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Method for separating and extracting lignin by using ultrafiltration membrane

A lignin and ultrafiltration membrane technology, applied in chemical recovery and other directions, can solve the problems of acid-base neutralization loss, increase, and chemical reagents cannot be recycled, and achieve the effect of reducing acid-base loss

Inactive Publication Date: 2011-04-27
INST OF PROCESS ENG CHINESE ACAD OF SCI +1
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

For the extraction of lignin from the black liquor obtained by the alkaline method, the acid analysis method has the least investment because of its mature and reliable technology, and is still a commonly used method at present [Hunan Paper, 2008, 1: 13-15], by adding acid to reduce the pH value Precipitate the lignin, neutralize the acid and alkali in the process of adding acid to change the pH value, and cause the loss of acid and alkali at the same time, and the added chemical reagents cannot be recycled
For the extraction of lignin from the black liquor obtained by the sulfite method, the alkali analysis method is mainly used to precipitate the lignin by increasing the pH value, which also has the problem of loss caused by acid-base neutralization

Method used

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  • Method for separating and extracting lignin by using ultrafiltration membrane

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Effect test

Embodiment 1

[0021] The straw or wood is sent into the cooking tank after being crushed, and the cooking conditions are: the amount of alkali (NaOH) 4%. The liquid ratio is 1:6, the heating time is 1h, the maximum temperature is 155°C, and the holding time is 2h. The liquid is filtered with a polyvinyl chloride ultrafiltration membrane with a molecular weight cut-off of 1000, and the lye that passes through the ultrafiltration membrane is sent to the cooking tank for recycling. The liquid intercepted by the ultrafiltration membrane is a lignin solution, and the lignin concentration in it is After being improved, it is further concentrated by using a three-effect negative pressure evaporator, and the lignin concentration in the concentrated solution reaches 53%, and finally the lignin solution is dried into a finished lignin by a spray drying method.

Embodiment 2

[0023] After the straw or wood is crushed, it is sent to the cooking tank, and the kraft pulping method is used for cooking conditions: the amount of alkali used (Na 2 O meter) 4%, vulcanization degree 25%, liquid ratio 1:4, heat up for 1.75h, keep warm for 2.5h, the highest temperature is 168°C (120°C for small deflation), cool down to 60°C after cooking, and then use a 300-mesh board The frame filter separates the boiled material, and the separated solid is sent to other uses, while the liquid is filtered by a polyvinylidene fluoride ultrafiltration membrane with a molecular weight cut-off of 10,000, and the lye that passes through the ultrafiltration membrane is sent to the cooking tank for circulation Utilization, the liquid intercepted by the ultrafiltration membrane is a lignin solution, and the lignin concentration in it is increased, and further concentrated using a three-effect negative pressure evaporator, and the lignin concentration in the concentrated solution reac...

Embodiment 3

[0025] Straw or wood is crushed and sent to the cooking tank, using sulfite pulping method. Cooking conditions: total acid 4.2%, ratio of compound acid to free acid 2.3, liquid ratio 1:7, maximum temperature 155°C, holding time 135min, cooking After the end, the temperature is lowered to 60°C, and then the cooked material is separated by a screw extruder, and the separated solid is sent to other uses, while the liquid is filtered by a polyacrylonitrile ultrafiltration membrane with a molecular weight cut-off of 20,000. The lye of the membrane is sent to the cooking tank for recycling. The liquid intercepted by the ultrafiltration membrane is a lignin solution, and the lignin concentration in it is increased. It is further concentrated by a three-effect negative pressure evaporator. The lignin concentration in the concentrated solution reaches 50%, and finally the lignin solution is dried into finished lignin by spray drying method.

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Abstract

The invention relates to a method for separating and extracting lignin by using an ultrafiltration membrane, and belongs to the field of the separation and extraction of lignin in a straw or wood. The method comprises the following steps of: dissolving the lignin in the straw or the wood by a base method or a sulfite method, and performing solid-liquid separation on the processed material, wherein a separated solid is used for papermaking and the like; separated liquid is filtered by the ultrafiltration membrane, permeable liquid is recycled and is used for processing the straw or the wood, and trapped liquid serving as concentrated lignin solution is conveyed to an evaporator for further concentration, and is dried to prepare finished lignin; and the lignin can be used for preparing bonding agents, complexing agents and the like. In the method, the problem of acid-base neutralization is solved, so the losses of acid and base are reduced, and chemical reagents added during processing by the base method or the sulfite method can be recycled.

Description

technical field [0001] The invention belongs to the field of lignin separation and extraction, in particular to a method for ultrafiltration membrane separation and extraction of lignin. Background technique [0002] The main components of straw or wood are cellulose, hemicellulose and lignin. Cellulose is a macromolecular polysaccharide composed of glucose, which is insoluble in water and general organic solvents. Cellulose is an important raw material for papermaking, and products made from cellulose are also widely used in plastics, explosives, electrical and scientific research equipment, etc. Lignin is an aromatic compound that widely exists in the plant kingdom. All plants except mosses and fungi contain lignin. It is the only aromatic compound that can be obtained from renewable resources in industry, and its content is second only to cellulose , and regenerated at a rate of 50 billion tons per year. The structure of lignin is very complex. It is a non-crystalline ...

Claims

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Application Information

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IPC IPC(8): C08H7/00
CPCY02P20/582
Inventor 陈洪章丁文勇马保华生晓东
Owner INST OF PROCESS ENG CHINESE ACAD OF SCI
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