三元金属间化合物负载Ru催化剂的设计合成及其合成氨催化性能研究

As an important pillar of the national economy, ammonia synthesis has drawn great attention in both scientific community and industry. Synthesizing ammonia synthesis catalysts that work with excellent performance under mild reaction conditions is one of the most effective ways to reduce the production cost and improve the production safety for ammonia synthesis industry. The selection of suitable support materials is vital to Ru-based ammonia synthesis catalysts. For example, even thousandfold difference in catalytic activity could occur for two Ru-based catalysts with different supports. RTX (R = rare earth, T = transition metal, X = p-block element) ternary intermetallics, with more than 1,000 analogues, can be novel catalyst promoters for ammonia synthesis due to its unique properties of easily donating electrons and dissociating H2, and the reversible H2 soprtion ability. They could promote N2 dissociation of supported Ru and protect Ru particles from being poisoned by activated H. Besides, on account of the clear structures of RTX materials, it is convenient to construct Ru/RTX models to study the correlation between the electronic structure of RTX and the catalytic performance of Ru/RTX for ammonia synthesis by DFT calculations. Currently, there is few work concerning the application of RTX materials as supports for heterogeneous catalysis can be found. Here, we intend to prepare Ru catalysts supported on RTX materials and apply them for ammonia synthesis. The catalysts are expected to show extraordinary catalytic performance for ammonia synthesis under low reaction temperatures and pressures, and it is highly possible to achieve reliable relationship between the electronic structure of supports and the ammonia synthesis activity of Ru/support catalysts, which would guide the selection of novel catalyst supports for ammonia synthesis and other heterogeneous catalytic reactions.

合成氨工业是国民经济的重要支柱。低温低压合成氨催化剂的开发是降低合成氨工业成本、提高生产安全性的重要途径。合成氨催化剂载体在很大程度上决定了催化剂的性能。RTX类(R=稀土元素, T=过渡金属，X=p系元素)三元金属间化合物种类繁多，大部分RTX材料不仅结构稳定，还具有低功函、可逆吸脱氢性能。其作为催化剂载体可克服传统Ru催化剂上N2活化迟缓，H物种毒化的缺陷，因此有望合成高活性的低温低压催化剂。另外RTX材料结构明确，在不改变晶型的前提下，通过置换其中任意元素即可对载体的电子性质进行精确调控，有望通过研究得出载体的电子结构对合成氨催化反应的影响规律。目前，RTX材料作为载体用于非均相催化基本未受关注。本项目拟采用RTX类三元金属间化合物作为载体，制备Ru/RTX类催化剂并研究合成氨催化活性与载体结构的关系，旨在合成低温低压下的高活性催化剂并为负载型合成氨催化剂的载体选择提供理论指导。

RTX类(R=稀土元素, T=过渡金属，X=p系元素)三元金属间化合物种类繁多，大部分RTX材料不仅结构稳定，还具有低功函、可逆吸脱氢性能。其作为催化剂载体可克服传统Ru催化剂上N2活化迟缓，H物种毒化的缺陷，因此有望合成高活性的低温低压催化剂。RTX材料结构明确，在不改变晶型的前提下，通过置换其中任意元素即可对载体的电子性质进行精确调控，有望通过研究得出载体的电子结构对合成氨催化反应的影响规律。.受本项目资助，我们成功合成并研究了LaTMSi（TM=Fe，Co，Mn）系列四方相RTX材料作为载体用于催化合成氨研究。主要获得以下重要结果：（1） 合成了系列晶体结构一致，电子结构不同的高纯四方相RTX材料，为详细研究材料的电子;（2）证明了RTX系列材料都是电子化合物材料;（3）研究了RTX作为载体催化合成氨反应的性能、动力学，发现所研究系列LaTMSi材料都能够助力Ru改变传统合成氨反应的决速步，完全改变负载型催化剂的动力学;同时发现不同的RTX材料能大幅影响Ru催化剂的稳定性；（4）通过实验结合第一性原理计算揭示了RTX系列材料在合成氨反应中的作用本质，为相关载体的发展和发现提供了方向。.本项目发展了系列四方相RTX材料，并在此基础上揭示了RTX材料作为载体促进Ru合成氨催化性能的关键机制，对作为合成氨载体的三元金属间化合物乃至电子化合物的筛选和开发提供了理论指导和实践经验，为低温低压下高性能合成氨催化剂的开发具有重要的实际意义。