CN113372572B - A method for recycling solid organic acid to separate lignin - Google Patents

Abstract

The invention relates to a method for recycling solid organic acid to separate lignin. The lignocellulosic raw material is mixed with a solid organic acid aqueous solution for heating reaction, and the obtained first filtrate is diluted with an anti-solvent to obtain a separated mother liquor and lignin. The separated mother liquor is cooled and recrystallized, and the recovered solid organic acid is used to prepare the solid organic acid aqueous solution for recycling. The method of recycling solid organic acid to separate lignin according to the present invention can not only separate and obtain high-value lignin products, but also make the lignin separation rate ≥ 90%, the DLS size is 226-231nm, and the Zeta potential is stable at -38-- 44mV, organic reagents can also be recycled, the recovery cost is low, the environmental pollution is small, the separation cost is greatly reduced, and it is convenient for large-scale promotion and use, and the inventor has further studied the suitable recycling times of solid organic acids.

Description

A method for recycling solid organic acid to separate lignin

technical field

The invention relates to the technical field of biomass chemical industry, relates to lignin separation and purification, and in particular to a method for recycling solid organic acid to separate lignin.

Background technique

Lignin is one of the three major components in plant cell walls and widely exists in vascular plants. Lignin has the advantages of being natural, renewable, biodegradable, and non-toxic, and is regarded as an important alternative raw material for petrochemical resources. In my country, with the rapid development of renewable energy industries such as papermaking industry and fuel ethanol, lignin is often discharged or burned as a by-product of pulping and papermaking waste liquid and biorefining, which not only seriously pollutes the environment, but also It is a great waste of resources.

The effective separation of lignin through biomass refining is an effective way for high-value utilization of lignin. Pulping-oriented lignin separation methods include caustic soda method, sulfate method, formic acid method, etc., which usually need to be carried out under severe reaction conditions, and lignin β-O-4 content is generally low, and the reactivity is weak; emerging sugar-oriented Advanced lignin separation methods such as weak acid, weak base, organic solvent treatment, etc., due to mild conditions, the lignin removal rate is generally low, which will also limit its high-value conversion. Therefore, the development of simple, green and efficient lignin separation methods has become a current research hotspot.

At present, the prior art generally adopts a cooking method to separate lignin. For example, CN108086028A discloses a production method of solvent lignin. The specific steps are as follows: pretreat the plant fiber raw material with an organic acid or an aqueous solution of an organic acid; The fiber raw material is cooked; after cooking, the solid-liquid is separated to obtain the cooking liquid and plant fiber; the cooking liquid is pumped into the evaporation and concentration equipment for negative pressure evaporation and concentration, and the value of the pressure P satisfies 0.7×10 ⁵ Pa≤P≤1×10 ⁵ Pa, concentration temperature is 65～200 ℃, and the degree of concentration is to concentrate until the total mass of the concentrated solution is 5～300% of the absolute dry raw material weight, stop the concentration, collect the recovered organic acid solution and concentrated solution; add distilled water in the concentrated solution, Stir well, let stand, and filter, and the obtained solid precipitate is solvent lignin.

CN105274894A discloses a method for metal-catalyzed organic acid separation of lignocellulose components. Lignocellulose raw materials are put into a cooking system composed of organic acids and metal catalysts for cooking; after the cooking is completed, the metal catalyst is recovered and solid-liquid separation , the solid is washed with organic acid solution and water to obtain pulp; the cooking waste liquid and pickling waste liquid are mixed and then evaporated and concentrated, and the steam is condensed and then distilled again to recover organic acid and furfural; water washing waste liquid is added to the evaporated concentrated liquid Precipitation, solid-liquid separation, the solid is washed with water and dried to obtain lignin, the liquid is concentrated by evaporation and dried to obtain oligosaccharides and monosaccharides, which is more suitable for the component separation of wood and non-wood fiber raw materials.

However, in the prior art, the cooking method is used to separate lignin, which not only has the disadvantages of high energy consumption and cumbersome operation, but also wastes a lot of organic reagents and increases the cost of raw materials, so it is not suitable for large-scale promotion and use. Therefore, in order to solve the problems of low lignin separation yield and high cost of chemical reagent recovery, it is urgent to develop a method for recycling solid organic acids to separate lignin, which can not only separate high-value lignin products, but also make lignin separation more efficient. The efficiency is ≥90%, the DLS size is 225-230nm, and the Zeta potential is stable at -38--44mV. Organic reagents can also be recycled, with low recycling costs and less environmental pollution, which greatly reduces the separation cost and facilitates large-scale promotion and use.

Contents of the invention

In view of the problems existing in the prior art, the present invention provides a method for recycling solid organic acid to separate lignin, which can not only separate and obtain high-value lignin products, but also make the lignin separation yield ≥ 90%, and the DLS size is 226 ~231nm, the Zeta potential is stable at -38 ~ -44mV, organic reagents can also be recycled, the recovery cost is low, the environmental pollution is small, the separation cost is greatly reduced, and it is convenient for large-scale promotion and use, and the inventor has further studied the suitable solid organic acid of recycling times.

For reaching this purpose, the present invention adopts following technical scheme:

The object of the present invention is to provide a method for recycling solid organic acid to separate lignin, said method comprising the steps of:

(1) The lignocellulosic raw material is mixed with a solid organic acid aqueous solution for heating reaction, and the first filtrate and solids are obtained through solid-liquid separation for the first time;

(2) diluting the first filtrate described in step (1) with an anti-solvent, and obtaining the separated mother liquor and lignin through solid-liquid separation for the second time;

(3) cooling and recrystallizing the separated mother liquor described in step (2), and obtaining a recovered solid organic acid through solid-liquid separation for the third time, and using the recovered solid organic acid to prepare the solid organic acid described in step (1) The aqueous solution is recycled.

The method of recycling solid organic acid to separate lignin in the present invention can not only separate and obtain high-value lignin products, but also make the lignin separation rate ≥ 90%, the DLS size is 226-231nm, and the Zeta potential is stable at -38-- 44mV, organic reagents can also be recycled, the recovery cost is low, the environmental pollution is small, the separation cost is greatly reduced, and it is convenient for large-scale promotion and use, and the inventor has further studied the suitable recycling times of solid organic acids.

As a preferred technical solution of the present invention, the lignocellulosic raw material in step (1) includes any one or a combination of at least two of wood, straw or bamboo, and a typical but non-limiting example of the combination is: wood and straw The combination of straw and bamboo, or the combination of wood and bamboo, etc.

As a preferred technical solution of the present invention, the solid organic acid in the solid organic acid aqueous solution described in step (1) includes any one or at least two of maleic acid, crotonic acid, benzenesulfonic acid or anthranilic acid. Typical but non-limiting examples of such combinations are: the combination of maleic acid and crotonic acid, the combination of crotonic acid and benzenesulfonic acid, the combination of benzenesulfonic acid and anthranilic acid, or the combination of maleic acid and Combinations of sulfanilic acid, etc.

As a preferred technical solution of the present invention, the mass concentration of the solid organic acid aqueous solution in step (1) is 30 to 95wt.%, such as 30wt.%, 35wt.%, 45wt.%, 50wt.%, 60wt.%, 70wt. .%, 75wt.%, 85wt.% or 95wt.%, etc., but not limited to the listed values, other unlisted values within the range of values are also applicable.

As a preferred technical solution of the present invention, the mass ratio of the lignocellulosic raw material to the solid organic acid aqueous solution in step (1) is 1:(5-40), such as 1:5, 1:10, 1:15, 1:20 , 1:25, 1:30, 1:35 or 1:40, etc., but not limited to the listed values, other unlisted values within the range are also applicable.

As a preferred technical solution of the present invention, the temperature of the heating reaction in step (1) is 60-120°C, such as 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 100°C °C, 105 °C, 110 °C, 115 °C, or 120 °C, etc., but not limited to the listed values, and other unlisted values within the range of values are also applicable.

Preferably, the heating reaction time in step (1) is 10 to 120 min, such as 10 min, 20 min, 30 min, 40 min, 50 min, 60 min, 70 min, 80 min, 90 min, 100 min, 110 min or 120 min, etc., but not limited to the listed The numerical value of , other unlisted numerical values in this numerical range are also applicable.

Preferably, the first solid-liquid separation in step (1) is suction filtration.

As a preferred technical solution of the present invention, the anti-solvent in the anti-solvent dilution described in step (2) includes water.

It should be noted that the anti-solvent dilution in the present invention refers to the process of adding anti-solvent to the first filtrate.

Preferably, the mass ratio of the anti-solvent in the anti-solvent dilution described in step (2) to the first filtrate is 1:(1-4), such as 1:1, 1:1.5, 1:2, 1:2.5 , 1:3, 1:3.5 or 1:4, etc., but not limited to the listed values, other unlisted values within the range of values are also applicable.

Preferably, the temperature of the anti-solvent in the anti-solvent dilution described in step (2) is 20-30°C, such as 20°C, 21°C, 22°C, 23°C, 25°C, 26°C, 27°C, 28°C or 30°C etc., but not limited to the listed values, other unlisted values within this range are also applicable.

It is worth noting that the first filtrate in step (1) does not need to be cooled down, and the anti-solvent with a temperature of 20-30 ° C can be directly added to it, and the anti-solvent can be diluted at room temperature, which can completely reach The purpose of the basic precipitation of lignin.

Preferably, the second solid-liquid separation in step (2) includes centrifugation.

It is worth noting that the volume of solids in the first solid-liquid separation is relatively large, and the purpose of separation can be achieved by simple suction filtration; the DLS size of the solid (lignin) in the second solid-liquid separation is nano-scale, The effect of centrifugation is the best; the particle size of the solid (solid organic acid) in the third solid-liquid separation is relatively large, and the separation effect can be achieved by suction filtration.

As a preferred technical solution of the present invention, the initial temperature of cooling recrystallization in step (3) is 20-30°C, 21°C, 22°C, 23°C, 25°C, 26°C, 27°C, 28°C or 30°C, etc. , but not limited to the listed values, other unlisted values within this range are also applicable.

Preferably, the end temperature of cooling recrystallization in step (3) is 0-10°C, such as 0°C, 1°C, 2°C, 4°C, 5°C, 6°C, 7°C, 9°C or 10°C, etc., However, it is not limited to the listed values, and other unlisted values within the range of values are also applicable.

Preferably, the holding time for cooling recrystallization in step (3) is 20-24h, such as 20h, 20.5h, 21h, 21.5h, 22h, 22.5h, 23h, 23.5h or 24h, etc., but not limited to the listed The numerical value of , other unlisted numerical values in this numerical range are also applicable.

It is worth noting that the holding time for cooling recrystallization in step (3) of the present invention refers to the time maintained after reaching the terminal temperature of cooling recrystallization.

As a preferred technical solution of the present invention, the number of times of recycling in step (3) is 1 to 10 times, such as 1 time, 3 times, 5 times, 7 times, 9 times or 10 times, etc., but not limited to the listed The numerical value of , other unlisted numerical values within this numerical range are also applicable, preferably 1 to 5 times.

It is worth noting that the inventor has found through many experiments and studies that although the recovery-type solid organic acid is used to prepare the solid organic acid aqueous solution required for the next round, it will not affect the physicochemical properties and yield of the lignin product, but Recycled solid organic acids will inevitably be doped with impurities produced by further degradation such as glucose, xylose, furfural, formic acid, acetic acid, etc., thereby reducing the recovery rate of recycled solid organic acids, considering recycling costs and energy consumption , the inventor preferably recycles 1 to 5 times.

As a preferred technical solution of the present invention, the method comprises the steps of:

(1) According to the mass ratio of 1: (5 ~ 40), the lignocellulosic raw material is mixed with a solid organic acid aqueous solution with a mass concentration of 30 ~ 95wt.%, and the heating reaction is carried out at 60 ~ 120 ° C for 10 ~ 120 minutes. Filter to obtain the first filtrate and solids; wherein, the lignocellulosic raw material includes any one or a combination of at least two of wood, straw or bamboo; the solid organic acid in the solid organic acid aqueous solution includes maleic acid, Any one or a combination of at least two of crotonic acid, benzenesulfonic acid or anthranilic acid;

(2) adding water to the first filtrate described in step (1) at a temperature of 20 to 30°C for antisolvent dilution, the mass ratio of water to the first filtrate is 1: (1 to 4), obtained through centrifugation Separation of mother liquor and lignin;

(3) cooling and recrystallizing the separated mother liquor in step (2), the initial temperature of the cooling recrystallization is 20-30°C, the end temperature of the cooling recrystallization is 0-10°C, and the holding time is 20-24h , the recovery type solid organic acid is obtained through the third solid-liquid separation, and the recovery type solid organic acid is used to prepare the solid organic acid aqueous solution in step (1) for 1 to 10 times of recycling.

Compared with the prior art solutions, the present invention has at least the following beneficial effects:

The method of recycling solid organic acid to separate lignin in the present invention can not only separate and obtain high-value lignin products, but also make the lignin separation rate ≥ 90%, the DLS size is 226-231nm, and the Zeta potential is stable at -38-- 44mV, organic reagents can also be recycled, the recovery cost is low, the environmental pollution is small, the separation cost is greatly reduced, and it is convenient for large-scale promotion and use, and the inventor has further studied the suitable recycling times of solid organic acids.

Description of drawings

Fig. 1 is the morphology of the lignin obtained by the recycling of benzenesulfonic acid described in Example 1 and the lignocellulosic raw material reaction separation;

Fig. 2 is the appearance of lignin obtained by recycling benzenesulfonic acid described in Example 1 and reacting with lignocellulosic raw materials for 10 times.

detailed description

The technical solutions of the present invention will be further described below in conjunction with the accompanying drawings and through specific implementation methods.

For better illustrating the present invention, facilitate understanding technical scheme of the present invention, typical but non-limiting embodiment of the present invention is as follows:

Example 1

This embodiment provides a method for recycling solid organic acid to separate lignin, said method comprising the following steps:

(1) According to the mass ratio of 1:10, 1g of lignocellulosic raw material and 10g of benzenesulfonic acid aqueous solution with a mass concentration of 80wt.% are mixed, and the heating reaction is carried out at 80°C for 20min, and the first filtrate and solids are obtained by suction filtration ; Wherein, the lignocellulosic raw material is ground wood powder;

(2) adding water to the first filtrate described in step (1) at a temperature of 25° C. for anti-solvent dilution, the mass ratio of water to the first filtrate is 1:3, and centrifuging to obtain the separated mother liquor and lignin;

(3) Cooling and recrystallizing the separated mother liquor described in step (2), the initial temperature of the cooling and recrystallization is 25°C, the end point temperature of the cooling and recrystallization is 5°C, the holding time is 24h, after the third solidification Liquid separation obtains recovery type benzenesulfonic acid, weighs after described recovery type benzenesulfonic acid is dried, calculates the recovery rate, then prepares the benzenesulfonic acid aqueous solution described in step (1) together with fresh benzenesulfonic acid and recycles, According to the above steps, a total of 10 times of recycling.

Example 2

This embodiment provides a method for recycling solid organic acid to separate lignin, said method comprising the following steps:

(1) Mix 1g lignocellulosic raw material and 40g mass concentration of 50wt.% maleic acid aqueous solution according to the mass ratio of 1:40, carry out heating reaction for 120min at 100°C, obtain the first filtrate and solids through suction filtration ; Wherein, the lignocellulosic raw material is ground wood powder;

(2) adding water at a temperature of 20° C. to the first filtrate in step (1) for anti-solvent dilution, the mass ratio of water to the first filtrate is 1:1, and centrifuging to obtain the separated mother liquor and lignin;

(3) Cooling and recrystallizing the separated mother liquor described in step (2), the initial temperature of the cooling and recrystallization is 20°C, the end point temperature of the cooling and recrystallization is 0°C, the holding time is 24h, after the third solidification Liquid separation obtains reclaimed maleic acid, weighs after described reclaimed maleic acid is dried, calculates the recovery rate, then prepares the maleic acid aqueous solution described in step (1) together with fresh maleic acid and recycles, According to the above steps, a total of 10 times of recycling.

Example 3

This embodiment provides a method for recycling solid organic acid to separate lignin, said method comprising the following steps:

(1) According to the mass ratio of 1:25, 1g lignocellulosic raw material and 25g mass concentration are mixed with 30wt.% anthranilic acid aqueous solution, carry out the heating reaction of 90min at 120 ℃, obtain the first filtrate and the first filtrate through suction filtration Solid matter; Wherein, described lignocellulosic raw material is the bamboo powder after grinding;

(2) adding water to the first filtrate described in step (1) at a temperature of 30° C. for anti-solvent dilution, the mass ratio of water to the first filtrate is 1:2, and centrifuging to obtain the separated mother liquor and lignin;

(3) Cooling and recrystallizing the separated mother liquor described in step (2), the initial temperature of the cooling and recrystallization is 30°C, the end point temperature of the cooling and recrystallization is 10°C, the holding time is 24h, after the third solidification liquid separation to obtain reclaimed anthranilic acid, weigh the reclaimed anthranilic acid after drying, calculate the recovery rate, and then prepare the anthranilic acid described in step (1) together with fresh anthranilic acid The aqueous solution of benzenesulfonic acid is recycled, and the above-mentioned steps are recycled 10 times.

In the methods described in the above-mentioned Examples 1-3, the solid organic acid recovery rate calculated under different recycling times is shown in Table 1; it is worth noting that the solid organic acid recovery rate under each recycling is calculated according to the following formula: Solid organic acid recovery rate = dry mass of recovered solid organic acid/mass of solid organic acid in solid organic acid aqueous solution × 100%.

Table 1

Cycle times 1 time 2 times 3 times 4 times 5 times 6 times 7 times 8 times 9 times 10 times Embodiment 1 (benzenesulfonic acid) 97% 92% 88% 81% 75% 71% 67% 62% 58% 52% Embodiment 2 (maleic acid) 98% 96% 95% 93% 88% 86% 83% 80% 76% 70% Embodiment 3 (anthranilic acid) 96% 94% 90% 86% 85% 83% 80% 74% 72% 67%

As can be seen from Table 1, under the same recycling number of times, the recovery rate of maleic acid corresponding to embodiment 2 is higher; after recycling 10 times, the recovery rate of maleic acid corresponding to embodiment 2 is 70%, And the solid organic acid containing sulfonic acid group, that is, anthranilic acid and benzenesulfonic acid, the corresponding recovery rate is relatively low, after recycling 10 times, the recovery rate reduces to 67% and 52% respectively; After being used for 5 times, the recovery rate of solid organic acid corresponding to Examples 1-3 is all above 75%, but as the number of cycles increases, the recovery rate of solid organic acid all decreases. Considering comprehensively the recovery cost and energy consumption, the preferred cycle The number of times of use is 1 to 5 times.

The lignin obtained under different recycling times in the method described in Example 1 above was characterized as follows, lignin separation yield, DLS size, Zeta potential and molecular weight. The specific characterization results are shown in Table 2.

Table 2

As can be seen from Table 2, the benzenesulfonic acid that embodiment 1 adopts is in the process of recycling 10 times, and the lignin separation yield is all above 90%, and the dynamic light scattering (DLS) size and Zeta of the lignin that separation obtains The potentials were kept at 226~231nm and –38~–44mV, respectively, and the weight-average molecular weight and number-average molecular weight were also kept at about 3000 and 1500, indicating that the recycling of benzenesulfonic acid will not affect the quality of the separated lignin, including Size, surface properties and molecular weight etc. In addition, Figure 1 shows the morphology of lignin separated by benzenesulfonic acid recycling once and reacted with lignocellulosic raw materials, and Figure 2 shows the lignin separated by benzenesulfonic acid recycled 10 times and reacted with lignocellulosic raw materials Comparing Figure 1 with Figure 2, it can be seen intuitively that the morphology of the two is basically the same, and the size is similar, indicating that the recycling of benzenesulfonic acid will not affect the morphology of the separated lignin.

Comparative example 1

This comparative example provides a method for separating lignin, except that the terminal temperature of cooling recrystallization described in step (3) in Example 2 is replaced by 15°C from 0°C, other conditions are exactly the same as in Example 2. The first recovery rate calculated was only 57%, and no recycling was carried out.

Comparative example 2

This comparative example provides a method for separating lignin, except that the terminal temperature of cooling recrystallization described in step (3) in Example 2 is replaced by -5°C from 0°C, other conditions are exactly the same as in Example 2. The recovered maleic acid obtained by visual inspection is yellow, indicating that it is doped with more impurities, and the purity of the recovered maleic acid is not up to the standard, and has not been recycled.

Comparative example 3

This comparative example provides a method for separating lignin, except that the holding time described in step (3) in Example 2 is replaced by 12h from 24h, other conditions are exactly the same as in Example 2. The first recovery rate calculated was only 62%, and no recycling was performed.

To sum up, the method of recycling solid organic acid to separate lignin according to the present invention can not only separate and obtain high-value lignin products, but also make the lignin separation yield ≥ 90%, the DLS size is 226-231nm, and the Zeta potential is stable At -38 ~ -44mV, organic reagents can also be recycled, with low recycling costs and less environmental pollution, which greatly reduces separation costs and facilitates large-scale promotion and use. The inventors further studied the appropriate recycling times of solid organic acids.

The applicant declares that the present invention illustrates the detailed structural features of the present invention through the above-mentioned embodiments, but the present invention is not limited to the above-mentioned detailed structural features, that is, it does not mean that the present invention must rely on the above-mentioned detailed structural features to be implemented. Those skilled in the art should understand that any improvement to the present invention, the equivalent replacement of selected components in the present invention, the addition of auxiliary components, the selection of specific methods, etc., all fall within the scope of protection and disclosure of the present invention.

The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention. These simple modifications All belong to the protection scope of the present invention.

In addition, it should be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable way if there is no contradiction. The combination method will not be described separately.

In addition, various combinations of different embodiments of the present invention can also be combined arbitrarily, as long as they do not violate the idea of the present invention, they should also be regarded as the disclosed content of the present invention.

Claims (11)

1. a method for recycling solid organic acid to separate lignin, characterized in that, the method may further comprise the steps: (1) The lignocellulosic raw material is mixed with a solid organic acid aqueous solution for heating reaction, and the first filtrate and solids are obtained through solid-liquid separation for the first time; (2) adding the first filtrate described in step (1) into water at a temperature of 20 to 30° C. for antisolvent dilution, the mass ratio of water to the first filtrate is 1: (1 to 4), and after the second Solid-liquid separation to obtain separated mother liquor and lignin; (3) cooling and recrystallizing the separated mother liquor in step (2), the initial temperature of the cooling recrystallization is 20-30°C, the end temperature of the cooling recrystallization is 0-10°C, and the holding time is 20-24h , the recovered solid organic acid is obtained through solid-liquid separation for the third time, and the recovered solid organic acid is used to prepare the solid organic acid aqueous solution in step (1) for recycling. 2. The method according to claim 1, characterized in that the lignocellulosic raw material in step (1) comprises any one or a combination of at least two of wood, straw or bamboo. 3. method according to claim 1, is characterized in that, the solid organic acid in the described solid organic acid aqueous solution of step (1) comprises any in maleic acid, crotonic acid, benzenesulfonic acid or anthranilic acid One or a combination of at least two. 4. The method according to claim 1, characterized in that the mass concentration of the solid organic acid aqueous solution in step (1) is 30-95wt.%. 5. The method according to claim 4, characterized in that, the mass ratio of lignocellulosic raw material and solid organic acid aqueous solution in step (1) is 1:(5～40). 6. The method according to claim 1, characterized in that the temperature of the heating reaction in step (1) is 60-120° C.; the time is 10-120 min. 7. The method according to claim 1, characterized in that the first solid-liquid separation in step (1) is suction filtration. 8. The method according to claim 1, characterized in that the second solid-liquid separation in step (2) comprises centrifugal separation. 9. The method according to claim 1, characterized in that the number of times of recycling in step (3) is 1 to 10 times. 10. The method according to claim 9, characterized in that the number of times of recycling in step (3) is 1 to 5 times. 11. The method according to claim 1, characterized in that the method comprises the steps of: (1) According to the mass ratio of 1: (5 ~ 40), the lignocellulosic raw material is mixed with a solid organic acid aqueous solution with a mass concentration of 30 ~ 95wt.%, and the heating reaction is carried out at 60 ~ 120 ° C for 10 ~ 120 min. Filter to obtain the first filtrate and solids; wherein, the lignocellulosic raw material includes any one or a combination of at least two of wood, straw or bamboo; the solid organic acid in the solid organic acid aqueous solution includes maleic acid, Any one or a combination of at least two of crotonic acid, benzenesulfonic acid or anthranilic acid; (2) adding water to the first filtrate described in step (1) at a temperature of 20 to 30° C. for antisolvent dilution, the mass ratio of water to the first filtrate is 1: (1 to 4), obtained through centrifugation Separation of mother liquor and lignin; (3) cooling and recrystallizing the separated mother liquor in step (2), the initial temperature of the cooling recrystallization is 20-30°C, the end point temperature of the cooling recrystallization is 0-10°C, and the holding time is 20-24h , the recovery type solid organic acid is obtained through the third solid-liquid separation, and the recovery type solid organic acid is used to prepare the solid organic acid aqueous solution in step (1) for 1 to 10 times of recycling.

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