A method for comprehensive utilization of waste liquor from chemical mechanical / sulfate pulping

Abstract

The present application belongs to the field of comprehensive utilization of lignocellulosic biomass raw materials, and provides a method for comprehensive utilization of chemical mechanical method / sulfate method pulping waste liquid. First, the lignin-carbohydrate complex (LCC) degradation is obtained by using sulfuric acid acidification pulping black liquor and catalysis, and then the hemicellulose in the black liquor is converted into furfural and acetic acid by using sulfuric acid acidolysis and catalysis. The whole process fully utilizes the different chemical properties of sulfuric acid at different temperatures, realizes the different effects of sulfuric acid on the main components in the pulping black liquor by adjusting the treatment temperature, and extracts or prepares lignin, furfural and acetic acid, realizing the high-value utilization of black liquor.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of comprehensive utilization of lignocellulosic biomass feedstock, and particularly relates to a method for comprehensive utilization of chemical mechanical method / sulfate method pulping waste liquor. BACKGROUND

[0002] The information disclosed in this Background section is for the purpose of generally presenting the context of the application. The information disclosed in this Background section is not to be necessarily taken as an acknowledgement or any form of suggestion that this information forms part of the prior art already known to a person skilled in the art.

[0003] Lignocellulosic biomass feedstock is the most abundant renewable resource in nature. About one hundred million tons of lignocellulosic biomass feedstock is used for pulping and papermaking every year in the world. Lignocellulosic biomass feedstock is mainly composed of cellulose, hemicellulose and lignin. In the pulping and papermaking industry, the cellulose in lignocellulosic biomass feedstock is mainly used for papermaking, while a large amount of hemicellulose and lignin is dissolved into pulping waste liquor in the pulping process.

[0004] Hemicellulose is a heterogeneous polymer composed of several different types of monosaccharides, in which the hemicellulose of hardwood and grasses is mainly polysaccharides, and the hemicellulose of coniferous wood is mainly polysaccharides. Lignin is a biological macromolecule with a three-dimensional network structure formed by the mutual connection of three phenylpropane units through ether bonds and carbon-carbon bonds, which contains rich aromatic ring structures, aliphatic and aromatic hydroxyl groups, and quinone groups. Xylose, galactose, glucose and mannose can be converted into important platform compounds such as furfural and 5-hydroxymethylfurfural through a series of chemical reactions. Lignin is the only renewable resource of aromatic compounds in nature, which can be used to produce high-calorie fuels and aromatic compounds. The traditional treatment method of pulping waste liquor is to recover chemicals and heat energy in the waste liquor by alkali recovery method or to discharge it as waste water after biochemical treatment, which causes serious resource waste.

[0005] Therefore, it is urgent to establish a method for comprehensive utilization of chemical mechanical method / sulfate method pulping waste liquor, which can efficiently extract or prepare lignin, furfural and acetic acid and other products to improve the economic value of pulping waste liquor. SUMMARY

[0006] In order to solve the above problems, the present application provides a method for extracting lignin and preparing furfural and acetic acid by using chemical mechanical method / sulfate method pulping waste liquid as starting material. First, the acid solution is used to acidify the pulping black liquor and catalyze the degradation of lignin-carbohydrate complex (LCC) to obtain high-purity lignin, and then the sulfuric acid is used to acid hydrolysis and catalyze the conversion of hemicellulose in the black liquor into furfural and acetic acid. The whole process makes full use of the different chemical properties of the acid solution at different temperatures, and realizes the different effects of the acid solution on the main components in the pulping black liquor by adjusting the treatment temperature, while extracting or preparing lignin, furfural and acetic acid, and realizing the high-value utilization of black liquor.

[0007] In order to achieve the above purpose, the present application adopts the following technical scheme:

[0008] In a first aspect of the present application, a method for comprehensive utilization of chemical mechanical method / sulfate method pulping waste liquid is provided, comprising:

[0009] Filtering or centrifuging the pulping waste liquid, adding acid to form acidified waste liquid;

[0010] Heating the acidified waste liquid to 100-120 DEG C and keeping warm to make lignin-carbohydrate complex LCC degrade, and then solid-liquid separation to collect the precipitated lignin and clear liquid respectively;

[0011] Placing the clear liquid in a sealed container, heating to evaporate steam containing furfural and acetic acid, condensing and collecting the evaporated liquid;

[0012] Separating furfural and acetic acid from the evaporated liquid;

[0013] The pulping waste liquid is sulfate method pulping black liquor or chemical mechanical method pulping waste liquid.

[0014] Among them, for sulfate method pulping black liquor, lignin is extracted from sulfate method pulping black liquor relying on alkali recovery system, and furfural and acetic acid are produced by using various organic matters in waste liquid.

[0015] In some embodiments, the pH value of the acidified waste liquid is 1-4.

[0016] In some embodiments, the holding time is 10-50 min (chemical mechanical method pulping waste liquid) or 0.5-2 h (sulfate method pulping black liquor).

[0017] In some embodiments, the temperature in the sealed container is heated to 150-220 DEG C, and the holding time is 0-20 min.

[0018] In some embodiments, the outgassing rate of the sealed container is 2-10% of the waste liquid volume / min.

[0019] In some embodiments, the furaldehyde-containing liquid is distilled to a volume of 0.5-1.5 times the initial volume of the liquid in the high-pressure reactor, and the gas release, water injection and heating are stopped.

[0020] In the present application, the method for purifying and separating furaldehyde and acetic acid from the reaction distillate is not particularly limited, and those skilled in the art can select from the existing methods according to the actual situation.

[0021] In some embodiments, the acid solution used for acidification is at least one of sulfuric acid, hydrochloric acid and phosphoric acid.

[0022] In some embodiments, when the pulp waste liquid is a kraft pulp black liquor, the remaining liquid in the sealed container is introduced into the kraft pulp black liquor alkali recovery system.

[0023] When the pulp waste liquid is a chemi-mechanical pulp waste liquid, the remaining liquid in the sealed container is concentrated and desalted to adjust the pH of the pulp waste liquid.

[0024] In a second aspect of the present application, furaldehyde and acetic acid prepared by the above method are provided.

[0025] In a third aspect of the present application, the use of chemical pulp black liquor and chemi-mechanical pulp waste liquid in the preparation of furaldehyde and acetic acid is provided.

[0026] Advantages of the present application

[0027] (1) For kraft pulp black liquor, the present application first acidifies the kraft pulp black liquor with sulfuric acid and catalyzes the degradation of lignin-carbohydrate complex (LCC) to obtain high-purity lignin, then acid hydrolyzes and catalyzes the conversion of hemicellulose in the black liquor into furaldehyde and acetic acid, and finally relies on the traditional kraft pulp black liquor alkali recovery system to prepare and recover sodium sulfide. The entire process fully utilizes the different chemical properties of sulfuric acid at different temperatures, achieves different effects of sulfuric acid on the main components in the pulp black liquor by adjusting the treatment temperature, and relies on the pulp black liquor alkali recovery system to achieve the utilization of the reaction residues. Not only does it achieve high-value utilization of black liquor, but the entire process is environmentally friendly and has low production cost.

[0028] (2) For chemi-mechanical pulp waste liquid, the present application acidifies the pulp waste liquid with acid solution, promotes the acid precipitation of lignin in the waste liquid, and at the same time acts as a catalyst to catalyze the hydrolysis of polysaccharides in the waste liquid into monosaccharides and acetic acid, and further catalyze the conversion of five-carbon sugars into furaldehyde, thereby reducing the amount of chemical reagents used and significantly reducing production cost. The present application treats the lignin suspension at a relatively low temperature to destroy the lignin-carbohydrate complex (LCC), thereby improving the purity of the extracted lignin. The remaining liquid after the reaction in the present application can be reused to adjust the pH of the pulp waste liquid, thereby achieving cyclic utilization.

[0029] (3) The preparation method is simple, practical and easy to popularize. DETAILED DESCRIPTION

[0030] It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the application. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

[0031] The application will be further described in conjunction with specific examples. It should be noted that the specific examples are illustrative of the application and are not limiting.

[0032] In the following examples, the mass fraction of concentrated sulfuric acid is 72%.

[0033] The calculation method of the lignin extraction rate and the acetic acid yield of the pulping waste liquid is as follows:

[0034] (1) The calculation method of the lignin extraction rate is as follows:

[0035] Since the lignin precipitation amount in the waste liquid is affected by the lignin concentration and pH in the waste liquid, the lignin mass m1 precipitated at pH = 1 of the waste liquid is selected as the reference.

[0036] Lignin extraction rate % = m / m1*100

[0037] Wherein, m is the lignin precipitation mass.

[0038] (2) The calculation method of the acetic acid yield is as follows:

[0039] ① Determination of total sugar content in pulping waste liquid: Take a certain amount of pulping waste liquid, adjust the pH of the waste liquid to 7 using dilute sulfuric acid, filter, and take 1 mL of the filtrate in a pressure bottle. Add 70 uL of sulfuric acid with a mass fraction of 72% and 0.93 mL of deionized water to the pressure bottle to make the concentration of sulfuric acid in the waste liquid 4%. Place the pressure bottle in a 121℃ oil bath for 60 min. Determine the concentration of pentose in the waste liquid using ion chromatography. Finally, the pentose concentration in the cooked waste liquid after acid hydrolysis is converted to C1(g / L).

[0040] Total sugar content m 总糖 (g) in pulping waste liquid = C1*V1, wherein V1(L) is the volume of the pulping waste liquid.

[0041] ② Determine the acetic acid concentration C 乙酸 (g / L) in the steam-out liquid using liquid chromatography.

[0042] Acetic acid production m 乙酸 (g) = V2*C 乙酸， Wherein, V2 is the volume of the steam-out liquid

[0043] Yield of acetic acid from pulping waste liquor 乙酸 (%) = m 乙酸 / m 总糖 * 100.

[0044] Example 1

[0045] 500 mL of filtered eucalyptus chemical mechanical pulping waste liquor was poured into a pressure bottle, and concentrated sulfuric acid was used to adjust the pH of the waste liquor to 2. The acidified waste liquor was heated to 120°C and maintained for 10 min. The precipitated lignin in the waste liquor was then separated by centrifugation at 4000 rpm. The acidified and centrifuged chemical mechanical pulp waste liquor was placed in a high-pressure reaction kettle, and the heating rate of the reaction kettle was adjusted so that the reaction kettle was heated to 180°C in 30 min. After 5 min of maintaining the temperature, the exhaust valve of the reaction kettle was opened and adjusted, and the steam rich in furfural and acetic acid was directly introduced into the condenser tube and collected in a glass tube. The exhaust valve was adjusted to a condensate collection rate of 20 mL / min. At the same time that the exhaust valve of the reaction kettle was opened, the high-pressure water inlet switch was opened, and the water inlet rate of the reaction kettle was equal to the condensate collection rate. When the volume of the condensate was 500 mL, the exhaust valve of the reaction kettle and the high-pressure water inlet were closed, and the heating was stopped. The reaction distillate was purified and separated to obtain furfural and acetic acid.

[0046] The yield of lignin extraction and preparation of furfural and acetic acid from pulping waste liquor was significantly affected by the lignin content and total sugar content in the waste liquor. The final yield of lignin was 93%, and the purity was 92%. The yield of furfural was 76%, and the yield of acetic acid was 21%.

[0047] Example 2

[0048] 500 mL of eucalyptus chemical mechanical pulp waste liquor was poured into a pressure bottle, and concentrated sulfuric acid was used to adjust the pH of the waste liquor to 2.5. The acidified waste liquor was heated to 110°C and maintained for 20 min. The precipitated lignin in the waste liquor was then separated by filtration. The filtered chemical mechanical pulp waste liquor was placed in a high-pressure reaction kettle, and the heating rate of the reaction kettle was adjusted so that the reaction kettle was heated to 170°C in 30 min. After 10 min of maintaining the temperature, the exhaust valve of the reaction kettle was opened and adjusted, and the steam rich in furfural and acetic acid was directly introduced into the condenser tube and collected in a glass tube. The exhaust valve was adjusted to a condensate collection rate of 25 mL / min. At the same time that the exhaust valve of the reaction kettle was opened, the high-pressure water inlet switch was opened, and the water inlet rate of the reaction kettle was equal to the condensate collection rate. When the volume of the condensate was 750 mL, the exhaust valve of the reaction kettle and the high-pressure water inlet were closed, and the heating was stopped. The reaction distillate was purified and separated to obtain furfural and acetic acid.

[0049] The yield of lignin extraction and preparation of furfural and acetic acid from pulping waste liquor was significantly affected by the lignin content and total sugar content in the waste liquor. The final yield of lignin was 88%, and the purity was 90%. The yield of furfural was 73%, and the yield of acetic acid was 21%.

[0050] Example 3

[0051] 500 mL of the filtered wheat straw chemi-mechanical pulp spent liquor was poured into a pressure vessel, the pH of the spent liquor was adjusted to 2 using reaction spent liquor, the acidified spent liquor was heated to 100°C and kept for 30 min. The acid-precipitated lignin was obtained by filtering the acidified spent liquor; the filtered chemi-mechanical pulp spent liquor was placed in a high-pressure reaction vessel, the heating rate of the reaction vessel was adjusted so that the reaction vessel was heated to 185°C in 30 min; when the temperature of the reaction vessel was increased to 185°C, the exhaust valve of the reaction vessel was immediately opened and adjusted, the steam rich in furfural and acetic acid was directly introduced into the condenser tube and collected in a glass tube, the exhaust valve was adjusted so that the collection rate of the condensate was 20 mL / min; the high-pressure water inlet switch was opened at the same time as the exhaust valve of the reaction vessel was opened, so that the water inlet rate of the reaction vessel was equal to the condensate collection rate. When the volume of the condensate was 500 mL, the exhaust valve of the reaction vessel and the high-pressure water inlet were closed, and the heating was stopped. The reaction distillate was purified and separated to obtain furfural and acetic acid.

[0052] The yield of lignin extraction and preparation of furfural and acetic acid from pulp spent liquor is obviously affected by the lignin content and total sugar content in the spent liquor. The final yield of lignin is 93%, the purity is 90%, the yield of furfural is 76%, and the yield of acetic acid is 23%.

[0053] Example 4

[0054] 1000 mL of the filtered poplar kraft pulp black liquor was poured into a beaker, the pH of the black liquor was adjusted to 2 using concentrated sulfuric acid, the acidified black liquor was heated to 120°C and kept for 0.5 h, and then the black liquor was filtered to obtain acid-precipitated lignin; the delignified black liquor was placed in a high-pressure reaction vessel, the heating rate of the reaction vessel was adjusted so that the reaction vessel was heated to 185°C in 40 min; after keeping for 5 min, the exhaust valve of the reaction vessel was opened and adjusted, the steam rich in furfural and acetic acid was directly introduced into the condenser tube and collected in a glass tube, the exhaust valve was adjusted so that the collection rate of the condensate was 50 mL / min; the high-pressure water inlet switch was opened at the same time as the exhaust valve of the reaction vessel was opened, so that the water inlet rate of the reaction vessel was equal to the condensate collection rate. When the volume of the condensate was 1200 mL, the exhaust valve of the reaction vessel and the high-pressure water inlet were closed, and the heating was stopped. The reaction distillate was purified and separated to obtain furfural and acetic acid. Finally, the reaction residue rich in sodium sulfate and sulfuric acid was introduced into the pulp black liquor alkali recovery system to realize the recycling of the reaction residue.

[0055] The yield of lignin extraction and preparation of furfural and acetic acid from pulp spent liquor is obviously affected by the lignin content and total sugar content in the spent liquor. The final yield of lignin is 93%, the purity is 92%, the yield of furfural is 75%, and the yield of acetic acid is 20%.

[0056] Example 5

[0057] A 1000 mL of Eucalyptus Kraft Pulping spent liquor was poured into a beaker, 72% sulfuric acid was used to adjust the pH of the spent liquor to 2.5, the acidified spent liquor was heated to 100°C and kept for 1.5 h, and the acid-precipitated lignin in the spent liquor was separated by centrifugation; the delignified acidified spent liquor was placed in a high-pressure reaction kettle, the heating rate of the reaction kettle was adjusted so that the reaction kettle was heated to 180°C in 30 min; when the temperature of the reaction kettle was raised to 180°C and kept for 10 min, the exhaust valve of the reaction kettle was opened, and the steam rich in furfural and acetic acid was directly introduced into the condenser tube and collected in a glass tube, the exhaust valve was adjusted so that the condensate collection rate was 50 mL / min; the high-pressure water inlet switch was opened at the same time as the exhaust valve of the reaction kettle was opened, so that the water inlet rate of the reaction kettle was equal to the condensate collection rate. When the volume of the condensate was 1500 mL, the exhaust valve of the reaction kettle and the high-pressure water inlet were closed, and the heating was stopped. The reaction distillate was purified and separated to obtain furfural and acetic acid. Finally, the reaction residue rich in sodium sulfate and sulfuric acid was introduced into the pulping spent liquor alkali recovery system to realize the recycling of the reaction residue.

[0058] The yield of lignin extraction and preparation of furfural and acetic acid from pulping waste liquor is obviously affected by the lignin content and total sugar content in the waste liquor. The final yield of lignin is 88%, the purity is 90%, the yield of furfural is 70%, and the yield of acetic acid is 21%.

[0059] Example 6

[0060] A 1000 mL of Eucalyptus Kraft Pulping spent liquor was poured into a beaker, 72% sulfuric acid was used to adjust the pH of the spent liquor to 2.5, the acidified spent liquor was heated to 100°C and kept for 1.5 h, and the acid-precipitated lignin in the spent liquor was separated by centrifugation; the delignified acidified spent liquor was placed in a high-pressure reaction kettle, the heating rate of the reaction kettle was adjusted so that the reaction kettle was heated to 180°C in 30 min; when the temperature of the reaction kettle was raised to 180°C and kept for 10 min, the exhaust valve of the reaction kettle was opened, and the steam rich in furfural and acetic acid was directly introduced into the condenser tube and collected in a glass tube, the exhaust valve was adjusted so that the condensate collection rate was 50 mL / min; the high-pressure water inlet switch was opened at the same time as the exhaust valve of the reaction kettle was opened, so that the water inlet rate of the reaction kettle was equal to the condensate collection rate. When the volume of the condensate was 1500 mL, the exhaust valve of the reaction kettle and the high-pressure water inlet were closed, and the heating was stopped. The reaction distillate was purified and separated to obtain furfural and acetic acid. Finally, the reaction residue rich in sodium sulfate and sulfuric acid was introduced into the pulping spent liquor alkali recovery system to realize the recycling of the reaction residue.

[0061] The yield of lignin extraction and preparation of furfural and acetic acid from pulping waste liquor is obviously affected by the lignin content and total sugar content in the waste liquor. The final yield of lignin is 88%, the purity is 90%, the yield of furfural is 70%, and the yield of acetic acid is 21%.

[0062] The above merely provides the preferred embodiments of the present application, and is not used to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modifications, equivalent replacements, improvements, etc. made within the principles and technical scope of the present application shall fall into the scope of the present application.

Claims

1. A method for comprehensive utilization of pulping waste liquor, characterized by, The method is: 500 mL of filtered eucalyptus chemical mechanical pulping waste liquid is poured into a pressure-resistant bottle, the pH of the waste liquid is adjusted to 2 using 72% sulfuric acid, the acidified waste liquid is heated to 120℃ and kept for 10 min; the lignin precipitated in the waste liquid is separated by centrifugation at 4000 rpm; The acidified and centrifuged chemical mechanical pulping waste liquid is placed in a high-pressure reaction kettle, the heating rate of the reaction kettle is adjusted so that the reaction kettle is heated to 180℃ for 30 min; after keeping for 5 min, the exhaust valve of the reaction kettle is opened and adjusted, the steam rich in furfural and acetic acid is directly introduced into the condenser tube and collected in the glass tube, the exhaust valve is adjusted to make the condensate collection rate 20 mL / min; the high-pressure water inlet switch is opened at the same time as the exhaust valve of the reaction kettle is opened, so that the water inlet rate of the reaction kettle is equal to the condensate collection rate; when the volume of the condensate is 500 mL, the exhaust valve of the reaction kettle and the high-pressure water inlet are closed, and the heating is stopped; The reaction distillate is purified and separated to obtain furfural and acetic acid; The yield of the lignin is 93%, the purity is 92%, the yield of furfural is 76%, and the yield of acetic acid is 21%.

2. A method for comprehensive utilization of pulping waste liquor, characterized by, The method is: 500 mL of filtered eucalyptus chemical mechanical pulping waste liquid is poured into a pressure-resistant bottle, the pH of the waste liquid is adjusted to 2 using 72% sulfuric acid, the acidified waste liquid is heated to 120℃ and kept for 10 min; the lignin precipitated in the waste liquid is separated by centrifugation at 4000 rpm; The acidified and centrifuged chemical mechanical pulping waste liquid is placed in a high-pressure reaction kettle, the heating rate of the reaction kettle is adjusted so that the reaction kettle is heated to 180℃ for 30 min; after keeping for 5 min, the exhaust valve of the reaction kettle is opened and adjusted, the steam rich in furfural and acetic acid is directly introduced into the condenser tube and collected in the glass tube, the exhaust valve is adjusted to make the condensate collection rate 20 mL / min; the high-pressure water inlet switch is opened at the same time as the exhaust valve of the reaction kettle is opened, so that the water inlet rate of the reaction kettle is equal to the condensate collection rate; when the volume of the condensate is 500 mL, the exhaust valve of the reaction kettle and the high-pressure water inlet are closed, and the heating is stopped; The reaction distillate is purified and separated to obtain furfural and acetic acid; The yield of the lignin is 93%, the purity is 92%, the yield of furfural is 76%, and the yield of acetic acid is 21%.

3. A method for comprehensive utilization of pulping waste liquor, characterized by, The method is: 1000 mL of filtered poplar kraft pulping black liquor is poured into a beaker, the pH of the black liquor is adjusted to 2 using concentrated sulfuric acid, the acidified black liquor is heated to 120℃ and kept for 0.5 h, and then the black liquor is filtered to obtain the acid-precipitated lignin; The delignified kraft pulping black liquor is placed in a high-pressure reaction kettle, the heating rate of the reaction kettle is adjusted so that the reaction kettle is heated to 185℃ for 40 min; after keeping for 5 min, the exhaust valve of the reaction kettle is opened and adjusted, the steam rich in furfural and acetic acid is directly introduced into the condenser tube and collected in the glass tube, the exhaust valve is adjusted to make the condensate collection rate 50 mL / min; the high-pressure water inlet switch is opened at the same time as the exhaust valve of the reaction kettle is opened, so that the water inlet rate of the reaction kettle is equal to the condensate collection rate; when the volume of the condensate is 1200 mL, the exhaust valve of the reaction kettle and the high-pressure water inlet are closed, and the heating is stopped; The purified separation reaction distillate is distilled to obtain furfural and acetic acid; The yield of the lignin is 93% and the purity is 92%, the yield of furfural is 75%, and the yield of acetic acid is 20%.

4. The method for comprehensive utilization of pulping waste liquor according to claim 1 or 2, characterized in that, The pulping waste liquid is a chemical mechanical pulping waste liquid, and the remaining liquid in the high-pressure reaction kettle is concentrated and desalted to adjust the pH of the pulping waste liquid.

5. The method for comprehensive utilization of pulping waste liquor according to claim 3, characterized in that, The pulping waste liquid is a kraft pulping black liquor, and the remaining liquid in the high-pressure reaction kettle is introduced into a kraft pulping black liquor alkali recovery system.

6. Use of the method according to any one of claims 1-3 in the preparation of furfural and acetic acid.