GB538307A - An improved manufacture of hydrocarbons by alkylation - Google Patents

Abstract

538,307. Acyclic hydrocarbons. STANDARD OIL DEVELOPMENT CO. Jan. 19, 1940, No. 1180. Convention date, March 4, 1939. [Class 2 (iii)] In an alkylation process for producing hydrocarbons of high octane value from a mixture of hydrocarbons comprising such as contain up to 6 carbon atoms, including at least one saturated hydrocarbon containing a tertiary carbon atom and at least one mono-olefine, wherein the mixture is brought into contact with sulphuric acid under substantially non-alkylating conditions and the acid containing absorbed olefines is passed to the alkylation zone, the gases leaving the absorption zone are fractionated to yield a fraction composed essentially of normal paraffins and one composed essentially of isoparaffins and this latter fraction is conducted to the alkylation zone. The extraction of the olefine and the alkylation are preferably carried. out continuously. The Figure shows, diagrammatically, apparatus suitable for the treatment of a refinery C 4 cut comprising normal butylenes, isobutylene, normal butane and isobutane. The feed stock entering by pipe 2 is passed through a cooler 4 to a dispersion device 7 in an absorber 6 to which fresh sulphuric acid from line 8 or spent sulphuric acid from line 55 is supplied through a cooler 10 and a dispersion device 12. The resulting acid extract is passed through pipes 13, 15 to a dispersion device 17 in an alkylation vessel 16 and effluent containing isobutane passes through pipe 28, and thence, with or without other isobutane-containing liquids or gases supplied through valve 31, passes through pipe 30 to a fractionating tower 32. Normal butane withdrawn from the bottom of this tower may be dehydrogenated or isomerized to isobutane or dehydrogenated and isomerized to isobutylene and the products used in the process. The isobutane-containing mixture from the top of the tower is passed through a cooler 36 to a pipe 37 and thence either by valve 40 and pipe 39 to pipe 13 for admixture with the acid extract supplied to the alkylation vessel 16, or by valve 42, pipe 41, valve 72 and pipes 71 and 23 for preliminary admixture with re-cycle stock. The vessel 16 and the pipes leading thereto are maintained under sufficient pressure to keep the reactants in the liquid phase. Part of the product passes through pipe 18, valve 19 and cooler 21 into pipe 23 for re-cycle to the vessel 16, either by valve 24 and dispersion device 17 or, preferably, directly by valve 26. The remainder of the product passes through valve 45 to settler 46, acid from the bottom of the settler being withdrawn through pipe 47 and returned through valves 54, 43 and 56, pipe 55, and the acid intake pipe 8 to the absorber 6, a portion of the acid being, however, withdrawn from the system continuously or at intervals through valve 58. Alternatively, valve 50 may be opened to divert a portion of the acid to the vessel 16 through pipe 49. Fresh acid may also be supplied to the vessel 16 through pipe 51 and valve 52. The hydrocarbons pass from the top of settler 46 by line 59 and, after treatment with dilute caustic soda (by means not shown) pass through valve 60 to a fractionating tower 61 operated at pressures and temperatures suitable for separating the unreacted hydrocarbons, mainly isobutane, from the alkylation products. The isobutane &c. leaving the top of the tower by pipe 62 is either withdrawn through valve 63 or delivered through valve 65, pipe 64, cooler 69 and valve 70 for re-cycling either through pipe 71 to the re-cycle stock in pipe 23 or through line 39 to the acid extract in pipe 13. Fresh isoparaffin may be supplied through pipe 67 and valve 68. The alkylation product from the bottom of tower 61 is passed to a second fractionating tower 75 maintained under substantially atmospheric pressure, from the top of which the final product of the desired boiling point is withdrawn, the higher boiling fraction from the bottom of the tower being withdrawn or re-cycled to the vessel 16 through a cooler 85.