Additive for vanadium and sulfur oxide capture in catalytic cracking

摘要

A catalytic cracking process especially useful for the catalytic cracking of high metals content feeds including resids in which the feed is cracked in the presence of a catalyst additive comprising an alkaline earth metal oxide and an alkaline earth metal spinel, preferably a magnesium aluminate spinel which acts as a trap for vanadium as well as an agent for reducing the content of sulfur oxides in the regenerator flue gas. The additive is used in the form of a separate additive from the cracking catalyst particles in order to keep the vanadium away from the cracking catalyst and so preserve the activity of the catalyst; in addition, use of separate additive particles permits the makeup rate for the additive to be varied relative to that of the cracking catalyst in order to deal with variations in the metals and sulfur content of the cracking feed. The additive may be separated from the cracking catalyst by physical classification so that it can be separately withdrawn from the unit for better control of the catalyst/additive ratio. The additive may be injected into the unit separate from the cracking catalyst so that it contacts the feed first to effect a preliminary demetallation.