Cracking of Butane on a Pt/H-ZSM-5 Catalyst in the Presence of Hydrogen

This work provides a detailed interpretation of the complex reaction mechanisms of n-butane on Pt/H-ZSM-5 catalyst in the presence of H2 from the perspective of kinetics. In one route, n-butane conversion involved dehydrogenation on Pt to form butene and isomerization, dimerization, and cracking steps on the acid sites in the zeolite. Alternatively, butane could have underwent direct protolytic cracking on zeolite. On zeolite surfaces dominated by unoccupied Brønsted acid sites, protolytic cracking of butane was the preferred primary cracking mechanism. As the coverage of C4 surface adsorbate increased, the routes via butene became prominent and likely dominated under practical conditions with high hydrocarbon partial pressures. The various reaction pathways all followed the Langmuir–Hinshelwood rate model. With over 90% combined selectivity of propane and ethane at nearly full butane conversion and good catalyst regenerability, this mechanism presents an effective way to convert butane fuel to chemical feedstocks.