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 °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 (Ssp) decreased considerably, the carbon structure became ordered, whereas the specific activity (Wsp) increased. Thus, Wsp at 400 °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. [Display omitted] •Carbon support with more ordered structure was produced by high-temperature treatment of initial carbon material Sibunit.•The increase in the temperature of Sibunit calcination leads in the rise of carbon structure ordering effect.•The carbon support structure ordering is favorable for specific activity and stability to methanation for Ru-Ba/Sibunit ammonia synthesis catalyst.•Ru-Cs(Ba)/Sib2200 catalysts are 3 times more active than Ru-Cs(Ba)/Sib20 catalysts, with a 10-fold reduced ruthenium content.