Deposition of La₂O₃ and Al₂O₃ on Al₂O₃-supported Ni catalysts was performed to study their effects on heterogeneous catalysts for the dry reforming of methane (DRM) reaction. An alumina-supported Ni catalyst (Ni/Al₂O₃, 2 wt % of Ni), synthesized via incipient wetness impregnation, loses ∼87% of its initial activity within 45 h under DRM conditions. While overcoating of Al₂O₃ on this catalyst via atomic layer deposition (ALD) helps stabilize the catalytic activity in long time-on-stream (TOS) tests, this overcoated catalyst is ca. 40 times less active than the uncoated catalyst at peak activity. This Al₂O₃-overcoated Ni/Al₂O₃ catalyst also exhibits a long induction period (∼20 h) due to the slow reduction of Ni²⁺ within the catalytically inactive nickel aluminate (NiAl₂O₄) phase, formed by the interaction of metallic Ni with the Al₂O₃ overcoat during pre-DRM treatment at the 700 °C reaction temperature. Here, we report that, while doping small amounts of La (∼0.03 wt %) into the Ni/Al₂O₃ catalyst does not significantly affect the catalytic activity or stability by itself, the addition of ALD-Al₂O₃ on top of the La₂O₃-promoted Ni catalysts significantly suppresses the long TOS deactivation, helps recover the peak activity of uncoated Ni/Al₂O₃, and eliminates the DRM induction period. This strategy obtains the stabilization benefits of Al₂O₃ overcoating on Ni/Al₂O₃ while, at the same time, avoiding the formation of undesirable NiAl₂O₄ species.

中文翻译：

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使用原子层沉积结合 La 掺杂和 Al 外涂层稳定用于甲烷干重整的负载型 Ni 催化剂

在Al ₂ O ₃负载的Ni催化剂上沉积La ₂ O ₃和Al ₂ O ₃以研究它们对用于甲烷干重整(DRM)反应的多相催化剂的影响。通过初湿浸渍合成的氧化铝负载的镍催化剂（Ni/Al ₂ O ₃ , 2 wt% of Ni）在 DRM 条件下在 45 小时内失去了 87% 的初始活性。Al ₂ O _3复涂时在这种催化剂上通过原子层沉积 (ALD) 有助于稳定长时间运行 (TOS) 测试中的催化活性，这种涂层催化剂约为 在峰值活性时，活性比未涂层催化剂低 40 倍。由于在催化惰性铝酸镍 (NiAl ₂ O _{4 ) 相中 Ni} ²⁺的缓慢还原，这种 Al ₂ O ₃涂层的 Ni/Al ₂ O ₃催化剂还表现出较长的诱导期（~20 小时），由金属Ni与Al ₂ O _{3的相互作用}在 700 °C 反应温度下进行预 DRM 处理期间的外涂层。_{在这里，我们报告说，虽然在 Ni/Al 2} O ₃催化剂中掺杂少量的 La（~0.03 wt%）并不会显着影响催化剂本身的催化活性或稳定性，但在顶部添加 ALD-Al ₂ O ₃ La ₂ O ₃促进的Ni催化剂的显着抑制了长时间的TOS失活，有助于恢复未涂覆的Ni/Al ₂ O ₃的峰值活性，并消除了DRM诱导期。该策略获得了在 Ni/Al ₂ O _{3上覆盖 Al 2} O _{3的稳定性优势}同时，避免了不希望的NiAl ₂ O ₄物种的形成。