A chemical looping process for hydrogen production using iron-containing perovskites

Abstract

A comparison is made between La_0.6Sr_0.4Co_0.2Fe_0.8O_3−δ and La_0.7Sr_0.3FeO_3−δ perovskite-type oxides, co-precipitated iron oxide (60% Fe₂O₃/Al₂O₃) and supported nickel oxide (20% NiO/Al₂O₃) as oxygen carrier materials for the water-gas shift reaction in a chemical looping process with the goal of steady production of hydrogen over more than 100 redox cycles. A temperature programmed survey of redox activity over five cycles was used to confirm the potential of the materials as oxygen carriers for this reaction and give some idea of appropriate temperatures for operation. Isothermal redox cycles at 850 °C were performed with the most promising materials, 60% Fe₂O₃/Al₂O₃ and La_0.7Sr_0.3FeO_3-δ. Initially the 60% Fe₂O₃/Al₂O₃ produced over double the amount of hydrogen (on a mass basis) compared to La_0.7Sr_0.3FeO_3-δ, but following 150 cycles performances from both materials were similar. More importantly, the perovskite material showed a steady hydrogen production over more than 100 cycles whereas the 60% Fe₂O₃/Al₂O₃ never showed steady hydrogen production. It can be concluded that La_0.7Sr_0.3FeO_3−δ is an attractive material for the chemical looping water-gas shift process.