GB873449A - Improvements in or relating to the isomerisation of hydrocarbons - Google Patents

Abstract

The isomerisation of C5-C7 normal paraffins containing less than 1 p.p.m. of sulphur possibly with concurrent demethylation, is effected at 340-400 DEG C. and 8-70 atmospheres in the presence of hydrogen in a mol ratio to hydrocarbon of 0.5-4.5 and a catalyst comprising an acidic, mixed refractory oxides support together with a hydrogenation catalyst containing an iron-group metal, oxide or salt. The support is preferably silica-alumina though others containing zirconia, titania, boria, chromia and beryllia are referred to. The iron-group metal if present as an oxide may be mixed with a Group VIa metal oxide or may be present as a borate, phosphate, tungstate, molybdate, chromate, vanadate, or manganate. Also present may be palladium, platinum or rhodium, a phosphate of aluminium, magnesium, calcium, zirconium, beryllium or strontium or lithium oxide. The catalyst is activated by reduction and oxidation followed by further reduction, the latter preferably in the presence of water vapour. Reactivation of the catalysts is effected by alternate oxidation or reduction steps, the latter in the presence of water vapour. Water vapour is also preferably present during the isomerisation process, e.g. at a partial pressure of 10-50 mm. Hg. The hydrogen to hydrocarbon mol ratio may be low when starting up, e.g. 0.25-0.5 and gradually increased. A LHSV of 0.1-2 may be used. The preferred feed is a light naphtha or natural gasoline of boiling range 40-95 DEG C. from which isoparaffins have been removed.ALSO:Catalysts for the isomerisation or isocracking of hydrocarbons comprise an iron-group metal, oxide or salt hydrogenation catalyst on an acidic, mixed refractory oxides, active cracking support. The support may be silica-alumina, e.g. containing 13-25% of alumina, silica - zirconia, silica - titania, silica - boria, alumina-zirconia, alumina-beryllia, alumina-boria, silica-chromia, boria-titania, silica-alumina-zirconia or silica-alumina-beryllia. The hydrogenation component may comprise iron, cobalt or nickel, or an oxide, borate or phosphate thereof, together with an oxide of a Group VIa metal, tungsten, molybdenum or chromic oxide, or may be a salt including a Group VIa or other metal such as the salts of tungsten, molybdenum, chromium, vanadium or manganese oxyacids. There may be 0.5-15% of promoter but preferably 3-5% by wt. of nickel. Also present may be 0.01-0.1% of palladium, platinum or rhodium. Nickel and nickel salts may also be promoted with aluminium, magnesium, calcium, zirconium, beryllium or strontium phosphate. With 0.5-8% of nickel, 1-15% of phosphate is added. Lithium oxide may be present in amounts of 0.05-0.5%. The catalyst is activated by heating in hydrogen at 482-538 DEG C. and about 25 atmospheres until the salt used for impregnation decomposes (if not previously calcined) and the metal reaches the lowest valency state. The catalyst is cooled and purged with nitrogen and contacted with air at 370-540 DEG C. The catalyst is again treated with hydrogen and is also preferably water-equilibrated by using humidified hydrogen, preferably at 427-524 DEG C. with hydrogen containing water vapour at a partial pressure of 5-100 mm. Hg for 5-50 hours and preferably in two stages, the first at 496-524 DEG C. and the second 24-136 DEG C. lower but above the process temperature. Regeneration of the catalyst is effected by a plurality of oxidation-reduction steps. Oxidation is effected at 400-538 DEG C. with a gas containing 1-5% oxygen and water vapour at a partial pressure of 1-5 mm. Hg. Reduction may be effected in a single step at 400-538 DEG C. but preferably in two steps, the first at 510-538 DEG C. for 15-25 hours with less than 5 mm. Hg. water vapour partial pressure, the second at 510-524 DEG C. for 10-25 hours with 20-50 mm. Hg. water vapour. Isocracking of paraffinic hydrocarbons of 5-7 carbon atoms to effect isomerisation and principally demethylation is effected in the presence of the above catalysts at 340-400 DEG C. and 8-70 atmospheres and a hydrogen to hydrocarbon mol. ratio of 0.5-4.5. The feed should have a sulphur content of less than 1 p.p.m. and preferred conditions are 360-390 DEG C., 20-35 atmospheres, L.H.S.U. of 0.5-1.2 and hydrogen to hydrocarbon mol. ratio of 2-4.