Phase Equilibrium Study On Extractive Desulfurization Of Thiophene Compounds In Oil

Exhaust emissions from automobiles have led to various hazards,such as air pollution,crop yield reduction,and building damage,which have gradually become the focus of attention.With the rapid development of science and technology and the enhancement of people ’s awareness of environmental protection,the sulfur content in gasoline and diesel oil is more and more strictly restricted in various countries in the world,which is very necessary to reduce the sulfur content in FCC diesel oil and gasoline.According to statistical data research,the sulfides in catalytic cracking gasoline are mainly thiophene and its derivatives,and the content of thiophene and its derivatives is more than 90%.For diesel oil,more than 80%of sulfur compounds are thiophene,and more than 70%of thiophene compounds are mainly benzothiophene(BT)and dibenzothiophene(DBT).Therefore,for the desulfurization of gasoline and diesel oil,it is mainly for the removal of thiophene sulfides.Extraction desulfurization has milder operating conditions compared to hydrogenation and oxidative desulfurization.It is suitable as a pretreatment for deep desulfurization of oil.In this paper,the liquid-liquid and solid-liquid equilibria in the process of oil extraction desulfurization were studied.The solid-liquid and liquid-liquid equilibrium data of thiophene compounds were determined by relevant experimental devices and methods,and the thermodynamic model was used to correlate the experimental phase equilibrium data,providing basic physical parameters and models for the separation and purification of thiophene sulfides in gasoline and diesel.The main contents of this paper include:Firstly,the solubility of dibenzothiophene in N,N-dimethylformamide,1-Methyl-2-pyrrolidinone,ethanol,acetonitrile,gasoline,diesel oil,2-(2-butoxyethoxy)ethanol,n-propanol,n-octane,diethylene glycol,decahydronaphthalene,sulfolane,dimethyl sulfoxide and acetone solvents was determined by using the laser dynamic device by self-designed and assembled in the temperature range of 282.75-341.15 K.The Apelblat,λh and NRTL model equations were used to simulate the phase equilibrium data measured by the experiment,and the corresponding model parameters were obtained.The result of Akaike Information Criterion(AIC)analysis showed that the Apelblat model was the best model to correlate the solubility of DBT in diethylene glycol,1-Methyl-2-pyrrolidinone,n-octane,sulfolane and decahydronaphthalene,the λh model was the best model to correlate the solubility of DBT in 2-(2-butoxyethoxy)ethanol and diesel oil,and the modified NRTL model was the best model to correlate the solubility of DBT in N,N-dimethylformamide,gasoline,acetone,dimethyl sulfoxide and n-propanol.Furthermore,the thermodynamic functions including dissolution enthalpy,entropy and Gibbs energy were obtained from the solubility data by using the van t Hoff equation.Secondly,the liquid-liquid equilibrium data of n-octane-N,N-dimethylformamide,n-octane-dimethyl sulfoxide,n-octane-sulfolane,n-octane-N-methyl pyrrolidone,n-octane-N,N-dimethylformamide-thiophene,n-octane-dimethyl sulfoxide-thiophene,n-octane-sulfolane-thiophene,n-octane-N-methyl pyrrolidone-thiophene,n-octane-N,N-dimethylformamide-dibenzothiophene,n-octane-dimethyl sulfoxide-dibenzothiophene,n-octane-sulfolane-dibenzothiophene,n-octane-N-methyl pyrrolidone-dibenzothiophene systems were determined by using the static analytical method in the temperature range of 310.15-355.15 K.The NRTL model and UNIQUAC model are used to correlate the experimental data of binary and ternary liquid-liquid equilibrium.The results show that the root mean square deviation(RMSD)is 4.91%and 4.32%respectively,and the interaction parameters of the corresponding models are obtained.The thermodynamic stability of the interaction parameters obtained by correlation model is tested.The results show that the interaction parameters obtained by correlation model can accurately describe the liquid-liquid equilibrium process involved in this experiment.Thirdly,the liquid-liquid equilibrium data of decahydronaphthalene-N,N-dimethylformamide,decahydronaphthalene-dimethyl sulfoxide,decahydronaphthalene-sulfolane,decahydronaphthalene-N,N-dimethylformamide-thiophene,decahydronaphthalene-dimethyl sulfoxide-thiophene,decahydronaphthalene-sulfolane-thiophene,decahydronaphthalene-N,N-dimethylformamide-dibenzothiophene,decahydronaphthalene-dimethyl sulfoxide-dibenzothiophene,decahydronaphthalene-sulfolane-dibenzothiophene systems were determined by using the static analytical method in the temperature range of 310.15-355.15 K.The NRTL model and UNIQUAC model are used to correlate the experimental data of binary and ternary liquid-liquid equilibrium.The results show that the root mean square deviation(RMSD)is 2.51%and 2.93%respectively,and the interaction parameters of the corresponding models are obtained.The thermodynamic stability of the interaction parameters obtained by correlation model is tested.The results show that the interaction parameters obtained by correlation model can accurately describe the liquid-liquid equilibrium process involved in this experiment.