Chemical looping preferential oxidation of CO over ceria-supported γ-Fe2O3

Abstract

A novel chemical looping preferential oxidation (CL-PROX) process is proposed and demonstrated for eliminating trace CO from a H2-rich stream. The proposed process exhibited an excellent CO removal performance (CO concentration < 100 ppm) and a high H2 recovery (>∼96 %) with a ceria-supported γ-Fe2O3 oxygen carrier. It was obtained by activating the fresh sample that was synthesized through a co-precipitation method and the innovative activation process comprising a partial reduction step at 400 °C followed by an oxidation process at 260 °C. The structure and evolution of iron species in the oxygen carrier were investigated through experimental characterizations during activation and redox cycles. TPR characterizations illustrated a significant difference in the reducibility of the active species, γ-Fe2O3, under H2 and CO atmospheres, which could be the evidence for its relatively high selectivity to CO oxidation. In-situ FTIR characterization also pointed out that the desorption of reaction intermediates to CO2 is facilitated via the reduction of the surface γ-Fe2O3, which might contribute to the outstanding CO oxidation performance of the oxygen carrier. The successful application of chemical looping process to selective oxidation of CO in H2-rich gas not only illustrates a new strategy for H2 purification, but also provides insights into the redox reaction mechanism with the newly-prepared γ-Fe2O3-based oxygen carrier.