Multifunctional Ni-based oxygen carrier for H2 production by sorption enhanced chemical looping reforming of ethanol

The sorption enhanced chemical looping reforming is a prospective technology for high-quality hydrogen production. In this technology, the full benefits of catalysis, oxygen transfer, and CO2 adsorption are achieved by the utilization of oxygen carriers and sorbents. However, most sorbents that are mixed physically into the reforming bed are liable to encountering ash fouling and porosity reduction, preventing CO2 adsorption and sorbent regeneration. In this work, we develop a multifunctional composite oxygen carrier, which combines the NiO/ NiAl2O4 catalyst with the CaO sorbent into a one-body composite pellet. Compared with the conventional physically mixed oxygen carrier, the composite oxygen carrier shows uniform element distribution, superior reducibility, and shortened dead time, resulting in enhanced CO2 adsorption capacity, high H2 production efficiency, and excellent ethanol conversion. Furthermore, during 20 cycle tests, the stable CO2 adsorption capacity and H2 concentration of composite oxygen carrier were maintained, while the H2 concentration of mixed oxygen carrier sharply decreased because of deteriorated adsorption performance. The results confirm that the multifunctional composite oxygen carrier is more suitable than the mixed oxygen carrier for CO2 adsorption and high purity hydrogen production. This work opens a new avenue toward the performance improvement of oxygen carriers.