Estudo da influência do método de preparação na formação de sítio ativo em catalisadores para a reforma de metanol

• Autor(a) principal: Seixas, Ana Cláudia Mendes de
• Data de Publicação: 1998
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Repositório Institucional da Universidade Estadual de Maringá (RI-UEM)
• Texto Completo: http://repositorio.uem.br:8080/jspui/handle/1/3743
• topic: Catalisadores; Preparação; Catalisadores; Formação de sítio ativo; Metanol; Desenvolvimento de processos; Brasil.; Engenharias; Engenharia Química

In this work it was tried to evaluate the influence of the preparation method of Cu/Zn catalysts, on the generation of the Cu-Zn interaction as well as the efficiency of this interaction in the methanol reforming reaction. The catalysts were prepared in two groups: Cu/ZnO/Al2O3 and Cu/ZnO. For comparison, catalysts were prepared from 1M solutions of Cu(NO3)2.3H2O, Zn(NO3)2.6H2O and Na2CO3, as precipitation agent, through the impregnation and precipitation methods with two different contents of copper for each catalyst type. A mechanical mixture CuO/ZnO was prepared from commercial pure oxides, appraising the alterations in the catalytic behaviour the preparation without intimate mixture. The samples were characterized by: Elementary analysis by atomic absorption, specific surface area (BET), X-ray diffaction, diffuse reflectance espectroscopy (DRS) and temperature programmed reduction (TPR). The TPR and DRS results indicated the presence of the interaction in all the catalysts. The spectra of DRS showed a band between 287 and 291nm that is not related to CuO, nor to ZnO. In the analysis of TPR there was an increase in the content of reduced zinc showing that the interaction with copper leads to a larger reduction of ZnO. The importance of the interaction as responsible for the generation of the active site was checked by the accomplished catalytic test. The methanol reforming reaction was used. It was verificaed that, independent of the preparation method or of the alumina presence, the catalysts with smaller copper content are more active. The ternary catalysts prepared by the impregnation method are the ones which convert more methanol, showing the importance of the interaction Cu-Zn in the conversion, because in these catalysts larger dispersion of the copper on the surface of the zinc oxide occurs, promoting larger exhibition of the interaction .