Construction of a model for microwave-assisted hydrothermal pretreatment of acacia components and a method for pulping thereof

Abstract

This invention belongs to the field of pulping and papermaking technology, and provides a method for constructing a model of component leaching in acacia wood pretreated with microwave-assisted hydrothermal treatment and a method for pulping it. The model was constructed using the component leaching content as a parameter after microwave-assisted hydrothermal pretreatment of acacia wood. The F-value was 161.6355, P < 0.05, reaching a significant level, indicating a very good fit. The R-value of the model is... 2 The value was 0.9728, and the mean square error was 0.0318, indicating a reliable prediction result. The treated acacia wood chips were then subjected to sulfate pulping. The pulp was screened, beaten, defatted, and then processed into paper. The prepared paper exhibited excellent properties, with a tear index of 2.76–7.36 mN·m. 2 / g, tensile index is 44.4-102 N·m / g, burst index is 1.91-6.12 kPa·m 2 The ring compression index is 9.77–14.67 N·m / g. This invention provides a powerful tool for evaluating pretreatment effects and optimizing process parameters, further enhancing the scientific rigor and practicality of the research.

Description

Technical Field

[0001] This invention belongs to the technical field of pulp and paper making, specifically relating to the construction of a microwave-assisted hydrothermal pretreatment model for the dissolution of acacia wood components and its pulping method. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] Acacia wood, a common timber resource, is mainly composed of cellulose, hemicellulose, lignin, and extractives. These components are tightly bound together through physical mixing or covalent bonds, forming a structure that is difficult to degrade, limiting its high-value utilization. In traditional chemical pulping, acacia wood chips are not pretreated, and most of the hemicellulose and lignin are directly degraded and enter the pulping waste liquid, which is then burned as low-value fuel in the alkali recovery system, resulting in a waste of biomass resources. Adding pretreatment before pulping to separate and extract some hemicellulose and lignin for high-value utilization is an effective way to solve the problem of biomass resource waste in traditional chemical methods. Hydrothermal pretreatment uses water as the only solvent to hydrolyze biomass, and has been widely used due to its advantages such as being green and pollution-free, having relatively low equipment requirements, and having less damaging effects on cellulose. However, traditional hydrothermal methods suffer from high energy consumption and long reaction times. Furthermore, it is impossible to accurately predict the dissolution of components during the pretreatment stage before pulping. Summary of the Invention

[0004] To address the aforementioned issues, this invention provides a method for constructing a lignin leaching model for microwave-assisted hydrothermal pretreatment of acacia wood components and for pulping it. This invention enables accurate prediction of lignin leaching during microwave-assisted hydrothermal pretreatment. Using this model can reduce the amount of subsequent cooking chemicals used, improve the hydrothermal pretreatment effect, and enhance the quality of acacia wood pulp.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] In a first aspect, the present invention provides a method for constructing a microwave-assisted hydrothermal pretreatment model for the dissolution of components in acacia wood, comprising:

[0007] Microwave-assisted hydrothermal pretreatment was performed on acacia wood chips, followed by solid-liquid separation. The pretreated wood chips and pretreatment liquid were collected separately, and the treatment temperature and time were recorded.

[0008] Measure the amount of lignin dissolved in the pretreatment solution;

[0009] The least squares method was used to fit the data of treatment temperature, treatment time and lignin dissolution to establish a microwave-assisted hydrothermal pretreatment model for the dissolution of components in acacia wood.

[0010] Determine the optimal conditions corresponding to the target lignin dissolution rate based on the model;

[0011] The acacia wood chips are pretreated under microwave-assisted hydrothermal conditions to obtain the desired product.

[0012] This invention proposes a model for the dissolution of components in acacia wood under microwave-assisted hydrothermal pretreatment and a pulping method thereof, which can predict the dissolution content of lignin in the microwave-assisted hydrothermal pretreatment stage and improve the pretreatment effect.

[0013] In some implementations, the regression equation is:

[0014] ;

[0015] ;

[0016] in, To handle temperature, Y represents the processing time and the amount of lignin dissolved.

[0017] In some implementations, Matlab R2024a is used to fit the obtained data. The R... 2 The mean squared error was 0.9728, the standard deviation was 0.0318, and the estimated standard deviation was 0.1825, indicating a reliable prediction. The validation F-value was 161.6355, with P < 0.05, showing a very good fit.

[0018] In some embodiments, the method for determining the amount of lignin leaching is as follows: take the pretreatment solution, adjust the pH to 3.5-3.6, centrifuge, collect the precipitate, continue centrifuging and washing until neutral, dry and weigh to obtain the weight of acid-insoluble lignin;

[0019] The supernatant was diluted, and the absorbance of the supernatant sample at 205 nm was detected using a UV spectrophotometer to calculate the concentration of acid-soluble lignin.

[0020] A second aspect of the present invention provides a system for constructing a microwave-assisted hydrothermal pretreatment model for the dissolution of components in acacia wood, comprising:

[0021] This module is used for microwave-assisted hydrothermal pretreatment of acacia wood chips, solid-liquid separation, collection of pretreated wood chips and pretreatment liquid, and recording of treatment temperature and treatment time.

[0022] Module for measuring the amount of lignin dissolved in the pretreatment solution;

[0023] This module is used to fit the data of treatment temperature, treatment time and lignin dissolution using the least squares method to establish a microwave-assisted hydrothermal pretreatment model for the dissolution of components in acacia wood.

[0024] This module is used to determine the optimal conditions corresponding to the target lignin dissolution rate based on the model.

[0025] Module for microwave-assisted hydrothermal pretreatment of acacia wood chips under optimal conditions.

[0026] More specifically, including:

[0027] S1. Select qualified wood chips, mix qualified acacia wood chips with deionized water and pretreat with microwave-assisted hydrothermal treatment at a microwave power of 500-800 W. After the reaction is completed, perform solid-liquid separation and collect the pretreated wood chips and liquid for later use.

[0028] S2. The amount of lignin leaching in the pretreatment solution was measured. The relationship between microwave-assisted hydrothermal pretreatment conditions and lignin leaching was analyzed using the least squares method. The obtained data were fitted using Matlab R2024a.

[0029] S3. The wood chips after microwave-assisted hydrothermal treatment are cooked and pulped at a temperature of 150-170℃ for 60-120 minutes with a liquor ratio of 1:4-7. The pulp after cooking is washed and screened to obtain chemical pulp.

[0030] A third aspect of the present invention provides a method for preparing chemical pulp from acacia wood using microwave-assisted hydrothermal treatment, comprising:

[0031] Based on the above method, the treatment temperature and treatment time of microwave-assisted hydrothermal treatment were determined, and acacia wood chips were subjected to microwave-assisted hydrothermal treatment, solid-liquid separation was performed, and the pretreated wood chips were collected.

[0032] The pretreated wood chips are steamed to obtain pulp;

[0033] The pulp is pulped, loosened, and then paper-made to obtain paper.

[0034] In some embodiments, the acacia wood chips are 2-2.5 cm long, 3-5 mm thick, and 1-2 cm wide.

[0035] In some embodiments, during the pretreatment process, the solid-liquid ratio of acacia wood to water is 1:4-7, the microwave power is 500-800 W, the treatment time is 20-100 min, and the treatment temperature is 120-190℃.

[0036] Preferably, the solid-liquid ratio of acacia wood to water is 1:5;

[0037] In some embodiments, the cooking temperature is 150-170°C, the cooking time is 60-120 min, and the liquid ratio is 1:4-7.

[0038] In some embodiments, the sulfate process is used for pulping, with an alkali content of 15% (calculated as Na2O), a sulfidation degree of 30%, a cooking temperature of 165°C, a heating time of 90 min, a holding time of 150 min, and a liquor ratio of 1:4.

[0039] Beneficial effects of the present invention

[0040] (1) The present invention found that during the microwave-assisted hydrothermal pretreatment of acacia wood, there is a significant correlation between the treatment time Xt, XT and the lignin dissolution amount Y. The established nonlinear equation has high accuracy, realizing a prediction of the lignin dissolution amount during the microwave-assisted hydrothermal pretreatment process, thus improving the hydrothermal pretreatment effect.

[0041] (2) The present invention uses wood chips that have undergone microwave-assisted hydrothermal pretreatment, which can effectively reduce the use of subsequent cooking chemicals, reduce energy consumption, reduce pretreatment time, and improve production efficiency.

[0042] (3) The present invention uses wood chips that have undergone microwave-assisted hydrothermal pretreatment for pulping, which can effectively improve pulp yield and paper physical properties.

[0043] (4) Compared with the traditional method of determining the optimal treatment process through experiments, the wood component leaching model constructed in this invention can quickly determine the corresponding optimal process conditions based on the target lignin leaching amount, with high prediction accuracy and simple steps. Attached Figure Description

[0044] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. Exemplary embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0045] Figure 1 The yield of fine pulp under different treatment conditions in Example 3;

[0046] Figure 2 The tear index of paper under different treatment conditions in Example 3;

[0047] Figure 3 The bursting strength index of paper under different treatment conditions in Example 3;

[0048] Figure 4 The tensile index of paper under different treatment conditions in Example 3;

[0049] Figure 5 The ring crush index is the paper's ring crush index under different treatment conditions in Example 3. Detailed Implementation

[0050] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0051] Terminology Explanation:

[0052] "Lignin dissolution rate" refers to the amount of lignin dissolved in the pretreatment solution.

[0053] The present invention will be further described in detail below with reference to specific embodiments. It should be noted that the specific embodiments are explanations of the present invention and not limitations thereof.

[0054] Example 1: A method for microwave-assisted hydrothermal pretreatment of acacia wood, specifically including the following steps:

[0055] 1. Raw material preparation. Manually select acacia wood chips of the appropriate size, and air-dry them for later use.

[0056] 2. Weigh 30 g of wood chips (octane-dry weight) into a polytetrafluoroethylene (PTFE) container. Add 150 ml of deionized water at a liquid-to-liquid ratio of 1:5 (g / ml). Set the microwave power to 500 W and perform hydrothermal pretreatment in a microwave hydrothermal synthesizer at 170℃ for 60 min. After the reaction, separate the solid and liquid components. Transfer the pre-hydrolyzed liquid to a bottle and store it in a refrigerator at 4℃. Air-dry the solid portion for subsequent chemical pulping.

[0057] 3. Take a certain amount of pre-hydrolyzed solution into a centrifuge tube, adjust the pH to 3.5, centrifuge to achieve solid-liquid separation, wash the precipitate to neutral, dry and weigh to obtain the weight of acid-insoluble lignin. Dilute the supernatant to an appropriate factor, and use a UV spectrophotometer to detect the absorbance of the supernatant sample at 205 nm. Calculate the concentration of acid-soluble lignin. Add 72 wt% H2SO4 to the supernatant to make the sulfuric acid concentration in the pre-hydrolyzed solution 4 wt%. Then place it in a digester and incubate at 121℃ for 60 min. After digestion, dilute the liquid to a certain factor, and use ion chromatography to determine the monosaccharide components and content.

[0058] Comparative Example 1

[0059] The process is basically the same as the previous example, except that microwaves are not used; instead, conventional hydrothermal pretreatment is employed.

[0060] Example 2: Establishing a correlation model between microwave-assisted hydrothermal pretreatment temperature, time, and lignin dissolution amount.

[0061] 1. Raw material preparation. Manually select acacia wood chips of the appropriate size, and air-dry them for later use.

[0062] 2. Weigh 30 g of wood chips (occasionally dry) into a polytetrafluoroethylene (PTFE) container, add 150 ml of deionized water at a liquid ratio of 1:5 (g / ml), set the microwave power to 500 W, and perform hydrothermal pretreatment in a microwave hydrothermal synthesizer. 22 different treatment conditions were set, as shown in Table 2.

[0063] 3. Hypothesized regression equation:

[0064]

[0065]

[0066] in, To handle temperature, The processing time is represented by a1, a2, a3, a4, a5, and b, which are coefficients to be determined.

[0067] Error equation:

[0068]

[0069] in, It's an error. These are experimental data. That's the theoretical value.

[0070] Sum of squared errors: Based on the principle of least squares, this invention aims to obtain the minimum sum of squared errors between experimental data and theoretical values, as shown in the following formula.

[0071]

[0072] 4. Using the 22 sets of data obtained in step 2 and the regression equation assumed in step 3, this invention uses Matlab R2024a to obtain the regression equation for microwave-assisted hydrothermal pretreatment temperature, time, and lignin dissolution as follows:

[0073]

[0074]

[0075] 5. Perform analysis of variance and significance tests on the obtained equation. The mean squared error (MSE) is 0.0318, and R0 is... 2 The F-value was 0.9728 and the estimated standard deviation was 0.1825, indicating that the prediction results are reliable. The F-value was 161.6355 and the P-value was less than 0.05, indicating that the regression was significant at the 0.05 level. In conclusion, the model constructed using the least squares method is feasible for predicting the amount of lignin dissolved during microwave-assisted hydrothermal pretreatment.

[0076] Example 3: A method for pulping acacia wood pretreated with microwave-assisted hydrothermal pretreatment

[0077] 1. Raw material preparation. Manually select acacia wood chips of the appropriate size, and air-dry them for later use.

[0078] 2. Weigh 100 g of wood chips (occasionally dry) into a polytetrafluoroethylene (PTFE) container. Add 500 ml of deionized water at a liquid-to-liquid ratio of 1:5 (g / ml). Set the microwave power to 500 W and perform hydrothermal pretreatment in a microwave hydrothermal synthesizer at a temperature of 120-190℃ for 60 min. After the reaction is complete, separate the solid and liquid components. Transfer the pre-hydrolyzed solution to a bottle and store it in a refrigerator at 4℃. Air dry the solid portion.

[0079] 3. After measuring the solids content of the acacia wood chips from step 2, perform sulfate cooking using a 15L electric rotary cooker containing four 1L stainless steel tanks. The treatment conditions are: 15% alkali (as Na₂O), 30% sulfidation, liquor ratio 1:4, holding temperature 165℃, and holding time 150 min. After cooking, rinse the pulp until the pH is neutral.

[0080] 4. The slurry from step 3 is screened through a slurry screening machine to obtain good slurry and coarse residue, and the yield of fine slurry is calculated.

[0081] 5. Dilute the slurry obtained in step 4 to a consistency of 10%, and then refine it using a PFI refiner. Set the freeness to 40±2 °SR. After refining, form it into sheets of 100 g / m³. 2 The unbleached paper was tested for its tear index, tensile index, bursting index, and ring crush index.

[0082] Comparative Example 2

[0083] Unlike Example 3, no pretreatment is used.

[0084] Table 1. Sugar content in solutions from conventional hydrothermal pretreatment and microwave-assisted hydrothermal pretreatment.

[0085]

[0086] Table 2. Lignin content under different treatment conditions

[0087]

[0088] As shown in Table 1, the microwave-assisted hydrothermal method can effectively increase the xylose content in the pretreatment solution.

[0089] From Table 2 and Figures 1-5According to the records, this invention achieves accurate prediction of lignin dissolution during microwave-assisted hydrothermal pretreatment. Using this model can reduce the amount of subsequent cooking chemicals used, improve the hydrothermal pretreatment effect and the quality of acacia pulp.

[0090] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for constructing a microwave-assisted hydrothermal pretreatment model for the dissolution of components in acacia wood, characterized in that, include: Microwave-assisted hydrothermal pretreatment was performed on acacia wood chips, followed by solid-liquid separation. The pretreated wood chips and pretreatment liquid were collected separately, and the treatment temperature and time were recorded. The acacia wood chips are 2-2.5 cm long, 3-5 mm thick, and 1-2 cm wide. During the pretreatment process, the solid-liquid ratio of acacia wood to water is 1:4-7, the microwave power is 500-800 W, the treatment time is 20-100 min, and the treatment temperature is 120-190℃. Measure the amount of lignin dissolved in the pretreatment solution; The least squares method was used to fit the data of treatment temperature, treatment time and lignin dissolution to establish a microwave-assisted hydrothermal pretreatment model for the dissolution of components in acacia wood. Determine the optimal conditions corresponding to the target lignin dissolution rate based on the model; The acacia wood chips are subjected to microwave-assisted hydrothermal pretreatment under optimal conditions to obtain the desired product. The regression equation is: ； ； in, To handle temperature, Y represents the processing time and the amount of lignin dissolved.

2. The method for constructing the microwave-assisted hydrothermal pretreatment dissolution model of Acacia coriander components as described in claim 1, characterized in that, The obtained data were fitted using Matlab R2024a.

3. The method for constructing the microwave-assisted hydrothermal pretreatment dissolution model of Acacia coriander components as described in claim 1, characterized in that, The method for determining the amount of lignin leaching is as follows: take the pretreatment solution, adjust the pH to 3.5-3.6, centrifuge, collect the precipitate, continue centrifuging and washing until neutral, dry and weigh to obtain the weight of acid-insoluble lignin; The supernatant was diluted, and the absorbance of the supernatant sample at 205 nm was detected using a UV spectrophotometer to calculate the concentration of acid-soluble lignin.

4. A system for constructing a microwave-assisted hydrothermal pretreatment model for the dissolution of components in acacia wood, characterized in that, include: This module is used for microwave-assisted hydrothermal pretreatment of acacia wood chips, solid-liquid separation, collection of pretreated wood chips and pretreatment liquid, and recording of treatment temperature and treatment time. The acacia wood chips are 2-2.5 cm long, 3-5 mm thick, and 1-2 cm wide. During the pretreatment process, the solid-liquid ratio of acacia wood to water is 1:4-7, the microwave power is 500-800 W, the treatment time is 20-100 min, and the treatment temperature is 120-190℃. Module for measuring the amount of lignin dissolved in the pretreatment solution; This module is used to fit the data of treatment temperature, treatment time and lignin dissolution using the least squares method to establish a microwave-assisted hydrothermal pretreatment model for the dissolution of components in acacia wood. This module is used to determine the optimal conditions corresponding to the target lignin dissolution rate based on the model. Module for microwave-assisted hydrothermal pretreatment of acacia wood chips under optimal conditions; The regression equation is: ； ； in, To handle temperature, Y represents the processing time and the amount of lignin dissolved.

5. A method for preparing chemical pulp from acacia wood using microwave-assisted hydrothermal treatment, characterized in that, include: Based on the method described in any one of claims 1-3, the processing temperature and processing time of microwave-assisted hydrothermal treatment are determined, and acacia wood chips are subjected to microwave-assisted hydrothermal treatment, solid-liquid separation is performed, and the pretreated wood chips are collected. The pretreated wood chips are steamed to obtain pulp; The pulp is pulped, loosened, and then paper-made to obtain paper.

6. The method for preparing chemical pulp from acacia wood using microwave-assisted hydrothermal treatment as described in claim 5, characterized in that, The cooking temperature is 150-170℃, the cooking time is 60-120 minutes, and the liquid ratio is 1:4-7.

7. The method for preparing chemical pulp from acacia wood using microwave-assisted hydrothermal treatment as described in claim 5, characterized in that, The pulp was prepared using the sulfate process, with an alkali content of 15% (calculated as Na2O), a sulfidation degree of 30%, a cooking temperature of 165℃, a heating time of 90 min, a holding time of 150 min, and a liquor ratio of 1:4.

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