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Applied Catalysis A, General (v.381, #1-2)

Editorial Board (pp. co2).

Contents (pp. iii-xi).

Catalytic features of Rh and Ni supported catalysts in the steam reforming of glycerol to produce hydrogen by V. Chiodo; S. Freni; A. Galvagno; N. Mondello; F. Frusteri (pp. 1-7).

Glycerol steam reforming on Rh and Ni supported catalyst was investigate in view to produce syn-gas to feed a high temperature fuel cell system. Rh/Al2O3 catalyst resulted to be more active and stable than Ni catalysts but independently from the experimental conditions investigated, the reaction is affected by coke formation mainly promoted by the large presence of olefins formed by glycerol decomposition.Glycerol steam reforming on Rh and Ni supported catalyst was investigate in view to produce syn-gas to feed a high temperature fuel cell system (SOFC-MCFC). Results obtained revealed that glycerol is subjected to pyrolysis phenomena and at temperature higher than 720K drastically decomposes before to reach the catalyst surface. Rh/Al₂O₃ catalyst resulted to be more active and stable than Ni supported catalysts but independently from the catalyst used (Rh or Ni) and temperature investigated, the reaction is affected by coke formation mainly promoted by the large presence of olefins formed by glycerol thermal decomposition. Even if for thermodynamic reasons the hydrogen production should be favored by operating at high temperature, results obtained demonstrate that it is more convenient to operate at temperature not higher than 923K, since higher reaction temperature promotes the formation of encapsulated carbon which negatively reflects on catalyst stability.

Keywords: Rh and Ni catalysts; H; ₂; production; Glycerol steam reforming; Coke formation

Oxidation of benzyl alcohol and styrene using H₂O₂ catalyzed by tetraazamacrocycle complexes of Cu(II) and Ni(II) encapsulated in zeolite-Y by Vipin Kumar Bansal; Pompozhi Protasis Thankachan; Rajendra Prasad (pp. 8-17).

Neat Cu(II) and Ni(II) tetraazamacrocycle complexes have been synthesized and encapsulated in the supercages of zeolite-Y. Their catalytic activity towards solvent free oxidation of benzyl alcohol and styrene has also been studied. Effects of various parameters like temperature, amount of catalyst, amount of oxidant and reaction time on the overall conversion have been investigated.Encapsulation of 7,16-diacetyl[M{Me₄(Bzo)₂[14]tetraeneN₄}], {M=Cu(II) and Ni(II)} tetraazamacrocycle complexes in the cavity of Zeolite-Y by the template synthesis method has been described. These complexes have been characterized using various physico-chemical techniques viz., spectroscopic (electronic and IR) studies, thermal analysis, metal analysis, field emission scanning electron micrographs and X-ray powder diffraction patterns. These encapsulated tetraazamacrocycle complexes have been used as a heterogeneous catalyst for the oxidation of styrene and for the solvent free oxidation of benzyl alcohol using hydrogen peroxide as oxidant. The solvent free catalyzed oxidation of benzyl alcohol catalyzed by 7,16-diacetyl[Cu{Me₄(Bzo)₂[14]tetraeneN₄}]-NaY gives benzaldehyde as the major product, while that of styrene gives benzaldehyde and styrene oxide as major oxidation products when 7,16-diacetyl[Ni{Me₄(Bzo)₂[14]tetraeneN₄}]-NaY is used as catalyst.

Keywords: Zeolite encapsulation; Oxidation; Benzyl alcohol; Styrene; Heterogeneous catalysis; Tetraazamacrocycle

Thermodynamic and experimental study of the partial oxidation of a Jet A fuel surrogate over molybdenum dioxide by Oscar Marin-Flores; Timothy Turba; Joe Breit; M. Grant Norton; Su Ha (pp. 18-25).

This figure describes a ternary phase diagram Mo–O–C at 850°C and 1atm showing the minimized Gibbs free energy in a color-scale. The results of our calculations indicate that maximum stability is attained by those regions where solid MoO₂, solid Mo₂C, and liquid MoO₃ are present and coexist with a gas-phase consisting basically of CO₂.A combination of thermodynamic calculations and experimental results was used to investigate the activity and stability of molybdenum dioxide (MoO₂) as a catalyst for the partial oxidation of aviation jet fuels. The surrogate fuel used in this study was n-dodecane. Our results indicate that the stability window for MoO₂ is strongly affected by the O₂/C molar ratio. Thus, the formation of elemental carbon on the catalyst structure can be prevented using O₂/C ratios higher than 0.5. However, O₂/C ratios higher than 1.0 enhance the formation of MoO₃, which is volatile and leads to the irreversible loss of catalytic material. The activity was measured at 850°C and 1atm and our findings indicate that, within the stability window determined earlier, the production rates of H₂ and CO can reach values as high as 78% and 92%, respectively. The coking resistance of MoO₂ was compared with that of a commercial nickel catalyst by performing activity tests under coke-promoting conditions. Energy dispersive X-ray analysis of the spent samples shows that MoO₂ is much more resistant to deactivation by coking than the commercial nickel catalyst. Based on these results, MoO₂ appears to be a promising catalyst for the partial oxidation of jet fuels.

Keywords: Thermodynamic calculations; Molybdenum dioxide; Partial oxidation; Aviation jet fuels; n; -dodecane; Coking resistance

Toluene oxidation on chromium- and copper-modified SiO₂ and SBA-15 by M. Popova; Á. Szegedi; Z. Cherkezova-Zheleva; A. Dimitrova; I. Mitov (pp. 26-35).

It was found that the type of the generated metal oxide species depends on the type of support used. The mesoporous support favors the formation of tetrahedrally coordinated copper and chromium oxide species which are highly active in toluene oxidation. The appropriate metal oxide content in order to obtain highly active catalyst is 3wt.% chromium and 7wt.% copper supported on SBA-15.Copper- and chromium-modified SiO₂ and SBA-15 materials, prepared by a wet impregnation technique, were investigated using X-ray diffraction (XRD), N₂ physisorption, temperature-programmed reduction (TPR-DTG), temperature-programmed oxidation (TPO-DTG), UV–vis diffuse reflectance EPR and FT-IR spectroscopy. Their catalytic behavior was studied in the total oxidation of toluene. The supports had decisive role on the nature and dispersion of the formed metal species. The presence of chromium and copper species, mainly in tetrahedral coordination, was observed for the modified SBA-15 samples, while a significant amount of metal oxides is registered for the modified SiO₂ ones. More finely dispersed chromium and copper species were formed on the bi-component copper- and chromium-containing SBA-15 catalysts and possessed higher activity in total oxidation of toluene. The optimal metal oxide content for highly active and selective SBA-15-supported catalyst was found to be 3wt.% chromium and 7wt.% copper.

Keywords: Copper- and chromium-modified SiO; ₂; and SBA-15; Total oxidation of toluene

Effect of Ni incorporation into goethite in the catalytic activity for the oxidation of nitrogen compounds in petroleum by Wladmir F. de Souza; Iara R. Guimarães; Luiz C.A. Oliveira; Amanda S. Giroto; Mário C. Guerreiro; Carmen L.T. Silva (pp. 36-41).

The successive hydroxylation of quinoline during this oxidation strongly suggests that highly reactive hydroxyl radicals are generated during the reaction involving H₂O₂ on the Ni-goethite grain surface, also confirming that these materials are efficient heterogeneous Fenton catalysts.Samples of Ni-doped goethites were prepared and characterized by Mössbauer spectroscopy, IV, XRD, TPR and BET surface area measurements. Mössbauer data evidenced the incorporation of Ni²⁺ in the goethite structure, and this cation-doping caused a significant decrease of the chemical reduction temperature in the TPR process. The catalytic behavior of these Fe1−_xNi_xOOH materials was investigated for the H₂O₂ decomposition to O₂ and the oxidation of quinoline. The successive hydroxylation of quinoline during this oxidation strongly suggests that highly reactive hydroxyl radicals are generated during the reaction involving H₂O₂ on the Ni-goethite grain surface, also confirming that these materials are efficient heterogeneous Fenton catalysts.

Keywords: Goethite; Nickel; Oxidation; Petroleum

SBA-15-supported gold nanoparticles decorated by CeO₂: Structural characteristics and CO oxidation activity by L. Escamilla-Perea; R. Nava; B. Pawelec; M.G. Rosmaninho; C.L. Peza-Ledesma; J.L.G. Fierro (pp. 42-53).

A series of Au catalysts supported on SBA-15 substrate modified with variable amounts of CeO₂ (0, 5, 10, 15 and 20wt%) were prepared by the deposition–precipitation method. Catalytic activity was found to increase with the CeO₂ loading even though this increase was not linear: the highest activity was found for the catalyst loaded with 10wt% CeO₂. This behavior is explained in terms of the quantity of Au⁺ species present on the surface of catalysts. The importance of both Au⁺ and Au⁰ species on the catalytic performance in the target reaction is discussed.The influence of SBA-15 substrate modified with CeO₂ on the catalytic response of supported gold catalysts in the CO oxidation reaction was investigated. The mesoporous CeO₂/SBA-15 materials (5, 10, 15 and 20wt% of CeO₂) were prepared by incipient wetness impregnation of synthesized SBA-15 substrate whereas the supported gold catalysts were prepared by deposition–precipitation method. The dried Au/SBA-15 and Au/CeO₂/SBA-15 catalysts were characterized by elemental analysis (EDX), N₂ adsorption–desorption isotherms, X-ray diffraction (XRD), UV–vis diffuse reflectance spectroscopy (UV–vis DRS), high resolution transmission electronic microscopy (HRTEM) and X-ray photoelectron spectroscopy (XPS) and their catalytic activity was investigated by the temperature-programmed CO oxidation reaction performed in temperature range 26–205°C. Catalytic activity was found to increase with the CeO₂ loading even though this increase was not linear: the highest catalytic activity was observed for the catalyst loaded with 10wt% CeO₂. This result was explained in terms of the combined effects of the higher stability of gold particles on the support. It was found that the Au nanoparticles in the CeO₂/SBA-15 substrates could be stabilized more efficiently than those on Ce-free SBA-15 material. For the Ce-containing catalysts, a superior performance of the Au/10%CeO_x/SBA-15 catalyst was related to multiple factors such as (i) highest dispersion of Au species on the support surface (by XPS and HRTEM), (ii) highest surface exposure of the Au δ⁺ species (by XPS), and (iii) probably a synergetic effect between the gold nanoparticles and the CeO₂ nanoparticle size (by XRD, UV–vis and HRTEM).

Keywords: Gold nanoparticles; Gold catalysts; CeO; ₂; /SBA-15 supports; CO oxidation

Enhanced Pt stability in MO₂ (M=Ce, Zr or Ce_0.9Zr_0.1)-promoted Pt/C electrocatalysts for oxygen reduction reaction in PAFCs by Q. He; S. Mukerjee; R. Zeis; S. Parres-Esclapez; M.J. Illán-Gómez; A. Bueno-López (pp. 54-65).

PtMO₂/C (M=Ce, Zr, Ce_0.9Zr_0.1) electrocatalysts were prepared towards improving the sintering and corrosion resistance under the severe conditions of the oxygen reduction reaction (ORR) in PAFCs (85%H₃PO₄, 110°C). MO₂ hindered sintering of Pt nanoparticles significantly during long term chronoamperometry test, and the best results were obtained with the mixed oxide (Pt Ce_0.9Zr_0.1O₂/C).Well dispersed PtMO₂/C (M=Ce, Zr, Ce_0.9Zr_0.1) electrocatalysts were prepared towards improving the sintering and corrosion resistance during the oxygen reduction reaction (ORR) in phosphoric acid fuel cells PAFCs. Marginally better kinetics performance can be ascribed to the promoting effect of the metal oxides. However, fairly close Tafel slope values for ORR on PtMO₂/C catalysts in high overpotential region and low overpotential region indicate that metal oxides preserve Pt active sites and prevent the Pt surface from oxidation. Electrochemical surface area (ECA) measurement, polarization curves measurement, X-ray Diffraction (XRD) patterns and transmission electronic microscopy (TEM) images were taken on Pt/C and PtMO₂/C electrocatalysts before and after long term chronoamperometry tests. These experiments showed that the incorporation of metal oxides (MO₂) hindered sintering of Pt nanoparticles significantly. Formation of a core–shell structure and an unusual passivation phenomenon pertinent to mixed oxides are proposed to explain the excellent stability of PtCeZrO₂/C in an environment mimicking real operation conditions in phosphoric acid fuel cells (PAFCs).

Keywords: Abbreviations; DHE; dynamic hydrogen electrode; CVs; cyclic voltammograms; ECA; electrochemical active surface area; EDS; energy dispersive X-ray analyser; GDL; gas diffusion layer; ORR; oxygen reduction reaction; PAFC; phosphoric acid fuel cells; PEMFCs; proton exchange membrane fuel cells; RDE; rotating disk electrode; TEM; transmission electron microscopy; TWC; three way catalysts; XRD; X-ray diffractionPAFCs; ORR; Platinum; Metal oxides; Ceria; Ceria-Zirconia

Mechanistic aspects of the Andrussow process over Pt-Rh gauzes. Effect of gauze morphology and oxygen coverage on primary O₂–NH₃–CH₄ interactions by V.A. Kondratenko; G. Weinberg; M.-M. Pohl; D.S. Su (pp. 66-73).

The general scheme of product formation in the oxidative coupling of methane and ammonia does not depend on the extent of restructuring of commercial Pt-Rh gauzes having been applied for different times on-stream in the Andrussow process.Primary O₂–NH₃–CH₄ interactions in the Andrussow process were investigated in the temporal analysis of products (TAP) reactor over three commercial Pt-Rh gauzes having been applied for different times on-stream in this reaction (fresh, activated and spent catalysts). The gauzes were characterized by scanning electron microscopy combined with energy dispersive X-ray analysis. It was established that they underwent severe morphological changes including deposition of various impurities with increasing time on-stream. Content and type of these impurities possess local variations. However, the near-to-surface Pt/Rh ratio of the deposit-free areas does not change with time on-stream. These areas are strongly faceted on the spent Pt-Rh gauze. Despite the gauzes differ in their morphology and in the content of impurities, the overall scheme of HCN production via oxidative coupling of CH₄ and NH₃ is valid for all the gauzes studied. Nitric oxide primarily formed via ammonia oxidation reacts further with methane and ammonia yielding hydrogen cyanide and nitrogen, respectively. The formed HCN is consecutively converted to N₂. The surface restructuring, coverage by oxygen species and/or the presence of iron oxide influence the interplay between the reaction pathways leading to HCN and its further transformations.

Keywords: Hydrogen cyanide; SEM; EDX; Pt-Rh gauze; Restructuring; TAP; Isotopes

Mechanistic aspects of the Andrussow process over Pt–Rh gauzes. Pathways of formation and consumption of HCN by V.A. Kondratenko (pp. 74-82).

The ability of three Pt–Rh gauzes for HCN formation via coupling of CH₄ with NH₃ or with NO and for oxidative and non-oxidative HCN conversion was compared considering their morphological differences.Reaction pathways governing HCN selectivity in the oxidative coupling of methane and ammonia were investigated over three commercial Pt–Rh gauzes (fresh, activated, and spent) in the temporal analysis of products reactor with submillisecond-time resolution using isotopic traces. These gauzes differed in the extent of reaction-induced restructuring as well as impurity content. The ability of the gauzes to form HCN in the dual interactions of CH₄ with NH₃ or NO was compared considering the morphological differences of the gauzes. It was found that the progressive structural changes increased the gauze activity for methane conversion and facilitate the stabilization of methane fragments on the catalyst surface, but did not influence significantly the surface residence time of N-containing species. The well-known increase in HCN selectivity within first hours on-stream in the Andrussow process was suggested to be likely due to restructuring-induced stabilization of surface methane fragments. The decrease in the HCN selectivity after a stable phase of operation is mainly related to consecutive oxidation of HCN over iron oxide accumulated on the catalyst surface under industrial conditions of the Andrussow process.

Keywords: Hydrogen cyanide; Mechanism; Pt–Rh gauze; TAP-2

n-Butane dehydrogenation on Pt, PtSn and PtGe supported on γ-Al₂O₃ deposited on spheres of α-Al₂O₃ by washcoating by Adriana D. Ballarini; Patricia Zgolicz; Irene M.J. Vilella; Sergio R. de Miguel; Alberto A. Castro; Osvaldo A. Scelza (pp. 83-91).

The catalytic performance of Pt, PtSn and PtGe supported on γ-Al₂O₃ prepared by washcoating of spheres of α-Al₂O₃ is studied in the n-butane dehydrogenation. PtSn(0.5)/γ-A/α-A showed the best catalytic performance (activity, selectivity to all butenes and high stability) and show low electronic interaction between the two metals, with a surface segregation of Sn and oxidized Sn stabilized on the support.Display OmittedIn this paper the catalytic performance of Pt, PtSn and PtGe catalysts supported on γ-Al₂O₃ (γ-A) prepared by washcoating of spheres of α-Al₂O₃ (α-A) is studied in the n-butane dehydrogenation. For this purpose, the effect of the addition of Sn (0.3 and 0.5wt.%) and Ge (0.18 and 0.3wt.%) to Pt (0.3wt.%) on the activity, selectivity and the catalytic stability was analyzed. The catalyst characterization was carried out by using cyclohexane dehydrogenation (CHD) and cyclopentane hydrogenolysis (CPH) reactions, and also temperature programmed reduction (TPR), H₂ chemisorption, X-ray photoelectron spectroscopy (XPS) and scanning electronic microscopy (SEM). Results show that important advances in the development of these catalysts were obtained. In this sense the PtSn(0.5)/γ-A/α-A catalyst showed the best catalytic performance (activity, selectivity to all butenes and high stability) in n-butane dehydrogenation reaction. Results showed a different composition of the metallic phase according to the nature of the second metal (Sn or Ge). In fact, PtSn catalysts show a low electronic interaction between the two metals, with a surface segregation of Sn and oxidized Sn stabilized on the support. On the other hand, PtGe catalysts present strong PtGe interactions with probable alloys formation.

Keywords: Washcoating of spheres of α-Al; ₂; O; ₃; with γ-Al; ₂; O; ₃; layers; Bimetallic PtSn and PtGe catalysts; Characterization of catalysts

Magnetic properties and catalytic performance of iron-containing mesoporous molecular sieves by Verónica R. Elías; Marcos I. Oliva; Silvia E. Urreta; Silvia P. Silvetti; Karim Sapag; Azucena M. Mudarra Navarro; Sandra G. Casuscelli; Griselda A. Eimer (pp. 92-100).

The synthesis of Fe-containing mesoporous catalysts by wet impregnation and further reduction treatment was reported. Their magnetic behavior and catalytic performance were tested in the cyclohexene oxidation with H₂O₂.Fe-containing mesoporous molecular sieves were synthesized by the wet impregnation method with two different metallic loadings. The resulting iron oxide/silica composites were then submitted to a reduction treatment for 6h at 873K, under H₂ flow. The microstructure of both, the Si-MCM-41 host and the impregnated composites were characterized by XRD, N₂ adsorption, DRUV–vis and Mössbauer spectroscopy. The magnetic behavior of each microstructure was characterized by the magnetization dependence on the magnetic field (up to 1.5T) and temperature (between 5 and 300K). The catalytic performance was tested for cyclohexene oxidation by hydrogen peroxide and further correlated with the observed magnetic properties. It was found that the reduction treatment largely affects the selectivity to reaction products, leading to catalysts exhibiting a selectivity of 80% towards the allylic oxidation products. This is attributed to a large free radical generation arising from the interaction between the hydrogen peroxide and the partially reduced iron species (mainly Fe⁰ and Fe₃O₄), exhibiting superparamagnetic and/or ferromagnetic character.

Keywords: Iron; Mesoporous molecular sieves; Magnetic properties; Cyclohexene oxidation; Reduction; Allylic oxidation products

Synthesis and application of a novel mesoporous zeolite L in the catalyst for the HDS of FCC gasoline by Quan Huo; Tao Dou; Zhen Zhao; Huifang Pan (pp. 101-108).

A novel mesoporous zeolite L was synthesized by the self-assembly of zeolite L nanocrystal clusters in the presence of template Triton X 100. The catalyst into which such material was introduced showed excellent hydrodesulfurization and preserved RON performances compared with the catalysts into which microporous zeolite L or mesoporous Al-MSU-2 was introduced and compared with the catalyst that used bare alumina as support for full-range FCC gasoline hydrodesulfurization.A novel mesoporous zeolite L (M-L) was synthesized by using the nanocrystal clusters of zeolite L as precursor and a nonionic surfactant Triton X 100 (TX 100, polyethylene glycol p-(1,1,3,3-tetramethylbutyl)-phenyl ether) as template. Several techniques including XRD, nitrogen adsorption, TEM,²⁷Al MAS NMR, NH₃-TPD, and Py-FTIR were used for the physicochemical characterization of samples. Nitrogen adsorption results indicated that the material possessed composite pore structures with micropores and mesopores. The surface area and the pore volume of M-L significantly increased compared with those of ordinary zeolite L. The results of NH₃-TPD and Py-FTIR demonstrated that M-L had appropriate acid amounts and strengths, large amounts of Lewis acid sites and high L/B (the ratio of Lewis acid amount to Brönsted acid amount) values. For evaluation of FCC gasoline hydrodesulfurization, the catalyst in which mesoporous zeolite L was introduced showed the excellent performances of deep desulfurization, aromatization, isomerization and preservation of RON (research octane number) value compared with the catalysts into which ordinary microporous zeolite L or mesoporous Al-MSU-2 was introduced and compared with the catalyst that used bare alumina as support. The excellent catalytic performances of the catalyst should be attributed to appropriate acidity distribution, to a large amount of Lewis acid sites and to the open pore structure of material M-L. As a result, the possibilities for deep desulfurization, selective hydrogenation, aromatization and isomerization of the catalyst containing mesoporous zeolite L are favorable for decreasing sulfur content and for maintaining the relatively high contents of olefins, aromatics and isoparaffins, all these factors play important roles in maintaining a high RON value.

Keywords: Mesoporous zeolite L; Microporous and mesoporous composite structures; Triton X 100; Hydrodesulfurization; FCC gasoline; Hydrotreating catalyst

Photocatalysis by Electron Transfer between Different-sized Anatases by Tsung-Ying Ke; Chi-Young Lee; Hsin-Tien Chiu (pp. 109-113).

In the solution state, photocatalysis of micro- and nano-sized anatases can be optimized at flat band and in a high pH solution, respectively. Furthermore, a remarkable photocatalyst that can be adopted over a wide range of pH values was produced by mixing commercial micro- and nano-sized anatases.In the solution state, photocatalysis of micro- and nano-sized anatases can be optimized at flat band and in a high pH solution, respectively. Furthermore, a remarkable photocatalyst that can be adopted over a wide range of pH values was produced by mixing commercial micro- and nano-sized anatases. Mixing causes the electron transfer between the identical phase but different-sized TiO₂ particles, subsequently separating the electrons and holes, as well as greatly facilitating photocatalysis. As is well known, the commercially available photocatalyst P25, a mixture of anatase and rutile, achieves a superior photocatalytic performance from pH 3 to 10, owing to the electron transfer between the various phases. This study elucidates these mixed photocatalysts, P25 and mixture of micro and nano-sized anatases.

Keywords: Photocatalysis; Electron transfer; pH; P25

Oxidative dehydrogenation of ethane with oxygen catalyzed by K–Y zeolite supported first-row transition metals by Xufeng Lin; Kenneth R. Poeppelmeier; Eric Weitz (pp. 114-120).

The catalytic activity and selectivity for the oxidative dehydrogenation of ethane (ODHE) on transition metal (M=Ni, Co, Cu and Fe) oxides supported on basic Y zeolite were examined. The selectivities for ethylene production were obtained under various conditions, for an ethane conversion that was extrapolated to zero. The mechanistic implication of these measurements for the ODHE reaction is discussed.Fe, Co, Ni, and Cu oxide loaded K–Y zeolites were synthesized using a two-step method, in which transition metals in the zeolite framework reacted with the anions in solution to form an insoluble salt which, when calcined, is expected to form an oxide that is anchored to the inner and/or outer zeolite surface(s). The catalytic properties of these zeolites, for the oxidative dehydrogenation of ethane (ODHE) to ethylene were then investigated. An ethylene selectivity of close to 80%, at an ethane conversion of >20% was achieved on a nickel oxide loaded K–Y catalyst. This is a higher ethylene selectivity, at higher ethane conversion, than was achieved using a previously reported Ni/KY catalyst. The effects of both reaction temperature and the O₂/C₂H₆ ratio on the catalytic performance were examined. The apparent energy of activation for the ODHE reaction on the nickel oxide loaded K–Y catalyst was 51.5±0.7kJ/mol. The C₂H₄ selectivity at zero conversion ( S₀) on nickel oxide loaded K–Y was estimated for various O₂/C₂H₆ ratios at a number of temperatures. The implications for the reaction mechanism of the S₀ values, with regard to the relative values of critical rate constants are discussed.

Keywords: Oxidative dehydrogenation; Ethane; First-row transition metals; Y zeolite

Preparation of Pd (0) and Pd (II) nanotubes and nanoparticles on modified bentonite and their catalytic activity in oxidation of ethyl benzene to acetophenone by M. Ghiaci; Z. Sadeghi; M.E. Sedaghat; H. Karimi-Maleh; J. Safaei-Ghomi; A. Gil (pp. 121-131).

Palladium nanotubes and nanoparticles on a modified bentonite were studied as catalysts for the oxidation of ethyl benzene to acetophenone. The catalysts remained stable under several reaction conditions and can be reused several times.The synthesis and application of palladium nanotubes and nanoparticles on modified bentonite was studied. In the first step, an organo-bentonite was prepared by the exchange of the exchangeable Na⁺ cations of a homoionic Na–bentonite by cetyl pyridinium cations (CP–bentonite), especially in the range of low coverage ratios where surfactant ions are adsorbed through cation exchange with the counter ions of bentonite. At this stage, there will be a disordered liquid-like monolayer arrangement of alkyl chain within the gallery. This modified bentonite was loaded with the first generation of amidoamine hyperbranch cascade, 3,3′-(dodecylazanediyl) bis(N-(2-(2-aminoethylamino)ethyl)propanamide) (DAEP), which has a long aliphatic tail (C₁₂) and a hydrophilic head. The solid/liquid interfacial layer of this architecturally designed bentonite (DAEP–bentonite) was utilized as a nanoreactor for the synthesis of nanoparticles of Pd²⁺ and Pd⁰. The structure, specific surface area, and porosity of bentonite are significantly altered by the incorporation of nanoparticles. These alterations were monitored by several techniques such as N₂ adsorption, X-ray diffraction (XRD), transmission electron microscopy (TEM) and electrochemical impedance spectroscopy (EIS). The size of the palladium nanoparticles prepared in this work was in the range of 5–15nm. Solvent free oxidation of ethyl benzene using tert-butyl hydroperoxide as an oxidant showed that the palladium nanocatalysts prepared in this work, were highly active and selective.

Keywords: Palladium; Modified bentonite; Ethylbenzene; Oxidation

Bimetallic Ru/Ni supported catalysts for the gas phase hydrogenation of acetonitrile by P. Braos-García; C. García-Sancho; A. Infantes-Molina; E. Rodríguez-Castellón; A. Jiménez-López (pp. 132-144).

A family of bimetallic Ni-Ru catalysts supported on a mesoporous SBA-15 as well as the corresponding Ni and Ru monometallic catalysts were tested in the hydrogenation of acetonitrile reaction. Ru-rich bimetallic catalysts exhibited conversion values higher than that of pure Ni one, as a consequence of enhanced specific activity of Ni⁰ atoms, attributable to a strong interaction between both metals.A family of bimetallic Ni-Ru catalysts supported on a mesoporous SBA-15 silica was prepared by conventional impregnation method, with constant metal molar loadings, but varying Ni/(Ni+Ru) atomic ratios. The corresponding Ni and Ru monometallic catalysts were also prepared for comparison. These catalysts were characterized by XRD, N₂ adsorption–desorption at −196°C, TEM, XPS, H₂-TPR, chemisorption of H₂ at r.t., H₂-TPD and NH₃-TPD techniques. Finally, they were also tested in the hydrogenation of acetonitrile reaction, in the gas phase and at atmospheric pressure. Acetonitrile conversion values depended on the Ni/(Ni+Ru) composition of the bimetallic catalysts. Ru-rich bimetallic catalysts exhibited acetonitrile conversion values higher than that of pure Ni one; thus, although selectivity patterns remained almost unchanged, primary amine yields were increased. These higher conversion values resulted as a consequence of enhanced specific activity of Ni⁰ atoms, attributable to a strong interaction between both metals, Ni and Ru, likely because NiRu alloy nanoparticles were formed.

Keywords: Gas phase acetonitrile hydrogenation; Supported nickel-ruthenium bimetallic catalysts; Mesoporous silica; SBA-15

Microwave-assisted regioselective alkylation of naphthalene compounds using alcohols and zeolite catalysts by Hiroshi Yamashita; Yumi Mitsukura; Hiroko Kobashi; Kazuaki Hiroki; Jun-ichi Sugiyama; Kiyotaka Onishi; Tetsuo Sakamoto (pp. 145-149).

Microwave-assisted regioselective alkylation of naphthalene compounds (2-isopropylnaphthalene, naphthalene) with alcohols (isopropyl alcohol, tert-butyl alcohol) smoothly proceeded in the presence of a H-mordenite catalyst (SiO₂/Al₂O₃ ratio=240) to give the corresponding 2,6-dialkylnaphthalenes with high selectivities. The conversions and the selectivities were generally higher than those obtained by conventional oil bath heating.Regioselective alkylation of naphthalene compounds with alcohols smoothly proceeded in the presence of zeolite catalysts under microwave irradiation. A H-mordenite (H-M) zeolite catalyst (SiO₂/Al₂O₃ ratio=240) showed the highest efficiency. In the microwave reactions, high reaction rates and high selectivities for 2,6-dialkylnaphthalenes were achieved. In the best case for the reaction of 2-isopropylnaphthalene with isopropyl alcohol, the conversion and the selectivity were 43.5% and 66.4%, respectively. In di- tert-butylation of naphthalene with tert-butyl alcohol, the conversion and the selectivity reached 86.5% and 70.4%, respectively. The conversions and the selectivities were generally higher than those obtained by conventional oil bath heating.

Keywords: Microwave; Naphthalene; Alkylation; Alcohol; Zeolite

Exotemplated ceria catalysts with gold for CO oxidation by S.A.C. Carabineiro; S.S.T. Bastos; J.J.M. Órfão; M.F.R. Pereira; J.J. Delgado; J.L. Figueiredo (pp. 150-160).

Cerium oxides were synthesized by an exotemplating procedure using activated carbon and carbon xerogel and loaded with gold. The catalytic performance of samples was tested in the oxidation of carbon monoxide. Xerogel prepared samples showed to be the most active. The gold particle size was 5–10nm for the most active sample, and 8–13nm for the least active.Cerium oxides were synthesized by an exotemplating procedure using both activated carbon and carbon xerogel as templates. The template effect and the preparation method were investigated. The surface area of the materials varied from 73 to 114m²g⁻¹, being similar to samples prepared by standard precipitation and calcination techniques (150 and 98m²g⁻¹, respectively), but much larger than a commercial ceria sample (20m²g⁻¹), used for comparison purposes. Samples prepared using xerogel as template have, approximately, twice as much porosity than those prepared with activated carbon, and the mesopores of the first are roughly 4 times larger than those of the latter. Cerianite CeO₂ was the only phase detected by XRD for all materials. Gold was loaded onto these materials by a double impregnation method. The catalytic performance of these ceria oxide materials alone and loaded with gold was tested in the oxidation of carbon monoxide. Xerogel prepared samples showed to be the most active in CO oxidation. Addition of Au increased the activity up to two orders of magnitude, at room temperature. With the unloaded samples, complete conversion was only achieved above 400°C, but when Au was loaded, full CO conversion occurred already at 75°C. Analysis of selected samples by HAADF and HRTEM showed that the gold particle size was 5–10nm for the most active sample, and 8–13nm for the least active. H₂-TPR experiments proved that addition of gold significantly helped to improve the reducibility of the surface oxygen on CeO₂. Both for ceria and Au/ceria materials, it was observed that the temperature at which the CO conversion started is related to the temperature of the first peak of the TPR spectrum, showing that the activity depends on the availability of surface oxygen. Experiments without oxygen in the feed, in the presence of ceria catalysts, suggest that the lattice oxygen can react with CO. It is shown that there is a significant correlation between the catalytic activity and the lattice oxygen donating ability. The TPR results suggest that gold is in its reduced state in the “fresh” Au/ceria samples.

Keywords: Ceria; Exotemplating; Gold; Carbon monoxide; Oxidation

Palladium-catalysed methylation of aryl halides in ionic liquids with stabilized AlMe₃ by Valeria Conte; Giulia Fiorani; Barbara Floris; Pierluca Galloni; Simon Woodward (pp. 161-168).

Methylation of aryl halides with DABAL-Me₃ in a VOC/IL system is proposed. Good yields and high chemoselectivity were observed. Satisfactory recycling of catalytic phase was attained using a charged phosphine ligand.A new protocol for the methylation of aryl halides using the AlMe₃ analogue DABAL-Me₃ in a VOC/IL biphasic system is described. Very good isolated yields and chemoselectivities (methylation vs homocoupling), were observed in alkylmethylimidazolium and DABCO-based ILs, in presence of a bulky substituted phosphine (XPhos) and the structurally related sulfonated phosphine (XPhosSO₃H). Recycling experiments of the IL-catalyst systems were satisfactory only in case of the butyldimethylimidazolium IL due to catalyst loss to the VOC phase.

Keywords: Methylation; Pd-catalysis; Ionic liquids; Cross-coupling reactions; Trialkylaluminum reagents; DABAL-Me; ₃

Study of CuO–CeO₂ catalysts supported on SiO₂ on the low-temperature oxidation of CO by Julián Astudillo; Gonzalo Águila; Francisco Díaz; Sichem Guerrero; Paulo Araya (pp. 169-176).

SiO₂-supported CuO–CeO₂ catalysts were studied in the low-temperature oxidation of CO. The optimum Cu/Ce ratio was found for a catalyst with 3% Cu and 7% Ce. The latter catalyst is able to maximize the available CuO–CeO₂ interface, which is the active phase in the oxidation of CO.A study was made on the effect of the Cu/Ce ratio and on the total load of both metals on the oxidation activity of CO with O₂ using SiO₂ as support. It was found that the optimum Cu/Ce ratio for a constant total load of 10% on silica (Aerosil 200) was 0.43 (w/w), which corresponded to a catalyst with 3% Cu and 7% Ce. For that ratio the highly dispersed CuO–CeO₂ interface was maximized. The catalyst's activity increased with increasing the total Cu–Ce load, but it reached a maximum above which the activity kept constant due to a similar concentration of sites at the CuO–CeO₂ interface. The higher surface area of the support led to a increase of CuO particles interacting with CeO₂ and to a decrease of bulk CuO species not interacting with CeO₂. The highly dispersed CuO–CeO₂ interface was not affected by a higher available surface area explaining the similar activity in supports with different surface area.

Keywords: CO oxidation; CuO; CeO; ₂; SiO; ₂; Supported catalysts

Stability of cerium-modified γ-alumina catalyst support in supercritical water by Adam J. Byrd; Ram B. Gupta (pp. 177-182).

Supercritical water is emerging as a promising medium to carry out a variety of catalytic reactions. However the support material can undergo transformation in the hydrothermal environment, as shown in the figure below. In this work the stability of a common support material γ-Al₂O₃ is examined at 500–700°C and 246bar.Supercritical water (above 374.1°C and 220.6bar) is emerging as a promising medium to carry out a variety of catalytic reactions, including reforming to produce hydrogen. However, when using a heterogeneous catalyst the support material can undergo transformations in the hydrothermal environment. In this work the stability of γ-Al₂O₃ modified with 1–10wt% Ce in supercritical water is examined, specifically in the temperature range of 500–700°C at 246bar. Transformations of the γ-phase were slowed but not prevented. Based on X-ray analysis, the transformation of γ-Al₂O₃ proceeded through the κ phase toward the stable α phase. Reduced cerium species were seen to be oxidized in the supercritical water environment, and low Ce-loading supports maintained the highest BET surface areas. The stabilization was greatest at 700°C, where Ce-modified aluminas retained significantly higher specific surface areas than unmodified alumina.

Keywords: Alumina; Hydrothermal; Supercritical water; Cerium; Stabilization

Al-MCM-41 as methanol dehydration catalyst by Sajo P. Naik; Vy Bui; Taegong Ryu; Jan D. Miller; Wlodzimierz Zmierczak (pp. 183-190).

Al-MCM-41, [SiO₂]/[Al₂O₃]=30, mesoporous catalysts were synthesized in the presence of tetrapropylammonium hydroxide (TPAOH) as a co-surfactant additive. The samples synthesized in the presence of TPAOH showed higher activity than those synthesized in its absence. Al-MCM-41 catalysts were also combined with methanol synthesis catalysts to form bifunctional catalysts for the synthesis of DME from CO₂/H₂.Al-MCM-41, [SiO₂]/[Al₂O₃]=30, mesoporous catalysts were synthesized using tetraethylorthosilicate (TEOS) as a source of silica and hexadecyltrimethylammonium bromide (CTAB) as a structure-directing agent (SDA) in the presence of tetrapropylammonium hydroxide (TPAOH) as a co-surfactant additive. The catalytic activities of the calcined samples were evaluated for the dehydration of methanol to dimethyl ether (DME) at 250–450°C and a gas hourly space velocity (GHSV) of 14,000–80,000mLg⁻¹_cath⁻¹. Al-MCM-41 samples synthesized in the presence of TPAOH showed higher activity than those synthesized in its absence. The improvement in catalytic activity correlates with the increase in acidity brought about by the enhanced condensation of aluminosilicate framework in the Al-MCM-41 structure. Al-MCM-41 catalysts were also combined with methanol synthesis catalysts to form bifunctional catalysts for the synthesis DME from CO₂/H₂ at temperature, 260°C; pressure, 735psi; GHSV, 2000mLg⁻¹_cath⁻¹ in a fixed-bed reactor.

Keywords: Al-MCM-41; Tetrapropylammonium hydroxide; Methanol dehydration catalyst; Dimethyl ether synthesis catalyst

Reduction of Fe₂O₃ with hydrogen by Jerzy Zieliński; Ilona Zglinicka; Leszek Znak; Zbigniew Kaszkur (pp. 191-196).

The reduction of Fe₂O₃ in hydrogen proceeds:•in two steps, Fe₂O₃→Fe₃O₄→Fe, in dry 5.8% H₂+Ar mixture, but•in three steps, Fe₂O₃→Fe₃O₄→“FeO”→Fe, in wet 5.8% H₂+Ar+H₂O mixture. ▪The reduction of Fe₂O₃ with hydrogen was studied. The thermodynamic analysis of the process implied that temperature-programmed reduction of the oxide should proceed in three steps, i.e. Fe₂O₃→Fe₃O₄→“FeO”→Fe, atXH2O/XH2 ratio over 0.35, but in two steps, i.e. Fe₂O₃→Fe₃O₄→Fe, below that value. The idea was verified by TPR and XRD studies. Generally, the examinations confirmed the suggestions. The reduction is three-step reaction at highXH2O/XH2 ratio, but two-step reaction at low that ratio. Additionally, it was revealed that at extremely lowXH2O/XH2 ratio the TP reduction is a one-step reaction, i.e. Fe₂O₃→Fe.

Keywords: Reduction of iron oxide; Temperature-programmed reduction (TPR); XRD; Fe; ₂; O; ₃; Hematite; Magnetite; Wustite; Iron

Merging traditional and high-throughput approaches results in efficient design, synthesis and screening of catalysts for an industrial process by Laurent A. Baumes; Pedro Serna; Avelino Corma (pp. 197-208).

The epoxidation of a model olefin with organic peroxides using titanium grafted on MCM-41 and ITQ-2 is investigated as a model reaction for the epoxidation of methyl-oleate. This contribution deals with the research methodology where HT and data mining are used with characterization, computational chemistry, and QSAR-QSPR analyses. We show how this results in greater benefits considering experiments saving and knowledge acquisition.In this manuscript, a strategy is presented that focuses on the maximization of the information retrieve by balancing the use of HT technology and other highly informative but time consuming sources. The methodology is applied to the epoxidation of a model olefin with organic peroxides, using titanium grafted on MCM-41 and ITQ-2 as catalysts for the reaction. The presented work represents a contribution in the research methodology for heterogeneous catalytic studies, where HT and data mining are used in close collaboration with characterization, computational chemistry, and quantitative structure activity and property relationship (QSAR/QSPR) analyses. It is shown how such an overlapping of the different disciplines results in greater benefits from the point of view of saving experiments and knowledge acquisition, so that main properties of the catalysts can be optimized in a rational way using an automated strategy.

Keywords: QSAR; QSPR; Descriptors; Catalysts; High-throughput; Data mining

Selective hydrogenation of crotonaldehyde in liquid-phase over Au/Mg₂AlO hydrotalcite catalysts by Hsing-Yu Chen; Ching-Tu Chang; Shu-Jen Chiang; Biing-Jye Liaw; Yin-Zu Chen (pp. 209-215).

Gold dispersed on the solid base of Mg₂AlO hydrotalcite could selectively hydrogenate crotonaldehyde (UAL) to crotyl alcohol (UOL). A high selectivity value of UOL, about 62%, was obtained near complete conversion and the UOL was not successively reduced to 1-butanol (SOL). The correlation between the gold states (Au³⁺/Au⁰) and the activity and selectivity was extensively examined.The liquid-phase selective hydrogenation of crotonaldehyde to crotyl alcohol over Au supported on a solid base of Mg₂AlO-hydrotalcite (Mg/Al=2) was investigated. The 2% Au/Mg₂AlO catalysts were prepared using a modified deposition precipitation method without adjusting the pH of the initial HAuCl₄ solution. The influence of the calcination temperatures of the Mg₂AlO support and of the 2% Au/Mg₂AlO catalyst, and the effects of the reaction medium (solvent), temperature, pressure and concentration were studied. The promoter, Fe, Mo or W, was co-deposited with Au on Mg₂AlO to maximize the yield of crotyl alcohol. 2% Au/Mg₂AlO was compared with Au supported on FeOOH, Fe₂O₃, CeO₂, TiO₂ and Al₂O₃. The correlation between the gold states (Au³⁺/Au⁰) and the activity and selectivity of crotyl alcohol was extensively examined.

Keywords: Gold catalysts; Hydrotalcite; Promoters; Selective hydrogenation; Crotonaldehyde

Characterization of cobalt Fischer–Tropsch catalysts by Hui Ming; Bruce G. Baker; Marek Jasieniak (pp. 216-225).

Rare earth (RE) promoted cobalt-silica gel catalysts for Fischer–Tropsch (F–T) synthesis were prepared by wet impregnation and were investigated systematically. The addition of small amounts of praseodymium to cobalt-silica gel catalysts enhances their activity and selectivity in the F–T synthesis greatly. The optimal atomic ratio of Pr/Co for 6% cobalt-silica gel catalysts was found to be between 0.26 and 0.35.Rare earth (RE) promoted cobalt-silica gel catalysts for Fischer–Tropsch (F–T) synthesis were investigated systematically by various analytical techniques. The addition of small amounts of praseodymium to cobalt-silica gel catalysts greatly enhances their activity and selectivity in the F–T synthesis. The optimal atomic ratio of Pr/Co for 6% cobalt-silica gel catalysts was found to be between 0.26 and 0.35. Spectroscopic and other experimental results show that impregnated praseodymium readily substitutes the surface silicon atoms to form negatively charged centres on the surface of the support. Due to the presence of praseodymium, the deposited cobalt species can partially react with the support. Consequently, significant amounts of surface cobalt silicates or hydrosilicates can be formed. Most of these species undergo reduction during activation and can be converted to a metallic cobalt phase that remains incorporated at the silica surface.

Keywords: Catalyst characterization; Cobalt-silica gel catalyst; Rare earth; Promoter; Wet impregnation

A facile method for synthesis of amine-functionalized mesoporous zirconia and its catalytic evaluation in Knoevenagel condensation by K.M. Parida; Sujata Mallick; P.C. Sahoo; S.K. Rana (pp. 226-232).

In the Knoevenagel condensation reactions, the catalyst activity is mainly due to the structural basicity of the amine group. The reaction is initiated when a benzaldehyde molecule reacts with a surface amine to form an amine compound. The addition of diethyl malonate and the subsequent molecular rearrangement produces the final reaction product and water molecules.Amine-functionalized mesoporous zirconia was prepared by a co-condensation method using silane (aminopropyltrimethoxysilane, APTES) and zirconium butoxide. The materials were characterized by X-ray diffraction, BET surface area analysis,¹³C magic angle spinning-nuclear magnetic resonance (NMR), Fourier-transfer infrared spectroscopy (FTIR), transmittance electron micrography (TEM), and CHN analysis. FTIR and NMR results revealed the successful grafting of organic amines onto the surface of zirconia. The catalytic activities were investigated for liquid phase Knoevenagel condensation of various aromatic aldehydes with diethyl malonate. The catalysts showed excellent yield of products at room temperature in solvent-free condition.

Keywords: Mesoporous zirconia; Amine-functionalized; Knoevenagel condensation

Efficient epoxidation of alkenes with sodium periodate catalyzed by reusable manganese(III) salophen supported on multi-wall carbon nanotubes by Shahram Tangestaninejad; Majid Moghadam; Valiollah Mirkhani; Iraj Mohammadpoor-Baltork; Mohammad Saleh Saeedi (pp. 233-241).

Biomimetic epoxidation of alkenes catalyzed by [Mn(salophen)Cl] supported on functionalized multi-wall carbon nanotubes is reported. The MWCNTs were modified by 1,4-diaminobenzene, 4-aminophenol and 4-aminothiophenol and [Mn(salophen)Cl] were attached to the supports via axial ligation. The prepared catalysts were used for efficient epoxidation of alkenes with NaIO₄ at room temperature. These new heterogeneous catalysts are high reusability in the oxidation reactions.In this paper, efficient epoxidation of alkenes catalyzed by manganese(III) salophen chloride [Mn(salophen)Cl], supported on functionalized multi-wall carbon nanotubes MWCNTs, is reported. The MWCNT was modified with 1,4-diaminobenzene, 4-aminophenol and 4-aminothiophenol and [Mn(salophen)Cl] was attached to the supports via axial ligation. The prepared catalysts were used for efficient epoxidation of alkenes with NaIO₄ at room temperature. These new heterogenized catalysts were characterized by elemental analysis, FT-IR spectroscopy, diffuse reflectance UV–vis spectrophotometery and scanning electron microscopy. These heterogeneous catalysts were highly reusable in the oxidation reactions and reused several times without significant loss of their catalytic activity.

Keywords: Manganese(III) salophen; Alkene epoxidation; Sodium periodate; Multi-wall carbon nanotubes; Heterogeneous catalysts

Origin of different deactivation of Pd/SnO₂ and Pd/GeO₂ catalysts in methanol dehydrogenation and reforming: A comparative study by Harald Lorenz; Qian Zhao; Stuart Turner; Oleg I. Lebedev; Gustaaf Van Tendeloo; Bernhard Klötzer; Christoph Rameshan; Kristian Pfaller; Jürgen Konzett; Simon Penner (pp. 242-252).

The special properties of SnO₂ and GeO₂ upon annealing and reduction are shown to crucially influence the metal/bimetallic–support interaction in oxide-supported Pd-based bimetallic particles, and, consequently, also the interpretation of catalytic activity and selectivity in methanol conversion.Pd particles supported on SnO₂ and GeO₂ have been structurally investigated by X-ray diffraction, (High-Resolution) transmission and scanning electron microscopy after different reductive treatments to monitor the eventual formation of bimetallic phases and catalytically tested in methanol dehydrogenation/reforming. For both oxides this included a thin film sample with well-defined Pd particles and a powder catalyst prepared by incipient wetness impregnation. The hexagonal and the tetragonal polymorph were studied for powder GeO₂. Pd₂Ge formation was observed on all GeO₂-supported catalysts, strongly depending on the specific sample used. Reduction of the thin film at 573K resulted in full transformation into the bimetallic state. The partial solubility of hexagonal GeO₂ in water and its thermal structural instability yielded Pd₂Ge formation at 473K, at the cost of a structurally inhomogeneous support and Ge metal formation at higher reduction temperatures. Pd on tetragonal GeO₂ entered a state of strong metal–support interaction after reduction at 573–673K, resulting in coalescing Pd₂Ge particles on a sintered and re-crystallized support, apparently partially covering the bimetallic particles and decreasing the catalytic activity. Pd₂Ge on amorphous thin film and hexagonal GeO₂ converted methanol primarily via dehydrogenation to CO and H₂.At 573K, formation of Pd₂Sn and also PdSn occurred on the Pd/SnO₂ thin film. Pd₃Sn₂ (and to some extent Pd₂Sn) were predominantly obtained on the respective powder catalyst. Strong deactivation with increasing reduction temperature was observed, likely not based on the classical strong metal–support interaction effect, but rather on a combination of missing active structural ensembles on Sn-enriched bimetallic phases and the formation of metallic β-Sn. Correlations to Pd and its bimetallics supported on ZnO, Ga₂O₃ and In₂O₃ were also discussed.

Keywords: Electron microscopy; Pd; ₃; Sn; ₂; Pd; ₂; Ge; Metal–support interaction; Methanol conversion; Selected area electron diffraction; Pd; ₂; Sn; PdSn

Fischer–Tropsch synthesis over LaFe1−_xCo_xO₃ perovskites from a simulated biosyngas feed by Néstor Escalona; Soledad Fuentealba; Gina Pecchi (pp. 253-260).

Fischer–Tropsch reaction using a mixture similar to that obtained from biomass transformation has been studied over LaFe1−_xCo_xO₃ perovskites. The CO conversion over LaFe1−_xCo_xO₃ perovskites is mainly determined by the dispersion of Co segregates species. A higher metal Co segregates particle decreases the production of hydrocarbon chain C₁₄₊ and promotes the synthesis of smaller hydrocarbon chain lengths (C₈–C₉).The Fischer–Tropsch synthesis reaction using a simulated gas mixture, comparable to that obtained from biomass transformation (biosyngas), was studied over LaFe1−_xCo_xO₃ perovskites. The perovskites were prepared using the amorphous citrate precursor method and the FTS reaction was carried out in a stainless steel fixed bed reactor at 300°C and 1MPa. Nitrogen adsorption was at −196°C. Thermal-programmed reduction (TPR), X-ray diffraction (XRD), Fourier-transform IR spectroscopy (FTIR), oxygen-temperature-programmed desorption (O₂-TPD) and scanning electron microscopy (SEM) were used as characterization methods. The perovskites were found to display two crystal systems determined by XRD patterns, orthorhombic for x_Co<0.5 and rhombohedral for x_Co≥0.5. The LaFe1−_xCo_xO₃ perovskites, with a substitution degree x_Co=0.1, 0.2 and 1.0, displayed significant intrinsic CO conversion. This activity was probably due to the formation of Co–metal segregates on the surface, as suggested by XRD patterns. The highest CO intrinsic conversion was obtained for perovskites with a substitution degree of x_Co=0.2. The LaFe1−_xCo_xO₃ perovskites presented a wide distribution of liquid hydrocarbons (C₆–C₁₈₊) and high CH₄ formation. The liquid product distribution was related to the average size of iron particles. The increase of cobalt particle size favours the formation of hydrocarbons centred in C_8–9 chain length.

Keywords: Lanthanum; Iron; Cobalt; Fischer–Tropsch; Perovskites; Biosyngas

Influence of Mn doping on the performance of CuO-CeO₂ catalysts for selective oxidation of CO in hydrogen-rich streams by Jing Li; Pengfei Zhu; Shufeng Zuo; Qinqin Huang; Renxian Zhou (pp. 261-266).

CuO-CeO₂ catalysts with Mn doping were studied for the selective oxidation of CO in hydrogen-rich streams. CO conversions of up to 99.0% were attained from 110 to 140°C, with O₂ selectivity above 50%. The formation of a more stable solid solution with a larger surface area and smaller particle size after doping Mn contributed to the excellent performance.CuO-CeO₂ catalysts with different amounts of Mn doping were prepared by a hydrothermal method and were investigated by means of X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET), temperature-programmed reduction (H₂-TPR), X-ray photoelectron spectroscopy (XPS) and UV-Raman. The results show that MnO_x-CuO-CeO₂ catalyst with Mn:Cu=1:5 exhibits the best catalytic activity and the broadest operating temperature “window” for the high conversion (CO conversion>99.0%, 110–140°C) in the selective oxidation of CO in hydrogen-rich streams. Doping an appropriate amount of Mn in CuO-CeO₂ catalyst is beneficial to the formation of a more stable solid solution with a larger surface area and smaller particle size, and the redox properties of the catalysts are also enhanced, which improves the selective oxidation performance of CO in hydrogen-rich streams.

Keywords: Mn doping; CuO-CeO; ₂; catalysts; Selective oxidation of CO; Hydrogen-rich streams; Oxygen vacancies

Biomimetic polymerization of aniline using hematin supported on halloysite nanotubes by Elisa Tierrablanca; Jorge Romero-García; Paulina Roman; Rodolfo Cruz-Silva (pp. 267-273).

This work shows the use of a naturally occurring nanostructured silicate as support for hematin, a biomimetic catalyst, and its use for the aniline polymerization. This is an alternative method to chemical functionalization of hematin that also increases its catalytic activity in acidic environments, and opens the possibility for the large-scale and environmentally friendly polyaniline–silica nanocomposites.Halloysite is a very interesting naturally occurring aluminosilicate, which has received great attention due to its nanotube shape. We used this nanostructured material as support for hematin, a biomimetic catalyst, which was successfully employed for the aniline polymerization. The adsorption of hematin (Heme) on the halloysite nanotubes (HNTs) was confirmed by UV–vis spectroscopy, zeta potential measurements, thermal analysis and X-ray diffraction. The resulting HNTs/Heme/PANi nanocomposites were characterized by transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy (FTIR). UV–vis and FTIR confirmed the formation of the conjugated form of polyaniline (PANi). Electrical conductivity of the HNTs/Heme/PANi nanocomposites was in the order of 8.8×10⁻¹S/cm. This work shows the use of a naturally occurring nanostructured material as support for biomimetic catalyst immobilization, opening possibilities for a large-scale and environmentally friendly polyaniline synthesis.

Keywords: Biomimetic catalyst; Hematin; Polyaniline synthesis; Halloysite

Heterogenization of functionalized Cu(II) and VO(IV) Schiff base complexes by direct immobilization onto amino-modified SBA-15: Styrene oxidation catalysts with enhanced reactivity by Ying Yang; Ying Zhang; Shijie Hao; Jingqi Guan; Hong Ding; Fanpeng Shang; Pengpeng Qiu; Qiubin Kan (pp. 274-281).

Two copper(II) and oxovanadium(IV) Salen complexes anchored on mesoporous SBA-15 are active for the oxidation of styrene with air or H₂O₂ as oxidant. The supported oxovanadium(IV) complex exhibits good product selectivity and high stability against leaching of active species. The superior properties of the heterogeneous catalyst result from the homogeneity of active species and its covalent bonding to the interior channels.Two functionalized copper(II) and oxovanadium(IV) Schiff base complexes of type [M(N₂O₂), M=Cu, VO] bearing chloromethyl groups were respectively synthesized, directly anchored onto amino-modified SBA-15 materials and examined as catalysts for styrene oxidation. The purity of each ligand was confirmed by¹H NMR, FT-IR and elemental analysis. XRD, N₂ adsorption/desorption and TEM results indicated that the mesoporous structure of SBA-15 remained intact throughout the grafting procedure. FT-IR, UV–vis spectroscopy plus TG–DTA data demonstrated the incorporation of copper(II) and oxovanadium(IV) complexes on amino-modified SBA-15. ICP-AES, SEM-EDX combined with XPS data further showed the different anchorage status of copper(II) and oxovanadium(IV) species on amino-modified SBA-15. The copper(II) Schiff base complex was anchored through the coordination of copper atom with the nitrogen atom of the amino group modified on the SBA-15 external surface. The oxovanadium(IV) Schiff base complex, however, was covalently anchored on SBA-15 via the condensation reaction of the chloromethyl group of the Schiff base with the amino group from the modified SBA-15 matrix. The catalytic properties of supported copper(II) and oxovanadium(IV) complexes in the oxidation of styrene with air or H₂O₂ as oxidant were investigated and compared with the properties of their homogeneous analogues. It was found that both heterogeneous copper(II) and oxovanadium(IV) catalysts were more active than their homogeneous analogues and that the product selectivity varied in cases of different oxidants. The supported oxovanadium(IV) complex showed high yield of styrene oxide (56.0%) and good recoverability when using air as oxidant.

Keywords: Mesoporous materials; Metal Schiff base complexes; Styrene oxidation; Copper; Oxovanadium

Effect of Rh promoter on MWCNT-supported alkali-modified MoS₂ catalysts for higher alcohols synthesis from CO hydrogenation by Venkateswara Rao Surisetty; Ajay Kumar Dalai; Janusz Kozinski (pp. 282-288).

The promotional effects of Rh (0 to 2wt%) on Mo-K/MWCNT catalysts for higher alcohol synthesis from synthesis gas (molar ratio of H₂ to Co is equal to 1) were examined. The maximum total alcohol yield of 0.211g/(gofcat./h), and ethanol selectivity of 16% were observed on the catalyst with 1.5wt% Rh at 320°C and 8.3MPa.The promotional effects of Rh (0 to 2wt%) on Mo-K/MWCNT catalysts for higher alcohol synthesis from synthesis gas (molar ratio of H₂ to Co is equal to 1) were examined. Diffraction peaks representing the characteristic K-Mo-S phase were observed in the X-ray diffraction (XRD) patterns of the sulfided form of the Rh-promoted Mo-K/MWCNT catalysts. When 1wt% Rh was introduced on the multi-walled carbon nanotube (MWCNT)-supported 15wt% Mo and 9wt% K catalysts, the reduction temperature of Mo(VI) to Mo(IV) was significantly decreased to 394°C. Metal dispersions were increased from 30% to 42%, with an increase in Rh content from 0 to 2wt%. The existence of promoted and un-promoted MoS₂ sites was confirmed by a diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) study of adsorbed CO over sulfided catalysts. The maximum total alcohol yield of 0.211g/(gofcat./h), ethanol selectivity of 16%, and higher alcohols selectivity of 25% were observed on the catalyst with 1.5wt% Rh at 320°C and 8.3MPa. The best conditions for producing higher alcohols from synthesis gas (mole ratio of H₂ and CO is equal to 1) using gas hourly space velocity (GHSV) of 3.6m³(STP)/h/(kgofcatalyst) are determined as 330°C and 9.65MPa (1400psig).

Keywords: Abbreviations; DRIFTS; diffuse reflectance infrared Fourier transform spectroscopy; DTA; differential thermal analyzer; FID; flame ionization detection; GHSV; gas hourly space velocity; HAS; higher alcohol synthesis; ICP-MS; inductively coupled plasma-mass spectroscopy; MWCNT(s); multi-walled carbon nanotubes; STY; space time yield; TEM; transmission electron microscopy; TPR; temperature programmed reduction; XRD; X-ray diffractionHigher alcohols synthesis; Alkali-promoted MoS; ₂; catalysts; Multi-walled carbon nanotubes; Rh promotion

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Applied Catalysis A, General (v.381, #1-2)