Catalytic Combustion Of Formaldehyde Over Cu-doped Mn-ce-o Solid Solution Catalysts

A series of CuO-doped Mn-Ce-O composite oxides and their supported Pd catalysts were prepared using co-precipitation and impregnation methods, and their performance on catalytic combustion of Formaldehyde were investigated. The relation between the catalytic activity of these composite oxides and their structures were characterized by XRD, Raman spectra and H2-TPR experiments.When the molar ratio of Mn to Ce is 2:8, the Mn-Ce-O composite oxide showed highest activity for catalytic combustion of Formaldehyde and further, fluorite CeO2 was detected from this Mn-Ce-O composite oxide. The Raman peak of Ce-O shifted to high wave-number region due to doping of Mn and this disclosed the strong interaction between Mn and Ce, which resulted from the formation of Ce-Mn-O solid solution.Cu was introduced to Mn-Ce-O composite oxide by two doping methods: co-precipitation and impregnation. It was found that the preparation methods have a major effect on the activity of catalysts for combustion of formaldehyde. The results demonstrated that CuO-Mn-Ce-O composite oxide prepared by co-precipitation method showed higher catalytic activity and higher dispersion of amorphous CuO than CuO-Mn-Ce-O composite oxide prepared by impregnation method. Cu-doped Mn-Ce-O composite oxide with 5.0 wt.% CuO showed highest activity for catalytic combustion of Formaldehyde. When CuO loading lowered below the dispersion threshold (5.0 wt.%), the activity for catalytic combustion of Formaldehyde enhanced with the increase of the doping amount of Cu and, on the contrary, the increase of CuO loading amount had an adverse effect on catalytic activity when it exceeded the dispersion threshold. For CuO-Mn-Ce-O composite oxide, Cu2+ and Mn3+ in which ionic radius are all below that of Ce4+ can partially enter the crystal lattice of CeO2 to form Cu-Mn-Ce-O solid solution with the structure like fluorite CeO2. It proved that the formation of Cu-Mn-Ce-O solid solution and highly dispersed amorphous CuO played the main role in enhancing catalytic activity for catalytic combustion of Formaldehyde. Amorphous PdO was highly dispersed on the surface of Cu-Mn-Ce-O composite oxide in PdO/Cu-Mn-Ce-O catalyst. High activity of this catalyst can be attributed to highly dispersed PdO and CuO on the surface of support and synergistic interaction between Pd-Cu-Mn-Ce.