The effect of alkali metals on the surface area of iron catalyst for ammonia synthesis

The surface area of the iron catalyst for ammonia synthesis impregnated with lithium, sodium, potassium and cesium was examined. The concentration of the respective element (expressed in mole fraction) in the bulk of the catalyst sample was varied from near zero to 1.5-10~3. The increase in the concentration of the promoter led to the decrease of the surface area of the catalyst regardless of the element present in the bulk. The exponential equation has been proposed to describe this dependence. The empirical factor AM o from the mentioned equation, which differs from element to element, was correlated with the difference between the formation enthalpy of A12O3 and the respective alkali metal oxide. The observed dependence obeys a linear law.