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The role of oxygen vacancies in the CO2 methanation employing Ni/ZrO2 doped with Ca
International Journal of Hydrogen Energy ( IF 8.1 ) Pub Date : 2020-01-16 , DOI: 10.1016/j.ijhydene.2019.12.140
Oliver E. Everett , Priscila C. Zonetti , Odivaldo C. Alves , Roberto R. de Avillez , Lucia G. Appel

The Ni/ZrO2 catalyst doped with Ca and Ni/ZrO2 were employed in the CO2 methanation, a reaction which will possibly be used for storing intermittent energy in the future. The catalysts were characterized by X-ray photoelectron spectroscopy (XPS, reduction in situ), X-ray diffraction (XRD, reduction in situ and Rietveld refinement), electron paramagnetic resonance (EPR), temperature-programmed surface reaction, cyclohexane dehydrogenation model reaction, temperature-programmed desorption of CO2 and chemical analysis. The catalytic behavior of these catalysts in the CO2 methanation was analyzed employing a conventional catalytic test. Adding Ca to Ni/ZrO2, the metallic surface area did not change whereas the CO2 consumption rate almost tripled. The XRD, XPS and EPR analyses showed that Ca+2 but also some Ni2+ are on the ZrO2 surface lattice of the Ni/CaZrO2 catalyst. These cations form pairs which are composed of oxygen vacancies and coordinatively unsaturated sites (cus). By increasing the number of these pairs, the CO2 methanation rate increases. Moreover, the number of active sites of the CO2 methanation rate limiting step (CO and/or formate species decomposition, rls) is enhanced as well, showing that the rls occurs on the vacancies-cus sites pairs.



中文翻译:

氧空位在掺杂Ca / Ni / ZrO 2的CO 2甲烷化中的作用

掺有Ca和Ni / ZrO 2的Ni / ZrO 2催化剂用于CO 2甲烷化,该反应将来可能会用于存储间歇性能量。通过X射线光电子能谱(XPS,原位还原),X射线衍射(XRD,原位还原和Rietveld精制),电子顺磁共振(EPR),程序升温表面反应,环己烷脱氢模型反应对催化剂进行了表征。,程序升温的CO 2解吸和化学分析。使用常规催化试验分析了这些催化剂在CO 2甲烷化中的催化行为。向Ni / ZrO中添加Ca如图2所示,金属表面积没有变化,而CO 2消耗率几乎增加了两倍。XRD,XPS和EPR分析表明,Ni / CaZrO 2催化剂的ZrO 2表面晶格上有Ca +2以及一些Ni 2+。这些阳离子形成由氧空位和配位不饱和位点(cus)组成的对。通过增加这些对的数目,CO 2甲烷化率增加。此外,CO 2甲烷化率限制步骤的活性位点数目(CO和/或甲酸盐种类分解,rls)也增加了,表明rls出现在空位-cus位点对上。

更新日期:2020-01-17
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