Reaction Kinetics of the Hydroenitrogenation of Decahydroquinoline over NiMo(P)/Al_2O_3 Catalysts

摘要

The reaction mechanism and the kinetics of hydrodenitrogenation (HDN) of decahydroquinoline (DHQ) over NiMo(P)/Al_2O_3 catalysts were studied in the presence and absence of H_2S. Cis- and trans-propylcyclohexylamine were identified as the most important reaction intermediates; thei reactivity was found to vary under different reaction conditions. The kinetic constants in the HDN network of DHQ were calculated assuming a Langmuir-Hinshelwood mechanism. It was found that, in the phosphorus-containing catalysts, the adsorption of DHQ was enhanced and the rate constant of the first C-N bond cleavage decreased. As a consequence, the overall HDN reaction rate of DHQ decreased when phosphorus was added to a NiMo/Al_2O_3 catalyst. The effect of H_2S was the opposite of that of phosphorus: it increased the rate constants and decreased the adsorption constants. The inhibiting effect of DHQ in its own conversion was different from that on the hydrogenation of cyclohexene, proving that different catalytic sites are involved in these reactions.