Patent GB-529197-A (GB)
Title: Improvements in or relating to alkylation of hydrocarbons
IPC: C07C2/62
Filed: 1939-05-24
Abstract: 529,197. Alkylation of isoparaffins. TEXACO DEVELOPMENT CORPORATION. May 24, 1939, No. 15416. Convention date, July 29, 1938. [Class 2 (iii)] Low boiling isoparaffins are alkylated with olefins by a process which comprises feeding into the reaction zone isoparaffins, olefins, and liquid acid catalyst at such a rate as to maintain a pre-determined acid to hydrocarbon ratio in the feed, withdrawing the products of reaction, separating the acid from the hydrocarbon and re-cycling the used acid in sufficient amount to maintain a higher ratio of acid to hydrocarbons in the reaction zone than in the fresh feeds. The preferred ratio of acid to hydrocarbons in the reaction zone is 2-5 times that in the fresh feeds. The preferred acid catalyst is sulphuric acid, and a preferred modification of the invention comprises passing the hydrocarbon mixture and strong sulphuric acid catalyst through a plurality of reaction zones, withdrawing hydrocarbon reaction products and acid, separating at least a portion of the acid and hydrocarbon reaction products, and recycling' the used acid to the reaction zones to maintain a higher concentration of acid in the reaction zones than in the fresh feeds. If desired, an accumulation of acid may be caused in the reaction vessels, by separating at least a portion of the acid from the mixture passing through the system and returning the acid to one or more reactors or points in the system. The amount of acid held up may be variably controlled by controlling the rate of re-cycling of the acid to the individual reactors. In the five stage apparatus shown in Fig. (1) for a counter-current flow operation the isoparaffin charge which may be any low boiling isoparaffin such as isobutane, isopentane, isohexane or mixtures thereof is fed through line 5 to the mixer 7 where it is contacted with used acid from a previous settler introduced through line 8. The charge to the mixer 7 may be only isoparaffin, in which case it acts as a stripping medium for the used acid. Additional hydrocarbons may be added through lines 9 and 10. After intimate mixture in mixer 7 the reactants are transferred to settler 14 through line 12. The hydrocarbons collect in the upper part and the acid in the lower part of the settler. A constant amount of acid may be retained in the settler and regulated by the constant level device 17. Any desired proportion of the acid may be re-cycled to the mixer through the line 19 and pump 20. Additional olefine stock may be added through the line 22. The resulting mixture is then transferred to a second mixer 25 through line 24 where the process is repeated and passed to a second settler 28. The branch lines 10, 22, 35, and 50 communicate with an olefin supply line 52 through pump 53. By regulation of the valves in these lines the charge may be split between any or all of the settlers 14, 28, and 42. Fresh acid is introduced through line 67 by pump 68. This is preferably sulphuric acid of 94 per cent. to 96 per cent. concentration. Hydrocarbons are passed from settler 70 to mixer 75 where they are mixed with an alkaline reagent such as dilute caustic soda or soda ash solution, and then passed to settler 81, and the hydrocarbon fraction passed through fractionator 85. The lighter gasoline fractions pass to the secondary fractionator 90. A similar apparatus adapted for a concurrent flow operation also is described.