GB1071467A - Hydrocracking process - Google Patents

Abstract

Hydrocarbon feedstocks having initial boiling-points higher than gasoline, i.e. higher than 400 DEG F., and having 95% boiling ranges from 405-1000 DEG F., for example whole crudes, heavy naphthas, gas oils, kerosenes, refractory catalytically cracked cycle stocks, high boiling virgin and coker gas oils and residual oils, are hydrocracked at 550-1000 DEG F., 200-3000 p.s.i.g. and an L.H.S.V. of 0.25-10 v./v./hr. in the presence of hydrogen, 0.1 to 10 mole per cent H2S (relative to the total gas mixture) and a hydrocracking catalyst containing a platinum group metal, not more than 10% wt. alkali metal oxide, and a crystalline alumino-silicate zeolite having pore openings of 6-15 <\>rA. To obtain the required H2S concentration in the hydrogenating gas mixture when a low S-content feedstock is used, the gas may be separately added to the hydrogen stream in a measured quantity or may be formed in situ within the hydrocracking reactor by reaction of hydrogen with the pre-adjusted S-content of the feed, increased e.g. to 0.03-10% wt. by addition e.g. of CS2; when a feedstock of high S-content is used the required H2S concentration may be achieved by conventional hydrofining or, in recycle processes, by purging the H2 and H2S gas stream from the system. In a preferred embodiment a two-stage hydrocracking treatment is used in conjunction with an initial hydrofining. The hydrocracking catalyst is a natural or synthetic zeolite, baseexchanged with another metal or hydrogen-containing cation, and composited with a platinum group metal, preferably palladium, to give 0.01-5.0% wt. of the catalytic metal in the finished catalyst. Platinum or palladium may be added as a salt or ammonia complex, e.g. platinous ammonia chloride, palladium chloride; generally the platinum group metal is reduced to its elemental form by heating or treatment with H2 at 500-1500 DEG F. If a catalyst of reduced activity is required the zeolite may be embedded in a silica gel or cogel with ammonia, titania or magnesia to give a final composite containing 5-80% wt. zeolite. A fixed, moving or fluidized bed of hydrocracking catalyst may be used. The hydrofining catalyst, when used, may be individual or mixed oxides or sulphides of Group VI and VIII metals composited with an inert metal oxide support consisting of silica or a Group IIA, IIIA or IVB metal oxide; cobalt molybdate on alumina is particularly preferred. The hydrofining preferably involves downward flow of the oil feed over a fixed bed of catalyst. In a two-stage hydrocracking the second stage employs milder conditions. The hydrocracking product may be fractionated to give light and heavy naphtha, light fuel oil, and heavy oil bottoms for recycle.