Decomposition Of Benzene Using Dielectric Barrier Discharges With Catalysts

The pollution of volatile organic compounds (VOCs) in indoor air has been paid much more attention. Many technologies have been developed for removals of VOCs, in which non-thermal plasma (NTP, also called cold plasmas) technologies are included. However, such NTP technologies still have a problem of high treatment cost. The aim of this study is to develop a hybrid process of plasma and catalysis to reduce VOCs removal cost.The experiment was carried out using a dielectric barrier discharge (DBD) reactor driven by alternative current (AC) voltage power to remove benzene in air. At first, the influence of discharge space volume, air flow rate, output voltage of the AC power supply, energy density, and initial concentration of benzene on benzene removal rate and energy efficiency was investigated, then, similar investigation was performed after loading a catalyst (MnO₂, TiO₂, or actived carbon) downstream of the DBD zone.The results are as follows:1) When use DBD reactor without catalysts, benzene removal rate increases with increasing discharge space volume, output voltage of AC power supply, and energy density, but decreases with increasing air flow rate and initial benzene concentration; The energy efficiency increases with the increase in initial benzene concentration and peaks at an energy density. The energy efficiency is 0.12 mol-C₆H₆/kWh at maximum that is the highest value in all low-concentration VOCs removals using plasma discharges.2) When use DBD reactor with catalysts, benzene removal rate and energy efficiency are improved obviously. The general effects are:(1) benzene removal rate: MnO₂/activated carbon/TiO₂/none=2/1.5/1/1; (2) energy efficiency: MnO₂/activated carbon/TiO₂/none=2.5/2/1/1. The maximum energy efficiency using MnO₂ is 0.035 mol-C₆H₆/kWh. The mechanism of benzene oxidation is possibly (a) benzene is decomposed and oxidized by energized electrons and oxygen atoms in the discharge zone; (b) benzene is further decomposed and oxidized by ozone and oxygen to CO and CO₂ on MnO₂.