Fluid catalytic cracking of vacuum gas oil with a refractory fluid quench

Claim 1

In a fluid catalytic cracking process wherein said process takes placed in an apparatus comprising a riser cracking zone at a first temperature for maximum conversion of a vacuum gas oil to debutanized naphtha, a catalyst separation zone and a catalyst regeneration zone, wherein the improvement comprises: a. contacting said vacuum gas oil with a regenerated fluidized cracking catalyst to form a first suspension in an initial portion of said riser cracking zone for a contacting time of about 1.5 to 5.0 seconds at a second temperature at least 5° F. above said first temperature; b. quenching the first suspension in a downstream portion of the riser cracking zone with a refractory fluid prior to said suspension entering said separation zone, said refractory fluid selected from the group consisting of liquid water and steam, to form a second suspension at a third temperature at least 10° F. below said first temperature for a contacting time of about 0.5 seconds or less; c. separating cracking catalyst with deposited contaminants of hydrocarbon cracking from hydrocarbon cracking products of said vacuum gas oil in said catalyst separation zone; d. regenerating separated cracking catalyst with deposited contaminants of hydrocarbon cracking in said catalyst regeneration zone wherein said catalyst is raised to a temperature of about 1100° to 1400° F. to yield a regenerated cracking catalyst wherein deposited contaminants are reduced to about 0.1 wt % or less.