Copper promotion of chromium-doped iron oxide water-gas shift catalysts under industrially relevant conditions

Ariëns, M.I.; van de Water, L. G.A.; Dugulan, A.I.; Brück, E.H.; Hensen, E. J.M.

doi:10.1016/j.jcat.2021.12.013

Copper promotion of chromium-doped iron oxide water-gas shift catalysts under industrially relevant conditions

Title

Copper promotion of chromium-doped iron oxide water-gas shift catalysts under industrially relevant conditions

Author

Ariëns, M.I. (TU Delft RST/Fundamental Aspects of Materials and Energy; Eindhoven University of Technology)
van de Water, L. G.A. (Johnson Matthey Technology Center)
Dugulan, A.I. (TU Delft Instrumenten groep; TU Delft RST/Fundamental Aspects of Materials and Energy)
Brück, E.H. (TU Delft RST/Fundamental Aspects of Materials and Energy)
Hensen, E. J.M. (Eindhoven University of Technology)

Date

2022

Abstract

Copper promotion of chromium-doped iron oxide prepared via co-precipitation for high-temperature water–gas shift (WGS) catalysis is investigated. Low-temperature Mössbauer spectra demonstrate that copper doping delays hematite (α-Fe₂O₃) formation in the fresh catalyst, favoring the formation of small crystallites of ferrihydrite (Fe₅HO₈∙4 H₂O). Catalysts are treated under industrial WGS conditions at 360 °C (activity evaluation) and 450 °C (ageing) at 2 and 25 bar. Mössbauer spectra show that chromium is incorporated in octahedral sites of the active magnetite (Fe₃O₄) phase, resulting in a partially oxidized structure. Copper doping did not affect the bulk magnetite structure of the activated catalyst, which points to the presence of a separate copper phase. Near-ambient pressure XPS shows that copper is in the metallic state. XPS of discharged catalysts evidenced that reaction at elevated pressure resulted in the surface reduction of Fe³⁺ to Fe²⁺. Copper promotion enhances CO conversion under high-temperature WGS conditions.