Mechanistic Effects of Water on the Fe-Catalyzed Hydrodeoxygenation of Phenol. The Role of Brønsted Acid Sites
- The Gene &, Linda Voiland School of Chemical Engineering and Bioengineering, ∥Department of Physics and Astronomy, and ⊥Department of Chemistry, Washington State University, Pullman, Washington 99164, United States; Institute for Integrated Catalysis and §Fundamental and Computational Sciences Directorate, Pacific Northwest National Laboratory, Richland, Washington 99352, United States
A mechanistic understanding of the roles of water is essential for developing highly active and selective catalysts for hydrodeoxygenation (HDO) reactions since water is ubiquitous in such reaction systems. Here, we present a study for phenol HDO on Fe catalysts using density functional theory which examines the effect of water on three elementary pathways for phenol HDO using an explicit solvation model. The presence of water is found to significantly decrease activation barriers required by hydrogenation reactions via two pathways. First, the proton transfer in the hydrogen bonding network of the liquid water phase is nearly barrierless, which significantly promotes the direct through space tautomerization of phenol. Second, due to the high degree of oxophilicity on Fe, liquid water molecules are found to be easily dissociated into surface hydroxyl groups that can act as Brønsted acid sites. These sites dramatically promote hydrogenation reactions on the Fe surface. As a result, the hydrogen assisted dehydroxylation becomes the dominant phenol HDO pathway. This work provides new fundamental insights into aqueous phase HDO of biomass-derived oxygenates over Fe-based catalysts; e.g., the activity of Fe-based catalysts can be optimized by tuning the surface coverage of Brønsted acid sites via surface doping.
- Research Organization:
- Pacific Northwest National Lab. (PNNL), Richland, WA (United States). Environmental Molecular Sciences Lab. (EMSL)
- Sponsoring Organization:
- USDOE Office of Science (SC), Basic Energy Sciences (BES)
- DOE Contract Number:
- AC05-76RL01830
- OSTI ID:
- 1427904
- Report Number(s):
- PNNL-SA-130676; 49339; KC0302010
- Journal Information:
- ACS Catalysis, Vol. 8, Issue 3; ISSN 2155-5435
- Publisher:
- American Chemical Society (ACS)
- Country of Publication:
- United States
- Language:
- English
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