Preparation Of Copper Mantianese Catalyst In Microreactor For Catalytic Combustion Of VOCs

Cu-Mn catalysts,with high catalytic activity in the oxidation of atmospheric pollutants,have extensive application prospects in the fields of catalytic combustion of volatile organic compounds,selective catalytic reduction of NOx and CO oxidation.Co-precipitation is one of the most common methods for the preparation of Cu-Mn catalysts.The microreactors are convenient to study the Cu-Mn catalysts prepared by co-precipitation due to the unique flow and mixing.In this paper,Caterpillar microreactor was employed to explore the structural evolution of Cu-Mn catalysts and the effect of aging on this process.Further,relationship between structure and catalytic performance of Cu-Mn catalysts was discussed.Based on the research of the Cu-Zn system,it was found that the performance of Cu-Mn catalysts prepared by calcination-direct-derived from co-precipitates in microreactor is better than the catalysts obtained by conventional route.In order to figure out the mechanism behind,the structure and morphology of the precipitates were investigated by XRD,FT-IR and TG-MS and the pore structure and surface element state of catalysts were comprehensively analyzed by Raman spectroscopy,SEM,N2-BET,XPS and other methods.Further,the relationship between these structures and catalytic performance was studied,and on this basis,the influence of Cu element on the structure and evolution process of precipitates in calcination-direct-derived route was studied.The conclusions are as followsThe structure of Cu-Mn precipitates changes rapidly in the early stage of aging,and within 2 minutes,it changes from the amorphous hydroxyl-carbonate to the crystalline carbonate.Cu and Mn elements separate during this process,resulting in the decrease of catalytic activity.In the subsequent process of aging,Cu rhodochrosite will be formed by the incorporating of Cu element into MnCO3,which enhances the Cu-Mn interaction and ilcreases the content of surface Mn3+,Cu+ and lattice oxygen in catalysts,resulting in the increase of catalytic activity.During the preparation process of calcination-direct-derived route in microreactor,the carbonate in Mn precipitates transforms to hydroxyl-carbonate in Cu,Mn precipitates with the increase of Cu content,which significantly reduces the degree of crystallization in precipitates.The specific surface area,content of surface Mn3+ and Olatt,Cu-Mn interaction and pore volume of catalysts are affected consequently,resulting in that the catalytic activity for toluene reaches the highest when the Cu content is 0.2-0.3.Compared with the stirred tank reactor in the literature,the aging of precipitates during the reaction process can be avoided in microreactor,thus the sharp decline of catalytic activity during the early stage of aging disappears.It was found that in the catalytic oxidation of toluene,the reaction rate of Cu-Mn catalyst prepared from the precipitate in microreactor can be 429.48 mmol/g h at 190℃ while the best activity of the same type catalysts in the literature is 117.60 mmol/g h.