Isobutane: Normal Butane Isomerised over Aluminium Chloride and Hydrogen Chloride at 150 °C (Ipatieff & Pines, US 2,318,226)

Heated under pressure with aluminium chloride and a little hydrogen chloride, straight-chain normal butane rearranges into branched isobutane, the gas that alkylation needs. About two thirds of the butane comes out as isobutane. Result (Ex. I): after 12 hours at 150 °C the hydrocarbons were 66.5 % isobutane and 31.9 % normal butane. Variable: batch or continuous. A rotated pressure vessel suits small scale; a continuous run through a heated tube and reaction chamber at 160 °C gave about 63 % isobutane. Source: Ipatieff & Pines, US 2,318,226 (1943). Not given: how the butanes were fractionated, vessel size, how it was heated. Danger: hydrogen chloride gas burns eyes and lungs, and the vessel runs at about 30 atmospheres. Picture drawn by Youblob.