GB782024A - Improved method for preparing and catalytically cracking petroleum residuum fractions - Google Patents

Abstract

In a process for the catalytic cracking of petroleum residual oils, the residual oil is subjected to distillation under reduced pressure at an equivalent atmospheric-pressure vapourtemperature of at least 900 DEG F. whereby a distillate and a residuum fraction are obtained, the residuum fraction is deasphalted with liquid propane, the deasphalted oil and the vacuum distillate are combined, and the mixture is subjected to catalytic cracking. The cracking may be effected using a synthetic clay or aluminasilica type catalyst, arranged in fixed or fluidized beds, at a temperature in the range of 850 DEG to 1150 DEG F. The invention enables a good yield of high-quality gasoline to be obtained from the cracked products, with low catalyst degradation. In an example, a blend of crude oils from various regions in the U.S.A. was distilled with steam until an 18.3 per cent residuum was produced. The residuum was then distilled under vacuum in a centrifugal molecular still at a temperature equivalent to an atmospheric-pressure vapour-temperature of about 1150 DEG F. until a second residuum amounting to 5.8 per cent of the feedstock was obtained. This second residuum was treated with four parts of liquid propane at 120 DEG F. The deasphalted oil was mixed with the vacuum-distillate. The mixture gave a predicted catalytic yield of C5-430 DEG F. naphtha of 55 volume per cent.