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Real-time monitoring and quantification of organic by-products and mechanism study of acetone decomposition in a dielectric barrier discharge reactor

Li, Xueshuang, Guo, Teng, Peng, Zhen, Xu, Li, Dong, Junguo, Cheng, Ping, Zhou, Zhen
Environmental science and pollution research international 2019 v.26 no.7 pp. 6773-6781
acetaldehyde, acetic acid, acetone, byproducts, carbon dioxide, formaldehyde, formic acid, free radicals, hydroxyl radicals, mass spectrometry, methanol, monitoring, oxygen, volatile organic compounds
Non-thermal plasma (NTP) degradation of low-concentration acetone was investigated in a cylindrical dielectric barrier discharge reactor. The effects of oxygen content and flow rate on the removal efficiency at various discharge powers were examined in real-time. The acetone removal efficiency decreases drastically and then remains stable or increases gradually as the O₂ content increases from 0 to 25%, and further to 50%. The organic by-products were characterized and quantified using a real-time proton transfer reaction time-of-flight mass spectrometry (PTR-TOF-MS) instrument. The observed organic compounds, with concentrations about ppbv/ppmv by volume, were mainly formaldehyde, methanol, ketene, acetaldehyde, formic acid, acetone, and acetic acid. The discharge power was a critical factor affecting the concentration of the organic by-products and the selectivity toward CO₂. The mechanism study based on the by-product monitor in real-time showed that acetone firstly fragments into methyl radicals, acetyl radicals, and H; then, the methyl and acetyl radicals are oxidized by O or OH radicals into acetaldehyde, methanol, and other compounds. It seems that acetaldehyde could be an intermediate in acetone decomposition. Firstly, most of the acetone molecules were decomposed into acetaldehyde molecules; then, the acetaldehyde molecules continued to be decomposed and oxidized into other compounds, such as acetic acid and formaldehyde. These investigations not only proposed a detail decomposition mechanism for acetone in dielectric barrier discharge reactor, but also provided a potential way to analyze and evaluate the practicability of NTP removal of VOCs.