Effect of high-temperature treatment of on the activity of Ru-Cs(Ba)/Sibunit catalysts in ammonia synthesis and their resistance to methanation

Ru-Cs(Ba)/Sibunit catalysts with the molar ratio Cs(Ba):Ru = 2.5 were synthesized using the carbon composite Sibunit calcined at 1400, 1600, 1800, 2000 and 2200 degrees C. Activity of the promoted catalysts in ammonia synthesis and their thermal stability to methanation were compared. Substantial changes in the structure and properties of Sibunit during its calcination were shown to affect the activity of the synthesized catalysts. As the calcination temperature was raised, specific surface (S-sp) decreased considerably, the carbon structure became ordered, whereas the specific activity (W-sp) increased. Thus, Wsp at 400 degrees C for Cs-Ru/Sib1400 was equal to 0.107 mol NH3.gRu(-1).h(-1), while for Cs-Ru/Sib2200 - 0.591 mol NH3.gRu(-1).h(-1). It was found that elevation of the calcination temperature and introduction of barium significantly enhanced thermal stability of the samples - the carbon loss decreased up to 10 times.