Kinetic Analysis of Support Effects of Pt-loaded Catalysts on Toluene Hydrogenation at Ambient Pressure

Toluene hydrogenation reaction for methylcyclohexane (MCH) synthesis via Pt-loaded Al2O3 and TiO2 (Pt/Al2O3 and Pt/TiO2) catalysts were investigated in a fixed bed reactor at 398-473 K and ambient pressure. Partial pressures of toluene, hydrogen and MCH were 60 to 91, 9 to 23, and 9 to 17 kPa, respectively. Pt-loaded catalysts showed higher activities in the order of Pt/Al2O3 > Pt/TiO2 (anatase-rutile mixture, AR) = Pt/TiO2 (anatase, A) > Pt/TiO2 (rutile, R) above 423 K, whereas Pt/TiO2 (anatase) showed remarkably higher activities at 393 K. To estimate the effects of support species, kinetic analysis using rate-based model was conducted. The correlation between adsorption behavior and catalytic activities was investigated using a Langmuir-Hinshelwood model. The kinetic constants for each catalyst were almost same. It was considered that only kinetic constants cannot explain the catalytic activities. Coverage of toluene and MCH were independent of the reaction rates, however the reaction rates increased as hydrogen coverage increased for all catalysts.