Reaction and characterization studies of an industrial Cr-free iron-based catalyst for high-temperature water gas shift reaction

Abstract

Activity and stability of an industrial Cr-free iron-based catalyst (NBC-1) for high-temperature water gas shift (WGS) reaction were studied in a fixed-bed reactor under 350 °C, 1 atm, H 2O:gas = 1:1 and 3000 h −1 (dry-gas basis). Physical properties of the NBC-1 catalyst before and after the WGS reaction, the desorption behavior of H 2O, CO, CO 2 and H 2, and surface reaction over the catalyst were characterized by BET, X-ray diffraction (XRD), Mössbauer emission spectroscopy (MES), temperature programmed desorption (TPD) and temperature programmed surface reaction (TPSR). The NBC-1 catalyst is active and has excellent thermo-stability even after pretreatment at a high temperature of 530 °C. Its activity and thermo-stability are comparable to those of an UCI commercial Fe-Cr catalyst, C12-4. XRD and MES studies show that iron in the fresh NBC-1 catalyst is present as γ-Fe 2O 3, most of which is converted to Fe 3O 4 during reduction and reaction. Results of TPD demonstrate that adsorbed CO 2 and CO cannot exist on the NBC-1 surface beyond the temperature of 300 °C while higher temperatures (>400 °C) are required to completely desorb H 2O. A redox mechanism of WGS on the NBC-1 surface is proposed based on the TPD and TPSR observations.