Alkylate: Isobutane Joined with Cracked-Gasoline Olefins over 98 % Sulphuric Acid at 10 °C (McAllister & Ross, Shell, US 2,344,469)

Alkylation joins isobutane to the olefins of a cracked gasoline over strong sulphuric acid, at about 10 °C, giving a branched, saturated fuel of high octane. Shell's patent adds a first step: washing the olefin feed with formic acid makes the sulphuric acid last longer. Result (Ex. I): 130 % by weight of alkylate on the cracked gasoline used, about 83 % boiling 23-150 °C, octane 82.5, raised to 94.5 by 1 cc of tetraethyl lead per gallon. The acid made 11.2 volumes of alkylate per volume, against 8.9 without the formic wash. Variable: formic wash or not. Source: McAllister & Ross, US 2,344,469 (1944). Not given: how the reactor is cooled, how acid and alkylate are parted afterwards, where the isobutane comes from. Danger: 98 % sulphuric acid and 90 % formic acid burn skin and eyes. Picture drawn by Youblob.