Abstract
Potassium-promoted, alumina-supported molybdenum oxide is investigated for non-oxidative isobutane dehydrogenation, with an emphasis on sub-monolayer coverages. After pre-reduction in H2, initial isobutene turnover frequencies are largely independent of Mo loading, but deactivation rate constants increase by >100-fold as loadings increase to monolayer, leading to a >13-fold difference in reaction rates at extended time on stream. Mo oxidation state by in situ X-ray absorption spectroscopy is stable with time on stream, arguing against continued catalyst restructuring as the origin of deactivation. Across the set of loadings, isobutane dehydrogenation and coke formation are correlated with partially reduced Mo4+ and deeply reduced Moδ+ sites, respectively. Given the stable dehydrogenation activity of low-loaded Mo, in contrast to the rapid deactivation of high-loaded Mo, sub-monolayer metal oxides may warrant further investigation as light alkane dehydrogenation even when their bulk counterparts may not.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 212-222 |
| Number of pages | 11 |
| Journal | Journal of Catalysis |
| Volume | 397 |
| DOIs | |
| State | Published - May 2021 |
Funding
This material is based upon work supported by the National Science Foundation Graduate Research Fellowship Grant No. DGE-1324585. This work is also supported as part of the Institute for Catalysis in Energy Processes funded by the U.S. Department of Energy, Office of Basic Energy Sciences under Award DE-FG02-03ER15457. Metal analysis was performed at the Northwestern University Quantitative Bio-element Imaging Center. This work made use of the J.B. Cohen X-ray Diffraction Facility supported by the Materials Research Science and Engineering Center (MRSEC) under the National Science Foundation Award DMR-1720139. Dr. Qing Ma and Dr. Neil Schweitzer are acknowledged for providing valuable assistance with XAS, which was performed at the DuPont-Northwestern-Dow Collaborative Access Team (DND-CAT) located at Sector 5 of the Advanced Photon Source (APS) and at the Materials Research Collaborative Access Team (MRCAT) located at Sector 10 of APS. DND-CAT is supported by Northwestern University, The Dow Chemical Company, and DuPont de Nemours, Inc. MRCAT operations are supported by the Department of Energy and the MRCAT member institutions. This research used resources of the Advanced Photon Source, 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-AC0-06CH11357. The REACT Facility of the Northwestern University Center for Catalysis and Surface Science is supported by a grant from the DOE (DE-SC0001329). This work also made use of the Keck-II and SPID facilities of Northwestern University’s NUANCE Center, which has received support from the Soft and Hybrid Nanotechnology Experimental (SHyNE) Resource (NSF ECCS-2025633), the International Institute for Nanotechnology (IIN), and Northwestern’s MRSEC program (NSF DMR-1720139).
Keywords
- Dehydrogenation
- Isobutane
- Metal oxides
- Molybdenum oxide
- Sub-monolayer MoO
ASJC Scopus subject areas
- Catalysis
- Physical and Theoretical Chemistry