Hydrodesulfurzation of thiophene over the molybdenum-based catalysts supported on activated carbon

Abstract

A series of Co and Mo catalysts supported on activated carbon were prepared, and their catalytic behaviors were investigated and compared with those of the conventional alumina supported CoMo catalysts. The objectives of the present work are; i) to examine the characteristics of hydrodesulfurization (HDS) and hydrogenation (HYD) activities of carbon supported CoMo catalysts relative to alumina supported catalysts and ii) to elucidate the properties of the synergistic active sites which arise from the result of Co-Mo interaction. In the first part of this work, the kinetic study for HDS of thiophene was made on three commercial catalysts from Harshaw Co., CoMo/$Al_2O_3$(HT 400E), NiMo/$Al_2O_3$(HT 500E) and NiW/$Al_2O_3$(Ni 4301E). Fourteen kinetic models of Langmuir-Hinshelwood typewere discriminated for each catalyst using a nonlinear regression method. Adsorption equilibrium constants at the reaction temperature were obtained through independent measurement by the chromatographic pulse technique. The same type of rate equations were selected irrespective of the kinds of active metals, but the NiW system showed a relatively higher hydrogenation functionality through weaker adsorption of thiophene and $H_2S$ than those for the CoMo or NiMo system. Hydrogen adsorption was found to be very weak compared to other reactants and not of dissociative type under the present reaction conditions. The kinetic and adsorption parameters estimated through kinetic modeling were well consistent with those of the separate adsorption measurements. In the second part, reduction characteristics of Co or Mo oxide catalysts supported on activated carbon and alumina were studied under hydrogen atmosphere using a flow microbalance reactor. The characteristic of Co or Mo oxide catalyst supported on carbon was explained in terms of the interaction between support and active metal phase, the dispersion and the thermal behavior. The results of temperature programmed reduction (TPR) and re...