Anionic ruthenium cluster K2[Ru4(CO)13] as precursor of catalytically active ruthenium particles and potassium promoter.: New efficient ammonia synthesis catalysts based on supported K2[Ru4(CO)13]

New efficient potassium-promoted catalysts for ammonia synthesis are reported. For preparation of the catalysts, anionic ruthenium cluster K-2[Ru-4(CO)(13)] was used as a precursor of both catalytically active metal particles and potassium promoter while magnesium oxide and new original graphite-like active carbon CFC-1 were employed as supports. The catalysts found are capable of catalysing the ammonia synthesis starting from 250 degrees C (1 atm) and exceed markedly in their activity at 300-400 degrees C and atmospheric pressure the industrial ammonia synthesis catalyst (SA-1). Especially effective is the K-2[Ru-4(CO)(13)] catalyst on MgO. The replacement of MgO by gamma-Al2O3 and SiO2 results in a sharp decrease in activity of the catalyst in ammonia synthesis. This indicates the importance of the basic properties of a support for the achievement of high ammonia synthesis rates. (C) 1998 Elsevier Science B.V. All rights reserved.