(622b) Novel Ferrite Materials for H2 Production Using Chemical Looping

Weimer, A. W., University of Colorado at Boulder

The chemical looping hydrogen (CLH) production process is an alternative method to water-gas shift to generate pure H2, as well as a separate stream of pure and easily-sequestered CO2, from any synthesis gas without complicated and expensive separations equipment.  Synthesis gas is used to reduce a metal oxide material at moderate to high temperatures as it leaves a gasifier (500°C to 800°C), producing a stream of CO2 and H2O.  The resulting reduced metal is then oxidized with H2O to produce H2 and regenerate the metal oxide.  This process requires use of a metal oxide material that achieves high H2 and CO conversions to H2O and CO2 during the reduction step.  Complete regeneration of the metal oxide using only H2O as an oxidant is also desirable.   In this study, the mixed metal ferrites CoFe2O4 and NiFe2O4 have been investigated as metal oxide candidates for the CLH process.  The ability of these ferrites to oxidize H2 and CO in the syngas to H2O and CO2 during the reduction step was compared to that of the Fe2O3 in a packed bed reactor and found to be nearly equivalent. Unlike Fe2O3, the mixed metal ferrites were regenerated with H2O oxidation only, allowing all the H2 and CO used during the reduction step to be recovered as H2 during oxidation.  Experimental results also show the H2 production capacity of the reduced ferrites to be much greater than that of the Fe2O3 per cycle under the same conditions.  Long-term cyclability tests showed the CoFe2O4 material to cycle with great consistency.