Deactivation of Modified Iron Oxide Materials in the Cyclic Water Gas Shift Process for CO-Free Hydrogen Production

The iron oxide Fe 2 O 3 is a potential oxygen storage material for the production of hydrogen in the cyclic water gas shift (CWGS) reaction. The deactivation of modified iron oxides during repeated reduction and reoxidation cycles was investigated. Sintering was found to be the main reason for deactivation during the CWGS cycles. The influence of CeO 2, La 2 O 3, and Ce 0.5 Zr 0.5 O 2 as promoters in the system was investigated, as well. CeO 2 - or La 2 O 3 -promoted iron oxide deactivated significantly during the progression of the redox cycles due to the solid−solid transformation of oxide structures (CeFeO 3 or LaFeO 3 ) which had a lower oxygen capacity. Iron oxide promoted by Ce 0.5 Zr 0.5 O 2 showed high stability and activity in the CWGS process. The influence of the Fe 2 O 3 −Ce 0.5 Zr 0.5 O 2 oxide composition ratio and the effect of Mo, Cu, and Mg metal additives on the lifetime stability and activity have been declared. A sample containing 80 wt % Fe 2 O 3 gave the highest activity during the reduction and reoxidation cycles compared to the other oxide composition ratios. The Mo species impregnated on Fe 2 O 3 −Ce 0.5 Zr 0.5 O 2 inhibited the interaction between iron oxide particles during the redox cycles and resulted in mitigated sintering of the iron species. The Mo-impregnated sample was stable over 100 redox cycles.