Carlos A. García-González; Irina Smirnova; Walter Leitner; Pablo Domínguez de María (pp. 180-186).

.Display Omitted► Aldol condensation of furfural and acetone provides useful platform chemicals. ► Chitosan (presently a waste), catalyzes aldol condensation of furfural and acetone. ► Dried chitosan-gels lead to full conversions in 4h under non-optimized conditions. ► As heterogeneous catalyst, recovery and reuse are straightforward. ► Worldwide available catalysts will be privileged in biorefineries.Aldol condensations between sugar-derived dehydrated aldehydes ( e.g. furfural) and acetone have been proposed as a route to provide useful biomass-derived chemicals. In the quest of sustainable catalytic ways for such aldol condensations, this paper assesses the use of dried chitosan-gels as naturally-immobilized, readily available and non-hazardous amino-based organocatalysts. At room temperature chitosan dried gels are not suitable catalysts for the desired reaction. However, at higher temperatures (>90°C) reaction proceeds efficiently either in solvent-free systems (with addition of catalytic amounts of water) or in water. The set-up of closed reactor set-ups (thermoshakers or microwave reactions) proved highly beneficial for the reaction outcome. Furthermore, chitosan dried gels were successfully re-used for a number of cycles. An efficient catalyst drying method (either lyophilization or scCO₂ drying) was crucial to achieve virtually full conversions in 4h. After pertinent further process optimization, dried chitosan-gels may become very useful catalysts for their use in biomass-based reactions in biorefineries.

Keywords: Chitosan; Aerogels; Furfural; Gasoline; Biofuels; Biorefineries

Alumina-supported Cu@Ni and Ni@Cu core–shell nanoparticles: Synthesis, characterization, and catalytic activity in water–gas-shift reaction by Jiann-Horng Lin; Vadim V. Guliants (pp. 187-194).

Display Omitted► Core–shell Cu–Ni catalysts were synthesized by successive reduction. ► Novel water–gas-shift (WGS) catalysts for hydrogen production. ► Suppressed methanation activity observed for Cu@Ni due to Cu surface segregation. ► Ni@Cu showed similar activity to Cu due to a small mismatch in lattice parameters.Novel Cu@Ni catalysts consisting of a Cu core and a Ni shell and Ni@Cu catalysts have been synthesized by successive reduction of Cu and Ni sources dissolved in ethanol. A combination of transmission electron microscopy (TEM), UV–vis spectroscopy, X-ray diffraction (XRD), CO chemisorption, as well as thermogravimetric analysis (TGA) was used to characterize the core–shell nanoparticle catalysts. The powder XRD patterns, CO chemisorption data, and UV–vis spectra indicated the formation of core–shell structures in the bimetallic Cu–Ni nanoparticles. Cu5@Ni5 and Ni5@Cu6.5 nanoparticles with an average particle size of 4.7 and 5.4nm, respectively, were observed in TEM images. Alumina-supported Ni@Cu nanoparticle catalysts were found to possess similar activity in the water–gas-shift (WGS) reaction to supported Cu catalysts, while supported Cu@Ni catalysts showed comparable WGS activity to supported Ni catalysts and reduced extent of undesirable methanation side-reaction.

Keywords: Water–gas shift reaction; Core–shell nanoparticles; Cu–Ni bimetallic catalysts

Optimal Ir/Pt ratio for the ring opening of decalin in zeolite supported catalysts by Silvana A. D’Ippolito; Laura B. Gutierrez; Carlos L. Pieck (pp. 195-203).

Display Omitted► Decalin ring opening using Pt–Ir/HY zeolite catalysts was studied. ► Catalysts with higher content of Ir have the higher hydrogenolytic activity. ► An increase in Pt content of catalysts favors the hydrogenating activity. ► Ir(1.0)Pt(1.0) and Ir(1.5) Pt(1.5) catalysts showed better performance for SRO.The aim of this study was to study the ring opening of decalin at 300 and 350°C using Pt–Ir/HY zeolite catalysts. Monometallic Ir( x=1.0, 1.5wt%) and Pt( y=1.0, 1.5wt%) and bimetallic Ir(1.0)Pt( y=0.5, 1.0, 1.5wt%), Ir(1.5)Pt( y=0.5, 1.0, 1.5wt%) catalysts were prepared and catalytically tested. Catalysts were characterized by TPR, pyridine TPD, CO–FTIR, XRD, cyclohexane dehydrogenation and cyclopentane hydrogenolysis activity tests. It was found that the acidic character of Ir oxides species increased the amount of strong acid sites of the support. On the other hand, the Pt content increase favored the formation of medium strength acid sites. The catalysts with higher content of Ir had the higher hydrogenolytic activity while an increase in the Pt content decreased the hydrogenolytic activity. The presence of Pt promoted the dehydrogenation of cyclohexane. Higher yields of dehydrogenated products and increased conversion of cis-decalin were observed at the highest temperature level. The zeolite structure was partially collapsed in the case of the Ir(1.5)Pt(1.5) catalyst. Ir(1.0)Pt(1.0) catalysts at 350°C and Ir(1.5)Pt(1.5) catalysts at 300°C, which showed a good performance, seem to have an adequate balance between metal and acid functions that favors the opening of naphthenic rings.

Keywords: SRO decalin; Ir–Pt/HY zeolite; Diesel

Hydroaminomethylation of eugenol with di-n-butylamine catalyzed by rhodium complexes: Bringing light on the promoting effect of Brönsted acids by Kelley C.B. Oliveira; Alexandra G. Santos; E.N. dos Santos (pp. 204-208).

Display Omitted► The hydroaminomethylation of eugenol is reported for the first time. ► New amines are produced with yields reaching 93%. ► Brönsted acids with non-coordinating anions are better promoters. ► Trifluoromethanesulfonic acid is an excellent promoter for hydroaminomethylation.The hydroaminomethylation of eugenol with di-n-butylamine was performed employing a bis[(1,5-ciclooctadiene)(μ-methoxy)rhodium(I)] as pre-catalyst. In the absence of phosphines, the catalyst was efficient in the process, but the regioselectivity for amines was poor. For phosphine-promoted catalyst, the chemoselectivity at the hydroformylation step improved, but the hydrogenation of enamine intermediates was hampered. The regioselectivity within the class of amines was surprisingly high (>96%) for the linear product. The addition of triflic acid (10–20mol%) improved significantly the efficiency of HAM. Employing the 2,2′-bis((diphenylphosphino)methyl)-1,1′-binaphthyl as ancillary and triflic acid as a promoter, the linear product was obtained in up to 93% yield.

Keywords: Hydroaminomethylation; Acid promotion; Tandem catalysis; Renewable feedstock

Pt-based chiral organotin modified heterogeneous catalysts for the enantioselective hydrogenation of 3,4-hexanedione by Virginia Vetere; María B. Faraoni; Julio C. Podestá; Mónica L. Casella (pp. 209-214).

Display Omitted► Organotin compounds with the chiral carbon bonded to the Sn exert a chiral induction. ► PtSn catalysts were obtained by a surface reaction between Pt and menthyl compounds. ► PtSn systems have been active in the liquid phase hydrogenation of 3,4-hexanedione. ► PtSn catalysts have been enantioselective (ee% for 4-hydroxy-3-hexanone of 25%). ► An increase in the ee% with a decrease in the reaction temperature has been observed.In this paper we have studied the liquid-phase enantioselective hydrogenation of 3,4-hexanedione using Pt-based catalysts, modified with chiral organotin compounds derived from the (−)-menthyl group: (−)-Pt-MenSnBu₃ and (−)-Men₃Sn-Sn-(−)-Men₃. The organotin chiral modifiers were carefully synthesized and characterized in order to obtain optically pure compounds.The catalysts were prepared through a controlled surface reaction between the supported transition metal and the organometallic compound, using techniques derived from Surface Organometallic Chemistry on Metals (SOMC/M). The organobimetallic catalytic systems were found to be active and enantioselective in the hydrogenation of 3,4-hexanedione, yielding an enantiomeric excess of 25–27% for 4-hydroxy-3-hexanone.

Keywords: Enantioselectivity; 3,4-Hexanedione; Hydrogenation; (−)-Menthyl derivatives; PtSn; SOMC/M

Selective formation of propylene from methanol over high-silica nanosheets of MFI zeolite by Si Hu; Jie Shan; Qing Zhang; Yan Wang; Yuanshuai Liu; Yanjun Gong; Zhijie Wu; Tao Dou (pp. 215-220).

Display Omitted► High-silica nanosheet MFI zeolite was synthesized using cheap raw materials. ► Nanosheets of MFI zeolite were a high efficient catalyst for MTP. ► Enhanced propylene selectivity (51.0%) and P/E ratio (12.1) were obtained. ► Catalytic performance of MTP could be correlated to the morphology of MFI zeolite.A high-silica nanosheet MFI zeolite was successfully assembled by low-cost raw materials and a special bifunctional organic surfactant. It showed high propylene selectivity (51.0%) and high propylene/ethylene (P/E) ratio (12.1), as well as long catalytic lifetime in methanol to propylene (MTP) reaction under the operating condition of T=450°C, P=0.1MPa ( P_MeOH=20kPa) and WHSV=1.5h⁻¹. The excellent catalytic performance of MFI nanosheets could mainly be ascribed to its unique morphology and textural properties. The ultrathin nanosheets enormously shorten the diffusion path length and thus remarkably improve the molecular diffusion. As a result, the product molecules could easily escape from zeolite channels, and the secondary reactions like aromatization and hydrogen transfer are inhibited dramatically, leading to a high propylene selectivity and a low deactivation rate. Moreover, the considerably large specific surface area and high mesoporosity of the nanosheet MFI zeolite enable it to accommodate a lot more coke deposition, which also gives a good contribution to the notable improvement in the catalytic lifetime.

Keywords: Nanosheets; Methanol to propylene; Propylene selectivity; Catalytic lifetime; Diffusion

A simple method for CO chemisorption studies under continuous flow: Adsorption and desorption behavior of Pt/Al₂O₃ catalysts by Canan Karakaya; Olaf Deutschmann (pp. 221-230).

Display Omitted► A simple and rapid method for determination of metal dispersion is presented. ► Pt/Al₂O₃ is studied based on a CO TPD method at atmospheric pressure. ► CO₂ found in TPD is attributed to CO oxidation by O₂ in the carrier gas. ► Dispersion agrees with data from a pulse adsorption technique and commercial devices.A simple and rapid method for the determination of metal dispersion of technical catalysts is presented, which is based on temperature-programmed desorption (TPD) of pre-adsorbed CO in a continuous-flow reactor at atmospheric conditions. A commercial Pt/Al₂O₃ diesel oxidation catalyst is studied as an example. In the TPD spectra, desorption of CO as well as CO₂ is considered. Furthermore, a pulse adsorption technique is applied to better understand the adsorption–desorption behavior and the oxidation of CO. Metal dispersion based on the TPD methods presented agrees well with data derived from H₂ and CO chemisorption measurements using commercial set-ups.

Keywords: Metal dispersion; CO chemisorption; Pt/Al; ₂; O; ₃; Adsorption; Desorption

Application of a cross-linked Pd–chitosan catalyst in liquid-phase-hydrogenation using molecular hydrogen by Stefan Schüßler; Nico Blaubach; Achim Stolle; Giancarlo Cravotto; Bernd Ondruschka (pp. 231-238).

Display Omitted► A Pd-catalyst based on cross-linked chitosan was prepared. ► The reduction of unsaturated carbonyl compounds proceeded with high selectivities. ► Imines and alkynes were hydrogenated rapidly. ► Catalyst was reused for ten times.Chitosan was cross-linked with hexamethylendiisocyanate and loaded with Pd which was subsequently reduced with NaBH₄. The prepared catalyst was characterized by FT-IR and elemental analysis. The metal content was determined by ICP-MS measurements. Several substrates (cyclohex-2-enone, benzalacetophenone, 1,2-diphenylacetylene, and N-benzylidenaniline) were hydrogenated successfully in ethanol at mild conditions (50°C, p(H₂) ∼6bar) utilizing a microwave reactor. Reaction parameters like temperature, hydrogen pressure, and the solvent were varied. It was shown that the reduction of the catalyst is crucial for catalytic activity. The catalyst was reused ten times for the hydrogenation of cyclohex-2-enone, without showing a dramatic loss in immobilized metal content. Also the polymeric support material did not show any decomposition.

Keywords: Biopolymer; Catalysis; Chitosan; Crosslinking; Hydrogenation; Microwaves; Palladium

Acidic ionic liquid immobilized on magnetic mesoporous silica: Preparation and catalytic performance in esterification by Bin Zhen; Qingze Jiao; Yaping Zhang; Qin Wu; Hansheng Li (pp. 239-245).

Display Omitted► Acidic ionic liquid catalysts immobilized on magnetic mesoporous silica (SCF). ► Pore structure of carriers has critical effect on the immobilization of ionic liquid. ► The catalytic activity of catalysts is affected by the molecule size of reactants. ► The prepared catalysts may have potential application in shape-selective catalysis.Magnetic mesoporous silica (SCF) with cobalt ferrite nanoparticles embedded in silica, exhibiting a mesoporous structure, high magnetic responsivity and paramagnetism, was prepared using a reverse microemulsion-mediated sol–gel method and then modified with 3-mercaptopropyl trimethoxysilane to achieve sulfhydryl-group-modified SCF (MPS-SCF). 1-Allyl-3-(butyl-4-sulfonyl) imidazolium trifluoromethanesulfonate ([BsAIm][OTf]) was immobilized on MPS-SCF via free radical addition. The obtained MPS-SCF and [BsAIm][OTf]/SCF were characterized by FT-IR, XRD, TEM, VSM, elemental analysis and N₂ adsorption–desorption measurements. The immobilization of [BsAIm][OTf] on MPS-SCF and the relationship between the sulfhydryl group (SH) loading of MPS-SCF and the ionic liquid loading of [BsAIm][OTf]/SCF were studied. The catalytic activities of [BsAIm][OTf]/SCF were evaluated through the esterification of oleic acid with straight-chain alcohols. The results showed that more modifications corresponded to an increase in the SH loading of MPS-SCF and a decrease in the average pore diameter and specific surface area of MPS-SCF. The more SH groups that were supported on MPS-SCF, the less ionic liquid was immobilized on [BsAIm][OTf]/SCF due to its smaller pore diameter, which hindered the diffusion and immobilization of [BsAIm][OTf]. Moreover, when the carbon number of the straight-chain alcohol increased, the mass-transfer resistance in [BsAIm][OTf]/SCF rapidly increased and the conversion of oleic acid significantly decreased under the same reaction conditions.

Keywords: Magnetism; Mesoporous silica; Acidic ionic liquid; Catalyst; Esterification

Highly selective Pd/Al₂O₃ catalyst for hydrogenation of methylacetylene and propadiene in propylene stream prepared by γ-radiation by Haibo Yu; Zuwang Mao; Wei Dai; Jing Peng; Maolin Zhai; Genshuan Wei (pp. 246-251).

Display Omitted► Superior selectivity was achieved on Pd/Al₂O₃ catalyst prepared by radiation method. ► High selectivity was attributed to Pd(111) plane and strong adsorption to reactant. ► Pd–support interaction was strengthened by the irradiation process. ► Radiation could be a promising method to prepare highly selective Pd catalysts.Pd/Al₂O₃ catalyst was successfully prepared by γ-radiation induced reduction and showed much higher selectivity in the hydrogenation of methylacetylene and propadiene in propylene stream than catalysts prepared by chemical reduction and calcination method. Characterizations by TEM, XPS, and in situ FTIR proved that the irradiation process was beneficial in achieving uniform distribution of Pd particles on the surface of Al₂O₃ by strengthened Pd–support interaction. The irradiation process was also responsible for the dominant Pd(111) plane and the strong adsorption to target reactant of Pd sites, which we think are the reasons for the high selectivity of the catalyst.

Keywords: Palladium–alumina; Hydrogenation catalyst; γ-Radiation; Methylacetylene; Propadiene

Selective oxidation of benzyl alcohol to benzaldehyde over Co-metalloporphyrin supported on silica nanoparticles by Farook Adam; Wan-Ting Ooi (pp. 252-260).

Display Omitted► Tetrakis( o-chlorophenyl)porphyrinato Co(II) was immobilizing onto silica. ► The porphyrin–silica complex (RHAC-CoPor) formed spherical nanoparticles. ► RHAC-CoPor catalyzed the oxidation of benzyl alcohol to extent of 97.1%. ► A selectivity of 97.7% for benzaldehyde was achieved.Heterogenation of the metalloporhyrin ligand, [tetrakis( o-chlorophenyl)porphyrinato]Co(II) was effected by immobilizing the complex onto inorganic silica support to form spherical nanoparticles of RHAC-CoPor. This insoluble mesoporous hybrid showed a high specific surface area of 114m²g⁻¹ and a pore volume of 0.177cm³g⁻¹. The prepared catalyst possessed a narrow pore size distribution centered at around 4.17nm. The¹³C MAS NMR showed that RHAC-CoPor had three chemical shifts at 12.60, 26.60 and 45.18ppm consistent with the three carbon atoms of the propyl group and a series of chemical shifts in the range of δ=108–167ppm consistent with the presence of the metalloporphyrin complex. Elemental analysis showed the successful immobilization of metalloporphyrin complex onto functionalized RHA silica support. RHAC-CoPor appeared to be an active catalyst in the oxidation of benzyl alcohol, producing 97.1% conversion and 97.7% selectivity for benzaldehyde under an ambient temperature of 70°C. RHAC-CoPor could be regenerated and reused several times by washing with water, followed by drying at 100°C.

Keywords: Rice husk ash; Metalloporphyrin; Sol–gel technique; Nano particle; Oxidation; Benzyl alcohol

Efficient synthesis of E-1,2-bis(silyl)ethenes via ruthenium-catalyzed homocoupling of vinylsilanes carried out in ionic liquids by Szymon Rogalski; Patrycja Żak; Miłosz Miętkiewski; Michał Dutkiewicz; Ryszard Fiedorow; Hieronim Maciejewski; Cezary Pietraszuk; Marcin Śmiglak; Thomas J.S. Schubert (pp. 261-268).

Display Omitted► Highly efficient and selective synthesis in biphasic system. ► Recyclability of the immobilized catalyst. ► Compatibility of ruthenium hydride to a variety of ionic liquids. ► Immobilization of catalyst in ionic liquid was demonstrated by a split test.A series of ruthenium complexes (RuCl₃×3H₂O, [C₅H₅Ru(CH₃CN)₃]⁺[PF₆]⁻, [RuCl₂(PPh₃)₃], [RuHCl(CO)(PPh₃)₃], [RuHCl(CO)(PCy₃)₂]) immobilized in [bmim][Tf₂N] were tested in homocoupling of vinylsilanes (H₂CCHSi(OEt)₃, H₂CCHSi(OⁱPr)₃, H₂CCHSi(OSiMe₃)₃, H₂CCHSiMe(OSiMe₃)₂, and H₂CCHSiPh(OSiMe₃)₂) performed in a biphasic system. The highest catalytic activity and selectivity of homocoupling product was observed for [RuHCl(CO)(PCy₃)₂]. The complex [RuHCl(CO)(PCy₃)₂] immobilized in a variety ionic liquids ([bmim][PF₆], [bmim][BF₄], [bmim][Tf₂N], [bmim][TfO], [bmim][HSO₄], [bmim][Cl], [trimim][MeSO₄], [NBu₃Me][MeSO₄], [PBu₄][Cl], [bpy][PF₆], [bpy][BF₄], [bpy][Cl]) exhibits high catalytic activity in homocoupling of H₂CCHSiMe₂Ph, H₂CCHSi(OEt)₃ and H₂CCHSiMe(OSiMe₃)₂ and enables high-yield stereoselective synthesis of the corresponding E-1,2-bis(silyl)ethenes. The immobilized complex can be easily recycled up to 12 times in the homocoupling of H₂CCHSiMe₂Ph and up to 10 times in the homocoupling of H₂CCHSiMe(OSiMe₃)₂ without a significant drop in activity and selectivity. Results of a split test indicate that the source of catalytic activity is the catalyst immobilized in ionic liquid phase.

Keywords: Ionic liquid; Silylative coupling; Vinylsilanes; Ruthenium complexes; Hydride complexes

Simplified preparation of chirally modified nickel catalyst for enantioselective hydrogenation: A step forward to industrial use by Tsutomu Osawa; I-Yin Sandy Lee; Shinji Ikeda; Takayuki Kitamura; Yoshihisa Inoue; Victor Borovkov (pp. 269-273).

Display Omitted► Metallic 3-μm nickel powder catalyst modified with ( R, R)-tartaric acid and NaBr. ► Modified catalyst afforded up to 90% ee in the hydrogenation of methyl acetoacetate. ► Chiral modification process activates nickel surface prior to the modification. ► Potentially hazardous pre-activation by hydrogen gas can be avoided.A chirally modified nickel catalyst for the enantio-differentiating hydrogenation of β-ketoesters is conventionally prepared by immersing the pre-activated metallic nickel into an aqueous solution of enantiopure tartaric acid (so called “modification step”). During the pre-activation step, nickel precursor is commonly treated with hydrogen gas at elevated temperatures of up to 473K. The X-ray photoelectron spectral examinations of chirally modified nickel catalysts obtained under the different modification conditions revealed that the chiral modification process itself plays a major role in activating the nickel surface whilst the pre-activation procedure is a less important factor. The corresponding enantio-differentiating hydrogenations of methyl acetoacetate in the liquid phase using the prepared chiral catalysts unambiguously confirmed this conclusion, providing quantitative conversions and high enantioselectivities of up to 90%.

Keywords: Chirally modified metallic nickel; Enantioselective hydrogenation; Hydrogen activation; XPS; Methyl acetoacetate; Tartaric acid

Photocatalytic activity and photoinduced hydrophilicity of brookite–heteropolyacid hybrid films by Kunchaya Pruethiarenun; Toshihiro Isobe; Sachiko Matsushita; Akira Nakajima (pp. 274-279).

Display Omitted► A transparent PW₁₂/brookite hybrid film was prepared by layer-by-layer process. ► The film exhibited better photocatalytic activity than a brookite film. ► The film also provided a higher hydrophilization rate under UV illumination. ► The electron scavenger effect of PW₁₂ plays an important role on these results.After transparent hybrid films of brookite (TiO₂) and 12 tungsto(VI) phosphoric acid (PW₁₂) were prepared using layer-by-layer (LBL) processing, a comparative study of photocatalytic decomposition activity and photoinduced hydrophilicity for the films was conducted using gaseous 2-propanol (IPA) decomposition and sessile drop method. The TTP (TiO₂/TiO₂/PW₁₂) film exhibited better photocatalytic activity on the decomposition of gaseous IPA than that of the TT (TiO₂/TiO₂) film. Moreover, the TTP film provided a higher hydrophilization rate under UV illumination, and provided better sustainability of the hydrophilicity in the dark than the TT film did. The generation of PW₁₂⁻ by electron transfer from TiO₂ to PW₁₂ was inferred as a key factor underpinning the overall performance of wettability conversion before and after UV illumination on this hybrid film.

Keywords: Brookite; Photocatalyst; Layer-by-layer; Keggin; Hydrophilicity

Ammonia synthesis over cobalt catalysts doped with cerium and barium. Effect of the ceria loading by Magdalena Karolewska; Elżbieta Truszkiewicz; Bogusław Mierzwa; Leszek Kępiński; Wioletta Raróg-Pilecka (pp. 280-286).

Display Omitted► Effect of CeO₂ on the activity of the Co catalysts was studied. ► Ceria plays the role of a structural promoter in Co–Ce–Ba catalysts. ► Ceria changed the reduction route of the cobalt catalysts. ► An optimum ceria loading in the catalyst was between 10 and 13wt%. ► The studied Co–Ce–Ba catalysts are highly active in ammonia synthesis.The effect of ceria loading on the activity and thermal stability of a cobalt catalyst for ammonia synthesis has been studied. The concentration of CeO₂ in the Co₃O₄+CeO₂ mixtures ranged from 0 to 29wt%, whereas the barium content was constant and equaled 13wt% in relation to Co₃O₄. Kinetic measurements in NH₃ synthesis were carried out in a flow differential reactor operating under standard conditions ( p=6.3MPa, T=400°C, H₂:N₂=3:1). The kinetic measurements of NH₃ synthesis were supplemented with the characterization studies of the obtained materials – N₂ physisorption, XRPD, H₂ chemisorption, TPR-TG/DTG-MS and SEM-EDS. It has been found that ceria plays the role of a structural promoter; it hinders the sintering of Co₃O₄ during calcination and stabilizes the surface area of Co under reaction conditions. Moreover, it seems that ceria stabilizes the hcp phase of metallic cobalt, which results in a higher activity of the cobalt catalysts. The co-promoted cobalt catalyst containing 11.5wt% of CeO₂ (symbol Co/Ce(11.5)/Ba) was shown to be more active in NH₃ synthesis than the conventional fused iron catalyst (KM I, H. Topsoe). Moreover, the catalyst Co/Ce(11.5)/Ba is very resistant to overheating. Heat treatment at 600°C for 160h (3H₂:N₂=30.0l/h, p=0.1MPa) results in a decrease of its activity in NH₃ synthesis by only a few percent.

Keywords: Ammonia synthesis; Cobalt catalyst; Barium and cerium promoters; Ceria loading

Cu/SiO₂ hybrid catalysts containing HZSM-5 with enhanced activity and stability for selective hydrogenation of dimethyl oxalate to ethylene glycol by Haiqiang Lin; Xinlei Zheng; Zhe He; Jianwei Zheng; Xinping Duan; Youzhu Yuan (pp. 287-296).

Display Omitted► A novel type of hybrid catalyst composed of Cu/SiO₂ and HZSM-5 zeolite is prepared. ► Introduction of HZSM-5 modifies the copper dispersion and surface Cu⁺ site concentration. ► Introduction of HZSM-5 considerably improves the heat-resistance of the catalyst. ► The hybrid catalyst shows enhanced performance for hydrogenation of dimethyl oxalate. ► The hybrid catalyst can retain its excellent activity for longer than 300h.A novel type of hybrid catalysts composed of Cu/SiO₂ and H-form ZSM-5 (HZSM-5) zeolite, prepared using urea-assisted gelation method, displayed excellent catalytic activity and stability for the selective hydrogenation of dimethyl oxalate (DMO) to ethylene glycol (EG). The content and SiO₂/Al₂O₃ ratio of HZSM-5 significantly influenced the performance of hybrid catalysts. An unprecedentedly high EG space time yield of 1.50gg_-cat⁻¹h⁻¹, with DMO conversion of 99.5% and EG selectivity of 94.8%, were obtained on a hybrid catalyst containing 3wt% of HZSM-5 with SiO₂/Al₂O₃=38. The characterizations of N₂ physisorption and N₂O chemisorptions revealed that both specific surface area and copper dispersion were promoted by introducing HZSM-5 zeolite into the Cu/SiO₂ catalyst. Moreover, X-ray Auger electron spectroscopy and in situ Fourier transform infrared spectroscopy of chemisorbed CO demonstrated that the surface Cu⁺ site concentration of the catalysts containing HZSM-5 was higher than those without HZSM-5. The results indicated that the introduction of HZSM-5 zeolite changed the crystallization behaviors of cupric phyllosilicate precursor, essentially improving copper dispersion and enhancing copper–silica interaction. Furthermore, the specific zeolitic cages and negatively charged framework of HZSM-5 zeolite incorporated into Cu/SiO₂ entities might also be beneficial for accommodation and stabilization of highly dispersed cuprous species, which act as efficient active sites for the activation of ester groups.

Keywords: Copper; HZSM-5; Ethylene glycol; Hydrogenation; Stability

A rapid microwave-assisted solution combustion synthesis of CuO promoted CeO₂–M_xO_y (M=Zr, La, Pr and Sm) catalysts for CO oxidation by Lankela H. Reddy; Gunugunuri K. Reddy; Damma Devaiah; Benjaram M. Reddy (pp. 297-305).

Display Omitted► Designed active CO oxidation catalysts by microwave-induced combustion synthesis. ► Incorporation of various dopants enhanced CO oxidation activity of copper–ceria. ► The addition of dopants resulted in improved textural/structural properties. ► Mixed oxides are more active than single oxides due to synergetic effects. ► Zirconium doped copper–ceria exhibited superior CO oxidation activity.A series of copper oxide promoted CeO₂–M_xO_y (M_xO_y=ZrO₂, La₂O₃, Pr₂O₃ and Sm₂O₃) mixed oxides were synthesized by microwave-assisted solution combustion method using urea as the fuel and the respective metal nitrates as the precursors. The physico-chemical properties of the synthesized materials were analysed by BET surface area, X-ray diffraction (XRD), Raman spectroscopy, temperature programmed reduction/oxidation (TPR/TPO), X-ray photoelectron spectroscopy (XPS) and oxygen storage capacity (OSC) methods. XRD measurements confirmed the formation of solid solutions between ceria and the doped metal oxides in the presence of copper promoter. Raman measurements suggested defective structure of the mixed oxide solid solutions resulting in the formation of oxygen vacancies. The TPR/TPO studies revealed that the reduction behaviour of ceria depends on the type of metal dopant. XPS studies confirmed the presence of cerium in both Ce³⁺ and Ce⁴⁺ oxidation states in all mixed oxides. All the doped mixed oxides exhibited better CO oxidation activity compared to the undoped copper–ceria catalysts. Among various samples, ZrO₂ doped copper–ceria showed a high activity ( T_1/2∼378K) followed by samarium, praseodymium and lanthanum oxide doped samples, respectively. Significance of the combustion synthesis method has been addressed that include simplicity, flexibility and the control of different favourable factors.

Keywords: Copper–ceria; Microwave-induced solution combustion synthesis; CO oxidation; Catalyst characterization

A novel heteropolyanion-based amino-containing cross-linked ionic copolymer catalyst for epoxidation of alkenes with H₂O₂ by Yan Leng; Weijie Zhang; Jun Wang; Pingping Jiang (pp. 306-311).

Display Omitted► A new heteropolyanion-based amino-containing cross-linked polymeric hybrid is prepared. ► The hybrid catalyst leads to the heterogeneous epoxidation of alkenes with H₂O₂. ► The hybrid catalyst gives high conversion and selectivity. ► The catalyst shows easy recovery, and very steady reuse.A heteropolyanion-based cross-linked ionic copolymer was prepared by the anion-exchange of a newly task-specific designed amino-containing ionic copolymer with a Keggin heteropolyacid, and characterized by FT-IR, SEM, TG, XRD, UV–vis, ESR,¹H NMR, and elemental analysis. Its catalytic activity was evaluated in the epoxidation of alkenes with aqueous H₂O₂. The resultant heteropolyanion-based ionic copolymer is revealed to be a highly efficient heterogeneous catalyst for epoxidation of alkenes with H₂O₂, adding the advantages of convenient recovery and steady reuse.

Keywords: Heteropolyacid; Cross-linked copolymer; Ionic liquid; Epoxidation of alkenes; Heterogeneous catalysis

The effect of hydrothermal treatment of FCC catalysts and ZSM-5 additives in catalytic conversion of biomass by Ofei D. Mante; F.A. Agblevor; S.T. Oyama; R. McClung (pp. 312-320).

Display Omitted► Hydrothermal treatment of the FCC catalyst reduced the selectivity for coke. ► Mild steam treatment at 732°C for 4h FCC catalyst produced bio-oils of higher quality. ► Phosphorus stabilization of ZSM-5 prevented detrimental effects of steam treatment on the process. ► The effect of steam treatment of Y-zeolite FCC catalyst was different from the ZSM-5 based additives.Fresh fluid catalytic cracking (FCC) catalysts and ZSM-5 additives were hydrothermally treated with 100% steam at 732°C (1350°F) and 788°C (1450°F) for 4h in a fluidized bed reactor. The catalytic pyrolysis of hybrid poplar wood with fresh and steam treated catalysts was conducted in a 50mm bench scale bubbling fluidized bed reactor at 475°C and a weight hourly space velocity (WHSV) of 2h⁻¹. BET surface area measurements showed a reduction of 24% and 34% in the surface area of the FCC catalyst after steam treatment at 732°C and 788°C respectively. The non-phosphorus based ZSM-5 additive lost about 15% of its surface area after mild steaming at 732°C. However, the phosphorus impregnated ZSM-5 additive was not affected at both steaming conditions. The hydrothermal treatment of the catalysts influenced the catalytic product distribution and the quality of the bio-oil. The steamed FCC catalyst produced higher organic liquid and gas yields and lower formation of coke and water. The viscosity and the density of the bio-oils produced from the steamed FCC catalyst were lower than those produced with the fresh FCC catalyst. In the case of the ZSM-5 additives, the steam treatment affected only the organic liquid and gas yields. The organic liquid yield increased and the gas yield decreased. Steaming of the ZSM-5 additive did not show any effect on the char/coke yield as was seen with the FCC catalyst due to the lower tendency of ZSM-5 to form coke. The GC analysis of the product gases suggested that steam treatment influenced the catalyst selectivity in the formation of CO, CO₂, H₂, CH₄ and C₂C₅ hydrocarbons. The¹³C NMR analysis of the bio-oil showed generally that steaming of the FCC catalyst increased the selectivity for the production of aromatic hydrocarbons.

Keywords: Catalytic pyrolysis of biomass; Catalyst steaming; FCC catalyst; ZSM-5 additives; Bio-oils

Catalytic performance of sucrose-derived CMK-3 in oxidative dehydrogenation of propane to propene by Piotr Michorczyk; Piotr Kuśtrowski; Paula Niebrzydowska; Anna Wach (pp. 321-328).

Display Omitted► CMK-3 carbon replica exhibits high catalytic activity in dehydrogenation of propane. ► Reaction temperature and feed composition strongly influence catalytic performance. ► Changes in surface composition are observed during the catalytic process. ► Oxygen-containing groups play a crucial role in the propane conversion.CMK-3 carbon replica was synthesized by carbonization of sucrose introduced to the pore system of a SBA-15 hard template followed by dissolving SiO₂ with HF. The material with a stable hexagonal structure and an expanded surface area ( S_BET=1287m²/g) was obtained. TG measurements showed that CMK-3 type mesoporous carbon started to be intensively oxidized by molecular O₂ above 723K. This carbon sample was tested as a catalyst of dehydrogenation of propane to propene under oxidative (O₂:C₃H₈=0.25, 0.50 and 1.00) and non-oxidative (O₂:C₃H₈=0.00) conditions in the temperature range from 573 to 873K. The propene yield increased with rise in the reaction temperature, however above 573K the formation of side-products (C₂H₆, C₂H₄, CH₄ and H₂) was observed. Moreover, coke was deposited on the catalyst surface. A decrease in the mass of a catalyst bed after the catalytic runs suggested the participation of oxygen in burning of deposited and bulk coke. The surface composition of a spent catalyst was investigated by XPS and TPD analysis. The changes in the concentration of oxygen functional groups, caused by the catalytic reaction, were observed regardless of a reaction temperature and feed composition.

Keywords: Oxidative dehydrogenation; Propene; Carbon replica; CMK-3

Modification of MCM-22 zeolite through sequential post-synthesis treatments. Implications on the acidic and catalytic behaviour by V. Machado; J. Rocha; A.P. Carvalho; A. Martins (pp. 329-338).

Display Omitted► MCM-22 zeolite was modified through desilication and alkaline+acid treatment. ► Inter and inter+intracrystalline mesoporosity was achieved using different experimental conditions. ► Alkaline+acid treatment led to a transformation from 2-D to 3-D pore structure. ► The deposition of EFAL species favours the production of p-xylene isomer.Desilication and a combination of alkaline followed by acid treatment were applied to MCM-22 zeolite using two different base concentrations. The samples were characterised by powder X-ray diffraction,²⁷Al and²⁹Si MAS-NMR spectroscopy, SEM, TEM and low temperature N₂ adsorption. The acidity of the samples was study through pyridine adsorption followed by FTIR spectroscopy and by the analyses of the hydroxyl region. The catalytic behaviour, anticipated by the effect of post-synthesis treatments on the acidity and space available inside the two internal pore systems was evaluated by using the model reaction of m-xylene transformation.The generation of mesoporosity was achieved upon alkaline treatment with 0.05M NaOH solution and practically no additional gain was obtained when the more concentrate solution, 0.1M, was used. Instead, Al extraction takes place along with Si, as shown by²⁹Si and²⁷Al MAS-NMR data, followed by Al deposition as extraframework species.Samples submitted to alkaline plus acid treatments present distinct behaviour. When the lowest NaOH solution was used no relevant effect was observed on the textural characteristics. Additionally, when the acid treatment was performed on an already fragilized MCM-22 structure, due to previous desilication with 0.1M NaOH solution, the extraction of Al from both internal pore systems promotes their interconnection, evolving from a 2-D to a 3-D porous structure. This transformation has a marked effect in the catalytic behaviour, allowing an increase of m-xylene conversion as a consequence of an easier and faster molecular traffic in the 3-D structure. On the other hand, the continuous deposition of extraframework Al species inside the pores leads to a shape selective effect that privileges the formation of the more valuable isomer p-xylene.

Keywords: MCM-22; Desilication; Acid treatment; Acidity; m; -Xylene transformation

Vanadium containing heteropoly molybdates as precursors for the preparation of MoVP oxides supported on alumina catalysts for ammoxidation of m-xylene by B. Hari Babu; G. Parameswaram; A. Sri Hari Kumar; P.S. Sai Prasad; N. Lingaiah (pp. 339-345).

Display Omitted► MPAV supported on alumina catalysts are active for ammoxidation of m-xylene. ► The ammoxidation activity depends on content of V in MPA and MPAV on support. ► Minimum amount of V is favorable in heteropoly molybdate. ► MoO₃ and V₂O₅ derived from MPAV are responsible for ammoxidation activity.Vanadium incorporated molybdophosphoric acid (MPAV) was used as a precursor to prepare MoVP oxide supported on alumina catalysts. The catalysts were prepared by impregnation of MPAV on alumina and subjecting them to calcination at 450°C. The catalysts were characterized by X-ray diffraction, Fourier transform infrared, temperature programmed reduction and X-ray photo electron spectroscopy to study the nature of interaction of MPAV with Al₂O₃. The characterization results revealed the decomposition of MPAV Keggin ion on alumina and the formation of its constituent oxides during calcination. The nature of metal oxide species formed on the surface of alumina depended on MPAV loading and the V content. The crystalline nature of metal oxides derived from the decomposition of MPAV_x increased with increase in vanadium content. The activity of the catalysts during the ammoxidation of m-xylene also depended on MPAV loading and the content of V, as they were responsible for the dispersion of the constituent metal oxides on alumina.

Keywords: Ammoxidation; m; -Xylene; Molybdophosphoric acid; Vanadium; Alumina

Fatty ketones from the rearrangement of epoxidized vegetable oils by Luis A. Rios; Biviana A. Llano; Wolfgang F. Hoelderich (pp. 346-350).

Display Omitted► Epoxidized vegetable oils can be transformed to ketones via rearrangement reaction. ► Acid catalysts are active if their Brönsted acid sites are accessible. ► Formation of ketone is favored by strong acidic catalysts and temperature. ► Polar-protic solvents increase the ketone yield but decrease the selectivity. ► Epoxide rearrangement takes place through a hydride migration.The rearrangement of epoxidized vegetable oils to produce fatty ketones, catalyzed by acidic resins, is disclosed. The non-microbial production of fatty ketones from epoxidized vegetable oils has not been previously reported. Some of the variables affecting the ketone formation such as acidic strength of the catalyst, temperature and solvent are studied in order to determine the conditions that favor the rearrangement. Epoxidized vegetable oils can be easily transformed to the respective ketones via a rearrangement reaction catalyzed by acidic resins. Other kind of acidic catalysts are active for this reaction if their Brönsted acid sites are accessible to protonate the epoxide. Formation of ketones, from the rearrangement of epoxidized methyl oleate, is favored in the presence of strongly acidic catalysts and enhanced by increasing temperature. Polar-protic solvents increase the ketone yield but decrease the ketone selectivity because they are added to the epoxide ring. The mechanism for the epoxide rearrangement is very likely to take place through a hydride migration to the carbocation generated in the acid-catalyzed epoxide ring opening.

Keywords: Ketone; Epoxide; Oil; Vegetable; Acid; Resin; Rearrangement

Cooperation between the surface hydroxyl groups of the support and organic additives in the highly selective hydrogenation of citral by Hai-Jun Jiang; Hong-Bin Jiang; De-Ming Zhu; Xue-Li Zheng; Hai-Yan Fu; Hua Chen; Rui-Xiang Li (pp. 351-358).

Display Omitted► Hydrogenation selectivity to CO bond of citral over AlO(OH) is enhanced in water. ► Water film formed by action between AlO(OH) and water leads to the selective adsorption of CO bond. ► Modification of diamines to metal sites can further improve the catalyst performance.A Ru/AlO(OH) catalyst was prepared by co-precipitation and characterised by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), thermo-gravimetry (TG), and Fourier transform infrared spectroscopy (FT-IR). Its catalytic performance was tested in the selective hydrogenation of citral. The results showed that the combination of Ru/AlO(OH) and water obviously improved the catalyst activity and its selectivity to geraniol and nerol. Introducing organic additives increased the hydrophilicity of metal particles, which favoured the adsorption of the citral CO bond over the adsorption of the conjugated CC bond, improving the selectivity to and inhibiting the further hydrogenation of geraniol and nerol. The maximum yield of geraniol and nerol (81%) was achieved in water with ethylenediamine as an additive.

Keywords: Ruthenium; Citral; Hydrogenation; α,β-Unsaturated alcohol; Organic amine

Schiff base complex of metal ions supported on superparamagnetic Fe₃O₄@SiO₂ nanoparticles: An efficient, selective and recyclable catalyst for synthesis of 1,1-diacetates from aldehydes under solvent-free conditions by Mohsen Esmaeilpour; Ali Reza Sardarian; Jaber Javidi (pp. 359-367).

Display Omitted► Preparation of the novel magnetic nanocatalysts. ► Schiff base complex of metal ions functionalized magnetite@silica nanoparticles. ► Recyclable magnetic nanocatalysts by external magnetic field. ► Efficient chromium magnetic nanocatalysts in the synthesis of acylals.We report a new multistep method for preparing functionalized superparamagnetic Fe₃O₄@SiO₂ possessing high saturation magnetization. During the first step, Fe₃O₄@SiO₂ nanosphere core–shell is synthesized using nano-Fe₃O₄ as the core, TEOS as the silica source and PVA as the surfactant. Then, Schiff base complex of metal is synthesized from the reaction between Schiff base and metal acetates [Co(OAc)₂, Mn(OAc)₂, Ni(OAc)₂, Cu(OAc)₂, Hg(OAc)₂, Cr(OAc)₃ and Cd(OAc)₂] on the Fe₃O₄@SiO₂ surface. The structural and magnetic properties of functionalized magnetic silica are identified by transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM) instruments. Moreover, functionalized Fe₃O₄@SiO₂ possessed a superparamagnetic characteristic with saturation magnetization value of about 34emu/g. NMR, FT-IR, elemental analysis and XRD were also used for the identification of these structures. The catalytic ability of Fe₃O₄@SiO₂/Schiff base complex of metal ions was found to be an efficient nanocatalyst for the conversion of aldehydes to their corresponding 1,1-diacetates compounds under mild and solvent-free conditions at room temperature. This method gives notable advantages such as excellent chemoselectivity, mild reaction condition, short reaction times and excellent yields. Also, the aforementioned nanocatalyst can be easily recovered by a magnetic field and reused for subsequent reactions for at least 5 times without noticeable deterioration in catalytic activity.

Keywords: Superparamagnetic; Nanocatalyst; 1,1-Diacetates; Schiff base complex; Solvent-free

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Applied Catalysis A, General (v.445-446, #)

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Applied Catalysis A, General (v.445-446, #)