Melting-type acidic quaternary ammonium ionic liquids as catalysts for alkylation desulfurization of FCC gasoline

The melting-type of caprolactam-tetrabutylammonium bromide acidic quaternary ammonium ionic liquids (ILs) were synthesized as catalysts for the olefin alkylation thiophenic sulfur (OATS) in FCC gasoline. [CPL-TBAB] 2HSO(4) with high acid strength showed the best desulfurization performance. GC-MS analysis suggested that the alkylation products of model oil were mainly mono-alkyl or di-alkyl thiophenic sulfides. The decrease of acid strength made the activity of IL degraded. Re-cation regeneration of cationic ligands with higher price recovered from the used IL was proposed to restore the acid strength by adding new anionic groups, and it showed a similar desulfurization activity as the fresh IL.