GB547214A - Improvements in or relating to the alkylation of hydrocarbons - Google Patents

Abstract

547,214. Alkylation of hydrocarbons. STEVENS, A. H. (Texaco Development Corporation). May 7, 1940, No. 8231. [A Specification was laid open to inspection under Sect. 91 of the Acts, Nov. 12, 1940]. [Class 2 (iii)] Isoparaffin hydrocarbons are alkylated with C 3 and C 4 olefins by subjecting a C 4 olefin containing fraction and a low boiling isoparaffin to contact with a liquid alkylation catalyst in a reaction zone under a pressure just sufficient to maintain the C 4 hydrocarbons in the liquid state but insufficient to liquefy the C 3 hydrocarbons. At the same time C 3 hydrocarbons which have been either separated off from the above C 4 fraction, or supplied from a separate source are contacted with a liquid alkylation catalyst in a separate absorption zone, and the liquid product supplied to the above alkylation reaction zone. The isoparaffin is thus alkylated with C 3 and C 4 hydrocarbons using a pressure not greater than that necessary to maintain C 4 hydrocarbons in the liquid state. Saturated C 3 hydrocarbons which are not absorbed in the C 3 absorption zone are rejected. In a preferred form of the invention the process is operated as a continuous multistage process, and catalyst discharged from the reaction zone is passed to the separate C 3 absorption zone, each alkylation stage having its own individual absorption stage. In an example an unstabilized cracked naphtha is passed from pipe 1 to stabilizer 2, and a distillate comprising C 4 , C 3 and lighter hydrocarbons is passed to a fractionator 4 when the C 3 fraction is separated from the C 4 . The C 4 fraction is passed to reactor 6 where it is contacted with isobutane in the presence of concentrated sulphuric acid. The reaction mixture from 6 passes to settler 8 where the used acid separates. At least a substantial portion thereof is mixed in a mixing coil 10 with C 3 and lighter hydrocarbons from pipe 11. The product from mixing coil 10 passes upwards through absorber 14. Fresh sulphuric acid is added to the absorber through pipe 15. Unabsorbed C 3 and lighter hydrocarbons such as propane are discharged through pipe 16. The acid containing the absorbed olefins is passed direct to the reaction vessel 6. The apparatus described has three succeeding stages which function in the same way as the stage just described.