| The rapid development of economy and people's income levels have promoted the continuous growth of the number of vehicles,and the pollution caused by automobile exhausts has become increasingly serious.To this end,countries around the world have introduced increasingly strict environmental regulations,and the use of low-sulfur or even sulfur-free gasoline is imperative.China's current national V motor gasoline standard stipulates that the sulfur content of gasoline should not exceed 10.0?g/g.Therefore,the research of deep desulfurization technology for gasoline with high efficiency,mild reaction conditions and simple operation has important significance.In this paper,four kinds of PbO2/Ti electrodes were prepared as anodes,and Cr2O72-was used as the oxidizing medium to study the electrochemical oxidative desulfurization of straight-run gasoline.The electrocatalytic effect of anode materials was evaluated,and the experimental conditions such as electrolyte concentration,current and temperature were optimized.A possible mechanism of oxidative desulfurization is proposed according to the analysis results.The anode material has a great influence on the electrochemical oxidation process.Here,we prepared the Pb02/Ti electrode and the metal(Ni,Co,Cu)doped Pb02/Ti electrode by electrodeposition and evaluated the desulfurization efficiency of high-sulfur straight-run gasoline with four kinds of electrodes as anodes.The experimental results showed that under certain conditions,all four electrodes were excellent in electrocatalytic performance,and the desulfurization rate of gasoline is above 80.00%.However,the desulfurization rate of Cu-PbO2/Ti as an anode is higher than others,which is 86.52%.The addition of the valence metal ions to the electrolyte not only enhances the oxidation of the organic sulfides,but also enables the recycling of the electrolyte.In this paper,H2SO4 and Cr2(SO4)3·6H2O were mixed to form a composite electrolyte,which was used in the electrochemical oxidation desulfurization of straight-run gasoline.The results showed that the desulfurization rate of gasoline is 85.74%when used H2SO4 as electrolyte and then raised to 95.07%after added an appropriate amount of chromium sulfate.Cr2O72-was generated form the oxidation of Cr3+during electrolysis,which could react with organic sulfide and oxidize it to sulfoxides,sulfones or sulfonic acids,while itself was reduced to Cr3+,thereby achieving the circulation of the electrolyte.After the determination of the electrolysis system,the experimental conditions were optimized and the recycling of the electrolyte was studied.Under the optimal conditions,such as content of Cr2(S04)3·6H2O,0.5mol/L;weight percent of H2SO4,50.00%;applied current,400mA;electrolysis temperature,50?;stirring speed,1000r/min;the volume ratio of electrolyte/oil,2.5;electrolysis time,60min,the sulfur content of gasoline is reduced from 911.5?g/g to 8.5?g/g,and the desulfurization rate is 99.16%.After seven times reused of the electrolyte,the sulfur content of gasoline could still be reduced to less than 10.0?g/g.Finally,n-octane and thiophene were mixed as a simulated oil,and the electrolyte and simulated oil before and after electrochemical oxidation were analyzed by UV-Vis,FTIR and GC-MS.The analysis results show that Cr3+in the electrolyte can be converted into a strong oxidizing medium Cr2O72-during electrolysis,which can oxidize the organic sulfides in the oil to high-boiling sulfoxides,sulfones and sulfonic acids. |
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