Montmorillonite-Supported Iron Oxide for Hydrogen Storage by Chemical Looping

A technology for hydrogen storage is proposed based on the repeated reduction of magnetite (Fe 3 O 4 +4 H 2 →3 Fe+4 H 2 O) and the oxidization of metallic iron (3 Fe+4 H 2 O→Fe 3 O 4 +4 H 2 ). Herein, we prepared three montmorillonite (MMT)-supported iron oxide samples by using a sol–gel method and demonstrated their application in hydrogen storage through a chemical looping process. The redox performance of the Fe-MMT samples was studied at 600 °C in a fixed-bed reactor. The results showed that 70 Fe-MMT (with 70 wt % Fe 2 O 3 ) exhibited relatively good redox performance owing to its excellent anti-agglomeration ability and sintering resistance. After the redox performance tests, Fe 2 SiO 4 was observed in all Fe-MMT samples. It was worth noting that the diffraction intensity of Fe 2 SiO 4 in 70 Fe-MMT was much weaker than in 30 Fe-MMT (30 wt % Fe 2 O 3 ) and 50 Fe-MMT (50 wt % Fe 2 O 3 ), which was owed to the high MMT content in the 30 Fe-MMT and 50 Fe-MMT samples. The formation of Fe 2 SiO 4 in repeated redox cycles could reduce the stability and recyclability of Fe-MMT samples. This might be the major reason for the better hydrogen storage performance of 70 Fe-MMT compared with 30 Fe-MMT and 50 Fe-MMT.