Pyrolysis of Trifluoromethane over Activated Carbon: Role of the Surface Oxygen Groups

Abstract

The pyrolysis of CHF 3 and CHClF 2 over activated carbons was investigated at 823 K, GHSV of 1820 h -1 and pressure of 1 bar. To elucidate the mechanism, activated carbons were treated in H 2 at 1123 K, HNO 3 solution at 363 K, N 2 at 873 K or supported with 4 wt% poly(acrylic acid sodium salt), respectively. The results confirm that following different treatments, the concentration of surface oxygen groups on activated carbons varies dramatically. These surface groups play important roles in the decomposition of CHF 3 and the product profiles. It is suggested that carboxylic groups are responsible for the formation of CF 3 and ultimately the product C 2 F 6 which results from the coupling of CF 3 , while the interaction between CHF 3 and hydroxyl or lactonic groups leads to the total destruction of CHF 3 and production of CO and CO 2 . Pyrolysis of CHClF 2 over activated carbon confirms that surface oxygen groups have no noticeable influence on the reactions of CF 2 . By contrast, a pure carbon surface is responsible for the disproportionation of CF 2 and formation of CF 3 .

Promotion of O2 on the co‐pyrolysis of CHF3 and CH4 for VDF synthesis

“…Recently, technologies such as catalytic decomposition and thermal pyrolysis have been proposed for the destruction of CHF 3 . Alternatively, it was discovered that CCl 2 F 2 , CBrClF 2 , CHClF 2 , and CHF 3 can be converted into unsaturated HFC, CH 2 =CF 2 via reaction with CH 4 or CH 3 Br …”