Method for recovering lignin and cellulose by utilizing forestry waste pine powder

Abstract

The invention discloses a method for separating lignin from pine wood by using an organic solvent, solid alkali and oxygen-containing gas, which comprises the following steps: 1, mixing forestry waste pine wood powder serving as a raw material with an acidic aqueous solution, and heating to react to obtain a reaction solution; cooling and filtering to obtain filtrate A containing xylan and xylose and slurry A containing lignin and cellulose; 2, putting the slurry A into a reaction kettle, adding a catalyst alkali metal oxide and a solvent gamma-valerolactone, introducing oxygen-containing gas, sealing, pressurizing, heating and reacting; and 3, filtering the reaction product obtained in the step 2 to obtain cellulose-containing slurry B and filtrate B, and carrying out acid precipitation on the filtrate B to obtain gamma-valerolactone-lignin precipitate. The production process is simple, the separation effect is good, hemicellulose, cellulose and lignin can be efficiently extracted, the practicability is high, and the downstream conversion problem of forestry waste pine wood can be solved, so that the biomass utilization efficiency of the forestry waste pine wood is improved.

Description

Technical Field

[0001] The invention belongs to the field of biochemistry, and in particular relates to a method for recovering lignin and cellulose by utilizing pine wood powder which is a forestry waste. Background Art

[0002] Pine is a common tree species in my country and its status in my country's forestry resources is second only to poplar and fast-growing fir. Pine has the characteristics of short growth cycle and high fiber content. Its rational development and application may be able to cope with the increasingly scarce wood resources. However, there are still few research and development on the preparation and subsequent utilization of pine pulp in my country. The main research focuses on bamboo, pine, etc., and the separation of the three elements of bamboo, pine and other woods is difficult, and the waste utilization rate is low. Usually, combustion treatment is required. This treatment method not only increases the environmental burden, but also causes waste of biomass resources. Therefore, the research and development of efficient pine pulping can effectively solve the problems of low utilization rate of wood resources, low conversion rate, low economic benefits and serious environmental pollution, which is "three lows and one heavy", and play a positive role in the papermaking industry and ecological sustainable development.

[0003] Pine sawdust is a forestry waste rich in cellulose, xylan and lignin, in which the contents of cellulose, xylan and lignin are about 50%, 20% and 25% respectively. The deep processing of pine wood by biorefining method can produce high value-added sugar products, bioenergy and chemicals, which can not only improve the utilization efficiency of biomass but also create economic value. Lignin, as a common biological macromolecule, has good development prospects. It can be degraded into aromatic products and small molecular acids, while hemicellulose can be degraded into xylans, and cellulose can be catalyzed into a variety of platform compounds. However, the lignin, cellulose and hemicellulose of plants are closely combined, breaking the connection between the three elements. Therefore, how to reasonably separate and utilize the three elements of pine wood through reasonable biorefining methods is an urgent problem to be solved at present. Summary of the invention

[0004] In view of the above background, the present invention proposes a method for recovering lignin and cellulose by using pine wood powder, which is a forestry waste. The method can efficiently separate xylan and xylose, lignin and cellulose.

[0005] The method of the present invention comprises the following steps:

[0006] The first step is to use forestry waste pine wood powder as raw material, mix the raw pine wood powder with an acidic aqueous solution, heat to react, cool down and filter to obtain a filtrate A containing xylan and xylose and a slurry A containing lignin and cellulose;

[0007] The second step is to put the slurry A into a reactor, add the catalyst alkali metal oxide, the solvent γ-valerolactone and introduce the oxygen-containing gas, seal and pressurize and heat to react, and filter the reaction product to obtain the cellulose-containing slurry B and the filtrate B;

[0008] In the third step, γ-valerolactone-lignin precipitate is obtained from the filtrate B by acid precipitation.

[0009] Preferably, in the first step, the acidic aqueous solution is a sulfuric acid aqueous solution, the sulfuric acid concentration in the sulfuric acid aqueous solution is 0.5-2% (w / v), the heating reaction temperature is 110-130° C., and the heating reaction time is 0.5-2 h.

[0010] Preferably, in the second step, the reaction temperature is 110-170° C., the reaction time is 60-240 min, the gas is pure oxygen, the reaction pressure is 0.5-2.5 MPa, and the stirring speed is 100-1000 r / min.

[0011] Preferably, in the second step, the concentration of γ-valerolactone is 20%-100% (w / v), the alkali metal oxide is magnesium oxide, and the concentration of the alkali metal oxide is 3%-20% (w / v).

[0012] Preferably, in the third step, hydrochloric acid with a pH of 1-3 is added to precipitate lignin, i.e., γ-valerolactone-lignin precipitation.

[0013] Preferably, in the second step, the reaction temperature is 150° C., the reaction time is 60 min, the gas is pure oxygen, the magnesium oxide content is 15% (w / w) and the reaction pressure is 2 MPa.

[0014] The separation method of the present invention has at least the following beneficial effects:

[0015] 1) The separation method of the present invention can efficiently separate xylan and xylose, lignin and cellulose, and the method is simple and highly operable. The whole process also realizes the economic value of efficient reuse of forestry waste, solves the problem of bamboo powder utilization of agricultural and forestry waste, and the whole production process is relatively clean and environmentally friendly, and is easy to industrialize.

[0016] 2) The present invention uses forestry waste pine wood powder as raw material. The raw material pine wood powder is rich in cellulose, hemicellulose and lignin. It is treated under the catalytic conditions of a relatively low concentration of an acidic aqueous solution to achieve hemicellulose degradation to convert it into xylan and xylose. Xylan and xylose can be dissolved in the acidic aqueous solution. Therefore, a filtrate A rich in xylan and xylose can be obtained by separating the products, which can be used for subsequent xylan product conversion.

[0017] 3) The pulp A obtained in the first step is subjected to a heating and pressurizing reaction treatment by a GVL-CAOSA (catalyst magnesium oxide, solvent γ-valerolactone) system. The product is filtered and separated to obtain a filtrate B rich in lignin and a pulp B. The filtrate B can be precipitated by adding dilute hydrochloric acid to obtain a GVL-lignin precipitate, and the pulp B can be used to obtain a cellulose-rich pulp by removing the water therein. The introduction of GVL as a solvent can significantly improve the separation efficiency of lignin and cellulose compared to the water used as a solvent in the traditional method.

[0018] 4) The catalyst concentration used in the first step is low, the reaction time is short, and the reaction temperature is low, which has good practical utilization value; the magnesium oxide used in the second step is not highly alkaline and can be removed by further acid washing without causing significant pollution to the environment, and GVL can be recovered by a simple rotary evaporation method after the reaction. DETAILED DESCRIPTION

[0019] In combination with the implementation examples, the method for recovering lignin and cellulose from pine wood powder, a forestry waste, proposed by the present invention is further described. Unless otherwise specified, the reagents and instruments used in the following examples are commercially available products.

[0020] The specific implementation cases are as follows:

[0021] The first step is to use forestry waste pine wood powder as raw material, mix the raw pine wood powder with an acidic aqueous solution, heat to react, cool down and filter to obtain a filtrate A containing xylan and xylose and a slurry A containing lignin and cellulose;

[0022] The second step is to put the slurry A into a reactor, add the catalyst alkali metal oxide, the solvent γ-valerolactone and introduce the oxygen-containing gas, seal and pressurize and heat to react, and filter the reaction product to obtain the cellulose-containing slurry B and the filtrate B;

[0023] In the third step, γ-valerolactone-lignin precipitate is obtained from the filtrate B by acid precipitation.

[0024] The method of the present invention will be described in detail below with reference to a number of embodiments.

[0025] Example 1

[0026] This embodiment provides a method for recovering lignin and cellulose using pine wood powder from forestry waste, comprising:

[0027] Step 1: Take 1g of 99% sulfuric acid in a 200ml beaker, add 100ml of deionized water, and stir for 30min to obtain H 2 SO 4 Aqueous solution, concentration 1% (w / v).

[0028] Mix 5g of pine wood powder with the prepared H2 SO 4 The aqueous solution is mixed with a solid-liquid ratio of 1:10; then it is loaded into a reactor, heated to 120°C for reaction for 60 minutes, with a stirring speed of 500r / min. After the reaction is completed, the filtrate A containing xylan and xylose and the slurry A containing lignin and cellulose are separated by a vacuum filtration device.

[0029] Liquid phase mass spectrometry (HPLC, Agilent) was used to conduct qualitative and quantitative analysis on pulp A. The results showed that the separation rate of hemicellulose from pine wood powder was greater than 90%.

[0030] In the second step, the slurry A containing lignin and cellulose is added to the reactor, and the solvent γ-valerolactone (GVL) (80% w / v) and the catalyst MgO (15% w / v) are added, and then O is introduced. 2 , under the conditions of pressure of 2MPa and temperature of 160℃, the reaction time is 3h. After the reaction is completed, the slurry A is subjected to reaction treatment. The treated product is filtered to obtain slurry B and filtrate B. The filtrate B is rich in lignin, and the slurry B is rich in cellulose.

[0031] In the third step, the filtrate B is acid-precipitated with dilute hydrochloric acid (pH=2) to obtain a powder of GVL-lignin precipitation, and the slurry B is dried to obtain cellulose.

[0032] Liquid chromatography-mass spectrometry (HPLC, Agilent) was used to qualitatively and quantitatively analyze the dried pulp B: the lignin removal rate in the pine wood powder was 93.76%, and the cellulose retention rate was 72.84%.

[0033] Example 2

[0034] This embodiment provides a method for recovering lignin and cellulose using pine wood powder from forestry waste, comprising:

[0035] Step 1: Take 1g of 99% sulfuric acid in a 200ml beaker, add 100ml of deionized water, and stir for 30min to obtain H 2 SO 4 5g of pinewood powder was mixed with the prepared H 2 SO 4 The aqueous solution was mixed with a solid-liquid ratio of 1:10; then loaded into a reactor, heated to 120°C for 60 minutes, and stirred at a speed of 500 r / min. After the reaction was completed, the filtrate A containing xylan and xylose and the slurry A containing lignin and cellulose were separated by a vacuum filtration device. The slurry A was qualitatively and quantitatively analyzed by liquid chromatography-mass spectrometry (HPLC, Agilent). The result was that the separation rate of hemicellulose from pine wood powder was greater than 90%.

[0036] In the second step, the slurry A containing lignin and cellulose was added to the reactor, and solvent water (80% w / v) and catalyst MgO (15% w / v) were added, and then pure O 2 , under the conditions of pressure of 2MPa and temperature of 160°C, the reaction time is 3h. After the reaction is completed, the slurry A is subjected to reaction treatment. The treated product is filtered to obtain slurry B and filtrate B, filtrate B is rich in lignin, and slurry B is rich in cellulose. Filtrate B is acidified by dilute hydrochloric acid (pH=2) to obtain GVL-lignin precipitated powder, and cellulose is obtained by drying slurry B.

[0037] The dried pulp B was qualitatively and quantitatively analyzed by liquid chromatography-mass spectrometry (HPLC, Agilent): the lignin removal rate in the pine wood powder was 75.58%, and the cellulose retention rate was 72.98%.

[0038] Example 3

[0039] The method of Example 1 was used with reference to the method of Example 1, except that the reaction temperature in the second step was 140° C. The results were as follows: the lignin removal rate was 81.79% and the cellulose retention rate was 84.91%.

[0040] Example 4

[0041] The method of Example 1 was used with reference to the method of Example 1, except that the reaction temperature in the second step was 150° C. The results were as follows: the lignin removal rate was 87.66% and the cellulose retention rate was 84.68%.

[0042] Example 5

[0043] The method of Example 4 was used with reference to the method of Example 4, except that the reaction time in the second step was 1 hour. The results were as follows: the lignin removal rate was 88.23%, and the cellulose retention rate was 84.01%.

[0044] Example 6

[0045] The method of Example 4 was used with reference to the method of Example 4, except that the reaction time in the second step was 2 hours. The results were as follows: the lignin removal rate was 91.01%, and the cellulose retention rate was 80.76%.

[0046] Example 7

[0047] The method of Example 5 was referred to, except that the MgO content was adjusted to 9% in the second step. The results were: lignin removal rate was 49.36%, and cellulose retention rate was 69.81%.

[0048] Example 8

[0049] The method of Example 5 was referred to, except that the MgO content was adjusted to 12% in the second step. The results were: lignin removal rate was 55.90%, and cellulose retention rate was 71.34%.

[0050] Example 9

[0051] The method of Example 5 was referred to, except that the MgO content was adjusted to 18% in the second step. The results were: lignin removal rate was 78.26%, and cellulose retention rate was 74.15%.

[0052] Example 10

[0053] Referring to the method of Example 5, the difference is only in the second step: wherein O 2 The pressure was adjusted to 0.5 MPa. The results were: lignin removal rate was 55.09% and cellulose retention rate was 46.44%.

[0054] Embodiment 11

[0055] Referring to the method of Example 5, the difference is only in the second step: wherein O 2 The pressure was adjusted to 1 MPa. The results were: lignin removal rate 56.11%, cellulose retention rate 58.25%.

[0056] Example 12

[0057] Referring to the method of Example 5, the difference is only in the second step: wherein O 2 The pressure was adjusted to 1.5 MPa. The results were: lignin removal rate was 72.67% and cellulose retention rate was 66.02%.

[0058] Embodiment 13

[0059] Referring to the method of Example 5, the difference is only in the second step: wherein O 2 The pressure was adjusted to 2.5 MPa. The results were: lignin removal rate was 80.17% and cellulose retention rate was 82.93%.

[0060] Table 1 shows the reaction conditions of step 2 in different embodiments, as well as the lignin removal rate and cellulose retention rate

[0061]

[0062] According to the results of the above specific embodiments, it is shown that by using GVL as the solvent of step 2, and combining magnesium oxide catalyst and oxygen-containing gas as reaction gas, a better lignin removal rate and cellulose retention rate can be obtained. Compared with Example 2, by comparing Example 1 with Example 2, the introduction of GVL as a solvent can significantly improve the separation efficiency of lignin and cellulose compared with water used as a solvent in the traditional method. In addition, by comparing different embodiments, such as Example 5, the conditions of the second step, namely the reaction temperature of 150°C, the reaction time of 60min, the magnesium oxide content of 15% (w / w) and the oxygen pressure of 2Mpa, obtained a relatively high lignin removal rate and cellulose retention rate, and achieved effective separation of hemicellulose, lignin and cellulose.

[0063] In summary, the present invention provides a green and environmentally friendly reaction system for separating three elements in pine wood.

[0064] 1) The separation method of the present invention can efficiently separate xylan and xylose, lignin and cellulose, and the method is simple and highly operable. The whole process also realizes the economic value of efficient reuse of forestry waste, solves the problem of bamboo powder utilization of agricultural and forestry waste, and the whole production process is relatively clean and environmentally friendly, and is easy to industrialize.

[0065] 2) The present invention uses forestry waste pine wood powder as raw material. The raw material pine wood powder is rich in cellulose, hemicellulose and lignin. The hemicellulose is degraded into xylan and xylose by reacting under low concentration sulfuric acid catalysis conditions. Xylan and xylose can be dissolved in an acidic aqueous solution. Therefore, a filtrate A rich in xylan and xylose can be obtained by separating the products, which can be used for subsequent xylan product conversion.

[0066] 3) The pulp A obtained in the first step is subjected to a heating and pressurizing reaction treatment with GVL-CAOSA (catalyst magnesium oxide, solvent γ-valerolactone). The product is separated by suction filtration to obtain a filtrate B rich in lignin and a pulp B. The filtrate B can be precipitated by adding dilute hydrochloric acid to obtain a GVL-lignin precipitate, and the pulp B can be used to obtain a cellulose-rich pulp by removing part of the water therein.

[0067] 4) The catalyst concentration used in the first step is low, the reaction time is short, and the reaction temperature is low, which has good practical utilization value; the magnesium oxide used in the second step is not highly alkaline and can be removed by further acid washing without causing significant pollution to the environment, and GVL can be recovered by a simple rotary evaporation method after the reaction.

[0068] The specific embodiments of the present invention are only for the purpose of illustrative description, and the catalytic system is applicable to the three-element separation of lignocellulosic biomass. It does not limit the protection scope of the present invention in any way, and those skilled in the art can make improvements or changes based on the above description, and all these improvements and changes should belong to the protection scope of the claims attached to the present invention.

Claims

1. A method for recovering lignin and cellulose using pine wood powder from forestry waste, characterized in that The steps include: The first step is to use forestry waste pine wood powder as raw material, mix the raw pine wood powder with an acidic aqueous solution, heat to react, cool down and filter to obtain a filtrate A containing xylan and xylose and a slurry A containing lignin and cellulose; The second step is to put the slurry A into a reactor, add the catalyst alkali metal oxide, the solvent γ-valerolactone and introduce the oxygen-containing gas, seal and pressurize and heat to react, and filter the reaction product to obtain the cellulose-containing slurry B and the filtrate B; In the third step, γ-valerolactone-lignin precipitate is obtained from the filtrate B by acid precipitation.

2. A method for recovering lignin and cellulose using pine wood powder from forestry waste as claimed in claim 1, characterized in that: In the first step, the acidic aqueous solution is a sulfuric acid aqueous solution, the sulfuric acid concentration in the sulfuric acid aqueous solution is 0.5-2% (w / v), the heating reaction temperature is 110-130° C., and the heating reaction time is 0.5-2 h.

3. The method for recovering lignin and cellulose by using pine wood powder from forestry waste as claimed in claim 1, characterized in that: In the second step, the reaction temperature is 110-170° C., the reaction time is 60-240 min, the gas is pure oxygen, the reaction pressure is 0.5-2.5 MPa, and the stirring speed is 100-1000 r / min.

4. The method for recovering lignin and cellulose by using pine wood powder from forestry waste as claimed in claim 1, characterized in that: In the second step, the concentration of γ-valerolactone is 20%-100% (w / v); the alkali metal oxide is magnesium oxide, and the concentration of the alkali metal oxide is 3%-20% (w / v).

5. The method for recovering lignin and cellulose by using pine wood powder from forestry waste as claimed in claim 1, characterized in that: In the third step, hydrochloric acid with a pH of 1-3 is added to the filtrate B to precipitate lignin, namely, γ-valerolactone-lignin precipitation.

6. The method for recovering lignin and cellulose by using pine wood powder from forestry waste as claimed in claim 1, characterized in that: In the second step, the reaction temperature is 150° C., the reaction time is 60 min, the gas is pure oxygen, the magnesium oxide content is 15% (w / w), and the reaction pressure is 2 MPa.

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