GB1406837A - High temperature catalytic cracking with zeolite catalysts - Google Patents

Abstract

1406837 Cracking MOBIL OIL CORP 5 Sept 1972 [5 Oct 1971] 41130/72 Heading C5E Hydrocarbon oils are converted to gasoline by (a) combining a first hydrocarbon feed (2) with particles of hot regenerated zeolite catalyst (8) to form a suspension at 1000‹ F. or above; (b) passing this suspension through a first conversion zone (10) to give a residence time of 1 to 12 seconds; (c) separating vaporous product from (b) from catalyst; (d) combining the catalyst from (c) (26) with hot, freshly regenerated catalyst particles (28) and a second hydrocarbon feed (32) more refractory than the first, to form a second suspension; (e) passing this second suspension at 950‹ F. or above through a second conversion zone (36) to give a residence time of 2 to 15 seconds; (f) separating vaporous product from (e) from catalyst; (g) stripping the catalyst from (f); and (h) regenerating stripped catalyst from (g) by burning in an oxygencontaining gas. The first feed may be a fraction of low molecular weight, the second of higher molecular weight; or the first may be a virgin gas oil and the second a coker gas oil, recycle oil or residual stock. The catalyst may contain two different zeolites, and may also contain a metal oxide that will enhance regeneration by catalysing the conversion of CO to CO 2 , e.g. chromium oxide. As shown, a first feed is heated in furnace 4, diluted if desired by steam or light hydrocarbons at 6, combined with regenerated catalyst from standpipe 8 and cracked in riser 10. Further portions of feed may be injected at 7<SP>1</SP> and 7<SP>11</SP> to adjust the residence time. The cracked material is discharged through cyclone separators 11 into hopper 14; the vaporous product is collected at 12 and taken off at 16, the catalyst is collected in dense bed 20, where it is stripped by steam from a line 22. A vertical baffle 24 separates catalyst beds 20 and 40, but the upper parts of the hopper are in open communication. Catalyst is withdrawn from bed 20, while still hot, by standpipe 26 and mixed with freshly regenerated catalyst from standpipe 28. The second feed 32 is cracked in a similar fashion to the first, but using a lower temperature, longer residence time, higher catalyst-to-oil ratio, and mixed catalyst from the standpipes 26 and 28. The product is separated in cyclone 38, and the catalyst passes to bed 40 and is stripped there. Catalyst fines in the stripping gases are removed by the central cyclone and returned to bed 40. Catalyst is withdrawn from bed 40 by standpipe 44, suspended in air from line 46 and carried into regenerator 52. In Fig. 4 (not shown) the baffle 24 has slots for controlled flow of catalyst between the two beds 20 and 40. In Fig. 5 (not shown) the catalysts from both reaction zones discharge into a common bed; part of this catalyst is withdrawn from a point above the stripping zone to be used in the second cracking zone, another part is withdrawn from below the stripping zone and sent to the regenerator; alternatively both streams can be taken from below the stripping zone. In this modification also a third feed can be injected into the dense bed, and used to control the amount of coke deposited on the catalyst, and so the temperature of the catalyst leaving the regenerator.