Effects of water, salt water, and silicone overcoating of the TiO2 photocatalyst on the rates and products of photocatalytic oxidation of liquid 3-octanol and 3-octanone

The environment of the TiO(2) photocatalyst affects the rate and the ratio of products generated in the photocatalytic oxidation of liquid 3-octanol and 3-octanone. The rates and products were determined with two photocatalysts, one directly solution-contacting and hydrophilic, the other embedded in a poly(methylsiloxane) and hydrophobic: in the neat organic reactant, without added water; with added water; and with NaCl (0.5 M) in the water. 3-Octanone was oxidized to CO(2) and to two organic phase extracted products n-hexanoic acid and n-pentanal. The organic phase extracted initial oxidation products of 3-octanol were 3-octanone, n-hexanal, and n-pentanal. The CO(2) evolution rate was highest in neat 3-octanone when the hydrophilic photocatalyst was in direct contact with the liquid reactant, in which the catalyst particles were uniformly dispersed. When water was added, this photocatalyst resided at the liquid-liquid interface, and the rate of CO(2) evolution was reduced. The rate was further reduced when NaCl was added. When the TiO(2) was embedded in the hydrophobic silicone, the photocatalyst remained dispersed in the organic phase, and the reaction was not inhibited by NaCl The rate of CO(2) formation now exceeded that for the hydrophilic catalyst.