Investigation Of Preparation Technology And Performance Of 3DOM Monolith Soot Catalyst

Engine-out emissions are sources of the main outdoor air pollutants,consisting of volatile organic compounds?VOCs?,nitrogen oxides?NOx?and particulate matter?PM?,which is harmful to people's living environment and physical health.At present,the combination of a diesel particulate filter and a low-temperature,high-activity catalyst is one of the effective ways to eliminate PM.There is a layer of regular macropores with pore size is about 200 nm on the surface of the three-dimensional ordered porous monolith catalyst.The nanosized pore structure can increase the specific surface area of the catalyst while promoting full contact between the soot and the catalyst.It shows superior practical application than powder catalysts in the catalytic oxidation of carbon soot particles.In this paper,cordierite was used as substrate,zirconium dioxide nanosol as additive,and PMMA as template,and monolithic soot catalyst with a three-dimensional ordered structure was prepared by dip coating.The effect of coating time,coating times,curing time,and curing temperature were mainly studied,and determined that the loading was optimal preparation conditions.Second,the effect of Ce content on the catalytic performance of MnOx-CeO2 and CuMn2-xCexO4 were studied.The prepared monolithic catalyst was characterized by a series of methods such as XRD,SEM,BET,Raman and XPS.Finally,the catalytic performance and the anti-high temperature performance of the catalyst on soot were studied in detail.This study successfully built a three-dimensional ordered macroporous structure on the surface of cordierite.The macropores of the surface layer on substrate were connected to each other through a small window with a diameter of 60±5 nm,and the underlying structure was highly visible.The polymer templating agent melted during the firing process to cause pore structure shrinkage,resulting in a prepared pore size of160±10 nm,slightly smaller than the PMMA diameter.The macroporous structure not only increased the specific surface area of the monolith catalyst,but also improved the gas flowability,increasing the contact area between the catalyst and the soot,and exposing more active sites than non-porous particles,promoting soot combustion.The study result of MnOx-CeO2 catalysts with different Ce contents show that with the increasing of Ce content,Mn gradually entering CeO2 lattice,suppresing CeO2 grain growth,causing crystallinity of CeO2 to decrease,and the specific surface area increasing.When the mole ratio of Mn and Ce exceeded 1:1,CeO2 lattice could not hold Mn.Mn⁴⁺,Ce³⁺/(Ce³⁺+Ce⁴⁺)values and oxygen vacancy concentration decreased and the activity of the catalyst also decreased.The study of different Ce content CuMn_2-xCe_xO₄ catalysts show that the tetrahedral position was occupied by Cu²⁺,and the octahedral position was occupied by Mn³⁺.When the CeO2 content is low,it acted as a load-hole barrier agent,and when the content was high,the sample provided the main structural characteristics.With the increase of niobium content,CeO2 fluorite peaks gradually increased.When the Ce content exceeded 0.3,manganese or copper was introduced into the fluorite crystal lattice,the crystal lattice shrink,and the manganese-germanium solid solution separated and the soot catalytic activity was reduced.