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The reactive adsorption of sulfur-contaminated compounds over transition metal (TrM) polycation-exchanged zeolites is a very efficient method for the desulfurization of hydrocarbon processing streams. The process consists of the physical adsorption of thiols, sulfides, and disulfides and the catalytic oxidation of the adsorbed substances. The reaction does not require the participation of free oxygen; diffuse-reflectance infrared Fourier transform spectroscopy (DRIFTS) and X-ray absorption spectroscopy (XAS) studies confirmed that the thiol oxidation proceeds through the direct involvement of TrM polycation superoxides. All of the studied zeolite X, zeolite Y, and mordenite materials containing Zn, Mn, Cu, and Cd polycations show remarkable activity for the oxidation of sulfur compounds; this results in a significant increase of the total pick-up from gas and liquid hydrocarbons. The thermal regeneration of the adsorbent-catalysts under oxidizing conditions leads to the complete restoration of their original activities and capacities for the removal of sulfur compounds. Suitable operating conditions for the regeneration process are disclosed. The study also demonstrates favorable properties of the suggested adsorbent-catalysts for use in commercially important applications such as the desulfurization of natural gas and liquid hydrocarbons. [ABSTRACT FROM AUTHOR]

The oxidation of CO was studied on a series of MLaO3 perovskites (M=Co, Fe, Ni) supported on mesoporous zirconia that are synthesized by using a glycine-mediated method and characterized by using X-ray photoelectron spectroscopy, X-ray absorption spectroscopy, and diffuse reflectance infrared Fourier transform spectroscopy. The activity of the catalysts in the CO oxidation reaction follows the order Co>Ni>Fe. [ABSTRACT FROM AUTHOR]

Abstract: Novel catalytic nano-sized materials based on LaCoOx perovskite nanoparticles incapsulated in the mesoporous matrix of zirconia were prepared, characterized by physicochemical methods and tested in complete methanol oxidation. LaCoOx nanoparticles were prepared inside the mesopores of ZrO2 by decomposition of bimetallic La–Co glycine precursor complexes. The catalysts have been studied by diffuse-reflectance FTIR-spectroscopy using such probe molecules as CO, CD3CN and CDCl3 to test low-coordinated metal ions. At low temperatures of decomposition of complexes (up to 400°C), low-coordinated Co3+ ions predominate in the LaCoOx nanoparticles, whereas basically Co2+ ions are found upon increasing the decomposition temperature to 600°C. The novel nano-sized perovskite catalysts exhibit a very high catalytic activity in the abatement of volatile organic compounds present in air, like methanol and light hydrocarbons. [Copyright &y& Elsevier]

Abstract: Pd/H-Beta catalysts with different silica-to-alumina ratio prepared by an impregnation method have been studied by XANES/EXAFS, IR, XRD and TEM. It was shown that palladium in calcined Pd/H-Beta samples exists as palladium oxide that can be easily reduced to Pd metal. The catalysts were tested in selective oxidation of piperonyl alcohol to piperonylaldehyde at 80°C. The Pd/H-Beta zeolite catalysts with the lowest silica-to-alumina ratio possess the highest catalytic activity in benzylic alcohol oxidation reaction. [Copyright &y& Elsevier]

Au/Al2O3 and Ni/Al2O3 prepared by deposition-precipitation and impregnation methods, respectively, and Au–Ni/Al2O3 prepared by impregnation of the Au/Al2O3 system with nickel have been studied by physicochemical methods. The catalysts were tested in allylbenzene isomerization at 443 K. The isomerization on Au/Al2O3 proceeds with a rather low rate, while monometallic Ni/Al2O3 is inactive. Unlike monometallic catalysts, Au–Ni/Al2O3 demonstrates a strong synergetic effect: the isomerization rate on the bimetallic sample exceeds the sum of the rates over the individual metals by an order of magnitude. The catalysts structure was estimated by XPS, DRIFT, and XAS techniques. It was revealed that nickel in Au–Ni/Al2O3 and Ni/Al2O3 exist as Ni2+ cations with the coordination state close to that in the precursor, gold in Au/Al2O3 exist as Au0 nanoclusters, whereas the Au0 nanoclusters co-exist with Au3+ cations in the bimetallic Au–Ni/Al2O3 sample. Reasons of the synergetic catalytic effect for Au–Ni/Al2O3 are discussed in terms of the formation of new positively charged Au catalytic centers. [ABSTRACT FROM AUTHOR]

Previous studies have shown that a variety of iron-oxo species, including nanoclusters and dimers, can be formed within the pore structure of ZSM-5 and other porous materials. We report that these species can readily be sulfided by exposure to hydrogen sulfide at 623 K when formed in ZSM-5, mordenite, and MCM-41. The iron-sulfur entities produced have been characterized by XPS and EXAFS spectroscopy. Iron is in the oxidation state +2 and the nearest neighbor iron-sulfur interatomic distance is ∼2.25 Å, which is close to that in iron(II) sulfide. Sulfidation appears to be at least 90% complete. In ZSM-5 the same iron-sulfur species, which contains isolated iron atoms or very small clusters, is formed irrespective of whether the iron was introduced by aqueous exchange or chemical vapor deposition. The sulfided ZSM-5 material is found to be weakly active for the hydration of acrylonitrile to acrylamide in tetrahydrofuran solution at 338 K, with the best materials achieving about 0.5 turnovers per iron species per day. [ABSTRACT FROM AUTHOR]

A series of the Au–Cu/SiO 2 catalysts including low-loaded samples with an overall metal content less than 0.5 wt% was synthesized by a redox method. The catalysts were tested in the selective oxidation of ethanol to acetaldehyde. The highest catalytic activity was observed for the catalysts having the lowest metal content due to the presence of nanosized Au particles and the synergetic effect of Au–Cu 2+ interaction. Unusual reduction behavior was found for the catalysts with the 0.2 wt% content of Cu. XRD, TPR, EXAFS, and STEM techniques were applied for the catalysts characterization. [ABSTRACT FROM AUTHOR]

Abstract: In this paper we report the synthesis of robust and efficient nanocatalysts based on Pt-containing nanoparticles (NPs) formed in the pores of hypercrosslinked polystyrene (HPS) and their catalytic performance in the phenol CWAO under mild conditions. The Pt species were incorporated in HPS using wet impregnation of platinic acid in tetrahydrofuran followed by NaHCO3 treatment. The catalysts containing from 0.11 to 4.85wt.% of Pt were studied by X-ray fluorescence analysis, transmission electron microscopy, X-ray absorption spectroscopy, X-ray photoelectron spectroscopy, and liquid nitrogen physisorption methods. The NP sizes were found to be independent of the amount of platinic acid used for impregnation, but rather controlled by the pores of HPS. Three types of Pt species: Pt(0), Pt(II), and Pt(IV), constituted the NP composition. The effects of the phenol and catalyst initial concentrations and temperature were investigated in the phenol CWAO. Removal of 97% of the phenol with 94.2% selectivity to CO2 and H2O were observed for the most active catalyst containing 0.95wt.% Pt. These parameters are significantly higher than those for the conventional Al2O3–Pt catalyst with the similar amount of the active metal or for Pt(5%)/activated carbon. [Copyright &y& Elsevier]