Reductive amination of carbonyl compounds with ammonia using H₂ as a reductant is a highly powerful method for synthesizing primary amines. To enhance sustainability, however, there is a need to develop heterogeneous catalysts based on iron, which is abundant and inexpensive. Previously reported Fe-based heterogeneous catalysts require a high reaction temperature and high H₂ pressure, probably due to the agglomeration of Fe particles during the reduction of iron oxide precursors. We discovered that layered double hydroxides (LDHs) were suitable precursors for preparing supported Fe catalysts. Reduction of Mg- and Fe-based LDHs (MgFe-LDHs) after introducing citrate furnished MgO-supported Fe catalysts (Fe–C/MgO) with small Fe and MgO particles. Fe–C/MgO worked as a reusable and stable heterogeneous catalyst for reductive amination at a low temperature and low H₂ pressure; the benzylamine yield from benzaldehyde reached 99% even at 80 °C under 1.5 MPa H₂ pressure. Introducing citrate to the LDHs not only suppressed the crystal growth of Fe and MgO particles but also facilitated the reduction of iron oxides to metallic Fe. This work demonstrates a promising method for the preparation of supported Fe catalysts with small Fe particles.

中文翻译：

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层状双氢氧化物制备负载型铁催化剂用于羰基化合物还原胺化合成伯胺


使用H ₂作为还原剂，羰基化合物与氨的还原胺化是合成伯胺的一种非常有效的方法。然而，为了提高可持续性，需要开发基于铁的多相催化剂，铁资源丰富且廉价。先前报道的铁基多相催化剂需要高反应温度和高H ₂压力，这可能是由于氧化铁前体还原过程中Fe颗粒的团聚。我们发现层状双氢氧化物（LDH）是制备负载型铁催化剂的合适前体。引入柠檬酸盐后还原镁基和铁基 LDH（MgFe-LDH），得到具有小 Fe 和 MgO 颗粒的 MgO 负载 Fe 催化剂（Fe-C/MgO）。 Fe-C/MgO是一种可重复使用、稳定的低温、低H ₂压还原胺化多相催化剂；即使在80℃、1.5 MPa H ₂压力下，苯甲醛的苯甲胺收率也达到99%。将柠檬酸盐引入LDH不仅抑制了Fe和MgO颗粒的晶体生长，而且促进了铁氧化物还原为金属Fe。这项工作展示了一种制备具有小铁颗粒的负载型铁催化剂的有前途的方法。