Evaluation of the alkaline hydrolysis of HCFC-22 (CHClF2) in a closed-circulation reactor

Abstract We evaluated the kinetics of alkaline hydrolysis of HCFC-22 (CHClF 2 ) in hot water, which is a potential method for destruction of this hydrochlorofluorocarbon. Specifically, a CHClF 2 –air mixture was exposed to different concentrations of aqueous NaOH solution in a closed-circulation reactor, typically at 353 K, and the time course of the gaseous CHClF 2 partial pressure was monitored. The decrease in the partial pressure of gaseous CHClF 2 exhibited first-order kinetics (rate constant k 1 ). The main reaction products were F − , Cl − , and HCOO − ; a minor product was (COO − ) 2 . The k 1 values obtained when the aqueous NaOH was stirred at high speeds indicated that the rate constant for aqueous reaction of CHClF 2 with OH − ( k OH − ) was greater than 0.26 M −1  s −1 at 353 K. The k 1 values increased with increasing OH − concentration in the range from 0 to 3.5 × 10 −2  M; however, at OH − concentrations greater than 3.5 × 10 −2  M, the k 1 value decreased. According to these results, combined with the large, substantiated value of k OH − , it is expected that alkaline hydrolysis of CHClF 2 in aqueous NaOH solution at concentrations of some 10 −2  M at 353 K would proceed within several minutes if the gas-to-water mass transfer of CHClF 2 proceeds efficiently.