Oxygen and Hydroxyl Species Induce Multiple Reaction Pathways for the Partial Oxidation of Allyl Alcohol on Gold

Abstract

Partial oxidation of alcohols is a topic of great interest in the field of gold catalysis. In this work, we provide evidence that the partial oxidation of allyl alcohol to its corresponding aldehyde, acrolein, over oxygen-precovered gold surfaces occurs via multiple reaction pathways. Utilizing temperature-programmed desorption (TPD) with isotopically labeled water and oxygen species, reactive molecular beam scattering, and density functional theory (DFT) calculations, we demonstrate that the reaction mechanism for allyl alcohol oxidation is influenced by the relative proportions of atomic oxygen and hydroxyl species on the gold surface. Both atomic oxygen and hydroxyl species are shown to be active for allyl alcohol oxidation, but each displays a different pathway of oxidation, as indicated by TPD measurements and DFT calculations. The hydroxyl hydrogen of allyl alcohol is readily abstracted by either oxygen adatoms or adsorbed hydroxyl species on the gold surface to generate a surface-bound allyloxide intermediate, which then undergoes α-dehydrogenation via interaction with an oxygen adatom or surface hydroxyl species to generate acrolein. Mediation of a second allyloxide with the hydroxyl species lowers the activation barrier for the α-dehydrogenation process. A third pathway exists in which two hydroxyl species recombine to generate water and an oxygen adatom, which subsequently dehydrogenates allyloxide. This work may aid in the understanding of oxidative catalysis over gold and the effect of water therein.

Highly efficient and selective reduction of nitroarenes into anilines catalyzed by gold nanoparticles incarcerated in a nanoporous polymer matrix: Role of the polymeric support and insight into the reaction mechanism

“…DFT calculations substantiated this reaction pathway, initially proposed on the basis of a number of experimental evidences [2b,f,4]. Actually labeling experiments using [18] O 2 showed no incorporation of the isotopomer in the oxidation products to confirm that dioxygen acts just as hydride scavenger from the AuNPs surface to produce the hydroperoxo species, Au-OOH, that in turn decomposes to hydrogen peroxide by protonolysis [5]. Interestingly the possibility of obtaining stable Au-H intermediate species paved the way to gold catalysts suitable for reduction reactions.…”

Reliable and efficient reaction path and transition state finding for surface reactions with the growing string method

“…A variety of reaction types, including molecular and dissociative adsorptions, desorptions, and bimolecular and unimolecular reactions, are covered in this set. Most of these reactions have been investigated previously using the NEB method by other researchers . In summary, 43 elementary reactions which consists of nine different metals, one metal oxide, and seven different surface terminations were studied.…”

Theoretical Studies on the Direct Propylene Epoxidation Using Gold-Based Catalysts: A Mini-Review

“…based catalysts [121][122][123][124][125]. Moreover, OMMP (from C3H6 + O) will preferentially react to form propanal (from OMMP1) or acetone (from OMMP2) via a 1,2-H shift reaction instead of PO.…”

“…Although many studies have indicated that the epoxidation of propylene using molecular oxygen is unlikely [11,30] [24], in which the stripping of the methyl hydrogen of propylene by atomic O to yield allyl was found to be facile, leading to the final product allyl alcohol or acrolein. Allyl alcohol is known to convert to acrolein on O-covered Au (111), and this is why acrolein is the main partial oxidation product captured on gold-based catalysts [121][122][123][124][125]. Moreover, OMMP (from C 3 H 6 + O) will preferentially react to form propanal (from OMMP1) or acetone (from OMMP2) via a 1,2-H shift reaction instead of PO.…”