Preparation Of Copper-manganese Composite Oxide Catalysts And The Performance Of Catalytic Combustion Of Toluene

Volatile organic compounds（VOCs）seriously affect people’s health and social development,and the management of VOCs in the air has become a hot research topic.The catalytic combustion method based on the heterogeneous catalytic mechanism has the advantages of low processing temperature,high processing efficiency,no secondary pollution,continuous operation,and large processing capacity.It is widely used in the removal of VOCs in industrial exhaust gas,automobile exhaust gas and other gases.The catalysts used in catalytic combustion include two types of precious metal type catalysts and non-precious metal type catalysts.Although precious metal catalysts have the advantages of low ignition temperature and high activity,their high price and easy deactivation restrict their industrial applications.In view of this,this article took toluene as the target pollutant and copper-manganese composite oxide as the catalyst to study the catalytic combustion performance of toluene and optimize the preparation parameters of the catalyst;and further analyze the stability of the optimized catalysts and the catalytic mechanism.The main work of this paper is as follows:In order to solve the problems of low catalytic activity and poor dispersion of traditional copper-manganese oxides,with the structure of catechins short chain of dopamine hydrochloride was used as a surfactant,the adjustable morphology and size,high dispersion,excellent catalytic activity of copper-manganese oxide catalyst by a one-pot solvothermal method.And characterize and optimize the catalysts.The results show that the optimal synthesis conditions of copper-manganese oxide catalysts are:temperature of 160℃,time of 14 h,DA of 0.10 mmol,calcination temperature of500℃,calcination time of 4 h;The surface of copper-manganese catalysts modified by dopamine hydrochloride has different morphologies.The catalysts with a copper-manganese molar ratio of 2,1,1/2 are respectively hexagonal,regular quadrilateral and spherical,with high dispersion;through BET characterization and analysis,the specific surface area and pore size of the copper-manganese oxide series catalysts are both small;the catalyst with a copper-manganese molar ratio of 1 mainly forms the CuMn₂O₄ crystal phase,which exhibits the highest catalytic combustion activity.and The temperature of T₅₀（205℃）and T₉₀（221℃）is much lower than other catalysts,indicating that the catalyst has higher catalytic combustion activity in the low temperature section and high temperature section.In order to improve the specific surface area and pore size of copper-manganese oxide,further improve the catalytic performance of toluene,and reduce the preparation cost and energy consumption of the catalyst,this study firstly purified and separated the natural palygorskite support and acid-activated treatment to obtain a relatively highly purity acidic palygorskite,then using the pretreated palygorskite as a support,and using the structure of catechins short chain of short-chain dopamine hydrochloride（DA）and 3,4-dihydroxyphenylpropionic acid（DHCA）,long-chain sodium dodecylbenzenesulfonate（SDBS,anionic）,cetyltrimethylammonium bromide（CTAB,cationic）and polyethylene glycol（PEG,non-ionic）as surfactants,the copper-manganese/palygorskite catalysts with large specific surface area,controllable morphology,adjustable size,and excellent catalytic activity was prepared by co-precipitation method.And characterize and optimize the catalysts.The results show that the optimal synthesis conditions of copper-manganese/palygorskite catalyst are:co-precipitation pH of 10,reaction temperature of 50℃,aging time of 24 h,stirring speed of 400 r/min,calcination temperature of 500℃,calcination time of 4 h;the copper-manganese/palygorskite catalysts surface-modified by different types of surfactants have different morphologies and structural characteristics.In comparison,when non-ionic PEG is used as the surfactant,its morphology,crystal phase and dispersion are the best;catalysts with different copper-manganese ratios modified by PEG have similar morphology,better dispersion and rod structure of palygorskite.Among them,the copper-manganese/palygorskite catalyst with a copper-manganese molar ratio of 1 forms a CuMn₂O₄ spinel structure phase that is helpful for catalysis,and the T₅₀ and T₉₀ temperatures are much lower than the copper-manganese oxide catalyst;catalysts with different ratios have larger specific surface area and pore size,which effectively solves the problem of small specific surface area of copper manganese oxide catalysts;working conditions such as space velocity and toluene concentration have important effects on the catalytic combustion effect.This paper also studies the stability and catalytic mechanism of copper-manganese composite oxide catalysts.The results show that the copper-manganese oxides and copper-manganese/palygorskite catalysts for the removal of toluene have maintained the removal rate of 98%and 98.5%in 60 hours.The copper-manganese composite catalyst mainly uses copper-manganese as the active component.The continuous adsorption-oxidation-desorption cycle process can effectively and quickly convert toluene into a non-toxic and harmless substance.