Digestion on The Nature of Lignin

霍滿堂 侯哲生 房巖朝

【Abstract】Through the analysis of lignins structure， chemical properties， lignins modification and the application of lignin， we can better understand the nature of lignin.

【Key words】structure； chemical properties； modification； lignin

【作者簡介】霍滿堂（1992-），男，漢族，河北衡水人，吉林化工學院，碩士在讀，研究方向：制漿造紙；侯哲生，房巖朝，吉林化工學院。

【基金項目】吉林市科技創新創業大賽，項目名稱：秸稈制漿，編號：201851889。

1. Introduction

Lignin is the second most abundant polymer in nature， and its characteristics such as reproducibility， non-toxicity， biodegradation and low price （mainly from the by-products of pulping） make its comprehensive utilization of lignin become a hot spot in todays petroleum and other chemical resources.

2. Structure of Lignin

Lignin is an amorphous polymer with complex structure. Until now， we can only recognize its constituent elements， connection mode， basic component units and basic structure. Lignin is a kind of three alcohol monomers connected by carbon， carbon and ether bonds， but it is not a simple connection. Lignin contains a variety of structures， such as dibenzodiazepine， benzodioxepine and spironadienone.

3. Chemical Properties of Lignin

Lignin contain a variety of functional groups， the functional type determines the possible chemical reactions， lignin containing functional groups categories include： aromatic base， alcohol， phenol hydroxyl， carbonyl and carboxyl， hydroxyl methoxyl group， sulfonic group， such as， this determines the lignin chemical reactions can happen include： halogenation， nitration， phenol， graft copolymerization， alkylation and a series of chemical reactions.

At present， fiber is mainly used in two aspects， namely pulping and second-generation ethanol technology. During pulping， the chemical reactions of lignin mainly include elimination reaction， nucleophilic substitution reaction and REDOX reaction.

4. Lignins modification

The modification of lignin can change the properties of lignin through chemical reaction， introducing new functional groups or changing the number of functional groups in lignin. Lignin modification mainly includes sulfonation， hydroxymethylation， amine methylation， alkylation， etc. In addition， graft copolymerization is also one of the common means of lignin modification

5. Application of Lignin

With the depletion of fossil energy and various kinds of pollution caused by the use of fossil energy， people began to invest more and more in the utilization of biomass. Lignin， as the only substance containing benzene ring in nature and its unique physical and chemical properties， has been increasingly applied in life.

The application of lignin mainly includes three aspects. First， lignin is directly used as chemical reaction material to prepare phenolic resin， polyurethane， epoxy resin， etc. The other is the direct utilization of lignin， such as surfactant， flocculant， etc. Third， lignin is used as filling agent to modify rubber and so on. Due to its structure and hydrogen bond， lignin cannot be dispersed well in the matrix， so it should be chemically modified before use.

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