Chlorofluorocarbons recycling

Cmde HCl recovered from production of chlorofluorocarbons by hydrofluorination of chlorocarbons contains unique impurities which can be removed by processes described in References 53—62. CICN—CI2 mixtures generated by reaction of hydrogen cyanide and CI2 during the synthesis of (CICN) can be removed from the by-product HCl, by fractional distillation and recycling (see Cyanides) (59). 

Cements, polyester, 30 CFCs. See Chlorofluorocarbons (CFCs) Chain conformation, 54 Chain extenders, 213-214 structure of, 219 Chain extension, 216 Chain-growth polymerizations, 4 Char formation, 421, 423 Chelated phosphine ligands, 488 Chemical recycling, 208 Chemical structure... 

Apart from these synthetically impractical examples of hydrolysis of chloro-fluorocarbons, there are useful applications converting some chlorofluorocarbons to fluonnated carboxylic acids. As an alternative to the use of the highly corrosive fuming sulfuric acid, normally used in batch processes, a continuous hydrolytic process for converting 1,1,1-trichlorotrifluoroethane (CFC-113a), available by isomerization of CFC-113 [44], to trifluoroacetic acid has been developed [45] (equation 45). It uses metal chloride catalysts deposited on high-surface-area supports Unreacted CFC-113a can be recycled. 

A major area of concern in chemical processes is the use of volatile organic compounds as solvents for reactions. The solvent is not generally consumed in the reaction, but there are unavoidable releases to the atmosphere even in the most carefully controlled processes. Further, the solvent may be toxic or may decompose at least to some extent during reaction, thus creating wastes. The use of supercritical fluids ("Chemistry at Work" box. Section 11.4) represents a way to replace the conventional solvent by CO2, a nontoxic gas already present in the atmosphere that can be recycled. Du Pont chemical company, for example, has invested in a production facility to make polytetrafluoroethylene, — [CF2Cp2] — (Teflon M) and copolymers with tetrafluoroethylene in liquid or supercritical CO2. In this case the CO2 replaces chlorofluorocarbon solvents, which, aside from their costs, have harmful effects on Earth s ozone layer (Section 18.3). 

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