Process Simulation Of Diesel Desulfurization Systems With Ionic Liquids

With the development of the world's industry and the popularity of automobiles,the consumption of diesel fuel is increasing.However,sulfide in diesel fuel cause serious pollution to the environment,all countries in the world are strictly limiting the sulfide of diesel fuel.However,hydrodesulfurization process is difficult to remove benzothiophene(BT)and dibenzothiophene(DBT)and its derivatives in diesel fuel.Oxidative extraction desulfurization(ODS)process using acidic ionic liquids(IL)as extractant is regarded to be advantages due high desulfurization efficiency,mild conditions,simple operation and easy separation and recovery of extractants,etc.It is among the most important research directions for fuel oil desulfurization that could have a broad prospect in industrial applications.However,the research on the current topic is limited to the laboratory scale.Therefore,this paper uses Aspen Plus as simulation software to design an oxidation extraction desulfurization process for diesel.First,Br(?)nsted acidic ionic liquid N-methyl pyrrolidone hydrogen sulfate([HNMP]HSO4),N-methylpyrrolidone dihydrogen phosphate[HNMP]H2PO4 and organic solvent N,N-dimethylformamide(DMF)were selected as extractants,the model oil of first kind is composed of thiophene as the sulfur component and n-octane as the solvent;the model oil of second kind is composed of dibenzothiophene as the sulfur component and n-octane as the solvent.These two kinds model oils were used as the processing object and the two ionic liquids and organic solvents were used as extractants and the direct extraction method was designed.The interaction parameters between IL and model oil were predicted with the help of COSMO-RS model,the NRTL was selected as the equation of state correlation,finally,the obtained parameters were then inputted into Aspen Plus.Sensitivity analysis was used to examine the effect of various operating conditions on the desulfurization rate of the model oil,and the optimum extraction process for these two different model oils was obtained.Through comparative analysis,it is concluded that ionic liquid[HNMP]H2PO4 as extractant has higher desulfurization efficiency than[HNMP]HSO4 and[HNMP]H2PO4 extractant is used less than DMF,so[HNMP]H2PO4 is performed for the next time simulation.In present study,37 components were selected to define the diesel compositions.[HNMP]H2PO4 and DMF were used as extractants and H2O2 was used as the oxidant for the oxidation extraction process.The best operating conditions were:ionic liquid extractant to oil ratio(S/F)is 1,the ratio of DMF to oil is 1.2;the theoretical plate number of the column is 15,the extraction temperature is 25 ?;the flash pressure of[HNMP]H2PO4 is 1 bar,the temperature is 138 ?;the first flash pressure of DMF is 1 bar and temperature is 187 0C,secondary flash pressure 0.8 bar and temperature is 198 0C.Under this condition,the final desulfurization rate of the product was 96.28%,and the mass yield was 87.37%.The sulfur content was reduced from 224.12 ppm to 8.94 ppm,which reach the national V diesel standard,demonstrating the feasibility of this process for real diesel desulfurization.