Kinetics of Catalyst Coking in Heptane Reforming over Pt−Re/Al₂O₃

Previous studies have shown that five-membered ring naphthenes (C5N) are the key source of coke in n -heptane ( n C 7 ) reforming on a Pt−Re/Al 2 O 3 catalyst. Using methylcyclopentane (MCP) as a model C5N compound, we develop a kinetic model that predicts its coking rate on the basis of the data obtained from a vibrational microbalance and a fixed-bed reactor. This rate, with an apparent activation energy of 39.7 kcal/mol, decays exponentially in coke-on-catalyst and is first order in MCP partial pressure. Its dependence on H 2 is a combination of negative first and second orders. The model considers that coke deposits randomly on both clean and coked sites a feature that permits the distinction between monolayer and multilayer coke buildup. The model correctly predicts the coking rates of ethylcyclopentane and of n C 7 . Moreover, it predicts the observed coke profile generated from n C 7 reforming in the integral fixed-bed reactor under conditions quite different from those used in the microbalance. As such, the model may be used for probing the state of coking in a reformer and for guiding catalyst-accelerated aging studies.