Effect of Oxygen Content on Toluene Decomposition in Wire-Plate Dielectric Barrier Discharge Reactor Guo Yufang Ph.D candidate South China University of Technology

Introduction 1. Emission of various volatile organic compounds (VOCs) pollutes the air seriously. Dielectric barrier discharges (DBDs) processing has been considered as one of the most hopeful methods to remove VOCs.

Operational parameters: applied voltage gas flow rate gas concentration with/without catalyst 2.In this study, an optimal oxygen content was tested for the removal of toluene from gas streams. Operational parameters: applied voltage gas flow rate gas concentration with/without catalyst

Experimental apparatus   A Dielectric barrier discharge （ DBD) reactor :wire-plate Figure 1. Simplified structure of the wire-plate DBD reactor Figure 1. Simplified structure of the wire-plate DBD reactor

 Experimental setup Figure 2.Schematics of the experimental setup

Results  1.The effect of oxygen concentration in the background gas Figure 3. Dependences of toluene removal Figure 4. Dependences of input power efficiency on oxygen content on oxygen content (Q=500ml/min, 200ppm toluene)

2. The Effect of Gas Flow Rates 2. The Effect of Gas Flow Rates Figure 5. Dependences of toluene removal Figure 6. Dependences of ozone concentration efficiency on gas flow rates on gas flow rates ([O 2 ]=5%, 1300ppm toluene)

3. The Effect of Initial Concentration of Toluene in Background Gas Figure 7a. Dependences of toluene removal efficiency on gas concentration ([O 2 ]=5%, Q=500ml/min) Figure 7b. Dependences of toluene removal efficiency on gas concentration ([O 2 ]=10%, Q=500ml/min)

Figure 7c. Dependences of toluene removal efficiency on gas concentration ([O 2 ]=15%, Q=500ml/min) Figure 8. Dependences of ozone concentration on gas concentration ([O 2 ]=5%, Q=500ml/min)

4. The Effect of Catalyst Figure 9. Removal efficiency of toluene by Figure 10. Ozone concentration with/without the plasma process with/without the catalyst the catalyst (Q=500ml/min, [O 2 ]=5%, 200ppm toluene)

5. byproducts CH 4, C 7 H 16 and C 7 H 12 (no oxygen) benzene,C 4 H 4 O 3 ([O 2 ]=5%) benzene,C 4 H 4 O 3 ([O 2 ]=5%)

Discussion Oxygen plays a very important role in the reaction. e + O 2 ＝ O + O( 1 D) (1) O+ O 2 = O 3 (2) H·+ O = OH· (3) A higher O2 content leads to the generation of more highly reactive O radicals, resulting in a higher removal efficiency. However, O2 has an adverse effect on toluene removal due to its electronegativity. So when the oxygen content is 10%, the removal efficiency is highest. Ozone as the main long-living radical is transported to the catalyst and can take part in heterogeneous oxidation reactions on its surface.

This paper indicated a wire-plate dielectric barrier discharge reactor with catalyst in-situ. It confirmed that dielectric barrier discharge can promote the activation of the catalyst and restrain the formation of ozone to the utmost extent.

Summary An optimal toluene removal is achieved at around 10% of oxygen. The wire-plate dielectric barrier discharge reactor with cobalt oxide catalyst in-situ is effective in destroying toluene and dissociate ozone.

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