Process for catalytic cracking of petroleum based feed stocks

Abstract

A process for selective catalytic cracking of a petroleum-based feedstock to produce a product having a high yield of liquified petroleum gas (LPG) and light olefins having 3 to 4 carbons includes providing a fluidized bed reactor which is a high velocity riser, continuously circulating fluidized bed reactor; providing a solid acidic catalyst comprised of: from 1 to 6% by wt. of ultra stable Y-zeolite; from 8-25% by wt. of Pentasil zeolite which is shape selective; from 0-8% by wt. of an active material which is bottom selective; from 0-1% by wt. of rare earth constituents; and from 91 to 60% by wt. of nonacidic constituents and binder; charging the fluidized bed reactor with the solid acidic catalyst and the petroleum-based feedstock; and cracking the petroleum-based feedstock in the presence of the solid acidic catalyst in the fluidized bed reactor. The reactor is operated at a Weight Hourly Space Velocity (WHSV) ranging from 40 to 120 hr.sup.-1, a ratio of solid acidic catalyst to petroleum-based feedstock ranging from 15 to 25, a temperature at the top of the high velocity riser ranging from 530.degree. C. to 600.degree. C., recycled riser products ranging from 0 to 40%, a pressure in the fluidized bed reactor ranging from 1.0 to 4.0 kg/cm.sup.2 g, and an amount of steam for dilution and quenching of hydrocarbons ranging from 3 to 50 wt. % of the petroleum-based feedstock. The Pentasil zeolite has a pore size ranging from 5 to 6 .ANG. so that the catalyst is highly selective for LPG and C.sub.4 light olefins with minimum dry gas and coke make, and so that the vanadium tolerance of the catalyst is increased and ranges up to 21,000 PPM. The process produces a LPG yield ranging up to 40 to 65 wt. % of the fresh petroleum-based feedstock, a selectivity for the light olefins of at least 40 wt. %, and a selectivity for the LPG of at least 45 wt.