Effect of MgO Support and BaO Promoter on Structure and Catalytic Activity of Ruthenium Catalysts for Ammonia Synthesis

A series of Ba-Ru/MgO catalysts were prepared by the impregnation method using commerical(mark as MgO-1) and synthesized MgO(mark as MgO-2) as the support,respectively.The catalysts were characterized by XRD,TG/DSC,N 2 adsorption-desorption,TEM,H 2 TPR and CO 2 TPD.The effect of MgO support and BaO promoter were investigated on the phase structure,texture structure and morphology,reduction process of ruthenium particles,surface properties and catalytic activity in ammonia synthesis.The results indicate that the physical and chemical properties of MgO support have a strong impact on the structure and activity of ruthenium catalyst.The specific surface area and total basic sites number of MgO-2 was higher than that of MgO-1,Ru particles supported over the surface of MgO-2 was about 2 nm and easy to be reduced.When the molar ratio of n Ba ∶n Ru was 1.0,weak basic sites appeared over the surface of Ba-Ru(1 ∶1)/MgO-2,which greatly promoted the ammonia synthesis rate.The ammonia synthesis activity was 15.40 L·g-1 Ru ·h-1 at 3.0 MPa、5 000 h-1 and 400 ℃ for Ba-Ru(1∶1)/MgO-2,which was higher than that of Ba-Ru/MgO-1 catalysts at the same conditions.