Abstract
A series of Al2O3-supported Fe-containing catalysts were synthesized by incipient wetness impregnation. The iron surface density was varied from 1 to 13 Fe atoms/nm2 spanning submonolayer to above-monolayer coverage. The resulting supported Fe-catalysts were characterized by N2 physisorption, ex situ X-ray diffraction (XRD), X-ray pair distribution function (PDF), X-ray absorption spectroscopy (XAS), aberration corrected scanning transmission electron microscopy (AC-STEM) and chemically probed by hydrogen temperature-programmed reduction (H2-TPR). The results suggest that over this entire range of loadings, Fe was present as dispersed species, with only a very small fraction of Fe2O3 aggregates, at the highest Fe loading in oxide phase. The in situ sulfidation of Fe/Al2O3 resulted in the formation of a highly active and selective PDH catalyst. The highest activity with 52% propane conversion and ∼99% propylene selectivity at 560 °C was obtained for the 6.4 Fe/Al2O3-S catalyst, suggesting that this is the highest amount of Fe that could be fully dispersed on the support in sulfided form. XRD and AC-STEM indicated the absence of any crystalline iron sulfide aggregates after sulfidation and reaction. H2-TPR results indicated that the amount of the reducible Fe sites in the sulfided catalyst remained constant above monolayer coverage, and increasing loading did not increase the number of reducible Fe sites. Consistent with these results, the reactivity per gram of catalyst showed no increase with Fe loading above monolayer coverage, suggesting that additional Fe remains conformal to the alumina surface.
| Original language | English |
|---|---|
| Pages (from-to) | 10055-10067 |
| Number of pages | 13 |
| Journal | ACS Applied Nano Materials |
| Volume | 4 |
| Issue number | 10 |
| DOIs | |
| State | Published - Oct 22 2021 |
Funding
This work was supported as part of the Center for Understanding and Control of Acid Gas-Induced Evolution of Materials for Energy (UNCAGE-ME), an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences under Grant DE-SC0012577. S.R. acknowledges support from the American Chemical Society Petroleum Research Fund (Grant 57946-DNI5). A.D. acknowledges support from the NSF/ERC CISTAR under Cooperative Agreement EEC-1647722 and for microscope acquisition under Grant DMR-1828731. 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 Offices of Science by Argonne National Laboratory under Contract DE-AC02-06CH11357. This research used resources at 28-ID-1 of the National Synchrotron Light Source II, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Brookhaven National Laboratory under Contract DE-SC0012704.
Keywords
- HS
- alumina
- catalyst
- iron
- propane dehydrogenation
- sulfidation