Acid-catalyzed isobutane-isobutylene alkylation in liquid carbon dioxide solution

Liquid carbon dioxide was studied as a solvent for the isobutane-isobutylen e alkylation. The acid catalysts in the reaction were anhydrous HF (AHF), p yridinium-poly(hydrogen fluoride) complex (PPHF), concentrated sulfuric aci d and trifluoromethanesulfonic acid (TFSA). The effect of the acid-hydrocar bon volume ratio, temperature and residence time on the alkylate quality we re studied over the temperature range of 50 greater than or equal to T grea ter than or equal to 0 degrees C. Carbon dioxide as a competing weak base d ecreases the acidity of the system which parallels the alkylate quality. In the case of HF and TFSA catalysts, solvent CO2 increased the octane number of the alkylate product (RON 95.6 for HF- and 88.0 for TFSA-catalyzed alky lation with CO2 solvent).