Isobutane Alkylation Catalyzed By Ether Functionalized Ionic Liquids

Alkylation of isobutane with 2-butene is an important process to produce alkylate. Owing to a high octane number(RON) and low vapor pressure as well as free of sulfur, olefins and aromatics, the alkylate is considered to be a very good blending component for gasoline. At present, sulfuric acid and hydrofluoric acid still have been the dominant industrial catalysts. However, the application of these catalysts results in severe causticity, toxicity, and environmental concerns, which restricts the application.Taking advantage of the predominance of good designability and adjustable combination with variable cation and anion, we synthesized several acidic ether functionalized chloroaluminate ionic liquids and studied the properties such as viscosity, density, thermal stability and acid strength. Then 1-methoxyethyl-3-methylimidazolium chlorine aluminium chloride([MOEMIM]Cl/Al Cl3) with appropriate molar ratio(0.75) of ether functionalized ionic liquids to Al Cl3 was synthesized to catalyze the alkylation of isobutane with 2-butene. Under a low I/O molar ratio(10:1) and mild temperature(30 oC), the optimal alkylate with a C8 selectivity of up to 71.2 wt% and research octane number of 94.3 was obtained, which was much better than that with non-ether functionalized chloroaluminate ionic liquids. The catalysts could be reused several times without obvious loss of activity. In the reaction, the ether group played a positive role in being coupled with Al Cl3 to alter the acidity and increasing the isobutane solubility, which was beneficial to the alkylation.We also prepared several ether-modified chloroaluminate ionic liquids, and investigated the catalytic performance of them. When the isobutane with 2-butene was catalyzed by the ether-modified chloroaluminate ionic liquid with a mass fraction of 8%, the optimal alkylate with a C8 selectivity of 63.2 wt% and research octane number of 93.2 was obtained. The optimum reaction conditions of 25 oC, 10 min, 480 m L/h were preferred by the experiments. Compared to the pure three trimethylamine hydrochloride chloroaluminate ionic liquids, the ether-modified catalysts showed excellent catalytic activity and selectivity. And the catalysts were proved to be of good reusability after 20 cycles.