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

• Published in: International journal of hydrogen energy 2022-01, Vol.47 (4), p.2433-2441
• Main Authors: Osozawa, Mami, Hori, Ayane, Fukai, Kosuke, Honma, Tetsuo, Oshima, Kazumasa, Satokawa, Shigeo
• Format: Article
• Language: English
• Subjects: Ammonia synthesis; Ceria support; Cesium promoter; Electron donation; Energy carrier; Ruthenium catalyst
• ISSN: 0360-3199; 1879-3487
• DOI: 10.1016/j.ijhydene.2021.10.204

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. [Display omitted] •Cs+ promoter was modified into CeO2 support before the impregnation of Ru catalyst.•Significant improvement of NH3 synthesis rate was realized by Ru/Cs+/CeO2 catalyst.•The NH3 synthesis rate was 4 times higher than that of the benchmark catalyst.•Electron donation from Cs+ promoter contributes to the catalytic performance.•The catalytic activity of the catalyst was stable for 100 h.