Highly efficient subnanometer Ru-based catalyst for ammonia synthesis via an associative mechanism

doi:10.1016/j.cjche.2022.01.015

Abstract

Abstract: The industrial manufacture of ammonia (NH₃) using Fe-based catalyst works under rigorous conditions. For the goal of carbon-neutrality, it is highly desired to develop advanced catalyst for NH₃ synthesis at mild conditions to reduce energy consumption and CO₂ emissions. However, the main challenge of NH₃ synthesis at mild conditions lies in the dissociation of steady NN triple bond. In this work, we report the design of subnanometer Ru clusters (0.8 nm) anchored on the hollow N-doped carbon spheres catalyst (Ru-SNCs), which effectively promotes the NH₃ synthesis at mild conditions via an associative route. The NH₃ synthesis rate over Ru-SNCs (0.49% (mass) Ru) reaches up to 11.7 mmol NH₃·(g cat)^-1·h^-1 at 400 ℃ and 3 MPa, which is superior to that of 8.3 mmol NH₃·(g cat)^-1·h^-1 over Ru nanoparticle catalyst (1.20% (mass) Ru). Various characterizations show that the N₂H₄ species are the main intermediates for NH₃ synthesis on Ru-SNCs catalyst. It demonstrates that Ru-SNCs catalyst can follow an associative route for N₂ activation, which circumvents the direct dissociation of N₂ and results in highly efficient NH₃ synthesis at mild conditions.

Key words: Ammonia synthesis, Sustainability, Subnanometer Ru clusters, Associative route, Catalysis

摘要： The industrial manufacture of ammonia (NH₃) using Fe-based catalyst works under rigorous conditions. For the goal of carbon-neutrality, it is highly desired to develop advanced catalyst for NH₃ synthesis at mild conditions to reduce energy consumption and CO₂ emissions. However, the main challenge of NH₃ synthesis at mild conditions lies in the dissociation of steady NN triple bond. In this work, we report the design of subnanometer Ru clusters (0.8 nm) anchored on the hollow N-doped carbon spheres catalyst (Ru-SNCs), which effectively promotes the NH₃ synthesis at mild conditions via an associative route. The NH₃ synthesis rate over Ru-SNCs (0.49% (mass) Ru) reaches up to 11.7 mmol NH₃·(g cat)^-1·h^-1 at 400 ℃ and 3 MPa, which is superior to that of 8.3 mmol NH₃·(g cat)^-1·h^-1 over Ru nanoparticle catalyst (1.20% (mass) Ru). Various characterizations show that the N₂H₄ species are the main intermediates for NH₃ synthesis on Ru-SNCs catalyst. It demonstrates that Ru-SNCs catalyst can follow an associative route for N₂ activation, which circumvents the direct dissociation of N₂ and results in highly efficient NH₃ synthesis at mild conditions.

关键词: Ammonia synthesis, Sustainability, Subnanometer Ru clusters, Associative route, Catalysis

Yanliang Zhou, Qianjin Sai, Zhenni Tan, Congying Wang, Xiuyun Wang, Bingyu Lin, Jun Ni, Jianxin Lin, Lilong Jiang. Highly efficient subnanometer Ru-based catalyst for ammonia synthesis via an associative mechanism[J]. Chinese Journal of Chemical Engineering, 2022, 43(3): 177-184.

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