Production of CaF₂ by the Destructive Adsorption of Trifluoromethane and a Binary Mixture of Trifluoromethane/ Chlorodifluoromethane with CaO Powder under Air-Flow

Abstract

The destructive adsorption of trifluoromethane (HFC-23) and chlorodifluoromethane (HCFC-22) with CaO powder under air-flow was investigated. CaO pretreated at 873 K exhibited a high conversion potential (100% HFC-23 conversion over 2.5 h) at 873 K under HFC-23 (1 mol%)/air-flow. In the case of 100% HFC-23 conversion, the main gaseous products were CO₂, H₂O, and CO, and no fluorinated product was formed. On the other hand, CaO powder showed moderate potential for the destructive adsorption of HCFC-22 resulting in the production of CO, CO₂, H₂O, CaClF, and CaF₂. For the destructive adsorption of the HFC-23/HCFC-22 binary mixture, it was found that the presence of HCFC-22 retards the reaction of the HFC-23 molecule with CaCO₃, which is formed during the reaction. It was concluded from the results that high purity CaF₂ could be produced when only HFC-23 or the HFC-23/HCFC-22 (=9 : 1) binary mixture was fed into a CaO powder bed at 773 K under air-flow.