Investigation on Deactivation of K‐promoted Ru Catalyst for Ammonia Synthesis by CO Formation

• Published in: ChemistrySelect (Weinheim) 2020-06, Vol.5 (22), p.6639-6645
• Main Authors: Ni, Jun, Ran, Haiyun, Lin, Jianxin, Wang, Xiuyun, Lin, Bingyu, Jiang, Lilong
• Format: Article
• Language: English
• Subjects: Ammonia synthesis; Carbon; Deactivation; Oxidation; Ruthenium
• ISSN: 2365-6549; 2365-6549
• DOI: 10.1002/slct.202000772

The prevailing view of the deactivation of carbon‐supported Ru catalyst in ammonia synthesis is carbon methanation, but those strategies focusing on inhibiting carbon methanation cannot effectively solve the challenge of Ru/C catalysts. Herein we prepared four K‐promoted Ru catalysts with different Ru loadings and treated the samples at 450 or 500 °C under 1 MPa during ammonia synthesis reaction. The result showed that the presence of a larger amount of Ru species enhanced methane formation at the reaction temperature, which was irrelevant to the loss in activity of ammonia synthesis. On the contrary, CO formation along with a great decline in catalytic activity can be observed when Ru catalysts are heated at 500 °C. The characterization results indicated that the severe depletion of surface oxygen groups following the CO‐formation pathway, resulting in the notable decrease in the amount of gas adsorption, contributed to the deactivation of carbon‐supported Ru catalyst. The prevailing view of the deactivation of carbon‐supported Ru catalyst in ammonia synthesis is carbon methanation. However, the change in the Ru loading affected methane formation at the reaction temperature, which was irrelevant to the loss in activity of ammonia synthesis. On the contrary, the severe depletion of surface oxygen groups following the CO‐formation pathway, resulting in the notable decrease in the amount of gas adsorption, contributed to the deactivation of carbon‐supported Ru catalyst.