GB600011A - Improvements relating to the isomerization of saturated hydrocarbons - Google Patents

Abstract

<PICT:0600011/IV(b)/1> Isomerization of saturated hydrocarbons is effected by passing them in liquid phase through a primary reaction zone containing an isomerization catalyst comprising free Friedel-Crafts metallic halide in the presence of hydrogen halide under such conditions that isomerization occurs and some metallic halide is dissolved in the hydrocarbons, passing the stream of hydrocarbons and dissolved halide to a secondary zone where it is contacted with a body of liquid metal halide-hydrocarbon complex substantially free from uncombined halide under isomerizing conditions, an olefin being provided in this zone sufficient to react with the free halide, and separately removing an isomerized hydrocarbon stream substantially free from dissolved metallic halide, and excess liquid complex. Instead of olefins such as propene or butane being injected into the secondary zone in the isomerization of butane, normal paraffins of from 5-7 carbon atoms may be added which are isomerized and, under the prevailing conditions, cracked to a small extent to form the reactive olefins. Surplus complex discharged from the secondary zone may be used for isomerizing higher hydrocarbons or for purifying hydrocarbons. The temperature may be the same in both zones or lower in the second to favour pentane isomerization when this is added. Normal butane from pipe 1 is preheated to 160-240 DEG F. and fed in the form of dispersed droplets to the base of tower 4 containing a 10-40 ft. column of liquid complex catalyst. 1-10 per cent of hydrogen chloride promoter may be fed by pipe 6. Treated hydrocarbons pass by pipe 7 to a second similar reactor 10, and leave by pipe 11 for fractionation. Pipe 20 leads part of the initial feed to heater 21, and vessel 22 containing aluminium chloride fed from hopper 23, the resulting solution passing continuously by line 24 to reactor 4 to maintain the required free halide. Hydrocarbons leaving by pipe 7 may contain .01-.20 per cent by weight of aluminium chloride. Olefine is fed to the reactor 10 by pipe 31 or 32 in sufficient amount, about .01-1 per cent by weight of the total hydrocarbons, to remove free halide from the catalyst. Surplus complex is withdrawn to vessel 34. The complex catalyst in reactor 4 should have a heat of hydrolysis of about 340-360 cals. per gram while that in reactor 10 should have a figure of not more than 320 and may be as low as 200. Temperatures are about 200 and 220 DEG F. respectively. Preformed complex for starting up may be obtained from aluminium chloride, hydrocarbon such as kerosene, and hydrogen chloride at 200-300 DEG F. Used complex may have additional aluminium chloride incorporated for re-use. Pentane, hexane, heptane, and naphtha fractions may be isomerized similarly. The catalyst is preferably free of undissolved aluminium halide. The hydrocarbons may be in liquid, gas or mixed phase, and such additions as naphthenes, hydrogen, and aromatics may be made to permit of higher reaction temperatures. Spent complex from the second zone may be recycled in small amounts to the first to improve the fluidity.