Kinetics of propane dehydrogenation over Pt–Sn/Al2O3 catalyst

Langmuir–Hinshelwood kinetic models for catalytic propane dehydrogenation on Pt -Sn/Al2O3 are proposed based on the reaction mechanisms that take into account the one step or two-step dehydrogenation and are evaluated by fitting the experiments. When taking into consideration the fitting accuracy, the number of fitting parameters and the rigorousness of the reaction mechanism, the kinetics of propane dehydrogenation based on the assumptions of step-wise dehydrogenation, the first step dehydrogenation as the rate-determining step, and low surface coverage of C3H7 outperforms other kinetic models. The change of catalyst activity with time-on-stream is related to the rate of coke formation that depends on the partial pressures of propene and hydrogen. Finally a complete kinetic model, which includes propane dehydrogenation and cracking and catalyst deactivation because of coking, is developed, which is found to agree well with the changes of propane conversions with time-on-stream under different operating conditions. Direct measurement of coke formation is avoided by the approach employed in this study for the prediction of catalyst deactivation by coke deposition.

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► We modeled kinetics of propane dehydrogenation.
► Model describes kinetics of dehydrogenation, cracking and deactivation.
► First C–H cleavage was identified as the rate determining step.
► Propene was identified as the main precursor for the coke formation.
► Hydrogen suppresses the coke formation.