Patent GB-599906-A (GB)
Title: Improvements relating to the use of liquid alkylation catalysts in the alkylation ofhydrocarbons
IPC: C07C2/62
Filed: 1943-09-22
Abstract: <PICT:0599906/IV/1> A process for the alkylation of isoparaffins with olefins other than ethylene to produce hydrocarbons boiling in the motor fuel range, using concentrated sulphuric acid at -10 DEG  to 30 DEG  C. and sufficient pressure to maintain the liquid phase, and circulating the reaction mixture at a high rate to induce turbulence until the acid concentration is reduced to an extent determined by the quality of the alkylate, comprises charging a reaction zone with fresh acid of high concentration, flowing into said zone a stream of olefin, a substantial excess of isoparaffin, and acid of at least the concentration of that in said zone and at a rate to maintain the acid concentration above the average concentration of the acid in an operational cycle, continuously withdrawing a stream of reaction mixture and conducting at least a portion into a quiescent settlement zone of large capacity wherein the acid is separated, passing said acid to a storage zone of large capacity to accumulate therein a body of acid of average concentration appreciably above that of the acid in the reaction zone, and recycling acid from the storage zone to the reaction zone to serve as "make-up" acid.  Using an initial 98 per cent acid, the first period of the operation will yield an alkylate of above standard quality, i.e. the quality obtained with the use of 90 per cent acid.  In the second period, acid from the storage zone is used and is discarded while still above 90 per cent.  This is used in successive periods until it falls to or below 90 per cent when further use gives a sub-standard alkylate.  The process may be continued until the acid is degraded to 85 or even 82 per cent. Part only of the average total acid supplied in an operational cycle may be charged to the alkylator, and to the balance tank or storage zone. The acid in said tank is rapidly circulated to the reaction zone, and additional make-up acid from an external source may be added at such a rate that the total acid, including that originally charged, will not exceed that used in a normal operation.  As applied to a single-stage continuous unit, concentrated, e.g. 98 per cent acid, isoparaffin, and olefin are fed by lines e, g, h through pump a where they are emulsified and passed to reactor b.  The product separates in settler c, part of the emulsion being recycled by line b1 to maintain an isoparaffin : olefin ratio of 50-150 : 1 or more. Separated acid passes to balance tank d.  In the second period, acid is supplied from tank d through pipe c4 and, after separation in settler c, passes to tank d1.  In a third period, acid from d1 is used, and separated acid passes to d, and so on. In modifications, the plant is charged with acid, the remainder necessary for an operational cycle is charged to the balance tank, and circulation effected as above or part of the total only is charged and fresh acid added during operation.  In multi-stage plants, acid from the settler of one stage passes to the reactor of the next during the initial period, while, in the second period, degraded acid of the first is used as make-up. Degradation of acid in the balance tanks may be prevented by storing in contact with, say, isobutane, which is evaporated to maintain a low temperature.  In examples: (1) a continuous multi-stage plant is operated in periods of 10 days; in the first 98 per cent acid is charged and added as make-up, the concentration falling to 95 per cent while the acid withdrawn to the balance tank is 96.5 per cent; in the second, the latter acid is added as make-up, the concentration falling to 92.5 while 94 per cent acid accumulates in a second balance tank; successive periods result in a final concentration of 82 per cent; (2) balance tanks are added and acid drawn entirely therefrom or part charged to the tanks and part added as make-up.