DECOMPOSITION OF CO2 TO CARBON BY H-2-REDUCED NI(II)- AND CO(II)-BEARING FERRITES AT 300-DEGREES-C

Ni(II)- and Co(II)-bearing ferrites with different levels of metal substitution have been studied for CO2 decomposition. Ni2+ and Co2+ have been substituted for Fe2+ or Fe3+ in magnetite with the spinel type of crystal structure up to 14% and 26% for the mole ratio of Ni2+ and Co2+ to the total Fe contents, respectively. The metal substitution was corroborated by Mossbauer spectroscopy and XRD studies. They were activated in a flow of HZ gas to form oxygen-deficient ferrites with the spinel structure retained. The oxygen-deficient M(II)-bearing ferrites have been found to show high reactivity toward CO2 decomposition to carbon at 300 degrees C. The reactivity increased with the level of metal substitution and activation. The oxygens of CO2 were incorporated into the spinel structure and carbon was deposited on the surface of the ferrites. The deposited carbon was visible on dissolution of the ferrites used. The rate of decomposition on H-2-activated Ni(II)-bearing ferrite with the mole ratio of 14% was 30 times as high as that of H-2-activated magnetite.