It was proved that the H in (C₂H₅)₃NHCl was proton acidic through the FT-IR and ¹H NMR analysis of (C₂H₅)₃NHCl solution titrated with KOH alcohol solution, during which KCl was formed and after which the signal of H at δ 7.3 in the ¹H NMR spectrum disappeared completely. When the dewatered (C₂H₅)₃NHCl/AlCl₃ ionic liquid was used as a catalyst, the alkylation catalytic mechanism under a super critical conditions was studied using an isotope exchange method in this paper. The results showed that the dewatered ionic liquid could still catalyze the alkylation, and the carbonium mechanism was established through the GC-MS analysis of the reaction liquid product. It was found that the strength of H linked to N was reduced by 80.12% comparing the ¹H NMR spectrum before and after the reaction, so the H^＋ initiating the reaction was the H linked to N in the (C₂H₅)₃NHCl.

Key words: ionic liquid, alkylation, super critical, catalytic mechanism