摘要
研究了稀土金属氧化物La2O3,CeO2,Pr2O3,Nd2O3和Sm2O3对Ru-Ba/堇青石催化剂的活性的影响。利用BET,BJH,SEM,XRD,CO化学吸附等测试手段对催化剂进行表征,并对催化剂的反应性能进行评价。SEM测试结果显示La2O3呈“虫卵状”聚集在堇青石表面,而CeO2呈立方CaF2型均匀的覆盖在堇青石表面,Ru粒子呈“孤岛状”均匀地分散在铈改性的堇青石载体表面。堇青石载体经CeO2改性后,催化剂的比表面积、比孔容积以及中、微孔数量均有所提高,孔径分布也得到了明显改善。活性数据显示,适量的稀土金属氧化物均能促进Ru-Ba/堇青石催化剂的活性,其中CeO2的改性效果最好,在10 MPa,475℃,5000 h-1时CeO2改性的Ru-Ba/堇青石催化剂的氨合成转化率达到9.9%。研究了CeO2对氨浓度随温度、压力、空速变化趋势的影响。
Conversion of ammonia synthesis over Ru- Ba/cordierite catalyst modified by different rare earth such as La203, CeO2, Pr2O3, Nd2O3 and Sm2O3 was studied. The modified catalysts were characterized by BET and BJH surface area measurements, SEM surface morphology analysis. The SEM results show that La2O3 congregated on the cordierite surface as ＂worm eggs＂, but CeO2 uniformly covered with the cordierite as cubic CaF2 crystal structure, and ruthenium uniformly distributes on the CeO2 modified cordierite supports as ＂single island＂. The value of BET surface area, pore volume, mesoporous and micro-porous are all higher than the original cordierite for the catalyst after modified by CeO2 and well controlled pore size distributions are also produced. Dynamics testing show that rare earth element can greatly improve the activity and stability of the catalyst, and the catalyst modified by CeO2 exhibits better performance for Ru-Ba/cordierite, which activity reaches 9.9% at 475 ℃, 5000 h^-1, Moreover, the relation between temperature, total pressure, space velocity and the activity of ammonia synthesis are effected by CeO2.
出处
《中国稀土学报》
CAS
CSCD
北大核心
2006年第6期666-670,共5页
Journal of the Chinese Society of Rare Earths
基金
国家自然科学基金(20576021)资助项目
福建省重大专项项目(2005H201-2)
关键词
氨合成
整体式
催化剂
稀土
ammonia synthesis
monolith
catalyst
rare earths
作者简介
王建梅（1979-），女，山东蓬莱人，硕士研究生；研究方向：催化材料
通讯联系人（E-mail：twang@fzu．edu．cn）
