A method for removing lignin from lignocellulosic raw material using a catalyst and a reaction device thereof

Abstract

The application discloses a method for removing lignin from lignocellulose raw materials by using a catalyst, and comprises the following steps: placing the lignocellulose raw materials into a mixed solution of hydrogen peroxide and glacial acetic acid, and adding a catalyst to cook the lignocellulose raw materials, so that the cooked lignocellulose raw materials are lignocellulose raw materials from which lignin is removed, wherein the catalyst is Mn / Fe / Bi@Al2O3. The method can realize the purpose of removing or separating lignin by adding hydrogen peroxide and acetic acid to produce a synergistic effect with the Mn / Fe / Bi@Al2O3 catalyst, and oxidizing toxic and refractory organic compounds. In addition, the whiteness of the lignocellulose raw materials treated by the method can reach 90ISO, and the finished product with high whiteness and high lignin removal rate can be obtained by one-step method.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of biomass, and particularly relates to a method for removing lignin from lignocellulose raw materials by using a catalyst and a reaction device thereof. BACKGROUND

[0002] In lignocellulose raw materials, the composition usually includes three parts: lignin, cellulose and hemicellulose. Among them, lignin, cellulose and hemicellulose are cross-linked with each other, and lignin has rigidity and is not easy to be corroded, and usually plays a supporting role in cells.

[0003] The traditional method for removing lignin is a strong alkali removal method, but this treatment method has problems such as waste liquid cannot be regenerated and recycled, metal ion residues, environmental pollution, etc. in the reaction process. The lignin raw materials treated need to be pretreated by pressurization, crushing and grinding, pre-soaking, etc. The process is complex, the maximum thickness of the treated raw materials needs to be less than 0.5 mm, and it will also cause lignin to be converted into lignin salt, changing the original structure of lignin, which does not meet the green and efficient recyclable chemical concept.

[0004] Therefore, it is an urgent problem for those skilled in the art to provide a method for removing lignin with simple treatment process, environmental friendliness, low production cost and high removal efficiency. SUMMARY

[0005] Therefore, the present application provides a method for removing lignin from lignocellulose raw materials by using a catalyst and a reaction device thereof. The method produces a synergistic effect by adding hydrogen peroxide and acetic acid with Mn / Fe / Bi@Al2O3 catalyst, oxidizes toxic and refractory organic compounds, so as to achieve the purpose of removing or separating lignin. The whiteness of the lignocellulose raw materials treated by this method can reach 90ISO, and high whiteness and high lignin removal rate of the finished product can be obtained by one-step method. The thickness of the treated lignocellulose raw materials can reach 30mm, and there is no need to crush or grind into small particles in advance, so the treatment efficiency is greatly improved.

[0006] In order to achieve the above purpose, the present application adopts the following technical solutions:

[0007] A method for removing lignin from lignocellulose raw materials by using a catalyst, the method comprising the following steps:

[0008] The lignocellulose raw materials are put into a mixed solution of hydrogen peroxide and glacial acetic acid, and the catalyst is added for cooking to obtain lignocellulose raw materials from which lignin is removed.

[0009] This invention utilizes the characteristic that transition metals (Mn, Fe, Bi) readily gain electrons, and leverages their synergistic effect with hydrogen peroxide and acetic acid to generate hydroxyl radicals (·OH), organic free radicals (RC·), and superoxide radicals (·O) in situ. 2- ) and singlet oxygen ( 1 Highly active substances such as O2 are used to separate lignin from lignocellulosic raw materials, solving the problem of difficult treatment of highly polluting waste liquid from lignin removal in lignocellulosic raw materials during pulp production.

[0010] Preferably, the concentration of hydrogen peroxide is 20-50%, and the concentration of glacial acetic acid is 95-99%.

[0011] The mass ratio of the hydrogen peroxide to the glacial acetic acid is 1:0.2-4.5.

[0012] Preferably, the concentration of hydrogen peroxide is 30%, and the concentration of glacial acetic acid is 99%.

[0013] Preferably, the mass ratio of the lignocellulose raw material to the mixed solution is 1:1.0-3.0.

[0014] Preferably, the catalyst is Mn / Fe / Bi@Al2O3, and the mass ratio of the effective components in the catalyst is Mn:Fe:Bi:Al2O3 = 2.09:0.56:0.41:10.

[0015] Preferably, the mass ratio of the catalyst to the mixed solution is 1:50-5000.

[0016] Preferably, the thickness of the lignocellulose raw material is 0-30 mm.

[0017] Preferably, the cooking parameters are: temperature 40-90℃, reaction time 2-6h.

[0018] Preferably, the temperature is 60°C.

[0019] Preferably, the filtrate obtained after cooking is lignin after drying.

[0020] Preferably, the lignocellulose raw material is selected from at least one of pine, eucalyptus, linden and fir, and the lignocellulose raw material after lignin removal can be used for pulp production.

[0021] Preferably, the lignocellulose raw material is any one of bamboo, coniferous wood, and broadleaf wood.

[0022] The reaction apparatus of the above-described method includes a reaction vessel, the top of which is provided with a feed inlet and an exhaust outlet;

[0023] The bottom of the side wall of the reactor is provided with a first circulation port, which is connected to a second circulation port located above the first circulation port via a peristaltic pump; the bottom of the side wall of the reactor is also provided with a discharge port.

[0024] The reactor is equipped with a catalyst suspension device at the top and a sloped surface at the bottom that faces the discharge port.

[0025] The bottom of the reactor is designed to be inclined to facilitate the removal of the reacted lignocellulose raw material; a peristaltic pump is installed outside the reactor to accelerate the reaction of the mixed solution inside the reactor; during the reaction, the Mn / Fe / Bi@Al2O3 catalyst is packed in a 400-mesh 316L stainless steel mesh column, and the catalyst can be recycled.

[0026] Preferably, the catalyst suspension device includes a suspension support plate fixed to the top of the reactor and a mesh column for holding the catalyst.

[0027] Preferably, the bottom of the reactor is equipped with an electric heating device.

[0028] Preferably, the vent is connected to the water tank.

[0029] As can be seen from the above technical solution, compared with the prior art, the beneficial effects of the present invention are as follows:

[0030] This invention provides a method for removing lignin from lignocellulosic raw materials using a catalyst. In plant-based lignocellulosic raw materials, lignin, cellulose, and hemicellulose are cross-linked, and lignin is rigid and resistant to corrosion, typically playing a supporting role in cells. However, due to its polyhydroxyl structure, lignin forms lignin salts that dissolve in water when treated with an alkaline method, thus disrupting its original structure. Under acidic conditions, lignin usually retains its original structure. Therefore, this invention utilizes the synergistic effect of glacial acetic acid, hydrogen peroxide, and a Mn / Fe / Bi@Al2O3 catalyst, along with the electron-acquiring characteristics of transition metals, to generate hydroxyl groups (·OH), organic free radicals (RC·), and superoxide radicals (·O) in situ. 2- ) and singlet oxygen ( 1 Highly active substances such as O2 can achieve a lignin removal rate of 99% and a hemicellulose removal rate of 95% in lignocellulose raw materials within 6 hours. Furthermore, this method does not generate wastewater, and the whiteness of the treated fiber can reach 90 ISO. In addition, this method does not generate wastewater and does not damage the original structure of lignin. The solution can be reused, reducing environmental pollution. Attached Figure Description

[0031] In order to make the technical solutions in the embodiments of the present application or the prior art clearer, the accompanying drawings needed in the embodiments or the prior art description will be briefly introduced. The accompanying drawings in the description are only some embodiments of the present application.

[0032] Figure 1 The structure diagram of the reaction device of the present application;

[0033] Wherein, 1-reaction kettle, 2-feed inlet, 3-exhaust port, 4-discharge port, 5-first circulation port, 6-second circulation port, 7-peristaltic pump, 8-water tank, 9-electric heating device, 10-net column, 11-hanging support plate. DETAILED DESCRIPTION

[0034] The technical solutions in the embodiments of the present application will be described clearly and completely. Obviously, the described embodiments are only some embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all the other embodiments obtained by those skilled in the art without creative labor are within the protection scope of the present application.

[0035] As Figure 1 , the present application provides a reaction device for removing lignin from lignocellulosic raw materials, comprising a reaction kettle 1, the top of the reaction kettle 1 is provided with a feed inlet 2 and an exhaust port 3; the exhaust port 3 is connected with a water tank 8;

[0036] The bottom of the side wall of the reaction kettle 1 is provided with a first circulation port 5, the first circulation port 5 is connected with a second circulation port 6 arranged on the upper part of the first circulation port 5 through a peristaltic pump 7, and the two sides of the peristaltic pump 7 are respectively provided with on-off valves; the bottom of the side wall of the reaction kettle 1 is also provided with a discharge port 4;

[0037] The inner top of the reaction kettle 1 is provided with a catalyst hanging device, and the inner bottom of the reaction kettle 1 is an inclined surface inclined to the discharge port 4; the inner bottom of the reaction kettle 1 is provided with an electric heating device 9 below the inclined surface;

[0038] The catalyst hanging device comprises a hanging support plate 11 fixed on the top of the reaction kettle 1 and a net column 10 for loading catalyst, and the net column is a 400-mesh 316L stainless steel net column;

[0039] The device reaction process is as follows: the catalyst is loaded into the stainless steel net column, then the raw materials are put into the reaction kettle through the feed inlet, the electric heating device is turned on, the peristaltic pump and the on-off valves are turned on to circulate the reaction solution, the mixed solution is accelerated to react in the reaction kettle, after the reaction is completed, the discharge port is opened to take out the lignocellulosic raw materials, and the water tank collects the exhaust gas generated from the exhaust port.

[0040] Embodiment 1

[0041] A method for removing lignin from lignocellulosic raw materials by using a catalyst, the specific steps are as follows:

[0042] (1) Catalyst preparation: Al2O3 10 g, 1 wt% nitric acid 15 g and Sesbania powder 0.5 g were mixed in a beaker, and extruded into strips in a semi-solid state, dried in an oven at 80°C for 6h, and then calcined at 1300°C in a muffle furnace for 8h to obtain the shaped Al2O3;

[0043] Bi(NO3)3·5H2O 4.8512 g, Fe(NO3)3·9H2O 4.0399 g, MnCl2·4H2O 1.465 g were mixed in 150 mL ultrapure water, 5 mL concentrated nitric acid was added to prevent Bi from hydrolyzing, and the calcined shaped Al2O3 was placed in it, and left to stand for 2h, then taken out and dried in an oven at 80°C for 5h, and then taken out and calcined in a muffle furnace at 450°C for 5h to obtain the Mn / Fe / Bi@Al2O3 catalyst;

[0044] (2) Hydrogen peroxide (30%) 78.08 g and glacial acetic acid (99%) 165.09 g were mixed to obtain a mixed solution, i.e. the mass ratio of hydrogen peroxide to glacial acetic acid was 1:2.1; Mn / Fe / Bi@Al2O3 catalyst 2.43 g was mixed in a beaker, and eucalyptus wood chips (50*50*10mm, water content less than 55%) 122 g, i.e. lignocellulose raw material, were mixed, and the mass ratio of the three was 50:100:1, and the temperature was raised to 60°C within 20 min and kept constant for 4h, and then cooled to room temperature after the reaction was completed;

[0045] The reaction solution was subjected to solid-liquid separation to obtain the catalyst, the solid raw material and the liquid, and the catalyst could be reused; the liquid was dried at a temperature of 80°C to obtain a solid powder, i.e. lignin; in the reaction process, the glacial acetic acid could be recycled by condensation reflux; the separated solid could be uniformly decomposed by a grinding machine or a beater to prepare paper pulp, and the brightness of the paper pulp could reach 90ISO, the lignin removal rate was 99%, and the hemicellulose removal rate was 99%;

[0046] Example 2

[0047] (1) Catalyst preparation same as Example 1

[0048] (2) Take hydrogen peroxide (30%) 175.38g and glacial acetic acid (99%) 62.22g mixed to get mixed solution, namely the mass ratio of hydrogen peroxide to glacial acetic acid is 1:0.35; then take Mn / Fe / Bi@Al2O3 catalyst 2.37g, eucalyptus chips (50*50*10mm, water content less than 55%) 118.8g, namely the mass ratio of lignocellulose raw material, mixed solution, catalyst is 50:100:1, through heating, the temperature is raised to 60℃ within 20min, and then constant temperature for 4h, after the reaction is completed, it is cooled to room temperature;

[0049] The reaction complete solution is subjected to solid-liquid separation to obtain catalyst, raw material solid and liquid, wherein the catalyst can be reused; the liquid is dried at a temperature of 80℃ to obtain solid powder, which is lignin; in the reaction process, the glacial acetic acid can be recycled by condensation reflux; the separated solid is uniformly decomposed by a grinding machine or a beater to prepare paper pulp, wherein the brightness of the paper pulp can reach 90ISO, the lignin removal rate is 99%, and the hemicellulose removal rate is 99%.

[0050] Example 3

[0051] (1) The preparation of catalyst is the same as example 1

[0052] (2) Take hydrogen peroxide (30%) 78.08g and glacial acetic acid (99%) 165.09g mixed to get mixed solution, namely the mass ratio of hydrogen peroxide to glacial acetic acid is 1:2.1; then take Mn / Fe / Bi@Al2O3 catalyst 2.43g in a beaker, eucalyptus chips (50*50*30mm, water content less than 55%) 122g, namely the mass ratio of lignocellulose raw material, mixed solution, catalyst is 50:100:1, through heating, the temperature is raised to 60℃ within 20min, and then constant temperature for 4h, after the reaction is completed, it is cooled to room temperature;

[0053] The reaction complete solution is subjected to solid-liquid separation to obtain catalyst, raw material solid and liquid, wherein the catalyst can be reused; the liquid is dried at a temperature of 80℃ to obtain solid powder, which is lignin; in the reaction process, the glacial acetic acid can be recycled by condensation reflux; the separated solid is uniformly decomposed by a grinding machine or a beater to prepare paper pulp, wherein the brightness of the paper pulp can reach 90ISO, the lignin removal rate is 99%, and the hemicellulose removal rate is 99%.

[0054] Example 4

[0055] (1) The preparation of catalyst is the same as example 1

[0056] (2) Take hydrogen peroxide (30%) 200.0 g and glacial acetic acid (99%) 40.0 g after mixing to get mixed solution, namely the mass ratio of hydrogen peroxide to glacial acetic acid is 1:0.2; take Mn / Fe / Bi@Al2O3 catalyst 2.40 g, eucalyptus fragments (50*50*30mm, water content is less than 55%) 120.0 g, namely the mass ratio of lignocellulose raw material, mixed solution, catalyst is 50:100:1, through heating, the temperature is raised to 60℃ within 20 min, and then constant temperature for 4.5 h, after the reaction is completed, it is cooled to room temperature;

[0057] The reaction complete solution is subjected to solid-liquid separation to obtain catalyst, raw material solid and liquid, wherein the catalyst can be repeatedly used; the liquid is dried at a temperature of 80℃ to obtain solid powder, which is lignin; in the reaction process, the glacial acetic acid can be recycled by condensation reflux; the separated solid is uniformly decomposed by a grinding machine or a beater to prepare paper pulp, wherein the paper pulp whiteness is 90ISO, the lignin removal rate is 99%, and the hemicellulose removal rate is 99%;

[0058] Example 5

[0059] (1) The preparation of catalyst is the same as example 1

[0060] (2) Take hydrogen peroxide (30%) 43.64 g and glacial acetic acid (99%) 196.36 g after mixing to get mixed solution, namely the mass ratio of hydrogen peroxide to glacial acetic acid is 1:4.5; take Mn / Fe / Bi@Al2O3 catalyst 2.40 g, eucalyptus fragments (50*50*30mm, water content is less than 55%) 120.0 g, namely the mass ratio of lignocellulose raw material, mixed solution, catalyst is 50:100:1, through heating, the temperature is raised to 60℃ within 20 min, and then constant temperature for 4.5 h, after the reaction is completed, it is cooled to room temperature;

[0061] The reaction complete solution is subjected to solid-liquid separation to obtain catalyst, raw material solid and liquid, wherein the catalyst can be repeatedly used; the liquid is dried at a temperature of 80℃ to obtain solid powder, which is lignin; in the reaction process, the glacial acetic acid can be recycled by condensation reflux; the separated solid is uniformly decomposed by a grinding machine or a beater to prepare paper pulp, wherein the paper pulp whiteness is 90ISO, the lignin removal rate is 99%, and the hemicellulose removal rate is 99%;

[0062] Example 6

[0063] (1) The preparation of catalyst is the same as example 1

[0064] (2) Take hydrogen peroxide (30%) 78.08g and glacial acetic acid (99%) 165.09g to mix, then get mixed solution, namely the mass ratio of hydrogen peroxide to glacial acetic acid is 1:2.1; Take Mn / Fe / Bi@Al2O3 catalyst 0.049g in a beaker, eucalyptus chips (50*50*30mm, water content is less than 55%) 122g, namely the mass ratio of lignocellulose raw material, mixed solution, catalyst is 50:100:0.02, the mass ratio of catalyst to mixed solution is 1:5000, through heating, the temperature is raised to 60℃ within 20min, then constant temperature for 6h, after the reaction is completed, cool to room temperature;

[0065] The reaction solution is subjected to solid-liquid separation to obtain catalyst, raw material solid and liquid, wherein the catalyst can be reused; the liquid is dried at a temperature of 80℃ to obtain solid powder, which is lignin; in the reaction process, the glacial acetic acid can be recycled by condensation reflux; the separated solid is uniformly decomposed by a grinding machine or a beater to prepare paper pulp, wherein the brightness of the paper pulp can reach 90ISO, the lignin removal rate is 99%, and the hemicellulose removal rate is 99%;

[0066] Example 7

[0067] (1) The preparation of catalyst is the same as example 1

[0068] (2) Take hydrogen peroxide (30%) 78.08g and glacial acetic acid (99%) 165.09g to mix, then get mixed solution, namely the mass ratio of hydrogen peroxide to glacial acetic acid is 1:2.1; Take Mn / Fe / Bi@Al2O3 catalyst 2.43g in a beaker, eucalyptus chips (50*50*30mm, water content is less than 55%) 244g, namely the mass ratio of lignocellulose raw material, mixed solution, catalyst is 100:100:1, the mass ratio of lignocellulose raw material to mixed solution is 1:1, through heating, the temperature is raised to 60℃ within 20min, then constant temperature for 6h, after the reaction is completed, cool to room temperature;

[0069] The reaction solution is subjected to solid-liquid separation to obtain catalyst, raw material solid and liquid, wherein the catalyst can be reused; the liquid is dried at a temperature of 80℃ to obtain solid powder, which is lignin; in the reaction process, the glacial acetic acid can be recycled by condensation reflux; the separated solid is uniformly decomposed by a grinding machine or a beater to prepare paper pulp, wherein the brightness of the paper pulp can reach 90ISO, the lignin removal rate is 99%, and the hemicellulose removal rate is 99%;

[0070] Comparative example 1

[0071] The difference between Comparative Example 1 and Example 1 is that the lignocellulose removal solution was prepared using a traditional method, namely, the raw materials are sodium hydroxide and sodium sulfite. 26.0g of sodium hydroxide and 13.1g of sodium sulfite were mixed in 260g of deionized water to prepare a 2.5mol / L sodium hydroxide and 0.4mol / L sodium sulfite solution. The reaction was carried out at 103℃ for 6h, and the lignin removal rate was 43%. This method requires a high temperature, and a large amount of sodium ions will remain in the solution. The solution cannot be recycled. The relevant data results are shown in Table 1.

[0072] The differences between Comparative Examples 2-10 and Example 1 lie in the use and proportions of lignocellulose raw materials, mixed solutions, and catalysts. Specific parameters and results are shown in Table 1.

[0073] Table 1. Raw material ratios and results for Examples 1-7 and Comparative Examples 1-10

[0074]

[0075]

[0076] As shown in the table above, this invention utilizes the synergistic effect of glacial acetic acid, hydrogen peroxide, and transition metal (Mn, Fe, Bi) catalysts, as well as the characteristic that transition metals readily gain electrons, to generate hydroxyl radicals (·OH), organic free radicals (RC·), and superoxide radicals (·O) in situ. 2- ) and singlet oxygen ( 1 Highly active substances such as O2 can achieve a lignin removal rate of 99% and a hemicellulose removal rate of 95% in lignocellulose raw materials within 6 hours. This method does not generate wastewater, and the whiteness of the treated fiber can reach 90 ISO. Furthermore, this method does not generate wastewater and does not damage the original structure of lignin. The solution can be reused, reducing environmental pollution. It also eliminates the need to crush and grind the raw materials, and the raw material thickness can be up to 30 mm, which is a significant improvement.

[0077] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for removing lignin from a lignocellulosic feedstock using a catalyst, characterized by, The method comprises the following steps: The lignocellulose raw material is put into a mixed solution of hydrogen peroxide and glacial acetic acid, and a catalyst is added to obtain a lignocellulose raw material with removed lignin after cooking; The concentration of the hydrogen peroxide is 20-50%, and the concentration of the glacial acetic acid is 95-99%; The mass ratio of the hydrogen peroxide to the glacial acetic acid is 1:0.2-4.5; The mass ratio of the lignocellulose raw material to the mixed solution is 1:2.0-3.0; The catalyst is Mn / Fe / Bi@Al2O3, wherein the mass ratio of effective components in the catalyst is Mn:Fe:Bi:Al2O3=2.09:0.56:0.41:10; The mass ratio of the catalyst to the mixed solution is 1:50-5000.

2. The method for removing lignin from lignocellulosic feedstock using a catalyst according to claim 1, characterized in that, The thickness of the lignocellulose raw material is 0-30mm.

3. The method for removing lignin from lignocellulosic feedstock using a catalyst according to claim 1, characterized in that, The parameters of the cooking are as follows: the temperature is 40-90℃, and the reaction time is 2-6h.

4. The method for removing lignin from lignocellulosic feedstock using a catalyst according to claim 1, characterized in that, The filtrate obtained after the cooking is dried to obtain lignin.

5. The method for removing lignin from lignocellulosic feedstock using a catalyst according to claim 1, characterized in that, The lignocellulose raw material is any one of bamboo, coniferous wood and broad-leaved wood.

6. A reaction apparatus for the process according to any one of claims 1 to 5, characterized in that The reaction kettle is provided with a feeding port and an exhaust port at the top; The bottom of the side wall of the reaction kettle is provided with a first circulation port, which is connected with a second circulation port arranged at the upper part of the first circulation port through a peristaltic pump; the bottom of the side wall of the reaction kettle is also provided with a discharging port; The inner top of the reaction kettle is provided with a catalyst suspension device, and the bottom is a slope inclined to the discharging port.

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