Catalytic conversion and DFT analysis of post DDBD-catalysis system for degradation of toluene, ethyl acetate and acetone with different metal-oxides catalysts

A series of multiphase metal-oxide catalysts (MnOx/γ-Al2O3, CuOx/γ-Al2O3, FeOx/γ-Al2O3, CeOx/γ-Al2O3 and LaOx/γ-Al2O3) were prepared for plasma-catalyst degradation of multicomponent volatile organic compounds (VOCs, such as toluene, acetone and ethyl acetate). The results reveal that the degradation efficiency (DE) of acetone, toluene and ethyl acetate in the DDBD system can be arranged as follows: Mn2O3/γ-Al2O3> Fe2O3/γ-Al2O3> CuO/γ-Al2O3> CeO2/γ-Al2O3> La2O3/γ-Al2O3> γ-Al2O3, and the highest DE (49.5% for acetone, 93.3% for toluene and 79.8% for ethyl acetate) is obtained in Mn2O3/γ-Al2O3+double dielectric barrier discharge (DDBD) system at specific input energy (SIE) of 700 J/L. Compared with the other catalysts, Mn2O3/γ-Al2O3 also exhibits the most significant inhibitory effect on the production of ozone (O3). On the other hand, CeO2/γ-Al2O3 and La2O3/γ-Al2O3 catalysts display different catalytic selectivity. Both catalysts can slightly raise the DE of VOCs and remarkably facilitate VOCs' mineralization. The carbon balance (CB) is increased by 30.2% and 38.8%, and the CO2 selectivity (SCO2) is raised by 70.5% and 11.9% in the CeO2/γ-Al2O3+DDBD system and La2O3/γ-Al2O3+DDBD system at SIE of 700 J/L, respectively. To further understand the catalytic effect of the catalysts, the adsorption of O3 on different catalysts was simulated by a DFT model. According to the results of the DFT model, it is found that the adsorption energy of other metal oxides seems to be used as a reference for catalytic effect to a certain extent except CeO2. The higher the absolute values of adsorption energy, the higher the improvement of VOCs degradation efficiency by catalyst.