Desulfurization Of Gasoline Using Ionic Liquids

Owing to the ineffectiveness of hydrodesulfurization to abolish some aromatic sulfur compounds, it is facing challenges in producing the sulfur free clean fuel oils. Oxidative (ODS) and extractive desulfurization (EDS) using ionic liquids (ILs), as substitutes or supplementary processes, has been intensively studied currently. In this study, we synthesized Br(?)nsted acidic ILs of n-methyl pyrrolidonium and n-methylimidazolium cation based. These ILs are n-methyl pyrrolidone hydrogen sulphate, n-methyl pyrrolidone dihydrogen phosphate, 1-butyl-3-methylimidazolium sulphate and 1-butyl-3-methylimidazolium dihydrogen phosphate, and investigated their desulfurization efficiency by following three combinations,1) ODS of real fluidized catalytic cracking gasoline using these ILs as extractant and catalyst and H2O2 as oxidant.2) ODS of real FCC gasoline by ILs coupled with solvent extraction by organic solvents (ethylene glycol, furfural and furfural alcohol) with involving a variations of main factors such as equilibrium time, reaction temperature, regeneration and recycling of ILs, multiple-step of desulfurization and solvent/oil mass ratio.3) EDS efficiency of mixtures of these ILs with n-dimethyl formamide (DMF) as composite solvent for model and real gasoline, involving a diversity of factors such as extraction temperature, extraction time, recycling of solvent, multiple-step desulfurization and solvent/oil mass ratio.The major results and observations of this study as follows,1) ODS efficiencies follow this order [HNMP]HSO4> [HNMP]H2PO4> [BMIM]HSO4> [BMIM]H2PO4 Typically, the sulfur removal efficiency is about 25% after one-step ODS (at 60℃,4 h, IL/oil(w)= 1, O/S(mol)= 16) while it is about 60% after six-step of ODS, e.g., the S-content can be decreased from 260 μg/mL to 194 μg/mL after one-step ODS by [HNMP]HSO4 and be decreased further to 111 μg/mL after six-step ODS, i.e 57% efficiency.2) S-contents, however, can be expressively reduced to 16.8 μmL with a total S-removal of 95.0% in single-step ODS coupled with EDS using furfural alcohol as extractant (40℃ temperature, 1hour, mass ratio of solvent/oil:1). The work shows that ODS using ionic liquids coupled with EDS using organic solvents could be prospective way to produce clean gasoline.3) EDS efficiency of mixtures of n-dimethyl formamide with a ILs [HNMP]HSO4 and [HNMP]H2PO4 (The mixtures were named as composite solvent A and composite solvent B respectively) are very attractive. Thiophene (Ts) S-contents decreased from 500 μg/mL to 22 μg/mL and 28 μg/mL for A and B respectively. While sulfur removal efficiency for real fluidized catalytic cracking gasoline was obtained 70-75% in five extractive desulfurization steps by these composite solvents. The used solvents can be regenerated by an evaporation tailed by simple distillation process.The high efficiency obtained at mild conditions, is favorable due to less cost and energy are required. This study offers a weighty influence to the production of clean fuel.