Catalytic hydrodesulfurization of dibenzothiophene and a coal-derived liquid

Abstract

The catalytic hydrodesulfurization (HDS) reactions of both specific organosulfur compounds and a coal-derived liquid were studied in a continuous, back-mixed, internally circulated (gradientless) laboratory reactor using a commercial cobalt-molybdenum on alumina catalyst. The HDS of dibenzothiophene yielded experimental reaction rates that were adequately correlated by a Langmuir-Hinshelwood relationship. The computed activation energy and heats of adsorption computed compare quite well with values reported in the literature. The HDS of other thiophenic compounds demonstrated the effects that different alkyl substituents located on the thiophene ring would have on the sulfur-removal reactivity of these compounds relative to the HDS reactivity of dibenzothiophene. Coal-derived liquids were prepared by the batchwise solvent extraction and hydrogenation of a Herrin (IL) No. 6 coal with tetrain, toluene, and hydrogen. The coal was then catalytically hydrotreated by the same HDS procedure. The HDS rates measured were very adequately represented by a kinetic model that was first-order with respect to the total sulfur concentration and first-order with respect to hydrogen pressure. The value of the activation energy of the HDS pseudoreaction rate constant also compares quite well with those reported in literature, in spite of differences in catalysts, reactor designs, and feed coal liquid origins and compositions.