Method for preparing amino lignin by using ammonia water

Abstract

The invention belongs to the technical field of lignin modification, and discloses a method for preparing amino lignin by using ammonia water, which comprises the following steps: S1, collecting a lignocellulose biomass raw material, and crushing the lignocellulose biomass raw material into powder; s2, pretreating the lignocellulose biomass powder obtained in the step S1 through liquid amino so as to synchronously realize removal and amination of lignin; s3, carrying out solid-liquid separation on the mixture pretreated in S2, and collecting pretreated black liquor; s4, separating and separating out amino lignin solids from the pretreated black liquor through an anti-solvent method; s5, collecting amino lignin solids through solid-liquid separation, and washing and refining the amino lignin solids through absolute ethyl alcohol; s6, drying to obtain an amino lignin product; according to the method, the amino lignin with higher chemical specificity and higher commercial added value is prepared from the liquid amino pretreatment black liquor rich in lignin through anti-solvent crystallization.

Description

Technical Field

[0001] The invention relates to the technical field of lignin modification, and in particular to a method for preparing amino lignin by utilizing ammonia water. Background Art

[0002] With the rise of the "lignin first" biorefining concept, the value of lignin has become the key to biorefining. Traditionally, lignin is regarded as a "must-remove" component, but in the new generation of biorefining technology, the recycling of lignin is regarded as one of the key breakthrough technologies. The recovery rate and efficiency of lignin directly affect the overall value of biomass.

[0003] Lignin can be converted into products with higher added value, such as phenols and polymers, through a series of chemical modification methods. It can not only play a role in energy production, but also has broad market prospects in the development of new materials. Current chemical modification methods include esterification, etherification and amination, among which the amination method shows great potential in a variety of application scenarios due to its high reactivity.

[0004] Although existing amination methods can improve the reactivity of lignin, these methods usually have some shortcomings. For example, even if the Mannich reaction method introduces multiple amine groups into the product, it is difficult to accurately control the number of amine groups in the product, which affects the commercial application of amino lignin.

[0005] Therefore, finding a more efficient lignin amination technology is one of the problems that technicians in this field urgently need to solve. Summary of the invention

[0006] The present invention is intended to provide a method for preparing amino lignin using ammonia water, wherein the liquid amino pretreatment waste liquid rich in lignin is prepared by simple and easy anti-solvent crystallization to obtain amino lignin with higher chemical specificity and higher commercial added value, which can be applied to a variety of research and application scenarios for separating and regenerating amino lignin from liquid amino in lignocellulosic biomass. The problems in the background technology are solved.

[0007] In order to achieve the above object, the present invention provides the following technical solutions:

[0008] A method for preparing amino lignin using ammonia water comprises the following steps:

[0009] S1, collecting lignocellulosic biomass raw materials and crushing them into powder;

[0010] S2, pretreating the lignocellulosic biomass powder obtained in S1 with liquid amino groups, thereby simultaneously achieving lignin removal and amination;

[0011] S3, performing solid-liquid separation on the mixture obtained by the pretreatment in S2, and collecting the pretreated black liquor;

[0012] S4, separating and precipitating amino lignin solids from the pretreated black liquor by an anti-solvent method;

[0013] S5, collecting amino lignin solids by solid-liquid separation, and washing and refining the amino lignin solids by anhydrous ethanol;

[0014] S6. Drying to obtain an amino lignin product.

[0015] Furthermore, the lignocellulosic biomass raw materials include office waste paper, corrugated paper, rice straw, wheat straw, rape straw, corn straw, corn cobs, bagasse, bamboo powder, sawdust, nut shells, citrus peel residue, grapefruit peel, pepper seeds, coffee grounds, pepper, litsea cubeba, houttuynia cordata and fish vanilla.

[0016] Furthermore, the method of pretreating lignocellulosic biomass powder with liquid amino group is ammonia leaching method, ultrasound-assisted ammonia leaching method or ammonia recovery percolation method.

[0017] Furthermore, the ammonia leaching method comprises the following steps:

[0018] A1. Add lignocellulosic biomass powder and ammonia water with a mass concentration of 15-30 wt % into a reaction vessel at a solid-liquid ratio of 1:2-1:10, and then add a stirrer into the reaction vessel and seal it;

[0019] A2. Place the sealed reaction container obtained in A1 into an oil bath or a water bath shaker for magnetic stirring or shaking. Heat to 40-90°C and start timing. After reacting for 6-24 hours, take out the reaction container and wait until it cools to room temperature to obtain black liquor.

[0020] Furthermore, the ultrasonic-assisted ammonia leaching method comprises the following steps:

[0021] B1, adding lignocellulosic biomass powder and ammonia water with a mass concentration of 15-30wt% into a reaction container at a solid-liquid ratio of 1:2-1:10;

[0022] B2, inserting an ultrasonic probe with an ultrasonic amplifier power of 0 to 950 W and a frequency of 20 kHz into a depth of about 1 cm below the surface of the lignocellulosic biomass ammonia solution obtained in B1, and then sealing the reaction container;

[0023] B3. Place the sealed reaction container obtained in B2 in an oil bath and heat it to a high temperature. After reacting at 40-90°C for 6-24 hours, take out the reaction container and wait for it to cool to room temperature to obtain black liquor. During the reaction, the ultrasonic device is operated in an intermittent mode.

[0024] Further, the ammonia recovery diafiltration method comprises the following steps:

[0025] C1. Add lignocellulosic biomass powder into a reaction vessel, preheat the reaction vessel for 25 minutes, and always introduce nitrogen gas at a pressure of 2.5 MPa into the reaction system;

[0026] C2. Ammonia water with a mass concentration of 10-15wt% is fed into the reaction container through a peristaltic pump, the solid-liquid ratio of lignocellulosic biomass powder to ammonia water is 1:2-3:10, the reaction time is 10min, the void volume is 45mL, and after the reaction is completed, the reactor is rapidly quenched to obtain black liquor.

[0027] Further, in step S4, the specific method of the anti-solvent method is:

[0028] Anhydrous ethanol anti-solvent is added to the pretreated black liquor, the ratio of black liquor to anhydrous ethanol is 2:1-1:7, after being fully mixed, it is allowed to stand for crystallization, small black solid particles appear after standing for 1-3 hours, and all amino lignin solids can be precipitated after standing for 2-3 days.

[0029] The beneficial effects of the technical solution are:

[0030] Through liquid amino pretreatment, lignin removal and amination are achieved simultaneously. At the same time, amino lignin solid is precipitated from the pretreated black liquor by the anti-solvent method. After refining and drying, the obtained amino lignin not only has high chemical specificity, but also has broader application prospects.

[0031] The invention can significantly improve the recovery rate and sedimentation rate of lignin, while reducing the impact on the environment, and provides an effective way for high value-added utilization of lignocellulosic biomass.

[0032] The present invention can not only be applied to the regeneration of black liquor pretreated with liquid amino in lignin cellulose biomass, but also be widely applicable to various raw materials rich in lignin, such as office waste paper, rice straw, etc., greatly improving the recovery value of lignin and the economy of commercial application. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 is a process flow chart of preparing amino lignin by ammonia leaching method in Example 1 of the present invention;

[0034] Figure 2 is a process flow chart of preparing amino lignin by ultrasound-assisted ammonia leaching in Example 2 of the present invention;

[0035] Figure 3 is a process flow chart of preparing amino lignin by dilute ammonia water ammonia recovery percolation method in Example 3 of the present invention;

[0036] Figure 4 is the FTIR spectrum of amino lignin solid provided by the embodiment of the present invention;

[0037] Figure 5 3 is a thermogravimetric analysis diagram of amino lignin solid provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0038] The present invention is further described in detail below in conjunction with the accompanying drawings and embodiments:

[0039] Example 1 Preparation of amino lignin (AL) (such as Figure 1 )

[0040] (1) Walnut shells were crushed into fine powder (>75 mesh) as lignocellulosic biomass (LCB) raw material.

[0041] (2) Using dilute ammonia pretreatment to simultaneously remove and aminize lignin:

[0042] Weigh 3g of walnut shell powder and put it into a 50mL hydrothermal reactor, then add 18mL of 20% ammonia water, add a stirrer, seal it well, put it in an oil bath and start heating and magnetic stirring. Start timing after the temperature rises to 90℃ (Note: the temperature of ammonia water cannot rise suddenly). Take out the reactor after 10 hours of reaction, and open the bottle cap after the reactor cools to room temperature. The hydrothermal reactor is a safe sealed container. Ammonia water will release ammonia vapor and water vapor as the temperature rises, causing the pressure in the reactor to increase.

[0043] (3) Solid-liquid separation and collection of pre-treated black liquor:

[0044] The black liquid after pretreatment with dilute ammonia is collected by vacuum filtration, and the solid obtained by solid-liquid separation is placed in an oven for drying. Since the lignin is removed (the LCB without lignin is named DLLCB), the dried solid can be used for the subsequent simultaneous saccharification and fermentation process to produce cellulosic ethanol (EtOH).

[0045] (4) Precipitating amino lignin solids by anti-solvent method:

[0046] Add 4 times the volume of anhydrous ethanol anti-solvent to the pretreated black liquor, mix thoroughly, and let stand for crystallization. After standing for 1 to 3 hours, small black solid particles appear. It takes 2 to 3 days for all the precipitates to precipitate.

[0047] (5) Solid-liquid separation, collection and purification of amino lignin solids:

[0048] The solid-liquid phase was transferred to a suction filtration device for suction filtration, and the solid was collected and purified by washing with anhydrous ethanol.

[0049] (6) Drying / drying the refined amino lignin solid:

[0050] After the washing liquid was clarified, the refined aminolignin solid was collected in a petri dish and dried in a convection oven at 55°C to obtain a dark brown solid, which was ground into a brown powder.

[0051] (7) Analysis and characterization of chemical parameters of amino lignin:

[0052] ①Elemental analysis: FlashSmart elemental analyzer (CHNS / O) was used to perform elemental analysis on amino lignin solid samples and alkaline lignin control samples. In order to ensure the accuracy of the results, the sample powder should be fully ground to achieve absolute homogeneity, and the sample should be as dry as possible with as little water as possible. When packing the sample, the tin cup should be folded into a cylindrical shape. Note that the tin cup cannot be broken and the sample cannot be exposed. A blank sample needs to be made before measuring the sample. Since this analysis does not require the determination of the S content of the sample, V2O5 does not need to be added when packing the empty tin cup and packing the sample.

[0053] ②Bypass package sample: Place 2-3 mg of standard sample into a tin cup as a debugging sample to confirm the instrument performance status.

[0054] ③ Drawing of the standard curve: weigh the tin cup and return to zero. Wrap 2-3 mg of chemical standard (equipped with the instrument) in the tin cup to ensure that the sample does not leak out easily. The weighed standard must have a certain gradient and only 3-5 are needed. Record the weight after wrapping. This weight can be regarded as the horizontal coordinate in the standard curve. The content of each component corresponds to the vertical coordinate in the standard curve. The instrument will automatically detect and draw a fitting standard curve and save the method.

[0055] ④ Sample packaging: First set the balance to zero, weigh the empty tin cup, peel it after it stabilizes, add 3 to 4 mg of sample powder to the tin cup, remove it from the balance, weigh it again after the sample is packaged, record the data at this time after it stabilizes, and enter this weight into the instrument setting record.

[0056] ⑤ Place the packaged samples into the automatic sampler one by one and set the program for automatic testing.

[0057] Table 1 shows the element ratio and peak area carbon-nitrogen ratio of amino lignin solid samples, with alkaline lignin as a control.

[0058] Table 1 Element ratio and peak area carbon-nitrogen ratio of amino lignin solid samples

[0059]

[0060] Note: 90℃-EtOH and 120℃-EtOH in the table are amino lignin solid samples. 90℃-EtOH means the pretreatment temperature is 90℃, the anti-solvent is ethanol, and so on. Figure 5The sample numbers in are the same as in this table.

[0061] (8) Analysis and characterization of physical parameters of amino lignin:

[0062] ① Fourier transform infrared spectroscopy analysis: Nicolet iS20 FTIR spectrometer (Fourier transform infrared spectrometer) was used to perform Fourier transform infrared spectroscopy analysis on the amino lignin solid sample and the alkaline lignin control sample. The FTIR spectrum can determine the specific groups in the sample material by the peak position, which is very important for whether the lignin is amino. The sample was pretreated by the KBr powder pressing method, and then infrared detection was performed at 500-4000cm-1. The FTIR spectrum of the amino lignin solid sample (with alkaline lignin as the control) is shown in Figure 4 .

[0063] ② Thermogravimetric analysis: Thermogravimetric analysis of amino lignin solid sample and alkaline lignin control sample was performed in the range of 0-900℃ using STA 4493F3 synchronous thermal analyzer. The thermogravimetric analysis diagram of amino lignin solid sample (with alkaline lignin as control) is shown in Figure 5 .

[0064] Example 2 Preparation of amino lignin (such as Figure 2 )

[0065] (1) The walnut shells were crushed into fine powder (>75 mesh) as raw materials.

[0066] (2) Using ultrasound-assisted ammonia pretreatment to simultaneously achieve lignin removal and amination:

[0067] 10 g corn cob and 60 mL of 15% ammonia water were placed in a 100 mL screw bottle and treated with 20 kHz ultrasound at 60°C for 12 h. The ultrasonic probe was inserted about 1 cm below the surface of the sample solution.

[0068] (3) Solid-liquid separation and collection of pre-treated black liquor:

[0069] After ultrasonic-assisted ammonia pretreatment, the black liquid after ultrasonic-assisted ammonia pretreatment was collected by vacuum filtration, and the solid (USAA-treated corn cob, USAACC) was washed with deionized water until the pH value of the filtrate reached neutral and then placed in an oven for drying. Since lignin was removed, the dried solid can be used for the subsequent simultaneous saccharification and fermentation (SSF) process to produce cellulosic ethanol.

[0070] (4) Precipitating amino lignin solids by anti-solvent method:

[0071] Add 4 times the volume of anhydrous ethanol anti-solvent to the pretreated black liquor, mix thoroughly, and let stand for crystallization. After standing for 1 to 3 hours, small black solid particles appear. It takes 2 to 3 days for all the precipitates to precipitate.

[0072] (5) Solid-liquid separation, collection and purification of amino lignin solids:

[0073] The solid-liquid phase is transferred to a suction filtration device for suction filtration, the solid is collected and purified by washing with anhydrous ethanol, and the filtered liquid is collected once and used for the determination in step seven.

[0074] (6) Drying / drying the refined amino lignin solid:

[0075] After the washing liquid was clarified, the refined aminolignin solid was collected in a petri dish and dried in a convection oven at 55°C to obtain a dark brown solid, which was ground into a brown powder.

[0076] Example 3 Preparation of amino lignin (such as Figure 3 )

[0077] (1) The walnut shells were crushed into fine powder (>75 mesh) as raw materials.

[0078] (2) Using dilute ammonia water to recover ammonia and perform filtration pretreatment to simultaneously achieve lignin removal and amination:

[0079] Take 15g of rape straw fine powder (>75 mesh) and put it into a 70mL continuous reaction vessel without pre-soaking. Preheat the reaction vessel for 25 minutes, and then always introduce nitrogen at a pressure of 2.5MPa into the reaction system to prevent the boiling of ammonia water. Then send 30-50mL of ammonia water with a mass concentration of 10-15wt% into the reactor through a peristaltic pump, the reaction time is 10min, and the void volume is 45mL. The pumped black liquor enters the evaporator and is heated to form ammonia vapor, and is re-blended into dilute ammonia water with a fixed mass concentration (10-15wt%) in the liquid storage tank. Finally, it is pumped to realize the circulation of ammonia water and reflux into the reaction system. After the reaction is completed, the reactor is quickly quenched.

[0080] (3) Precipitating amino lignin solids by anti-solvent method:

[0081] The initial pH of the remaining pretreated black liquor in the evaporator is about 12, and the solid content rises to 50wt%. The above black liquor is pumped into the crystallization tank, and 4 times the volume of anhydrous ethanol anti-solvent is added. After sufficient mixing, it is allowed to stand for crystallization. After standing for 1 to 3 hours, small black solid particles appear. It takes 2 to 3 days for all the precipitation to precipitate.

[0082] (4) Solid-liquid separation, collection and purification of amino lignin solids:

[0083] The solid-liquid phase is transferred to a suction filtration device for suction filtration, and the solid is collected and washed and refined with anhydrous ethanol to obtain amino lignin solid.

[0084] (5) Drying / drying the refined amino lignin solid:

[0085] After the washing liquid was clarified, the refined aminolignin solid was collected in a petri dish and dried in a convection oven at 55°C to obtain a dark brown solid, which was ground into a brown powder.

[0086] The above is only an embodiment of the present invention, and the common knowledge such as the known specific technical solutions or characteristics in the solution is not described in detail here. It should be pointed out that for those skilled in the art, several modifications and improvements can be made without departing from the technical solution of the present invention, which should also be regarded as the protection scope of the present invention, and these will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the specification can be used to interpret the content of the claims.

Claims

1. A method for preparing amino lignin using ammonia water, characterized in that: The following steps are involved: S1, collecting lignocellulosic biomass raw materials and crushing them into powder; S2, pretreating the lignocellulosic biomass powder obtained in S1 with liquid amino groups, thereby simultaneously achieving lignin removal and amination; S3, performing solid-liquid separation on the mixture obtained by the pretreatment in S2, and collecting the pretreated black liquor; S4, separating and precipitating amino lignin solids from the pretreated black liquor by an anti-solvent method; S5, collecting amino lignin solids by solid-liquid separation, and washing and refining the amino lignin solids by anhydrous ethanol; S6. Drying to obtain an amino lignin product.

2. The method for preparing amino lignin using aqueous ammonia according to claim 1, characterized in that: In step S1, the lignocellulosic biomass raw materials include office waste paper, corrugated paper, rice straw, wheat straw, rape straw, corn straw, corn cobs, bagasse, bamboo powder, sawdust, nut shells, citrus peel residue, grapefruit peel, pepper seeds, coffee grounds, pepper, litsea cubeba, houttuynia cordata and fish vanilla.

3. The method for preparing amino lignin using ammonia water according to claim 1, characterized in that: In step S2, the method of pretreating the lignocellulosic biomass powder with liquid amino groups is an ammonia leaching method, an ultrasound-assisted ammonia leaching method or an ammonia recovery percolation method.

4. The method for preparing amino lignin using aqueous ammonia according to claim 3, characterized in that: The ammonia leaching method comprises the following steps: A1. Add lignocellulosic biomass powder and ammonia water with a mass concentration of 15-30 wt % into a reaction vessel at a solid-liquid ratio of 1:2-1:10, and then add a stirrer into the reaction vessel and seal it; A2. Place the sealed reaction container obtained in A1 into an oil bath or a water bath shaker for magnetic stirring or shaking. Heat to 40-90°C and start timing. After reacting for 6-24 hours, take out the reaction container and wait until it cools to room temperature to obtain black liquor.

5. The method for preparing amino lignin using aqueous ammonia according to claim 3, characterized in that: The ultrasonic-assisted ammonia leaching method comprises the following steps: B1, adding lignocellulosic biomass powder and ammonia water with a mass concentration of 15-30wt% into a reaction container at a solid-liquid ratio of 1:2-1:10; B2, inserting an ultrasonic probe with an ultrasonic amplifier power of 0 to 950 W and a frequency of 20 kHz into a depth of about 1 cm below the surface of the lignocellulosic biomass ammonia solution obtained in B1, and then sealing the reaction container; B3. Place the sealed reaction container obtained in B2 in an oil bath and heat it to a high temperature. After reacting at 40-90°C for 6-24 hours, take out the reaction container and wait for it to cool to room temperature to obtain black liquor. During the reaction, the ultrasonic device is operated in an intermittent mode.

6. The method for preparing amino lignin using aqueous ammonia according to claim 3, characterized in that: The ammonia recovery diafiltration method comprises the following steps: C1. Add lignocellulosic biomass powder into a reaction vessel, preheat the reaction vessel for 25 minutes, and always introduce nitrogen gas at a pressure of 2.5 MPa into the reaction system; C2. Ammonia water with a mass concentration of 10-15wt% is fed into the reaction container through a peristaltic pump, the solid-liquid ratio of lignocellulosic biomass powder to ammonia water is 1:2-3:10, the reaction time is 10min, the void volume is 45mL, and after the reaction is completed, the reactor is rapidly quenched to obtain black liquor.

7. The method for preparing amino lignin using aqueous ammonia according to claim 1, characterized in that: In step S4, the specific method of the anti-solvent method is: Anhydrous ethanol anti-solvent is added to the pretreated black liquor, the ratio of black liquor to anhydrous ethanol is 2:1-1:7, after being fully mixed, it is allowed to stand for crystallization, small black solid particles appear after standing for 1-3 hours, and all amino lignin solids can be precipitated after standing for 2-3 days.

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