β-O-4 Bond Cleavage Mechanism for Lignin Model Compounds over Pd Catalysts Identified by Combination of First-Principles Calculations and Experiments

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• 作者：Jianmin Lu ; Min Wang ; Xiaochen Zhang ; Andreas Heyden ; Feng Wang
• 刊名：ACS Catalysis
• 出版年：2016
• 出版时间：August 5, 2016
• 年：2016
• 卷：6
• 期：8
• 页码：5589-5598
• 全文大小：839K
• 年卷期：0
• ISSN：2155-5435

文摘

Lignin in lignocellulosic biomass is the only renewable source for aromatic compounds, and effective valorization of lignin remains a significant challenge in biomass conversion processes. We have performed density functional theory calculations and experiments to investigate the cleavage mechanism of the C–O ether bond in the lignin model compound 2-phenoxy-1-phenylethanol with a β-O-4 linkage over a Pd(111) catalyst surface model. We propose the favorable reaction pathway to proceed as follows: the dilignol reactant gets dehydrogenated first on the α-carbon and then on the −OH group to generate its corresponding ketone 2-phenoxy-1-phenylethanone; the ketone continues to get dehydrogenated on the β-carbon by first a equilibrated keto–enol tautomerization to its enol form and then −OH dehydrogenation; the C–O ether bond cleavage happens afterward, leading to one-aromatic-ring surface intermediates followed by hydrogenation to yield acetophenone and phenol.