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Low-temperature conversion of base precursor KNO3 on core–shell structured Fe3O4@C: Fabrication of magnetically responsive solid strong bases
Catalysis Today ( IF 5.3 ) Pub Date : 2020-10-12 , DOI: 10.1016/j.cattod.2020.10.007
Tian-Tian Li , Ming-Qi Shao , Chen Gu , Song-Song Peng , Xiao-Qin Liu , Lin-Bing Sun

Solid strong bases can catalyze a variety of organic reactions under mild conditions. Their preparation consists of loading base precursors (e.g. KNO3) on porous supports followed by activating to convert base precursors to basic sites (e.g. K2O). However, high temperatures are usually required for activation, which consumes lots of energy and damages the structure of supports. Moreover, filtration or centrifugation is mainly adopted for the recovery of solid base catalysts, which is tedious and limits their applications to some extent. In this paper, we constructed multifunctional core–shell structured Fe3O4@C microspheres as the supports owing to the reducibility of carbon shell and the magnetism of Fe3O4 core, thus creating magnetically responsive solid strong bases under mild conditions. Strong basic sites can be formed at a low temperature of 400 °C due to the redox reaction between the carbon shell and the base precursor, yielding the solid base K-400@Fe3O4@C. Such a temperature is obviously lower than the temperature for the decomposition of KNO3 on the frequently used supports SiO2 (750 °C) and Al2O3 (500−700 °C). The resultant solid base K-400@Fe3O4@C exhibits excellent catalytic activity in transesterification reaction, and the yield of target product dimethyl carbonate is higher than some benchmarks like MgO, CsX, and Na2O/Al2O3. In addition, thanks to the superparamagnetism, the solid base catalysts can be recovered within 10 s with the assistance of external magnetic fields.



中文翻译:

核壳结构 Fe 3 O 4 @C上碱前体 KNO 3的低温转化:磁响应固体强碱的制备

固体强碱在温和条件下可催化多种有机反应。它们的制备包括将碱前体(例如 KNO 3)加载到多孔载体上,然后激活以将碱前体转化为碱性位点(例如 K 2 O)。然而,活化通常需要高温,这会消耗大量能量并破坏支撑结构。此外,固体碱催化剂的回收主要采用过滤或离心法,操作繁琐,在一定程度上限制了其应用。在本文中,由于碳壳的还原性和 Fe 3 O的磁性,我们构建了多功能核壳结构的 Fe 3 O 4 @C 微球作为载体。4核,从而在温和的条件下产生磁性响应的固体强碱。由于碳壳和碱前体之间的氧化还原反应,可以在 400 °C 的低温下形成强碱位点,产生固体碱 K-400@Fe 3 O 4 @C。这样的温度明显低于KNO 3在常用载体SiO 2 (750 °C)和Al 2 O 3 (500-700 °C)上分解的温度。所得固体碱K-400@Fe 3 O 4@C在酯交换反应中表现出优异的催化活性,目标产物碳酸二甲酯的产率高于MgO、CsX和Na 2 O/Al 2 O 3等一些基准。此外,由于超顺磁性,固体碱催化剂可以在外部磁场的帮助下在 10 秒内恢复。

更新日期:2020-10-12
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