Complete oxidation of ethanol over alkali-promoted Pt/Al2O3 catalysts

The catalytic performance of alkali (K+ and Na+)-promoted Pt/Al2O3 catalysts for the complete oxidation of ethanol present in trace amounts (500 ppm) in air has been investigated. Pure alumina acts mainly as an acidic catalyst producing diethyl ether and ethylene, while complete oxidation of ethanol to CO2 requires temperatures higher than 400 °C. Addition of alkalis in alumina neutralizes its acidic sites and suppresses the formation of diethylether and ethylene. Ethanol oxidation over the Pt/Al2O3 catalyst results in the formation of partially oxidized compounds, such as acetaldehyde and acetic acid, as well as CO2 at higher temperatures. Alkali-promoted catalysts do not produce acetic acid and are significantly more active than un-promoted Pt/Al2O3, especially when they have been pre-reduced. The most effective catalyst was Pt/Al2O3 (K/Al = 0.10), in which complete oxidation of ethanol to CO2 was achieved at ∼220 °C, while complete oxidation of ethanol over the un-promoted catalyst was obtained at 280 °C.