High Purity and Low Molecular Weight Lignin Nano-Particles Extracted from Acid-Assisted MIBK Pretreatment.

Qilin Zhang,Zongwei Guo,Feng Xu,Haichao Li

doi:10.3390/polym12020378

Abstract

A simple and economical biorefinery method, organosolv methyl isobutyl ketone (MIBK) pretreatment assisted by Lewis acid ferric trichloride hydrolysis, was proposed for fractionating the lignin from extractive-free Eucalyptus powder at the nanoscale, accompanied by another product furfural, derived from hemicellulose. Under the conditions (180 °C, 1 h) optimized based on the best yield of furfural, 40.13% of the acid-insoluble lignin (AIL) could be obtained with a high purity of 100%, a low molecular weight of 767 (Mn) and improved thermostability. The extracted lignin was characterized by its chemical structure, thermostability, homogeneity, molecular weight, and morphology as compared with milled wood lignin (MWL). The results showed significant variations in chemical structures of the extracted lignin during the pretreatment. Specifically, the aryl ether linkage and phenylcoumarans were broken severely while the resinols were more resistant. The G-type lignin was more sensitive to degradation than the S-type, and after the pretreatment, H-type lignin was formed, indicating the occurrence of a demethoxylation reaction at high temperature. Moreover, the lignin nano-particles were identified visually by AFM and TEM images. The dynamic light scattering (DLS) showed that the average diameter of the measured samples was 131.8 nm, with the polydispersity index (PDI) of 0.149. The MIBK-lignin nano-particles prepared in our laboratory exhibit high potentials in producing high functional and valuable materials for the application in wide fields.

Highlights

Due to abundant greenhouse gas and severe environmental problems caused by fossil fuels and the limited non-renewable energy, the pathway of valorizing the renewable lignocellulosic biomass for materials, chemicals, and biofuels has attracted many interests in recent decades [1,2]
Due to the mild extraction conditions, milled wood lignin (MWL) yield is commonly below 20% based on the lignin existed in the original biomass, and in this work, the MWL yield from Eucalyptus was
Under the conditions (180 ◦ C, 1 h), 40.13% of the acid-insoluble lignin from Eucalyptus biomass by the Lewis acid ferric trichloride hydrolysis modified organosolv in original biomass can be obtained with a high purity of 100% and a low molecular weight of 767 (Mn )

Summary

Introduction

Due to abundant greenhouse gas and severe environmental problems caused by fossil fuels and the limited non-renewable energy, the pathway of valorizing the renewable lignocellulosic biomass for materials, chemicals, and biofuels has attracted many interests in recent decades [1,2]. Lignocellulose is mainly composed of cellulose, hemicellulose, and lignin. Cellulose and hemicellulose are classes of polymers containing one or several monosaccharide units. For cellulose, a component of biomass in yielding specialty chemicals and functional materials as a result of the simple chemical composition and crystalline structure [3]. Cellulose is well protected by the surrounding biomass recalcitrance, a barrier structured by hemicellulose and lignin. Lignin is the main factor hindering the cellulose valorization; on the other hand, it is one of the few natural large-scale sources of aromatic compounds [4]. Three types of methoxylated phenylpropanoid units including p-hydroxyphenyl (H), guaiacyl (G), and syringyl (S) coupled by aryl ether (α–O–4, β–O–4, and 4–O–5) or carbon-carbon linkage (β–β, β–1, β–5, and 5–5) construct such complex lignin

Methods

Results

Conclusion