Kinetics of the Rapid Dark Reaction between Methanol and Oxygen in the Presence of a "Photocatalyst"

Article abstract of DOI:10.1021/j100040a022

It has been discovered that a rapid dark reaction occurs on adding platinized TiO2 "photocatalyst" to liquid methanol before and/or during degassing resulting in large amounts of formaldehyde (mostly in the form of methoxymethanol) being present at the start of subsequent photolyses.The kinetics of this reaction has been studied in a magnetically stirred reactor over the temparature range 282-325 K, yielding an activation energy essentially equal to the value for diffusion of O2 through CH3OH (l).The rate constants measured at t = 0 are only (2.4 +/- 0.7) * 10^-4 times theoretical diffusion-limited values, indicating that the rapid reaction only occurs at widely-spaced platinuum-coated sites.Turnover numbers as large as 2200 per Ti atom (1.1 * 10⁷ per active site) were measured after 27 h of reaction.Methyl formate, formic acid, and CO2 are observed as secondary reaction products, with some indication of higher hemiformals being formed as well.