RUTHENIUM CLUSTER-DERIVED CATALYSTS FOR AMMONIA-SYNTHESIS

Ruthenium supported on gamma-alumina modified with KOH was tested as c atalyst for ammonia synthesis under atmospheric pressure. Ru-3(CO)(12) and RuCl3 were compared as ruthenium precursors. The catalysts derive d from Ru-3(CO)(12) exhibited an up to five times higher productivity than the corresponding ones derived from RuCl3. Ruthenium metal disper sion, which probably influences the catalytic activity, was measured b oth by carbon monoxide and hydrogen chemisorption tests, and observed by high resolution transmission electron microscopy (HRTEM), and was c learly higher in the case of the ruthenium cluster. Different rutheniu m catalysts, with 2, 5, 8 and 10% metal and 30% potassium (added as KO H) on alumina, were prepared from Ru-3(CO)(12). The highest hourly pro ductivity of ammonia, both referred to unit mass of the catalyst and t o the ruthenium atom content, was obtained with 8% Ru/Al2O3-KOH at 623 K and atmospheric pressure.