The Synthesis Of Mesoporous Manganese And Cobalt Oxide And Its Catalytic Oxidation Of Ethanol And Formaldehyde

Based on energy and environmental strategies, the development of automotivealternative fuels becomes an inevitable trend. The physical and chemical properties ofethanol and gasoline are similar and ethanol is renewable energy, so it is regarded asone of the most promising alternative fuel. Although ethanol itself does not containimpurities such as sulfur, nitrogen, phosphorus, benzene, but unregulated pollutantssuch as alcohol, aldehyde, etc exist in the vehicle exhaust. These pollutants can causeserious damage for the atmospheric environment and human health. However, thetraditional automotive three-way catalyst can not effectively remove these alcohols andaldehydes pollutants. Therefore, the research and development of new catalyst forremoving alcohols and aldehyde have important scientific significance and practicalvalue.In this paper, mesoporous MnO2and Co3O4catalyst have been prepared by usingKIT-6and SBA-15mesoporous silica as hard template agent. On this basis, differentcatalysts supported Ag were prepared by different methods. The catalytic performanceof all catalysts for ethanol and formaldehyde oxidation was studied systematically. Allcatalysts have been characterized by a variety of technologies. The reaction mechanismsfor formaldehyde oxidation on Ag supported catalysts were discussed in-depth. Themain results of the paper are following.(1)1D-MnO2synthesized by the hydrothermal method was the single-crystalnano-rod with the tetragonal structure.2D-MnO2and3D-MnO2prepared by the hardtemplate method possess two-dimensional (2D) and three-dimensional (3D) porechannel structure, respectively.3D-MnO2has the best low-temperature catalytic activityof ethanol and formaldehyde, and complete conversion for ethanol (300ppm ethanoland45000mL/(g.h)) and formaldehyde (500ppm HCHO and30000mL/(g.h)) is150°C and130°C, respectively. It is due to more surface active oxygen species, thenumber of active Mn4+cations and better reducibility.(2)3D ordered mesoporous Ag2O-MnO2and Ag/MnO2were prepared on thebasis of3D-MnO2. Ag2O-MnO2prossess Ag+oxidation state, stronger interaction Agwith Mn, more lattice defects and surface lattice oxygen (O2-) species. Ag2O-MnO2catalyst shows more excellent catalytic activity of HCHO due to Ag+and O2-as active species.(3)2D-Co3O4and3D-Co3O4catalysts were prepared by the hard template method，and nano-Co3O4was synthesized by precipitation method. The2D-Co3O4and3D-Co3O4catalysts have larger surface areas and mesoporous properties of theircorresponding hard templates.3D-Co3O4has better catalytic acitivity. Basis on3D-Co3O4, mesoporous Ag/Co3O4and K-Ag/Co3O4catalysts were successfullyprepared. Ag nanoparticles were uniformly dispersed and supported on thepolycrystalline wall. The addition of K+ions strengthens anion lattice defects andinteraction of Ag and Co3O4support, and form more Co3+ions and surface latticeoxygen species. The K-Ag/Co3O4sample has better catalytic performance of HCHOoxidation than the Ag/Co3O4catalyst due to the existence of surface OH-species andthe exposure of Ag (111) active faces. The TOF of K-Ag/Co3O4sample is0.22s-1at60°C. The pathway of reaction for HCHO oxidation on the K-Ag/Co3O4follows theHCHO�'CHOO-+OH-�'CO2+H2O route.