摘要
以KF、KNO3、Ba(NO3)2、CsNO3为助剂前驱体,CeO2为载体采用氧化还原共沉淀法制备了一系列无氯负载型钌催化剂,考察了助剂种类和助剂含量及单双助剂对Ru/CeO2氨合成活性的影响,并采用N2物理吸附、CO脉冲吸附、XRD、XRF等表征手段,考察了助剂对Ru/CeO2催化剂比表面积、孔分布、钌分散度的影响。结果表明,F与碱金属、碱土金属一样可以促进Ru/CeO2催化剂的氨合成活性,四种单助剂中以CsNO3前驱体为助剂的促进效果最好,而对于双助剂Ba+Cs的促进效果最明显,在400℃,10 MPa,10 000 h-1反应条件下,出口氨浓度达到了13.3%。加入助剂后使各Ru/CeO2催化剂表面结构发生改变,但是催化剂的结构因素对氨合成活性的影响不明显,电子效应才是影响催化剂氨合成活性的主要因素。
A series of Ru based ammonia synthesis catalysts supported by ceria with different promoter precursors,such as KF、KNO3、Ba （NO3 ）2、 CsNO3、were prepared. Not only studied the effect of single and double promoters for the catalytic activity but also studied the effect of promoters＇ kinds and content. N2 physisorption, CO chemisorption and X-ray diffraction were carried out to investigate the effect of promoter on surface area, pore size distribution and ruthenium dispersion of catalysts. It has been found that the effectiveness of F ion just like the role of alkaline or alkaline-earth-promoter for ammonia synthesis. For the single-promoted Ru/CeO2 catalyst, cesium proved to be most effective in the studied four promoters. For the double-promoted one ,the activity of the catalyst was affected remarkably by cesium and barium co-exists. Ammonia synthesis concentration of over 13.3% was obtained over Ba＋Cs-Ru/CeO2 catalyst under 400 ℃ ,10 MPa and 10 000 h-1. The structure and the surface property of Ru/CeO2 catalyst were changed when promoters added. But the real factor to improving catalytic activity is electronic effect rather than structural factors.
出处
《燃料化学学报》
EI
CAS
CSCD
北大核心
2012年第7期848-854,共7页
Journal of Fuel Chemistry and Technology
基金
中国石油科技创新基金研究(2010D-5006-0502)
国家科技支撑计划(2007BAE08B02)
关键词
助剂
钌
氨合成
二氧化铈
promoter
ruthenium
ammonia synthesis
ceria
