Toluene decomposition by non-thermal plasma assisted CoOx - γ-Al2O3: The relative contributions of specific energy input of plasma, Co3+ and oxygen vacancy

Abstract

Cobalt oxide (CoO_x) is a common catalyst for plasma catalytic elimination of volatile organic compounds (VOCs). However, the catalytic mechanism of CoO_x under radiation of plasma is still unclear, such as how the relative importance of the intrinsic structure of the catalyst (e.g., Co³⁺ and oxygen vacancy) and the specific energy input (SEI) of the plasma for toluene decomposition performance. CoO_x - γ-Al₂O₃ catalysts were prepared and evaluated by toluene decomposition performance. Changing the calcination temperature of the catalyst altered the content of Co³⁺ and oxygen vacancies in CoO_x, resulting in different catalytic performance. The results of the artificial neural network (ANN) models presented that the relative importance of three reaction parameters (SEI, Co³⁺, and oxygen vacancy) on the mineralization rate and CO₂ selectivity were as follows: SEI > oxygen vacancy > Co³⁺ , and SEI > Co³⁺ > oxygen vacancy, respectively. Oxygen vacancy is essential for mineralization rate, and CO₂ selectivity is more dependent on Co³⁺ content. Furthermore, a possible reaction mechanism of toluene decomposition was proposed according to the analysis results of in-situ DRIFTS and PTR-TOF-MS. This work provides new ideas for the rational design of CoO_x catalysts in plasma catalytic systems.

Keywords: Toluene Plasma catalysis Oxygen vacancy Co(3+) cations Ozone decomposition.