Kinetics and Reaction Pathways for Propane Dehydrogenation and Aromatization on Co/H-ZSM5 and H-ZSM5

Abstract

Co/H-ZSM5 catalyzes propane dehydrogenation and aromatization reactions. Initial product selectivities, product site-yields, and the 13C content and distribution in the products of 2-13C-propane show that propane undergoes two primary reactionsdehydrogenation to propene and H2 and cracking to methane and ethene. Propene and ethene then form aromatics via oligomerization−cracking reactions and both ethene and propene hydrogenate to form ethane and propane, respectively, via both hydrogen transfer from coadsorbed intermediates and dissociative adsorption of H2. These reaction pathways resemble those occurring on H-ZSM5, but Co cations provide an alternate pathway for the removal of hydrogen atoms in adsorbed intermediates as H2. A kinetic model was used to describe experimental rates based on these observations and to obtain rate constants for individual reaction steps as a function of Co content and H2 concentration. H2 inhibits propane dehydrogenation to propene and alkene conversion to aromatics, and inc...