Cinética da produção de butenos a partir de butanol empregando catalisadores ácidos

Abstract

to environmental requirements, new producing routes have been pursued and the butanol dehydration reaction is one of the most promising. HZSM-5 zeolites and -alumina acid catalysts were synthesized at different conditions to investigate the effects of their acid properties on catalyst activity in this reaction. The catalytic tests were carried out following a complete factorial design. The results evinced that there is a great influence of feeding rate on butanol conversion, exhibiting a characteristic profile of chemical reaction with order lower than 1. The conversion obtained with the zeolites were always higher than the ones obtained with the aluminas at all reaction temperatures, even though less catalyst mass was employed, which indicates a higher activity of this catalyst. Selectivity to 2-butene was higher than the primary olefin selectivity for the HZSM-5; while, the aluminas almost did not isomerized 1- butene, with selectivity of approximately 98% in all tests. The SAR of the HZSM-5 presents impact on the activity of this material, the lower the SAR is, more active is the catalyst. The zeolites with SAR 30 and 40 presented high conversions of butanol and concentrations of isomerization product than SAR 50. For the aluminas, the highest catalytic activity was observed for the sample calcined at 600 °C. After calculating the molar fraction of the products at the reactor outlet, parameter estimation of the proposed kinetic models was performed. The results from the models confirmed the higher activity of the HZSM-5 and also validated the effect of the zeolite SAR and the calcination temperature of the aluminas on the reaction selectivity. Heterogeneous models fitted better the experimental data than pseudohomogeneous models. Comparing different kinetic models, it was observed that the butanol adsorption is the only significant hypothesis in model fitting to the experimental data. The adsorption of other molecules, such as 2-butene, isobutene and water, could be disconsidered in the best model formulation.