Extractive desulfurization of dibenzothiophene by a mixed extractant of N,N-dimethylacetamide, N,N-dimethylformamide and tetramethylene sulfone: optimization by Box–Behnken design

In this paper, the performance of extractive desulfurization (EDS) from gasoline was studied using a mixed solvent, which consisted of N,N-dimethylacetamide (DMAC), N,N-dimethylformamide (DMF) and tetramethylenesulfone (TMS). The effects of relevant parameters on EDS including volume ratio of DMAC/DMF/TMS, extraction temperature, extraction time, stirring speed, volume ratio of extractant and gasoline and initial concentration were investigated. The extraction removal of dibenzothiophene (DBT) and the residual sulfur content reached 99.1% and 9.5 ppm, respectively, at an optimal extractive condition of volume ratio of DMAC/DMF/TMS of 3 : 1 : 1 and volume ratio of extractant to gasoline of 1 : 5 at a stirring speed of 100 rpm over 10 min for extraction at 30 °C (ambient temperature) with five extraction stages. The DMAC/DMF/TMS extractant could be reused for several cycles maintaining high sulfur removal before being regenerated through adsorption. The impacts of three individual process variables such as, extraction time, extraction temperature and volume ratio of extractant to gasoline were investigated using Box–Behnken experimental design and their optimum values were found to be 15 min, 37 °C and 0.5, respectively. These results can be referred to for sulfur removal from gasoline in industrial applications.