不同MgO担体对Ba-Ru/MgO氨合成催化剂物化性质和反应性能的影响(英文)  

Effect of Different Supports on Physical and Chemical Properties and Catalytic Activity over Ba-Ru/MgO Ammonia Synthesis Catalysts

作　　者：杨晓龙[1] 唐立平[1,2] 夏春谷[1] 熊绪茂[1] 慕新元[1] 胡斌[1] 

机构地区：[1]中国科学院兰州化学物理研究所羰基合成与选择氧化国家重点实验室,甘肃兰州730000 [2]中国科学院研究生院,北京100049

出　　处：《分子催化》2012年第1期1-9,共9页Journal of Molecular Catalysis(China)

基　　金：supported by the National Science Foundation for Distinguished Young Scholars of China(20625308)

摘　　要：采用不同沉淀剂制备了MgO材料,以其为载体制备了Ba-Ru/MgO氨合成催化剂,考察了沉淀剂种类和BaO助剂对其氨合成性能的影响.通过X射线衍射(XRD)、N2物理吸附、X射线荧光光谱(XRF)、透射电镜(TEM)、H2程序升温还原(H2-TPR)、CO2程序升温脱附(CO2-TPD)、H2程序升温脱附(H2-TPD)和N2程序升温脱附(N2-TPD)表征手段,对不同沉淀剂影响Ba-Ru/MgO催化剂氨合成性能的原因进行了探索.结果表明:采用(NH4)2CO3作沉淀剂制备的Ba-Ru/MgO催化剂表面Ru物种易于在低温下还原,催化剂表面在低温区具有较多数量的弱碱性吸附位,在450℃、5.0 MPa和5 000 h-1条件下,由(NH4)2CO3做沉淀剂制备的Ba-Ru/MgO催化剂活性最高,出口氨浓度为3.74%.BaO助剂的加入大大减少了Ba-Ru/MgO催化剂表面吸附氢的数量,增大表面脱附氮的数量,从而易于N2解离吸附,提高氨合成反应速率.MgO supports were prepared by different precipitants and further examined as the supports for barium-promoted ruthenium catalyst for ammonia synthesis.The reason resulting in their difference of catalytic activity were explored by X-ray diffraction,N2 adsorption-desorption,X-ray fluorescence spectroscopy,transmission electron microscopy,H2 temperature-programmed reduction,CO2 temperature-programmed desorption,H2 temperature-programmed desorption and N2 temperature-programmed desorption.It was found that MgO prepared by（NH4）2CO3 precipitant facilitated the reduction of ruthenium oxide for Ba-Ru/MgO catalyst,and the weak basic sites of Ba-Ru/MgO（（NH4）2CO3 as precipitant） appeared at lower temperature and showed higher weak basic site densities compared with the others.At 450 ℃、 5.0 MPa and 5 000 h-1,catalytic activity of Ba-Ru/MgO catalyst employing（NH4）2CO3 as the precipitant was higher than that of the catalyst prepared by other precipitants under the same reaction conditions,the ammonia concentration in the effluent reached 3.74%.The addition of Ba promoter significantly decreased the amount of hydrogen chemisorption,increased the number of dissociatively adsorbed N＊ on the Ru surface and thus accelerated the reaction rate of ammonia synthesis.

关 键 词：氨合成 钌催化剂 沉淀剂 碱性位 

分 类 号：O643.3[理学—物理化学] TQ113.2[理学—化学]