GB587615A - Improved process for the isomerization of straight chain paraffinic hydrocarbons - Google Patents

Abstract

Normal paraffins of at least 5 carbon atoms are isomerized by contact in the vapour phase at superatmospheric pressures up to 180 p.s.i. with an aluminium halide catalyst supported on a solid carrier and arranged in solid beds, at a temperature of 400-500 DEG F., in the presence of 2-22 per cent by weight of a halogen-containing promoter and in the absence of hydrogen, the rate of flow of normal paraffin feed being 0.25-2 vols./vol./hr. and the contact time 16-260 secs. In a modification, hydrogen having a partial pressure of 50-600 p.s.i. may be present, the total pressure being up to 1000 p.s.i. Rate of isomerization and selectivity increase with increase of temperature. The preferred catalyst is aluminium chloride or bromide on a carrier such as activated carbon or alumina, acid-treated clays, bauxite and particularly "Porocel" (Registered Trade Mark). Aluminium chloride may be vaporized and carried by a carrier gas into contact with the carrier or mixed therewith in solid form or in presence of a solvent. The "Porocel" may be preheated to 1000-1400 DEG F. for 1-18 hrs. and, after absorbing the chloride vapours, may be heated to 25-100 DEG F. higher than the isomerization temperature in an inert gas to remove all but tenaciously held chloride, generally about 4-12 per cent by weight. The feed may be normal pentane, which may contain small amounts of isopentane, or hexane, heptane or higher paraffins, casinghead gasoline or straight-run naphtha. Olefins and water are removed with concentrated sulphuric acid or fluor- or chlor-sulphonic acids, and sulphur with caustic alkali. A plurality of reactors may be arranged in series or parallel. The catalyst is regenerated by heating to remove aluminium halide, burning at 700-1000 DEG F. with oxygen-containing gas, and re-impregnating. Examples describe the isomerization of pentane with aluminium chloride on "Porocel" at varying reaction conditions. Specifications 498,463, 535,398 and 543,085 are referred to.