Method for separating high-purity lignin

Abstract

The invention discloses a method for separating high-purity lignin by treating agricultural and forestry wastes with a green solvent. The method comprises the following steps that 1, a hydrogen bond acceptor and a hydrogen bond donor are heated and dissolved to obtain a low eutectic solvent system of a uniform transparent solution; 2, the agricultural and forestry wastes serve as raw materials, alow eutectic solvent serves as a reaction solvent, and the raw materials and the reaction solvent react in a reaction kettle; 3, after the reaction is completed, cooling is conducted, solid and liquidare centrifugally separated, and the separated liquid is precipitated through deionized water, centrifuged and freeze-dried to obtain the high-purity lignin; 4, rotary evaporation is carried out on the liquid obtained through centrifugation to recover the eutectic solvent. The reaction raw materials in the separation method are the agricultural and forestry wastes, low in cost and environmentallyfriendly, and the low eutectic solvent is easy to prepare, low in cost, free of toxins, recyclable and free of a complex preparation process. According to the method, the treatment conditions are mild, the extraction process is simple, the reaction is easy to control, and the energy consumption is effectively reduced. The obtained lignin is high in purity.

Description

technical field [0001] The invention belongs to the field of biological energy, and in particular relates to a method for separating high-purity lignin from agricultural and forestry wastes by using a green solvent. Background technique [0002] Lignin is the third largest natural organic polymer in the plant kingdom, only a small part is used to produce chemicals or polymer materials, and most of it is burned directly, causing serious resource waste and environmental pollution. If these lignins can be fully utilized to turn waste into treasure, it will not only solve the environmental problems caused by lignin combustion, but also solve the problems of high cost and low economic benefits in the current biomass refining process. Lignin is composed of phenylpropane structural units connected by ether bonds and carbon-carbon bonds. It contains a large number of active functional groups such as carbonyl groups, phenolic hydroxyl groups, and alcoholic hydroxyl groups. It has bro...

AI Technical Summary

Problems solved by technology

[0004] However, the above-mentioned prior art has at least the following disadvantages: when organic acid extracts and separates lignin, the danger of liquid strong acid is high, the requirements for corrosion resistance of reaction equipment are high, and the acidolysis solution after pretreatment requires a large amount of alkali to neutralize, and there is difficulty in recovery. And other issues

The cost of lignin extraction by ionic liquid is high and the raw material solvent needs to be pre-treated, which increases operating costs and limits its industrialization.

When extracting lignin with deep eutectic solvent, there are long reaction time, high reaction temperature, complicated separation procedure and the use of acid-base solution in the separation process, which will cause problems such as corrosion of equipment and environmental pollution.