A study on thiophene removals from model oils with different molecular compositions using an inexpensive N-methylpyrrolidone-FeCl3 ionic liquid

Extraction desulfurization technology (EDS) has been widely concerned because of its mild process conditions and low loss of octane number. At present, most of researches on EDS reported in literature mainly adopt single chain alkane as model oil. However, the chemical composition of fluid catalytic crack (FCC) gasoline is quite different from that of single chain alkane. Therefore, in this paper, the removal of thiophene from model oils containing different molecular compositions, such as n-octane, cyclohexane, 1-octene, cyclohexene and toluene, was systematically studied, using NMP + nFeCl3 (n = 0, 5 wt%, 10 wt%, 20 wt%) as extractants. The effects of different molecular compositions on desulfurization rate and the selectivity of extractants were systematically investigated, and their interaction mechanisms were discussed. The experimental results showed that the effects of different molecular compositions on desulfurization rate and selectivity were quite different, with the order of toluene > cyclohexene >1-octene > cyclohexane > n-octane. The higher the π electron cloud densities of the investigated molecular compositions or the more similar their chemical structures to extractants, the lower the desulfurization rates and selectivities. Moreover, the CH⋯π interaction between the investigated molecular composition and the extractant had a greater influence on desulfurization rate and selectivity than ring structure. The desulfurization results of simulated FCC gasoline showed that the selectivity and desulfurization rate of simulated gasoline containing olefins and aromatics were far lower than those of n-octane reported in the literature. The desulfurization results of real gasoline showed that the desulfurization rate and selectivity of real gasoline were also significantly lower than those of n-octane model oil.