On the Redox Mechanism of Methanol Carbonylation on the Dispersed ReOx/SiO2 Catalyst

18 October 2024, Version 2
This content is a preprint and has not undergone peer review at the time of posting.

Abstract

Acetic acid is industrially produced by methanol carbonylation using Ir- or Rh-based homogeneous catalysts and a corrosive HI promoter. Recently, a heterogeneous catalyst with atomically dispersed ReO4 sites on an inert mesoporous SBA-15 support demonstrated high acetic acid yields and stability without the need for a promoter (Qi et al. J. Am. Chem. Soc. 2020, 142, 14178). In this study, we investigate the reaction mechanisms of methanol carbonylation on monopodal -ORe(=O)3 sites using density functional theory calculations, natural bond orbital analysis, and the energetic span model. We find that the reduction of dispersed Re(VII) oxide by CO through an indirect mechanism is essential for catalyst activation. The C–C coupling of methyl and carbonyl ligands is favorable in both Re(V) and Re(III) complexes, with Re(III) being superior due to transition state stabilization by a metal-localized lone electron pair. The preceding C–O bond activation is favorable only on Re(V) and leads to a thermodynamic sink, posing challenges in interpreting the high carbonylation activity in terms of monopodal ReOx site catalysis. We hypothesize that multi-nuclear sites or more exotic ligand environments drive the cooperative reaction mechanism of selective carbonylation.

Keywords

rhenium oxide
heterogeneous catalysts
redox mechanism
methanol carbonylation
acetic acid

Supplementary materials

Title
Description
Actions
Title
Supporting information: On the Redox Mechanism of Methanol Carbonylation on the Dispersed ReOx/SiO2 Catalyst
Description
Generation and validation of catalytic site models, estimation of the energetic span from experimental kinetic data, tested reaction mechanisms and their energy diagrams
Actions

Comments

Comments are not moderated before they are posted, but they can be removed by the site moderators if they are found to be in contravention of our Commenting Policy [opens in a new tab] - please read this policy before you post. Comments should be used for scholarly discussion of the content in question. You can find more information about how to use the commenting feature here [opens in a new tab] .
This site is protected by reCAPTCHA and the Google Privacy Policy [opens in a new tab] and Terms of Service [opens in a new tab] apply.