(677f) Selective Adsorption of Chlorofluorocarbons(CFC) and Hydrochlorofluorocarbons(HCFC) in Hydrofluorocarbon’s (HFC) Using Adsorbent Supported Metal Oxide.

Hydrofluorocarbons (HFC) are used in a variety of applications such as blowing agents, refrigerants and plasma etching gases for the semiconductor industry and are often commercially manufactured from fluorination of chlorofluorocarbons (CFC) or hydrochlorofluorocarbons (HCFC). As a result, these products may contain undesired impurities which may be toxic, have high global warming or ozone depletion potential, as well as impact the end market process use of the gas. Some of these impurities form azeotropic combinations with the matrix gas leading to difficulties in separation using conventional distillation. A novel purification method to selectively remove these undesired impurities (CFC’s and HCFC’s) from hydrofluorocarbons using metal oxide based adsorption bed along with specific pre-treatment processes will be discussed. Conventionally, these adsorbent beds have been employed to completely remove or scrub halocarbons from various gas streams for environmental purposes. In this application, we are taking advantage of the relatively higher affinity of chlorine containing compounds towards metals and metal oxides compared to the fluorocarbons for selective adsorption thereby producing ultrahigh purity electronic gases. Examples will be presented including 245fa (1,1,1,3,3-Pentafluoropropane) purification utilizing a metal oxide adsorption bed where some key CFC/HCFC impurities including 1,1,2 trichlorotrifluoroethane and 2,2 dichloro-1,1,1trifluoroethane were observed to be reduced from 284 ppm and 16 ppm to << 1ppm respectively when measured using GC/MS/TCD.