INVESTIGADORES
BLANCO Maria Belen
congresos y reuniones científicas
Título:
A temperature dependent kinetic study of the gas-phase reactions of Cl atoms with different unsaturated compounds
Autor/es:
MARIANO A. TERUEL, IAN BARNES AND M. B. BLANCO
Lugar:
Leuven, Belgium
Reunión:
Simposio; 21st International Symposium on Gas Kinetics; 2010
Resumen:
In the last few years, a growing number of experimental studies have been carried out on the reactivity of chlorine atoms with unsaturated compounds. Isobutene, 1,3-butadiene, methyl crotonate and b,b-dimethylacrolein are emitted in the atmosphere from anthropogenic and biogenic sources as they are used as solvents, intermediates in closed systems for chemical synthesis and in several industrial processes. The release of these volatile organic compounds (VOCs) to the atmosphere is likely to contribute to the formation of ozone, peroxy acetyl nitrate (PAN) and other photooxidant components of photochemical smog that are formed in urban areas through the reactions of the VOCs mainly with OH radicals and other oxidants such as NO3 radicals, O3 molecules and Cl atoms [1].             The aim of this study was to determinate the rate coefficients of the following reactions:                         CH2=CH(CH3)2                  +     Cl  ¨          Products,            k1                         CH2=CHCH=CH2                +     Cl  ¨          Products,                       k2                         CH3CH=CHC(O)OCH3  +     Cl  ¨          Products,            k3                         (CH3)2C=CHC(O)H        +     Cl  ¨          Products             k4             Relative kinetic measurements were performed in the temperature range 287-313K and atmospheric pressure of air in a 1080 L photoreactor coupled with in situ FTIR analysis to monitor the decay of the organics and the reference compounds. The kinetic data obtained were used to derive the first temperature dependence Arrhenius expressions for the reactions (in units of cm3 molecule-1s-1): k1 = (1.98 } 0.95) ~ 10-13 exp[(2216 } 289)/T], k2 = (0.67 } 0.37) ~ 10-13 exp[(2585 } 346)/T], k3 = (1.39 } 0.61) ~ 10-14 exp[(2849 } 397)/T] and k4 = (2.18 } 1.01) ~ 10-12 exp[(1413 } 129)/T] (Figure 1). Negative temperature dependencies of the rate constants were obtained for the four reactions studied which supports that addition of Cl to the double bond is the main reaction path as observed for Cl + alkene and Cl + unsaturated and oxygentated VOCs reactions            The kinetic data obtained in this work has been used in conjunction with other kinetic data to access the possible atmospheric implications of release of the compounds to the atmosphere.