New Y(La)-M-O binary systems (M = Ca, Sr, or Ba): Synthesis, physicochemical characterization, and application as the supports of ruthenium catalysts for ammonia synthesis

The effect of the nature of the alkaline-earth metal on the phase composition and specific surface area of new Y(La)-M-O binary oxide compositions (M = Ca, Sr, or Ba) prepared by coprecipitation was studied. These systems were found to contain mixed compounds (M2Y2O5, MY2O4, and MLa2O4), which are different in thermal stability, in addition to individual La2O3 or Y2O3 phases. The Y(La)-M-O compositions calcined at 450degreesC were characterized by a more developed specific surface area, as compared with that of individual La2O3 or Y2O3. An increase in the calcination temperature to 650degreesC was accompanied by a decrease in the specific surface area of binary compositions. Catalysts prepared by supporting K-2[Ru-4(CO)(13)] onto the Y(La)-M-O systems were active in ammonia synthesis at 250-400degreesC and atmospheric pressure. The most active of these catalysts, K-2[Ru-4(CO)(13)]/Y-Ba-O, provided a higher yield of NH3 at 250-300degreesC than analogous catalysts prepared with the use of well-known supports (Sibunit, CFC-1, and C/MgO).