Triflic acid catalyzed continuous alkylation of isobutane and butene with ionic liquids as a promoter

摘要

Processes for the alkylation of isobutane with C_3-C_5 olefin to produce the highestquality gasoline are of considerable industrial importance, which form a highlybranched C_8 paraffins mixture with high research octane number (RON) and free ofsulphur and aromatics. However, the industrially used catalysts (sulfuric acid orhydrogen fluoride) for alkylation are “non-green” because of some drawbacks from anenvironmental as well as toxicological point of view.An improved process for the continuous alkylation of isobutane and butene in thepresence of the acidic ionic liquid catalysts which could be effectively tunedphysical-chemical properties of the catalytic systems containing the acidity, solubility,density, viscosity, interfacial properties and so on were reported in this study. In thebatch reaction, the acidic ionic liquids catalysts have been prepared from thequaternary ammonium-based ionic liquids with varied anion (such as BF_4~-, PF_6~- SbF_6~-or NTf_2~-) and triflic acid. In addition, several additives, including metal triflates,trifluoroethanol, PPh3 and so on, were used further to improve the catalyticperformances. High-quality alkylate with up to 90% C_8 selectivity and 98 RON valuewere achieved with the optimized catalyst and operation condition. In the continuousreaction, ICP-Mass and ultraviolet-fluorescence analyzer were used to study thealkylate quality. UV-vis spectroscopy and ~(13)C-NMR were used to determined theacidic scale of catalytic system. In addition, refractive indexes also were used to