The exchange of H218O with the oxygen of promoters on the surface of iron catalysts

The oxygen content of promoter oxides or other metallic oxide on the surface of iron synthetic ammonia catalysts has been estimated by a method involving equilibration with a known quantity of H218O in hydrogen at 450 °C. The results indicate a surface coverage by promoters of about 60% for a catalyst containing 1.06% Al2O3 and 0.52% K2O. With reasonable assumptions in regard to the cross sectional area of oxygen ions the coverage agrees with that estimated from the chemisorption of carbon monoxide at −195 °C on the same catalyst. A pure iron catalyst revealed only a 1.2% coverage with oxygen after extended reduction at 450 °C.