Kinetics of Al+H2O Reaction: Theoretical Study

Quantum chemical calculations were carried out to study the reaction of Al atom in the ground electronic state with H2O molecule. Examination of the potential energy surface revealed that the Al + H2O -> AlO + H-2 reaction must be treated as a complex process involving two steps: Al + H2O -> AlOH + H and AlOH + H -> AlO + H-2. Activation barriers for these elementary reaction channels were calculated at B3LYP/6-311+G(3df,2p), CBS-QB3, and G3 levels of theory, and appropriate rate constants were estimated by using a canonical variational theory. Theoretical analysis exhibited that the rate constant for the Al + H2O products reacron measured by McClean et al. must be associated with the Al + H2O -> AlOH + H reaction path only. The process of direct HAlOH formation was found to be negligible at a pressure smaller than 100 atm.