Chinese Journal of Catalysis ›› 2017, Vol. 38 ›› Issue (7): 1216-1228.DOI: 10.1016/S1872-2067(17)62854-7

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Decomposition of a β-O-4 lignin model compound over solid Cs-substituted polyoxometalates in anhydrous ethanol:acidity or redox property dependence?

Xuezhong Wua,b, Wenqian Jiaoa, Bing-Zheng Lib, Yanming Lib, Yahong Zhanga, Quanrui Wangc, Yi Tanga   

  1. a Department of Chemistry, Laboratory of Advanced Materials, Collaborative Innovation Center of Chemistry for Energy Materials and Shanghai Key Laboratory of Molecular Catalysis and Innovative Materials, Fudan University, Shanghai 200433, China;
    b State Key Laboratory of Non-Food Biomass Enzyme Technology, National Engineering Research Center for Non-Food Biorefinery, Guangxi Key Laboratory of Biorefinery, Guangxi Academy of Sciences, Nanning 530007, Guangxi, China;
    c Department of Chemistry, Fudan University, Shanghai 200433, China
  • Online:2017-07-18 Published:2017-06-27
  • Contact: 10.1016/S1872-2067(17)62854-7
  • Supported by:

    This work was supported by the National Key Basic Research Program of China (973 program, 2013CB934101), National Natural Science Foundation of China (21433002, 21573046), China Postdoctoral Science Foundation (2016M601492), and International Science and Technology Cooperation Projects of Guangxi (15104001-5).

Abstract:

Production of aromatics from lignin has attracted much attention. Because of the coexistence of C-O and C-C bonds and their complex combinations in the lignin macromolecular network, a plausible roadmap for developing a lignin catalytic decomposition process could be developed by exploring the transformation mechanisms of various model compounds. Herein, decomposition of a lignin model compound, 2-phenoxyacetophenone (2-PAP), was investigated over several ce-sium-exchanged polyoxometalate (Cs-POM) catalysts. Decomposition of 2-PAP can follow two dif-ferent mechanisms:an active hydrogen transfer mechanism or an oxonium cation mechanism. The mechanism for most reactions depends on the competition between the acidity and redox proper-ties of the catalysts. The catalysts of POMs perform the following functions:promoting active hy-drogen liberated from ethanol and causing formation of and then temporarily stabilizing oxonium cations from 2-PAP. The use of Cs-PMo, which with strong redox ability, enhances hydrogen libera-tion and promotes liberated hydrogen transfer to the reaction intermediates. As a consequence, complete conversion of 2-PAP (>99%) with excellent selectivities to the desired products (98.6% for phenol and 91.1% for acetophenone) can be achieved.

Key words: Lignin model compound, β-O-4 ether bond, Polyoxometalate, Hydrogen transfer mechanism, Oxonium cation mechanism, Anhydrous ethanol