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

Abstract

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.