Dataset Information

Highly selective cleavage C-O ether bond of lignin model compounds over Ni/CaO-H-ZSM-5 in ethanol.

ABSTRACT: Herein, 2-(2-methoxyphenoxy)-1-phenylethanol (β-O-4), 2-methoxyphenyl anisole (α-O-4) and 4-phenoxyphenol (4-O-5) were selected as typical lignin model compounds. Given the effectiveness of traditional acid-base catalysts for lignin depolymerisation, a novel Ni/CaO-H-ZSM-5(60) catalyst was prepared to investigate the difficulty level of C-O bond of three model compounds cleavage in ethanol. It was observed that Ni/CaO-H-ZSM-5(60) had prominent performance on the C-O bond cleavage at very mild conditions (140 °C, 1 MPa H₂). Among them, the C-O bond of α-O-4 and β-O-4 could be completely cleaved within 60 min. Although the C-O bond of 4-O-5 had high bond energy, 41.2% of conversion was occurred in 60 min. The introduction of CaO could regulate the acidity of H-ZSM-5 to enhance the ability to break C-O bonds. Moreover, the possible pathways of C-O ether bonds in three lignin model compounds cleavage were proposed in order to selectively obtain target products from the raw lignin degradation.

SUBMITTER: Guo J

PROVIDER: S-EPMC6661968 | biostudies-literature | 2019 Dec

REPOSITORIES: biostudies-literature

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Highly selective cleavage C-O ether bond of lignin model compounds over Ni/CaO-H-ZSM-5 in ethanol.

Guo J J Ma Yu L YL Yu Jia Y JY Gao Yu J YJ Ma Ning X NX Wu Xiao Y XY

BMC chemistry 20190326 1

Herein, 2-(2-methoxyphenoxy)-1-phenylethanol (β-O-4), 2-methoxyphenyl anisole (α-O-4) and 4-phenoxyphenol (4-O-5) were selected as typical lignin model compounds. Given the effectiveness of traditional acid-base catalysts for lignin depolymerisation, a novel Ni/CaO-H-ZSM-5(60) catalyst was prepared to investigate the difficulty level of C-O bond of three model compounds cleavage in ethanol. It was observed that Ni/CaO-H-ZSM-5(60) had prominent performance on the C-O bond cle ...[more]

PMID: 31384784

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Project description:Lignin is the most abundant renewable feedstock to produce aromatic chemicals, however its depolymerisation involves the breaking of several C-O and C-C inter-unit linkages that connect smaller aromatic units that are present in lignin. Several strategies have been reported for the cleavage of the C-O inter-unit linkages in lignin. However, till today, only a few methodologies have been reported for the effective breaking or the conversion of the recalcitrant C-C inter unit linkages in lignin. Here we report the ruthenium ion catalysed oxidative methodology as an effective system to activate or convert the most recalcitrant inter unit linkages such as β-5 and 5-5' present in lignin. Initially, we used biphenyl as a model compound to study the effectiveness of the RICO methodology to activate the 5-5' C-C linkage. After 4 h reaction at 22 °C, we achieved a 30% conversion with 75% selectivity towards benzoic acid and phenyl glyoxal as the minor product. To the best of our knowledge this is the first ever oxidative activation of the C-C bond that connects the two phenyl rings in biphenyl. DFT calculation revealed that the RuO4 forms a [3 + 2] adduct with one of the aromatic C-C bonds resulting in the opening of the phenyl ring. Biphenyl conversion could be increased by increasing the amount of oxidant; however, this is accompanied by a reduction in the carbon balance because of the formation of CO2 and other unknown products. We extended this RICO methodology for the oxidative depolymerisation of lignin model hexamer containing β-5, 5-5' and β-O-4 linkages. Qualitative and quantitative analyses of the reaction mixture were done using 1H, 13C NMR spectroscopy methods along with GC-MS and Gel Permeation Chromatographic (GPC) methods. Advanced 2D NMR spectroscopic methods such as HSQC, HMBC and 31P NMR spectroscopy after phosphitylation of the mixture were employed to quantitatively analyse the conversion of the β-5, 5-5' and β-O-4 linkages and to identify the products. After 30 min, >90% of the 5-5' and linkages and >80% of the β-5' are converted with this methodology. This is the first report on the conversion of the 5-5' linkage in lignin model hexamer.

Dataset Information

Highly selective cleavage C-O ether bond of lignin model compounds over Ni/CaO-H-ZSM-5 in ethanol.

Publications

Highly selective cleavage C-O ether bond of lignin model compounds over Ni/CaO-H-ZSM-5 in ethanol.

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