GB917088A - Process for the catalytic cracking of hydrocarbon oils - Google Patents

Abstract

In a two stage, vapour phase, process for cracking hydrocarbon oils boiling above gasoline the feed is contacted in a first stage with 5-15 parts of freshly regenerated cracking catalyst in a narrow confined zone at a velocity in the range 2,4-18 m./sec. such that the catalyst will not separate into a pseudo-liquid phase and that the contact time of oil and catalyst is 1-4 seconds while maintaining a conversion of at least 40%, the catalyst is separated and passed to the second stage, the vapours are fractionated together with vapours from the second stage to recover gasoline and an oil boiling above gasoline a part of which is fed to the second stage, such that the ratio of combined feeds to the two stages to fresh feed is 1,5 to 2,8, and there contacted with a fluidized bed of catalyst at a lower temperature than the first stage, a W.H.S.V. of 2,9 to 13,8 with a catalyst residence time less than two minutes but at least five times that in the first stage and a conversion of 10-40%. The first stage temperature is preferably at least 510 DEG C. and in the second stage 56 DEG C. less, and the catalyst residence time in the second stage is preferably not more than 100 seconds. The feed should contain less than 0,5% wt. of material boiling below 232 DEG C. and steam may also be added to either zone. Silica-alumina or activated clay may be the catalyst. Specification 818,219 also is referred to.