Indexed by:期刊论文

Date of Publication:2017-07-01

Journal:ACS CATALYSIS

Included Journals:SCIE

Volume:7

Issue:7

Page Number:4571-4580

ISSN No.:2155-5435

Key Words:lignin; transfer hydrogenation; heterogeneous catalysis; visible light; ZnIn2S4

Abstract:Obtaining high selectivity of aromatic monomers from renewable lignin has been extensively pursued but is still unsuccessful, hampered by the need to efficiently cleave C-O/C-C bonds and inhibit lignin proliferation reactions. Herein, we report a transfer hydrogenolysis protocol using a heterogeneous ZnIn2S4 catalyst driven by visible light. In this process, alcoholic groups (C alpha H-OH) of lignin act as hydrogen donors. Proliferation of phenolic products to dark substances is suppressed under visible light illumination at low temperature (below 50 degrees C); formation of a light and transparent reaction solution allows visible light to be absorbed by the catalyst. With this strategy, 71-91% yields of phenols in the conversion of lignin beta-O-4 models and a 10% yield of p-hydroxyl acetophenone derivatives from organosolv lignin are achieved. Mechanistic studies reveal that C alpha H-OH groups of lignin beta-O-4 linkage are initially dehydrogenated on ZnIn2S4 to form a "hydrogen pool", and the adjacent C-beta-O bond is subsequently hydrogenolytically cleaved to two monomers by the "hydrogen pool". Thus, the dehydrogenation and hydrogenolysis reaction are integrated in one-pot with lignin itself as a hydrogen donor. This study shows a promising way of supplying phenolic compounds by taking advantages of both renewable biomass feedstocks and photoenergy.