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首页> 外文期刊>Catalysis science & technology >The tendency of supports to generate oxygen vacancies and the catalytic performance of Ni/ZrO2 and Ni/Mg(Al)O in CO2 methanation
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The tendency of supports to generate oxygen vacancies and the catalytic performance of Ni/ZrO2 and Ni/Mg(Al)O in CO2 methanation

机译：支持产生氧空位的支撑趋势以及二氧化碳中Ni/Zro2和Ni/mg（Al）O的催化性能

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Ni/ZrO2, Ni/Mg(Al)O, and Ni/SiO2 catalysts were employed in CO2 methanation. The catalysts were characterized by XPS, XRF, XRD (Rietveld refinement method), TPR, EPR, BET, CO2 + H2-TPSR, CO + H2-TPSR, CO2-TPD, CO-TPD, S/TEM-XEDS, and DFT calculations. The catalytic performance of these catalysts in CO2 methanation was analyzed employing a conventional microreactor. CO2 consumption and formation rates of the products were obtained under differential conditions. The Ni/ZrO2 catalyst exhibited the highest activity and selectivity for the methanation of CO2 compared to Ni/Mg(Al)O and Ni/SiO2. The Mg-based catalyst reaches the Ni/ZrO2 performance at high temperatures. Some authors have proposed that CO rupture or formate decomposition (the rate-limiting step of CO2 methanation) occurs on pairs of oxygen vacancy–cus sites. DFT calculations showed that oxygen vacancies improve CO adsorption and dissociation over the Ni/ZrO2 catalyst. For Ni/ZrO2, the vacancies are generated by the insertion of Ni in the ZrO2 lattice (DRX) and by the defects of ZrO2 oxide (EPR), whereas Mg(Al)O shows intrinsic vacancies (EPR). Ni/ZrO2 exhibits the same metallic area compared with Ni/Mg(Al)O. However, the former is more active and selective than Ni/Mg(Al)O at a large temperature range, showing that H2 dissociation is not the rate-limiting step. Indeed, the Zr-based catalyst generates H2O or eliminates oxygen, generating vacancies at much lower temperatures than Ni/Mg(Al)O (CO2 + H2-TPSR and CO + H2-TPSR). However, at higher temperatures (>400 °C), the catalytic behavior of these two catalysts is similar. Indeed, the elimination of H2O and oxygen vacancy formation are easier for both catalysts under these conditions. Thus, this work shows that the catalytic performance of Ni-based catalysts is associated with the support's facility to release O (reducibility).
机译：Ni/Zro2，Ni/Mg（Al）O和Ni/SiO2催化剂用于CO2甲烷化。这些催化剂的特征是XPS，XRF，XRD（Rietveld Refinement方法），TPR，EPR，BET，CO2 + H2-TPSR，CO + H2-TPSR，CO2-TPD，CO2-TPD，CO-TPD，S/s/tem-Xeds和DFT计算。使用常规微反应器分析了这些催化剂在CO2甲基化中的催化性能。产品的二氧化碳消耗和形成速率是在不同条件下获得的。与Ni/Mg（Al）O和Ni/SiO2相比，Ni/Zro2催化剂对CO2的甲烷化的活性和选择性最高。基于MG的催化剂在高温下达到NI/ZRO2性能。一些作者提出，CO破裂或甲酸分解（二氧化碳甲基化的速率限制步骤）发生在氧气空位 - CUS位点上。 DFT计算表明，氧空位改善了Ni/Zro2催化剂上的CO吸附和解离。对于Ni/Zro2，空缺是由Ni在ZRO2晶格（DRX）中的插入和ZRO2氧化物（EPR）的缺陷产生的，而Mg（al）O显示出内在空缺（EPR）。 Ni/Zro2与Ni/mg（Al）O相比表现出相同的金属区域。但是，前者比在较大温度范围内的Ni/mg（Al）O更有活力和选择性，这表明H2解离并不是限速步骤。实际上，基于ZR的催化剂会产生H2O或消除氧气，在温度低得多的空位比Ni/mg（Al）O（CO2 + H2-TPSR和CO + H2-TPSR）的温度低得多。但是，在较高的温度（> 400°C）下，这两种催化剂的催化行为相似。实际上，在这些条件下，两种催化剂都更容易消除H2O和氧空位的形成。因此，这项工作表明，基于NI的催化剂的催化性能与支持的设施释放O（可降低）有关。

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