CN114752003A - Method for separating and extracting linear-chain xylan and multi-branched-chain xylan from paper pulp - Google Patents

Abstract

The invention discloses a method for separating and extracting straight-chain xylan and multi-branched-chain xylan from pulp. After pH, sedimentation and centrifugation are carried out to obtain solids and clear liquids, respectively. The solids are washed with ethanol, and then freeze-dried to obtain linear xylan; 2) ethanol is added to the clear liquid obtained in step 1), and alcohol is carried out. Sedimentation, centrifugation, and dialysis of the solid obtained by centrifugation, followed by freeze-drying to obtain multi-branched xylan. The method for separating and extracting straight-chain xylan and multi-branched-chain xylan from pulp has the advantages of simple operation, high separation efficiency, low cost, green environmental protection, high product yield and high product purity, and is suitable for large-scale production. Promote the application.

Description

A method for separating and extracting linear xylan and multi-branched xylan from pulp

technical field

The invention relates to the technical field of biomass materials, in particular to a method for separating and extracting linear xylan and multi-branched xylan from pulp.

Background technique

With the rapid and massive consumption of non-renewable resources such as oil, coal, and natural gas, and the increasing environmental pollution worldwide, the sustainable utilization of resources and energy is imminent, and it is becoming more and more important to seek sustainable alternatives. As an energy source that is expected to replace non-renewable resources in the future, biomass has received more and more attention, and how to develop and utilize biomass renewable resources efficiently, green and low-cost has become an important issue in the sustainable development strategy of today's world.

The wood cell wall is mainly composed of three kinds of high-molecular polymers, lignin, cellulose and hemifiber. It is a complex biomass material with hierarchical structure characteristics. dense structure. Among these polymers, hemicellulose, the physical barrier that surrounds cellulose fibers and protects cellulose from hydrolysis, is the second most abundant component in lignocellulosic biomass. Hemicellulose is a heteropolysaccharide chain composed of different five-carbon and six-carbon monosaccharide units, containing different substituents, which can be mainly divided into xylan, mannan, xyloglucan, galactan and arabinoid Glycans. Xylan is the main raw material for the production of xylo-oligosaccharides and D-xylose, and has broad application prospects in the fields of papermaking, biomass materials, functional foods, and medicine.

Therefore, developing a clean and efficient xylan separation and extraction method to improve the utilization rate of papermaking raw materials is of great significance for the development and utilization of biomass resources.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a method for separating and extracting linear xylan and multi-branched xylan from pulp.

The technical scheme adopted by the present invention is:

A method for separating and extracting linear xylan and multi-branched xylan from pulp comprises the following steps:

1) Disperse the pulp in the alkali solution and extract, filter, get the filtrate and add acid to adjust the pH and carry out sedimentation, centrifuge to obtain solid matter and clear liquid respectively, take the solid matter and wash with ethanol, and then freeze-dry to obtain a straight chain xylan;

2) adding ethanol to the clear liquid obtained in step 1), carrying out alcohol precipitation, centrifuging, taking the solid obtained by centrifugation, dialysis, and then freeze-drying to obtain multi-branched xylan.

Preferably, the pulp in step 1) is unbleached pulp (main components are glucose, xylose, galactose, arabinose and lignin, and the H factor is 300-1000) after the hardwood has been subjected to sulfate cooking.

Further preferably, the pulp described in step 1) is eucalyptus sulfate unbleached pulp.

Preferably, the alkali in the alkali solution in step 1) is selected from at least one of sodium hydroxide and potassium hydroxide.

Preferably, the concentration of the alkali solution in step 1) is 0.2 mol/L to 2 mol/L.

Preferably, the mass-volume ratio of the pulp and the lye in step 1) is 1 g: 20 mL-40 mL.

Preferably, the extraction in step 1) is performed at 30°C to 80°C, and the extraction time is 5h to 20h.

Preferably, the acid in step 1) is acetic acid, and the concentration is 4 mol/L to 6 mol/L.

Preferably, acid is added in step 1) to adjust the pH to 4.5-5.5.

Preferably, the settling time in step 1) is 6h-12h.

Preferably, the washing times of step 1) are 2 to 3 times.

Preferably, the volume ratio of the ethanol to the clear liquid in step 2) is 2:1 to 4:1.

Preferably, the molecular weight cut-off of the dialysis membrane used in the dialysis in step 2) is 2000 Da to 3500 Da.

The beneficial effects of the present invention are: the method for separating and extracting linear xylan and multi-branched xylan from pulp has the advantages of simple operation, high separation efficiency, low cost, environmental protection, and high product yield (75% ~85%), high product purity, suitable for large-scale promotion and application.

Specifically:

1) The method of the present invention can respectively obtain linear xylan with good solubility in organic phase and multi-branched xylan with good solubility in aqueous phase, which is convenient for linear xylan and Multi-branched xylan for further functionalization;

2) The method of the present invention is easy to operate, high in separation efficiency, clean and efficient, low in cost, green and environmentally friendly, and can well realize resource reuse.

Detailed ways

The present invention will be further explained and illustrated below in conjunction with specific embodiments.

Example 1:

A method for separating and extracting straight-chain xylan and multi-branched-chain xylan from pulp, comprising the following steps:

1) 50g of eucalyptus sulphate unbleached pulp (the H factor is 400, the mass percentage of xylose is 35%) is screened and dried and added in 2000mL of sodium hydroxide solution with a concentration of 1mol/L, and pumped at 30°C. Extracted for 10 hours, filtered, the filtrate was taken and added with acetic acid with a concentration of 5 mol/L to adjust the pH to 5.5, fully stirred and then settled for 12 hours, centrifuged to obtain solids and clear liquids, respectively. Obtain 9g of linear xylan;

2) Add 3 times the volume of anhydrous ethanol to the clear liquid obtained in step 1), fully stir and then stand for 12 hours, recover ethanol by vacuum evaporation, centrifuge, take the solid obtained by centrifugation and carry out dialysis, and the dialysis membrane used for dialysis is intercepted. The molecular weight is 2000 Da, and then freeze-drying is performed to obtain 5 g of polybranched xylan (the total yield of linear xylan and polybranched xylan is 80%).

Example 2:

A method for separating and extracting straight-chain xylan and multi-branched-chain xylan from pulp, comprising the following steps:

1) 50g of eucalyptus sulphate unbleached pulp (H factor is 600, and the mass percentage of xylose is 25%) is screened and dried and added in 1500mL concentration of potassium hydroxide solution of 1.5mol/L, at 50°C. Extracted for 8h, filtered, the filtrate was added with acetic acid with a concentration of 5mol/L to adjust the pH to 5.0, fully stirred, and settled for 10h, centrifuged to obtain solids and clear liquids, respectively, and the solids were washed 3 times with ethanol, and then freeze-dried , to obtain 6g of linear xylan;

2) Add 3 times the volume of anhydrous ethanol to the clear liquid obtained in step 1), fully stir and then stand for 12 hours, recover ethanol by vacuum evaporation, centrifuge, take the solid obtained by centrifugation and carry out dialysis, and the dialysis membrane used for dialysis is intercepted. The molecular weight was 2500 Da, and then freeze-dried to obtain 3.38 g of polybranched xylan (the total yield of linear xylan and polybranched xylan was 75%).

Example 3:

A method for separating and extracting straight-chain xylan and multi-branched-chain xylan from pulp, comprising the following steps:

1) 50g of eucalyptus sulphate unbleached pulp (H factor is 800, and the mass percentage of xylose is 20%) is screened and dried and added in 1000 mL of sodium hydroxide solution with a concentration of 2 mol/L, and pumped at 80°C. Extracted for 6 hours, filtered, the filtrate was taken and added with acetic acid with a concentration of 5 mol/L to adjust the pH to 4.5, fully stirred and then settled for 8 hours, centrifuged to obtain solids and clear liquids, respectively. Obtain 5g of linear xylan;

2) Add 3 times the volume of anhydrous ethanol to the clear liquid obtained in step 1), fully stir and then stand for 12 hours, recover ethanol by vacuum evaporation, centrifuge, take the solid obtained by centrifugation and carry out dialysis, and the dialysis membrane used for dialysis is intercepted. The molecular weight is 3000 Da, and then freeze-drying is performed to obtain 3.5 g of polybranched xylan (the total yield of linear xylan and polybranched xylan is 85%).

Test case:

Referring to the method of Example 1, by adjusting the extraction temperature in step 1) (the rest of the operations are exactly the same as in Example 1), test the composition table of hemicellulose extracted at different temperatures (30°C, 50°C and 80°C). , the test results are shown in the following table:

Table 1 Composition of hemicellulose extracted at different extraction temperatures

Note:

Monosaccharide content: the mass fraction of monosaccharide components relative to total polysaccharides, determined by HPAEC-PAD method;

H ₄₀₀ -30: Extraction of hemicellulose from eucalyptus kraft unbleached pulp with H factor of 400 at 30°C;

H _400-50 : Extraction of hemicellulose from eucalyptus kraft unbleached pulp with H factor of 400 at 50°C;

H ₄₀₀ -80: Extraction of hemicellulose from eucalyptus kraft unbleached pulp with H factor of 400 at 80°C;

GXI: linear xylan;

GXS: Multi-branched xylan.

It can be seen from Table 1 that the hemicellulose extracted by the present invention includes linear xylan-based hemicellulose (GXI) and polybranched-chain xylan-based hemicellulose (GXS). The following information can also be obtained: 1) The GXI component uses xylose as the main monosaccharide and contains glucuronic acid branch chains; the GXS component uses xylose as the main monosaccharide, in addition to the glucuronic acid branch chain, it also contains arabinose , branched chain structure of galactose and glucose; 2) With the change of extraction temperature, the obtained hemicellulose components are different, which is manifested in the increase of branched sugar content of multi-branched xylan GXS (for example: arabinoside sugar, galactose, glucose), while the composition of linear xylan is relatively stable.

The above-mentioned embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited by the above-mentioned embodiments, and any other changes, modifications, substitutions, combinations, The simplification should be equivalent replacement manners, which are all included in the protection scope of the present invention.

Claims (10)

1. A method for separating and extracting linear-chain xylan and multi-branched-chain xylan from paper pulp is characterized by comprising the following steps:

1) Dispersing paper pulp in alkali liquor for extraction, filtering, adding acid into filtrate to adjust pH, settling, centrifuging to obtain solid and clear liquid, washing the solid with ethanol, and freeze-drying to obtain linear xylan;

2) adding ethanol into the clear liquid obtained in the step 1), precipitating with ethanol, centrifuging, dialyzing the solid obtained by centrifuging, and freeze-drying to obtain the multi-branched xylan.

2. The method for separating and extracting linear xylan and multi-branched xylan from pulp according to claim 1, wherein: the paper pulp in the step 1) is unbleached paper pulp obtained by cooking broadleaf wood through sulfate.

3. The method for the isolation and extraction of linear xylans and multi-branched xylans from pulp according to claim 1 or 2, wherein: the alkali in the alkali liquor in the step 1) is at least one of sodium hydroxide and potassium hydroxide.

4. The method for separating and extracting linear xylans and multi-branched xylans from pulp according to claim 1 or 2, wherein: the concentration of the alkali liquor in the step 1) is 0.2-2 mol/L.

5. The method for separating and extracting linear xylans and multi-branched xylans from pulp according to claim 1 or 2, wherein: the mass volume ratio of the paper pulp to the alkali liquor in the step 1) is 1g:20 mL-40 mL.

6. The method for the isolation and extraction of linear xylans and multi-branched xylans from pulp according to claim 1 or 2, wherein: the extraction in the step 1) is carried out at the temperature of 30-80 ℃, and the extraction time is 5-20 h.

7. The method for the isolation and extraction of linear xylans and multi-branched xylans from pulp according to claim 1 or 2, wherein: the acid in the step 1) is acetic acid, and the concentration is 4-6 mol/L.

8. The method for the isolation and extraction of linear xylans and multi-branched xylans from pulp according to claim 1 or 2, wherein: adding acid to adjust the pH value to 4.5-5.5 in the step 1).

9. The method for the isolation and extraction of linear xylans and multi-branched xylans from pulp according to claim 1 or 2, wherein: the settling time in the step 1) is 6-12 h.

10. The method for the isolation and extraction of linear xylans and multi-branched xylans from pulp according to claim 1 or 2, wherein: the cut-off molecular weight of a dialysis membrane adopted in the dialysis in the step 2) is 2000 Da-3500 Da.