Study of Canadian FCC Feeds from Various Origins and Treatments. 2. Some Specific Cracking Characteristics and Comparisons of Product Yields and Qualities between a Riser Reactor and a MAT Unit

Ten vacuum gas oil feeds were cracked in a fixed-bed microactivity test (MAT) unit and a modified ARCO riser reactor on separate occasions. Several important observations from the MAT study were reported, including the effects of gasoline precursors on the maximum gasoline yields, light cycle oil (LCO) precursors on the optimum LCO yields, and aromatics in feeds on the conversion levels at which the maximum gasoline yields occurred. The yield profiles were similar, in regard to shape and relative position, between H 2 S-free dry gas and catalytic coke for all but one of the feeds. A method to check the qualities of the MAT and riser data was demonstrated by plotting the coke or total gas selectivity versus the gasoline selectivity. Individual yields of gas, liquid, and coke from MAT at conversions of 55, 65, 70, and 81 wt % were compared with their respective pilot-plant data. MAT results, with the exception of coke yield, were, in most cases, within 15% of the corresponding riser yields. Good linear correlations could be established between MAT and riser yields, except for liquefied petroleum gas (LPG) and LCO. Liquid products from MAT were analyzed for hydrocarbon type, sulfur and nitrogen contents, and density, most of which showed good agreement with those obtained from the riser study. The advantages of hydrotreating some poor feeds to improve product yields and qualities were demonstrated and discussed.