Preparation Of Nano-SiO₂ Composite Catalysts With Different Pore Dimensions And Their Catalytic Oxidation Adsorption Desulfurization Performance

The sulfur compounds in the fuel oil are burned to release a large amount of sulfur oxides（SO_x）,which can directly lead to the formation of acid rain and aggravate the generation of smog.Therefore,various countries have legislated to limit the concentration of sulfide in fuel oil（<10ppm）,and deep desulfurization of transportation fuel oils has become an urgent scientific research problem.Oxidative desulfurization technology（ODS）has the advantages of mild reaction conditions,strong removal rate of thiophene sulfur compounds and low cost.It is considered to be the most promising alternative to hydrodesulfurization technology.ODS usually needs to be combined with extractive desulfurization（EDS）to meet the requirements of ultra-low sulphur fuel,but the extractant will cause secondary pollution to the oil and complicate the desulfurization step.Therefore,the development of dual-functional catalysts with catalytic oxidation and adsorption for catalytic oxidation adsorption desulfurization（OADS）will become the development trend of fuel desulfurization catalysts was reserched.In this paper,the oxidation-adsorption desulfurization catalysts.by immobilize phosphotungstic acid on nano-silica of different dimensions（0D,1D and 2D）.The morphology,structure and composition of the catalysts were characterized by XRD,SEM,TEM,EDS,TG,XPS,BET and other test methods.Futhermore,the effect of the microscopic morphology,pore structure,particle size,active components and polar group pairs on the performance of the catalysts were investigated.The reaction mechanism and the principle of catalytic oxidation adsorption desulfurization of catalysts were discussed deeply.The specific research content is as follows:（1）Phosphotungstic acid（HPW）immobilized amino functionalized zero-dimensional nanoporous silica catalytic system（HPW-NH₂-HHSS）were prepared for catalytic oxidation adsorption desulfurization:using hierarchical hollow silica spheres（HHSS）with large specific surface area as the carrier,the amino was functionalized on HHSS with APTEs,and the HPW-NH₂-HHSS series catalysts with zero-dimensional pore structure was obtained by immobilizing H₃PW₁₂O₄₀（HPW）on its surface.The characterization results show that the HPW-NH₂-HHSS catalyst has a nanometer size（about 100nm）and maintains a high specific surface area.Phosphotungstic acid is highly dispersed on the amino-functionalized HHSS carrier,and the HHSS maintains the hierarchical composite hollow structure with original small hollow-spheres@big hollow-shperes,and the surface of the catalyst also contains large polar groups（-NH₂ and-OH）.These properties have a greater impact on its catalytic oxidation adsorption desulfurization performance.The desulfurization performance of 20%HPW-NH₂-HHSS was tested with a solution containing DBT in n-octane.The results confirmed that the desulfurization effect of catalyst arrived 99.36%after 30 minutes when the reaction temperature was 60^oC,O/S=2.5,m_catalyst=0.06.In addition,the catalyst also has good stability,and its desulfurization performance is not obvious reduce after 7 cycles.The oxidation products were analyzed by GC-MS and FT-IR methods,and it was congfirmed that the desulfurization mechanism is catalytic oxidation-adsorption coupling,-NH₂ and-OH polar groups can effectively adsorb sulfur-containing oxidation products,and the maximum equilibrium adsorption value of 20%HPW-NH₂-HHSS catalyst to dibenzothiophene sulfone（DBTO₂）can reach 374mg·g^-1.In this paper,nano-sized hierarchical hollow catalysts（HPW-NH₂-HHSS）with large polar groups（-OH and-NH₂）were synthesized for catalytic oxidation-adsorption desulfurization for the first time（2）phosphotungstic acid（HPW）immobilized amino functionalized one-dimensional nanoporous silica（HSNT）catalytic system（HPW-NH₂-HSNT）was synthesized for catalytic oxidation adsorption desulfurization:the hollow silica nanotubes（HSNT）with one-dimensional pores was synthesized by sol-gel template method,using it as the carrier,the amino was functionalized on HSNT with APTEs.The HPW-NH₂-HSNT series catalyst with one-dimensional pore structure is obtained by immobilizing HPW on its surface.The characterization results show that the HPW-NH₂-HSNT-7 catalyst has a complete hollow tubular structure.The pore structure is composed of the micropores（3.9nm）of the tube wall and the inner diameter of the hollow tube（49.74nm）and maintaining a high specific surface area.Phosphotungstic acid is highly dispersed on the amino-functionalized HSNT carrier,and the HSNT maintains a complete hollow nanotube structure.In addition,the catalyst surface also contains large polar groups（-NH₂ and-OH）,which catalyze its oxidation@Adsorption desulfurization performance has a greater impact.The desulfurization performance of HPW-NH₂-HSNT-7 was tested with a solution containing DBT in n-octane.The results confirmed that the desulfurization effect of catalyst arrived 100%after 15 minutes when the reaction temperature was 60^oC,O/S=3,m_catalyst=0.04g.In addition,the catalyst also has good stability,and its desulfurization performance does not decrease significantly after 10 cycles.The oxidation products were analyzed by GC-MS method,and it was congfirmed that the desulfurization mechanism is catalytic oxidation-adsorption coupling,and-NH₂ and-OH polar groups can effectively adsorb sulfur-containing oxidation products.（3）phosphotungstic acid（HPW）immobilized amino functionalized two-dimensional nanoporous silica（LS:Layered silical）catalytic system（HPW-NH₂-LS）was synthesized for catalytic oxidation adsorption desulfurization:A series of layered silicas（LS）with different morphologies were synthesized by liquid template corrosion,using it as the carrier,the amino was functionalized on HSNT with APTEs,then immobilizing HPW on its surface to obtain HPW-NH₂-LS_w（W is the concentration of ammonia）series catalysts.The characterization results show that the change of specific surface area,particle size,pore diameter and interlayer spacing of HPW-NH₂-LS catalysts with the change of the carrier’s morphology.the catalyst HPW-NH₂-LS₁₃ with a uniform and large layered morphology has Large specific surface area and pore size,the interlayer spacing is between 500nm～1μm,and the catalyst surface also contains large polar groups（-NH₂ and-OH）.All these characteristics are critical for the catalytic oxidation@dsorption Desulfurization activity of the catalysts with two-dimensional channel.The desulfurization performance of HPW-NH₂-LS₁₃ was tested with a solution containing DBT in n-octane.The results confirmed that The desulfurization effect of arrived98.82%after 25 minutes for the reaction temperature was 60^oC,O/S=3,m_catalyst=0.06g.In addition,the catalyst also has good stability and its desulfurization performance does not decrease significantly after 7 cycles.The oxidation products analysis by GC-MS methods,and it was confirmed that its desulfurization mechanism is indeed a catalytic oxidation-adsorption coupling.