Y-Zeolites Loaded with Iron Carbonyl Complexes: Activity and Selectivity in CO + H2 Conversion

Publisher Summary Thermodynamic considerations and experimental evidence indicate that by using CO + H 2 mixtures as reactants, a broad range of molecules can be produced, including alcohols, acids, aromatic hydrocarbons, alkanes, and alkenes with either linear or branched skeleton. This situation leads to a major problem area: CO/H 2 synthesis-product selectivity. Today, one of the main objectives is the development of new catalyst systems, which promote the more desirable products such as low-molecular-weight hydrocarbons. The chapter focuses on the determination of the composition and the structure of the active catalyst on the atomic scale. The results described in this chapter highlight that molecular iron complexes are valuable candidates to introduce Fe(O) particles into zeolites provided that no acidity is present. According to this procedure, iron-zeolites are catalyst precursors in the Fischer–Tropsch synthesis. They behave as conventional ones if the effect of temperature and the CO/H 2 ratio upon the C 1 –C 3 , C 3 + fraction and the alkene/alkane ratio is taken into consideration. The originality of the Fe 3 (CO) 12 –NaY adduct lies in the upper limit of the chain length of the hydrocarbons formed. Hydrocarbons higher than C 9 are only produced in trace amounts. The key parameter for selective Fischer–Tropsch synthesis is in the formation and stabilization of small aggregates. Nevertheless, the selectivity can be shifted toward C 4 –C 5 in promoting side reactions such as cracking by the addition of acidic supports.