(521cg) Reaction Mechanism and Kinetics of Methanol Carbonylation on Atomically Dispersed ReOx/SiO2 from First Principles

Acetic acid is an important industrial commodity chemical used for the production of polyvinyl acetate-based adhesives and alkyl acetates and as a solvent in the synthesis of terephthalic acid¹. The Cativa methanol carbonylation process,² responsible for the majority of produced acetic acid in the world, employs an expensive homogenous complex [Ir(CO)₂I₂]^- and an iodide promoter, which are associated with high separation costs and negative effects on the environment. Recently, a novel heterogeneous, halide-free catalyst – atomically dispersed ReO_x on an SBA-15 inert support – was shown to exhibit a remarkable activity, selectivity, and stability in methanol carbonylation to acetic acid.³

In this work, we employ density functional theory, electronic structure analysis, and mean-field microkinetic modeling to explore the energy landscape of the system, reveal kinetically relevant steps and intermediates, and understand the origin of the superior performance of the ReO_x/SBA-15 catalyst. We identify the redox reaction mechanism that is consistent with reported experimental reaction orders, apparent activation energy, reaction rate, and IR/XANES/EXAFS spectroscopic data. The importance of oxidation states and coordination numbers of a Re metal center is investigated and found to play a critical role in the reactivity of the proposed catalyst.

References

(1) Kalck, P.; Le Berre, C.; Serp, P. Recent Advances in the Methanol Carbonylation Reaction into Acetic Acid. Coord. Chem. Rev. 2020, 402, 213078.

(2) Sunley, G. J.; Watson, D. J. High Productivity Methanol Carbonylation Catalysis Using Iridium. Catal. Today 2000, 58 (4), 293–307.

(3) Qi, J.; Finzel, J.; Robatjazi, H.; Xu, M.; Hoffman, A. S.; Bare, S. R.; Pan, X.; Christopher, P. Selective Methanol Carbonylation to Acetic Acid on Heterogeneous Atomically Dispersed ReO4/SiO2 Catalysts. J. Am. Chem. Soc. 2020, 142 (33), 14178–14189.