Determination of the Intrinsic Activity and Effective Diffusivity of Aged Coal Liquefaction Catalysts

摘要

Although severe, rapid catalyst deactivation remains a major economic impediment to the production of liquid fuels from coal by direct processing, there have been few quantitative investigations of aged catalyst intrinsic activity and effective diffusivity. This study reports a method for determining these important properties under experimental conditions that accurately model actual conditions for the processing of coal-derived liquids. The power of the technique has been demonstrated by determination of the intrinsic hydrogenation activity and effective diffusivity of catalysts obtained from the Wilsonville, Alabama coal liquefaction test facility. The values of intrinsic catalyst activity and effective diffusivity reported here are based on kinetic measurements of the catalytic hydrogenation of pyrene. Pyrene was chosen as a chemical probe of these properties because it appears to play a key role as a hydrogen transfer agent in coal liquefaction. From determination of the pyrene hydrogenation rate constants for pairs of experiments, one with powdered catalyst and the other with whole extrudates, the fraction deactivated and the Thiele modulus, which relates the intrinsic rate constant to the extrudate effective diffusivity, were determined. Experiments with fresh, aged and regenerated catalysts have allowed the contribution of deactivation due to metallic contaminants to be separated from that due to carbonaceous material, and thus has allowed the mode of deactivation for each contaminant to be determined. 13 references, 4 figures, 3 tables. (ERA citation 09:032537)