Ceria–zirconia-supported Ni catalysts (Ni/Ce_0.83Zr_0.17O₂ or Ni/CZ) are prepared by dry impregnation, strong electrostatic adsorption, coprecipitation (CP), and combustion synthesis (CS). The nature and abundance of Ni species in these samples are characterized by X-ray adsorption spectroscopy, temperature-programmed reduction, and CO chemisorption. The bulk synthesis methods (i.e., CP and CS) produce Ni cations that are incorporated into the CZ lattice forming mixed-metal oxides with Ni³⁺ species at low Ni content. The formation of mixed-metal oxides increases the reducibility of CZ and increases the abundance of active surface oxygen. All NiO/CZ catalysts are active for methane dry reforming and retain some of their activity at a steady state. The initial methane conversion correlates linearly with the fraction of accessible Ni after reduction. The predominant path of catalyst deactivation strongly depends on the structure of the catalyst and, thus, on the synthesis method used. All catalysts experience agglomeration of Ni particles under reaction conditions. Improving the Ni dispersion to isolated species embedded in a support does not improve resistance to Ni particle growth. Coke formation is inversely related to the concentration of active surface oxygen. The dominant deactivation mechanism for catalysts made by CS is the encapsulation of Ni particles by the support.

中文翻译：

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不同合成方法制备的Ni / Ce _x Zr _{1– x} O _2的镍形态和甲烷干重整性能

二氧化铈-氧化锆负载的Ni催化剂（Ni / Ce _0.83 Zr _0.17 O ₂或Ni / CZ）是通过干浸渍，强静电吸附，共沉淀（CP）和燃烧合成（CS）制备的。这些样品中Ni的性质和丰度通过X射线吸收光谱，程序升温还原和CO化学吸附进行表征。本体合成方法（即CP和CS）产生的Ni阳离子被掺入CZ晶格中，形成具有Ni ^3+的混合金属氧化物镍含量低的物种。混合金属氧化物的形成增加了CZ的还原性，并增加了活性表面氧的丰度。所有NiO / CZ催化剂对甲烷干重整均具有活性，并在稳态下保持其某些活性。甲烷的初始转化率与还原后可及的Ni含量呈线性关系。催化剂失活的主要途径很大程度上取决于催化剂的结构，因此取决于所用的合成方法。所有催化剂在反应条件下都会发生镍颗粒的团聚。将镍分散体改进为嵌入载体中的分离物不会改善对镍粒子生长的抵抗力。焦炭的形成与活性表面氧的浓度成反比。