HYDRODESULFURIZATION AND FCC OF BLENDED STREAM CONTAINING COKER GAS OIL

摘要

A process is described for fixed bed hydrodesulfurizing a non-asphaltic oil feed blend for a zeolitic FCC riser cracking system in which cracking occurs at a space velocity sufficiently high to prevent formation of a catalyst bed. It is found that sulfur dioxide emissions from the zeolite catalyst regenerator associated with the riser are reduced to a lower extent than total sulfur removal from the feed oil. This indicates uneven sulfur removal in the hydrodesulfurization step whereby a smaller portion of sulfur is removed from the heavy portion of the feed from which the coke is derived than from the lighter portion of the feed. The present invention demonstrates a synergistic effect upon sulfur removal from the heavy portion of the feed by widening the boiling range of the feed and this synergistic effect is converted to practical advantage by reducing the amount of hydrodesulfurization catalyst in proportion to said synergistic effect. The further discovery is demonstrated herein that the ratio of gasoline to total conversion during the subsequent riser cracking step is enhanced by reducing the amount of said hydrodesulfurization catalyst as permitted by said synergistic effect and this ratio is further enhanced if a coker gas oil is employed as a blending stream.