Performance and mechanism of cerium-praseodymium-manganese(CePrMnOx)solid solution in catalytic soot combustion

ZHAO Xinyi; REN Yichen; JIANG Ruolan; LIU Jianxun; ZHANG Jian; LIU Wei; WANG Zhongpeng

doi:10.13732/j.issn.1008-5548.2025.04.015

Abstract：Objective To enhance the regeneration efficiency of diesel particulate filters(DPFs),it is necessary to increase the lattice oxy-gen mobility and active oxygen content,thus improving the soot oxidation capacity of the catalyst at medium and low tempera-tures.Therefore,it is critical to develop an efficient and cost-effective catalyst that can facilitate soot oxidation under these conditions. Methods In this study,pure metal oxides,CePrOx,and CePrMnOx catalysts were synthesized using the cetyltrimethylammonium bromide(CTAB)assisted co-precipitation method.The physical and chemical properties of these catalysts were characterized by various analytical techniques.Their structure and morphology,defect degree,reduction ability,oxidation ability,and mech-anism were systematically studied. Results and Discussion Based on the characterization and experimental results,the catalytic oxidation activity test curves of soot showed that co-doping with Pr and Mn increased lattice oxygen mobility and reactive oxygen content in the catalysts.Specifi-cally,the CePrMnOx catalyst exhibited superior low-temperature oxidation ability for soot,and its t10 and t50values were 85℃and 67℃ lower than those of CeO2,respectively.X-ray diffraction(XRD)results confirmed that Pr and Mn elements were suc-cessfully doped into CeO2 lattice,leading to lattice distortion.This distortion,which altered the lattice symmetry and oxygen ion migration pathways,was likely the key factor in improving lattice oxygen mobility.Nitrogen adsorption-desorption experiments showed that the CePrMnOx catalyst hada larger specific surface area and pore volume,suggesting more active sites for reactants to interact with,thus improving the catalytic efficiency.SEM results revealed the presence of nanorods in the CePrMnOx cata-lyst,which improved the contact efficiency of active sites and further enhanced the catalytic performance.Raman and temperature-programmed reduction(TPR)results showed that the CePrMnOx catalyst hada higher oxygen vacancy concentration and stronger reduction ability.X-ray photoelectron spectroscopy(XPS)results suggested that this was due to the higher content of Ce3+,Mn3+,and surface reactive oxygen species in the CePrMnOx catalyst.In situ diffuse reflectance infrared Fourier trans-form spectroscopy(DRIFT)results showed that carbonates were the main intermediate reaction products for both CePrOxand CePrMnOx catalysts.The bidentate carbonates on the surface of the CePrOx catalyst did not fully participate in the reaction,thus covering the active sites and limiting the improvement of catalytic activity.In contrast,the CePrMnOx catalyst,with its higher active oxygen content and oxygen vacancy concentration,promoted carbonate conversion more effectively,thus improving the catalytic efficiency. Conclusion 1)The CTAB-assisted co-precipitation method not only maintains the cubic fluorite structure of CeO2 but also suc-cessfully introduces Pr and Mn elements into the CeO2lattice.This co-doped catalyst exhibits a larger specific surface area and has more active sites for reactant interaction,thus improving catalytic activity.Moreover,this method enhances the redox capac-ity of the catalyst,which is particularly important for catalytic oxidation reactions.It promotes the activation and transfer of oxy-gen,thereby improving the catalytic efficiency.2)Mn doping has a significant impact on catalyst performance.The introduction of Mn enhances the oxygen migration ability of the catalyst and increases the content of chemisorbed oxygen on the surface.Effi-cient oxygen migration is vital for soot oxidation.Additionally,higher surface chemisorbed oxygen content means more oxygen molecules can be adsorbed on the catalyst surface,providing more reactive oxygen species for oxidation reactions.These charac-teristics collectively improve the catalyst performance in soot oxidation reactions,making it more efficient at low temperatures.3)During soot oxidation,bidentate carbonates are the main reactive species.However,bidentate carbonates on the surface of the CePrOx catalyst may cover active sites,reducing catalytic activity.This occurs because the adsorption of bidentate carbon-ates may hinder reactant contact with the active site.In contrast,the CePrMnOx catalyst,due to its optimized surface properties and enhanced oxygen migration capacity,can convert bidentate carbonates more efficiently.This reduces active site coverage and improves catalyticactivity.These findings indicate that the CePrMnOxcatalyst performs better in soot oxidation,which is sig-nificant for improving catalytic efficiency and reducing environmental pollution.