Chemically and physically robust, commercially-viable iron-based composite oxygen carriers sustainable over 3000 redox cycles at high temperatures for chemical looping applications

Abstract

A low-cost oxygen carrier material realized through an Al-based skeleton encapsulating iron–titanium oxides with long-term chemical reactivity and mechanical stability for commercial chemical looping applications.

Structure and phase evolution of CaMnO3 perovskite during isothermal redox cycles

“…Thermochemical redox schemes in CLC over perovskites generally constitute CH 4 ‐induced reduction and re‐oxidation under O 2 (∼1000 °C) . In this work, noteworthy isothermal redox activity at lower temperatures (600–900 °C) was observed for the as synthesized CaMnO 3 (Figure ).…”

Redox reactivity of titania‐doped YSZ‐promoted iron‐based oxygen carrier over multiple redox cycles for chemical looping reforming of methane and hydrogen production

“…The prepared oxygen carrier was reacting with reducing gases (10% H 2 , CO, and CH 4 ) or oxidizing gas (10% H 2 O) balanced with N 2 using a Perkin Elmer TGA‐7 thermogravimetric analyzer (TGA) to determine the degree of solid conversion (from Fe 2 O 3 to FeO or Fe) and the reaction rates. TGA experiments were conducted with high gas flows (300 sccm) and sample masses (20 mg) to reduce mass transfer resistance as much as possible . The degree of solid oxidation was calculated as X = [( m − m Fe )/( m Fe2O3 − m Fe )] × 100 (%), where m Fe2O3 and m Fe were the masses of the fully oxidized state of hematite and fully reduced state of Fe, respectively.…”

“…TGA experiments were conducted with high gas flows (300 sccm) and sample masses (20 mg) to reduce mass transfer resistance as much as possible. 31,39 The degree of solid oxidation was calculated as X = [(m − m Fe )/(m Fe2O3 − m Fe )] × 100 (%), where m Fe2O3 and m Fe were the masses of the fully oxidized state of hematite and fully reduced state of Fe, respectively. For instance, X = 100%, 66.7%, and 0% for Fe 2 O 3 , FeO, and Fe, respectively.…”

“…The ilmenite‐based material, FeTiO 3 , as an oxygen carrier was considered desirable for good reactivity and low cost . The iron‐titanium oxide oxygen carriers were modified to overcome kinetics and stability issues . However, it underwent a phase separation forming an outer hematite layer during repeated redox cycles, which might decrease in the reactivity …”

“…28,29 The irontitanium oxide oxygen carriers were modified to overcome kinetics and stability issues. 30,31 However, it underwent a phase separation forming an outer hematite layer during repeated redox cycles, which might decrease in the reactivity. 32 Recently, the mixed ionic-electronic conductors (MIECs)-supported oxygen carriers such as La 0.8 Sr 0.2 FeO 3-δ , La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3−δ or CaTi 1-x Fe x O 3-δ showed the higher redox activity in comparison with nonconductive and ionic-conductive materials.…”