Oxidative Depolymerization of Cellulolytic Enzyme Lignin over Silicotungvanadium Polyoxometalates.

Wenbiao Xu,Junyou Shi,Xiangyu Li

doi:10.3390/polym11030564

Wenbiao Xu, Junyou Shi + Show 1 more

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https://doi.org/10.3390/polym11030564

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Journal: Polymers	Publication Date: Mar 26, 2019
Citations: 10	License type: CC BY 4.0

Affiliation: Northeast Forestry University, Beihua University

Abstract

The aim of this study was to explore the catalytic performance of the oxidative depolymerization of enzymatic hydrolysis lignin from cellulosic ethanol fermentation residue by different vanadium substituted Keggin-type polyoxometalates (K5[SiVW11O40], K6[SiV2W10O40], and K6H[SiV3W9O40]). Depolymerized products were analyzed by gel permeation chromatography (GPC), gas chromatography–mass spectrometer (GC/MS), and two-dimensional heteronuclear single quantum coherence nuclear magnetic resonance (2D HSQC NMR) analysis. All catalysts showed an effective catalytic activity. The best result, concerning the lignin conversion and lignin oil production, was obtained by K6[SiV2W10O40], and the highest yield of oxidative depolymerization products of 53 wt % was achieved and the main products were monomer aromatic compounds. The HSQC demonstrated that the catalysts were very effective in breaking the β-O-4 structure, the dominant linkage in lignin, and the GPC analysis demonstrated that the molecular of lignin was declined significantly. These results demonstrate the vanadium substituted silicotungstic polyoxometalates were of highly active and stable catalysts for lignin conversion, and this strategy has the potential to be applicable for production of value-added chemicals from biorefinery lignin.

Highlights

Lignin is a heterogeneous renewable biopolymer and the only feedstock in nature with high carbon content and high aromaticity [1]
The residue was air-dried at room temperature to equilibrium moisture content and the purification of cellulolytic enzyme lignin (CEL) were prepared as the following method: 5.0 g cellulosic ethanol fermentation residue was added to 40 mL 3% NaOH aqueous solution
10 O40 ] with two vanadium atoms exhibited both highest lignin conversion at 87% and lignin evaluated by the measurement of lignin conversion and lignin oil yield

Summary

Introduction

Lignin is a heterogeneous renewable biopolymer and the only feedstock in nature with high carbon content and high aromaticity [1]. It is chemically and physically interlaced with cellulose and hemicelluloses in the plant cell walls. Its complex chemical structure and stable chemical properties make most lignin degradation a highly challenging work [2,3]. The natural lignin is structurally modified under the traditional acid or high temperature fraction or pre-treatment, leading to the irreversible condensation that dramatically affects its further catalytic valorization [2,4,5]. The processes for conversion lignin can be broadly classified into base or acid depolymerization [7], pyrolysis [8,9,10], hydroprocessing [11,12], oxidation [13,14,15], and other depolymerization processes

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