Isobutylene-Free C4 Fraction: Isobutylene Taken Out with 65 % Sulphuric Acid in Two Stages, 100 °F and 60 °F (Packie & Rupp, US 2,424,186)

Isobutylene is readily absorbed by sulphuric acid of 55-75 % strength. Packie and Rupp do it in two stages: warm, part-used acid takes most of it, then cold fresh acid takes the rest, so very little normal butylene is lost. Result (their example): a feed of 35 % isobutylene, 55 % normal butylenes and 10 % butanes by weight leaves as 2.0 % isobutylene, 82.7 % normal butylenes and 15.3 % butanes. 97 % of the isobutylene is taken out and only 2 % of the normal butylenes. Source: Packie & Rupp, US 2,424,186 (1947). Not given: absorber size, how the isobutylene extract is worked up. The input and output are matched by kind: any cracked C4 cut in, a C4 fraction with the isobutylene removed out. Danger: 65 % sulphuric acid burns. Picture drawn by Youblob.