Reduction of NO by CO on Cu/ZrO(2)/Al(2)O(3) catalysts: Characterization and catalytic activities

ZrO(2), gamma-Al(2)O(3) and ZrO(2)/gamma-Al(2)O(3)-supported copper catalysts have been prepared, each with three different copper loads (1, 2 and 5 wt%), by the impregnation method. The catalysts were characterized by nitrogen adsorption (BET), X-ray diffraction (XRD), temperature programmed reduction (TPR) with H(2), Raman spectroscopy and electronic paramagnetic resonance (EPR). The reduction of NO by CO was studied in a fixed-bed reactor packed with these catalysts and fed with a mixture of 1% CO and 1% NO in helium. The catalyst with 5 wt% copper supported on the ZrO(2)/gamma-Al(2)O(3) matrix achieved 80% reduction of NO. Approximately the same rate of conversion was obtained on the catalyst with 2 wt% copper on ZrO(2). Characterization of these catalysts indicated that the active copper species for the reduction of NO are those in direct contact with the oxygen vacancies found in ZrO(2). (C) 2009 Published by Elsevier Ltd.

A single-step procedure for the preparation of palladium nanoparticles and a phosphine-functionalized support as catalyst for Suzuki cross-coupling reactions

We here report the preparation of supported palladium nanoparticles (NPs) stabilized by pendant phosphine groups by reacting a palladium complex containing the ligand 2-(diphenylphosphino)benzaldehyde with an amino-functionalized silica surface The Pd nanocatalyst is active for Suzuki cross-coupling reaction avoiding any addition of other sources of phosphine ligands The Pd intermediates and Pd NPs were characterized by solid-state nuclear magnetic resonance and transmission electron microscopy techniques The synthetic method was also applied to prepare magnetically recoverable Pd NPs leading to a catalyst that could be reused for up to 10 recycles In summary we gathered the advantages of heterogeneous catalysis magnetic separation and enhanced catalytic activity of palladium promoted by phosphine ligands to synthesize a new catalyst for Suzuki cross-coupling reactions The Pd NP catalyst prepared on the phosphine-functionalized support was more active and selective than a similar Pd NP catalyst prepared on an amino-functionalized support (C) 2010 Elsevier Inc All rights reserved

Effect of adding CaO to ZrO(2) support on nickel catalyst activity in dry reforming of methane

Nickel catalysts with a load of 5 wt% Ni, supported on pure ZrO(2) and ZrO(2) stabilized with 4, 8 and 14 mol% CaO, were prepared by the polymerization method. The samples were characterized by X-ray diffraction (XRD), temperature-programmed reduction with hydrogen (TPR-H(2)), specific surface area (BET) and impedance spectroscopy (IS) and tested in the carbon dioxide reforming of methane. The XRD patterns showed the presence of the oxide precursor (NiO) and the tetragonal phase of CaO-ZrO(2) solid solutions. According to the TPR-H(2) analysis, the reduction of various NiO species was influenced by the support composition. The electrical properties of the support have a proportional effect on the catalytic activities. Catalytic tests were done at 800 degrees C for 6 h and the composition of the gaseous products and the catalytic conversion depended on the CaO-ZrO(2) solid solution composition and its influence on supported NiO species. A direct relation was found between the variation in the electrical conductivity of the support, the nickel species supported on it and the performance in the catalytic tests. (C) 2009 Elsevier B.V. All rights reserved.

Effect of the Y(2)O(3)-ZrO(2) support composition on nickel catalyst evaluated in dry reforming of methane

Nickel catalysts with a load of 5 wt.% Ni, supported on pure ZrO(2) and ZrO(2) stabilized with 4 mol%, 8 mol% and 12 mol% of Y(2)O(3), were prepared by the polymerization method. The samples were characterized by X-ray diffraction (XRD), temperature-programmed reduction with hydrogen (TPR-H(2)), specific surface area (BET) and electronic paramagnetic resonance (EPR) and tested as catalysts for carbon dioxide reforming of methane. The XRD patterns showed the presence of the oxide precursor (NiO) and the tetragonal phase of a Y(2)O(3)-ZrO(2) solid solution. According to the TPR-H(2) analysis, the reduction of various NiO species was influenced by the composition of the support. Catalytic tests were conducted at 800 degrees C for 6 h, and the composition of the gaseous products and the catalytic conversion rate depended on the composition of the Y(2)O(3)-ZrO(2) solid solution and its influence on the supported NiO species. A direct relation was observed between the variation in the support, the nickel species supported on it and the performance in the catalytic tests. (C) 2008 Elsevier B.V. All rights reserved.

Catalytic hydrodechlorination of chlorobenzene over supported palladium catalyst in buffered medium

The catalytic hydrodechlorination (HDC) reaction, which is an attractive abatement process for chlorinated organic wastes, was studied over a magnetically recoverable supported Pd(0) catalyst. We investigated the most favorable reaction conditions under which to obtain the highest substrate conversion rates while preserving the catalyst properties and morphology. Sodium hydroxide, triethylamine and buffered solutions were used as proton scavengers in the HDC of chlorobenzene under mild conditions. It was observed that sodium hydroxide caused corrosion of the silica support, triethylamine in 2-propanol preserved the morphology of the catalyst which could be recycled for up to five successive H DC reactions, and aqueous buffer solutions preserved the catalyst morphology and the catalytic activity for up to four successive HDC reactions. The use of buffer solutions to neutralize the HCl formed during the HDC reaction is an interesting, less aggressive, alternative approach to HDC reactions. (C) 2010 Elsevier B.V. All rights reserved.

Nickel catalysts supported on ZrO2, Y2O3-stabilized ZrO2 and CaO-stabilized ZrO2 for the steam reforming of ethanol: Effect of the support and nickel load

Catalysts with various nickel loads were prepared on supports of ZrO2, ZrO2-Y2O3 and ZrO2-CaO, characterized by XRD and TPR and tested for activity in ethanol steam reforming. XRD of the supports identified the monoclinic crystalline phase in the ZrO2 and cubic phases in the ZrO2-Y2O3 and ZrO2-CaO supports. In the catalysts, the nickel impregnated on the supports was identified as the NiO phase. In the TPR analysis, peaks were observed showing the NiO phase having different interactions with the supports. In the catalytic tests, practically all the catalysts achieved 100% ethanol conversion, H-2 yield was near 70% and the gaseous concentrations of the other co-products varied in accordance with the equilibrium among them, affected principally by the supports. It was observed that when the ZrO2 was modified with Y2O3 and CaO, there were big changes in the CO and CO2 concentrations, which were attributed to the rise in the number of oxygen vacancies, permitting high-oxygen mobility and affecting the gaseous equilibrium. The liquid products analysis showed a low selectivity to liquid co-products during the reforming reactions. (c) 2007 Published by Elsevier B.V.

Co catalysts supported on SiO(2) and gamma-Al(2)O(3) applied to ethanol steam reforming: Effect of the solvent used in the catalyst preparation method

Cobalt catalysts were prepared on supports of SiO(2) and gamma-Al(2)O(3) by the impregnation method, using a solution of Co precursor in methanol. The samples were characterized by XRD, TPR, and Raman spectroscopy and tested in ethanol steam reforming. According to the XRD results, impregnation with the methanolic solution led to smaller metal crystallites than with aqueous solution, on the SiO(2) support. On gamma-Al(2)O(3), all the samples exhibited small crystallites, with either solvent, due to a higher Co-support interaction that inhibits the reduction of Co species. The TPR results were consistent with XRD results and the samples supported on gamma-Al(2)O(3) showed a lower degree of reduction. In the steam reforming of ethanol, catalysts supported on SiO(2) and prepared with the methanolic solution showed the best H(2), CO(2) and CO selectivity. Those supported on gamma-Al(2)O(3) showed lower H(2) selectivity. (C) 2011 Elsevier Ltd. All rights reserved.

Hydrogen purification for fuel cell using CuO/CeO(2)-Al(2)O(3) catalyst

CuO/CeO(2), CuO/Al(2)O(3) and CuO/CeO(2)-Al(2)O(3) catalysts, with CuO loading varying from 1 to 5 wt.%, were prepared by the citrate method and applied to the preferential oxidation of carbon monoxide in a reaction medium containing large amounts of hydrogen (PROX-CO). The compounds were characterized ex situ by X-ray diffraction, specific surface area measurements, temperature-programmed reduction and temperature-programmed reduction of oxidized surfaces; XANES-PROX in situ experiments were also carried out to study the copper oxidation state under PROX-CO conditions. These analyses showed that in the reaction medium the Cu(0) is present as dispersed particles. On the ceria, these metallic particles are smaller and more finely dispersed, resulting in a stronger metal-support interaction than in CuO/Al(2)O(3) or CuO/CeO(2)-Al(2)O(3) catalysts, providing higher PROX-CO activity and better selectivity in the conversion of CO to CO(2) despite the greater BET area presented by samples supported on alumina. It is also shown that the lower CuO content, the higher metal dispersion and consequently the catalytic activity. The redox properties of the ceria support also contributed to catalytic performance. (C) 2010 Elsevier B.V. All rights reserved.

Effects of adding La and Ce to hydrotalcite-type Ni/Mg/Al catalyst precursors on ethanol steam reforming reactions

Catalyst precursors composed of Ni/Mg/Al oxides with added La and Ce were tested in ethanol steam reforming (ESR) reactions. La and Ce were added by anion-exchange. The oxides were characterized by X-ray photoelectron spectroscopy (XPS) and X-ray absorption near-edge structure (XANES) analysis. The catalyst precursors consist of a mixture of oxides, with the nickel in the form of NiO strongly interacting with the support Mg/Al. The XPS analysis showed a lanthanum-support interaction, but no interaction of Ce species with the support. The reaction data obtained with the active catalysts showed that the addition of Ce and La resulted in better H(2) production at 550 degrees C. The CeNi catalyst provided the higher ethanol conversion, with lower acetaldehyde production, possibly clue to a favoring of water adsorption on the weakly interacting clusters of CeO(2) on the surface. (C) 2010 Elsevier B.V. All rights reserved.

Methane conversion reactions on Ni catalysts promoted with Rh: Influence of support

Ni catalysts supported on gamma-Al(2)O(3) and Mg(Al)O were prepared with and without Rh as a promoter and tested in the reforming of methane in the presence of excess methane, simulating a model biogas. The effects of adding synthetic air on the methane conversion and the formation of carbon were assessed. The catalysts were characterized by X-ray spectroscopy (EDS), surface area (BET), X-ray diffraction (XRD), Temperature-programmed reduction (TPR), X-ray absorption near-edge structure (XANES) and XPD. The results showed that in catalysts without Rh, the Ni interacts strongly with the supports, showing high reduction temperatures in TPR tests. The addition of Rh increased the amount of reducible Ni and facilitated the reduction of the species interacting strongly with the support. In the catalytic tests, the samples promoted with Rh suffered higher carbon deposition. The in situ XPD suggested that on the support gamma-Al(2)O(3), the presence of Rh probably led to a segregation of Ni species with time on stream, leading to carbon deposition. On the support MgAlO, the presence of Rh improved the dispersion of Ni, by reducing the Ni(0) crystallite size, suggesting that in this case the carbon deposition was due to a favoring of CH(4) decomposition by Rh. (C) 2011 Elsevier B.V. All rights reserved.