Abstract
With the increase in the importance of renewable resources, chemical research is shifting focus toward substituting petrochemicals with biomass-derived analogues and platform-molecule transformations such as alcohol processing. To these ends, in-depth mechanistic understanding is key to the rational design of catalytic systems with enhanced activity and selectivity. Here we discuss in detail the structure and reactivity of a single-site active carbon-supported molybdenum-dioxo catalyst (AC/MoO2) and the mechanism(s) by which it mediates alcohol dehydration. A range of tertiary, secondary, and primary alcohols as well as selected bio-based terpineols are investigated as substrates under mild reaction conditions. A combined experimental substituent effect/kinetic/kinetic isotope effect/EXAFS/DFT computational analysis indicates that (1) water assistance is a key element in the transition state; (2) the experimental kinetic isotopic effect and activation enthalpy are 2.5 and 24.4 kcal/mol, respectively, in good agreement with the DFT results; and (3) several computationally identified intermediates including Mo-oxo-hydroxy-alkoxide and cage-structured long-range water-coordinated Mo-dioxo species are supported by EXAFS. This structurally and mechanistically well-characterized single-site system not only effects efficient transformations but also provides insight into rational catalyst design for future biomass processes.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 1247-1257 |
| Number of pages | 11 |
| Journal | ACS Catalysis |
| Volume | 12 |
| Issue number | 2 |
| DOIs | |
| State | Published - Jan 21 2022 |
Funding
Financial support is provided by Office of Basic Energy Sciences, Department of Energy (DE-FG02-03ER154757) to the Institute for Catalysis in Energy Processes (ICEP) at Northwestern University (J.L., Y.K., A.D.). We gratefully acknowledge Northwestern Integrated Molecular Structure Education and Research Center (IMSERC) for the use of NMR and MS facilities and Northwestern University Atomic and Nanoscale Characterization Experimental Center (NUANCE) for the use of Keck-II facility, which have received support from the Soft and Hybrid Nanotechnology Experimental (SHyNE) Resource (NSF ECCS-2025633), the State of Illinois, and the International Institute for Nanotechnology (IIN), the Northwestern University Ngyuyen group, Northwestern’s MRSEC program (NSF DMR-1720139), and Northwestern University. This work used the 5-BM-D beamline of the DuPont-Northwestern-Dow Collaborative Access Team (DND-CAT) located at Sector 5 of the Advanced Photon Source (APS). DND-CAT is supported by NU, E. I. DuPont de Nemours & Co., and The Dow Chemical Company. This research used resources of the APS, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357. This research was supported in part by the computational resources and staff contributions provided by the Quest High Performance Computing Facility at NU, which is jointly supported by the Office of the Provost, the Office for Research, and Northwestern U. Information Technology. We thank Dr. Alexander Kaushansky of the Technion Israel Institute of Technology for helpful discussions and DFT consultations.
Keywords
- alcohol dehydration
- dehydrogenation
- heterogeneous catalysis
- molybdenum
- single-site catalyst
ASJC Scopus subject areas
- Catalysis
- General Chemistry