Fundamental Study of Preparation Method of Ruthenium-Potassium and Osmium-Potassium Catalysts for Ammonia Synthesis

Abstract

The preparation methods of Ru-AC (active carbon)-K and Os-AC-K catalysts for ammonia synthesis were examined. The catalytic activity of Ru-AC-K increased linearly with the potassium content above 1 mmol/g-cat. below which no activity was found (Figs 1 and 7). About 6 times as much as the stoichiometric amount of hydrogen was consumed during reduction of RuCl3 on AC (Fig. 2), whereas the catalytic activity was indepenent of the extent of hydrogen consumption. Although hydrogen chloride was formed during the reduction, about 20% of chloride ion remained on the catalyst. The activity of Ru-AC-K was roughly proportional to the amount of CO chemisorption on Ru-AC (Figs 3 and 6), which increased linearly with Ru content, attaining a plateau value above 3 wt % (Fig. 5), and was unaffected by pretreatments of AC with HNO3 and/or NH4OH (Table 1, Figs 5, 6 and 7). RuCl3 was almost completely adsorbed on the active carbon during the preparation of low Ru-content catalysts (Fig. 4). The specific activity of supported metals was independent of the oxidation state of starting material of Ru(II, N) or Os(III, N, VI, VII). © 1976, The Chemical Society of Japan. All rights reserved.