Effect of Water on Ethanol Conversion over ZnO
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This work focuses on understanding the role of water on ethanol conversion over zinc oxide (ZnO). It was found that a competitive adsorption between ethanol and water occurs on ZnO, which leads to the blockage of the strong Lewis acid site by water on ZnO. As a result, both dehydration and dehydrogenation reactions are inhibited. However, the extent of inhibition for dehydration is orders of magnitude higher than that for dehydrogenation, leading to the shift of reaction pathway from ethanol dehydration to dehydrogenation. In the secondary reactions for acetaldehyde conversion, water inhibits the acetaldehyde aldol-condensation to crotonaldehyde, favoring the oxidation of acetaldehyde to acetic acid, and then to acetone via ketonization at high temperature (i.e., 400 °C).
KeywordsEthanol ZnO Water dissociation Ketonization Aldol-condensation
We acknowledge the US Department of Energy, Office of Basic Energy Sciences for the financial support, the WSU Franceschi Microscopy Center and Dr. Knoblauch for the use of the TEM. Junming Sun acknowledges the New Faculty Seed Grant support from Washington State University.