Deactivation mechanisms of a chromia-alumina catalyst by coke deposition

Abstract

Abstract Catalyst deactivation is a normal phenomenon in catalytic processes and it comes in manyforms — coking, poisoning, aging or sintering. In the case of coking, highly unsaturated, heavy hydrocarbons are adsorbed onto the catalyst active surface and condense leading to coke deposition. In this study, the mechanisms of coke formation as a side reaction from the dehhydrogenation of 1-butene were investigated. The physical modifications in pore volume and surface area show that pore-blocking cause the rapid initial loss in catalyst activity while a slower active site coverage results gradual deactivation there after. However, the characteristics of the coke deposition cannot be described satisfactorily by either parallel or series fouling alone and the combined fouling mechanism is more appropriate. Moreover, the contribution to coke depotition from each of the individual mechanism changes with temperature. A simple model is developed to simulate such coking phenomenon and the results are compared well with the experiments.