Patent GB-573761-A (GB)
Title: Improved process for the isomerization of normal paraffin hydrocarbons
IPC: C07C5/27
Filed: 1942-11-24
Abstract: <PICT:0573761/IV/1> Normal paraffins of at least four carbon atoms are isomerized by contacting in the vapour phase under isomerizing conditions with a catalyst consisting of aluminium halide tenaciously held by a porous carrier, while introducing with the paraffin, aluminium halide vapour sufficient only to replace loss thereof from the carrier.  "Tenaciously held" aluminium halide is defined as that obtained by impregnating the carrier such as a bauxite, acid-treated clay, alumina or silica at a temperature not less than the isomerization temperature, for example as described in Specification 573,109.  Aluminium chloride may be introduced into the catalyst mass by feeding the paraffins, wholly or in part, continuously or intermittently, alone or admixed with promoters such as hydrogen chloride, chlorine or hydrogen, through an aluminium chloride pick-up chamber.  Alternatively the promoter alone may be used as carrier for the aluminium chloride.  By control of the temperatures, and rates and duration of flow, only that amount of halide is vaporized which is necessary to maintain the activity of the catalyst and which can be completely sorbed. This is generally about .005 to .1, preferably .01 to .05 per cent by weight based on the feed.  Single paraffins or mixtures such as field butane or casinghead gasoline, in particular butane or pentane may be treated.  Temperatures are between about 150-400 DEG  F., for butane generally about 250-350 and for pentane about 175-250 DEG  F., with pressures up to 350 lbs./sq. in.  About 0.2-3 volumes of liquid feed/vol. of catalyst/hr. are generally passed. The feed may be treated to remove water and/or olefines, for example with concentrated sulphuric, chlorsulphonic or fluorsulphonic acid.  Multiple reactors in series or parallel may be employed.  The catalyst can be regenerated by burning off carbonaceous deposit and re-impregnation with aluminium chloride as described.  A feed comprising mainly n-butane is fed by lines 2, 4 and scrubbed with sulphuric acid circulating in tower 5.  The spent acid may be withdrawn for production of alcohols or esters or alkylation of isoparaffins.  The washed feed is freed from acid in separator 16 and, after filtering in zone 25 if necessary, is vaporized in heater 29, further heated at 35, and fed to isomerizers 60 and/or 61 either through one or both of the aluminium chloride pick-up drums 41, 37, through the heater or cooler 45, or partly through each.  Hydrogen chloride or chlorine and/or hydrogen enters by line 77 and is fed to the isomerizers either through line 80 and heater 35 or through line 82 and the pick-up drums and/or heater or cooler 45.  The vapours pass through the catalyst bed of aluminium chloride on "Porocel" (Registered Trade Mark) and by line 66 via a cooler, condenser, and heater to stripper 74 where promoter is separated and may be recycled by line 79.  The stripped product is fed by line 83 via a cooler, caustic soda scrubber, and separator, through heater 98 to still 99 where isobutane is separated as overhead from n-butane which may be recycled by line 101.  In an example, the isomerizer is charged with 15 lbs. aluminium chloride covered with 11 lbs. "Porocel" pre-heated to 1000 DEG  F. for 24 hrs. and n-butane passed upwardly through it for 24 hrs. at 250-325 DEG  F. when 6 per cent by weight of hydrogen chloride is admixed with the butane feed and the temperature raised slowly to 350 DEG  F.  After 200 hrs. the feed is passed to the isomerizer via an aluminium chloride pickup chamber at 230-250 DEG F. whereby an average of about .01 per cent is taken up by the feed based on the weight of liquid butane fed.  The Specification as open to inspection under Sect. 91 comprises also the use of catalysts containing aluminium halide in excess of that which is "tenaciously held."  This subjectmatter does not appear in the Specification as accepted.