Abstract
Study on alternative methods to hydrodesulfurization is always an interesting area, because of the ineffectiveness for hydrodesulfurization to remove some cyclic sulfur compounds (S-compounds) and the high cost from harsh operation conditions and expensive catalyst, among which oxidative desulfurization (OM using ionic liquid's (ILs) as solvent is intensively studied recently. Here, we synthesize a series of Bronsted Lewis acidic as of N-methylpyrrolidonium zinc chloride ([Hnmp]Cl-x/(ZnCl2)(y), x:y from 2:1 to 1:2) and investigate the ODS of both model diesel fuel composed of n-octane and dibenzothiophene and real FCC feedstock where such ILs are used as extractant and catalyst and 30 wt % H2O2 is used as oxidant, involving the factors Such as IL composition (or x:y), temperature, dose of Oxidant (or molar ratio of O/S), dose of IL (or mass ratio of IL/oil), recycling of IL and multistage desulfurization. IL composition has an important effect on sulfur removal (S-removal) efficiency, and [Hnmp]Cl/ZnCl2 (x:y = 1, the structure nature was characterized with ESI-MS and FT-IR) show the highest desulfurization capability with good recyclability. With [Hnmp]Cl/ZnCl2, the S-content in model diesel fuel can be reduced to <1 ppm from 500 ppm. with 99.9% S-removal at 75 degrees C, IL/oil = 1/3 and O/S = 8 after only one stage, while the sulfur removal for real FCC diesel fuel is less than 38% in one stage and can reach 83% after five stages, which might be ascribed to more-complex S-species in real fluidized catalytic cracking (FCC) diesel fuel as indicated by gas chromatography sulfur chemiluminescence detection (GC-SCD) chromatogram analyses. The sulfur content (S-content) in FCC diesel fuel, however, can be reduced to 5.3 ppm with a total S-removal of 97.6% after five-stage ODS with one more extractive desulfurization with furfural as the extractant. This work shows that such Bronsted-Lewis acidic ILs are potential solvents used in ODS to produce clean fuel oils.