Low Temperature Catalytic Oxidation of Ethanol Using Ozone over Manganese Oxide-Based Catalysts in Powdered and Monolithic Forms

Catalytic oxidation of low concentrations of ethanol was investigated in dry and humid air streams at low temperature (60 degrees C) over manganese oxide-based catalysts supported on a meso-macrostructured TiO2 using ozone as the oxidant. Ethanol was selected as a representative model VOC present in indoor air, and its concentration was fixed to 10 ppm. For that purpose, a series of Mn/TiO2 powder and monolithic catalysts was prepared, some doped with 0.5 wt% Pd. Whatever the catalyst, the presence of water vapor in the gas phase had a beneficial effect on the conversion of ethanol and ozone. The Pd-Mn/TiO2 catalyst containing 0.5 wt% Pd and 5 wt% Mn exhibited superior oxidation efficiency to the Mn/TiO2 counterparts by increasing ozone decomposition (77%) while simultaneously increasing the selectivity to CO2 (85%). The selectivity to CO2 approached nearly 100% by increasing the amount of catalyst from 20 to 80 mg. In a further step, alumina wash-coated cordierite honeycomb monoliths were coated with the 0.5Pd-5Mn/TiO2 catalyst. Full conversion of ethanol to CO2 without residual O-3 emitted (less than 10 ppb) could be attained, thereby demonstrating that the proposed Pd-Mn/TiO2 monolithic catalyst fulfills the specifications required for onboard systems.