Reforma a vapor de butanol com catalisadores de Ni,Co/MgAl2O4: efeito da composição do catalisador (Ni,Co) e reagentes (H2,H2O,Butanol) nas rotas reacionais de reação

Abstract

The effect of metal composition (Ni,Co) and the reactants composition (H2:H2O:Butanol) in the catalytic properties were studied for the Ni,Co/MgAl2O4 catalysts in the reaction of steam reforming of butanol (SRB) The catalysts have been prepared by wet impregnation with alcoholic solution of the Co and Ni nitrates on the support of the spinel MgAl 2O4 kind, prepared by the sol-gel method. The catalysts have been characterized by N2 physisorption, X-ray diffraction (XRD), temperatura programmed reduction (TPR), thermogravimetric analysis (TGA) and X-ray absorption near edge structure (H2-XANES). The catalytic tests had been realized in the 150-650°C temperature range, making testes with He flow and others with H2 flow (strongly reducing atmosphere), evaluating conversion, products distribution and H2 selectivity. The XRD reesults confirmed the formation of MgAl2O4 spinel structure and revealed some traces of NiO in the catalyst with 8% of Ni in mass. The TPR helped in the identification of the reducing temperatures of the catalysts. TPD revealed that the main route of butanol’s decomposition in the catalyst surface is the dehydration, producing butylene and etylene. The catalytic tests have indicated another main route, the oxidative dehydrogenation, forming butyraldehyde as the first relevant product of the reaction. The main difference between TPD and catalytic tests is that during the reaction, the presence of water keept the catalyst oxidized in low temperatures. By the XANES evaluation of the results, along with the comparison between TPD and catalytic tests, is suggested that butanol have the tendency to form butyraldehyde when there are more oxide concentration. The TGA revelead that wasn ́t formed significant quantity of the coke in the catalyst surface, probably due to the steam/carbon rate utilized in the catalytic tests. The catalysts had obtained equivalent performance related to H2 selectivty, having some small diferences related to the intermediate products of the reaction, and in the temperature which they were formed during the catalytc tests, as well.