Ammonia Synthesis over Ruthenium Catalysts Using Barium-Doped Zirconia as Supports Prepared by Citric Acid Method

Barium-promoted zirconia (Ba-ZrO2) was synthesized by the citric acid method and used as supports for Ru/Ba-ZrO2 catalysts, which were prepared by incipient wetness impregnation with K2RuO4 as precursor. The obtained Ba-ZrO2 and catalysts were characterized by X-ray diffraction and CO2 temperature-programmed desorption. The effect of Ba content on the structure and catalytic activity of K-Ru/Ba-ZrO2 catalysts is discussed. The formation of BaZrO3 can improve significantly the catalytic activity of Ru/Ba-ZrO2 for ammonia synthesis. The ammonia concentration and rate of ammonia synthesis of the K-Ru/Ba-ZrO2 catalyst (molar ratio of Ba: Zr is 1:1) were 9.24% and 29.77 mmol/(g·h), respectively, at 425°C, 5.0 MPa, and 10000 h−1. Improvements in electron conductivity and the basic nature of the catalyst may be the main reasons for such high catalytic activity in ammonia synthesis.

摘要采用柠檬酸络合法制备了一系列不同含量 Ba 掺杂的 ZrO2, 再用浸渍法制备了 K-Ru/Ba-ZrO2 催化剂并将其用于氨合成反应. 采用 X 射线衍射和 CO2 程序升温脱附技术考察了 Ba 含量对催化剂结构与性能的影响. 结果表明, Ba 掺入 ZrO2 后形成的 BaZrO3 有助于其负载的 Ru 催化剂氨合成活性的显著提高. 在 5.0 MPa, 10000 h–1, 425 °C 时, Ru/Ba-ZrO2 (Ba:Zr 摩尔比为 1:1) 催化剂活性最高, 出口氨浓度和反应速率分别达 9.24% 和 29.77 mmol/(g·h). 这主要归因于载体的强电子传导性能和碱性提高. 

Graphical abstractRu/Ba-ZrO2 was an excellent catalyst for ammonia synthesis especially under mild conditions. This was attributed to the presence of BaZrO3 with high basicity and ability to conduct electrons.Figure optionsDownload full-size imageDownload as PowerPoint slide