The deactivation of supported nickel catalysts by coking is an important technological subject for many chemical processes, especially when high concentrations of unsaturated hydrocarbons are present in the feed gas. Here, the reversible segregation of Ni from a LaFeO_3±δ perovskite‐type host lattice was exploited to completely recover a LaFe_0.8Ni_0.2O_3±δ catalyst after it had been deliberately subjected to severe carbon deposition during CO₂ methanation in ethylene rich feed gas for several hours. Temperature programmed reduction, X‐ray diffraction, electron microscopy, X‐ray absorption spectroscopy and catalytic activity tests were used to follow the catalyst structure along the various steps of reduction, reaction, coking and subsequent regeneration, while Raman spectroscopy and electron microscopy were used to characterize the nature of the carbon deposits. It is shown that upon reduction Ni atoms segregate to the surface of the perovskite to form catalytic active Ni particles. Oxidation stimulates Ni atoms to readopt the coordination environment of Fe in the perovskite matrix. This property persisted after severe catalyst deactivation by filamentous, partially graphitic carbon. It is demonstrated that simple catalyst reoxidation can be applied to oxidize all carbon deposits while additionally reverting segregated Ni back into the host lattice, thus protecting Ni from particle growth and resultant long‐term loss of catalyst activity over multiple regeneration cycles.

中文翻译：

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去除焦炭过程中LaFe0.8Ni0.2O3±δ中Ni的可逆偏析

对于许多化学方法，特别是当进料气中存在高浓度的不饱和烃时，通过焦化使负载的镍催化剂失活是重要的技术课题。在这里，在将LaFeO _{3± δ}钙钛矿型主晶格中的Ni进行可逆的偏析后，可充分回收LaFe _0.8 Ni _0.2 O _{3± δ}催化剂，该催化剂在CO ₂期间经过认真的碳沉积后得以完全回收。在富含乙烯的原料气中甲烷化数小时。使用程序升温还原，X射线衍射，电子显微镜，X射线吸收光谱和催化活性测试沿着还原，反应，焦化和后续再生的各个步骤跟踪催化剂的结构，同时使用拉曼光谱和电子显微镜表征碳沉积物的性质。结果表明，还原后，Ni原子偏析到钙钛矿的表面，形成催化活性的Ni颗粒。氧化刺激镍原子重新采用钙钛矿基质中铁的配位环境。在通过丝状的部分石墨碳使催化剂严重失活后，该性能仍然存在。