Preparation Of Manganese Based Catalyst And Its Catalytic Oxidation Performance Of Methanol

The pollution of volatile organic compounds（VOCs）has become an important environmental problem to be solved urgently.At present,the catalytic oxidation process has been proved to be an increasingly mature VOCs treatment technology,the core of the treatment technology lies in the development of efficient catalytic materials.In this paper,highly efficient manganese based catalysts were developed with methanol as the target pollutant,the structure-activity relationship between the physical and chemical properties of manganese based catalysts and the catalytic activity of methanol oxidation was discussed,and the conversion path of methanol was deduced.The main contents and conclusions are as follows:（1）Study on the structure-activity relationship between the preparation of MnO₂catalysts with different morphology and the catalytic activity of methanol oxidation.By hydrothermal synthesis method,the experimental parameters such as manganese salt precursor,reaction temperature and time were controlled to control the formation of the morphology structure of MnO₂,and one-dimensionalα-MnO₂-X nanowires,γ-MnO₂-B nanorods and two-dimensionalδ-MnO₂-P nanosheets catalytic materials were prepared,and the morphology effect of methanol catalytic oxidation reaction of different MnO₂materials was studied.The results showed that there were significant differences in physical and chemical properties of MnO₂materials with different morphology,such as specific surface area,crystal structure,low temperature reduction and reactive oxygen species.Compared withα-MnO₂-X andγ-MnO₂-B,the two-dimensional structure ofδ-MnO₂-P exhibits better low temperature reduction,abundant Mn⁴⁺and surface lattice oxygen,and its exhibits better reactivity with T₁₀,T₅₀and T₉₀values of 83℃,113℃and134℃,respectively（T_Xvalue represents the corresponding reaction temperature when the yield of CO₂produced by methanol reaction is X%）.（2）Construction of core-shell catalysts with different forms of Manganese oxide and study on structure-activity relationship of methanol catalytic oxidation reaction.In an innovative design,sheetδ-MnO₂-P was grown on the surface of Mn₂O₃-Q micro-spheres construct core-shell Mn₂O₃@δ-MnO₂materials with different manganese morphology combinations,and considering the assembly time factor,the growth degree of core-shell could be controlled and the core-shell samples under different assembly time were obtained,and the catalytic effect of Mn₂O₃@δ-MnO₂samples on methanol was investigated.The results show that compared with Mn₂O₃-Q andδ-MnO₂-P,Mn₂O₃@δ-MnO₂interface structure can accelerate the low temperature reduction of Mn⁴⁺→Mn²⁺,and promote the formation of abundant surface lattice oxygen on the surface of the catalyst,therefore,Mn₂O₃@δ-MnO₂core-shell samples show better methanol reaction activity.Among them,Mn₂O₃@δ-MnO₂-8h has the best catalytic activity with T₁₀,T₅₀and T₉₀values of 68℃,104℃and 119℃,respectively.（3）Preparation of Pt/MnO₂catalysts with different supports and study on structure-activity relationship of methanol catalytic oxidation.Three kinds of Pt/MnO₂catalysts with semi-encapsulated Pt/MnO₂hetero-structures were obtained by loading Pt nanoparticles（Pt NPs）onto the surface of MnO₂materials with different morphology（nanowire,nanorod and nanosheet）through multiple combinations;The influence of metal-support interaction regulates the surface local cooperative environment of the support on the overall physical and chemical properties of Pt/MnO₂catalyst and its special effect on catalytic oxidation of methanol.The results showed that changing the local cooperative environment of Pt-Mn on the support surface through the interaction of Pt NPs and MnO₂could significantly improve the physical and chemical properties of Pt/MnO₂catalyst(such as low temperature reduction,Mn⁴⁺and surface lattice oxygen,etc.),thus showing better methanol reactivity.Among them,Pt/α-MnO₂-X had the best catalytic activity of methanol,with T₁₀,T₅₀and T₉₀values of 46℃,67℃and 91℃,respectively.In addition,the possible conversion path of methanol on the catalyst surface is confirmed by In situ DRIFTS:methanol→formaldehyde,methyl formate and formate substances→short chain carboxylate and carbonate→CO₂and H₂O.