Efeito difusivo externo sobre a atividade catalítica dos catalisadores A10/Zn0 e Cr0/Zn0.

Abstract

External Mass Transport is one of the stages, which can be present in a heterogeneous catalytic process, however, most of the works are developed outside the conditions in the 4 is esue ofoi may be present, this because being a physical process it does not reveal information about catalyst structure or reaction kinetics. As a result, few publications found in the literature with test data from external diffusion. In this study, the effect of the time factor (W / F a), reagent composition and reaction temperature on external diffusion in Al 0 / ZnO and Cr0 / ZnO catalysts was evaluated, using isopropanol decomposition as a model reaction. The tests were carried out in a tubular reactor at atmospheric pressure and 360º C. There was a strong influence of the concentration of the reagent on the external diffusive effect reaching the total annulment, this effect for 40% concentration in moles of alcohol in the food for both catalysts. No effect of external mass transport was observed for W / Fa values ​​below 1.0 gcat.h / mol reag. for the Al 0 / ZnO catalyst and below 3.0 gcat.h / mol reac. for the Cr0 / ZnO catalyst, for a 100% alcohol feed. The low activation energies (Ea) obtained, 26.98 Kcal / mol for Al 0 / ZnO and 19.46 Kcal / mol for Cr0 / ZnO also indicate the presence of the external diffusive effect in these catalysts for the studied temperature range.