Kinetic model and simulation for catalyst deactivation during dehydrogenation of methylcyclohexane over commercial Pt‐, PtRe‐ and presulfided PtRe‐Al2O3 catalysts

Abstract

AbstractThe catalyst deactivation kinetics for the dehydrogenation of methylcyclohexane were studied with Pt‐, PtRe‐, and presulfided Presulfided PtRe‐Al2O3 Catalysts in a fixed‐bed differential reactor. The kinetic analysis was made based on a Langmuir‐Hinshelwood model assuming that the dehydrogenation of methylcyclohexene into methylcyclohexadiene was the rate‐controlling step for the main reaction, and the polymerization of adjacently adsorbed methylcyclohexadiene as coke precursor molecules was the rate‐controlling step for the deactivation reaction. The experimental data for the three catalysts at varying partial pressures of methylcyclohexane and hydrogen were well correlated by the hyperbolic deactivation function derived. The number of active sites involved in the rate‐controlling step of the deactivation was evaluated to be 2.7 in average. The enhanced activity maintenance by the addition of Re as well as sulfur was attributed to a reduction in the concentration of multiple sites occupied by coke precursors adjacently adsorbed, leading to a decrease in the rate constant of the deactivation reaction.