Photocatalytic Direct Conversion of Ethanol to 1,1-Diethoxyethane over Noble-Metal-Loaded TiO2 Nanotubes and Nanorods

As one of the most important biomass platform molecules, ethanol needs to have its product chain chemically extended to meet future demands in renewable fuels and chemicals. Additionally, chemical conversion of ethanol under mild and green conditions is still a major challenge. In this work, ethanol is directly converted into 1,1-diethoxyethane (DEE) and H-2 under mild photocatalytic conditions over platinum-loaded TiO2 nanotubes and nanorods. The reaction follows a tandem dehydrogenation-acetalization mechanism, in which ethanol is first dehydrogenated into acetaldehyde and H+ ion by photogenerated holes, and then acetalization between acetaldehyde and ethanol proceeds through promotion by H+ ions formed in real time. Excess H+ ions are simultaneously reduced into H-2 by photogenerated electrons. This photocatalytic process has a very high reaction rate over nanosized tubular and rod-like TiO2 photocatalysts, reaching 157.7mmolg(-1)h(-1) in relatively low photocatalyst feeding. More importantly, the reaction is highly selective, with a nearly stoichiometric conversion of reacted ethanol into DEE. This photocatalytic dehydrogenation CO coupling of ethanol is a new green approach to the direct efficient conversion of ethanol into DEE and provides a promising channel for sustainable bioethanol applications.