Nonoclusters of iron prepared by different methods and analyzed by various spectroscopic techniques

Two different preparative methods for loading zeolites with zerovalent iron clusters are compared: in the first case Fe(CO)₅ is adsorbed by NaX zeolite at low temperatures and decomposed under vacuum conditions up to 673 K. The iron clusters inside the cages of the zeolite are investigated by ferromagnetic resonance and Mössbauer spectroscopy. The second case deals with a sample prepared by ion exchange of NaA zeolite by means of a calculated amount of ferrous ions followed by reduction under an excess of sodium vapor at 573 K. Here the iron clusters are analyzed by Mössbauer and magnetization measurements. In both cases cluster composition and cluster sizes are comparable. The clusters are termed “nanoclusters” because their diameter is in the nanometer range ( 2 nm). We propose using these clusters for Fischer-Tropsch reactions, and we have achieved promising preliminary results.