Application of plasma catalysis system for CF removal.

Octafluorocyclobutane (CF) with a GWP (global warming potential) of 10,000 times of CO is listed as potent greenhouse gas. Therefore, development of effective control technologies for reducing CF emissions has become an emerging issue to be addressed. In this study, decomposition of CF was investigated via three systems including catalytic hydrolysis, non-thermal plasma, and plasma catalysis, respectively. Decomposition of CF achieved with catalytic hydrolysis reaches the highest efficiency of 20.1%, being obtained with γ-AlO as catalyst in the presence of 10% HO and operating temperature of 800 °C. For plasma-based system, the highest CF conversion obtained with non-thermal plasma is 62% at a voltage of 23 kV. As for the plasma catalysis system, 100% CF conversion efficiency can be achieved at an applied voltage of 22-23 kV. The effects of various parameters such as gas flow rate and CF concentration on plasma-based system show that the plasma catalysis also has better resistivity for the high gas flow rate. The highest energy efficiency of 0.75 g/kWh is obtained for the gas flow rate of 500 mL/min, with the CF conversion of 41%. The highest conversion 89% was achieved with the O content of 0.5%. Addition of Ar improves the performance of plasma-based system. When Ar is controlled at 20%, CF conversions obtained with plasma catalysis reach 100% at applied voltage of 22-23 kV even in the presence of 5% O. The main products of the CF conversion include CO, NO, and COF when O is added into the system. As water vapor is added, HF is also formed. This study has confirmed that combined non-thermal plasma with catalyst system to convert CF is indeed feasible and has good potential for further development.