Synthesis Of Carbon Confined Catalysts And Their Performance On Acetone Catalytic Oxidation

The rapid development of urbanization and industrialization leads to the emission of a large number of Volatile Organic Compounds（VOCs）.As a precursor of PM_2.5 and ozone generation,VOCs bring great threat to the atmospheric environment;And in the long-term environment containing VOCs,will cause damage to the central nervous system,affecting people’s health.Among VOCs removal technology,the method of catalytic oxidation is efficient and environmentally friendly.Its core lies in the design of catalyst.The carbon material is widely available,with a high specific surface area and adjustable pore size,which is a very potential catalyst carrier.In this study,acetone was used as the probe pollutant,cerium and manganese were selected as the main active components with wide resources and good reducibility.By using the limiting effect of carbon carriers with a high specific area,a catalyst was designed to fully expose the active site with high catalytic activity and stability.Combined with a variety of characterization techniques to analyze the relationship between catalyst structure and performance,providing theoretical guidance and experimental support for the development of low-temperature and high-efficiency catalysts.The main research results are as follows:（1）Because of the carbon carrier has low thermal stability,they tend to burn or even an explosion under the condition of high-temperature oxygen.To solve the above problems,in this paper,boron was directly doped into mesoporous carbon to improve its thermal stability,and cerium copper catalyst was supported by the impregnation method.Explore the optimal doping amount of cerium element,optical doping element,and Ce/Cu mole ratio.The results show that boron doping increases the initial oxidation temperature of mesoporous carbon by about 120℃.In the catalytic oxidation reaction of acetone,the best loading of Ce was 40wt%.Among many doped elements,Cu doping showed the best-promoting effect,the optimal molar ratio of Ce/Cu was 4.The results showed that the T₉₀ of catalyst prepared under this condition was 189℃,and T₉₀decreased by 8℃compared with the catalyst without Cu doping,and the activity was improved.The study found that the improvement of catalytic activity of the catalyst was mainly derived from its smaller grain size,more amount of Ce³⁺and adsorbed oxygen species,and better low-temperature reducibility.（2）To fundamentally solve the problem of poor thermal stability of carbon carriers,this paper proposes a strategy of“in situ carbon template limiting”.This strategy takes advantage of the carbon being included in the precursor of manganese oxide.Firstly,the carbon carrier is in situ loaded and limited to the active species of manganese oxide by calcination in the nitrogen atmosphere.Then,the calcination atmosphere is switched to air to remove the carbon template.Finally,the active component of uniformly dispersed manganese oxides with a small grain size was obtained.The results show that the most suitable amount of citric acid in manganese oxide catalyst is 2.4 times that of metal salt,and the optimum temperature of air calcination is 300℃.The catalyst synthesized under these conditions can convert 90%acetone at 178℃,far lower than the commercial Mn₃O₄（Mn₃O₄-C）catalyst（240℃）.The study found that the excellent catalytic performance mainly resulted from the catalyst’s larger specific surface area,smaller grain size,lower temperature reduction,and better lattice oxygen mobility.（3）A cerium-doped manganese-cerium composite oxide catalyst was synthesized by“in-situ carbon template limiting strategy”and the influence of cerium on the catalytic performance was investigated.The data showed that the catalyst with the molar ratio of Ce to Cu is 4 had the best performance,its T₉₀ was 172℃,6℃lower than that of MnO_x.Furthermore,the catalyst possessed excellent long-term stability,water,and sulfur resistance.It was found that the addition of Ce was beneficial to the decrease of particle size,the weaken of reduction temperature,and the increase of lattice oxygen mobility.This is because an electron transfer occurs between Mn and Ce after the addition of cerium,promoted the high Mn ions of redox and the transfer of Mn-O bond,the existing synergy accelerated the oxidation reaction of acetone.Finally,the reaction mechanism of acetone on the catalyst with the best activity was deduced.