Desorption of prtassium from the industrial iron catalysts form ammonia synthesis and the reference compound KAlO_2 was monitored by surface ionisation detection. Activation energies for desorption are cllse to each other with in the narrow range 1.7-1.8 eV: for KAlO_2, for Polish industrial catalyst PS3-INS boiled in water and for its precursor kept in moist amosphere for two years. The coincidence includes also literature values for the industrial catalyst AS-4 de-activated by usage in an industrail reactor for five years. The data obtained confirm the concept by Somorjai that formation of potassium aluminate implies the deactivation of iron catalysts.
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