Effect of CuCl additive on catalytic performance of Et3NHCl/AlCl3 ionic liquid in C4 alkylation

In order to solve the highly corrosive and environmentally detrimental problem caused by the use of sulfuric acid and hydrofluoric acid as catalysts in alkylation of isobutane and butene, the environmentally benign acidic ionic liquid with CuCl additive was investigated as the catalyst for alkylation of isobutane and butene. The results showed that the modified ionic liquid was an excellent catalyst for the reaction, the yield of alkytate reached 178 % to the butene volume, the total C-8 content in product alkytate was up to 85 % and the RON of product alkylate was 94.8. The ratio of trimethylpentanes (TMP) to dimethylhexanes (DMH) in the product alkylate, which is considered as an important criterion for examining the alkylate quality (higher TMP/DMH ratio implies higher RON), increased sharply from 1.1 to 6.5 with the CuCl additive. The large change in catalytic activity of the modified ionic liquid was due to the formation of AICl(4)CUCI(-) species, which acted as a good acceptor for carbonium ions so as to hold back the formation of longer carbon chains.