Microwave Photochemical Collaborative Catalytic Degradation VOCs From Fumes

Dued to Chinese unique dining habits, the cooking process will inevitably produce more carcinogenic or mutagenic substances. Recently, environmental protection departments had also issued related requirements and policies, then required for compulsory purification of fumes pollution. Traditional techniques for purification fumes had some imperfection, such as high energy consumption, the device configuration was complicated, also had secondary pollution trouble. In this paper, the catalytic combustion was assisted by microwave photochemistry as a newly-developing technology, the VOCs of fumes could be converted to small molecule with higher degradation efficiency.This article adopted titanium dioxide as carrier, the copper and manganese oxides were introduced by co-precipitation method, then copper manganese oxide-titanium dioxide composite catalyst （Cu_xMn_y/TiO₂） were obtained. For comparison, manganese ZSM-5-titanium dioxide composite materials （Mn-ZSM-5/TiO₂） were prepared. This paper researched the structures and properties of materials through TEM, TGA, XRD, XPS, ICP, H2-TPR, etc. The results showed that the copper-manganese atomic ratio of 1:1, loading capacity of 30%, prepared at 45 ℃, calcination under 500℃, Cu_xMn_y/TiO₂ catalyst has the best surface morphology and structural characteristics. When the reaction temperature was 60 ℃, calcination temperature of 400 ℃, TiO₂ loading capacity of 20%-25%, Mn-ZSM-5/TiO₂ showed good morphology.Hexanal was choosed as characteristic pollutants, then found Cu_xMn_y/TiO₂ had better catalytic capability than Mn-ZSM-5/TiO₂, so utilized Cu_xMn_y/TiO₂ to explore reaction conditions. We have studied the impact of the oxygen content, the initial concentration of hexanal, moisture content and hexanal initial concentration, reaction temperature, oxygen and other factors on the n-hexanal removal rate. The results showed that H2O decomposed a small number of OH radicals at low water vapor concentration range then can facilitate the degradation, but when initial concentration of n-hexanal rised, there was competitive adsorption between water vapor and n-hexanal, so had negative effect on the reaction process; under the low temperature water vapor there had absolute inhibiting effect, when the reaction temperature increased, the inhibiting effect of water vapor decreased.Microwave electrodeless light was introduced in this paper, found that had synergistic effect with the catalytic combustion degradation. And n-hexanal degradation mechanism was studied among with a separate photolysis, separate catalytic combustion, and cooperative system. Major role of photolysis was provide hydroxyl radical and generate more acid products, and catalytic combustion offer catalytic oxidation effect so that the n-hexanal was further decomposed under the fine synergistic effect, finally was degraded to small molecule acids and alcohols, and additional acetal material was further disintegrated, and thus achieved full degradation of n-hexanal for harmless purposes.