Unveiling the Nitrogen-Doping Mechanism in Carbon Catalysts for Oxidative Dehydrogenation of Ethanol to Acetaldehyde.

Abstract

Oxidative dehydrogenation (ODH) of ethanol to acetaldehyde is an important production process. However, it still suffers from low deactivation, selectivity, and high costs. Herein, we developed a new strategy for preparing mesoporous nitrogen-doped carbon catalysts by carbonization of phenolic resin with silica as a hard template. The catalyst demonstrated an impressive acetaldehyde selectivity of over 76% at 270 °C for 25 h during the ODH of ethanol to acetaldehyde. Mechanistic studies have shown that the two carbon atoms in adjacent C=O groups are replaced by nitrogen atoms in the N₀-Gra-O structural unit. The C=O functional group on the surface of the catalyst is the active center for the ODH of ethanol to acetaldehyde, and the introduction of nitrogen atoms can reduce the adsorption capacity of acetaldehyde molecules at the active site (ΔG values can be reduced by 0.11-0.45 eV), enabling rapid desorption of the product and avoiding the problem of excessive oxidation, thereby improving the selectivity of acetaldehyde. This work reveals the structure-activity relationship between active sites and selective regulation of nitrogen-doped carbon-based catalysts for the ODH of ethanol, providing a theoretical basis for the development of efficient non-metallic carbon-based catalysts.