Decomposition Degree of Chlorofluorocarbon (CFC) and CFC Replacements during Recovery with Surface-Modified Activated Carbon

Abstract

The recovery efficiency of 1,1,2-trichloro-1,2,2-trifluoroethane (CFC113) and three CFC replacements (1,1-dichloro-1-fluoro- ethane, HCFC141b; 1,3-dichloro-1,1,2,2,3-pentafluoro-propane, HCFC225cb; and 2,2,3,3,3-pentafluoro-1-propanol, 5FP) were investigated on the basis of their degree of decomposition and adsorption isotherms. We prepared activated carbons with various surface polarities to elucidate the recovery efficiency, the amount adsorbed, and the degree of decomposition. A correlation between the physicochemical properties of the activated carbon surface and the amount of CFC or CFC replacements adsorbed was not observed. The amount of CFC113 adsorbed onto untreated activated carbon was the largest of all. That of HCFC225cb adsorbed onto activated carbon treated with hydrogen gas was larger than that adsorbed onto untreated activated carbon and activated carbon treated with 6Nnitric acid. The amount of 5FP and HCFC141b adsorbed on the various activated carbons was not substantial. The degree of decomposition of CFC replacements using the untreated activated carbon except for HCFC225cb was the largest of all. In the case without the activated carbon, that of CFC and the CFC replacements increased in the order 5FP, CFC113 or HCFC225cb, and HCFC141b. These results indicated that the stability of CFC and CFC replacements molecules was controlled by the number of carbon-fluoride groups and/or hydrogen atoms. It is concluded that the recovery of CFC replacements was possible using the surface-modified activated carbons rather than the untreated activated carbon. The degree of decomposition of the CFC replacements during recovery using the activated carbon depends on the relationship between the adsorption site of the surface of the activated carbon and the polarity, hydrophilic site, or hydrophobic site of the CFC replacement molecule. It is assumed that the recovery of CFC replacements using HT-AC decreased the amount of hydrofluoric acid produced.