Abstraction of hydrogen from methanol by hydroxyl radical in subcritical and supercritical water

Reactions involving hydrogen abstraction by hydroxyl radical are an important class of reactions in subcritical. and supercritical oxidation in water. However, the rates of individual hydrogen abstraction reactions are not available in the literature at the high temperatures and pressures necessary for near-critical or supercritical water oxidation. Here we present the measurements of the hydrogen abstraction from methanol by hydroxyl radical in water at temperatures from ambient to 390 degreesC and at 250 bar. .OH was generated by pulse radiolysis and the kinetics determined by monitoring the growth of the nitrohydroxycyclohexadienyl radical. The measured bimolecular rate constants show Arrhenius temperature dependence from ambient temperature through the supercritical region. The experimental rate constants for hydrogen abstraction from methanol by hydroxyl radical are significantly higher than the values used by a variety of researchers who have attempted to model oxidation of methanol in supercritical water using detailed chemical kinetics models.