ABSTRACT
Aliphatic alkylation in petroleum refining is the process of alkylating isobutane with light olefins to produce alkylate, which is a high octane number paraffinic product. Most industrial aliphatic alkylation processes employ either sulfuric acid or hydrofluoric acid as catalyst. Aliphatic and aromatic alkylation are very different processes. Petroleum refining literature often refers just to “alkylation,” implying aliphatic alkylation, despite the potential for confusion with aromatic alkylation. Although the aliphatic alkylation reaction is simply the reverse of cracking, the belief that paraffins are chemically inert delayed the discovery of aliphatic alkylation until about 1935. The major alkylation processes using sulfuric acid as a catalyst are the autorefrigeration process, licensed by ExxonMobil Research and Engineering, and the effluent refrigeration process, licensed by Stratford Engineering Corp. The important question for a refinery is which alkylation process is best for the production of the desired product. The reaction chemistry of aliphatic alkylation is made possible by the extreme stability of the tert-butyl cation.
