Selectivity and Yield of Components of a Composite Cracking Catalyst: Effect of Interactions between Composite Components

Abstract

Coking, activity, and product distribution of a composite catalyst and its components, an REY zeolite and a silica-alumina matrix, are studied in the cracking of n-hexadecane at 500°C in a pulse microreactor equipped with a thermogravimetric analysis unit (TGA), an integral sample collector, and a GC. The matrix component alone does not show significant activity beyond thermal cracking. The zeolite component has high activity and high coking rate. The composite catalyst shows much higher conversion, much higher yield to C 5-C 10, and much lower coking rate than the values predicted from its components. The activity and the product distribution are affected by coke deposition, and this effect depends on coke level of the catalysts. Product yields for the three catalysts as functions of coke levels allow us to determine yield enhancement factors and selectivity enhancement factors (referring to the zeolite component in the composite catalyst relative to the pure zeolite catalyst at the same zeolite coke level) for four product groups. Examination of the selectivity enhancement factors indicates how the heaviest products (C 17+) from the matrix component of the composite catalyst convert to kerosene, gasoline, and lightest (C 4−) product groups over the zeolite component of the composite catalyst, and how these interconversions change with the coke level on the zeolite.