GB1347773A - Production of high octanerating unleaded gasoline - Google Patents

Abstract

1347773 Cracking and reforming naphtha UNIVERSAL OIL PRODUCTS CO 9 July 1971 [10 July 1970] 32279/71 Heading C5E Unleaded gasoline of high octane number is obtained by (a) catalytically hydro-cracking a feed heavier than gasoline, (b) separating the product into a first saturated vapour and a liquid of gasoline boiling range, (c) reforming this liquid under conditions such that at least 80 mole per cent of naphthenes, but no more than 40 mole per cent of alkanes is converted to aromatics, (d) separating the reformate into an aromatic stream, a saturated liquid stream and a second saturated vapour, (e) cracking this saturated liquid, thermally or catalytically, to obtain a cracked gasoline and an unsaturated vapour, (f) alkylating part or all of this unsaturated vapour with part or all of the saturated vapours from steps (b) and (d), and (g) combining the aromatic stream, the cracked gasoline and the alkylate. As shown, kerosene, atmospheric gas oil and vacuum gas oil in line 1 are hydrocracked at 2 in two stages. In the first stage, the catalyst is of nickel and molybdenum on an amorphous alumina-silica carrier, and serves also to remove nitrogen and sulphur from the feed as ammonia and H 2 S. The product is cooled by heat-exchange before passing to the next stage, where the catalyst is of nickel on faujasite. The product is cooled by heat-exchange and separated into vapour and liquid. The vapour is rich in hydrogen and may be freed of H 2 S and light hydrocarbons and then recycled. The liquid is fractionated, butanes and lighter being taken off by line 7 and heavy naphtha (heptanes to 204‹ C.) by line 3; heavier material is recycled to the second hydrocracking step, pentanes and hexanes may go with the heavy naphtha (3) or may go directly to the pool 13. The naphtha in line 3, and straight-run naphtha from line 4 are reformed at 5 in the presence of hydrogen over a catalyst of platinum, germanium and chlorine on alumina. The reformate is separated into a hydrogen stream, which is recycled, a light hydrocarbon stream (up to butane) in line 6 and a reformed naphtha in line 9. This is extracted countercurrently with sulpholane at 10 to give a paraffinic raffinate in line 11 and an aromatic extract which is separated from the solvent and goes by line 12 to the pool 13. The raffinate 11 and a light naphtha (pentanes and hexanes) are cracked at 14 using a fluid catalyst of faujasite and alumina in a silica matrix, and without liquid recycle. The product is separated into cracked gasoline, which goes by line 16 to the pool 13, and an unsaturated gas in line 15. The saturated gases in lines 6 and 7 are fractionated at 8 to obtain propane (25), iso-butane (22) and normal butane (21). The propane may be used as LPG, dehydrogenated to propene or go to alkylation (24); the normal butane may be isomerized at 23, together with butane recycled from the alkylation, over a catalyst of alumina, aluminium chloride and platinum in a fixed bed, and then go to alkylation; alternatively it may go directly, like the isobutane, to alkylation. The unsaturated gas in line 15 is fractionated at 26 to give propene (26) which may be used to make isopropyl alcohol, isopropyl-benzene, tetramer, or other chemicals, or may go, like the butenes in line 19, to alkylation. The alkylation 24 is over a HF catalyst; unreacted material may be recycled, the alkylate goes by line 17 to the pool 13. The middle distillates 1, straight-run naphtha 4 and light naphtha going to the cracking zone 14 may all be obtained by fractionation of the same crude.