CeO2的形貌特征对Ni/CeO2催化剂CO甲烷化性能的影响

Morphologic effect of CeO2 on the catalytic performance of Ni/CeO2 in CO methanation

通过改变制备方法合成了不同形貌的CeO2载体(包括球状CeO2-S、花苞状CeO2-F和多面体状CeO2-P),并用氨水配位浸渍法制备了Ni/CeO2催化剂。研究了CeO2载体结构与Ni/CeO2催化剂上CO甲烷化反应性能的关系。结果表明,CeO2-S、CeO2-F和CeO2-P载体暴露的晶面和氧空位不同,对Ni/CeO2催化剂催化活性影响也不相同。CeO2-S氧空位最多,Ni/CeO2-S在350℃下CO转化率和CH4选择性分别达到99.19%和88.88%。10 h热稳定性测试结果表明,Ni/CeO2-S催化剂上的积炭量最少(2.5%),CH4选择性一直保持在80%左右,分别是Ni/CeO2-F的1.3倍和Ni/CeO2-P的17.6倍。这主要归因于CeO2-S载体比表面积较大,主要暴露[111]晶面,且表面氧空位含量较多,使Ni/CeO2-S催化剂的载体与活性中心的相互作用增强,从而呈现出优异的抗积炭性能。

CeO2 supports with different morphologies(including spherical CeO2-S, bud-shaped CeO2-F, and polyhedral CeO2-P) were synthesized and the supported Ni/CeO2 catalysts were prepared by ammonia-water coordination impregnation method;the effect of CeO2 morphology on the catalytic performance of Ni/CeO2 in CO methanation was then investigated. The results indicate that CeO2-S, CeO2-F, and CeO2-P supports are rather different in the exposed crystal planes and oxygen vacancies, which have a significant effect on the catalytic performance of Ni/CeO2 in CO methanation. In particular, CeO2-S has the most oxygen vacancies;for CO methanation over the Ni/CeO2-S catalyst, the conversion of CO and selectivity to CH4 at 350 ℃ reach 99.19% and 88.88%, respectively. After 10 h thermal stability test, the Ni/CeO2-S catalyst displays lowest carbon deposit(2.5%);the selectivity to CH4 over the Ni/CeO2-S catalyst remains above 80%, which is 1.3 times of that over Ni/CeO2-F and 17.6 times of that over Ni/CeO2-P. The excellent catalytic performance of Ni/CeO2-S may be ascribed to that CeO2-S support has large surface area and mainly exposes the [111] crystal plane with a large amount of oxygen vacancies, which can enhance the interaction between the support and the active center and alleviate the carbon deposition.