Catalytic hydrolysis over alumina was carried out at temperatures between 350 °C and 520 °C and gas hourly space velocity (GHSV) of 6000 h−1. The effects of water vapor concentration, alumina phase, and Zn promoter as well as the reaction mechanism were investigated in detail. The results show that the presence of small amounts of water vapor (0.8%) significantly improves the activity of γ‐Al2O3, while higher water vapor concentration (>2.8%) does not further enhance the decomposition of CHF3. Compared with γ‐Al2O3 and AlOOH, α‐Al2O3 is inactive for the targeted reaction although it is stable under conditions studied (with the presence of HF product). Zn is an efficient promoter for the improvement of activity and stability of alumina catalyst. More attention is paid to the reaction and deactivation mechanism. Based on the experimental results and thermodynamic analysis, a reaction mechanism is proposed which explains the effect of water vapor and deactivation of catalyst reasonably.
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 .
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