Elucidating the Mechanism of Ambient-Temperature Aldol Condensation of Acetaldehyde on Ceria

19Citations
Citations of this article
26Readers
Mendeley users who have this article in their library.

This article is free to access.

Abstract

Using in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and density functional theory (DFT) calculations, we conclusively demonstrate that acetaldehyde (AcH) undergoes aldol condensation when flown over ceria octahedral nanoparticles, and the reaction is desorption-limited at ambient temperature. trans-Crotonaldehyde (CrH) is the predominant product whose coverage builds up on the catalyst with time on stream. The proposed mechanism on CeO2(111) proceeds via AcH enolization (i.e., α C-H bond scission), C-C coupling, and further enolization and dehydroxylation of the aldol adduct, 3-hydroxybutanal, to yield trans-CrH. The mechanism with its DFT-calculated parameters is consistent with reactivity at ambient temperature and with the kinetic behavior of the aldol condensation of AcH reported on other oxides. The slightly less stable cis-CrH can be produced by the same mechanism depending on how the enolate and AcH are positioned with respect to each other in C-C coupling. All vibrational modes in DRIFTS are identified with AcH or trans-CrH, except for a feature at 1620 cm-1 that is more intense relative to the other bands on the partially reduced ceria sample than on the oxidized sample. It is identified to be the C═C stretch mode of CH3CHOHCHCHO adsorbed on an oxygen vacancy. It constitutes a deep energy minimum, rendering oxygen vacancies an inactive site for CrH formation under given conditions.

Cite

CITATION STYLE

APA

Bhasker-Ranganath, S., Rahman, M. S., Zhao, C., Calaza, F., Wu, Z., & Xu, Y. (2021). Elucidating the Mechanism of Ambient-Temperature Aldol Condensation of Acetaldehyde on Ceria. ACS Catalysis, 11(14), 8621–8634. https://doi.org/10.1021/acscatal.1c01216

Register to see more suggestions

Mendeley helps you to discover research relevant for your work.

Already have an account?

Save time finding and organizing research with Mendeley

Sign up for free