A method for removing lignin from lignocellulose raw materials using molecular sieves and a reaction device thereof

Abstract

The present invention discloses a method for removing lignin from a lignocellulose raw material by using a molecular sieve, the method comprising the following steps: placing the lignocellulose raw material in a mixed solution of hydrogen peroxide and glacial acetic acid, adding the molecular sieve and steaming the lignocellulose raw material to obtain a lignocellulose raw material from which lignin is removed, wherein the molecular sieve is a FeY molecular sieve. The method of the present invention achieves the purpose of removing or separating lignin by adding hydrogen peroxide and acetic acid to produce a synergistic effect with the FeY molecular sieve to oxidize toxic and difficult-to-degrade organic compounds, and the whiteness of the lignocellulose raw material treated by the method can reach 85ISO, and a finished product with high whiteness and high lignin removal rate can be obtained by a one-step method.

Description

Technical Field

[0001] The invention belongs to the technical field of biomass, and in particular relates to a method for removing lignin from lignocellulose raw materials by using molecular sieves. Background Art

[0002] In lignocellulosic raw materials, its composition usually includes three parts: lignin, cellulose and hemicellulose. Among them, lignin, cellulose and hemicellulose are cross-linked with each other, and lignin is rigid and not easy to corrode, and usually plays a supporting role in cells.

[0003] The traditional method for removing lignin is the strong alkali removal method. However, this treatment method has problems such as the inability to regenerate and circulate waste liquid, residual metal ions, and environmental pollution during the reaction process. The processed lignin raw materials require pre-treatment such as pressurization, crushing and grinding. The process is complicated. The maximum thickness of the processed raw materials needs to be less than 0.5mm. It will also cause lignin to be converted into lignin salts, changing the original structure of lignin, which is not in line with the green, efficient and recyclable chemical concept.

[0004] Therefore, it is an urgent problem to be solved by technicians in this field to provide a method for removing lignin with simple processing technology, environmental friendliness, low production cost and high removal efficiency. Summary of the invention

[0005] In view of this, the present invention provides a method for removing lignin from a lignocellulosic raw material by using a molecular sieve. The method adds hydrogen peroxide and acetic acid to produce a synergistic effect with the FeY molecular sieve to oxidize toxic and difficult-to-degrade organic compounds, thereby achieving the purpose of removing or separating lignin. The whiteness of the lignocellulosic raw material treated by this method can reach 85ISO, and a finished product with high whiteness and high lignin removal rate can be obtained in one step; and the thickness of the treated lignocellulosic raw material can reach 30 mm, and there is no need to crush or grind it into fine particles in advance, so the processing efficiency is greatly improved.

[0006] In order to achieve the above object, the present invention adopts the following technical solution:

[0007] A method for removing lignin from a lignocellulosic raw material using a molecular sieve, the method comprising the following steps:

[0008] The lignocellulose raw material is put into a mixed solution of hydrogen peroxide and glacial acetic acid, and molecular sieve is added and cooked to obtain the lignocellulose raw material with lignin removed.

[0009] The present invention utilizes the characteristic of transition metal (Fe) that it is easy to obtain electrons and utilizes its synergistic effect with hydrogen peroxide and acetic acid to in situ generate hydroxyl radicals (·OH), organic free radicals (RC·), superoxide free radicals (·O 2- ) and singlet oxygen (1 O2) and other highly active substances are used to separate lignin from lignocellulosic raw materials, solving the problem of difficult treatment of highly polluted waste liquid from lignocellulosic raw materials during pulp production.

[0010] Preferably, the concentration of the hydrogen peroxide is 20-50%, and the concentration of the 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 the hydrogen peroxide is 30%, and the concentration of the glacial acetic acid is 99%.

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

[0014] Preferably, the molecular sieve is a FeY molecular sieve, and the molar ratio of effective components in the molecular sieve is 0.5Na2O:0.167Al2O3:1SiO2:22.5H2O:xFeSO4:yH2O2 (x=0-0.01, y=0-0.15).

[0015] Preferably, the mass ratio of the molecular sieve 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 of 40-90° C., and reaction time of 2-6 h.

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

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

[0020] Preferably, the lignocellulosic raw material is selected from at least one of pine, eucalyptus, basswood and fir, and the delignified lignocellulosic raw material can be used for pulp production.

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

[0022] The reaction device of the method described above comprises a reactor, wherein a feed inlet and an exhaust port are provided on the top of the reactor;

[0023] A first circulation port is provided at the bottom of the side wall of the reactor, and is connected to a second circulation port provided at the upper part of the first circulation port through a peristaltic pump;

[0024] A discharge port is provided in the middle of the bottom of the reactor, and electric heating devices are provided on both sides of the discharge port;

[0025] A stirring paddle is arranged on the top of the reactor, and a molecular sieve layer is arranged on the side wall of the reactor above the stirring paddle.

[0026] Preferably, the electric heating device comprises an electric heating sleeve and silicate rock wool.

[0027] Preferably, the exhaust port is connected to a water tank.

[0028] A stirring paddle is added to the reactor to accelerate the reaction, and the discharge port is at the bottom of the reactor; a peristaltic pump is installed outside the reactor to accelerate the reaction of the mixed solution in the reactor, and an electric heating jacket and silicate rock wool are installed outside the reactor to heat up and keep warm; during the reaction, the FeY molecular sieve will be filled in the 500 mesh 316L stainless steel mesh layer, and the molecular sieve can be recycled.

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

[0030] The present invention provides a method for removing lignin from lignocellulosic raw materials by using molecular sieves. In plant lignocellulosic raw materials, lignin, cellulose and hemicellulose are cross-linked with each other, and lignin is rigid and not easy to corrode, and usually plays a supporting role in cells. However, due to the polyhydroxy structure of lignin, when treated with an alkali method, lignin will attach new groups to become lignin salts and dissolve in water, which destroys the original structure of lignin. Under acidic conditions, lignin usually maintains its original structure. Therefore, the present invention utilizes the synergistic effect of glacial acetic acid, hydrogen peroxide and FeY molecular sieves and the characteristics of transition metals that are easy to obtain electrons to generate hydroxyl radicals (·OH), organic free radicals (RC·), superoxide free radicals (·O 2- ) and singlet oxygen ( 1 O2) and other highly active substances, which can achieve a lignin removal rate of 94% and a hemicellulose removal rate of 91% in the lignocellulose raw materials within 6 hours, and the method does not produce wastewater, and the fiber whiteness after treatment can reach 85ISO; and the method does not produce wastewater and does not destroy the original structure of lignin, the solution can be reused, and environmental pollution is reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. The drawings in this description are only embodiments of the present invention.

[0032] Figure 1 is a structural diagram of the reaction device of the present invention;

[0033] Among them, 1-reaction kettle, 2-feeding port, 3-exhaust port, 4-discharging port, 5-peristaltic pump, 6-first circulation port, 7-second circulation port, 8-stirring paddle, 9-net column, 10-electric heating device, 11-water tank. DETAILED DESCRIPTION

[0034] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0035] like Figure 1 The present invention provides a reaction device for removing lignin from a lignocellulose raw material, comprising a reactor 1, a feed port 2 and an exhaust port 3 are provided on the top of the reactor 1; the exhaust port 3 is connected to a water tank 11;

[0036] A first circulation port 6 is provided at the bottom of the side wall of the reactor 1, and the first circulation port 6 is connected to a second circulation port 7 provided on the upper part of the first circulation port 6 through a peristaltic pump 5, and switch valves are provided on both sides of the peristaltic pump 5; a discharge port 4 is provided in the middle of the bottom of the reactor 1, and electric heating devices 10 are provided on both sides of the discharge port 4, and the electric heating devices include electric heating sleeves and silicate rock wool;

[0037] A stirring paddle is provided on the top of the reactor 1, and a molecular sieve mesh layer is provided on the side wall of the reactor above the stirring paddle; the mesh layer is a 500-mesh 316L stainless steel mesh layer;

[0038] The reaction process of the device is as follows: load the catalyst into the stainless steel mesh layer, then put the raw materials into the reactor through the feed port, turn on the electric heating device and the stirring device, turn on the peristaltic pump and the switch valve to circulate the reaction solution to accelerate the reaction of the mixed solution in the reactor. After the reaction is completed, open the discharge port to take out the wood cellulose raw material, and at the same time, the water tank collects the exhaust gas generated by the exhaust port.

[0039] Example 1

[0040] A method for removing lignin from lignocellulose raw materials using molecular sieves, the specific steps are as follows:

[0041] (1) Preparation of molecular sieve: Under room temperature, a mixture of NaOH and NaAlO2 was added to silica sol, and after stirring for 3 h, Fenton's reagent was added, wherein the Fenton's reagent was a mixed reagent of iron and hydrogen peroxide, wherein the molar ratio of hydrogen peroxide to ferric sulfate was H2O2:FeSO4=15:1, and the mixture was stirred in a water bath at 80°C for 9 h. After suction filtration and washing with deionized water, the mixture was dried at 80°C to obtain FeY molecular sieve; the molar composition of FeY molecular sieve was 0.5Na2O:0.167Al2O3:1SiO2:22.5H2O:0.01FeSO4:0.15H2O 2, , FeY molecular sieve is packaged and granulated, the granulation particle size is 2mm, and the molecular sieve content is 60%.

[0042] (2) Weigh 78.08 g of hydrogen peroxide (30%) and 165.09 g of glacial acetic acid (99%) and mix them to obtain a mixed solution, that is, the mass ratio of hydrogen peroxide to glacial acetic acid is 1:2.1; then take 2.43 g of FeY molecular sieve and 122 g of eucalyptus chips (50*50*10 mm, with a water content of less than 55%), that is, the mass ratio of the lignocellulosic raw material, the mixed solution, and the molecular sieve is 50:100:1; soak the lignocellulosic raw material in the mixed solution for 20 minutes, then add the FeY molecular sieve, heat it to 60°C within 20 minutes, keep it at a constant temperature for 4 hours, and cool it to room temperature after the reaction is completed;

[0043] The reaction solution is subjected to solid-liquid separation to obtain molecular sieve, raw material solid and liquid, wherein the molecular sieve can be reused; the liquid is dried at a temperature of 80°C to obtain a solid powder, namely lignin; during the reaction process, glacial acetic acid can be recycled by condensation reflux; the separated solid can be uniformly decomposed by a grinder or a pulper to prepare pulp, wherein the pulp whiteness can reach 85ISO, the lignin removal rate is 94%, and the hemicellulose removal rate is 91%;

[0044] Example 2

[0045] (1) Preparation of molecular sieves is the same as in Example 1

[0046] (2) 175.38 g of hydrogen peroxide (30%) and 62.22 g of glacial acetic acid (99%) were mixed to obtain a mixed solution, i.e., the mass ratio of hydrogen peroxide to glacial acetic acid was 1:0.35; 2.37 g of FeY molecular sieve and 118.8 g of eucalyptus wood chips (50*50*10 mm, with a water content of less than 55%) were then taken, i.e., the mass ratio of the lignocellulosic raw material, the mixed solution, and the molecular sieve was 50:100:1. The mixed solution was first soaked in the lignocellulosic raw material for 20 minutes, and then the FeY molecular sieve was added. The temperature was raised to 60°C within 20 minutes and then kept constant for 4 hours. After the reaction was completed, it was cooled to room temperature;

[0047] The reaction solution is subjected to solid-liquid separation to obtain molecular sieve, raw material solid and liquid, wherein the molecular sieve can be reused; the liquid is dried at a temperature of 80°C to obtain a solid powder, namely lignin; during the reaction process, the glacial acetic acid can be recycled through condensation reflux; the separated solid can be uniformly decomposed by a grinder or a pulper to prepare pulp, wherein the pulp whiteness can reach 85ISO, the lignin removal rate is 94%, and the hemicellulose removal rate is 91%.

[0048] Example 3

[0049] (1) Preparation of molecular sieves is the same as in Example 1

[0050] (2) Weigh 78.08 g of hydrogen peroxide (30%) and 165.09 g of glacial acetic acid (99%) and mix them to obtain a mixed solution, that is, the mass ratio of hydrogen peroxide to glacial acetic acid is 1:2.1; then take 2.43 g of FeY molecular sieve and 122 g of eucalyptus chips (50*50*30 mm, water content less than 55%), that is, the mass ratio of lignocellulosic raw material, mixed solution and molecular sieve is 50:100:1. Soak the lignocellulosic raw material in the mixed solution for 20 minutes, then add the FeY molecular sieve, heat it to 60°C within 20 minutes, keep it constant for 4 hours, and cool it to room temperature after the reaction is completed;

[0051] The reaction solution is subjected to solid-liquid separation to obtain molecular sieve, raw material solid and liquid, wherein the molecular sieve can be reused; the liquid is dried at a temperature of 80°C to obtain a solid powder, namely lignin; during the reaction process, glacial acetic acid can be recycled by condensation reflux; the separated solid can be uniformly decomposed by a grinder or a pulper to prepare pulp, wherein the pulp whiteness can reach 85ISO, the lignin removal rate is 94%, and the hemicellulose removal rate is 91%;

[0052] Example 4

[0053] (1) Preparation of molecular sieves is the same as in Example 1

[0054] (2) Take 200.0g of hydrogen peroxide (30%) and 40.0g of glacial acetic acid (99%) and mix them to obtain a mixed solution, that is, the mass ratio of hydrogen peroxide to glacial acetic acid is 1:0.2; then take 2.40g of FeY molecular sieve and 120.0g of eucalyptus chips (50*50*30mm, water content less than 55%), that is, the mass ratio of lignocellulosic raw material, mixed solution and molecular sieve is 50:100:1. Soak the lignocellulosic raw material in the mixed solution for 20 minutes, then add FeY molecular sieve, heat it to 60°C within 20 minutes, keep it at a constant temperature for 4.5 hours, and cool it to room temperature after the reaction is completed;

[0055] The reaction solution is subjected to solid-liquid separation to obtain molecular sieve, raw material solid and liquid, wherein the molecular sieve can be reused; the liquid is dried at a temperature of 80°C to obtain a solid powder, namely lignin; during the reaction process, glacial acetic acid can be recycled by condensation reflux; the separated solid can be uniformly decomposed by a grinder or a pulper to prepare pulp, wherein the pulp whiteness is 85ISO, the lignin removal rate is 94%, and the hemicellulose removal rate is 91%;

[0056] Example 5

[0057] (1) Preparation of molecular sieves is the same as in Example 1

[0058] (2) 43.64 g of hydrogen peroxide (30%) and 196.36 g of glacial acetic acid (99%) were mixed to obtain a mixed solution, i.e., the mass ratio of hydrogen peroxide to glacial acetic acid was 1:4.5; 2.40 g of FeY molecular sieve and 120.0 g of eucalyptus wood chips (50*50*30 mm, with a water content of less than 55%) were then taken, i.e., the mass ratio of the lignocellulosic raw material, the mixed solution, and the molecular sieve was 50:100:1. The mixed solution was first soaked in the lignocellulosic raw material for 20 minutes, and then the FeY molecular sieve was added. The temperature was raised to 60°C within 20 minutes and then kept constant for 4.5 hours. After the reaction was completed, it was cooled to room temperature;

[0059] The reaction solution is subjected to solid-liquid separation to obtain molecular sieve, raw material solid and liquid, wherein the molecular sieve can be reused; the liquid is dried at a temperature of 80°C to obtain a solid powder, namely lignin; during the reaction process, glacial acetic acid can be recycled by condensation reflux; the separated solid can be uniformly decomposed by a grinder or a pulper to prepare pulp, wherein the pulp whiteness is 85ISO, the lignin removal rate is 94%, and the hemicellulose removal rate is 91%;

[0060] Example 6

[0061] (1) Preparation of molecular sieves is the same as in Example 1

[0062] (2) Weigh 78.08g of hydrogen peroxide (30%) and 165.09g of glacial acetic acid (99%) and mix them to obtain a mixed solution, that is, the mass ratio of hydrogen peroxide to glacial acetic acid is 1:2.1; then take 0.049g of FeY molecular sieve and 122g of eucalyptus chips (50*50*30mm, water content less than 55%), that is, the mass ratio of lignocellulose raw material, mixed solution and molecular sieve is 50:100:0.02, and the mass ratio of molecular sieve to mixed solution is 1:5000. Soak the lignocellulose raw material in the mixed solution for 20 minutes, then add FeY molecular sieve, heat it to 60°C within 20 minutes, keep it constant for 6 hours, and cool it to room temperature after the reaction is completed;

[0063] The reaction solution is subjected to solid-liquid separation to obtain molecular sieve, raw material solid and liquid, wherein the molecular sieve can be reused; the liquid is dried at a temperature of 80°C to obtain a solid powder, namely lignin; during the reaction process, glacial acetic acid can be recycled by condensation reflux; the separated solid can be uniformly decomposed by a grinder or a pulper to prepare pulp, wherein the pulp whiteness can reach 85ISO, the lignin removal rate is 94%, and the hemicellulose removal rate is 91%;

[0064] Example 7

[0065] (1) Preparation of molecular sieves is the same as in Example 1

[0066] (2) Weigh 78.08g of hydrogen peroxide (30%) and 165.09g of glacial acetic acid (99%) and mix them to obtain a mixed solution, that is, the mass ratio of hydrogen peroxide to glacial acetic acid is 1:2.1; then take 2.43g of FeY molecular sieve and 244g of eucalyptus chips (50*50*30mm, water content less than 55%), that is, the mass ratio of lignocellulosic raw material, mixed solution and molecular sieve is 100:100:1. Soak the lignocellulosic raw material in the mixed solution for 20 minutes, then add FeY molecular sieve, the mass ratio of lignocellulosic raw material to the mixed solution is 1:1, heat it to 60°C within 20 minutes, keep it at a constant temperature for 6 hours, and cool it to room temperature after the reaction is completed;

[0067] The reaction solution is subjected to solid-liquid separation to obtain molecular sieve, raw material solid and liquid, wherein the molecular sieve can be reused; the liquid is dried at a temperature of 80°C to obtain a solid powder, namely lignin; during the reaction process, glacial acetic acid can be recycled by condensation reflux; the separated solid can be uniformly decomposed by a grinder or a pulper to prepare pulp, wherein the pulp whiteness can reach 85ISO, the lignin removal rate is 94%, and the hemicellulose removal rate is 91%;

[0068] Comparative Example 1

[0069] The difference between Comparative Example 1 and Example 1 is that the solution for removing lignocellulose is prepared by a traditional method, that is, the raw materials are sodium hydroxide and sodium sulfite. 26.0 g of sodium hydroxide and 13.1 g of sodium sulfite are mixed in 260 g of deionized water to form a 2.5 mol / L sodium hydroxide and 0.4 mol / L sodium sulfite solution, and the reaction is carried out at 103° C. for 6 hours. The lignin removal rate is 43%. This method requires a high temperature, and a large amount of sodium ions will remain in the solution, and the solution cannot be recycled. The relevant data results are shown in Table 1.

[0070] The difference between the relevant comparative examples 2-7 and the embodiment 1 is that the use and proportion of the lignocellulose raw material, the mixed solution and the molecular sieve are different. The relevant specific parameters and results are shown in Table 1.

[0071] Table 1 Raw material ratios and results of Examples 1-7 and Comparative Examples 1-7

[0072]

[0073]

[0074] As can be seen from the above table, the present invention utilizes the synergistic effect of glacial acetic acid, hydrogen peroxide and FeY molecular sieve and the characteristic of transition metals being easy to obtain electrons to in situ generate hydroxyl radicals (·OH), organic free radicals (RC·), superoxide free radicals (·O 2- ) and singlet oxygen ( 1 O2) and other highly active substances, which can achieve a lignin removal rate of 94% and a hemicellulose removal rate of 91% in the lignocellulose raw materials within 6 hours, and this method does not produce wastewater. The fiber whiteness after treatment can reach 85ISO; this method does not produce wastewater and does not destroy the original structure of lignin. The solution can be reused to reduce environmental pollution. There is no need to crush and grind the raw materials. The raw material thickness can be up to 30mm, which is a significant improvement.

[0075] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one 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 present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for removing lignin from a lignocellulosic raw material using a molecular sieve, characterized in that: The method comprises the following steps: The lignocellulose raw material is placed in a mixed solution of hydrogen peroxide and glacial acetic acid, and a molecular sieve is added and cooked to obtain the lignocellulose raw material from which lignin is removed; 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 1:1.0-3.0; The molecular sieve is a FeY molecular sieve, wherein the molar ratio of the effective components in the molecular sieve is 0.5Na2O:0.167Al2O3:1SiO2:22.5H2O:xFeSO4:yH2O2, x=0~0.01, y=0~0.15; The mass ratio of the molecular sieve to the mixed solution is 1:50-5000; The thickness of the lignocellulose raw material is 0-30 mm; The cooking parameters are: temperature of 40-90° C. and reaction time of 2-6 h.

2. A method for removing lignin from lignocellulose raw materials using molecular sieves according to claim 1, characterized in that: The filtrate obtained after the cooking is dried to obtain lignin.

3. The method for removing lignin from lignocellulose raw materials using molecular sieves according to claim 1, characterized in that: The lignocellulose raw material is any one of bamboo, coniferous wood and broadleaved wood.

Images