Abstract This study reports a one-step facile synthesis of a novel heterogeneous granule base catalyst, dubbed CaO/AC that contains small calcium oxide (CaO) nanoparticles embedded within hierarchical activated carbon (AC). The CaO/AC hybrid exhibited a 98.59 wt% fatty acid methyl esters yield, with 89.75% less catalyst compared to pristine CaO. In addition, the CaO/AC granular catalyst, which was easily recovered without any post-treatment, presented sustainable catalytic activity after two cycles of transesterification. The calcium cations penetrated into the cell wall of coconut shell by vacuum impregnation, and the carbonization of cell wall suppressed the agglomeration of calcium compound, which was essential for the catalytic self-activation of Ca-doped coconut shell. The pyrolysis atmosphere and dwelling time were investigated to demonstrate the dual function of calcium. Owing to the catalytic effect of Ca during the self-activation process, the hierarchical activated carbon with improved mesopores was manufactured. On the other hand, CaO nanoparticles with an average size of 14.7 nm were in-situ encapsulated within the mesopores of hierarchical carbon matrices. The additional formation of mesopores and high dispersion of CaO nanoparticles were responsible for the enhanced inner mass transfer and the number of accessible alkaline sites in transesterification of triglycerides, leading to the high catalytic activity and stability of CaO/AC.

中文翻译：

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Ca掺杂椰壳的催化自活化原位合成分级多孔碳负载CaO酯交换催化剂

摘要 本研究报告了一种新型多相颗粒碱催化剂的一步简便合成，称为 CaO/AC，其中包含嵌入分级活性炭 (AC) 的小氧化钙 (CaO) 纳米颗粒。CaO/AC 杂化物的脂肪酸甲酯产率为 98.59%（重量），与原始 CaO 相比催化剂减少了 89.75%。此外，无需任何后处理即可轻松回收的 CaO/AC 颗粒催化剂在经过两个酯交换循环后表现出可持续的催化活性。钙离子通过真空浸渍渗透到椰壳细胞壁中，细胞壁的碳化抑制了钙化合物的团聚，这对于掺钙椰壳的催化自活化至关重要。研究了热解气氛和停留时间以证明钙的双重功能。由于Ca在自活化过程中的催化作用，制备了具有改进介孔的分级活性炭。另一方面，平均尺寸为 14.7 nm 的 CaO 纳米颗粒被原位封装在分级碳基质的介孔内。中孔的额外形成和 CaO 纳米颗粒的高分散性是导致内部传质增强和甘油三酯酯交换中可接近的碱性位点数量的原因，导致 CaO/AC 的高催化活性和稳定性。制备出具有改进介孔的分级活性炭。另一方面，平均尺寸为 14.7 nm 的 CaO 纳米颗粒被原位封装在分级碳基质的介孔内。中孔的额外形成和 CaO 纳米颗粒的高分散性是导致内部传质增强和甘油三酯酯交换中可接近的碱性位点数量的原因，导致 CaO/AC 的高催化活性和稳定性。制备出具有改进介孔的分级活性炭。另一方面，平均尺寸为 14.7 nm 的 CaO 纳米颗粒被原位封装在分级碳基质的介孔内。中孔的额外形成和 CaO 纳米颗粒的高分散性是导致内部传质增强和甘油三酯酯交换中可接近的碱性位点数量的原因，导致 CaO/AC 的高催化活性和稳定性。