Rate Constants of the OH-initiated oxidation of selected unsaturated esters between 283 and 313 K

M. B .BLANCO, I. BEJAN, I. BARNES, P. WIESEN AND M.A.TERUEL

Manchester ,UK

Simposio; 20th International Symposium on Gas Kinetics; 2008

Unsaturated esters are used in the production of polimers and resins and until 1991 they were registered for use as pesticides. The sources of their emissions are manufacturers of plastics, aircraft and electronic components1 and they have wide applications as solvents and industrial feedstocks. The release of these oxygenated volatile compounds (VOCs) into the atmosphere is likely to contribute to the formation of ozone and other components of photochemical smog found in urban areas through their reactions mainly with OH radicals and others oxidants like NO3 radicals, O3 molecules and Cl atoms. In order to assess the impact of these species on air quality, kinetic and mechanistic information on their tropospheric degradation is therefore needed2.   In the present study we have investigated the kinetics of the reactions of OH radicals with the following unsaturated compounds:                               OH + CH2=C(CH3)C(O)OCH3                                             Products             (1)                                       OH + CH2=CHC(O)O(CH2)3CH3                                      Products               (2)                             OH + CH2=C(CH3)C(O)O(CH2)3CH3                          Products                    (3)                             OH + CH2=CHOC(O)CH3                                    Products                              (4)   The experiments were carried using a relative rate method over the temperature range 283-313 K at atmospheric pressure of air. The experimental system consisted in a large volume photo-reactor using in situ FTIR analysis to monitor the decay of the organics and the reference compounds. The observed temperature dependences for k1, k2, k3 and k4 were the following:                                                     k1 = (2.07 ± 1.05) ´ 10-12 ´ e (766 ± 52) / T                                                                         k2 = (2.44 ± 0.95) ´ 10-12 ´ e (979 ± 56) / T                                                                          k3 = (1.65 ± 1.05) ´ 10-12 ´ e (344 ± 44) / T                                                   k4 = (1.96 ± 1.02) ´ 10-12 ´ e (449 ± 49) / T     To the best of our knowledge this work provides the first temperature dependence studies for these reactions, except for CH2=C(CH3)C(O)OCH3 were there is a previous data reported in the literature. Our value of k1 is in excellent agreement with the value reported previously using PLP-LIF system3. The kinetic data are presented in Arrhenius form and used to calculate the activation energies and preexponential factors. The atmospheric implications of the cited reactions were estimated through the kinetic data obtained in this work and in addition reactivity trends are also discussed.