Patent GB-576375-A (GB)
Title: Process for the isomerisation of saturated hydrocarbons
IPC: C07C5/27
Filed: 1944-04-06
Abstract: <PICT:0576375/IV/1> Saturated hydrocarbons are isomerized by means of metal halide and hydrogen halide and the reaction mixture fractionated to separate a light fraction containing isomerizate, and hydrogen halide, but substantially free from metal halide from a heavier fraction comprising substantially all of the metal halide and higher boiling hydrocarbons, said light fraction then being subjected to an independently controlled fractionation in a second fractionation zone to separate the hydrogen halide substantially completely from the hydrocarbons, the former being supplied to the reaction zone.  The isomerization may be effected in the liquid, vapour or mixed phase.  Pressure may be higher in the second fractionating zone and the hydrogen halide returned under this pressure to the isomerizer.  Normal butane is fed by line 1 to heater 5 and aluminium chloride supply tower 6 at about 10-120 DEG  C. and a pressure to liquefy the butane.  If it contains isobutane, this is separated in fractionator 38 and normal butane fed to the isomerizer as described below.  The butane containing aluminium chloride passes with hydrogen chloride to isomerizer 10 filled with refractory packing and maintained at about 10-180 DEG , preferably 70-125 DEG C., and slightly superatmospheric pressure up to 8.5-38 atm.  The liquid space velocity is about .01 to 5, preferably .1 to .75 vols./vol. of packed space/hr., and the hydrogen chloride concentration 1-40, generally 5-20 mol. per cent.  Reaction products pass to a sludge separator 13 and thence to a fractionator 15.  The sludge may be treated with the recycle streams to recover hydrogen chloride or aluminium chloride.  The overhead passing via condenser 19 to receiver 20 contains nearly all the hydrogen chloride and isobutane and most of the unconverted butane.  Part may be recycled as reflux, light gases may be vented, and the remainder is fed to fractionator 25 which gives an overhead containing hydrogen chloride which is recycled to isomerizer 10 after condensing out hydrocarbons in receiver 30 and recycling to receiver 20.  Bottoms from fractionator 25 may be in part returned by lines 71 and 17 to dissolve hydrogen chloride, the rest passing to fractionator 38 where isobutane is recovered as overhead and normal butane is recycled through lines 41, 49.  Bottoms from fractionator 15 containing higher boiling hydrocarbons, aluminium chloride, and some butane are recycled by line 4 to supply tower 6 or isomerizer 10.  Part is fed to washer 45 where aluminium chloride is removed, and the hydrocarbons are then fractionated in 48 to recover butane which is recycled by line 49, the heavy bottoms being removed.  Part of the stream in line 49 is fed by line 63 to various points in isomerizer 10 to control the temperature therein, while the temperature of the streams entering the supply tower and the isomerizer is also controlled by the recycle.  In an example, the supply tower is at about 71 DEG  C. and the isomerizer 93 DEG  C., pressure being about 27 atm.  The liquid hourly space velocity is 0.3, and the hydrogen chloride concentration 13 mol. per cent.  The first fractionator operates at 20.4 atm. with top and bottom temperatures of 96 DEG  and 110 DEG  C., the second at 30.6 atm. and 43 DEG  and 132 DEG  C.