The effect of addition of ZrO₂ to Fe₂O₃ for hydrogen production by chemical looping

In this paper, a synthetic mixture of ZrO₂ and Fe ₂O₃ was prepared by coprecipitation for use in chemical looping and hydrogen production. Cycling experiments in a fluidized bed showed that a material composed of 30 mol % ZrO₂ and 70 mol % Fe ₂O₃ was capable of producing hydrogen with a consistent yield of 90 mol % of the stoichiometric amount over 20 cycles of reduction and oxidation at 1123 K. Here, the iron oxide was subjected to cycles consisting of nearly 100% reduction to Fe followed by reoxidation (with steam or CO ₂ and then air) to Fe₂O₃. There was no contamination by CO of the hydrogen produced, at a lower detection limit of 500 ppm, when the conversion of Fe₃O₄ to Fe was kept below 90 mol %. A preliminary investigation of the reaction kinetics confirmed that the ZrO₂ support does not inhibit rates of reaction compared with those observed with iron oxide alone.