Toluene degradation in air/H2O DBD plasma: A reaction mechanism investigation based on detailed kinetic modeling and emission spectrum analysis

• Published in: Journal of hazardous materials Vol. 448; p. 130894
• Main Authors: Yue, Wenjing, Lei, Wentao, Dong, Yongheng, Shi, Chengjing, Lu, Qiancheng, Cui, Xin, Wang, Xinyu, Chen, Yumin, Zhang, Junying
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15.04.2023
• Subjects: Emission spectroscopy; Mechanism investigation, Kinetic modeling; Non-thermal plasma; Toluene degradation; Non-thermal plasma; Toluene degradation; Mechanism investigation, Kinetic modeling; Emission spectroscopy
• ISSN: 0304-3894; 1873-3336
• DOI: 10.1016/j.jhazmat.2023.130894

Non-thermal plasma (NTP) is emerging as an attractive method for decomposing volatile organic compounds (VOCs). In this paper, to study toluene degradation mechanism in air/H2O dielectric barrier discharge (DBD) plasma, optical emission spectrometry (OES) was employed to in-situ monitor active species in plasma, with the permanent degradation products being detected by on-line mass spectrometry under various operations. A detailed kinetic model of NTP with incorporation of non-constant electron filed and thermal effects has also been established. A toluene degradation efficiency > 82% could be achieved at P = 115 W, Cin, toluene = 1000 ppm. The relative spectrum intensity of excited OH, O, H and N2 (A3Σ+u) increased with increase of discharge power and was decreased at higher gas flowrates. Toluene degradation was mainly induced by oxidation of OH and O at afterglow stage, while part of toluene was decomposed by attack of electrons and reactive particles N2 (A3Σ+u) in discharge stage. A toluene degradation pathway has been proposed as: toluene→benzyl→benzaldehyde→benzene→phenoxy→cyclopentadiene→polycarbenes/alkynol→CO2/H2O. Benzoquinone, benzaldehyde, cyclopentadiene and cyclopentadienyl are supposed to be important intermediates for the ring-opening of toluene. Clarification of toluene degradation behaviors at discharge and afterglowing stage could provide new insights for plasma-catalytic process in future. [Display omitted] •Comprehensive explorations on plasma-based toluene degradation mechanism.•Plasma kinetic model with incorporation of non-constant electric field and thermal effects.•Detailed toluene degradation pathways in pulsed air/H2O DBD plasma.•A toluene degradation efficiency > 82% was achieved at P = 115 W without catalyst.