High purity hydrogen production via sorption enhanced chemical looping reforming: Application of 22Fe2O3/MgAl2O4 and 22Fe2O3/Al2O3 as oxygen carriers and cerium promoted CaO as CO2 sorbent

Abstract

High purity hydrogen can be produced using sorption enhanced chemical looping reforming (SE–CLR) in which an oxygen carrier and an in situ CO2 sorbent are involved. In this study, the effectiveness of alumina modification with Mg as the support of Fe2O3 based oxygen carriers is investigated in CLR and SE–CLR processes for clean hydrogen production. The 22Fe2O3/Al2O3 and 22Fe2O3/MgAl2O4 oxygen carriers are synthesized with impregnation and sequential impregnation methods, respectively. Prior to SE–CLR process, the performance of three different calcium based sorbents including industrial CaO, synthesized CaO and cerium promoted CaO are investigated for CO2 sorption in calcium loop. The characterization of the oxygen carriers and sorbent samples is performed by XRD, BET, FESEM and TEM. It is found that the addition of cerium to the calcium-based sorbent effectively improves its structural properties and CO2 sorption performance. The obtained results reveal that the sorbent surface area is a significant parameter affecting its CO2 removal efficiency at high temperatures. In addition, the presence of Mg in oxygen carrier structure successfully prevents the formation of Fe–Al spinel by MgAl2O4 formation. An excessive H2/CO molar ratio of 16.7 is also achieved using Fe2O3/MgAl2O4 oxygen carrier and synthesized Ce/Ca=0.2 sorbent at 600°C in SE–CLR process.