碱土金属对锆基钙钛矿材料负载钌催化剂氨合成性能的影响

Effect of alkali earth metals on performance of zirconium-based perovskite composite oxides supported ruthenium for ammonia synthesis

采用柠檬酸络合法制备了含Ca,Sr和Ba的锆基钙钛矿材料,负载Ru后用于催化氨合成反应;研究了碱土金属对催化剂织构性能和载体材料表面碱性的影响,并与催化剂活性相关联.同时,采用程序升温脱附技术对催化剂表面H2脱附性能进行了表征.结果显示,碱土金属对催化剂活性的促进顺序为Ba>Sr>Ca.研究发现,不同锆基碱土金属钙钛矿材料表面均具有较强的碱性位,碱土金属的加入影响了载体碱性强度以及金属-载体的相互作用,其中BaZrO3可有效抑制H2的吸附.因此,Ru/BaZrO3催化剂表现出优异的氨合成活性.

Zirconium-based perovskite materials with different alkaline earth metals were synthesized by the citric acid method and used as supports for ruthenium catalysts to catalytic ammonia synthesis reaction. The effects of alkaline earth metals on the texture properties, basicity, and catalytic activity were discussed. Additionally, the desorption properties of H2 on the surface of various catalysts were characterized by temperature-programmed desorption.The results showed that there were lots of strong basic sites appeared on the Ca, Sr, and Ba perovskite-style supports, andthe order of activity wasBa>Sr>Ca. The addition of different alkaline earth metals not only affected the electron donating ability but also influenced the metal-support interaction as well as the adsorption-desorption properties of these catalysts. The adsorption of H2 was inhibited significantly by the presence of BaZrO3 and increased the number of active sites for dissociatively adsorbed N2 which may be the major reason why the Ru/BaZrO3 catalyst exhibited so high activity for ammonia synthesis.