Decomposition of Adsorbed Xylene on Adsorbent Using Nonthermal Plasma and Gas Circulation

The xylene decomposition system which consists of adsorption process by adsorbents and adsorbed xylene decomposition process using nonthermal plasma with gas circulation is investigated. Two types of hydrophobic zeolite pellets are used as adsorbent. The ac 60 Hz and 20 kHz high voltage power supplies are employed for nonthermal plasma generation. After p-xylene or xylene mixture which consists of o-, m- and p-xylene is adsorbed by adsorbent for 130 min, nonthermal plasma is generated in order to decompose adsorbed xylene with gas circulation. For p-xylene, the conversion ratios of adsorbed xylene to CO and CO2 (eta(COx)) reach 43% for ac 60 Hz plasma and 70% for ac 20 kHz plasma during 60 min treatment and then the energy efficiencies (E-d) are 0.26 and 0.75 g/kWh, respectively. As for xylene mixture, eta(COx) of 69 and 48% are obtained by ac 60 Hz plasma for 90 min and ac 20 kHz plasma for 75 min, and E-d are 0.27 and 0.43 g/kWh. Ac 20 kHz plasma is better energy efficiency than that of ac 60 Hz plasma, however, ac 20 kHz plasma is unstable and generates NOx as byproduct. From FTIR analysis of exhaust gas after treatment, it is clarified that N2O is generated by ac 60 Hz plasma.