Patent GB-574678-A (GB)
Title: Improvements in or relating to the manufacture of 2,3-dimethyl butane and motor fuels of high anti-knock value
IPC: C10L1/06
Filed: 1943-02-16
Abstract: Isobutane is alkylated with ethylene by continuously introducing them in a molar ratio of at least 3 : 1 into a reaction zone wherein an aluminium chloride catalyst is maintained in a volume ratio of total catalyst to hydrocarbon of at least 0.2 : 1, hydrogen chloride being added in an amount not exceeding 0.1 per cent by weight of the hydrocarbon charge, the temperature being maintained at 105 DEG -140 DEG  F., preferably 110 DEG -120 DEG  F., and pressure sufficient to liquefy the isobutane, for a contact time of less than 20 mins., the product being continuously withdrawn and an alkylate recovered consisting of about 70 per cent or more by volume of 2,3-dimethyl butane.  Preferably a preformed aluminium chloride - hydrocarbon complex liquid with added dispersed aluminium chloride is used as catalyst with a volume ratio of total catalyst to hydrocarbon charge of at least 0.5 : 1. Additional aluminium chloride is added during operation.  The ethylene used may contain propylene, generally not more than 20 per cent by weight based on the former.  The alkylate or the dimethyl butane may be blended with other motor fuel fractions, for example a C4 alkylate fraction may be blended with 10-30 per cent thereof.  A cracked naphtha may be stabilized and fractionated to separate a C2 and lighter fraction used for the ethylene alkylation, and a C4 olefinic fraction for C4 alkylation.  The gases from the stabilization of the C2 and C4 alkylates may be fractionated to separate an isobutane and a normal butane fraction, the latter is isomerized, and the products fractionated in the same fractionator, the isobutane fraction being used in the alkylation stages.  Solid aluminium chloride may be used in the form of stationary catalytic beds through which the hydrocarbons are passed and which are continuously flooded with recycled alkylate to maintain the activity. Liquid complexes resulting from usual alkylation or isomerization processes or made by heating aluminium chloride with paraffins, olefins or alkyl halides, e.g. kerosene, naphtha or gas oil and, especially, tertiary butyl chloride are preferred, additional aluminium chloride being suspended therein generally in an amount of 1 part by weight to 4 of complex.  Rotary type reactors of the nature of a centrifugal pump with large clearance between impeller and rotor housing or turbo-mixers may be used, the separated catalyst being recycled after replenishing.  Where a C4 olefinic fraction separated from the initial mixture is used in a combined alkylation process, the C4 alkylation is effected with the usual sulphuric or chlorsulphonic acid, hydrogen fluoride or boron trifluoride-water catalysts, for example as in Specifications 515,367, 527,720, 540,459 and U.S.A. Specifications 2,232,674, 2,267,730 and 2,255,610.  Other olefinic fractions including C5 olefins, and olefin polymers may be used.  Isomerization of n-butane may be effected with aluminium chloride, for example as in Specification 525,554 and U.S.A. Specifications 2,208,362, 2,249,366 and 2,266,011.  Comparative results are given of isobutane-ethylene alkylation with aluminium chloride alone and dispersed in aluminium chloride-kerosene or tertiary butyl chloride complex, molar ratios of hydrocarbons being 4.34 : 1, temperatures 105 DEG -110 DEG  or 110 DEG  F., contact times 18, 11 and 11 mins. respectively, and catalyst hydrocarbon ratios .06, .8 and .8 : 1.  Specifications 533,285 and 546,334 and U.S.A.  Specification 2,174,883 also are referred to.