A kinetic study of the liquid-phase hydrogenation of citral on Au/TiO2 and Pt–Sn/TiO2 thin films in capillary microreactors

The kinetics of the liquid-phase hydrogenation of citral (3,7-dimethyl-2,6-octadienal) on Au/TiO2 and Pt–Sn/TiO2 thin films was studied in the temperature range 313–353 K and citral concentrations of 0.25–10.0 mol m−3. The thin films were deposited onto the inner walls of silica capillaries with internal diameter of 250 μm. First-order dependence on hydrogen pressure and near zero order dependence on citral concentration were observed for the initial rate of citral hydrogenation over the Pt–Sn/TiO2 and Au/TiO2 thin films. The Au/TiO2 catalyst prevents citronellal formation. The highest yield of unsaturated alcohols was obtained on the Pt–Sn/TiO2 film at a reaction temperature of 343 K, liquid residence time of 30 min and a citral conversion of 99%.

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► The Pt–Sn/TiO2 catalytic coating is more active and selective if to compare with Au/TiO2 one.
► The yield of unsaturated alcohols of 79% was obtained on the Pt–Sn/TiO2 thin film.
► The proposed kinetic model suitably describes the obtained experimental data.
► The reaction orders were found to be 1 for hydrogen and 0.07–0.08 for citral.