Preparation Of Cu-Mn-Zr Composite Catalyst And Its Degradation Characteristics For Ethyl Acetate

Volatile organic compounds（Volatile Organic Compounds,VOCs）have a wide range of diverse sources,as a toxic substance,it can not only cause photochemical smog,ozone damage and plant decay and other environmental problems,but also hazardous to human health.The catalytic combustion method can convert organic waste gas into carbon dioxide,water and other relatively less harmful compounds at a low temperature（usually at 200-500℃）,it has advantages of low energy consumption and less by-products,and how to improve the catalyst’s low temperature catalytic activity and stability are still the hot topics of the research.In this paper,a series of Cu-Mn-Zr composite oxide catalysts were prepared by sol-gel method.We studied the effects of preparation methods on the performance of the catalysts.And the influence of catalytic degradation of ethyl acetate on the removal efficiency and CO₂ selectivity was investigated.We used a series of characterization techniques to study the physicochemical properties of the catalyst,and the mechanism of catalytic degradation of ethyl acetate was analyzed.The main conclusions are as follows:（1）The effects of preparation conditions such as molar ratio of active metal components and calcination temperature on the catalytic performance of ethyl acetate were studied.The results showed that the Cu-Mn-Zr（1:1:1）catalyst prepared under calcination at 400℃ had the best degradation effect and lower temperature catalytic activity.Its T50 =166℃,T90 = 194℃,and its CO₂ selectivity was the highest.The CO₂ selectivity at 260℃ was 96.29%.（2）The Cu-Mn-Zr composite oxide catalysts were characterized by BET,XRD,XPS,SEM and TEM.The BET analysis showed that the catalyst has a uniform pore size distribution and a highly dispersed amorphous structure.The XRD analysis showed that the addition of Mn is conducive to the formation of highly dispersed amorphous materials.The calcination temperature increased the formation of CuO,MnO₂ and tetragonal ZrO₂.XPS analysis showed that CuO,MnO₂ and tetragonal ZrO₂ accounted for the largest proportion of Cu-Mn-Zr（1:1:1）catalyst prepared at calcination temperature 400℃.（3）We studied the effects of initial ethyl acetate concentration,space velocity,temperature and O₂ content on the catalytic oxidation of ethyl acetate and its effect on the selectivity to CO₂.Ethyl acetate removal and CO₂ selectivity decreased with the increasing of initial concentration and increasing airspeed,and increased with the increasing of temperature O₂ content.The higher temperature,the smaller the effect of the influencing factors.The removal rate of ethyl acetate and the selectivity of CO₂ were investigated with Cu-Mn-Zr（1:1:1）at 240 ℃ with the initial concentration of 1075.08 mg/m3,the space velocity of 24000 h-1 and the O₂ content of 40%the composite catalyst had the highest removal rate is 98.32%and selectivity of CO₂ was 96%.（4）Before and after the catalytic reaction of the catalysts were characterized by BET,XRD and XPS,and the catalytic reaction mechanism was studied by ATR,GC and other analysis.By BET analysis,the specific surface area and pore volume of the aged catalyst decreased significantly.XRD analysis showed that the oxides in the pre-reaction catalyst were present in a uniform,highly ordered,amorphous structure.After aging,copper oxide crystals and zirconium dioxide crystals appeared.The active materials that played a major role in the catalytic oxidation reaction analyzed by XPS are Cu2+,Mn4+ and Zr4+ in tetragonal zirconium dioxide.The results of ATR analysis and GC analysis showed that in addition to the presence of ethyl acetate,water and carbon dioxide on the surface of the catalyst,a very small amount of intermediate products such as ethanol and acetic acid may existed.The catalytic oxidation of ethyl acetate took place in two main stages.First,ethyl acetate was hydrolyzed to acetic acid and ethanol,which were then further oxidized to carbon dioxide and water.