SF6 catalytic degradation in a γ-Al2O3 packed bed plasma system: A combined experimental and theoretical study

Effective abatement of the greenhouse gas sulphur hexafluoride (SF6) waste is of great importance for the environment protection. This work investigates the size effect and the surface properties of gamma-Al2O3 pellets on SF6 degradation in a packed bed dielectric barrier discharge (PB-DBD) system. Experimental results show that decreasing the packing size improves the filamentary discharges and promotes the ignition and the maintenance of plasma, enhancing the degradation performance at low input powers. However, too small packing pellets decrease the gas residence time and reduce the degradation efficiency, especially for the input power beyond 80 W. Besides, lowering the packing size promotes the generation of SO2, while reduces the yields of S-O-F products, corresponding to a better degradation. After the discharge, the pellet surface becomes smoother with the appearance of S and F elements. Density functional theory calculations show that SF6 is likely to be adsorbed at the Al-III site over the gamma-Al2O3(110) surface, and it is much more easily to decompose than in the gas phase. The fluorine gaseous products can decompose and stably adsorb on the pellet surface to change the surface element composition. This work provides a better understanding of SF6 degradation in a PB-DBD system.

Automated summary

This study investigates the effects of packing size and surface properties of gamma-Al2O3 pellets on the degradation of SF6 in a packed bed dielectric barrier discharge system. The results show that decreasing packing size improves the degradation performance at low input powers, but decreases efficiency with excessively small packing pellets. Lowering the packing size promotes the generation of SO2 and reduces the yields of S-O-F products. After discharge, the pellet surface becomes smoother with the appearance of S and F elements. SF6 is likely to be adsorbed at the Al-III site over the gamma-Al2O3(110) surface, and it is more easily decomposed than in the gas phase.