Patent GB-573484-A (GB)
Title: Process for the isomerization of paraffinic hydrocarbons
IPC: C10G65/08
Filed: 1943-06-16
Abstract: A paraffinic hydrocarbon fraction containing unsaturateds comprising aromatic hydrocarbons is subjected to non-destructive catalytic hydrogenation using hydrogen in excess of that required p  to hydrogenate the unsaturateds, and the product, including the excess hydrogen, is subjected to isomerization in presence of a metal halide catalyst.  Feedstocks containing normally liquid paraffins with olefins and aromatics, such as gasolines, and having various boiling ranges between, for example, 27 DEG  and above 232 DEG  C., may be used.  Sulphur compounds may be removed by a preliminary treatment, for example with alkali.  Usually the hydrogenation products will require cooling to the isomerization temperature.  The amount of hydrogen is generally 0.5-50 mol per cent of the feed.  The preferred catalyst is reduced nickel or copper and nickel which is used at 93 DEG -260 DEG  C. or more and 1-135 atm. or more.  Other catalysts include cobalt, iron, chromium, molybdenum oxide, and nickel thiomolybdate.  The feed may be in liquid, vapour or mixed phase and one or more reaction zones may be used.  The products, after temperature and pressure regulation if necessary, pass to an isomerizer containing the metal halide, e.g. chloride of Al, Zr, Zn, Sb, Fe or mixtures thereof, which may be supported on alumina, carbon, kieselguhr, fuller's earth, firebrick or other refractory. Metal bromides or iodides are sometimes employed.  Temperatures are generally below 315 DEG  and, with aluminium chloride, usually below 205 DEG  C.  Pressures are from 1 to 135 atm. or more. 0.5-50 mol per cent of hydrogen chloride may be introduced.  The catalyst may be carried over from one tower to another, which may contain packing material, by a transfer medium such as the feedstock or recycled hydrogen.  The isomerization products, after separation of sludge if necessary, pass to a fractionator where isoparaffins are withdrawn as a side stream, hydrogen is removed as overhead and may be recycled to the hydrogenation and/or isomerizing zones, while a solution of catalyst leaves as bottoms and may be recycled.  Hydrogen chloride may be separated from the hydrogen as by fractionation under pressure and recycled to the isomerizer.  In examples: (1) a straight run naphtha fraction boiling at 43 DEG -121 DEG  C. and containing 7 1/2 per cent aromatics and some olefins, after hydrogenation at 167 DEG C. using a nickel-kieselguhr catalyst and 3.5 mol per cent of hydrogen, is isomerized with aluminium chloride and 15 per cent by weight of hydrogen chloride at 27 DEG  C. and 68 atm., the partial pressure of the hydrogen being about 51 atm.; (2) a straight run gasoline fraction boiling at 60 DEG -71 DEG  C. and containing 1.6 per cent aromatics is hydrogenated at about 166 DEG  C. using excess hydrogen and reduced nickel, and isomerization effected in a two-tower operation at about 34 atm. with 10 mol per cent each of hydrogen chloride and excess hydrogen, a temperature of 100 DEG  C. in the catalyst pick-up tower, and 78 DEG  or 93 DEG  C. in the second packed reaction tower. Specification 537,705 is referred to. The Specification as open to inspection under Sect. 91 comprises the treatment of hydrocarbon fractions containing paraffins and unsaturateds generally, for example butanes containing olefins but no aromatics.  This subject-matter does not appear in the Specification as accepted.