Patent GB-819232-A (GB)
Title: Alkylation process
IPC: C07C2/60
Filed: 1957-06-04
Abstract: <PICT:0819232/IV (b)/1> Isobutane is alkylated with propene, butene-2 or isobutene in the presence of a catalyst comprising a solution of aluminium chloride in an equimolar complex of aluminium chloride and an ether containing no more than 4 carbon atoms and 1 to 50 per cent by weight of the catalyst of a mononuclear aromatic hydrocarbon, and an alkylate boiling in the gasoline boiling range is separated from the alkylation reaction product.  During the process, some red oil, aluminium chloride-hydrocarbon complex is formed which is deleterious and is removed by withdrawing a portion of the total catalyst and washing it with fresh or recycled liquid isobutane; the catalyst is dissolved preferentially leaving the red oil which is discarded.  The catalyst is separated from the alkylation product by cooling to 30 DEG  to - 10 DEG F. or even lower when the catalyst solidifies; the cooling is carried out by evaporating a portion of the alkylate at reduced pressure.  Referring to the drawing, a liquefied mixed butane-butenes stream obtained from the catalytic cracking of gas oils, and containing for example 40 per cent isobutane, 10 per cent n-butane, 20 per cent isobutene, 10-15 per cent butene-1 and 15-20 per cent butene-2, is passed through caustic scrubber 13 to remove mercaptans and H2S, is separated from the caustic solution, dried in drier 22, heated to about 210 DEG  F. and passed through a series of isomerization reactors to isomerize butene-1 to butene-2.  Reactor 27 employs a molten sodium, potassium or lithium catalyst at about 210 DEG  F. and in any case below the critical temperature of isobutane (about 280-285 DEG  F.).  Reaction times of 5 minutes to 10 hours to effect 10-50 per cent conversion of butene-1 to butene-2 are employed. The effluent is separated from molten catalyst, cooled to 30-100 DEG  F. and passed to reactor 38 which employs sodium or other alkali metal and/or their hydrides supported on high surface area charcoal, activated alumina, sodium carbonate or clays such as pumice as catalyst.  The catalyst may contain 1-50 per cent by weight of alkali metal which may be converted to the hydride by treatment with hydrogen.  Temperatures of 100-600 DEG  F. and pressures of 15-1500 p.s.i. are used with sufficient residence time, e.g. 5 minutes to 5 hours, to complete the isomerization. The effluent is scrubbed with water in scrubber 51, separated, dried and passed to alkylation reactor 61.  The catalyst is formed in vessel 53 using about 1.5 mols. of AlCl3 per mol. of ether which is preferably dimethyl ether but may be diethyl or methyl propyl ether.  Some AlCl3 may be present as a slurry to ensure saturation of the equimolar complex.  The catalyst may be formed at 50-150 DEG  F.  The aromatic hydrocarbon is also added to the catalyst in vessel 53.  The greater the number of C1-C6 alkyl substituents the more effective is the hydrocarbon, suitable examples are toluene, xylenes, tri-, penta- and hexa-methylbenzenes, mono-, tri-, and hexa-ethylbenzenes, diisopropylbenzene, dibutylbenzenes and butylxylenes or mixtures such as obtained by solvent extraction of a hydroformate fraction.  A mixture of xylenes for example may be added by line 58.  The hydrocarbon and catalyst pass to the reactor by line 59.  The reaction is carried out stage-wise in a single vessel, e.g. as described in U.S.A.  Specification 2,768,987 under liquid conditions preferably below 150 DEG  F.  An external isobutane/olefine weight ratio of at least 3 : 1 is employed with an internal ratio of 50 : 1 to 1000 : 1 with an olefine space velocity of 1.0-20 volumes/hour/volume of catalyst and a contact time of 1 minute to 1 hour.  Cooling may be provided by removing hydrocarbon vapours by line 68, compressing, cooling and returning to the reactor.  The effluent passes to settler 74 from which the lower catalyst layer is removed and recycled to the reactor by line 89, part being removed by line 76 treated with liquid isobutane to dissolve catalyst, leaving red oil which is discarded, and returned in the liquid isobutane by line 67.  The upper layer from settler 74 containing product, unchanged isobutane and dissolved catalyst is flashed in flash drum 96 where the pressure is reduced from 100-500 p.s.i.g. to 10 p.s.i.a. Vaporized isobutane leaves by line 97.  The cooled liquid removed from the flash drum by line 102 is centrifuged, catalyst being separated as a slurry, heated, e.g. by passing through cooling coils in the alkylation reactor, to melt the catalyst, separated from hydrocarbons, which are returned to the flash drum by line 113, and returned to the catalyst preparation vessel by line 112.  The liquid leaving the centrifuge is water washed and passed with cooled isobutane from line 97 to fractionation to obtain isobutane which is used to treat catalyst in line 76, alkylate product and aromatic hydrocarbon which may have been further alkylated and which is returned to the system together with catalyst by line 112.