1,2-Ethanediol and 1,3-Propanediol Conversions over (MO3)3 (M = Mo, W) Nanoclusters: A Computational Study

Area of Science:

• Computational Chemistry
• Surface Science
• Catalysis

Background:

• Metal oxide nanoclusters are crucial catalysts in chemical transformations.
• Understanding glycol reactions on these surfaces informs catalyst design.
• Previous studies explored alcohol reactions, but glycol pathways require detailed investigation.

Purpose of the Study:

• To computationally investigate the dehydration and dehydrogenation reactions of 1,2-ethanediol and 1,3-propanediol on (MO3)3 nanoclusters (M = Mo, W).
• To elucidate reaction mechanisms, identify key intermediates, and compare reaction pathways.
• To assess the performance of different computational methods for studying these reactions.

Main Methods:

• Density Functional Theory (DFT) and Coupled Cluster (CCSD(T)) calculations were employed.
• Potential energy surfaces were mapped to identify reaction pathways and transition states.
• Lewis acid-base complex formation and hydrogen bonding were analyzed as initiation steps.

Main Results:

• Dehydration is the predominant reaction pathway for both glycols, forming metal bisdiolates.
• Acetaldehyde is the major product for 1,2-ethanediol via alpha-hydrogen transfer.
• 1,3-propanediol exhibits competing C-C bond breaking and proton transfer pathways, leading to various products like propylene oxide and propanal.
• Redox pathways on Mo3O9 are slightly more favorable for 1,2-ethanediol than acetaldehyde formation.
• W(VI) clusters show higher energy barriers for reduction pathways compared to Mo(VI).
• Activation energies for glycol reactions are higher than those for ethanol and 1-propanol.
• CCSD(T) is necessary for accurate energy predictions, outperforming DFT functionals like M06 and B3LYP.

Conclusions:

• Dehydration is the primary reaction pathway for ethanediol and propanediol on Mo/W nanoclusters.
• The reaction mechanisms are complex, involving Lewis acid-base interactions and hydrogen bonding.
• Computational methods like CCSD(T) are essential for accurate quantitative energy calculations in these systems.
• The reducibility of the metal center (Mo vs. W) influences the favorability of redox pathways.