JOURNAL OF SOLID STATE CHEMISTRY 87, 378-395 (1990) A Microstructural Investigation of Model Solid State Hydrodesulfurization Catalysts AMIT SACHDEV, JAMES LINDNER, JOHANNES SCHWANK, AND MARIA A. VILLA GARCIA* Department of Chemical Engineering, University of Michigan, Ann Arbor, Michigan 48109-2136; and *Departamento de Quimica Organometcilica, Facultad de Quimica, Universidad de Oviedo, Oviedo-33071, Spain Received August 11, 1989; in revised form April 3, 1990 Model molybdenum disulfide-based solid state synthesis catalysts have been prepared and tested catalytically in the HDS of thiophene. Both promoted and sulfur-deficient samples were prepared and the kinetic analyses were done at temperatures ranging from 473-673 K and atmospheric pressure. Structural characterization was carried out using X-ray diffraction and analytical and high resolution electron microscopy. T_he results indicate that the active catalysts possess a high degree of disorder in the (lOlO), (loll), (1012) directions, which represent the edges of the MoS, crystal. This work also establishes that both Group VIII promotion and sulfur deficiency lead to similar structural changes in the molybdenum sulfide lattice of this specific solid state system. These structural traits can be correlated with increased HDS activity. o 1990 Academic press, IX. Introduction The process of hydrodesulfurization (HDS) involves the removal of sulfur from crude oil feedstocks and is a very important concern of the oil industry for two reasons. From a catalytic viewpoint, sulfur acts as a poison for Pt-based reforming catalysts which are used to form gasoline from the desulfurized crude. From an ecological standpoint, removing the sulfur protects the environment by decreasing SO, pollution. Due to the dependence of industrialized economies on fossil fuels and the scale on which HDS catalysts are employed (an esti- mated 44,200 tons per year in 1986)(Z), stud- ies focusing on the nature of the catalytically active species have been both numerous and extensive. 0022-4596190 $3.00 378 HDS catalysts typically consist of a Group VI metal oxide, such as MOO, or WO,, promoted by a Group VIII oxide, such as Co0 or NiO, supported on alumina. Cur- rently, the workhorse of the HDS industry is the COO/MOO, alumina-supported catalyst, which must be sulfided in order to obtain the active species, whose structure is still under debate. Much of the research conducted in the last 20 years has focused on the nature of the active sites for HDS. This effort has concentrated on seeking a connection be- tween the MoS, phase-promoter interac- tion and the observed catalytic activity. The literature provides many different models to explain the promotional effect (2-12,24). A widely accepted model of the active HDS site assumes that HDS activity is related to the presence of covalently bonded Co on Copyright 0 1990 by Academic Press. Inc. All rights of reproduction in any form reserved.