Integration of plasma with catalyst for removing cf₄ from gas streams

Removal of CF₄ was evaluated with three systems including catalytic hydrolysis, plasma-alone, and plasma catalysis. CF₄ conversion achieved with catalytic hydrolysis using γ-Al₂O₃ as catalyst reaches 80.1% when the operating parameters are controlled at T = 800 ℃, gas hour space velocity (GHSV) = 6000 hr⁻¹, inlet CF₄ = 300 ppm, and H₂O_(g) content = 10%, respectively. The main products of CF₄ conversion via catalytic hydrolysis are CO₂ and HF. On the other hand, plasma-alone system reveals 50% CF₄ conversion at 12 kV (gas flow rate = 100 mL min⁻¹, GHSV = 6000 hr⁻¹, inlet CF₄ = 300 ppm, and frequency = 18.5 kHz). For the plasma catalysis, good conversions of CF₄ are obtained when γ-Al₂O₃ is applied as a catalyst. For instance, 100% conversion efficiency of CF₄ can be achieved with the applied voltage of 12 kV. Moreover, the results indicate that plasma catalysis can remove more CF₄ if compared with plasma-alone at the same level of energy consumption. When O₂ is added into the system, the main products of CF₄ conversion in plasma system include NO₂, N₂O, CO, CO₂, and COF₂. This study has confirmed that combined nonthermal plasma with appropriate catalyst is effective in converting CF₄ and this system has good potential for further development.