Preparation And Soot Catalytic Combustion Activity Of CeO₂-ZrO₂ Paper Catalyst

Diesel engine has many advantages such as high thermal efficiency,low speed torque and wide power coverage,which emerges as the main condidate for automotive engine.However,the emissioned soot particles are hard to eliminated,and become an important factor that restricts its development.The paper catalysts with high porosity,good heat transfer and gas diffusion capacity（especially in lateral direction）,give the prospect of a very attractive application in the field of soot elimination.In this paper,the CeO2-ZrO2（CZ）paper catalysts were fabricated by using traditional papermaking method,and homogenous CuO@CeO₂-ZrO₂（CZCu）fibers with high aspect ratio,together with the mullite fibers as the matrix.The effects of optimized forming process and various supported active components on the catalytic activities towards soot oxidation,are also studied extensively.First of all,the appropriate amounts of short cut mullite fibers and alumina sol were studied in order to improve the forming quality,mechanical properties,as well as catalytic activities of the paper catalyst.It was found that in a suitable processing range,the tensile strength was enhanced with the increased amounts of mullite fibers,while the catalytic activities were reduced.In contrast,the tensile strength was reduced with decreased amounts of alumina sol,while the catalytic activities were enhanced.The optimized composition of the CeO₂-ZrO₂ paper catalyst was listed as follows:1 part of CuO@CeO2-ZrO2 fibers,1 part of short cut mullite fiber,0.5¹parts of lignin fiber,1.1 parts of aluminum sol,0.25 parts of polyvinyl alcohol.In that case,the T₁₀,T₅₀,and T₉₀ values of the soot catalytic combustion process were309℃,396℃,and 509℃,respectively.Futhermore,the selected conversion percentage of CO₂(S_CO2)was as high as 96.5%.Secondly,the effects of various supported active ingredients（CuO,MnO₂,Co3O4 and NiO）on the catalytic activities towards soot oxidation were investigated by loading the same amount of 8%（wt.）.It was found that the order of their catalytic activities was as follows:CZ-8CuO>CZ-8MnO₂>CZ-8Co₃O₄>CZ-8NiO.For the paper catalyst supported with different amuonts of CuO（5%,8%,10%and 20%）,it exhibited the best catalytic activity for the sample loaded by 8%（wt.）with the T50value was as low as 372℃,and the selected conversion percentage of CO₂(S_CO2)can reached 97.7%.Finally,the effect of KNO₃ as active ingredients with different loading amounts of 6%,8%,and 10%（wt.）are studied.It is found that KNO₃ can improve the contact degree between the soot with the catalyst and provide oxidation active sites and promote the catalytic combustion of the soot.With the increase of KNO₃ loading,the soot catalytic combustion ability of the sample is increasing,in the range of 6%¹0%.In 21%O₂/N₂ atmosphere,when the KNO₃ loading is 10%,the T₁₀,T₅₀ and T₉₀ values of the soot catalytic combustion were 293℃,448℃ and 509℃,respectively,and the CO₂ selected conversion was 100%.