Study On The Performance Of Manganese-based Composite Oxide And Low-temperature Plasma Synergistic Catalytic Oxidation Of Toluene

Atmospheric volatile organic compounds（VOCs）,volatile substances mainly carbon based compounds,are the most important gaseous pollutants in the refining industry and have become a major constraint in the direction of green chemical development in China.Countries have done a lot of work in controlling VOCs emission,but still cannot reduce the VOCs management problem from economic aspect.The important task now is to find methods that can eliminate VOCs quickly at low temperatures and without secondary pollution.Low-temperature plasma co-catalysis technology has received wide attention in VOCs treatment technology because of its advantages such as low start-up temperature,high selectivity and non-thermodynamic equilibrium properties.In this paper,cobalt-and cerium-modified manganese-based composite oxides were synthesized by sol-gel method and combined with a low-temperature plasma system to investigate the performance of degrading toluene in volatile organic compounds（VOCs）,and the effects of Ag doping and input power on the catalytic performance were also investigated.The composition,structure and redox performance of the catalysts were characterized by XRD,H₂-TPR,O₂-TPD and XPS to analyze the conformational relationship between the structure of manganese-based composite oxides and the synergistic catalytic performance.The conclusions are as follows:（1）In the Mn_1-xCo_xO_2-δcatalyst,the co-catalytic activity increased and then decreased with the increase of Co doping.The catalytic performance of the Mn_0.7Co_0.3O_2-δcatalyst was the best at room temperature with the input power of 6 W.The conversion and CO₂selectivity of toluene were 58.49%and 64.06%,respectively,which were increased by 52.89%and 30.73%compared with the blank experiment.The characterization results demonstrated that the doped Co formed strong interactions with Mn,which led to the formation of more defect sites in the catalyst,effectively improving the oxygen mobility and lattice oxygen activation energy of the catalyst and enhancing the catalytic performance.（2）In the Mn_1-yCe_yO_2-δcatalyst,the higher Ce doping（y=0.7-0.9）catalysts showed obvious synergistic effect,but when y<0.5,the composite oxide formed a reduced synergistic catalytic effect with the low-temperature plasma.At an input power of 6 W,the Mn_0.3Ce_0.7O_2-δcatalyst showed the best activity with 69.23%conversion of toluene,but the CO₂selectivity was less enhanced,probably because the short residence time of the active oxygen species in the plasma on the catalyst surface was limited by the survival lifetime of the active oxygen in the plasma,so it did not improve the CO₂selectivity.The characterization results demonstrated that the substitution of Ce ions by Mn ions caused the contraction of Ce O₂lattice and formed Mn-Ce-O solid solution,and formed defects in Ce O₂lattice to generate oxygen vacancies,and the strong interaction between Ce O₂and Mn₂O₃increased the mobility of lattice oxygen in the solid solution,which improved the catalytic performance.（3）The doping of metal Ag in manganese-based composite oxides can effectively improve the catalytic synergistic effect.toluene conversion monotonically increased with increasing Ag doping below 14%,but the synergistic catalytic effect decreased above 14%At room temperature,at a low input power of 6 W,the 14%Ag-Mn_0.3Ce_0.7O_2-δcatalyst showed the best low-temperature co-catalytic activity and good stability compared with other catalysts,with93.58%toluene conversion,and the catalytic activity increased with increasing input power.