EFFECT OF PRELIMINARY HEATING ON THE ACTIVATION OF MODEL IRON CATALYST FOR AMMONIA-SYNTHESIS .2. STRUCTURAL-CHANGES LEADING UP TO THE NUCLEATION PROCESS

Microscopic and microprobe studies of significantly active, fused mode l iron catalysts with increased amounts of wustite are reported. The c atalysts were examined in untreated form and after annealing. Two type s of magnetite (isometric and lamellar) were found. A definite influen ce of the annealing on the relative content of both magnetites was obs erved. In the annealed sample a third kind of magnetite (enriched in i ron) was found. The creation of iron nuclei in the catalyst precursor is discussed and an suitable model is proposed.