FCC Study of Canadian Oil-Sands Derived Vacuum Gas Oils. 2. Effects of Feedstocks and Catalysts on Distributions of Sulfur and Nitrogen in Liquid Products

Abstract

This study was conducted in an effort to learn more about the roles of feedstock and catalyst in the distributions of sulfur and nitrogen in liquid products after catalytic cracking. A hydrotreated coker gas oil, a hydrotreated deasphalted oil, a virgin gas oil, all derived from Canadian oil-sands bitumen, were catalytically cracked in a fluid bed microactivity test (MAT) unit with two commercial catalysts. These were the equilibrium catalysts, bottoms-cracking and octane-barrel catalysts, respectively, both containing active matrixes. The cracked liquid products were analyzed for sulfur and nitrogen distributions with boiling point, from which the sulfur and nitrogen contents of gasoline, light cycle oil (LCO), and heavy cycle oil (HCO) fractions were determined. Variations of concentrations in each product cut with conversion were discussed, along with the hydrogen transfer indices of catalysts and the hydrogen yields of feeds. The overall distribution of feed sulfur in cracked products, and the relationship of the sulfur content of feed with that of LCO, confirmed the findings reported in the literature. The same three feeds were also cracked with the octane-barrel catalyst in a riser pilot plant. The sulfur and nitrogen concentrations in each product fraction from MAT were found to be in reasonably good agreement with those obtained from the riser pilot plant operation. Results from this study will provide the scientific community with a better understanding about the cracking chemistry of sulfur- and nitrogen-containing species in gas oils under different test environments.