FTIR kinetic study and products distribution of the reaction of CHCl2C(O)OCH3 with Cl atoms at 298 K and 760 Torr

VIANNI STRACCIA; CYNTHIA RIVELA; MARIA B BLANCO; IULIA PATROESCU-KLOTZ; ILLMANN, NIKLAS; PETER WIESEN; MARIANO A TERUEL

Rennes

Simposio; 26th International Symposium on Gas Kinetics and Related Phenomena ? GK2022; 2022

RSC Gas Kinetic group

The relative rate coefficient and products distribution of the gas-phase reaction of methyl dichloroacetate (CHCl2C(O)OCH3) with Cl atoms were obtained at 298 K and atmospheric pressure. All the experiments were performed in a 480 L Pyrex glass atmospheric simulation reactor coupled with“in situ”FTIR spectroscopy. The rate coefficient obtained from the average of different experiments was: kCl = (3.31 ± 0.50) ×10-13 cm3.molecule-1s-1. In addition, products studies were performed in similar conditions of the kinetic experiments. The initial pathway, for the degradation of methyl dichloroacetate in the reaction with Cl atoms occur via H-atom abstraction at the alkyl groups. Dichloroacetic acid, phosgene, methyl trichloroacetate and carbon monoxide, were the main products identified and quantified. The product yields for the reaction studied were the following: (22±2; 19±3; 16±1 and 38±2) % for Cl2CHCOOH, COCl2, CO, and CCl3C(O)OCH3, respectively. Phosgene is an extremely toxic gas that can be gradually degraded through UV-radiation to produce ClOx which has an important impact on the depletion of ozone layer. The atmospheric implications of the reaction investigated were assessed by the estimation of the tropospheric lifetimes of the chlorinated ester towards Cl atoms to be τCl= 10 years. In addition, other parameters were estimated to evaluate the possible environmental impact of the emissions of MDCA to the air. The Ozone Depletion Potential obtained, (ODP) was 0.044. This fact reflects that the relative influence of this chlorinated organic compound on the destruction of the ozone layer is significant lower than CFCl3. In addition, in order to evaluate the contribution to greenhouse warming, the Global Warming Potential, (GWP) was calculated to be 103, 28, 8 for times horizon of 20, 100 and 500 years, respectively. This contribution to global warming is significant compared with CO2 due to its long lifetime. At regional scale, compounds with Cl, F, N and S substituents may contribute to rainfall acidification. Consequenly, the Acidification Potential of the ester, (AP) was estimated using the empirical equation given by (de Leeuw, 1993),to be 0.45. This value indicates that methyl dichloroacetate degradation may play some role in acidifying rainwater.On the other hand, the Photochemical Ozone Creation Potential, (POCP) was estimated for the title VOC in 0.03, of negligible importance in the photochemical smog formation.References[1] Atkinson, R., Baulch, D.L., Cox, R.A., Hampson, R.F., Kerr, J.A., Rossi, M.J., Troe, J., J. Phys. Chem. Ref. Data 26, 521–1011, 1997.[2] Christensen, L.K., Ball, J.C., Wallington, T.J., J. Phys