40617-75-2Relevant academic research and scientific papers
Rate Mechanism of the Atmospheric Degradation of 1,1,1,2-Tetrafluoroethane (HFC-134a)
Bednarek,Ereil,Hoffmann,Kohlmann,Moers,Zellner
, p. 528 - 539 (2007/10/03)
Ihe atmospheric chemical behaviour of 1,1,1,2-tetrafluoroethane (CF3CFH2, HFC-134a) with respect to its rate and mechanism of degradation in the troposphere has been investigated. The rate coefficient for the reaction of (i a) CF3CFH2 +OH→CF3CFH + H2O has been determined in direct time-resolved experiments using iaser-pulse initiation and laser long-path absorption. A value of kia = (4.6±0.5)×10-15 cm3 A at T = 295K has been found. The ratio of the rate coefficients for the reactions of the CF3CFHO-radical with O2, (4) CF3CFHO + O2→CF3CFO + HO2, and C-C bond fission, (5) CF3CFHO + M→CFHO + CF3 + M, for T =295 K and ptotal = 50 mbar (O2) has been obtained to be k4/(k5 [M]) = 1.5×10-19 cm3, with the individual values being k4 = 2.7×10-15 cm3/s and k5 [M] = 1.8×104 s-1. The mechanism of the atmospheric degradation of HFC-134a has been investigated in the temperature range 244-295 K and ptotal = 1000 mbar using UV photolysis/FTIR product studies. From these experiments the Arrhenius expression k4/(k5 [M]) = 8.7 ×10-25 exp ((3240-610+990) K/T) cm3 was determined. Moreover, it is concluded that the major carbonyl products are CF3CFO, CFHO and CF2O which result from the two possible reactions of the oxy radical CF3CFHO. As a consequence the yield of these carbonyl products is dependent on temperature, O2 partial pressure and total pressure. For the reaction of CFHO with Cl atoms the Arrhenius expression k18 = 5.7×10-14 exp (-(1130 ±160)K/T)cm3/s was determined in the temperature range 244-298 K. VCH Verlagsgeseuschaft mbH, 1996.
