Gold catalysts supported on cerium-gallium mixed oxide for the carbon monoxide oxidation and water gas shift reaction

The synthesis, characterization and catalytic properties of gold supported on ceria, gallia and a cerium-gallium mixed oxide were investigated. The nanostructural characterization of the cerium-gallium support (nominal atomic composition Ce80Ga20) showed that gallium(III) cations are homogenously distributed into the ceria matrix by substituting cerium(IV) cations of the fluorite-type structure of ceria. Au was added to the supports by the deposition-precipitation method using urea. High Au dispersions were achieved for all the fresh materials (D > 60%). The CO oxidation and the water gas shift (WGS) reaction were tested on the whole set of catalysts. All the supported-gold catalysts showed high activity for the CO oxidation reaction. However, those containing gallium in their formulation deactivated due to gold particle sinterization. Au(2%)/CeO2 was the most active material for the WGS reaction, and the Au(2%)/Ce80Ga20 was as active as a Au(3%)/Ce68Zr32 catalyst for CO oxidation, and even more active than the reference catalyst of the World Gold Council, Au(2%)/TiO2.Fil: Vecchietti, María Julia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; ArgentinaFil: Collins, Sebastián Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; ArgentinaFil: Delgado, Juan José. Universidad de Cadiz. Facultad de Ciencias. Departamento de Cs.de Los Materiales E Ing.metalurgica y Quim.inorg.; EspañaFil: Malecka, Malgorzta. Universidad de Cadiz. Facultad de Ciencias. Departamento de Cs.de Los Materiales E Ing.metalurgica y Quim.inorg.; EspañaFil: del Rio, Eloy. Universidad de Cadiz. Facultad de Ciencias. Departamento de Cs.de Los Materiales E Ing.metalurgica y Quim.inorg.; EspañaFil: Chen, Xiaowei. Universidad de Cadiz. Facultad de Ciencias. Departamento de Cs.de Los Materiales E Ing.metalurgica y Quim.inorg.; EspañaFil: Bernal, Serafín. Universidad de Cadiz. Facultad de Ciencias. Departamento de Cs.de Los Materiales E Ing.metalurgica y Quim.inorg.; EspañaFil: Bonivardi, Adrian Lionel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentin

Molecular Structure and Thermal Stability of Oxide-Supported Phosphotungstic Wells-Dawson Heteropolyacid

We present, for the first time in literature, a systematic study of the molecular structure of the Wells-Dawson heteropolyacid H6P2W18O62.24H2O (HPA) dispersed on TiO2, SiO2, ZrO2 and Al2O3. The heteropolyacid-based materials were synthesized through a conventional impregnation method (in aqueous and ethanol media) at a loading that corresponds to the theoretical monolayer coverage (dispersion limit loading). The combination of Raman and infrared studies demonstrates the presence of crystals of HPA (regardless of the nature of the medium used during the synthesis) suggesting that the dispersion limit loading was greatly exceeded. In situ temperature programmed analyses demonstrated that the Raman shift of the distinctive W=O Raman mode of the fosfotungstic Wells-Dawson heteropolyacid is sensitive to the local environment, that is the amount of water molecules associated with the structure. Moreover, the aqueous based species associated with such structures are recognizable through infrared spectroscopy.Fil: Matkovic, Silvana Raquel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico la Plata. Centro de Investigación y Desarrollo En Ciencias Aplicadas; ArgentinaFil: Collins, Sebastián Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Santa Fe. Instituto de Desarrollo Tecnológico Para la Industria Química (i); ArgentinaFil: Bonivardi, Adrian Lionel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Santa Fe. Instituto de Desarrollo Tecnológico Para la Industria Química (i); ArgentinaFil: Bañares, Miguel A.. CSIC, Consejo Superior de Investigaciones Cientificas, Instituto de Catalisis y Petroquimica.Catalytic Spectroscopy Laboratory; EspañaFil: Briand, Laura Estefania. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico la Plata. Centro de Investigación y Desarrollo En Ciencias Aplicadas; Argentin

Reformado de Etanol: Estudio de la Adsorción y Descomposición de Etanol sobre Óxidos Mixtos de Cerio-Galio

En este trabajo se estudió la adsorción y reacción superficial a temperatura programada de etanol sobre CeO2 puro y óxidos mixtos de Ce-Ga mediante espectroscopia infrarroja por reflectancia difusa y espectrometría de masas. La correlación de los resultados obtenidos por ambas técnicas permitió plantear un mecanismo para la reacción de etanol con la superficie de los soportes estudiados. El etanol se adsorbe disociativamente formando especies etoxi. Dichas especies se descomponen a partir de 150 °C para dar grupos acetato. Por encima de 190 °C se observó la liberación de etileno en el caso del CeO2 y Ga2O3, pero no para los óxidos mixtos de Ce-Ga. Luego de la descomposición, los restos carbonosos fueron oxidados a temperatura programada con O2, y se observó que la evolución de CO2 fue al menos el 40 % mayor en el CeO2 respecto de los óxidos mixtos. Estos resultados sugieren que el etileno puede ser una de las fuentes de formación de coque sobre estos materiales. Se propone que la incorporación de cationes Ga3+ a la ceria mejora su comportamiento oxidativo, lo que redundaría en una mayor estabilidad de los catalizadores basados en Ce-Ga frente al reformado de etanol con vapor de agua para la producción de hidrógeno.Fil: Vecchietti, María Julia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; ArgentinaFil: Giordano, Sofía. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; ArgentinaFil: Mohr, Susanne. Universitat Erlangen-Nuremberg; AlemaniaFil: Collins, Sebastián Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; ArgentinaFil: Libuda, Jörg. Universitat Erlangen-Nuremberg; AlemaniaFil: Bonivardi, Adrian Lionel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; ArgentinaXXVI Congresso Ibero-Americano de CatálisePortugalSociedade Portuguesa de QuímicaUniversidade de Coimbr

Mechanism of the decomposition of adsorbed methanol over a Pd/α,β-Ga2O3 catalyst

The thermal decomposition of adsorbed methanol on 2 wt.% Pd/silica, 2 wt.% Pd/gallia and pure gallia, was studied by temperatureprogrammed surface reaction (TPSR), between 323 and 723 K under He flow, using FT-IR spectroscopy. After methanol adsorption on Pd/silica at 323 K, the concentration of methoxy species on the silica decreased during the TPRS experiment, but some methoxy groups still remained on this support even at 723 K. Simultaneously, methanol decomposed over metallic palladium to yield, stepwise, HCO and CO with the consequent release of H2 (g). On clean gallia, methanol is Lewis-bound adsorbed to the surface, as well as dissociatively adsorbed as methoxy (CH3O), but the position of the infrared bands indicates a stronger interaction of these species on gallium oxide than on silica. Methoxy species on gallia are decomposed to (mono- and bi-dentate) formate groups (m- and b-HCOO, respectively) at T > 473 K. We suggest that CO and CO2 are further produced by nonstoichiometric transformation of these formates, leading to the release of atomic hydrogen on the surface of the oxide, as detected by the Ga–H stretching infrared band, and surface anion vacancies. In the presence of Pd on the gallia surface, the dehydrogenation of CH3O species proceeds faster than over the pure oxide, and we propose the following mechanism for methanol decomposition: (i) methanol reacts with OH groups on the gallia surface to produce water and methoxy species, (ii) the dehydrogenation of the latter carbonaceous group leads to H2COO, first, and then to mand b-HCOO, (iii) the hydrogen atoms released in the previous steps are transferred from gallia to the Pd surface where they recombine and desorb as H2 (g).Fil: Collins, Sebastián Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; ArgentinaFil: Baltanas, Miguel Angel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; ArgentinaFil: Bonivardi, Adrian Lionel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentin

FTIR Study of the Adsorption of Methanol on Clean and Ca-promoted Pd/SiO2 Catalysts.

The adsorption and decomposition of methanol on a highly dispersed supported Pd/SiO2 catalyst (2% Pd w/w) prepared via ion exchange of [Pd(NH3)4]2+ in alkaline solution, together with two Ca-promoted preparations (Ca/Pd=2 at/at), where calcium was added either to the prereduced Pd crystallites or to the diammine palladium complex, were studied by FTIR at 298–623 K. Methanol adsorbs and reacts at 298 K on Pd/SiO2. The presence of Pd on the silica surface influences slightly the processes occurring on the support, where CH3OH is mostly adsorbed molecularly at room temperature, but readily forms very stable Si–O–CH3 groups upon heating. The dissociation of methanol via both O–H and C–O bond breaking is observed on Pd. The latter scission is only detected at 653 K. At room temperature, adsorbed CH3OH decomposes easily on the Pd crystallites, to give CO multicoordinated to the metal surface. Formyl species were also found at this temperature, but they promptly disappeared, above 393 K, when the catalyst was heated. Calcium promotion, either to the prereduced Pd or to its diammine complex precursor during the preparation steps, enhances methanol decomposition onto the catalyst surface, even at room temperature. With heating, formyl groups are replaced by mono- and bi-dentate formate species, which are chemisorbed on the support and/or the promoter. Bidentate formate is not as stable as the monodentate form and its IR band vanishes above 500 K. The observed features indicate that an excellent Ca–Pd intimacy was achieved with both types of promotion strategies.Fil: Cabilla, Griselda. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; ArgentinaFil: Bonivardi, Adrian Lionel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; ArgentinaFil: Baltanas, Miguel Angel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentin

Infrared Study of the Absorption of Formic Acid on Clean and Ca-promoted Pd/SiO2 Catalysts

The adsorption and decomposition of formic acid on a highly dispersed supported Pd/SiO2 catalyst (2 wt.% Pd) prepared via ion exchange (IE) of [Pd(NH3)4]2+ in alkaline solution, together with two Ca-promoted preparations (Ca/Pd=2 at./at.) where calcium was added either to the prereduced Pd crystallites or to the diammine palladium complex, were studied by FTIR at 298–653 K. On the support, HCOOH is mostly adsorbed molecularly at room temperature, with partial dimerization, condensation and extensive hydrogen bonding, but readily decomposes, on the Pd crystallites of Pd/SiO2, via decarbonylation, to give CO multicoordinated to the metal surface, and water. With heating, formic acid decomposition is accompanied by some water gas shift as well, while CO reacts to give methyl (methane) and methoxy. Calcium promotion to both the prereduced Pd and its diammine complex precursor, enhanced HCOOH decomposition onto the catalyst surface, even at 298 K. Together with sorbed HCOOH and chemisorbed CO, mono- and bidentate formates were observed on these materials, owing to the incorporation of well-dispersed CaOxHy. These formates were readily decomposed by atomic hydrogen produced by decarbonylation/WGS of formic acid on Pd. At increasing temperatures, some carbonates (polydentate and simple) were formed, but hardly any methane was detected. On Ca–Pd/SiO2 with calcium added to prereduced Pd metal particles the extension and/or onset of all these processes was more straightforward than on the promoted Ca–Pd/SiO2 where calcium was added to diammine palladium instead, most likely owing to the combined impact of a higher dispersion of the Pd crystallites on the former preparation, and calcium oxyhydroxide decoration (CaOxHy) of the metal particles on the latter, which hamper H-spillover from them.Fil: Cabilla, Griselda. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; ArgentinaFil: Bonivardi, Adrian Lionel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; ArgentinaFil: Baltanas, Miguel Angel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentin

Artificial neural networks study of the catalytic reduction of resazurin. Stopped-flow injection kinetic-spectrophotometric determination of Cu(II) and Ni(II)

An artificial neural network (ANN) procedure was used in the development of a catalytic spectrophotometric method for the determination of Cu(II) and Ni(II) employing a stopped-flow injection system. The method is based on the catalytic action of these ions on the reduction of resazurin by sulfide. ANNs trained by back-propagation of errors allowed us to model the systems in a concentration range of 0.5–6 and 1–15 mg l-1 for Cu(II) and Ni(II), respectively, with a low relative error of prediction (REP) for each cation: REPCu(II) = 0.85% and REPNi(II) = 0.79%. The standard deviations of the repeatability (sr) and of the within-laboratory reproducibility (sw) were measured using standard solutions of Cu(II) and Ni(II) equal to 2.75 and 3.5 mg l-1, respectively: sr[Cu(II)] = 0.039 mg l-1, sr[Ni(II)] = 0.044 mg l-1, sw[Ni(II)] = 0.045 mg l-1 and sw[Ni(II)] = 0.050 mg l-1. The ANNs-kinetic method has been applied to the determination of Cu(II) and Ni(II) in electroplating solutions and provided satisfactory results as compared with flame atomic absorption spectrophotometry method. The effect of resazurin, NaOH and Na2S concentrations and the reaction temperature on the analytical sensitivity is discussed.Fil: Magni, Diana. Universidad Nacional del Litoral; ArgentinaFil: Olivieri, Alejandro Cesar. Universidad Nacional de Rosario; ArgentinaFil: Bonivardi, Adrian Lionel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentin