Existent state of ZrO2 in fused iron catalyst and its influence on the reactivity of the catalyst

XRD. LRS, thermogravimetric technique. BET surface area determination and catalytic activity measurements have been used to investigate the existent state of ZrO2 in the fused iron catalyst with and without Y2O3 and the influence of them on the reactivity of fused iron catalyst for ammonia synthesis. The results of XRD and LRS show that zirconia exists in the form of yttria-stabilized cubic ZrO2 in the fused iron catalysts with Y2O3. We also found that for the Y2O3-free fused iron catalysts, cubic phase zirconia can also be stabilized by incorporating Fe2+ or Fe3+ cations into its lattice, and Fe2+-stabilized zirconia is more stable than Fe3+-stabilized zirconia. The results of a I eduction experiment indicate that Y2O3 has a promoting effect on the reduction of ZrO2-promoted fused iron catalyst. The catalyst containing Y2O3 and ZrO2 exhibits a higher activity than a current industrial catalyst. The role of zirconia and yttria was also discussed in this work. (C) 1998 Elsevier Science S.A.