Kinetic study of gas phase reactions of OH with CF_3CH_2OH, CF_3CF_2CF_2CH_2OH, and CHF_2CF_2CH_2OH using LP-LIF method

摘要

The rate coefficients for the reactions of OH radicals with three fluoroalcohols, CF_3CH_2OH (k_1), CF_3CF_2CF_2CH_2OH (k_2), and CHF_2CF_2CH_2OH (k_3), have been measured in the temperature range of 298-363 K, at a total pressure of ~ 55 torr, using LP-UF method. The kinetic parameters measured for CF_3CH_2OH, which is well studied, matches with the previous reports within error limits. The rate expression for k_2 is (1.54 ± 0.80) × 10~(12) exp (-765±170)/T), and for k_3 is (1.12 ± 0.26) × 10~(-12) exp (-560±80)/T). Based on the above values of the rate coefficients, the tropospheric lifetimes with respect to removal by reaction with OH have been estimated to be 0.38 and 0.26 years for CF3CF2CF2CH2OH and CHF2CF2CH2OH respectively, supporting their potential use as HFC alternatives. The results are discussed along with the literature data on other fluoroalcohols. The present study is aimed to assess the effect of additional CF_2 groups and H atoms on tropospheric lifetime and global warming potential of fluoroalcohols. The results confirm that the rate coefficients at room temperature and activation energy parameters are independent of n, for the reaction of OH with fluoroalcohols of general formula CF_3(CF_2)nCH_2OH, which are potential CFC/HFC alternatives.