A method for fractionally extracting lignin and xylooligosaccharides in papermaking black liquor

Abstract

The invention provides a method for classifying and extracting xylogen and xylo-oligosaccharide in papermaking black liquid. The method mainly comprises the following steps: diluting papermaking blackliquid, regulating the pH value, ageing, standing, and performing centrifugal separation to obtain centrifugate and a solid precipitate; performing rotary evaporation concentration on the centrifugate, dripping ethanol to precipitate, and performing centrifugal separation to obtain solid xylo-oligosaccharide; purifying and dissolving the solid precipitate with a methanol / acetone mixed solution; dripping an ethyl acetate solvent to precipitate, and performing centrifugal separation to obtain xylogen F1 and centrifugate; performing rotary evaporation concentration on the centrifugate, drippingan ethyl acetate / petroleum ether mixed solution to precipitate, and performing centrifugal separation to obtain xylogen F2 and centrifugate; and performing rotary evaporation concentration on the centrifugate, dripping petroleum ether to precipitate, and performing centrifugal separation, thereby obtaining xylogen F3 and xylogen F4 in the centrifugate. The method disclosed by the invention is capable of realizing classification and separation of xylogen and recycling of the xylo-oligosaccharide in bagasse papermaking black liquid, is wide in application range, simple in process and reliable intechnology and has actual application and popularization value.

Description

technical field [0001] The invention belongs to the field of waste water treatment in environmental protection technology, and specifically relates to a technique for extracting lignin, xylooligosaccharides and lignin fractionation from papermaking black liquor. Background technique [0002] In my country, non-wood fiber is the main raw material of most paper mills, and its main chemical components include cellulose, lignin and hemicellulose (ie polypentose). During the alkaline cooking process, the lignin and hemicellulose in the bagasse raw material are dissolved in the alkali solution to form a raw slurry containing water, residual alkali, cellulose, alkali lignin and hemicellulose. The original slurry is separated by slurry, and the non-alkali-soluble cellulose (pulp) is separated, and then sent to washing and bleaching processes for further processing to obtain pulp, and the waste liquid containing solids is called black liquor because of its black color. Black liquor ...

AI Technical Summary

Problems solved by technology

However, lignin has defects such as complex chemical composition, unclear molecular structure, and poor uniformity, which seriously limit the development and application of high-value lignin products.

[0009] At present, methods such as ultrafiltration and organic solvent extraction are often used to improve the homogeneity of lignin, but these methods have problems such as high production costs and difficulty in industrialization