Effect of ZnO/γ-Al₂O₃ Catalyst Packing on the Degradation of SF₆ in a Dual-Stage DBD Plasma Reactor

Sulfur hexafluoride (SF₆) gas is widely used in the electric power industry as an excellent insulating gas. However, SF₆ is a potent greenhouse gas, and its degradation is an ideal method for emission reduction. In the field of SF₆ degradation, due to the harsh decomposition conditions, it is often difficult to achieve both a high degradation rate and favorable product distribution. To address this issue, a double-stage dielectric barrier discharge (DBD) series degradation experimental platform for SF₆ gas was designed in this study. A ZnO catalyst was packed in the first-stage reactor to improve the SF₆ degradation rate, while a γ-Al₂O₃ catalyst was packed in the second-stage reactor to optimize the product distribution. Additionally, the selectivity of SF₆ degradation products was regulated by externally adding H₂O. Experimental results showed that under an input power of 100 W, the SF₆ degradation rate reached 100% in the ZnO/γ-Al₂O₃ double-stage packed system, achieving complete degradation of SF₆. As the input power increased, the energy yield showed a gradually decreasing trend. The addition of an appropriate concentration of H₂O effectively improved both the degradation rate and energy yield of SF₆, with the maximum energy yields of the two-stage reactors reaching 23.9 and 17.9 g/kWh, respectively. With regard to decomposition products, the types of SF₆ decomposition products in both reactors remained unchanged, including SO₂, SO₂F₂, SOF₂, and SOF₄. The main product in the first-stage reactor was SO₂F₂, whereas in the second-stage reactor, SO₂ was predominant. The addition of H₂O also effectively increased the yield of SO₂ while suppressing the formation of SO₂F₂, which is more difficult to treat. This study provides experimental support for SF₆ exhaust gas degradation and offers a research direction for industrial applications.