GB758413A - Improvements in or relating to process for cracking gas oils to gasoline - Google Patents

Abstract

<PICT:0758413/III/1> Heavy hydrocarbon oils such as gas oil are converted into gasoline by mixing the feed oil with a hydrogen-donor diluent comprising a hydrocarbon oil boiling above 500 DEG F. and containing partially hydrogenated condensed-ring aromatic components, subjecting the mixture to thermal cracking, fractionating the cracked products to separate gasoline and a heavy fraction boiling above 500 DEG F., and submitting the gasoline to catalytic reforming to increase its octane rating and to produce hydrogen this hydrogen is advantageously used to partially hydrogenate the polynuclear aromatic hydrocarbons in the heavy fraction; and the hydrogenated product is then employed as diluent for fresh feed oil. In the Figure, gas oil (B.R. 650 DEG -100 DEG F.), is mixed in line with bottoms from fractionator 23 and with diluent from hydrogenator 25. The volume ratio of diluent to feed is preferably 0.1 to 1.0. The mixture is heated in coil 21 and then cracked in drum 22 at a temperature of 850 DEG -950 DEG F. and at a pressure of 300-2000 psig., the space velocity being 2 to 5 v/v/hr. The cracked products are passed to fractionator 23, from which gas is withdrawn via line 7 while a C4-C5 light fraction is taken off through line 8. Light naphtha (C5-200 DEG F.), is removed from the fractionator by line 27, and gasoline is taken off through line 9. Heating oil (430 DEG -650 DEG ) is withdrawn through line 26; and the diluent cut (650 DEG -950 DEG F.) is taken off through line 10. Part of the bottoms from the fractionator is purged via line 18, and the remainder is sent through line 3 to be mixed with the feed. The gasoline, which may be desulphurized if necessary, is reformed in unit 24 which contains a platinum or molybdena catalyst at a temperature of 750 DEG -1150 DEG F., the pressure being 50 to 1000 psig. Virgin naphtha can be introduced via line 19 to control the hydrogen production in unit 24. The reformed gasoline is removed by line 12 and is blended with the C5-200 DEG F. naphtha from the fractionator. The hydrogen produced in unit 24 is passed via line 13 to hydrogenator 25. Part of the diluent cut from the fractionator may be purged via line 16, and replaced by make-up tar introduced through line 17. The diluent is then introduced into the hydrogenator, which contains molybdenum, nickel or tungsten sulphide as catalyst. The hydrogenated diluent is passed through line 4 to be mixed with the feed. If necessary, the feed may be deasphaltized before it is mixed with diluent.