Technique for extracting lignin from biomass raw materials

Abstract

The invention relates to a technique for extracting lignin, in particular to a technique of utilizing organic acid to extract the lignin from biomass raw materials by a catalytic action of hydrogen peroxide. According to the method, the lignin is obtained by extracting the biomass raw materials boiled by organic acid formed by methanoic acid and acetic acid by the catalytic action of hydrogen peroxide; a whole technique route is simple; the energy consumption is lower; and an extraction ratio of the lignin reaches 80-90%.

Description

technical field [0001] The invention relates to a lignin extraction process, in particular to a process for extracting lignin from biomass raw materials by using organic acids. Background technique [0002] Lignin is a valuable chemical raw material. High-purity sulfur-free lignin can be used as polymer additives such as phenolic resins, polyurethane foams, and epoxy resins, as well as soil improvers, pesticide slow-release agents, etc. Lignin is used in These aspects can make its added value much higher than that of recovering heat after combustion as fuel. At present, lignin is mainly produced as a by-product of pulping and papermaking, such as lignosulfonate, kraft lignin, etc. However, these lignins contain sulfur and have low purity, complex components, wide molecular weight distribution, low viscosity, high dispersion, poor processability, and almost no thermoplastic properties, which greatly limit their industrial applications. Therefore, the development of a clean ...

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Problems solved by technology

However, this patent also has the following disadvantages: 1. From the description in the manual, it can be seen that the process uses organic acid mixed with a catalyst represented by sulfuric acid for the first step of catalysis, and a catalyst needs to be added for catalysis during the reaction; 2. This process uses organic acid and a catalyst represented by sulfuric acid to cook biomass together. In the step of distilling organic acid, if the distillation of organic acid is not complete, the lignin cannot be completely precipitated. If the organic acid is completely distilled, add it The concentration of sulfuric acid increases, which will carbonize the lignin and affect the extraction rate of lignin; 3. Although the same organic acid is used for extracting and washing cellulose in the whole process, and the collected pretreatment liquid and washing liquid are directly used In the reaction kettle that is circulated to the first step, a large amount of lignin and pentose sugar solution dissolved therein also accumulate in the whole mixed liquor. In view of the limitation of the saturation degree of organic acid extraction, the effectiveness of the mixed black liquor to extract lignin will be reduced. Therefore, although this step is a cyclic reaction, it has little effect on the overall extraction efficiency; 4. The black liquor obtained by mixing needs to be circulated for more than 3 times before being distilled to separate the organic acid and dilute the obtained concentrated The liquid makes the lignin precipitate, which will cause a huge amount of black liquor and concentrated liquid to be processed at one time, which not only affects the treatment efficiency but also makes it difficult to realize the continuity of the process; 5. It can be seen from the manual that the lignin extraction in this process The extraction rate is only 6-16%, and the extraction rate of the whole process is relatively low

Although this method solves the problem of adding a catalyst in the process of cooking biomass, since this method is mainly used for pulp preparation, its purpose is to retain cellulose and part of hemicellulose to the greatest extent, and the entire process design is based on This is for the purpose, but the loss of lignin is not considered, and the treatment process for lignin is not given, so this process is not applicable to the process with lignin as the extraction product

[0007] "Research on Milox Solvent Method for Bleaching Bamboo Pulp" (Liang Fang, Liu Yakang, etc., Zhonghua Paper Industry, 2007, 28 (4), 40-43), shows that adopting formic acid and hydrogen peroxide as a kind of solvent pulping of cooking chemicals method to achieve the effect of dissolving or softening lignin, but the above method is a long-term steaming process at low temperature, the presence of a large amount of formic acid destroys the carbohydrates in the raw material, and because a small amount of acetic acid is produced during the hydrolysis of the raw material, The removal rate of hemicellulose in the raw material is reduced, and if you want to separate a small amount of acetic acid from formic acid in the whole process, the steps are complicated and difficult to separate. Therefore, the above method is not suitable for the extraction of lignin

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