Nitrogen-Doped Carbon-Modified Cobalt-Nanoparticle-Catalyzed Oxidative Cleavage of Lignin β-O-4 Model Compounds under Mild Conditions
Nitrogen-Doped Carbon-Modified Cobalt-Nanoparticle-Catalyzed Oxidative Cleavage of Lignin β-O-4 Model Compounds under Mild Conditions
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温和条件下氮掺杂碳改性钴纳米颗粒催化木质素 β-O-4 模型化合物的氧化裂解
DOI：
10.1021/acssuschemeng.8b02802
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发表时间：
2018-11-05
影响因子：
8.4
通讯作者：
Gao, Shuang
中科院分区：
文献类型：
--
作者：
Luo, Huihui;Wang, Lianyue;Gao, Shuang
首次研制了一种天然维生素B-12在活性碳上裂解制得的无贵金属钴基催化剂，用于在温和的反应条件下，以分子氧为氧化剂，一锅氧化裂解木质素与苯酚和芳香酯的键。在现有钴催化剂的基础上，苯酚的产率较高，苯酚没有发生氧化偶联反应。与以前的报道相比，本催化剂即使在室温下使用氧气气球也可以实现β-O-4酮的氧化裂解。多相催化剂表现出很强的可回收性，可以方便地回收和重复使用长达8次，而不会明显降低催化活性。此外，该催化体系还可以实现有机溶质木质素的键断裂。用二维异核单量子相干核磁共振和凝胶渗透色谱证明了解聚的存在。通过电感耦合等离子体、N-2吸附-脱附、拉曼光谱、扫描电子显微镜、透射电子显微镜、高分辨电子显微镜、大角度暗场扫描电子显微镜、能量色散X射线能谱、X射线光电子能谱和对照实验对催化剂进行了表征，为了解催化剂材料和反应途径提供了基础。用高温热解的方法将Co3O4原位负载在含氮碳载体上，可能是一种催化活性物种。用气相色谱-质谱法对两个反应中间体进行了检测和确认。
A noble-metal-free Co-based catalyst, derived from pyrolysis of natural vitamin B-12 on activated carbon, is developed for the first time for one-pot oxidative cleavage of lignin linkages to phenols and aromatic esters with molecular oxygen as the oxidant under mild reaction conditions. High yields of phenol were obtained, and no oxidative coupling of phenol was produced based on the present cobalt catalyst. Compared to the previous report, the present catalyst can achieve the oxidative cleavage of beta-O-4 ketones even at room temperature using a dioxygen balloon. The heterogeneous catalyst shows robust recyclability and can be conveniently recovered and reused up to eight times without an appreciable loss of catalytic activity. Moreover, this catalyst system can realize the bond cleavage of organosolv lignin. The evidence of depolymerization was given by two-dimensional heteronuclear single quantum coherence NMR and gel permeation chromatography. Characterization of the catalyst by inductively coupled plasma, N-2 adsorption-desorption, Raman spectroscopy, scanning electron microscopy, transmission electron microscopy (TEM), high-resolution TEM, high-angle angular dark-field scanning TEM, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and control experiments provide a fundamental understanding of the catalytic materials and the reaction pathway. Co3O4 in situ supported on a N-doped carbon matrix by the way of high-temperature pyrolysis might be a catalytically active species. Two reaction intermediates are detected and confirmed by gas chromatograph-mass spectrometry.