Revealing the chemical role of Al promoter with extremely low content of 0.85% in Fe2O3 for the High-Temperature Water-Gas Shift Reaction

Abstract

The high-temperature water-gas shift (HT-WGS) reaction is critically important for the development of H₂ production and Al is conventionally considered as a textural promoter to stabilize the surface of the iron oxide phase towards sintering. Here in this paper, we found that Al can also be a chemical promoter with an extremely low content of 0.85% in Fe₂O₃. The results show that due to the addition of Al (from 0.34 to 4.42%), the spinel structured FeAl₂O₄ formed, which can grasp Fe²⁺ and thus improved the CO conversion by redox mechanism. Lower content of Al with the amount of 0.85% (Fe_1.95Al_0.05O₃) exhibited the best activity in terms of CO conversion for HT-WGS at 400 °C and 450 °C. Scanning transmission electron microscopy (STEM) confirmed that atomic isolation of Al atoms within Fe₃O₄ lattice not only optimizes the hydrogen-binding energy but also decreases the free energy of water formation, thus leading to excellent thermocatalytic activity of Al1-Fe₂O₃ catalyst. The results show that Al can be a chemical promoter and via engineering Al at atomic level, which is highly effective for rational design of HT-WGS catalysts with high performance.

Keywords: Water-gas shift reaction, Al promoter, Chemistry role

DOI: 10.7176/CMR/17-1-05

Publication date: March 30^th 2025