Regulating sulfur removal efficiency of fuels by Lewis acidity of ionic liquids

It is urgent to develop a new deep desulfurization process of fuels as the environmental pollution increases seriously. In this work, a series of Lewis acidic ionic liquids (ILs) [(C4MPy)-M-3]Cl/nZnCl(2) (n=1, 1.5, 2, 3) were synthesized and used in extraction and catalytic oxidative desulfurization (ECOD) of the fuels. The effects of the Lewis acidity of ILs, the molar ratio of H2O2/sulfur, temperatures, and different substrates including dibenzothiophene (DBT), benzothiophene (BT) and thiophene (TS), on sulfur removal were investigated. The results indicated that [(C4MPy)-M-3]Cl/3ZnCl(2) presented near 100% DBT removal of model oil under conditions of 323 K, H2O2/DBT molar ratio 6:1. Kinetics for the removal of DBT, BT and TS by the [(C4MPy)-M-3]Cl/3ZnCl(2)-H2O2 system at 323 K is first-order with the apparent rate constants of 1.1348, 0.2226 and 0.0609 h(-1), and the calculated apparent activation energies for DBT, BT and TS were 61.13, 60.66, and 68.14 kJ/mol from 298 to 308 K, respectively. After six cycles of the regenerated [(C4MPy)-M-3]Cl/3ZnCl(2), the sulfur removal had a slight decrease. [(C4MPy)-M-3]Cl/3ZnCl(2) showed a good desulfurization performance under optimal conditions.