Abstract: The preparation chemistry of iron catalyst for ammonia synthesis is studied by molten method and X-ray diffraction. The chemical reaction and the change of crystal phase of iron oxide during the molten procedure is investigated according to Fe-O equilibrium diagram. The effect of solidifying-cooling rate of molten materials on the distribution of the promoters is exposed. It is indicated that Fe 2O₃ and stoichiometric ferrous oxide FeO is not able to be obtained by molten method at atmosphere; Fe₃O₄ or non stoichiometric magnetite Fe₃-yO₄ of n (O)/ n (Fe) in the range of 1.333-1.38 and the mixture oxide of Fe₃O₄ and FeOof n (O)/ n (Fe) in the range of 1.111-1.333 may be obtained by the same method ; but non-stoichiometric ferrous oxide expressed as Fe_{1- x} O or Wustite of n (O)/ n (Fe) in the range of 1.045- 1.111 may be obtained only when the cooling rate of molten materials is more than 20 ℃/min by molten method at atmosphere. There are observable influences of the solidifying cooling rate on the inhibition of the oxidation reaction and the disproportionation of the ferrous oxide Fe_{1- x}O and improvement of the distribution of the promoters.

Key words: Ammonia synthesis catalyst, Fe_1-x O, Preparation chemistry, Molten method