Experimental analysis of gas- and particle-phase organic byproducts formed by plasma-induced toluene destruction processes

Non-thermal plasma (NTP) technology has great potential to treat volatile organic compounds (VOCs) at low concentrations and large volumes. In this work, toluene, one of the most stable VOCs, was employed as a model pollutant to study its degradation by double dielectric barrier discharge (DDBD) at ambient temperature and atmospheric pressure. The performance of the DDBD reactor was evaluated in terms of discharge power, removal efficiency, COx selectivity, and byproduct formation. Online and continuous measurements by PTR-TOFMS showed that toluene degradation resulted in the formation of 12 major volatile organic byproducts as well as 7 minor ones with concentrations ranging from ppbv to ppmv. Moreover, the particle size distribution and number concentration of particles formed during toluene degradation were measured using a scanning mobility particle sizer, and the effects of discharge power, initial toluene concentration, gas flow rate and O2 content on particle formation were systematically investigated. The results show that both NTP-induced polymerization and oxidation contribute to aerosol formation, and the total concentration of organic byproducts in the aerosol phase is about 107 cm−3 with diameters in the range of 10 and 100 nm. This pioneered investigation on gas- and particle-phase organic byproducts from toluene degradation by NTP would deepen the understanding of plasma degradation of VOCs and accelerate the practical application of NTP for VOCs treatment.