Investigation On The Preparation And Soot Catalytic Performance Of Tin-based Oxide Fibers

Diesel engines are widely used in diesel vehicles with the advantages of good economy,high reliability and high thermal efficiency.However,the exhaust emissions from diesel vehicles pose a serious threat to human health and the environment.In particular,soot particles are the main source of air pollution and the main cause of haze,which may deposit in human lungs through the respiratory system.At present,diesel particulate filter(DPF)technology is the most effective post-treatment technology to remove soot particles.Honeycomb ceramic DPF has the advantages of large specific surface area,high filtration efficiency and high temperature resistance to the most widely used structure.However,the accumulation of soot particles in DPF will block the pores of the filter,reduce the filtration efficiency and cause engine exhaust back pressure,so it is necessary to remove the deposited soot particles for combustion purification.The catalyst can reduce the reaction activation energy of soot combustion,reduce the temperature of soot combustion,and increase the oxidation rate of soot to realize the regeneration of DPF.In this paper,tin based oxide fiber catalysts were prepared by electrospinning technology and applied to study the catalytic performance of soot particles.The main contents of the work are as follows:1.The preparation method of tin oxide fiber was optimized.The powder of tin oxide precursor was prepared by two-step solvent method.The precursor,named as polyhydroxyltriacetictin(PHTES),was easy to form sol.It has the advantages of high molar content of tin and high solid content of tin oxide fiber.It decreases considerably the amount of spinning agents in the electrospinning sol,which solves a lot of problems,such as low molar content of the target elements in the sol,poor strength,poor morphology,uneven grain size and easy pulverization of the fiber after high-temperature aerobic treatment,large diameter of the fiber obtained by centrifugal spinning method,and the problem of agglomeration of nanoparticle morphology materials.2.The effects of heat treatment temperature on the morphology and physicochemical properties of tin oxide fibers were studied,and the catalytic oxidation performance of tin oxide fibers on soot particles was tested.The results show that the fiber heat treated to 500℃ in air atmosphere has the best catalytic effect on soot particles.When the conversion is 10%,50%and 90%,the corresponding temperature is 404℃,450℃ and 474℃,respectively,and the selectivity of CO2 is increased to more than 95%.Tin oxide surface is rich in oxygen vacancies,which can absorb a large number of active oxygen involved in soot oxidation.Moreover,nanostructured fibers have the advantages of high specific surface area,network structure arrangement and high porosity,which can effectively promote the contact between soot particles and catalyst and improve the catalytic efficiency.3.The structure and soot catalytic activity under loose contact conditions of SnxCe1-xO2 fiber catalysts with different ratios were studied.When Ce enters into the crystal lattice of SnO2,the structural symmetry of SnO2 is destroyed,the crystallization and grain growth of the fiber are inhibited,and the fiber catalyst with larger specific surface area is obtained.Moreover,the addition of Ce improves the number of oxygen vacancies and redox ability of the catalyst,thus promoting the catalytic activity of the catalyst for soot particles.In particular,the Sn0.7Ce0.3O2 fiber catalysts have the strongest catalytic oxidation ability to soot particles,and can complete the oxidation of soot particles at a lower temperature and faster catalytic rate.The results of temperature programmed oxidation of Sn0.7Ce0.3O2 fiber catalyst for three times under the same conditions were basically consistent,indicating that the experimental results are reliable and repeatable.In addition,Sn0.7Ce0.3O2 fiber catalyst showed good cycle stability.