A novel egg-like nanosphere was designed as a long-lived catalyst and is described as Fe₃O₄@nSiO₂-NH₂-Fe₂O₃•xBi₂O₃@mSiO₂. The catalyst was prepared using a modified Stöber method with template-free surface-protected etching. The catalyst particle consists of a magnetic Fe₃O₄ core as the “yolk”, an inner silica shell bearing active Fe₂O₃•xBi₂O₃ species as the “egg white”, and outer mesoporous silica as the “egg shell”. It exhibits an excellent performance in the catalytic reduction of nitro aromatics to corresponding anilines in a fixed-bed continuous-flow reactor. The reaction could be performed at 80 °C and could reach complete conversion in less than 1 min with only a 7% excess of hydrazine hydrate. The catalyst bed could be easily shifted between different substrates without cross-contamination because of the uniformity of the catalyst particles. This catalyst exhibited very good stability in the continuous-flow protocol. In the long-term reduction of p-nitrophenol with 0.5 mmol·min⁻¹ productivity, it worked for more than 1,500 cycles without any catalytic activity loss.

中文翻译：

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蛋状磁固定纳米球：连续流反应器中氢转移反应的长寿命催化剂模型

设计了一种新型的鸡蛋状纳米球作为长寿命催化剂，并描述为Fe ₃ O ₄ @ n SiO ₂ -NH ₂ -Fe ₂ O ₃ • x Bi ₂ O ₃ @ m SiO ₂。使用改进的Stöber方法和无模板的表面保护蚀刻法制备催化剂。催化剂颗粒由磁性Fe ₃ O ₄核（称为“卵黄”），内部带有活性Fe ₂ O ₃ • x Bi ₂ O _3的二氧化硅壳组成。种类称为“卵白”，而外部介孔二氧化硅称为“卵壳”。在固定床连续流反应器中，它在将硝基芳烃催化还原为相应的苯胺方面表现出出色的性能。该反应可以在80℃下进行，并且仅用7％的水合肼即可在不到1分钟的时间内达到完全转化。由于催化剂颗粒的均匀性，催化剂床可以容易地在不同的基材之间移动而没有交叉污染。该催化剂在连续流方案中表现出非常好的稳定性。在以0.5mmol·min ^-1的产率长期还原对硝基苯酚时，其进行了超过1,500次循环而没有任何催化活性的损失。