Preparation Of Ionic Liquids And Applications In Diesel Oil Desulphurization

Ionic liquids extraction is an promising method for desulphurization. It has been concerned widely for the advantages of mild operation conditions, low energy consumption, environmental friendliness and renewable capacity. The ionic liquids [BMim]PF6 (1-butyl-3-methylimidazolium hexafluoroaphate) and [EEim]DEP (N-ethyl-N-ethyl- imidazolium diethyl phosphate) were synthesized and used in model oil and diesel oil extractions in this paper. The effects of different operation conditions were investigated and the results are listed as follows:The ionic liquids [BMim]PF6 and [EEim]DEP were synthesized by one-step and two-step methods. The ionic liquids were characterized by IR and the properties of viscosity versus temperature were studied.Two kinds of ionic liquids were used in the extraction of model oil which was prepared by mixing a certain amount of thiophene(T), benzothiophene(BT) and dibenzothiophene(DBT) with n-nonane. The ionic liquids show same variation regularities in aspects as follows: the desulphurization rates increase with the improvement of ratio between ionic liquids and oil, and the selectivity of sulfur contents rank as follows: DBT>BT>T. In the diesel oil extraction, the optimal desulphurization conditions with [EEim]DEP have been obtained: 40℃,I/O(v)=0.5,desulphurization rate 21.44%, while for the [BMim]PF6 are 90℃,I/O(v)=0.5,desulphurization rate 18.54%. The ionic liquid [EEim]DEP shows better desulphurization performance than [BMim]PF6 both in model oil and diesel oil extractions.In the catalytic oxidative experiments, the characters of three catalysts were compared and the effects of the catalysts rank as follows: C>B>A. Under the same operation conditions, different ionic liquids’desulphurization rates rank in the order [EEim]DEP> [BMim]PF6> [BMim]Br. The desulphurization rate of [EEim]DEP reaches 27.08% at the optimal operation.The continuous extractions of hydrogenation diesel oil with [EEim]DEP were carried out at 70℃, I/O(w)=0.8. The total feed rates are respectively 5.14g/min and 3.0g/min while the fillers are glass beads and Dixon ring. After 5 stages of continuous extractions, the desulphurization rates reach 36.38%(glass beads) and 50.83%(Dixon ring). The field of diesel oil is more than 96% in every stage of extraction.The distributions of sulfur-containing compounds in diesel oil before and after extraction were analyzed by GC3800 gas chromatograph. Contrast to [BMim]PF6, [EEim]DEP shows better selectivity for DBT and its derivatives and [BMim]PF6 performs good removal ability for T and DBT.The desulphurization rate of [EEim]DEP decreases with the increase of water contents in it. The used [EEim]DEP was regenerated by dilution-distillation process.