Propan-1-ol Oxidation Reaction on Au/TiO₂ Catalysts

Abstract

Alcohols such as propanol and n- butanol have been oxidised to aldehydes by resin- supported gold in the liquid phase, and several other primary and secondary alcohols have been oxidised with very high selectivity in vapour phase over a 1wt% Au/SiO₂ catalyst between 373- 573K. In this work, the adsorption of propan-1-ol was carried over 1%Au/TiO₂ catalysts prepared by deposition precipitation method. This was further investigated using Pulse Flow reactor, TPFRP, TPD, and XRD,. The adsorption of propan-1-ol over TiO₂ (P25) indicated a full monolayer with much of it in a dissociated state, forming propoxy group on the cationic site and hydroxyl group at anions. The propoxy is relatively stable until about 250^oC, at which dehydration to propene occurs by bimolecular surface reaction. As the concentration of propoxy on the surface disappear, so mechanism reverts to a decomposition pathway, producing CO₂ and H₂O. However, the presence of gold on the catalyst is marked with complete conversion of propan-1-ol at low temperature (230^oC) lower than Titania (300^oC). Similarly, propan-1-ol oxidation on Au/TiO₂ catalyst was followed by dehydration to propene at 300^oC (Characteristic of TiO2) and dehydrogenation to propanal at high temperature. The evolution of CO₂ and H₂ appear to be due to the production of formate species on the surface of the catalyst. This formate species is mainly involved in the complete oxidation reaction of propan-1-ol on the catalysts.

Keywords: Gold Catalysis, Propan-1-ol Oxidation, TPD, TPFRP, XRD