19514-00-2Relevant academic research and scientific papers
Catalytic C–O bond cleavage in a β-O-4 lignin model through intermolecular hydrogen transfer
Ahsan Usman, Muhammad,Naeem, Maham,Saeed, Muhammad,Zaheer, Muhammad
, (2021/03/22)
A base-free and redox neutral approach for the selective breaking of aryl ether bond (C–O) contained by a lignin model compound mimicking a β-O-4 linkage is reported. A palladium loaded metal-organic framework (MOF) was used as a catalyst for this purpose. The reaction proceeds through dehydrogenation of benzylic alcohol moiety followed by the hydrogenolysis of the ether bonds. Therefore, no external hydrogen source is required for the reaction to take place.
Visible-light-induced C-C bond cleavage of lignin model compounds with cyanobenziodoxolone
Zheng, Ming,Huang, Yan,Zhan, Le-Wu,Hou, Jing,Li, Bin-Dong
supporting information, (2020/10/02)
The catalytic degradation of lignin to value-added chemicals has received considerable attention over the past decade. Photocatalysis provides promising approaches to enable previously inaccessible transformations. However, examples of the visible-light promoted degradation of lignin are still limited. In this work, the visible-light-induced selective C-C bond cleavage of β-O-4 lignin model compounds has been disclosed via β-scission of in situ generated alkoxy radical intermediates. With cyanobenziodoxolone as the oxidant, a variety of substrates could be transformed into aldehydes in moderate to good yields. In addition, unexpected acetal esters which could conveniently furnish formaldehyde and phenols by alcoholysis were observed.
Activating molecular oxygen with Au/CeO2 for the conversion of lignin model compounds and organosolv lignin
Song, Wu-Lin,Dong, Qingmeng,Hong, Liang,Tian, Zhou-Qi,Tang, Li-Na,Hao, Wenli,Zhang, Hongxi
, p. 31070 - 31077 (2019/10/28)
Au/CeO2 was demonstrated to be a high efficiency catalyst for the conversion of 2-phenoxyacetophenol (PP-ol) employing O2 as an oxidant and methyl alcohol as the solvent without using an erosive strong base or acid. Mechanistic investigations, including emission quenching experiments, electron spin-resonance (ESR) and intermediate verification experiments, were carried out. The results verified that the superoxide anion activated by Au/CeO2 from molecular oxygen plays a vital role in the oxidation of lignin model compounds, and the cleavage of both the β-O-4 and Cα-Cβ linkages was involved. Au/CeO2 also performed well in the oxidative conversion of organosolv lignin under mild conditions (453 K), producing vanillin (10.5 wt%), methyl vanillate (6.8 wt%), methylene syringate (3.4 wt%) and a ring-opened product. Based on the detailed characterization data and mechanistic results, Au/CeO2 was confirmed to be a promising catalytic system.
Oxidative cleavage of β-O-4 bonds in lignin model compounds with a single-atom Co catalyst
Liu, Sijie,Bai, Lichen,Van Muyden, Antoine P.,Huang, Zhangjun,Cui, Xinjiang,Fei, Zhaofu,Li, Xuehui,Hu, Xile,Dyson, Paul J.
supporting information, p. 1974 - 1981 (2019/04/29)
Single-atom catalysts are emerging as primary catalysts for many reactions due to their 100% utilization of active metal centers leading to high catalytic efficiencies. Herein, we report the use of a single-atom Co catalyst for the oxidative cleavage of the β-O-4 bonds of lignin model compounds at a low oxygen pressure. Under the optimized reaction conditions, the conversion of 2-(2-methoxyphenoxy)-1-phenylethanol up to 95% with high selectivities was achieved with a variety of substrates investigated. The reusability of the Co catalyst with a high catalytic efficiency indicates its potential application in the oxidative cleavage of C-O bonds.
Acid promoted C-C bond oxidative cleavage of β-O-4 and β-1 lignin models to esters over a copper catalyst
Wang,Li,Lu,Li,Zhang,Liu,Luo,Wang
supporting information, p. 702 - 706 (2017/08/15)
Depolymerisation of lignin to aromatics is a challenging task. We herein report that a Cu(OAc)2/BF3·OEt2 catalyst is effective in simultaneously cleaving C-C bonds in β-1 and β-O-4 ketones, yielding esters and phenols. In-depth studies show that C-H bond activation is the rate determining step for C-C bond cleavage. BF3·OEt2 promotes the reaction via activating the β-C-H bond. This study offers the potential to obtain aromatic esters from lignin.
Promoting Lignin Depolymerization and Restraining the Condensation via an Oxidation-Hydrogenation Strategy
Zhang, Chaofeng,Li, Hongji,Lu, Jianmin,Zhang, Xiaochen,Macarthur, Katherine E.,Heggen, Marc,Wang, Feng
, p. 3419 - 3429 (2017/06/09)
For lignin valorization, simultaneously achieving the efficient cleavage of ether bonds and restraining the condensation of the formed fragments represents a challenge thus far. Herein, we report a two-step oxidation-hydrogenation strategy to achieve this goal. In the oxidation step, the O2/NaNO2/DDQ/NHPI system selectively oxidizes CαH-OH to Cα=O within the β-O-4 structure. In the subsequent hydrogenation step, the α-O-4 and the preoxidized β-O-4 structures are further hydrogenated over a NiMo sulfide catalyst, leading to the cleavage of Cβ-OPh and Cα-OPh bonds. Besides the transformation of lignin model compounds, the yield of phenolic monomers from birch wood is up to 32% by using this two-step strategy. The preoxidation of CαH-OH to Cα=O not only weakens the Cβ-OPh ether bond but also avoids the condensation reactions caused by the presence of Cα+ from dehydroxylation of CαH-OH. Furthermore, the NiMo sulfide prefers to catalyze the hydrogenative cleavage of the Cβ-OPh bond connecting with a Cα=O rather than catalyze the hydrogenation of Cα=O back to the original CαH-OH, which further ensures and utilizes the advantages of preoxidation.
Facile and selective hydrogenolysis of β-O-4 linkages in lignin catalyzed by Pd-Ni bimetallic nanoparticles supported on ZrO2
Zhang, Jia-Wei,Cai, Yao,Lu, Guo-Ping,Cai, Chun
supporting information, p. 6229 - 6235 (2016/12/03)
The β-O-4 linkage in lignin can be selectively cleaved by Pd-Ni bimetallic nanoparticles supported on ZrO2 using hydrogen gas as the hydrogen donor under ambient pressure and neutral conditions. Conspicuous enhancement in activity is observed compared with single nickel and palladium catalysts based on the results of experiments and characterization. Moreover, hydrogenation of the produced phenols is tuned by adjusting the amount of NaBH4. The catalyst can be reused over ten times in the model reaction and over five times in the hydrogenolysis of lignin without an obvious change in activity and selectivity.
Two-Step, Catalytic C-C Bond Oxidative Cleavage Process Converts Lignin Models and Extracts to Aromatic Acids
Wang, Min,Lu, Jianmin,Zhang, Xiaochen,Li, Lihua,Li, Hongji,Luo, Nengchao,Wang, Feng
, p. 6086 - 6090 (2016/09/09)
We herein report a two-step strategy for oxidative cleavage of lignin C-C bond to aromatic acids and phenols with molecular oxygen as oxidant. In the first step, lignin β-O-4 alcohol was oxidized to β-O-4 ketone over a VOSO4/TEMPO [(2,2,6,6-tetramethylpiperidin-1-yl)oxyl)] catalyst. In the second step, the C-C bond of β-O-4 linkages was selectively cleaved to acids and phenols by oxidation over a Cu/1,10-phenanthroline catalyst. Computational investigations suggested a copper-oxo-bridged dimer was the catalytically active site for hydrogen-abstraction from Cβ-H bond, which was the rate-determining step for the C-C bond cleavage.
Highly efficient, NiAu-catalyzed hydrogenolysis of lignin into phenolic chemicals
Zhang, Jiaguang,Asakura, Hiroyuki,Van Rijn, Jeaphianne,Yang, Jun,Duchesne, Paul,Zhang, Bin,Chen, Xi,Zhang, Peng,Saeys, Mark,Yan, Ning
supporting information, p. 2432 - 2437 (2014/05/06)
A highly efficient, stable NiAu catalyst that exhibits unprecedented low temperature activity in lignin hydrogenolysis was for the first time developed, leading to the formation of 14 wt% aromatic monomers from organosolv lignin at 170 °C in pure water. the Partner Organisations 2014.
A metal-free, carbon-based catalytic system for the oxidation of lignin model compounds and lignin
Gao, Yongjun,Zhang, Jiaguang,Chen, Xi,Ma, Ding,Yan, Ning
, p. 825 - 834 (2014/07/08)
Nitrogen-containing graphene material (LCN) has been identified as an effective catalyst for the oxidation of β-O-4 and α-O-4 types of lignin model compounds in the presence of tert-butyl hydroperoxide, to provide aromatic aldehydes, acids and other organic chemicals in high yield. The transformations of five lignin model compounds over LCN were investigated systematically. Instrumentation analysis, kinetic study and radical trapping experiments highlight the mechanistic features of the reaction, including: 1) the reaction pathway starts by benzylic C-H or C-OH bond activation, followed by Cα-Cβ or Cα-O bond cleavage, and finally further oxidation of intermediate aromatics; and 2) the reaction follows a free-radical mechanism with all the key steps involving radical species. In addition, the LCN proved to be a highly stable catalyst; no significant activity decrease was observed for four consecutive runs, and X-ray photoelectron spectroscopy analysis indicates negligible decrease in the content of the active nitrogen species in the catalyst. Notably, this new catalytic system can be extended to the oxidative depolymerisation of real lignin, to produce a significant portion of liquefied, low-molecular-mass products. Low mass, high conversion: Nitrogen-containing graphene-based carbon material has been used to establish a metal-free catalytic system for the oxidation of α-O-4 and β-O-4 types of lignin model compounds in the presence of tert-butyl hydroperoxide (see figure). In the oxidative depolymerization of organosolv lignin, a significant portion of liquefied, low-molecular-mass product is produced. Copyright
