ReOx as a Br?nsted acidic modifier in glycerol hydrodeoxygenation: Computational insight into the balance between acid and metal catalysis

A computational study for the competitive conversion of glycerol to 1,2-propanediol and 1,3-propanediol is presented, considering a two-step sequence of dehydration followed by hydrogenation. The elementary steps for dehydration, i.e., breaking of C-H followed by C-OH or vice versa, were studied computationally both on the Rh metal surface and the acid-modified ReOH-Rh surface in order to understand the role of the acid promoter. While the acid modifier can catalyze the C-OH cleavage, the activation energy for the C-H cleavage was found to be considerably smaller on both pure and acid-doped Rh(111) surfaces, and breaking the secondary C-H bond is kinetically favored over breaking the terminal C-H bond. This is in complete agreement with experimental protocols favoring the formation of 1,2-propanediol. Another potential feedstock, glycidol, was studied for the epoxide ring opening to yield 1,2-propanediol and 1,3-propanediol, and the reaction was found to be metal-catalyzed even in the presence of acid.(c) 2023 The Author(s). Published by Elsevier Inc. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).