Preparation And Characterization Of Copper-based Catalysts For Catalytic Combustion Of Ethyl Acetate

In recent years,Volatile Organic Compounds（VOCs）have been well known as environmental harmful pollutants.Catalytic combustion is widely used in the field of VOCs elimination due to low cost,high efficiency and convenient operation.The catalyst plays crucial role in the catalytic combustion method.However,precious metal catalysts such as Pt and Pd are high cost,easy sintering and short catalytic lifetime,although they can be used for most of the VOCs.Therefore,it is great significance to develop transition metal catalysts owning high catalytic activities to replace the precious-based catalysts.Copper-based catalysts comparing to the others transition metal catalysts have not only the advantage of low cost and but also high catalytic performances for catalytic combustion reaction.The dispersion of a catalyst is always a critical factor for catalytic activity.However,it is still a big challenge to prepare highly dispersed catalysts using a simple and eco-friendly method.In this paper,the ball milling method was used instead of the traditional impregnation method to prepare highly dispersed Cu-based catalysts under free-solvents and room temperature conditions.The particle of copper was<2 nm as the copper loading was<20 wt%over the silica support.Comparing with the catalyst prepared by the traditional impregnation method,the catalysts prepared with the ball-milled method showed better activity for the catalytic combustion of ethyl acetate.Using TG-DSC,XRD,XPS,TPR,FT-IR,TEM and N₂O chemisorption techniques,the structrural evolution and the catalytic activity and structure relationship of the Cu-based catalysts prepared by ball milling were elucidated.The following conclusions were reached in this dissertation:（1）The ball milling method was adopted to prepare copper-based catalysts instead of traditional impregnation.Green preparation of highly dispersed copper based catalysts under free-solvents and ambient conditions was achieved by using copper acetate precursor replacement of copper nitrate precursor and adjusting operation parameters of ball milling,which was no toxic gases or wastewater emitted during catalysts preparation.（2）We found that copper acetate could react with the Si O₂to form copper phyllosilicate layer with a-Cu-O-Si structure.And the copper phyllosilicate might play an important role in preventing the copper oxide from sintering during thermal pretreatment of catalysts.（3）A series of CuO/SiO₂with different copper loading were prepared via the ball milling method.It was found that the Cu O/Si O₂catalyst with 15%loading of copper exhibited the highest catalytic activity ascribing to its highest copper oxide active surface.And the copper oxide was its active species.（5）The effect of different supports(Alumina（Al₂O₃）,zirconia（Zr O₂）,cerium oxide（Ce O₂）,lanthanum oxide（La₂O₃）,aluminum hydroxide（Al（OH）₃）,zirconium hydroxide（Zr（OH）₄）,Cerium hydroxide（Ce（OH）₄）and lanthanum hydroxide（La（OH）₃）on the catalytic performances was investigated.We found that the catalyst using the cerium hydroxide as the precursor of Ce O₂displayed highest catalytic activity.And the conversion of EA was completely conversed at a low temperature of235°C.The conclusions reached in the dissertation would provide a new methodology to prepare highly dispersed supported transition metal catalysts for the catalytic combustion of VOCs.