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Costa V.V.,Federal University of Minas Gerais | Estrada M.,Research Center Cientifico Educacion Superior Of Ensenada | Demidova Y.,RAS Boreskov Institute of Catalysis | Prosvirin I.,RAS Boreskov Institute of Catalysis | And 5 more authors.
Journal of Catalysis | Year: 2012

Gold nanoparticles supported on magnesium oxide were shown to be efficient heterogeneous catalysts for the liquid-phase oxidation of a wide range of alcohols using molecular oxygen as a sole oxidant in the absence of co-catalysts or additives. The Au/MgO material was prepared through the deposition- precipitation method and characterized by XRD, XPS, XAS, HRTEM, UV-Vis spectroscopy, and N 2 adsorption techniques. The formation of gold nanoparticles on the MgO surface under temperature programmed reduction was monitored by in situ UV-Vis-Mass spectroscopy. Various carbonylic monoterpenoids important for fragrance and pharmaceutical industries were obtained in good to excellent yields starting from biomass-based monoterpenic alcohols, such as isoborneol, perillyl alcohol, and carveol. The Au/MgO catalyst also performs a selective one-pot oxidative esterification of benzyl alcohol in alkali-free methanol solutions in the absence of any additive to give methyl benzoate in a virtually quantitative yield. © 2012 Elsevier Ltd. All rights reserved.

Simakova O.A.,Abo Akademi University | Smolentseva E.,National Autonomous University of Mexico | Estrada M.,Research Center Cientifico Educacion Superior Of Ensenada | Murzina E.V.,Abo Akademi University | And 4 more authors.
Journal of Catalysis | Year: 2012

Aerobic selective oxidation of the naturally occurring lignan hydroxymatairesinol (HMR) to another lignan oxomatairesinol (oxoMAT) was carried out at 70 °C and atmospheric pressure over different gold and gold-palladium catalysts. Several groups of gold catalysts were prepared: Au ion-exchanged on Y-zeolites promoted by Cu, Ni, Fe; Au and Au-Pd supported via deposition-precipitation with urea - DPU on metal oxides (magnesia, alumina, ceria, zirconia, and lanthanum oxide); and Au on alumina, and alumina-ceria-zirconia mixed oxides prepared by the sol-gel method. The catalysts were characterized by ICP-AES, TEM, XPS and UV-Vis techniques. Acidity of supports was studied by an FTIR method using pyridine as a probe molecule. No catalytic activity was detected in case of gold catalysts based on zeolites. Au and Au-Pd catalysts supported on metal oxides showed different activity and selectivity in the HMR transformation depending on the support acidity/basicity and the active phase. The highest activity was reached over Au supported on alumina with big transport pores displaying 100% selectivity to oxoMAT. © 2011 Elsevier Ltd. All rights reserved.

Smolentseva E.,National Autonomous University of Mexico | Kusema B.T.,Abo Akademi University | Beloshapkin S.,University of Limerick | Estrada M.,Research Center Cientifico Educacion Superior Of Ensenada | And 5 more authors.
Applied Catalysis A: General | Year: 2011

Selective oxidation of arabinose to arabinonic acid was carried out isothermally in a shaker reactor at moderate conditions of 60°C and pH 8 on Pd-Au catalysts supported on nanosized alumina and ceria. The gold (4 wt.%) was supported by deposition-precipitation (DP) using HAuCl4 and urea with subsequent chemisorption of palladium (1 wt.%) using PdCl2. Before catalytic tests, samples were treated in hydrogen or oxygen at 300°C, or by aqueous solution of formaldehyde at room temperature. Synthesized bimetallic Pd-Au catalysts are characterized with higher activity in the selective aqueous phase oxidation of arabinose to arabinonic acid by molecular oxygen in comparison with monometallic ones. Activity and selectivity of catalysts depend on the sample treatment and the nature of the support used. Pd-Au/CeO 2 catalyst reduced by formaldehyde manifests the highest activity and selectivity. The synthesized bimetallic catalysts have been characterized by TEM, XPS and UV-vis techniques under different stages of sample activation. Mutual interactions of supported gold and palladium species depending on the support nature and sample treatment were observed. A more pronounced interaction between gold and palladium species was observed for Pd-Au/Al2O 3 catalyst, while interactions of Au and Pd with reducible ceria coexist with the mutual interaction between these metals. Gold metallic species seem to be responsible for activation of arabinose while an easy redox transformation of Pd species can provoke oxygen activation. Thus, gold species or Au-Pd alloy covered with thin PdO film manifest a synergetic effect in the selective arabinose oxidation by molecular oxygen. © 2010 Elsevier B.V. All rights reserved.

Smolentseva E.,National Autonomous University of Mexico | Simakov A.,National Autonomous University of Mexico | Beloshapkin S.,University of Limerick | Estrada M.,Research Center Cientifico Educacion Superior Of Ensenada | And 4 more authors.
Applied Catalysis B: Environmental | Year: 2012

Nanostructured ceria-alumina mixed oxides containing different concentrations of ceria (10 and 30wt.%) were prepared by the sol-gel method using organo-metallic precursors of alumina and ceria. The size of alumina and ceria particles in the prepared Ce-Al-O mixed oxides was smaller than that of pure alumina or ceria. The gold catalysts (3wt.% Au) supported on ceria-alumina mixed oxides by deposition-precipitation (DP) using HAuCl 4 and urea were characterized by several techniques: TEM, XPS and UV-vis spectroscopy, and temperature programmed reduction/oxidation (TPR/TPO). The catalytic activity of prepared Au/CeO 2-Al 2O 3 catalysts in CO oxidation was higher than that of Au/Al 2O 3 and Au/CeO 2 catalysts. Nanostructured ceria incorporated into an alumina matrix has been found quite effective for gold species activation in CO oxidation. In fact, transient analysis of CO oxidation provided an estimate of the relative content of (Au-ceria vacancy) active sites in catalysts. Obtained values are in good agreement with the order of activity for tested samples and gold dispersion according to EXAFS data. © 2011.

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