TAP studies of Pt–Sn–K/γ-Al2O3 catalyst for propane dehydrogenation

A Pt–Sn–K/γ-Al2O3 catalyst was prepared by incipient wet impregnation and studied with a temporal analysis of products (TAP) reactor for propane dehydrogenation. Previously to TAP analyses, the catalyst samples were used for propane dehydrogenation in two different reactors: a conventional fluidized bed reactor (FBR) where the catalyst was deactivated in time; and a two zone fluidized bed reactor (TZFBR) where propane and oxygen are fed at different levels, providing separated zones for the reaction and catalyst regeneration thus allowing a continuous mode operation. Several operating conditions were also investigated: different times on stream in the FBR, and in TZFBR at steady state the temperature, the oxygen flow rate and the location of the propane feeding point. Samples of catalyst were obtained at several axial positions in the bed. The amount of coke deposited on the catalyst surface has been determined by thermogravimetric analysis. TAP results show that activation energies for propane conversion are markedly different for catalysts used in FBR and TZFBR; these differences have been related to the different nature of coke present on the catalyst surface.

► TAP as a tool to study the influence of coke in dehydrogenation reactions.
► Activation energies (Ea) are markedly different for catalysts used in FBR and TZFBR.
► Ea differences correlates to the different nature of coke on the catalysts surface.
► In TZFBR the intermediated temperature coke remained unburned.