Estudo de catalisadores de Zn-V-Nb obtidos a partir de precursores lamelares para a reação de desidrogenação oxidativa do propano

Abstract

Propene is the second most important raw material in the petrochemical industry. It’s used for the production of polypropylene, acrylonitrile, oxy-alcohols, cumene and acrylic acid. The traditional methods to produce are as a by-product in the processes of hydrocarbon pyrolysis and fluidized catalytic cracking. In order to satisfy the increasing in the demand for propylene, some alternative processes are being studied, among them the oxidative dehydrogenation of propane (ODHP). Most catalysts described in the literature are based on vanadium oxides as the main component. On this study, it was used Φz type materials to add Nb in Zn-V structure. The synthesis method of the precursors was the co-precipitation. Catalysts were obtained by calcination of the precursor at 550 ºC during 3 h. The performance of the catalysts were evaluated in oxidative dehydrogenation of propane at temperatures from 350 ºC to 500 ºC. Propane conversion and propene selectivity were measured The technique of X-ray diffraction confirmed that the precursors V100 (no addition of Nb) and V95 (addition of 5% of Nb) have the Φz type structure. The structure indexing was successful. Precursor structures were refined by Rietveld method and the residuals factors were less than 10% for both V100 and V95. Phase identification showed that catalysts are formed by multimetallic oxides except for V0 (addition of 100% of Nb and without V in structure). Rietveld method was used to measure the proportion of the phases. For ODHP, the conversion was greater for the catalyst with Nb in its composition while the selectivity was lower. The addition of Nb in the structure of Zn-V catalysts increased the selectivity. The catalyst obtained by calcination at 750ºC showed the best performance in the ODHP reaction over 400ºC.