CN114044836A - Method for extracting hemicellulose from chemical pulp - Google Patents
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- CN114044836A CN114044836A CN202111438066.5A CN202111438066A CN114044836A CN 114044836 A CN114044836 A CN 114044836A CN 202111438066 A CN202111438066 A CN 202111438066A CN 114044836 A CN114044836 A CN 114044836A
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- 229920002488 Hemicellulose Polymers 0.000 title claims abstract description 62
- 229920001131 Pulp (paper) Polymers 0.000 title claims abstract description 53
- 238000000034 method Methods 0.000 title claims abstract description 37
- 239000000463 material Substances 0.000 claims abstract description 120
- 239000012528 membrane Substances 0.000 claims abstract description 76
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims abstract description 45
- 239000000919 ceramic Substances 0.000 claims abstract description 31
- 238000001728 nano-filtration Methods 0.000 claims abstract description 31
- 238000011282 treatment Methods 0.000 claims abstract description 25
- 238000001035 drying Methods 0.000 claims abstract description 19
- 239000007788 liquid Substances 0.000 claims abstract description 15
- 238000000926 separation method Methods 0.000 claims abstract description 13
- 238000007598 dipping method Methods 0.000 claims abstract description 8
- 239000000843 powder Substances 0.000 claims abstract description 7
- 239000002244 precipitate Substances 0.000 claims abstract description 7
- 239000002253 acid Substances 0.000 claims abstract description 5
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 21
- 239000000706 filtrate Substances 0.000 claims description 18
- 239000002023 wood Substances 0.000 claims description 17
- 239000007921 spray Substances 0.000 claims description 16
- 238000000502 dialysis Methods 0.000 claims description 14
- 239000002893 slag Substances 0.000 claims description 12
- 238000010411 cooking Methods 0.000 claims description 8
- 239000004744 fabric Substances 0.000 claims description 6
- 238000012545 processing Methods 0.000 claims description 6
- QAOWNCQODCNURD-UHFFFAOYSA-N sulfuric acid Substances OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims description 6
- 244000166124 Eucalyptus globulus Species 0.000 claims description 5
- 241000219000 Populus Species 0.000 claims description 4
- 239000002699 waste material Substances 0.000 abstract description 3
- 238000005470 impregnation Methods 0.000 abstract 3
- 238000004537 pulping Methods 0.000 description 7
- 239000000047 product Substances 0.000 description 6
- 239000000835 fiber Substances 0.000 description 5
- 239000002994 raw material Substances 0.000 description 5
- 238000000605 extraction Methods 0.000 description 4
- 239000007787 solid Substances 0.000 description 4
- 239000000126 substance Substances 0.000 description 4
- 235000000346 sugar Nutrition 0.000 description 3
- SRBFZHDQGSBBOR-IOVATXLUSA-N D-xylopyranose Chemical compound O[C@@H]1COC(O)[C@H](O)[C@H]1O SRBFZHDQGSBBOR-IOVATXLUSA-N 0.000 description 2
- PYMYPHUHKUWMLA-UHFFFAOYSA-N arabinose Natural products OCC(O)C(O)C(O)C=O PYMYPHUHKUWMLA-UHFFFAOYSA-N 0.000 description 2
- SRBFZHDQGSBBOR-UHFFFAOYSA-N beta-D-Pyranose-Lyxose Natural products OC1COC(O)C(O)C1O SRBFZHDQGSBBOR-UHFFFAOYSA-N 0.000 description 2
- 229910052799 carbon Inorganic materials 0.000 description 2
- 229920002678 cellulose Polymers 0.000 description 2
- 239000001913 cellulose Substances 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 238000011160 research Methods 0.000 description 2
- 238000002791 soaking Methods 0.000 description 2
- 230000009466 transformation Effects 0.000 description 2
- 229920000875 Dissolving pulp Polymers 0.000 description 1
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 1
- 244000302661 Phyllostachys pubescens Species 0.000 description 1
- 235000003570 Phyllostachys pubescens Nutrition 0.000 description 1
- 240000008042 Zea mays Species 0.000 description 1
- 235000005824 Zea mays ssp. parviglumis Nutrition 0.000 description 1
- 235000002017 Zea mays subsp mays Nutrition 0.000 description 1
- 239000003513 alkali Substances 0.000 description 1
- WQZGKKKJIJFFOK-PHYPRBDBSA-N alpha-D-galactose Chemical compound OC[C@H]1O[C@H](O)[C@H](O)[C@@H](O)[C@H]1O WQZGKKKJIJFFOK-PHYPRBDBSA-N 0.000 description 1
- PYMYPHUHKUWMLA-WDCZJNDASA-N arabinose Chemical compound OC[C@@H](O)[C@@H](O)[C@H](O)C=O PYMYPHUHKUWMLA-WDCZJNDASA-N 0.000 description 1
- 238000004061 bleaching Methods 0.000 description 1
- 210000004027 cell Anatomy 0.000 description 1
- 239000013043 chemical agent Substances 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 235000005822 corn Nutrition 0.000 description 1
- 238000003912 environmental pollution Methods 0.000 description 1
- 230000032050 esterification Effects 0.000 description 1
- 238000005886 esterification reaction Methods 0.000 description 1
- 238000006266 etherification reaction Methods 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 229930182830 galactose Natural products 0.000 description 1
- 210000001724 microfibril Anatomy 0.000 description 1
- 150000002772 monosaccharides Chemical class 0.000 description 1
- 238000004064 recycling Methods 0.000 description 1
- 239000002910 solid waste Substances 0.000 description 1
- 239000010902 straw Substances 0.000 description 1
- 150000008163 sugars Chemical class 0.000 description 1
- 210000001519 tissue Anatomy 0.000 description 1
- 229920001221 xylan Polymers 0.000 description 1
- 150000004823 xylans Chemical class 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08B—POLYSACCHARIDES; DERIVATIVES THEREOF
- C08B37/00—Preparation of polysaccharides not provided for in groups C08B1/00 - C08B35/00; Derivatives thereof
- C08B37/0003—General processes for their isolation or fractionation, e.g. purification or extraction from biomass
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08B—POLYSACCHARIDES; DERIVATIVES THEREOF
- C08B37/00—Preparation of polysaccharides not provided for in groups C08B1/00 - C08B35/00; Derivatives thereof
- C08B37/0006—Homoglycans, i.e. polysaccharides having a main chain consisting of one single sugar, e.g. colominic acid
- C08B37/0057—Homoglycans, i.e. polysaccharides having a main chain consisting of one single sugar, e.g. colominic acid beta-D-Xylans, i.e. xylosaccharide, e.g. arabinoxylan, arabinofuronan, pentosans; (beta-1,3)(beta-1,4)-D-Xylans, e.g. rhodymenans; Hemicellulose; Derivatives thereof
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- Chemical & Material Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Health & Medical Sciences (AREA)
- Engineering & Computer Science (AREA)
- Molecular Biology (AREA)
- General Health & Medical Sciences (AREA)
- Biochemistry (AREA)
- Materials Engineering (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Medicinal Chemistry (AREA)
- Polymers & Plastics (AREA)
- Organic Chemistry (AREA)
- Sustainable Development (AREA)
- Polysaccharides And Polysaccharide Derivatives (AREA)
Abstract
The invention discloses a method for extracting hemicellulose from chemical pulp, which specifically comprises the following steps: step 1) dipping chemical pulp in 5-20% sodium hydroxide solution for 0.5-4 h at the temperature of 40-80 ℃ to obtain a material A; step 2) carrying out solid-liquid separation treatment on the material A to obtain chemical pulp and impregnation liquid after impregnation, and collecting the impregnation liquid as a material B; step 3), pretreating the material B by using a filter bag, then treating the material B by using a nanofiltration membrane, and collecting concentrated solution to obtain a material C; step 4), adding acid into the material C to obtain a precipitate which is a material D; step 5), treating the material D by a ceramic membrane, and collecting a concentrated solution as a material E; and 6) drying the material E to obtain hemicellulose dry powder. The invention has the advantages of high efficiency, low cost, no generation of three wastes, small influence on environment and the like.
Description
Technical Field
The invention relates to the technical field of resource recycling, in particular to a method for extracting hemicellulose from chemical pulp.
Background
The chemical pulping is a method for obtaining paper pulp by adopting a chemical agent through high-temperature cooking post-treatment, the conditions of the cooking process of the chemical pulping are severe, the delignification effect on raw materials is better, the fiber softness is good, and the bleaching is easy. The obtained pulp also has the advantages of high long fiber content, low fiber finishing rate and the like, and is one of the mainstream pulping methods in recent years. The chemical pulp contains more hemicellulose, is not well utilized in the papermaking industry, and needs post-treatment in partial dissolving pulp, thus increasing the cost.
Hemicellulose is one of the three elements in wood and is contained in chemical pulp in a high content. Hemicellulose is a heteromultimer composed of several different types of monosaccharides, these sugars being five-and six-carbon sugars, including xylose, arabinose, galactose, and the like. Hemicellulose xylan, which accounts for 50% of the total amount in the woody tissue, is bound to the surface of cellulose microfibrils and is interconnected, and these fibers constitute a rigid interconnected network of cells. The pure hemicellulose is light yellow, has better hydrophilicity, and is easier to absorb water and swell than the cellulose. In addition, the hemicellulose structure contains various five-carbon sugars, is easy to generate chemical reaction and modify, and can perform reactions such as esterification and etherification. The method can be used as a production raw material of various chemical products, for example, the method for producing alcohol by using hemicellulose as a raw material is a research hotspot at home and abroad.
At present, chemical pulping processes are adopted by a plurality of domestic pulping and papermaking enterprises, a large amount of chemical pulp is produced every year, and the semi-fiber is not regarded as important. The solar paper industry, the Juntai paper industry and the Qingshan paper industry have hundreds of thousands of tons of chemical pulp pulping capacity, and the hemicellulose in the chemical pulp is hardly utilized. There are many researches on hemicellulose extraction at home and abroad, but most of raw materials are corn stalks, moso bamboos, straws and the like.
Therefore, there is a need in the art to develop a process method for extracting hemicellulose from chemical pulp, so as to realize efficient utilization of hemicellulose in chemical pulp and realize high-value utilization of resources.
Disclosure of Invention
In view of the above-mentioned drawbacks of the prior art, it is an object of the present invention to propose a method for extracting hemicellulose from chemical pulp.
The purpose of the invention is realized by the following technical scheme:
a method for extracting hemicellulose from chemical pulp specifically comprises the following steps:
step 1) dipping chemical pulp in 5-20% sodium hydroxide solution for 0.5-4 h at the temperature of 40-80 ℃ to obtain a material A;
step 2) performing solid-liquid separation treatment on the material A to obtain chemical pulp and steeping liquor after steeping, and collecting the steeping liquor as a material B, wherein the hemicellulose content of the material B is 10g/L-20 g/L;
step 3) pretreating the material B by using a filter bag and then treating the material B by using a nanofiltration membrane to obtain concentrated solution and filtrate, wherein the filtrate is sodium hydroxide solution and is recycled, the collected concentrated solution is material C, the hemicellulose content of the material C is 50-70 g/L, the aperture of the filter bag is 5-20 mu m, the intercepted molecular weight of the nanofiltration membrane is 300-3000, the temperature for treating the nanofiltration membrane is 40-70 ℃, and the membrane inlet pressure for treating the nanofiltration membrane is 10-30 bar;
step 4), adding acid into the material C to obtain a precipitate which is a material D, wherein the PH value of the material D is 2-7;
step 5) treating the material D by a ceramic membrane to obtain a concentrated solution and a filtrate, adding pure water for dialysis, and collecting the concentrated solution as a material E, wherein the hemicellulose content of the material E is 120-200 g/L, the cut-off molecular weight of the ceramic membrane is 10000-40000, the treatment temperature of the ceramic membrane is 60-90 ℃, the membrane inlet pressure of the ceramic membrane is 3-9 bar, and the water adding amount for dialysis is 2-7 times of the total amount of the material;
and 6) drying the material E to obtain hemicellulose dry powder.
Further, in the step 1), the chemical pulp is prepared by chemically cooking wood, the wood is broadleaf wood, and preferably the wood is one or more of eucalyptus and poplar.
Further, the temperature in the step 1) is 50-70 ℃, the concentration of the sodium hydroxide solution is 8-15%, and the dipping time is 1-3 h.
Further, an automatic slag discharge centrifuge is adopted in the solid-liquid separation treatment in the step 2), and the aperture of filter cloth of the automatic slag discharge centrifuge is 200-700 meshes, preferably 300-500 meshes.
Further, the aperture of the filter bag in the step 3) is 5-15 μm, the cut-off molecular weight of the nanofiltration membrane is 500-2000, the temperature for processing the nanofiltration membrane is 50-70 ℃, and the pressure for processing the nanofiltration membrane is 15-25 bar.
Further, the acid in the step 4) is concentrated sulfuric acid; the PH of the material D is 3-6.
Further, the molecular weight cut-off of the ceramic membrane in the step 5) is 15000-30000, the processing temperature of the ceramic membrane is 65-75 ℃, the membrane feeding pressure of the ceramic membrane is 5-8 bar, and the water adding amount for dialysis by adding water is 3-6 times of the total amount of the materials.
Further, in the step 6), the material E is dried by a spray dryer, and when the spray dryer is used for drying, the air inlet temperature is 240-300 ℃, preferably 260-300 ℃.
Further, in the step 6), the material E is dried by a centrifugal spray dryer, and when the centrifugal spray dryer is used for drying, the air outlet temperature is 80-120 ℃, preferably 95-115 ℃.
Another object of the present invention is a hemicellulose produced by any of the above methods for extracting hemicellulose from chemical pulp.
The invention has the outstanding effects that:
according to the method for extracting hemicellulose from chemical pulp, the chemical pulp is used as a raw material, and only one additional process is needed in the pulping process, so that the process is simple; the chemical pulp after hemicellulose extraction can directly enter downstream without special treatment, so that the generation of solid waste is reduced, alkali liquor in the dipping process can be recycled in a system, and the generation amount of waste liquor in the extraction process is greatly reduced; the chemical pulp can be directly impregnated without other treatments after being subjected to a simple pretreatment process, so that the process flow is simplified, the resource utilization rate is improved, the environmental pollution is reduced, the extraction cost is reduced, and the method has the advantages of high efficiency, low cost, no three wastes, small influence on the environment and the like. Meanwhile, the prepared hemicellulose product has wide application range and certain popularization.
The following detailed description of the embodiments of the present invention is provided in connection with the examples to facilitate understanding and understanding of the technical solutions of the present invention.
Detailed Description
The process of the present invention is illustrated below by means of specific examples, but the present invention is not limited thereto. The experimental methods described in the following examples are all conventional methods unless otherwise specified; the reagents and materials are commercially available, unless otherwise specified.
Example 1
The method for extracting hemicellulose from chemical pulp comprises the following steps:
step 1) dipping chemical pulp in 5 percent sodium hydroxide solution for 0.5h at the temperature of 40 ℃ to obtain a material A; the chemical pulp is prepared by chemically cooking wood, and the wood is eucalyptus;
step 2) performing solid-liquid separation treatment on the material A, wherein an automatic slag discharge centrifuge is adopted in the solid-liquid separation treatment, the aperture of filter cloth of the automatic slag discharge centrifuge is 200 meshes, impregnated chemical pulp and impregnating solution are obtained, the impregnating solution is collected to be a material B, and the hemicellulose content of the material B is 10 g/L;
step 3) pretreating the material B by using a filter bag and then treating the material B by using a nanofiltration membrane to obtain concentrated solution and filtrate, wherein the filtrate is sodium hydroxide solution and is recycled, the collected concentrated solution is material C, the hemicellulose content of the material C is 50g/L, the aperture of the filter bag is 5 mu m, the intercepted molecular weight of the nanofiltration membrane is 300, the temperature for treating the nanofiltration membrane is 40 ℃, and the membrane inlet pressure for treating the nanofiltration membrane is 10 bar;
step 4), adding concentrated sulfuric acid into the material C to obtain a precipitate which is a material D, wherein the PH value of the material D is 2;
step 5) treating the material D by a ceramic membrane to obtain a concentrated solution and a filtrate, adding pure water for dialysis, and collecting the concentrated solution to obtain a material E, wherein the hemicellulose content of the material E is 120g/L, the cut-off molecular weight of the ceramic membrane is 10000, the temperature for ceramic membrane treatment is 60 ℃, the membrane inlet pressure of the ceramic membrane is 3bar, and the water adding amount for water dialysis is 2 times of the total amount of the material;
and 6) drying the material E to obtain hemicellulose dry powder, drying the material E by using a spray dryer, wherein when the spray dryer is used for drying, the air inlet temperature is 240 ℃, and the air outlet temperature is 95 ℃.
The solid content of the finished product is 95.5 percent, and the ash content is 8.5 percent.
Example 2
The method for extracting hemicellulose from chemical pulp comprises the following steps:
step 1) dipping chemical pulp in 8% sodium hydroxide solution for 1h at the temperature of 50 ℃ to obtain a material A; the chemical pulp is prepared by chemically cooking wood, and the wood is poplar;
step 2) performing solid-liquid separation treatment on the material A, wherein an automatic slag discharge centrifuge is adopted in the solid-liquid separation treatment, the aperture of filter cloth of the automatic slag discharge centrifuge is 300 meshes, impregnated chemical pulp and impregnating solution are obtained, the impregnating solution is collected to be a material B, and the hemicellulose content of the material B is 15 g/L;
step 3) pretreating the material B by using a filter bag and then treating the material B by using a nanofiltration membrane to obtain concentrated solution and filtrate, wherein the filtrate is sodium hydroxide solution and is recycled, the collected concentrated solution is material C, the hemicellulose content of the material C is 60g/L, the aperture of the filter bag is 5 mu m, the intercepted molecular weight of the nanofiltration membrane is 500, the temperature for treating the nanofiltration membrane is 50 ℃, and the membrane inlet pressure for treating the nanofiltration membrane is 15 bar;
step 4), adding concentrated sulfuric acid into the material C to obtain a precipitate which is a material D, wherein the pH value of the material D is 3;
step 5) treating the material D by a ceramic membrane to obtain a concentrated solution and a filtrate, adding pure water for dialysis, and collecting the concentrated solution to be a material E, wherein the hemicellulose content of the material E is 140g/L, the cut-off molecular weight of the ceramic membrane is 15000, the temperature for ceramic membrane treatment is 65 ℃, the membrane feeding pressure of the ceramic membrane is 5bar, and the water adding amount for water dialysis is 3 times of the total amount of the material;
and 6) drying the material E to obtain hemicellulose dry powder, drying the material E by using a spray dryer, wherein when the spray dryer is used for drying, the air inlet temperature is 300 ℃, and the air outlet temperature is 120 ℃.
The solid content of the finished product is 96.5 percent, and the ash content is 8.5 percent.
Example 3
The method for extracting hemicellulose from chemical pulp comprises the following steps:
step 1) soaking chemical pulp in 15% sodium hydroxide solution for 3 hours at the temperature of 70 ℃ to obtain a material A; the chemical pulp is prepared by chemically cooking wood, wherein the wood is eucalyptus and poplar;
step 2) performing solid-liquid separation treatment on the material A, wherein an automatic slag discharge centrifuge is adopted in the solid-liquid separation treatment, the aperture of filter cloth of the automatic slag discharge centrifuge is 500 meshes, impregnated chemical pulp and impregnating solution are obtained, the impregnating solution is collected to be a material B, and the hemicellulose content of the material B is 19 g/L;
step 3) pretreating the material B by using a filter bag and then treating the material B by using a nanofiltration membrane to obtain concentrated solution and filtrate, wherein the filtrate is sodium hydroxide solution and is recycled, the collected concentrated solution is material C, the hemicellulose content of the material C is 68g/L, the aperture of the filter bag is 15 mu m, the intercepted molecular weight of the nanofiltration membrane is 2000, the temperature for treating the nanofiltration membrane is 60 ℃, and the membrane inlet pressure for treating the nanofiltration membrane is 25 bar;
step 4), adding concentrated sulfuric acid into the material C to obtain a precipitate which is a material D, wherein the pH value of the material D is 6;
step 5) treating the material D by a ceramic membrane to obtain a concentrated solution and a filtrate, adding pure water for dialysis, and collecting the concentrated solution to obtain a material E, wherein the hemicellulose content of the material E is 170g/L, the cut-off molecular weight of the ceramic membrane is 30000, the temperature for ceramic membrane treatment is 75 ℃, the membrane inlet pressure of the ceramic membrane is 8bar, and the water adding amount for water dialysis is 6 times of the total amount of the material;
and 6) drying the material E to obtain hemicellulose dry powder, drying the material E by using a centrifugal spray dryer, wherein when the centrifugal spray dryer is used for drying, the air inlet temperature is 260 ℃, and the air outlet temperature is 80 ℃.
The solid content of the finished product is 97.5 percent, and the ash content is 4.5 percent.
Example 4
The method for extracting hemicellulose from chemical pulp comprises the following steps:
step 1) soaking chemical pulp in 20% sodium hydroxide solution at 80 ℃ for 4h to obtain a material A; the chemical pulp is prepared by chemically cooking wood, and the wood is eucalyptus;
step 2) performing solid-liquid separation treatment on the material A, wherein an automatic slag discharge centrifuge is adopted in the solid-liquid separation treatment, the aperture of filter cloth of the automatic slag discharge centrifuge is 700 meshes, impregnated chemical pulp and impregnating solution are obtained, the impregnating solution is collected to be a material B, and the hemicellulose content of the material B is 20 g/L;
step 3) pretreating the material B by using a filter bag and then treating the material B by using a nanofiltration membrane to obtain concentrated solution and filtrate, wherein the filtrate is sodium hydroxide solution and is recycled, the collected concentrated solution is material C, the hemicellulose content of the material C is 70g/L, the aperture of the filter bag is 20 mu m, the intercepted molecular weight of the nanofiltration membrane is 3000, the temperature for treating the nanofiltration membrane is 70 ℃, and the membrane inlet pressure for treating the nanofiltration membrane is 30 bar;
step 4), adding concentrated sulfuric acid into the material C to obtain a precipitate which is a material D, wherein the pH value of the material D is 7;
step 5) treating the material D by a ceramic membrane to obtain a concentrated solution and a filtrate, adding pure water for dialysis, and collecting the concentrated solution to be a material E, wherein the hemicellulose content of the material E is 200g/L, the cut-off molecular weight of the ceramic membrane is 40000, the temperature for ceramic membrane treatment is 90 ℃, the membrane feeding pressure of the ceramic membrane is 9bar, and the water adding amount for water dialysis is 7 times of the total amount of the material;
and 6) drying the material E to obtain hemicellulose dry powder, drying the material E by using a centrifugal spray dryer, wherein when the centrifugal spray dryer is used for drying, the air inlet temperature is 300 ℃, and the air outlet temperature is 115 ℃.
The solid content of the finished product is 97 percent, and the ash content is 4.5 percent.
The invention has various embodiments, and all technical solutions formed by adopting equivalent transformation or equivalent transformation are within the protection scope of the invention.
Claims (10)
1. A method for extracting hemicellulose from chemical pulp is characterized by comprising the following steps:
step 1) dipping chemical pulp in 5-20% sodium hydroxide solution for 0.5-4 h at the temperature of 40-80 ℃ to obtain a material A;
step 2) performing solid-liquid separation treatment on the material A to obtain chemical pulp and steeping liquor after steeping, and collecting the steeping liquor as a material B, wherein the hemicellulose content of the material B is 10g/L-20 g/L;
step 3) pretreating the material B by using a filter bag and then treating the material B by using a nanofiltration membrane to obtain concentrated solution and filtrate, wherein the filtrate is sodium hydroxide solution and is recycled, the collected concentrated solution is material C, the hemicellulose content of the material C is 50-70 g/L, the aperture of the filter bag is 5-20 mu m, the intercepted molecular weight of the nanofiltration membrane is 300-3000, the temperature for treating the nanofiltration membrane is 40-70 ℃, and the membrane inlet pressure for treating the nanofiltration membrane is 10-30 bar;
step 4), adding acid into the material C to obtain a precipitate which is a material D, wherein the PH value of the material D is 2-7;
step 5) treating the material D by a ceramic membrane to obtain a concentrated solution and a filtrate, adding pure water for dialysis, and collecting the concentrated solution as a material E, wherein the hemicellulose content of the material E is 120-200 g/L, the cut-off molecular weight of the ceramic membrane is 10000-40000, the treatment temperature of the ceramic membrane is 60-90 ℃, the membrane inlet pressure of the ceramic membrane is 3-9 bar, and the water adding amount for dialysis is 2-7 times of the total amount of the material;
and 6) drying the material E to obtain hemicellulose dry powder.
2. A method of extracting hemicellulose from chemical pulp according to claim 1, characterized in that: in the step 1), the chemical pulp is prepared by chemically cooking wood, the wood is broadleaf wood, and preferably the wood is one or more of eucalyptus and poplar.
3. A method of extracting hemicellulose from chemical pulp according to claim 1, characterized in that: the temperature in the step 1) is 50-70 ℃, the concentration of the sodium hydroxide solution is 8-15%, and the dipping time is 1-3 h.
4. A method of extracting hemicellulose from chemical pulp according to claim 1, characterized in that: in the step 2), the solid-liquid separation treatment adopts an automatic slag discharge centrifuge, and the aperture of filter cloth of the automatic slag discharge centrifuge is 200-700 meshes, preferably 300-500 meshes.
5. A method of extracting hemicellulose from chemical pulp according to claim 1, characterized in that: in the step 3), the aperture of the filter bag is 5-15 μm, the molecular weight cut-off of the nanofiltration membrane is 500-2000, the temperature for processing the nanofiltration membrane is 50-70 ℃, and the pressure for processing the nanofiltration membrane is 15-25 bar.
6. A method of extracting hemicellulose from chemical pulp according to claim 1, characterized in that: the acid in the step 4) is concentrated sulfuric acid; the PH of the material D is 3-6.
7. A method of extracting hemicellulose from chemical pulp according to claim 1, characterized in that: the molecular weight cut-off of the ceramic membrane in the step 5) is 15000-30000, the processing temperature of the ceramic membrane is 65-75 ℃, the membrane feeding pressure of the ceramic membrane is 5-8 bar, and the water adding amount for dialysis by adding water is 3-6 times of the total amount of the materials.
8. A method of extracting hemicellulose from chemical pulp according to claim 1, characterized in that: in the step 6), the material E is dried by a spray dryer, and when the spray dryer is used for drying treatment, the air inlet temperature is 240-300 ℃, preferably 260-300 ℃.
9. A method of extracting hemicellulose from chemical pulp according to claim 1, characterized in that: in the step 6), the material E is dried by adopting a centrifugal spray dryer, and when the centrifugal spray dryer is used for drying treatment, the air outlet temperature is 80-120 ℃, and preferably 95-115 ℃.
10. Hemicellulose obtained by the process for extracting hemicellulose from chemical pulp according to any one of claims 1-9.
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| CN202111438066.5A CN114044836A (en) | 2021-11-30 | 2021-11-30 | Method for extracting hemicellulose from chemical pulp |
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| CN (1) | CN114044836A (en) |
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| CN114736318A (en) * | 2022-02-28 | 2022-07-12 | 上海昶法新材料有限公司 | Method for extracting hemicellulose from chemi-mechanical pulp |
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