Tautomerization Between Vinyl Alcohol and Acetaldehyde During Catalytic Ethanol Oxidation: The Effect of Water Molecules

10 October 2024, Version 1
This content is a preprint and has not undergone peer review at the time of posting.

Abstract

Catalytic ethanol oxidation reaction (EOR) takes place via many elementary reactions, such as dehydrogenation, C-C bond cleavage, and oxidation of C1 species. Recent studies indicate that hydrogen transfer reaction between intermediate species may need to be included in the reaction network to fully understand the transient kinetics of EOR catalysis. Furthermore, it is important to examine the requirement of the minimum elementary reactions (MERs) in the complex EOR network to calculate the apparent reaction rate and product selectivity. In this work, we performed density functional theory calculations to study the effects of catalyst using Ir(100) and one or two water molecules on the tautomerization reaction between vinyl alcohol (VA) and acetaldehyde (AA). The DFT results show that Ir(100) does not lower the VA-AA tautomerization barrier significantly, however, the presence of water molecules lowers the VA-AA tautomerization barrier considerably. This illustrates that VV-AA tautomerization during EOR occurs with water molecules serving as catalysts.

Keywords

Tautomerization
vinyl alcohol
acetaldehyde
Ir
DFT
EOR

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Comment number 1, Alexey Ignatchenko: Oct 11, 2024, 12:38

Water is not only a catalyst, it's a reagent. Experimental kinetics can show whether it is a first or a second order reaction on the concentration of water. However, there is also a possibility that it is not a one-step mechanism with a cyclic TS, but a stepwise process when either a cation or anion is stabilized by the Ir surface. In such case the barrier could be even lower.