Study Of The Decomposition Of Gaseous Benzene By Dielectric Barrier Discharge Combined Catalysis

Currently, the non-thermal plasma technology is one of the most promising new technology in the end of treatment, especially with low concentration of volatile organic compounds (VOCs). It has a wide range of application, high efficiency, low power consumption, simple structure, etc.In this paper, benzene was chosen as the target pollutant, using wire tube dielectric barrier discharge reactor, and the bipolar pulse high voltage was set as supplying power, and the single catalyst and two catalysts together were discussed the effect of benzene degradation. The reactor structure (discharge length and discharge gap), the gas parameters (initial concentration and gas flow) and catalyst preparation conditions (loading, carrier diameter, calcinations'temperature and calcinations'time) have been investigated. At the same time, the influences of the degradation characteristics of benzene on the two metal catalysts (Mn and Cu) together have been examined. Finally, the mechanism of benzene decomposition using plasma with catalytic has been studied. The main research results are as follows:1. The reactor structure has a very important effect on the discharge status, and the energy density putting into the discharge region can been changed by adjusting the discharge length and discharge gap. The increases of discharge length can add the injection energy in reactor, resulting in more high-electrons and active particles. Instead, the reduce discharge gap will be benefit to increase field strength, leading to the discharge strength was increased, and the energy density was improved.2. At the same energy density, the increase of the initial gas concentration has an adverse effect on increase of benzene decomposition efficiency. The reduced gas flow can improve the degradation rate of benzene, but inhibit the growth of energy efficiency.3. Adding Mn/γ-AlO3 catalyst in the system, it not only can increase the degradation rate of benzene and carbon oxide selectivity, but also improve energy efficiency. In this research system, the optimal conditions of catalyst preparation are:carrier diameter 3 mm, calcinations'temperature 550℃, calcinations'time 4 h, the best loading of Mn 12%, at this point the role of catalyst has a good results. The degradation rate of benzene up to 90.4%.4. Under the condition of two metal catalysts (12%Mn/γ-Al2O3 and 5%Cu/y-Al2O3) co-exist, the catalyst in series has the most significant effect, up to 84.1%. And the order via catalyst is first flowing through the catalyst of Mn/γ-Al2O3, after Cu/γ-Al2O3. The degradation characteristics of benzene improve with a increase of Cu loading. The best Cu loading is 12%, then the composition efficiency of benzene is 92.7% and carbon oxide selectivity is 97.4%.5. When discussing the mechanism of degradation benzene in system of combining plasma and catalyst, it found that two catalysts have a different effect on removal benzene. Mn catalyst degrades directly benzene molecule mainly using decomposition O3, and Cu catalyst has a significant effect on the further oxidation of intermediate product and CO into CO2.