PREPARATION AND CHARACTERIZATION OF CO/SIO2, CO-MG/SIO2 AND MG-CO/SIO2 CATALYSTS AND THEIR ACTIVITY IN CO HYDROGENATION

Co/SiO2, Mg-Co/SiO2 and Co-Mg/SiO2 catalysts were prepared from acetate, nitrate or carbonyl precursors. The catalysts were characterized by XRD, XPS, SIMS and TGA. The activity and product distribution of the catalysts were evaluated in synthesis gas reactions at 0.5 MPa and 235-290 degrees C using 3 : 1 : 3 molar ratio of Ar : CO : H-2. The activity in CO hydrogenation decreased in the precursor order Co-2(CO)(8) > Co(NO3)2 > Co(CH3COO)(2), and the probability of chain growth decreased in the precursor order Co(NO3), > Co-2(CO)(8) > Co(CH3COO)(2). Alcohol yields were highest with Co-2(CO)(8) and lowest with Co(NO3)(2). Magnesium promotion influenced the catalyst activity and decreased the CO2 formation, but the promotion effects were less profound than those of the precursor. Surface studies on partially magnesium covered cobalt foil model catalysts suggested that magnesium promotes CO dissociation and chain growth, neither of which were, however, observed in the supported catalysts.