Desenvolvimento de catalisadores de NiAl2O4 por reação de combustão para reforma a vapor de metano.

Abstract

This research involves the preparation and characterization of NiAI204 catalysts by combustion reaction, using urea and glycine as fuel, and to evaluate their catalytic performance of them in steam reforming of methane. The catalysts were obtained according to the propellants chemistry, with ratios Oe = 1 (stoichiometric), <Pe <1 (fuel-rich) and Oe > 1 (fuel-deficient), using a vitreous silica crucible. During the synthesis the combustion parameters as flame time and temperature were measured. The samples were characterized by X-ray diffraction (XRD), infrared spectroscopy (FTIR), agglomerate size distribution, gas picnometry, textural analysis (BET/BJH), scanning electronic microscopy (MEV), temperatureprogrammed reduction (TPR), and then, catalytically evaluated in the methane reforming reaction. It was observed that the type and fuel content, used in the catalysts preparation, interfered significantly in the reaction behavior, and consequently, in their structure and morphology. All the catalysts presented the NiAI204 spinel as major phase, and NiO and Ni as secondary phases, besides of a large median agglomerates size distribution. Structurally it was observed that the samples obtained with urea presented an increase in the crystallite size and crystallinity with the increasing fuel content. On the other hand, for the samples obtained with glycine, the behavior was almost opposite, because with the increasing fuel content, smaller crystallite size and crystallinity were observed. Regarding morphology, it was observed the presence of large agglomerates with large size distribution for all compositions, especially for those obtained with urea. However, it was also observed that the samples obtained with urea presented rigid agglomerates, constituted of interconnected fine particles and large surface area, whereas for the samples obtained with glycine, foamy and soft agglomerates, and smaller surface area were observed. Regarding the catalytic tests, all the samples presented high methane conversion to synthesis gas, but with rapid deactivation, due to coke deposition on the active phases surfaces.