A process for extracting lignin from lignocellulosic biomass

Abstract

The invention relates to a lignin extraction process, and particularly relates to a process for extracting lignin from lignocellulose biomass by using organic acids. The method of the invention extracts lignin by performing acidolysis of lignocellulose biomass with a mixed organic acid of formic acid with a concentration of 5-90% and acetic acid with a concentration of 5-90%; the lignin extraction rate is up to 85%; the whole process route is simple, and low in energy consumption; the process can be used for combined production of cellulose and pentose, and even products such as furfural and the like.

Description

technical field [0001] The invention relates to a lignin extraction process, in particular to a process for extracting lignin from lignocellulose by using organic acids. Background technique [0002] Lignin is a class of substances composed of polymerized aromatic alcohols, present in woody tissues, and its main function is to harden the cell wall by forming an interwoven network. Lignin is mainly located between cellulose fibers and acts as an anti-compression. In woody plants, lignin accounts for 25% and is the second most abundant organic matter in the world, after cellulose. [0003] With the deepening of human understanding of environmental pollution and resource crisis, the renewable and degradable properties of natural polymers have attracted increasing attention. The recycling of waste and the utilization of renewable resources are major issues in contemporary economic and social development, and are also new requirements for contemporary science and technology. I...

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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 acidify the biomass together. In the step of distilling the organic acid, if the distillation of the organic acid is not complete, the lignin cannot be completely precipitated. If the organic acid is completely distilled, add The concentration of sulfuric acid in it will increase, which will carbonize the lignin in it 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 It is used to circulate to the reaction kettle of the first step, but a large amount of dissolved lignin and pentose sugar solution also accumulate in the whole mixed liquor. In view of the saturation limit of organic acid extraction, the effective degree of the mixed black liquor to extract lignin 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 and then evaporated to separate the organic acid and dilute the obtained The concentrated solution causes lignin to separate out, which will cause a huge amount of black liquor and concentrated solution 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 specification that the lignin in the 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 acidolysis of biomass, since this method is mainly used for the preparation of pulp, its purpose is to retain cellulose and part of hemicellulose to the greatest extent, and its entire process design is For this purpose, 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 of extracting lignin

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