Preparation Of Heteropoly Acid Catalysts And Its Performance On Catalytic Oxidation For Diesel Deep Desulfurization

Most countries all over the world have made the increasingly stringent of automotive diesel sulfur content standards with the enhancement of human environmental protection consciousness.Therefore,the production of low sulfur or ultra-low sulfur diesel become an inevitable trend.Much attention has been paid to the oxidation desulfurization due to its mild reaction conditions,high desulfurization efficiency,and green process environmental protection.In this thesis,synthesis of a variety of mesoporous molecular sieves such as MCM-41,SBA-15,MCM-48 and micro-mesoporous composite molecular sieves MCM-48/ZSM-5.A series of supported phosphotungstic acid catalysts were prepared by supersaturated impregnation method with phosphotungstic acid on these molecular sieves.The molecular sieves and catalysts were characterized by means of XRD,FT-IR,N2 adsorption-desorption,TG-DTA,SEM and TEM.The effects of different carriers and catalysts preparation conditions on the desulfurization performance were investigated by using H2O2 as the oxidation agent and CTAB as phase the transfer catalyst.Meanwhile,the influences of oxidation-extraction conditions on straight-run diesel oil desulfurization were investigated.Finally,the effect of extraction separation technology on sulfur removal and yield of diesel oil were examined.The results showed that the mesoporous molecular sieve MCM-41 and SBA-15 were more suitable to the the carrier of phosphotungstic acid than ZSM-5.Moreover,HPW/SBA-15 catalytic activity were slightly better than that of HPW/MCM-41.The best mass percentage of HPW was 30% and HPW/SBA-15 showed the highest activity at 250?.In H2O2-HPW/SBA-15-CTAB catalytic oxidation desulfurization system,the sulfur content in the diesel oil decreased from 1317 mg/L to 39 mg/L and the sulfur removal reached 97.0% under the optimal conditions when n(H2O2):n(S)rate was 6,the mass fraction of HPW/SBA-15 was 2.5wt%,mass fraction of CTAB was 0.40wt%,furfural as the extraction solvent and the extraction stage was 4,the reaction temperature was 60? and the reaction time was 1.5h.The yield of diesel was no less than 75.0% and the extraction process was the main cause of diesel yield reduction.The catalytic activity order of three kinds of supported phosphotungstic acid catalysts was HPW/MCM-48 > HPW/SBA-15 > HPW-MCM-48/ZSM-5.However,the recycling effect of HPW-MCM-48/ZSM-5 was better than the other two,whereas the decrease in sulfur removal efficiency were noly 1.1% after the catalyst was recycled five times.The sulfur removal of single extraction agent such as furfural or NMP was very high,but the yield of diesel had certain losses.It could improve the yield of diesel oil when adding a small amount of distilled water into the single extraction,but the sulfur removal reduced.selected two best composite extracting agents balanced the sulfur removal and yield,the one is volume fraction 95% furfural water solution and the other is volume fraction 95% NMP water solution.Using HPW/MCM-48 as catalyst under the optimal conditions of catalytic oxidation-extraction desulfurization,volume fraction of 95% furfural water solution as the extraction agent,the sulfur removal and yield of the straight run diesel reached 97.1% and 83.75%,compared with the single extractant furfural the yield increased by 7.5% and the sulfur removal fell by only 0.5%,therefore improved the economic benefits of the oxidation desulfurization.