Jacek Przemysław Rogowski oral presentation (SN1-Fri2-2-1)
TOF-SIMS study of the morphology and chemical composition of the iron catalyst for ammonia synthesis and its wustite-based precursor
Lodz University of Technology Faculty of Chemistry Institute of General and Ecological Chemistry - Lodz University of Technology Faculty of Chemistry Institute of General and Ecological Chemistry, ul. Żeromskiego 116, 90-924 Łódź, Poland
The industrial process of ammonia synthesis introduced at the beginning of the twentieth century was based on the use of iron catalyst. Since then, many studies were devoted to improving iron catalyst activity. Most of these research concerned iron catalyst obtained from magnetite and was focused in finding the appropriate type and composition of the catalyst promoters . However, the application of wustite-based precursor resulted in the development of the iron catalyst with 10 - 37 % higher activity than that of the conventional ammonia synthesis catalysts obtained from the magnetite precursor [2, 3].
In this study the morphology and chemical composition of the ammonia synthesis iron catalyst and its wustite precursor were investigated using secondary ion mass spectrometry (TOF-SIMS). It was shown that the wustite-based precursor of iron catalyst is composed of wustite grains separated by intergranular spaces with high amount of promoters: K2O, Al2O3 and CaO (Fig. 1).
The TOF-SIMS analysis evidenced that beside intergranular spaces aluminum and calcium are also present in the wustite grains. The amount of calcium, aluminum and potassium in the wustite phase decreases in the sequence Ca > Al > K. It was shown that the surface of the reduced catalyst is covered with the layer containing promoters atoms with predominant potassium contents. Moreover, it was evidenced that annealing of the iron catalyst precursor above 350ºC leads to the efficient wetting of the wustite surface with potassium.
 H.Z. Liu, Ammonia synthesis catalyst 100 years: Practice, enlightenment and challenge, Chinese Journal of Catalysis, 35 (2014) 1619-1640.
 H.Z. Liu, X.N. Li, Z.N. Hu, Development of novel low temperature and low pressure ammonia synthesis catalyst, Applied Catalysis a-General, 142 (1996) 209-222.
 N. Pernicone, E. Ferrero, I. Rossetti, L. Forni, P. Canton, P. Riello, G. Fagherazzi, M. Signoretto, F. Pinna, Wustite as a new precursor of industrial ammonia synthesis catalysts, Applied Catalysis a-General, 251 (2003) 121-129.