焙烧气氛对Ba-Ru/MgO催化剂氨合成性能的影响

摘要

采用浸渍法制备Ba-Ru/MgO系列催化剂,考察不同焙烧气氛对Ba-Ru/MgO催化剂氨合成性能的影响,通过X射线衍射、N2-低温物理吸附、透射电镜、H2程序升温还原、CO2程序升温脱附和红外光谱等方法对其进行表征,考察焙烧气氛对负载型钌基氨合成催化剂的物相结构、织构性能、微观形貌、钌物种的还原性能和体系酸碱性能等影响.研究表明,MsO焙烧气氛对制备的钌基氨合成催化剂结构、物化性能以及氨合成活性有较大影响,不同气氛焙烧对Ba-Ru/MgO催化剂碱性强弱影响顺序:Ba-Ru/MgO(Ar)＞Ba-Ru/MgO(N2)＞Ba-Ru/MgO(空气)＞Ba-Ru/MgO(真空),在450℃、5.0MPa和5000h-1条件下,空气、Ar和N2气氛焙烧的MgO制备的Ba-Ru/MgO催化剂活性高于真空气氛焙烧的MgO制备的催化剂.%Ba-Ru/MgO catalysts were prepared by impregnation method. The effects of calcination atmos phere on the properties of Ba-Ru/MgO catalysts for ammonia synthesis were investigated. The phase struc ture , texture structure performance, the morphology, reduction properties of ruthenium species, surface acidity and basicity of the catalysts were characterized by means of XRD,N2 adsorption-desorption,TEM, H2-TPR,CO2-TPD and FT-IR. The results indicated that the calcination atmosphere for MgO support had great influence on the structure, physicochemical properties and ammonia synthesis activity of Ba-Ru/MgO catalysts. The basicity of Ba-Ru/MgO catalyst decreased in sequence as follows; Ba-Ru/MgO ( Ar) > Ba-Ru/MgO(N2) >Ba-Ru/MgO(Air) > Ba-Ru/MgO( vacuum). Under the condition of 450 ℃,5.0 Mpa and 5 000 h-1 ,the ammonia synthesis activity of Ba-Ru/MgO catalysts with MgO supports prepared under the calcination atmosphere of air, Ar and N2 was higher than that of Ba-Ru/MgO with MgO support prepared under the calcination atmosphere of vacuum.