Abstract
The effect of H2O on acetaldehyde oxidation was studied and alpha-, gamma-, delta-MnO2 can be affected by the H2O vapor, while beta-MnO2 is hardly affected by the H2O vapor during acetaldehyde oxidation. The H2O vapor can facilitate the catalytic oxidation of acetaldehyde at moderate temperatures (ca. 70 similar to 100 degrees C), with a negative effect observed at high temperatures (>100 degrees C). The stretching mode of the Mn-O-Mn chains in alpha-, gamma-, delta-MnO2 allows the associatively adsorbed water to absorb on the surface prior to acetaldehyde. Afterwards, acetaldehyde can form hydrogen bonds with the associatively adsorbed water molecules, thus, producing the intermediate carboxylic acid species, which are easily degraded to CO2. The negative effect of H2O on the acetaldehyde oxidation at high temperatures is attributed to the difficulty in adsorbing acetaldehyde on MnO2 via hydrogen bonding with the adsorbed H2O. These findings reveal the role of water in the catalytic oxidation of acetaldehyde.
NSTL
Elsevier