Hydrogenation by CoMo/Al2O3 catalyst. (Part 1). Effect of catalyst pretreatment on hydrogenation of monoaromatic hydrocarbons.

Abstract

Effects of reduction and sulfidation pretreatments on the hydrogenation activity of Co-Mo/alumina catalysts were studied. Reactions adopted for the activity tests were hydrogenation of benzene, toluene, and o-xylene, carried Out over pretreated catalysts at 400°C under flowing H2 or H2S/H2 at 5MPa. The hydrogenation was followed by skeletal isomerization, irrespective of the substrate and reaction conditions. The activity sequence among the variously pretreated catalysts in descending order was: sulfided>presulfided/reduced>prereduced/sulfided>fresh>reduced. The reaction of o-xylene was most sensitive to pretreatment, and attained its maximum conversion when the reaction was carried out over the sulfided catalyst and under flowing H2S/H2. Catalysts sulfided at higher temperatures exhibited higher catalytic activities. The catalytic activity was determined principally by the amount of sulfur incorporated in the catalyst.