Improvement in ammonia synthesis activity on ruthenium catalyst using ceria support modified a large amount of cesium promoter

A supported ruthenium catalyst (Ru/Cs⁺/CeO₂) for ammonia synthesis is described which incorporates a large amount of a Cs⁺ promoter in a porous CeO₂ support to enhance the electron donation effect of the alkali promoter on the ruthenium catalyst. Optimization of the Ru and Cs⁺ promoter contents improves the ammonia synthesis rate to more than 4 times that of the benchmark catalyst (Cs⁺/Ru/MgO) at 350 °C and 0.1 MPa, and the ammonia synthesis rate is stable for 100 h. Introduction of the Cs⁺ promoter into the support before the Ru impregnation increases the particle size of the Ru catalyst. Despite a decrease in the number of active sites, the TOF of the catalyst is more than 50 times that of Ru (2 wt%)/CeO₂. CO adsorption measurements suggest an electron donating effect by the Cs⁺ promoter to ruthenium metal. Reaction order analysis indicates this is due to a mitigation of hydrogen poisoning.