Solubility and hydrolysis of HCFC‐22 (CHF₂Cl): Upward revision of rate constants for aqueous reactions of CHF₂Cl with OH⁻ at elevated temperature

Abstract

Henry's law constants of CHF2Cl in water at temperature T in K, KH(T) in M atm−1, were determined to be ln(KH(T))=−(11.1±1.5)+((2290±500)/T) at 313–363 K by means of a phase ratio variation headspace method. The temperature‐dependent rate constants for aqueous reactions of CHF2Cl with OH−, k(T) in M−1 s−1, were also determined to be 3.7×1013exp(−(11, 200/T)) at 313–353 K, by considering the gas–water equilibrium, the aqueous reaction at room temperature, and liquid‐phase diffusion control. The liquid‐phase diffusion control was approximated with a one‐dimensional diffusion first‐order irreversible chemical reaction model. The k(T) value we determined is 10 times (at 353 K) or 3 times (at 313 K) as large as the value reported (R. C. Downing, Fluorocarbon Refrigerants Handbook, Prentice Hall: Englewood Cliffs, NJ, 1988). This upward revision of k(T) indicates that the removal efficiency of CHF2Cl directly through the hydrolysis (CHF2Cl + OH−) is higher than previously expected at temperatures, such as 353 K, relevant to wet flue gas cleaning systems for ozone‐destruction substance‐destruction facilities. © 2011 Wiley Periodicals, Inc. Int J Chem Kinet 43: 639–647, 2011

Determination of Rate Constants for Aqueous Reactions of HCFC‐123 and HCFC‐225ca with OH− Along with Henry's Law Constants of Several HCFCs

“…In a previous study , the author and coworkers found that the rate constants for HCFC‐22 (CHClF 2 ) hydrolysis with OH − () at 353 K were 10 times larger than what had been reported before and thus concluded that alkaline wet scrubbers could be used to remove residual CHClF 2 in the wet flue gas cleaning system of ODS destruction facilities. We further noted that hydrolysis is a potential technique for destruction of CHClF 2 .…”

“…Henry's law constants of HCFCs were determined by the PRV‐HS method in a way similar to that used in the previous study . The determination was carried out with an automatic headspace sampler (HP7694; Agilent Technologies, Palo Alto, CA) connected to a gas chromatograph mass spectrometer (GC‐MS; Agilent GC6890N with 5973inert; Agilent Technologies, Palo Alto, CA).…”

“…To evaluate the hydrolysis of the HCFCs, changes in headspace partial pressures were examined as a function of headspace time duration over a 1 M NaOH aqueous solution at 353 K. As described in the Results and Discussion section, only two HCFCs, CF 3 CF 2 CHCl 2 and CF 3 CHCl 2 , exhibited a decrease in headspace partial pressure. For these two HCFCs, values were determined at 313–353 K at intervals of 10 K in a way similar to that applied in the previous study . The determination of values was carried out by means of an automatic headspace sampler connected to a gas chromatograph/mass spectrometer.…”

“…In the previous study, the author and coworkers made an additional correction of Eq. to account for aqueous‐phase diffusion.…”

“…In this study, the author examined the hydrolysis of the following six commercial HCFCs: HCFC‐141b (CH 3 CCl 2 F), HCFC‐142b (CH 3 CClF 2 ), HCFC‐123 (CF 3 CHCl 2 ), HCFC‐124 (CF 3 CHClF), HCFC‐225ca (CF 3 CF 2 CHCl 2 ), and HCFC‐225cb (CClF 2 CF 2 CHClF). Because the determination of requires input of Henry's law constant ( K H ), the K H values of the HCFCs were determined at 313–353 K by means of the phase‐ratio variation headspace (PRV‐HS) method in a similar way as determined previously for CHClF 2 . The values of CF 3 CHCl 2 and CF 3 CF 2 CHCl 2 were determined at 313–353 K, whereas hydrolysis of the other HCFCs was not detectable under the experimental conditions examined.…”