Study On Preparation And Performance Of Oxygen-containing Acidic Deep Eutectic Solvents For Oxidative Desulfurization

SO_x produced during the combustion of gasoline and diesel is the main air pollutant.Hydrodesulfurization(HDS)is the major desulfurization technology in present.However,the operating conditions of HDS is very harsh,and it is difficult to remove aromatic sulfide by HDS.Oxidative desulfurization(ODS)has gained wide attention due to some advantages such as mild reaction condition and high desulfurization rate.In this paper,three kinds of containing oxygen acid DESs(benzene propionic acid/zinc chloride,choline chloride/trifluoroacetic acid,propionic acid/zinc chloride)were prepared by simple mixing(1)Zinc chloride and phenylpropanoic acid was added to the beaker according to certain molar ratio.The mixture were stirred by glass rod until formed into a green solution at 110?.The green solution is phenylpropanoic acid/zinc chloride deep eutectic solvents.The raw materials and DESs were characterized using electrospray ionization mass spectrometry(ESI-MS),thermogravimetric analysis(TGA),infrared spectrum(FT-IR),viscosity and solubility.The Lewis acidity of DESs,the ratio of oxygen to sulfur,the volume ratio of DESs to oil and the reaction temperature were optimized.The optimal reaction conditions is model oil of 5mL,oxygen and sulfur ratio(O/S)of 6,the ratio of catalyst to oil of 0.25:1,the reaction temperature of 50?.Under the optimal reaction conditions,the desulfurization rate of benzothiophene(BT),dibenzothiophene(DBT)and4,6-dimethyl-dibenzothiophene(4,6-DMDBT)can up to 96.12%,99.23%and98.4%,respectively.And the desulfurization rate of 76.16%can be obtained for the fact kerosene.The desulfurization rate of deep eutectic solvents slightly decreased after 5 cycles.Kinetic analysis shows that the activation energy is 34.754 KJ/mol,and the mechanism of ODS is studied.(2)Trifluoromethanesulfonic acid was dripped into choline chloride according to a certain molar ratio.The mixture were stirred to form a clear solution at room temperature.The clear solution is a choline chloride/trifluoromethanesulfonic acid deep eutectic solvents.Meanwhile,the raw materials and the deep eutectic solvents were characterized using FT-IR,hydrogen spectrum(~1HNMR),conductivity and viscosity.Influence of different desulfurization system,acidiy of deep eutectic solvents,O/S molar ratio,reaction temperature,volume ratio of DESs to oil on desulfurization performance are optimized.The optimal reaction conditions can be obtained such as model oil of 5mL,O/S molar ratio of 6,volume ratio of DESs to oil of0.2:1,the reaction temperature of 40?.The desulfurization rate of DBT and4,6-DMDBT are 98.65%and 96.8%in desulfurization system,respectively.The desulfurization rate is slightly decrease after 5 recycles,and the mechanism of ODS is discussed too.(3)Propionic acid was dripped into zinc chloride.The solution was completely dissolved at 100?.The properties of the raw materials and deep eutectic solvents were characterized by FT-IR,~1HNMR,ESI-MS,viscosity and conductivity.Some parameters such as acidity of deep eutectic solvents,reaction temperature,ratio of oxygen to sulfur,volume ratio of DESs to oil were optimized.The optimal reaction conditions were obtained as follows:the model oil of 5mL,V(DESs)/(oil)of 0.15:1,molar ratio of oxygen to sulfur of 4,and the reaction temperature of 30?.The oxidative desulfurization rate of DBT,4,6-DMDBT,BT and thiophene(TH)were 99.42%,98.8%,68.36%and 45.65%in oxidative desulfurization system,respectively.At the same time,the reaction mechanism and the reuse ability of the deep eutectic solvents were carried out.Desulfurization rate of the deep eutectic solvents slightly decreased after 5 recycles,the results show that deep eutectic solvents for sulfur exhibits good stability.