Alkylation of isobutane with 1-butene on a solid acid catalyst in supercritical reaction media

Alkylation of isobutane with n-butenes to form highly branched isoparaffins is an important process in gasoline manufacture. This reaction is currentl y catalyzed using either liquid hydrofluoric acid or sulfuric acid. Althoug h these liquid acids rapidly catalyze the alkylation reaction, there are a number of drawbacks associated with their use. Solid acids have been studie d extensively as possible catalysts for alkylation. However, with solid aci d catalysts, the catalyst deactivates rapidly with time on stream. It is be en hypothesized and shown that when the reaction is carried in supercritica l media, the solid acid catalyst deactivation slows down considerably; howe ver, high temperatures are needed to bring the reaction mixture to supercri tical conditions, which results in the formation of undesired products. In this study, the effects of using different operation conditions for alkylat ion on a USY zeolite were investigated. It was observed that the deactivati on rate was slower in supercritical-phase alkylation. Carbon dioxide was us ed as a diluent to lower the critical temperature of the reaction mixture i n the ratio 27/9/1 for carbon dioxide/isobutene/1-butene. The use of diluen t favored both alkylate selectivity and coke precursor removal.