Preparation Of Copper And Manganese Oxides And The Characteristic Of Catalytic Combustion Of VOCs

Catalytic combustion is a simple and effective way for the treatment of volatile organic compounds,which avoided the yield of NO_x,CO,etc. Catalyst is the key of catalytic combustion,so it is necessary to search a kind of catalysts with relatively high activity,themal stability,poison resistance and less expensive.Particle and monolithic ceramic Cu-Mn mixed oxides were prepared respectively and their further catalytic performance was studied.Then the best catalysts were applied to catalytic combustion of VOCs in comparison to commecial noble catalysts.Some conclusions were drawn as follows:Firstly,particle Cu-Mn-O catalysts were prepared through co-precipitation method and washed by ethanol to remove impurities.The results showed that the catalysts with high specific surface area and catalytic activity could be obtained,and the conversion of toluene could reach above 95%at 220℃on catalysts calcined at 500℃. Ethanol-washing could improve the dispersivity of nanoparticle and restrain the sintering of CuMn₂O₄ phase.Compared with water-washed samples,the ethanol-washed catalysts calcined at 700℃and 800℃showed high themal stability,and the total combustion temperature of toluene declined nearly 60℃and 50℃respectively.Secondly,a series of Cu-Mn-O mixed oxides supported on cordierite honeycomb were prepared by an impregnation method.In particular,the effect of preparation variables including the ion concentration,Cu/Mn ratio and calcination temperature on the activity were investigated for the oxidation of toluene.The results showed that Cu and Mn ions were uniform and well-alhered on the surface of support.The relationship between Cu/Mn ratio in solution and surface of catalysts was proven to be linear. The catalysts showed better catalytic activity while Cu/Mn ratio was 1/6, when Cuo and Mn₂O₃ phase had been at work to improve the catalytic performance.The catalytic activity declined along with the increase of calcination temperature for the sintering of particles.Thirdly,the third metal elements were adopted to improve the catalytic performance.The order of catalytic activity was as follows, Cu₁Mn₄Ce₂/Cord＞Cu₁Mn₄Zr₂/Cord＞Cu₁Mn₆/Cord＞Cu₁Mn₄Zn₂/Cord＞Cu₁Mn₄Fe₂/Cord＞Cu₁Mn₄Al₂/Cord＞Cu₁Mn₄V₂/Cord.The addition of Ce improved the ability to supply oxygen of Mn₂O₃.Further,the content of Ce was investigated.It was found that when Cu:Mn:Ce was 1:2:4,catalytic activity and themal stability were obviously enhanced for the formation of CeO₂ phase with prominent ability of oxygen storage and mass transfer.Finally,to test the applicability of Cu₁Mn₂Ce₄/Cord catalysts,catalytic performance on various VOCs(aromatics,alkanes,oxygenous,nitrogenous and chlorinated organic compounds) was investigated.The results showed that oxygenous organic compounds were easily oxidized except aromatics. Cu-Mn-Ce catalysts exhibited outstanding low-temperature activity which was significantly better than that of the commercial noble catalysts for the oxidation of VOCs except aromatics.