Photocatalytic oxidation of liquid alcohols and binary alcohol mixtures by rutile

Abstract

The photocatalytic oxidation of liquid ethanol, propan-1-ol, propan-2-ol and butan-2-ol, together with the binary mixtures ethanol + propan-2-ol and propan-1-ol + propan-2-ol, has been investigated using rutile suspensions irradiated with 366 nm u.v. light at temperatures in the range 275–313 K. Activities and activation energies for product formation from the individual alcohols were effectively identical. The single activation energy is considered to be the energy required to promote photoelectrons from traps into the rutile conduction band. With the binary mixtures both the activity and activation energy for total carbonyl compound formation were composition independent and approached those of the individual alcohols. Selectivities for specific products were a function of both composition and temperature, and are considered to reflect the availability of the parent alcohols within a saturated physisorbed layer on the rutile surface. The results are discussed in terms of an established radical mechanism.