Catalytic combustion of methane by palladium-supported molecular sieves / Combustão catalitica de metano usando paladio suportado em peneiras moleculares

AUTOR(ES)
DATA DE PUBLICAÇÃO

2005

RESUMO

The partieipation of the natural gas in energy generation has grown significantly in the last years in Brazil as well as in the world. Its use in the combustion generates emission pollutants in lower degrees when compared to other fossils fuels. This is very important in times when the goals of the Kyoto s protocol have to be achieved. In this sense, the Brazilian government encourages the use of the natural gas aiming at achieving, in 2010, a participation of up to 12% of this fuel in the energy matrix of the country. This Thesis had the objectíve to study the feasibility of the use of molecular sieves as supports for palladium catalysts, in the reaction of catalytic combustion of methane, for energy generation at lower temperatures. For that, micro and mesoporous molecular sieves of the kind of ETS-10, (Si and AI)-MCM-41 and meso-SAPO were prepared. The thermal stabilities of these molecular sieves indicated that for the reaction of interest, only the MCM-41 would be useful, either as purely silicate (Si-MCM-41) or as aluminumsilicate (AI-MCM-41). Also the effects caused by additives such as cerium, lanthanum and zirconium, introduced by impregnation in the supports before the impregnation of the palladium were studied. MCM-41 structure presented good thermal stability until 900 °C and the silicate composition (Si-MCM-41) showed to be more stable than the AI-MCM-41. The presence of palladium oxide (PdO) in the catalysts was also observed during characterization. The catalysts of both series Si-MCM-41 and AI-MCM-41 were active in the reaction of interest. Palladium supported in Si-MCM-41 presented better activity than when supported in the AI-MCM-41. This fact can be related with the difference in the hydrofilic/hydrofobic character of the support. The acidification process in the MCM-41 supports before palladium impregnation got better the catalytie performance, while the presence of additives in the mesoporous supports did not improve the catalytic performance as expected, probably due to the fact that the additives in the supports surface made the interaction between palladium and MCM-41 more difficult. In fact, Pd/H-Si-MCM-41 and Pd/H-AI-MCM-41 catalysts showed to be more efficient for the activation of the methane combustion.

ASSUNTO(S)

gas natural methane metano paladio natural gas catalytic combustion palladium molecular sieves combustão catalitica

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