Applied Catalysis A, General (v.346, #1-2)

Contents (iii-ix).

Catalytic partial oxidation of methane has been reviewed with an emphasis on the reaction mechanisms over transition metal catalysts. The thermodynamics and aspects related to heat and mass transport is also evaluated, and an extensive table on research contributions to methane partial oxidation over transition metal catalysts in the literature is provided. ▪Catalytic partial oxidation of methane has been reviewed with an emphasis on the reaction mechanisms over transition metal catalysts. The thermodynamics and aspects related to heat and mass transport is also evaluated, and an extensive table on research contributions to methane partial oxidation over transition metal catalysts in the literature is provided.Presented are both theoretical and experimental evidence pointing to inherent differences in the reaction mechanism over transition metals. These differences are related to methane dissociation, binding site preferences, the stability of OH surface species, surface residence times of active species and contributions from lattice oxygen atoms and support species.Methane dissociation requires a reduced metal surface, but at elevated temperatures oxides of active species may be reduced by direct interaction with methane or from the reaction with H, H2, C or CO.The comparison of elementary reaction steps on Pt and Rh illustrates that a key factor to produce hydrogen as a primary product is a high activation energy barrier to the formation of OH. Another essential property for the formation of H2 and CO as primary products is a low surface coverage of intermediates, such that the probability of O–H, OH–H and CO–O interactions are reduced.The local concentrations of reactants and products change rapidly through the catalyst bed. This influences the reaction mechanisms, but the product composition is typically close to equilibrated at the bed exit temperature.
Keywords: Synthesis gas; Hydrogen; Partial oxidation; Methane; Nickel; Cobalt; Iron;

Iron oxide colloids and their heterogenization by silica sol–gel entrapment: Catalytic and magnetic properties by Florentina Neaţu; Alexander Kraynov; Lawrence D'Souza; Vasile I. Pârvulescu; Krištof Kranjc; Marijan Kočevar; Victor Kuncser; Ryan Richards (28-35).
Fe3O4 colloids modified by the chiral ligand cinchonidine were prepared with the goal of obtaining a magnetic and catalytic nano-material and were subsequently embedded in silica to form a heterogeneous catalyst. The systems were characterized by TEM and XRD measurements, while the Mössbauer technique was applied for measuring the magnetic properties of the Fe3O4 colloids. The hyperfine magnetic field distribution was consistent with one type of Fe oxide, namely, the magnetite (Fe3O4). These colloids, both as ‘quasi-homogenous catalysts’ (or soluble heterogeneous catalysts) and embedded in silica (heterogeneous catalysts) were employed in the selective hydrogenolysis of complex bicyclo[2.2.2]oct-7-enes (bicyclo[2.2.2]oct-2-enes when unsubstituted).
Keywords: Fe oxide; Cinchonidine; Silica-embedded colloids; TEM; XRD; Mössbauer; Hydrogenolysis of bicyclo[2.2.2]oct-7-enes;

Study of hydrogen surface mobility and hydrogenation reactions over alumina-supported palladium catalysts by Mersaka Benkhaled; Claude Descorme; Daniel Duprez; Stéphane Morin; Cécile Thomazeau; Denis Uzio (36-43).
Alumina-supported Pd catalysts with different particle surface densities have been prepared using incipient wetness impregnation of aqueous solution of a palladium nitrite complex. Buta-1,3-diene and orthoxylene hydrogenation reactions were performed both in a batch and a fixed bed reactor. Hydrogen surface mobility was studied using H2–D2 isotopic exchange. The influence of (i) the particle surface density and (ii) the surface area of the support on the catalytic properties are discussed. The turnover frequency (TOF) of the but-1,3-diene hydrogenation was highly sensitive to the surface density of Pd particles (D sp). Moreover, for a given surface density, TOF also depend on the nature of the alumina support. For a given support, modifications of the electronic properties of palladium can explain the increase of the reaction rate with D sp while changes in the kinetics of hydrogen surface diffusion are proposed to explain the support effect.▪Alumina-supported Pd catalysts with different particle surface densities have been prepared using incipient wetness impregnation of aqueous solution of a palladium nitrite complex. Buta-1,3-diene and orthoxylene hydrogenation reactions were performed both in a batch and a fixed bed reactor. Hydrogen surface mobility was studied using H2–D2 isotopic exchange. The influence of (i) the particle surface density and (ii) the surface area of the support on the catalytic properties are discussed. The turnover frequency (TOF) of the but-1,3-diene hydrogenation was highly sensitive to the surface density of Pd particles (D sp). Moreover, for a given surface density, TOF also depend on the nature of the alumina support. For a given support, modifications of the electronic properties of palladium can explain the increase of the reaction rate with D sp while changes in the kinetics of hydrogen surface diffusion are proposed to explain the support effect.
Keywords: Highly dispersed Pd catalysts; Particle surface density; Butadiene hydrogenation; Orthoxylene hydrogenation; Surface mobility; H/D exchange;

Acid-catalyzed etherification of bio-glycerol and isobutylene over sulfonic mesostructured silicas by J.A. Melero; G. Vicente; G. Morales; M. Paniagua; J.M. Moreno; R. Roldán; A. Ezquerro; C. Pérez (44-51).
Sulfonic acid-modified mesostructured silicas have demonstrated an excellent catalytic performance in the etherification of glycerol with isobutylene. Their activity and selectivity towards valuable products for fuel bio-additives (di-tert-butylglycerols and tri-tert-butylglycerol) have shown to be comparable or even superior to those of macroporous commercial sulfonic acid resins. ▪Sulfonic-acid-functionalized mesostructured silicas have demonstrated an excellent catalytic behavior in the etherification of glycerol with isobutylene to yield tert-butylated derivates. Di-tert-butylglycerols (DTBG) and tri-tert-butylglycerol (TTBG) have shown to be valuable fuel additives leading to decreases in the emission of particulate matter, hydrocarbons, carbon monoxide and unregulated aldehydes. Likewise, said ethers can also act as cold flow improvers for use in biodiesel, reducing also its viscosity. The activities and selectivities achieved over sulfonic acid-functionalized mesostructured silicas are comparable or even superior to those displayed by widely used macroporous commercial acid resins. Under optimized reaction conditions, these mesostructured catalysts yield a complete glycerol conversion with a combined selectivity towards DTBG and TTBG up to ca. 90%. Furthermore, no formation of undesirable isobutylene oligomers is observed. The acid strength of the sulfonic acid sites has also been found to be an important factor affecting the catalytic performance of these materials.
Keywords: Sulfonic; Isobutylene; Glycerol; Tertiary butyl ethers; Mesoporous; Fuel additives;

Biomass to fuels: A water-free process for biodiesel production with phosphazene catalysts by Miriam Cerro-Alarcón; Avelino Corma; Sara Iborra; Juan Pedro Gómez (52-57).
Non-ionic triamino(imino)phosphoranes (phosphazenes) give excellent results as base catalysts for the water-free alcoholysis of vegetable fatty esters. Two phosphazene catalysts, with different intrinsic basicities, P1-t-Bu and P4-t-Bu, together with reaction parameters, such as temperature, alcohol/oil molar ratio, or catalyst concentration, have been studied. It was found that activity could be directly correlated to the basicity of the catalyst. Very high biodiesel yields were achieved under mild reaction conditions with methanol and ethanol. The catalyst can be recovered and recycled. ▪Non-ionic triamino(imino)phosphoranes (phosphazenes) give excellent results as base catalysts for the water-free alcoholysis of vegetable fatty esters. Two phosphazene catalysts, with different intrinsic basicities, P1-t-Bu and P4-t-Bu, together with reaction parameters, such as temperature, alcohol/oil molar ratio, or catalyst concentration, have been studied. It was found that activity can be directly correlated to the basicity of the catalyst. Very high biodiesel yields (93–95% mol) were achieved under mild reaction conditions with methanol and ethanol. The catalyst can be recovered and recycled.
Keywords: Biomass to fuels; Biodiesel; Transesterification; Alcoholysis; Organocatalysis; Phosphazene catalyst;

Deactivation behavior of ruthenium promoted Co/γ-Al2O3 catalysts in Fischer–Tropsch synthesis by Ahmad Tavasoli; Reza M. Malek Abbaslou; Ajay K. Dalai (58-64).
Detailed activity study and the deactivation of Ru-Co/γ-Al2O3 catalyst for Fischer–Tropsch (FT) synthesis over 1000 h was investigated considering different deactivation mechanisms. Morphology changes of the catalyst during FT synthesis were studied using XRD, TPR, BET, ICP, carbon determination, H2 chemisorption and re-oxidation techniques. When the P H 2 O / ( P H 2 + P CO ) in the reactor is above 0.75 the deactivation rate is not dependent on the number of the catalyst active sites and is zero order to CO conversion. In this case the main deactivation mechanisms are: cobalt re-oxidation, metal support interactions and aluminates formation. The deactivation of Ru-Co/γ-Al2O3 is related to cobalt cluster size. At lower amounts of P H 2 O / ( P H 2 + P CO ) deactivation can be simulated with a power law expression with a power order of 39.7 and the main deactivation is due to sintering. Regeneration of catalyst at 275 °C recovered the catalyst activity by 69.9% of total activity loss due to the reduction of oxidized cobalts. Catalyst regeneration at 400 °C recovered the activity by 21.9% of total activity loss due to the reduction of refractory forms of oxidized cobalt generated by cobalt–alumina interactions. 7.2% of total activity loss is irreversible and can be assigned to aluminates formation, sintering and coke deposition.When P H 2 O / ( P H 2 + P CO ) > 0.75 the deactivation rate of Ru-Co/γ-Al2O3 is zero order and is due to cobalt oxidation and metal support interactions. At lower P H 2 O / ( P H 2 + P CO ) deactivation is a power law expression with a power order of 39.7 and is due to sintering. 69.9% of total activity loss is due to oxidation, 21.9% is due to metal support interactions and 7.2% is due to sintering, aluminates and coke formation. ▪
Keywords: Fischer–Tropsch; Cobalt catalyst; Deactivation; Activity recovery; Modeling;

Oxovanadium(IV) Schiff base complexes derived from 2,2′-dimethylpropandiamine: A homogeneous catalyst for cyclooctene and styrene oxidation by Saeed Rayati; Marjan Koliaei; Fatemeh Ashouri; Sajjad Mohebbi; Andrzej Wojtczak; Anna Kozakiewicz (65-71).
Oxovanadium(IV) complexes of Schiff base ligands derived from 2,2′-dimethylpropandiamine have been prepared and characterized. These complexes catalyse the oxidation of cyclooctene and styrene using tert-butylhydroperoxide as oxidant in good yield. Various parameters such as solvent, temperature and concentration of oxidant have been optimized. Excellent selectivity of epoxidation for cyclooctene and good selectivity for styrene were obtained. ▪Tetradentate Schiff base ligands, derived from aromatic aldehydes and aliphatic diamine (2,2′-dimethylpropandiamine), and their vanadyl complexes have been prepared and characterized. Catalytic potential of these complexes was tested for the oxidation of cyclooctene and styrene using tert-butylhydroperoxide (TBHP) as oxidant. The effects of molar ratio of oxidant to substrate, temperature and solvent have been studied. Excellent selectivity of epoxidation for cyclooctene and good selectivity for styrene were obtained. The mechanism of oxidation has also been discussed.
Keywords: Schiff base; Oxovanadium; Catalyst; Olefins; tert-Butylhydroperoxide;

Nanofibres of poly(amideimide) (PAI) were prepared by electrospinning from solutions of 11 wt% PAI in dimethylformamide. Addition of small amounts of citric acid to the spinning solution improved the fibre size and fibre uniformity. Catalytic activation of the electrospun nanofibres was performed by coating the fibres with an organic solution of palladium diacetate containing citric acid onto the fibres and subsequent thermally induced conversion to nanosized palladium clusters. The catalyst was durably fixed on the fibres by this procedure. The presence of palladium (Pd) nanoparticles was confirmed by R-ray-diffractometry. These fibres were applied in the hydrogenation of methyl-cis-9-octadecenoate as a model reaction. The palladium-doped nanofibres showed an almost seven times higher hydrogenation rate than a commercial palladium catalyst supported on alumina.Nanofibres of poly(amideimide) (PAI) were prepared by electrospinning from solutions of 11 wt% PAI in dimethylformamide. Addition of small amounts of citric acid to the spinning solution improved the fibre size and fibre uniformity. Catalytic activation of the electrospun nanofibres was performed by coating with an organic solution of palladium diacetate containing citric acid onto the fibres and subsequent thermally induced conversion to nanosized palladium clusters. The catalyst was durably fixed on the fibres by this procedure. The presence of palladium (Pd) nanoparticles was confirmed by XRD-diffractometry. These fibres were applied in the hydrogenation of methyl-cis-9-octadecenoate as a model reaction. The palladium-doped nanofibres showed an almost seven times higher hydrogenation rate than a commercial palladium catalyst supported on alumina.▪
Keywords: Electrospinning; Nanofibres; Hydrogenation; Palladium nanoparticles; Catalytic activity;

Transesterification of sunflower oil over zeolites using different metal loading: A case of leaching and agglomeration studies by María Jesús Ramos; Abraham Casas; Lourdes Rodríguez; Rubí Romero; Ángel Pérez (79-85).
The transesterification of sunflower oil was carried out using three different zeolites (mordenite, beta and X). A methyl ester content of 95.1 wt% was obtained at 60 °C employing zeolite X. The high catalytic activity of zeolite X gives processes competitive advantages over conventional processes based on homogeneous catalysis at the same temperature. ▪The aim of this study was to analyse the catalytic performance of several heterogeneous catalysts in the transesterification of sunflower oil with methanol. In order to characterize the different catalysts, nitrogen adsorption/desorption and CO2 temperature programmed desorption were used. The transesterification of sunflower oil was carried out using three different zeolites: mordenite, beta and X, to determine the influence of the kind of zeolite on the methyl ester production. The influence of the metal incorporation technique was studied using both impregnation and ion-exchange methods. Also, the transesterification reaction was carried out using catalysts with different metal loading. Finally, zeolite X was agglomerated with a binder, sodium bentonite, to study how the presence of a binder could change the catalytic performance of the zeolite. A methyl ester content of 93.5 and 95.1 wt% was obtained at 60 °C employing zeolite X with or without sodium bentonite, respectively. All biodiesel synthesized were characterized using the standard UNE-EN 14214. A complete deactivation study was carried out in order to check the sodium leaching from the catalyst. The results supported the hypothesis of a homogeneous-like mechanism where the alkali methoxide species were leached out.
Keywords: Transesterification; Biodiesel; Zeolites; Binder; Heterogeneous basic catalysis; Leaching;

Heterolytic activation of hydrogen gas: New evidence for Spencer–Yu hypothesis! by Nicolas Faucher; Jean-Christophe Cintrat; Bernard Rousseau (86-89).
Hydrogenolysis of organolithium reagents is described under heterogeneous catalysis in the presence of Pd0. This approach gives details about the H–H bond polarization in the presence of transition metal catalysts.▪Hydrogenolysis or deuterogenolysis of organolithium compounds is described for the first time under heterogeneous catalysis. This work establishes that the carbon–lithium bond can undergo a facile reduction reaction when catalyzed by palladium or platinum catalysts and provides strong evidence for the existence of Pdδ−–Hδ+ species.
Keywords: Deuterium; Hydrogenolysis; Heterogeneous catalysis; Organolithium; Palladium;

The effect of addition of potassium to Pt supported on yttrium-stabilized zirconia (PtYSZ) catalyst for steam reforming of methane, ethane and methane/ethane mixtures was explored. Addition of potassium has a positive effect on preferential steam reforming of methane in mixtures of methane and ethane over Pt/YSZ catalysts. The activity of potassium-modified catalysts increased with time-on-stream during steam reforming of mixtures of methane and ethane, while the ratio of reaction rates of methane and ethane remained constant. Most importantly, it was demonstrated that the presence of potassium prevents competition between methane and ethane during steam reforming. The reaction rate ratio in methane/ethane mixtures is changed from preferential ethane reforming on PtYSZ towards preferential methane conversion as a result of addition of potassium.This study shows that the steam reforming rates of methane and ethane are affected differently by the presence of potassium on supported Pt catalysts. As a result, competition effects in mixtures containing the two hydrocarbons diminished and improved methane conversion was possible.▪
Keywords: Steam reforming; Methane; Ethane; Mixture; Pt; Potassium;

The promotional effect of Ni on the hydrodeoxygenation (HDO) of benzofuran (BF) over reduced Ni–Mo/γ-Al2O3 catalysts was studied. The adsorption characteristics of Al2O3 support, mono-metallic Mo, and bi-metallic Ni–Mo catalysts that were pre-reduced were investigated using the feed molecule (BF) and a probe molecule (NO) as adsorbates. NO was used to probe the coordinatively unsaturated sites (CUS). Three adsorption modes for benzofuran over reduced Al2O3 support, Mo, and Ni–Mo catalysts were proposed that involved OH groups, Brønsted acid sites, and CUS, respectively. Benzofuran molecule adsorbed more strongly on B acid sites and CUS than on OH groups and was activated with weakening of the C–O bond. With increasing catalytic hydrogenation activity (increasing CUS) and/or decreasing hydrogenolysis activity (decreasing acidity), the reaction pathway for benzofuran HDO changes from a hydrogenolysis route to a route that involves saturation of the benzene ring before any heteroatom removal takes place.Three adsorption modes for benzofuran over reduced Al2O3 support, Mo, and Ni–Mo catalysts were proposed that involved OH groups, Brønsted acid sites, and CUS, respectively. With increasing catalytic hydrogenation activity (increasing CUS) and/or decreasing hydrogenolysis activity (decreasing acidity), the reaction pathway for benzofuran HDO changes from a hydrogenolysis route to a route that involves saturation of the benzene ring before any heteroatom removal takes place. ▪
Keywords: Benzofuran hydrodeoxygenation; Reduced Mo and Ni–Mo catalysts; NO adsorption; Benzofuran adsorption;

The action of vanadium over Y zeolite in oxidant and dry atmosphere by Diana Vanessa Cristiano-Torres; Yonnathan Osorio-Pérez; Liliam Alexandra Palomeque-Forero; Luis Ernesto Sandoval-Díaz; Carlos Alexander Trujillo (104-111).
Y zeolite was impregnated with vanadium naphtenate and thermally treated at 720 °C for 5 h in dry air. Calcinated samples were characterized by micropore volume, UV–vis-DRS, cracking of n-butane and isopropylamine decomposition followed by simultaneous DSC–TGA. Results show that in dry air the zeolite is stable even at high vanadium loadings but the metal is able to move on the surface of the catalyst and neutralize acid sites. n-Butane conversion increases with vanadium concentration but this is a result of the metal's dehydrogenation ability. Selectivity to protolytic primary cracking products decreases linearly with vanadium concentration as a result of the neutralization of Brønsted acid sites quantified by the isopropylamine test. Rate of cracking vs. number of acid sites shows that on a unit of time (second) approximately only one in seven thousand acid sites measured by the isopropylamine technique is able to crack n-butane by monomolecular protolytic cracking mechanism. Selectivity to hydride transfer products remains constant with vanadium concentration except at high loadings. Vanadium is able to move on surface and neutralize preferentially acid sites where more energy is released in the reaction with isopropylamine; acid sites strong enough to crack n-butane. Neutralization of acid sites is probably the first step in Y zeolite destruction under conditions predominant in the regenerator of an FCC plant. Pictogram: This drawing represents the possible neutralization of Y zeolite Brønsted acid sites by vanadium species. ▪Y zeolite was impregnated with vanadium naphtenate and thermally treated at 720 °C for 5 h in dry air. Calcinated samples were characterized by micropore volume, UV–vis-DRS, cracking of n-butane and isopropylamine decomposition followed by simultaneous DSC–TGA. Results show that in dry air the zeolite is stable even at high vanadium loadings but the metal is able to move on the surface of the catalyst and neutralize acid sites. n-Butane conversion increases with vanadium concentration but this is a result of the metal's dehydrogenation ability. Selectivity to protolytic primary cracking (PPC) products decreases linearly with vanadium concentration as a result of the neutralization of Brønsted acid sites quantified by the isopropylamine test. Rate of cracking vs. number of acid sites shows that on a unit of time (second) approximately only one in seven thousand acid sites measured by the isopropylamine technique is able to crack n-butane by monomolecular protolytic cracking mechanism. Selectivity to hydride transfer (SHT) products remains constant with vanadium concentration except at high loadings. Vanadium is able to move on surface and neutralize preferentially acid sites where more energy is released in the reaction with isopropylamine; acid sites strong enough to crack n-butane. Neutralization of acid sites is probably the first step in Y zeolite destruction under conditions predominant in the regenerator of an FCC plant.
Keywords: Y zeolite; Vanadium; n-Butane cracking; FCC; Isopropylamine decomposition; Protolytic cracking;

Solvent-free allylic oxidation of cycloolefins over mesoporous CrMCM-41 molecular sieve catalyst at 1 atm dioxygen by Sudhir E. Dapurkar; Hajime Kawanami; Kenichi Komura; Toshirou Yokoyama; Yutaka Ikushima (112-116).
Oxidation of cycloolefins was effectively performed under aerobic (1 atm dioxygen) and mild solvent-free conditions using mesoporous CrMCM-41 molecular sieve catalyst. For instance, Cycloolefins (C5–C7) were selectively oxidized to the corresponding α,β-unsaturated ketones (for example, cyclohexene – 52.2% conversion and 71.2% selectivity) and cycloolefins (C8–C12) were oxidized to epoxides (for example, cis-cyclooctene – 50% conversion and >99% selectivity) at 323–353 K for 24 h.▪Oxidation of cycloolefins was effectively performed under aerobic (1 atm dioxygen) and mild solvent-free conditions using mesoporous CrMCM-41 molecular sieve catalyst. For instance, Cycloolefins (C5–C7) were selectively oxidized to the corresponding α,β-unsaturated ketones (for example, cyclohexene – 52.2% conversion and 71.2% selectivity) and cycloolefins (C8–C12) were oxidized to epoxides (for example, cis-cyclooctene – 50% conversion and >99% selectivity) at 323–353 K for 24 h. The catalytic activity over recycled catalyst remains nearly same.
Keywords: Solvent-free oxidation; Dioxygen; Allylic oxidation; Epoxidation; Catalyst;

Catalytic behavior of hybrid Co/SiO2-(medium-pore) zeolite catalysts during the one-stage conversion of syngas to gasoline by Agustín Martínez; Susana Valencia; Raúl Murciano; Henrique S. Cerqueira; Alexandre F. Costa; Eduardo Falabella S.-Aguiar (117-125).
The initial activity of 10-MR (membered ring) acid zeolites (ZSM-5, MCM-22, ITQ-2, IM-5) with Si/Al ∼15 in hybrid Co/SiO2-zeolite catalysts for in situ isomerization–cracking of FT (Fischer-Tropsch) waxes to branched gasoline-range hydrocarbons is mainly governed by the external acidity, pointing out to diffusional limitations. Deactivation rate, by contrast, is related to the amount and nature of “coke” and depends on zeolite structure rather than on acidity.▪The catalytic properties of 10-MR (membered ring) zeolites (ZSM-5, MCM-22, IM-5, ITQ-2, all with a similar Si/Al ratio of ca. 15) in hybrid Co/SiO2-zeolite catalysts for the direct conversion of syngas to mainly high-octane gasoline-range hydrocarbons has been studied under typical Fischer-Tropsch (FT) conditions: 250 °C, 2.0 MPa, and H2/CO = 2. Special emphasis has been given to the deactivation behavior and the characterization of the amount and nature of the carbonaceous deposits formed by a combination of techniques (elemental analysis, TGA (thermogravimetric analyses), GC–MS, and DR (diffuse reflectance) UV–vis spectroscopy). The presence of the medium-pore zeolite increases the gasoline yield by about 20–50%, depending on the particular zeolite, and enhances the formation of branched products with respect to the base Co/SiO2 catalyst, which is explained by the promotion of isomerization and cracking of long-chain (C13+) n-paraffins formed on the FT component. The initial zeolite activity is mostly determined by the surface acidity rather than by the total amount of Brønsted acid sites, pointing out to the existence of limitations for the diffusion of the long-chain n-paraffins through the 10-MR channels under FT conditions. Thus, ITQ-2 bearing the largest surface area presents the highest initial yield of branched gasoline-range products, followed by ZSM-5, IM-5, and MCM-22. All zeolites experience a loss of activity with TOS, particularly during the initial reaction stages. This deactivation is governed by the morphological and structural properties of the zeolite, which finally determine the amount and location of the coke species, and not by the acidity.
Keywords: Syngas conversion; Hybrid catalyst; Coke nature; GC–MS; UV–vis spectroscopy; IM-5 zeolite;

Supported Rh catalysts for methane partial oxidation prepared by OM-CVD of Rh(acac)(CO)2 by V. Dal Santo; C. Mondelli; V. De Grandi; A. Gallo; S. Recchia; L. Sordelli; R. Psaro (126-133).
Supported Rh catalysts, prepared by OM-CVD of Rh(acac)(CO)2, showed good performances in hydrogen/syngas production by the methane catalytic partial oxidation reaction. During ageing an extensive reconstruction occurs consisting in a sintering of Rh isolate sites to metal particles but without large increase in mean particles size. Catalytic performances were found to be dependent on the support material. ▪The organometallics chemical vapour deposition (OM-CVD) technique, using Rh(acac)(CO)2 as a precursor, was employed for the preparation of heterogeneous Rh catalysts supported on low surface area refractory oxides (α-Al2O3, ZrO2, MgO and La2O3). Prepared systems were tested in the methane catalytic partial oxidation (CH4-CPO) reaction in a fixed bed reactor and compared to a reference catalyst prepared from impregnation of Rh4(CO)12.Catalysts supported on Al2O3, ZrO2 and MgO show better or comparable performances with respect to the reference system.Complete decomposition of Rh precursor during formation of the metal phase under reductive conditions was investigated by TPRD and confirmed by infrared and mass spectrometry data.Supported Rh phase was characterized by CO and H2 chemisorption, CO-DRIFT spectroscopy and HRTEM microscopy in fresh and aged selected samples. Rh(I) isolated sites and Rh(0) metal particles were found on fresh catalysts; after ageing an extensive reconstruction occurs mainly consisting in a sintering of Rh isolate sites to metal particles but without large increase in mean particles size.Catalytic performances and Rh species balance were found to be dependent on the support material.
Keywords: OM-CVD; Rh catalysts; CH4 CPO; Rh(acac)(CO)2; Syngas; Hydrogen production;

Co(salen) complexes were encapsulated in zeolite Y by a “ship in bottle” method. Such encapsulated complexes were applied as catalysts for the synthesis of methyl N-phenylcarbamate by oxidative carbonylation of aniline. The conversion of 67.1% and the selectivity of 77.3% in the reaction were obtained with Co(salophen)(OH)2–Y. The catalyst could be recycled at least five times without significant loss of its catalytic activity.▪A green process for the synthesis of methyl N-phenylcarbamate (MPC) by the oxidative carbonylation of aniline was studied. In this process, Co(salen) complexes were successfully encapsulated in zeolite Y by a flexible ligand method. The heterogeneous catalysts were characterized by AAS, BET, IR, TGA, XRD and XPS. The catalytic activities of the encapsulated catalysts and their homogeneous analogues were examined in the oxidative carbonylation of aniline to MPC. Under the conditions of aniline (11 mmol), encapsulated catalyst (0.5 g), KI (0.365 g), CO/O2 ratio 9:1, 4 MPa, 170 °C, 3 h, Co(salophen)(OH)2–Y catalyst shows the highest activity with the conversion of 67.1% and the selectivity of 77.3%. Co(salophen)(OH)2–Y could be recycled at least five times and no significant loss of catalytic activity was observed.
Keywords: Salen; Encapsulation; Carbamate; Oxidative carbonylation;

Immobilized iron oxides on silica matrixes in fluidized bed reactors, including SiG1, SiG2, C1, and the commercial catalyst FeOOH, were used in the catalytic decomposition of H2O2 and the catalytic degradation of phenol. The iron oxides were characterized using XRD, SEM, N2-sorption, and elucidation of the kinetics of dissolved iron by oxalic acid in dark surroundings. SiG1 and SiG2 exhibit higher catalytic activities in phenol degradation. ▪Immobilized iron oxides on silica matrixes in fluidized bed reactors, including SiG1, SiG2, C1, and the commercial catalyst FeOOH, were used in the catalytic decomposition of H2O2 and the catalytic degradation of phenol. They were characterized using XRD, SEM, N2-sorption, and elucidation of the kinetics of dissolved iron by oxalic acid in dark surroundings. XRD patterns reveal that SiG1, SiG2, and C1 exhibit amorphous structures, and FeOOH exhibits the poor crystallinity of goethite. The SEM images reveal that the surfaces of all the iron oxides are smooth and that the iron oxides are aggregated by the iron oxide floc. The N2-sorption isotherm indicates that SiG1 and SiG2 are non-porous materials, and that C1 and FeOOH are typical type II and typical type IV materials, respectively. A kinetic model for iron dissolved by oxalic acid is established. The order of apparent first-order dissolution rate constants (k c) is SiG1 > SiG2 > FeOOH ∼ C1. The immobilized iron oxides, SiG1 and SiG2, are weakly bonded to the support (silica sand) in the presence of oxalic acid. The decomposition of H2O2 follows pseudo-first-order kinetics. The number of active sites for the decomposition of H2O2 is similar among all iron oxides at a particular k app (1.8 × 10−3  min−1). There are no interactions between phenol and iron oxides in the absence of hydrogen peroxide at pH 4. SiG1 and SiG2 exhibit much higher catalytic activities in phenol degradation than either C1 or FeOOH. The reactivity of iron oxides in catalyzing the phenol degradation by H2O2 relates to the tendency of iron to be dissolved by oxalic acid. The intermediates of phenol degradation, such as catechol and oxalic acid, promote the dissolution of iron from SiG1 and SiG2 by reductive and non-reductive pathways and lower the pH values. The catalyses of SiG1 and SiG2 involve heterogeneous and homogeneous reactions.
Keywords: Catalyst; Phenol; Iron oxides; Fenton; Fluidized bed reactor;

Role of platinum-like tungsten carbide as cocatalyst of CdS photocatalyst for hydrogen production under visible light irradiation by Jum Suk Jang; Dong Jin Ham; Narayanan Lakshminarasimhan; Won yong Choi; Jae Sung Lee (149-154).
The WC/CdS composite photocatalyst fabricated via a precipitation/hydrothermal method showed excellent photocatalytic activity, comparable to that of conventional Pt/CdS, for hydrogen production from water under visible light. Platinum-like WC provides active sites for proton reduction and causes fast diffusion of photoelectrons generated from CdS toward WC, leading to high photocatalytic activity of hydrogen production.▪To investigate the role of platinum-like tungsten carbide as a cocatalyst for photocatalytic hydrogen production under visible light irradiation, we fabricated for the first time a composite material consisting of WC and CdS by a precipitation/hydrothermal method. The composite prepared by this procedure consisted of well-dispersed WC and CdS, as confirmed by TEM mapping analysis. The WC/CdS composite photocatalyst exhibited a high rate of hydrogen production, comparable to that of Pt/CdS, under visible light irradiation (λ  ≥ 420 nm) from water containing sulfide and sulfite ions as hole scavengers. Like Pt cocatalyst loaded on the surface of CdS, WC provides active sites for proton reduction and causes fast diffusion of photoelectrons generated from CdS toward WC, leading to high photocatalytic activity of hydrogen production.
Keywords: WC; Photocatalysts; Cocatalyst; Hydrogen production;

We report here that the molybdenum and vanadium mixed crystal oxide is an effective heterogeneous catalyst for the selective oxidation of benzyl alcohols to benzaldehydes under mild condition with molecular oxygen as oxidant and without additive. Competitive tests revealed that hydride transfer may be involved in the reaction course. Kinetic analysis shows that the oxidation of benzyl alcohol exhibits first-order dependence on substrate concentration and on catalyst concentration.▪Novel crystalline Mo―V―O oxide was employed as the catalyst in the aerobic oxidation of alcohols to the corresponding carbonyl compounds. Reactions were mainly conducted at 353 K in pure oxygen or air (1 atm). The selectivities for benzaldehydes were more than 95% in all cases. The conversions of benzyl alcohols varied from 10% to 99% depending on the substituent. A Hammett plot gave a moderate ρ-value of −0.249 (r 2  = 0.98), suggesting that the reaction processes may involve hydride abstraction. The oxidation of primary alkanols afforded aldehydes, and secondary alcohols were mainly dehydrated to olefins. It was found that the conversion of linear alkanols decreased with the length of alkanols. Kinetic analysis showed that catalytic reaction rate was first-order dependent on the concentrations of substrate and of catalyst. The apparent activation energy was estimated to be 45.7 kJ mol−1. Catalytic reactions took place on the 6- or 7-member rings on the ab basal plane, where highly dense unsaturated metal cation centers and oxygen anion might serve as catalytic active sites.
Keywords: Mo―V―O crystalline; Alcohol oxidation; Oxygen; Heterogeneous catalysis; Liquid phase;

Catalytic decomposition of methane over a wood char concurrently activated by a pyrolysis gas by A. Dufour; A. Celzard; V. Fierro; E. Martin; F. Broust; A. Zoulalian (164-173).
The catalytic activity of a wood char towards CH4 decomposition in a pyrolysis gas was investigated in a fixed bed reactor for maximising hydrogen production from biomass gasification. Wood char is suggested to be the cheapest and greenest catalyst for CH4 conversion as it is directly produced in the pyrolysis facility. The conversion of methane reaches 70% for a contact time of 120 ms at 1000 °C. Because steam and CO2 are simultaneously present in the pyrolysis gas, the carbon catalyst is continuously regenerated. Hence the conversion of methane quickly stabilises. Such a phenomenon is shown to be possible through the oxidation of the char by CO2 and H2O at high temperature, which prevents the blocking of the mouth of pores by the concurrent pyrolytic carbon deposition. In the experimental conditions, oxygenated functional surface groups are continuously formed (by steam and CO2 oxidation) and thermally decomposed. The active sites for CH4 chemisorption and decomposition are suggested to be the unsaturated carbon atoms generated by the evolution of the oxygenated functions at high temperature.
Keywords: Hydrogen production; Biomass gasification; Methane decomposition; Carbon-based catalyst; Activation; Surface properties;

A synergic function exists in the hybrid catalyst system HCOONa/Cu–MgO to promote the catalytic activity in the reaction from syngas to synthesizing methanol. Moreover, during the formation of CO2, loss of CO3 2− and appearance of HCO3 suppressed the catalytic activity. In addition, H2-chemisorption and CO-chemisorption abilities of Cu/MgO catalysts based on various phase structures exhibited remarkable influences on the catalytic activity. ▪A novel hybrid catalyst system containing alkali formate and Cu/MgO–Na was developed to synthesize methanol from syngas via ethyl formate in a slurry reactor. The results exhibited that high CO conversion (>80%) and methanol selectivity (∼90%) with a mass space velocity of 1800 L(STP)/(h kg) were achieved at a low temperature of 433 K and at 5.0 MPa. A synergic function between HCOOM (M = Li, Na, K, Rb and Cs) and Cu/MgO–Na was in existence for promoting the reaction performance, in which sodium formate showed the optimizing synergy with Cu/MgO–Na catalyst. In addition, the nature of the solid copper catalysts also had a remarkable influence on the catalytic activity.
Keywords: Methanol synthesis; Ethyl formate; Alkali formate; Cu/MgO–Na; Synergic function; Chemisorption;

The CoNiB and PVP-stabilized CoNiB catalysts were prepared by chemical reduction with NaBH4. They were significantly more active than NiB and CoB in the hydrogenation of furfural, crotonaldehyde and citral. The most active catalyst PVP(2)-CoNiB(0.5) could selectively hydrogenate citral to citronellal at a low reaction temperature of 30 °C, with a good citronellal selectivity of about 86%. ▪CoNiB and polymer polyvinylpyrrolidone (PVP)-stabilized CoNiB (PVP-CoNiB) catalysts were prepared by chemical reduction with NaBH4. They were characterized and examined for their catalysis in the hydrogenation of unsaturated aldehydes. CoNiB and PVP-CoNiB catalysts were characterized by X-ray diffraction as amorphous structures and by transmission electron microscopy as having particle sizes in the range 3.5–7 nm – smaller than those of NiB (7–15 nm) and CoB (5–10 nm). CoNiB catalysts were significantly more active than NiB and CoB in the hydrogenations of furfural, crotonaldehyde and citral, and the PVP-CoNiB catalysts were significantly more active than CoNiB. The catalytic properties of CoNiB and PVP-CoNiB catalysts during the selective hydrogenations of crotonaldehyde and citral were similar to those of NiB, but different from those of CoB. The conjugated C=C bonds in crotonaldehyde and citral were preferentially reduced to form butyraldehyde and citronellal. PVP-CoNiB could hydrogenate citral to citronellal at a low reaction temperature of 30 °C.
Keywords: Chemical reduction; Nanoparticle; CoNiB; Hydrogenation; Unsaturated aldehydes;

Alkylation of isobutene with 2-butene using composite ionic liquid catalysts by Ying Liu; Ruisheng Hu; Chunming Xu; Haiquan Su (189-193).
A composite ionic liquid was used as an acid catalyst for the liquid phase alkylation of isobutane and 2-butene. The main product obtained was trimethylpentane (>85 wt.%) and the research octane numbers of the alkylates was 98–101. In the ionic liquid sample, a composite anion [AlCl4CuCl] was detected by means of ESI-MS. This new species was also confirmed by 27Al NMR and FT-IR characterizations. The effects of anion composition on the product distribution have been investigated. The composite anion plays important roles in improving alkylate quality.A composite ionic liquid was used as an acid catalyst for the alkylation of isobutane and 2-butene. The research octane number of alkylate obtained was 98–101. The effects of anion composition on the product distribution have been investigated. The composite anion ([AlCl4CuCl]) plays important roles in improving alkylate quality.▪
Keywords: Alkylation; Isobutane; Composite ionic liquid; Chloroaluminate;

The catalytic effects of impregnated nickel and iron via naphthenates on an FCC catalyst followed by steam deactivation were studied after oxidative and reductive treatments at 760 °C.The dehydrogenation activity of nickel was found to be close to the dehydrogenation activity of vanadium for the FCC catalyst used in this study and not several times higher than that of vanadium as is often reported.Hydrogen yield for FCC samples impregnated with 3000 ppm Ni or Fe followed by deactivation (Ni-ox and Fe-red) or deactivation and reductive treatment (Ni-red and Fe-red).▪The catalytic effects of nickel and iron deposited on an FCC (fluidized catalytic cracking) catalyst via metal naphthenates were studied in a micro activity test (MAT) unit after both oxidative and reductive treatments of the catalyst samples.The dehydrogenation activity of nickel was found to be close to the dehydrogenation activity of vanadium – and not several times higher than that of vanadium as is often reported – when deposited on the commercial FCC catalyst used in this study followed by steam deactivation (oxidative treatment) at 760 °C. However, the dehydrogenation activity of nickel was significantly intensified after post-treatment with a CO/N2 mixture at this temperature (reductive treatment).The results show that iron did not have a dehydrogenation activity after steaming, but had a significant dehydrogenation activity after steaming when followed by exposure to the CO/N2 mixture at 760 °C. The results indicate that the presence of deposited iron was inducing an additional catalytic cracking activity for the FCC catalyst.It was observed that co-impregnation of equal loadings of nickel, iron and vanadium on the FCC catalyst led to a considerably higher dehydrogenation activity than could be expected from the catalytic behaviour of the separate elements. The dehydrogenation activity was however slightly reduced by the reductive treatment as the reduced dehydrogenation activity from the lower oxidation state of vanadium (V3+) more than compensated the increased dehydrogenation activity of iron and nickel. A slightly increased gasoline production after the reductive treatment of the co-impregnated sample was a result of the increased production of gasoline from the FCC catalyst itself, which more than compensated for the reduced gasoline production from nickel.
Keywords: FCC; Nickel; Iron; Vanadium; Dehydrogenation; MAT; Resid cracking;

TiO2–SiO2 monolithic aerogels were homogeneously prepared using sol–gel method. Critical point of drying time of TiO2–SiO2 gels with ethanol was studied at 30–120 min. Subsequently, the gels were dried with supercritical ethanol, resulting in amorphous aerogels that crystallized following heat treatment at 550 °C for 1–5 h. TiO2–SiO2 gel should be supercritical dried for 30 min from economic point of view and heat treated for 5 h. SEM images of representative TiO2–SiO2 aerogel morphologies were monolithic aerogel. ▪TiO2–SiO2 monolithic aerogels were homogeneously prepared using sol–gel method. Critical point of drying of TiO2–SiO2 gels with ethanol was studied for 30, 60, 90 and 120 min. Subsequently, the gels were dried with supercritical ethanol, resulting in amorphous aerogels that crystallized following heat treatment at 550 °C from 1 to 5 h. The TiO2–SiO2 aerogels were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM) and surface area measurements. The molar ratio of SiO2:TiO2 was 6 and the synthetic strategy revealed that TiO2–SiO2 aerogel, had a surface area ∼868 m2/g, particle size ∼40 nm, density ∼0.17 g/cm3 and 80% porosity. The finding indicated that from economic point of view, TiO2–SiO2 gel should be supercritical dried for 30 min and heat-treated for 5 h. The TiO2–SiO2 aerogel monoliths photocatalyst synthesized using sol–gel method provided insight into the characteristics that make a photocatalyst material well-suited for photodegradation of phenol and cyanide in an industrial waste stream containing Cl, S2− and NH4 +. Interestingly, after multiple reuse cycles (i.e. ≥7), photodegradation systems with regenerated photocatalyst showed a slightly decreasing of photoactivity ∼2–4%. The overall kinetics of photodegradation of either phenol or cyanide using TiO2–SiO2 aerogel photocatalyst was found to be of first order.
Keywords: TiO2–SiO2; Aerogels; Monolithic; Photodegradation; Real wastewaters;