Patent GB-582138-A (GB)
Title: Vapor phase isomerization of hydrocarbons
IPC: B01J27/06
Filed: 1943-06-17
Abstract: A catalyst for isomerizing saturated hydrocarbons, in particular paraffins containing at least four carbon atoms, is made by supersaturating g -alumina containing less than 2 per cent. by weight of water with anhydrous liquid aluminium chloride under pressure. The g -alumina may be prepared by thermal dehydration of a or b -alumina trihydrate or a-alumina monohydrate, preferably such hydrated aluminas as have been precipitated from basic solutions, for example, by seeding or treating with carbon dioxide a sodium aluminate solution. Bauxites free from clay and iron may also be dehydrated.  The water content is preferably reduced to below 1, e.g., 0.5 per cent.  The temperature required may be about 600-850 DEG C., preferably 700-750 DEG C., for bauxite, and about 500-800 DEG C. for activated alumina and similar materials.  The time of dehydration varies with temperature, for example, between 1 and 12 hours. Acid pretreatment of the alumina with hydrochloric, sulphuric or hydrofluoric acid may be employed and a stream of hot air used to remove the water.  A g -alumina which absorbs about 15 per cent. of aluminium chloride when treated with vapour thereof at atmospheric pressure, is supersaturated with more than 15 and up to 40 per cent. by weight of aluminium chloride by impregnation with the liquid under pressure.  The concentration is generally more than 115 per cent. of that at saturation.  The impregnation is preferably effected in one stage at about 200-400 DEG C. for 40 minutes-8 hours.  The isomerization may be effected at pressures and temperatures sufficient to maintain the vapour phase.  In examples: (i) alumina trihydrate precipitated from sodium aluminate is heated to about 250-300 DEG C. until the water content is 6 per cent., and then further dehydrated at about 500 DEG C. till less than 2 per cent. when it is impregnated with liquid aluminium chloride under pressure to a content of 22 per cent., (ii) a bauxite containing alumina in the form of a-alumina monohydrate is dehydrated at 700 DEG C. for 6 hours giving a g -alumina of less than 1 per cent. water content which is supersaturated with about 20 per cent. aluminium chloride. Specification 556,803, [Group IV], is referred to.ALSO:Saturated hydrocarbons, in particular paraffins containing at least 4 carbon atoms, e.g. butane, pentane and hexane, are isomerized in the vapour phase by contacting with a catalyst made by supersaturating g -alumina containing less than 2 per cent by weight of water with anhydrous liquid aluminium chloride under pressure.  The g -alumina may be prepared by thermal dehydration of a - or b -alumina trihydrate or a -alumina monohydrate, preferably such hydrated aluminas as have been precipitated from basic solutions, for example by seeding or treating with carbon dioxide a sodium aluminate solution.  Bauxites free from clay and iron may also be dehydrated. The water content is preferably reduced to below 1, e.g. 0.5 per cent.  The temperature required may be about 600-850 DEG , preferably 700-750 DEG  C., for bauxite, and about 500-800 DEG  C. for activated alumina and similar materials. The time of dehydration varies with temperature, for example between 1 and 12 hrs.  Acid pretreatment of the alumina with hydrochloric, sulphuric or hydrofluoric acid may be employed and a stream of hot air used to remove the water.  A g -alumina which absorbs about 15 per cent of aluminium chloride when treated with vapour thereof at atmospheric pressure, is supersaturated with more than 15 and up to 40 per cent by weight of aluminium chloride by impregnation with the liquid under pressure. The concentration is generally more than 115 per cent of that at saturation.  The impregnation is preferably effected in one stage at about 200-400 DEG  C. for 40 mins. to 8 hrs.  The isomerization may be effected at substantial pressures, and temperatures sufficient to maintain the vapour phase, e.g. at 9-12 atm. and 100-130 DEG  C. for butane.  High space velocities, e.g. 20-100 mols. of butane per litre of catalyst per hr., and high concentrations of promoter, e.g. about 10 per cent of hydrogen chloride, may be used.  The known degradation inhibitors may also be added.  In examples: (1) alumina trihydrate precipitated from sodium aluminate is heated to about 250-300 DEG  C. until the water content is 6 per cent, and then further dehydrated at about 500 DEG  C. till less than 2 per cent when it is impregnated with liquid aluminium chloride under pressure to a content of 22 per cent and used for isomerizing butane at 100 DEG  C. and 11 atm., a space velocity of 6 mols. per litre per hr., using 2 mols. per cent of HCl; (2) a bauxite containing alumina in the form of a -alumina monohydrate is dehydrated at 700 DEG  C. for 6 hrs. giving a g -alumina of less than 1 per cent water content which is supersaturated with about 20 per cent aluminium chloride and used to isomerize butane at 100 DEG  C., 11 atm., space velocity of 12 mols. per litre per hr., and HCl concentration of 3, later increasing to 15 mols. per cent. Specification 556,803 is referred to.