Destruction of Freons by the Use of High-Voltage Glow Plasmas

The decomposition of two different Freon species, Freon 21 (CHFCl 2 ) and Freon 142-B (CF 2 ClCH 3 ), was carried out using a high-voltage glow discharge plasma. The plasma is produced in a tubular reactor consisting of an inner iron electrode and an outer electrode being either aluminum or copper, a glass tube between the electrodes serves as a dielectric. The reaction gases, 0.5% Freon in helium and 5% oxygen in helium (moisture added), are mixed on line. The conversion measured by a gas chromatograph as the disappearance of the Freon species is very high for both species. For Freon 21, the conversion ranges from 75% up to 100% in the input voltage regime between 1.60 and 5.44 kV depending on the mixture. In the case of Freon 142 B, higher voltages are needed to achieve similar conversions. The input voltage of 3.50 kV yields 70% conversion, 3.88 kV yields 77% conversion, and 5.44 kV gives 100%. The conversion of Freon 21 drops with increasing flow rate and decreases from 88% at 15 mL/min to 78% at 40 mL/min and to 47% at 100 mL/min. A more drastic decrease is seen with respect to CO 2 production, which decreases by 30% when the flow rate is changed from 20 to 40 mL/min and by 42% if changed to 60 mL/min. Oxygen increases CO 2 production via breakdown of Freon by 90%. Further addition of water increases CO 2 production by another 25% compared to the reaction with oxygen. Carbon dioxide is the main carbon oxide produced at a CO/CO 2 ratio of 0.05 to 0.07. Further reaction products are hydrogen fluoride and chlorine. Furthermore, mass spectroscopic and optical emission studies were carried out to obtain insight on the reaction mechanism.