Influence of CeO2 morphology on the catalytic oxidation of ethanol in air

Nano-CeO2 catalysts of different shapes were synthesized at different hydrothermal crystallization temperatures from an alkaline aqueous solution. X-ray diffraction (XRD), transmission electron microscope (TEM), and H2 temperature-programmed reduction (H2-TPR) were used to study the synthesized nano-CeO2 catalyst samples. The catalytic properties of the prepared nano-CeO2 catalysts for the catalytic oxidation of ethanol in air were also investigated. TEM analysis showed that CeO2 nanorod and nanocube catalysts have been synthesized at hydrothermal crystallization temperatures of 373 K and 453 K, respectively. XRD results showed that the synthesized nano-CeO2 catalysts have similar cubic fluorite structures. H2-TPR results indicated that CeO2 nanorod and nanocube catalysts exhibit different reduction behaviors for H2 and that the nanorod catalyst has better low-temperature reduction performance than the nanocube catalyst. Ethanol catalytic oxidation results indicated that oxidation and condensation products (including acetaldehyde, acetic acid, CO2, and ethyl acetate) have been produced from the prepared catalysts. The ethyl acetate and acetic acid can be ignited by ethanol at low temperature on the CeO2(R) catalyst to give low catalytic combustion temperature for ethyl acetate and acetic acid molecules. CeO2 nanorods gave ethanol oxidation conversion rates above 99.2% at 443 K and CO2 selectivity exceeding 99.6% at 483 K, while CeO2 nanocubes gave ethanol oxidation conversion rates of about 95.1% until 508 K and CO2 selectivity of only 93.86% at 543 K. CeO2 nanorod is a potential low-cost and effective catalyst for removing trace amounts of ethanol to purify air.