Comparative study of Ba, Cs, K, and Li as promoters for Ru/La2Ce2O7-based catalyst for ammonia synthesis

Ammonia is one of the promising carriers for hydrogen and a critical ingredient in many industries including fertilizers and pharmaceuticals. In the KAAP process, ruthenium- (Ru-) based catalysts showed 10-20 more activity compared with iron- (Fe-) based catalysts. The modifications that are applied to Ru-based catalysts revolve around changing the material of its support and/or promoters. This study compares the performance of a Ru-based catalyst for ammonia synthesis supported by La2Ce2O7 using barium (Ba), cesium (Cs), potassium (K), and lithium (Li) as promoters. Based on structural, physicochemical, adsorption, and electronic state analysis, the Cs-promoted catalyst is expected to perform best among all the promoted catalysts, while our findings suggest that the K-promoted catalyst performed the best in the actual catalytic reaction. This result will affect the development of Ru/La2Ce2O7-based catalysts, especially in ammonia synthesis at different temperatures and pressures.