X-ray Absorption Spectroscopy of an Fe-Promoted Rh/TiO2 Catalyst for Synthesis of Ethanol from Synthesis Gas
X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) have been used to elucidate the structural features of a 2% Rh-2.5% Fe/TiO{sub 2} catalyst for syngas conversion to ethanol. The results from Rh K-edge and Fe K-edge spectroscopy on a fresh catalyst exposed to air indicated that both Rh and Fe were present as highly dispersed oxides on the titania, and that both adopted a +3 formal oxidation state. For the catalyst reduced in H{sub 2} at 573 K, the Rh K-edge EXAFS revealed Rh-Rh interactions (coordination number N = 6.1, Rh-Rh distance r{sub Rh-Rh} = 2.67 {angstrom}) and a second feature arising from either Rh-Ti or Rh-O coordination. The metal particles contained on an average about 20 atoms, which is consistent with a particle size of 1 nm. A shift in the Rh K-edge XANES by -2 eV indicated that the reduced Rh particles were electron rich compared to bulk Rh metal. Although Rh was reduced completely to the metal by H{sub 2}, the iron oxide promoter was reduced primarily from Fe{sup III} to Fe{sup II} oxide. The results from X-ray absorption spectroscopy at both the Fe and Rh K-edges were unchanged by exposure of the reduced catalyst to syngas (H{sub 2}+CO) at 543 K. A structural model for this ethanol synthesis catalyst is proposed.
- Research Organization:
- Brookhaven National Lab. (BNL), Upton, NY (United States). National Synchrotron Light Source
- Sponsoring Organization:
- DOE - OFFICE OF SCIENCE
- DOE Contract Number:
- DE-AC02-98CH10886
- OSTI ID:
- 1020187
- Report Number(s):
- BNL-96037-2011-JA; TRN: US201116%%167
- Journal Information:
- ChemCatChem, Vol. 1, Issue 2; ISSN 1867-3880
- Country of Publication:
- United States
- Language:
- English
Similar Records
Understanding Electrocatalytic Pathways in Low and Medium Temperature Fuel Cells: Synchrotron-based In Situ X-Ray Absorption Spectroscopy
Vanadium oxide based nanostructured materials for catalytic oxidative dehydrogenation of propane : effect of heterometallic centers on the catalyst performance.
Related Subjects
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
ABSORPTION
ABSORPTION SPECTROSCOPY
AIR
ALCOHOLS
ATOMS
CATALYSTS
ELECTRONS
ETHANOL
FINE STRUCTURE
IRON
IRON OXIDES
OXIDES
PARTICLE SIZE
PROMOTERS
RHODIUM
SPECTROSCOPY
STRUCTURAL MODELS
SYNTHESIS
SYNTHESIS GAS
VALENCE
national synchrotron light source