PRESSURE AND TEMPERATURE-DEPENDENCE OF THE KINETICS OF THE REACTION AL+CO2

We measured the pressure and temperature dependence of the rate constants of the reaction of Al + CO2 between 10 and 600 Torr total pressure and 298 and 1215 K in our high-temperature reactor. The Al atoms were generated by the 248-nm photolysis of Al(CH3)3 and probed by laser-induced fluorescence. Below 700 K, the rate constants show a strong pressure dependence suggesting that the reaction is proceeding through a complex formation mechanism with some decomposition of the complex to the products AlO and CO. Above 700 K, the observed rate constants are pressure independent, indicating that a direct abstraction channel becomes dominant. An Arrhenius fit to the rate constants measured in this high-temperature regime results in a preexponential factor of (2.9 +/- 0.7) X 10(-10) cm3 s-1 and an activation energy of 6.4 +/- 0.4 kcal mol-1.