Bulk Ni-based catalysts derived from hydrotalcite-type (HT) compounds show enhanced stability in the hydrogenation of CO₂ into CH₄, in comparison to their supported counterparts. The composition of the parent hydrotalcite determines the Ni loading and particle size, as well as the basicity of the catalysts. In this work, a comparison between the effect of Fe and La on the performance of NiMgAl HT compounds (Ni/Mg/Al = 25/50/25 atomic ratio) calcined at 600 °C is investigated. After a reduction pretreatment at 750 °C, both promoters enhance the activity in the low-temperature range; however, the La-containing catalyst reaches a better CH₄ productivity rate at high oven temperature (i.e., 200 L g_Ni^–1 h^–1 at 325 °C). Although the formation of the NiFe alloy improves the activity, lanthanum keeps smaller Ni⁰ particles and provides a higher basicity to the mixed oxide than Fe. The activity of the NiMgLaAl catalyst can be further tailored by increasing the Ni loading from 25.6 wt % (Ni25Mg50La5Al20) to 44.6 wt % (Ni50Mg25La5Al20). Lastly, the feasibility of HT-derived catalysts in the direct methanation of clean biogas is proved.

中文翻译：

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Fe 和 La 对 NiMgAl HT 衍生催化剂在 CO2 和沼气甲烷化中性能的影响

与负载型催化剂相比，源自水滑石型 (HT) 化合物的块体 Ni 基催化剂在 CO ₂加氢生成 CH ₄时表现出更高的稳定性。母体水滑石的组成决定了镍的负载量和粒径，以及催化剂的碱度。在这项工作中，比较了 Fe 和 La 对在 600 °C 下煅烧的 NiMgAl HT 化合物（Ni/Mg/Al = 25/50/25 原子比）性能的影响。在 750 °C 还原预处理后，两种促进剂均增强了低温范围内的活性；然而，含 La 催化剂在高烘箱温度（即 200 L _{g Ni} ^–1 h ^–1在 325 °C）。虽然NiFe合金的形成提高了活性，但镧保持更小的Ni ⁰颗粒并且比Fe为混合氧化物提供更高的碱度。通过将 Ni 负载量从 25.6 wt% (Ni25Mg50La5Al20) 增加到 44.6 wt% (Ni50Mg25La5Al20)，可以进一步调整 NiMgLaAl 催化剂的活性。最后证明了HT衍生催化剂在清洁沼气直接甲烷化中的可行性。