PROCESS FOR INCREASING THE OCTANE NUMBER OF A LIGHT GASOLINE FRACTION

1386004 Cracking hydrocarbons SHELL INTERNATIONALE RESEARCH MAATSCHAPPIJ NV 9 Feb 1972 [11 Feb 1971 4 March 1971] 6061/72 Heading C5E A naphtha consisting mainly (85% or more) of C 5 and C 6 paraffins, low in aromatics (5% or less) and having a ratio (Y) of iso/normal C 6 hydrocarbons of 2 or more is hydrocracked selectively to remove normal paraffins and improve the octane rating. The feed must contain a proportion (X%) of C 6 paraffins of 25% or more, and 65Y must be equal to or more than 2x+80. The feed may be the product of an isomerization step, and may contain sulphur. Iso-pentanes may be removed from it before cracking, and blended with the product after removal of C 4 and lighter. The catalyst may include a porous zeolite, and may be sulphided. Six process schemes are described: in scheme I a feed is distilled to take off iso-pentanes, the topped naphtha is then isomerized and hydrocracked and again distilled to take off butanes and lighter, the distillate from the first distillation is then combined with the bottoms from the second; scheme II is similar, except that the distillate from the first distillation and bottoms from the second are not combined; in scheme III, the feed is distilled to take off isopentanes, isomerized, distilled to take off pentanes, which are returned to the feed, hydrocracked, combined with the distillate from the first distillation, and again distilled to take off butanes and lighter; in scheme V, the feed is isomerized, distilled to take off isopentanes, distilled again to take off normal pentane, which is returned to the feed, hydrocracked, combined with the distillate from the first distillation and distilled a third time, to take off butanes and lighter; schemes IV and VI are similar to schemes III and V, except that the distillate from the first distillation in each case is not combined with the hydrocracked material, but is redistilled by itself to take off butanes and lighter. Catalysts used are: for hydrocracking, (1) Ni on hydrogen erionite, (2) Pt or hydrogen-erionite, (3) a mixture of catalyst (1) with Ni on hydrogen-zeolite T; (5) Pt on hydrogen-mordenite and (6) Ni on hydrogen-zeolite KSO1, catalyst 2 being used in its reduced form and the other four sulphided; and for isomerizing (4) Pt on hydrogen-mordenite, in the reduced form. Reference is also made to the use of catalysts containing metals of the copper, zinc, chromium and manganese sub-groups for the hydrocracking step.