Preparation method of ammonium adipate crystal

Abstract

The invention relates to the technical field of chemical synthesis, in particular to a preparation method of ammonium adipate. The method comprises the following steps: dissolving adipic acid in a solvent to form an adipic acid solution, introducing ammonia gas into the adipic acid solution, heating, and reacting to generate crude ammonium adipate slurry; adding a mixed auxiliary coolant composed of hydrogen peroxide and ethanol into the ammonium adipate crude product slurry, and uniformly stirring to obtain a mixed slurry; the mixed slurry is cooled and crystallized, solid-liquid separation is performed after crystals are separated out, and solids are ammonium adipate wet bases; drying the wet base to obtain a finished product. By adding a mixed auxiliary coolant in a cooling crystallization link, the polarity of the solution is changed, the solubility of ammonium adipate is reduced, and crystallization is promoted to form crystals with larger particle sizes; the strong volatility of the mixed auxiliary coolant can accelerate drying, shorten time, avoid cracking of crystals during drying, increase the proportion of large-particle-size crystals, prolong the anti-caking period of the product, provide convenience for subsequent feeding and dissolving, and is suitable for industrial production.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of chemical synthesis, in particular to a preparation method of ammonium adipate crystals. BACKGROUND

[0002] Ammonium adipate, chemical formula is , is an important chemical raw material and intermediate generated by neutralization reaction of adipic acid and ammonia. Due to its unique chemical properties, it is widely used in many industrial fields. In the polymer material industry, it is one of the important precursors for the production of nylon 66; in the textile, plastic, coating and other industries, it can be used as an additive or pH regulator; the demand in the field of electronics, chemical reagents and other special fields is also increasing.

[0003] In the prior art, ammonium adipate crystals are usually produced by evaporation crystallization or cooling crystallization in industry. That is, after neutralization reaction of adipic acid and ammonia (or liquid ammonia), the obtained ammonium adipate solution is concentrated, crystallized, centrifuged and dried to obtain the final product. However, the ammonium adipate crystals prepared by the existing conventional method generally have the following technical defects: (1) the crystal size is small and uneven: the nucleation and growth process of the crystal is difficult to effectively control in the existing process, resulting in that the average particle size of the obtained crystal is small, and there are a large number of fine powders in the product, and the proportion of fine particles is too large. (2) easy to physically clump: due to the large specific surface area and high surface energy of the fine crystal particles in the product, combined with the hygroscopicity of ammonium adipate, the crystal particles are prone to hygroscopic and recrystallization during packaging and storage, thereby causing serious physical clumping. This not only affects the appearance of the product, but also brings great inconvenience to subsequent use. (3) poor performance: the flowability of the clumped product is very poor, and it is difficult to achieve accurate and smooth conveying during feeding, which is easy to block the equipment. At the same time, the dense block will significantly prolong the time required for its dissolution in water, reduce the production efficiency, and cannot meet the process requirements of modern continuous and efficient production of chemical industry.

[0004] Therefore, it is urgent to develop a preparation method of ammonium adipate which can effectively control the crystal morphology. SUMMARY

[0005] In order to solve the above technical problems, the present application provides a novel preparation method of ammonium adipate crystals, which should be able to prepare ammonium adipate crystals with larger particle size, more uniform crystal particle size, more concentrated size range and better flowability, thereby fundamentally overcoming the shortcomings of existing products such as easy clumping, difficult feeding and slow dissolution, and meeting the higher requirements of industrial production and application.

[0006] In one aspect, the present application provides a preparation method of ammonium adipate crystals, comprising the following steps:

[0007] (1) Dissolve adipic acid in a solvent to form an adipic acid solution, pass ammonia gas into the adipic acid solution, heat, and react to form an ammonium adipate crude product slurry;

[0008] (2) Add a mixed auxiliary coolant composed of hydrogen peroxide and ethanol to the ammonium adipate crude product slurry, stir and mix uniformly to obtain a mixed slurry;

[0009] (3) Cool and crystallize the mixed slurry to precipitate crystals, and separate the solid from the liquid, with the solid being ammonium adipate wet base and the liquid being ammonium adipate mother liquor;

[0010] (4) Dry the ammonium adipate wet base to obtain ammonium adipate finished product.

[0011] The present application is directed to a process for preparing ammonium adipate crystals from adipic acid and ammonia gas through acid-base neutralization reaction, and proposes an optimized cooling crystallization scheme. Before the ammonium adipate solution enters the cooling crystallization process, a mixed auxiliary coolant composed of hydrogen peroxide and ethanol is added and stirred uniformly, and the crystal optimization is achieved by controlling the crystallization process. On the one hand, both hydrogen peroxide and ethanol have good water solubility, and the mixed system formed after their addition can significantly change the polarity of the original aqueous solution, directly weakening the solubility of ammonium adipate in the "water-hydrogen peroxide-ethanol" mixed solvent, thereby effectively enhancing the cooling crystallization effect and promoting the formation of larger particle size ammonium adipate crystals. On the other hand, hydrogen peroxide and ethanol have strong volatility, which can accelerate the removal of water and volatile components during the subsequent crystal drying process, reducing the drying time from 40-60 minutes in the prior art to 30-40 minutes, greatly improving the drying efficiency and shortening the drying time, while avoiding the cracking of ammonium adipate during drying, further increasing the proportion of large particle size crystals. Ultimately, through this process optimization, not only can the anti-caking period of the packaged ammonium adipate product be extended, but also the feeding operation and crystal dissolution link in subsequent production can be facilitated.

[0012] Further, the amount of the mixed auxiliary coolant added in step (2) is 1-2 wt% of the ammonium adipate crude product slurry. The mixed auxiliary coolant needs to be uniformly dispersed in the slurry system to reduce the solution polarity in cooperation with water, reduce the solubility of ammonium adipate, and provide a suitable supersaturation environment for crystal growth. If the amount is less than 1 wt%, the effective component of the auxiliary coolant in the system is insufficient, and it is difficult to fully change the overall polarity of the solution, resulting in limited increase in the solution supersaturation, which cannot provide enough driving force for crystal growth, and thus the auxiliary cooling crystallization effect is poor, the crystal size does not increase significantly, and it is difficult to achieve the purpose of delaying product caking. If the amount of the auxiliary coolant is more than 2 wt%, the local heat transfer rate will increase rapidly due to the difference in physical properties between the auxiliary coolant and the slurry, causing the local temperature of the solution to drop rapidly. This local temperature drop will destroy the stability of the system supersaturation, resulting in a significant difference in crystal growth rate in different regions. Some regions have a large number of fine nuclei due to a rapid increase in supersaturation, while some regions have slow crystal growth due to insufficient supersaturation, resulting in uneven crystal size, which not only affects product quality, but also increases the difficulty of controlling the crystallization process. The total amount of the mixed auxiliary coolant is set to 1-2 wt% of the slurry, which can not only fully change the polarity of the solution by providing the required supersaturation for crystal growth, achieving the auxiliary cooling crystallization effect and increasing the crystal size, but also avoid rapid local temperature drop due to excessive addition, ensuring uniform temperature drop and stable supersaturation of the system, thereby ensuring uniform crystal growth and achieving efficient and controllable cooling crystallization process and stable product quality. Specifically, the total amount of the mixed auxiliary coolant is 1 wt%, 1.1 wt%, 1.2 wt%, 1.3 wt%, 1.4 wt%, 1.5 wt%, 1.6 wt%, 1.7 wt%, 1.8 wt%, 1.9 wt%, 2.0 wt% of the ammonium adipate crude product slurry, or a range consisting of any two of these values. Preferably, the total amount of the mixed auxiliary coolant is 1-1.5 wt% of the ammonium adipate crude product slurry.

[0013] In the mixed auxiliary coolant, ethanol is used for cooling, and hydrogen peroxide is used to effectively inhibit the esterification reaction between ethanol and adipic acid, while removing pigments and impurities in the solution.

[0014] Further, the concentration of the hydrogen peroxide is 7-20%; the hydrogen peroxide is miscible with ethanol, and the hydrogen peroxide and the ethanol can synergistically reduce the polarity of the solution and the solubility of the ammonium adipate to improve the crystallization effect. The inventors have found through a large number of studies that if the concentration of the hydrogen peroxide is less than 7%, the effective component is insufficient, and it is difficult to form a strong enough polar synergistic effect to assist crystallization; and the hydrogen peroxide is easily decomposed by heat, and the higher the concentration, the faster the decomposition. If the concentration of the hydrogen peroxide is more than 20%, the heat of the reaction will cause a large amount of loss of the effective component, and it is necessary to additionally increase the amount of the hydrogen peroxide, which not only increases the cost, but also the oxygen generated by the decomposition can interfere with the stability of the crystallization system. The concentration of the hydrogen peroxide is selected to be 7-20%, which can not only guarantee the synergistic effect of the hydrogen peroxide and the ethanol on the crystallization, but also reduce the loss caused by the heating decomposition, and achieve a balance between the effect and the cost. Specifically, the concentration of the hydrogen peroxide is 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, or a range formed by any two of these values. Preferably, the concentration of the hydrogen peroxide is 10-15%.

[0015] Further, the concentration of the ethanol is more than 95%.

[0016] Further, the mass ratio of the hydrogen peroxide to the ethanol is 1:(1-1.5). In this ratio range, the decomposition amount of the hydrogen peroxide can be avoided from increasing and the cost from rising when heated, and the polarity of the system can be prevented from decreasing too quickly due to the high proportion of the ethanol, which can cause the crystals to precipitate rapidly and have a small particle size. The overall properties of the mixed auxiliary coolant can be ensured to be stable, and the mixed auxiliary coolant can be easily dispersed uniformly after being mixed with the slurry, so that the controllability of the cooling and crystallization process can be further improved.

[0017] Further, the molar ratio of the adipic acid to the ammonia in step (1) is 1:(2-2.2). The reaction of the adipic acid and the ammonia can be ensured to be complete, and the adipic amine can be maximally converted; the incomplete reaction can be avoided, and the residual adipic acid can be prevented from affecting the crystallization of the adipic acid and the purity thereof, and the excessive ammonia can be prevented from causing the system to be too alkaline and causing a side reaction; and the subsequent cooling and crystallization can be ensured to provide a guarantee for preparing high-purity crystals.

[0018] Further, the reaction temperature in step (1) is 60-75°C. The reaction temperature in this temperature range can provide sufficient activation energy for the neutralization reaction, can avoid a slow reaction rate caused by a too low temperature, and can simultaneously prevent the ammonia from being volatilized and the utilization rate of the raw materials from being reduced caused by a too high temperature; and the quality of the generated crude adipic amine can be ensured to be stable.

[0019] Further, the reaction end point of step (1) is pH 7.3-7.6. The reaction end point is indicated by pH, which can accurately control the neutralization reaction degree of adipic acid and ammonia, ensure that adipic acid and ammonia are fully reacted according to the stoichiometric amount, avoid the problem that the crude product of ammonium adipate contains residual unreacted raw materials due to excess acid or excess base, and improve the product purity; and can make the reaction system stable in the pH range where the hydrolysis of ammonium adipate is not easy to occur, reduce the generation of impurities, and at the same time provide a crude slurry with uniform properties for the subsequent addition of a mixed auxiliary coolant and the cooling crystallization process, thereby ensuring the stability and crystallization effect of the subsequent process.

[0020] Further, the stirring time in step (2) is 10-30 min.

[0021] Further, the solvent of the adipic acid solution in step (1) is water or saturated ammonium adipate mother liquor at room temperature. The saturated mother liquor can inhibit the extraction and precipitation of ammonium adipate during the reaction, ensuring the smooth progress of the reaction.

[0022] Further, the mass content of ammonium adipate in the mother liquor in step (3) is 20-40%.

[0023] Further, the ammonium adipate mother liquor separated in step (3) is recycled and used as the solvent of the adipic acid solution in step (1), reducing wastewater discharge.

[0024] Further, the ammonium adipate product is packaged, and the packaging specification is 20-24 kg / bag, and the packaged bags are coded and stored in the warehouse.

[0025] Further, the wet base is dried by a boiling bed in step (4), improving the drying efficiency.

[0026] Compared with the prior art, the present application has the following beneficial effects:

[0027] (1) The present application adds a mixed auxiliary coolant composed of hydrogen peroxide and ethanol, which can significantly increase the average particle size of the crystals and make the crystal particles more uniform and the size range more concentrated by reducing the polarity of the solution and the solubility of ammonium adipate, reducing the proportion of fine powder, significantly prolonging the anti-caking period of the product after packaging, and avoiding the problems of difficult accurate feeding and slow dissolution speed in the subsequent use process.

[0028] (2) Reducing production cost: on the one hand, the present application prolongs the crystal caking time by precisely controlling the amount of mixed auxiliary coolant, the mass ratio of hydrogen peroxide to ethanol and other parameters, reduces raw material waste and invalid consumption, and reduces production cost; on the other hand, the crystallization mother liquor is recycled and used for the preparation of adipic acid solution, which greatly reduces the wastewater discharge amount and reduces the environmental protection treatment cost.

[0029] (3) Improve product quality consistency: the present application through the optimization process of "neutralization reaction-addition of mixed auxiliary coolant-cooling crystallization", and through the accurate control of pH value indicating reaction endpoint, stirring time and other parameters, ensures that each batch of crude product slurry is uniform in nature, avoiding the problem that the crystal nucleation and growth process is difficult to control in the existing process; at the same time, the mixed auxiliary coolant is easy to disperse uniformly with the slurry, and will not cause local temperature drop or composition imbalance, improving the controllability of the cooling crystallization process, and ensuring the stability and repeatability of the quality of different batches of products. DETAILED DESCRIPTION

[0030] The technical solutions in the embodiments of the present application will be clearly and completely described below in combination with the embodiments in the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the present application.

[0031] Embodiment 1

[0032] A preparation method of ammonium adipate, comprising the following steps:

[0033] (1) 1800 kg of adipic acid is dissolved in 3300 kg of water, heated to 40℃, and prepared into an adipic acid solution with a concentration of 35%; the prepared adipic acid solution is added into a reaction kettle for heating, so that the temperature in the reaction kettle is increased to 65℃, and ammonia gas is introduced into the reaction kettle, the molar ratio of ammonia gas to adipic acid being 2:1, stirring, and the pH value of the solution is monitored in real time by an online pH meter, when the pH value is stabilized at 7.3, the ammonia gas is stopped, and the stirring is continued for 10 min to obtain ammonium adipate crude product slurry;

[0034] (2) 30.6 kg of hydrogen peroxide with a concentration of 15% and 45.9 kg of anhydrous ethanol with a concentration of 95% are uniformly mixed in a container to prepare 76.5 kg of mixed auxiliary coolant; the mixed auxiliary coolant is slowly and uniformly added into the ammonium adipate crude product slurry, and after the addition is completed, the stirring is continued for 15 min to obtain a mixed slurry; the addition amount of the mixed auxiliary coolant is 1.5 wt% of the ammonium adipate crude product slurry;

[0035] (3) the mixed slurry is transferred into a cooling crystallization kettle, and ammonium adipate crystals are crystallized and separated from the slurry; a centrifugal machine is used for solid-liquid separation, and solid ammonium adipate wet base and liquid ammonium adipate mother liquor are obtained after the separation;

[0036] (4) the ammonium adipate wet base is transferred into a boiling bed for drying to obtain ammonium adipate finished product.

[0037] Embodiment 2

[0038] The preparation method of this example is basically the same as that of Example 1, except that:

[0039] In step (2), hydrogen peroxide with a concentration of 7% and ethanol with a concentration of 95% are mixed into a mixed auxiliary coolant at a solution mass ratio of 1:1.

[0040] The addition amount of the mixed auxiliary coolant is 1wt% of the ammonium adipate crude product slurry.

[0041] Example 3

[0042] The preparation method of this example is basically the same as that of Example 1, except that:

[0043] In step (2), hydrogen peroxide with a concentration of 7% and ethanol with a concentration of 95% are mixed into a mixed auxiliary coolant at a solution mass ratio of 1:1.

[0044] The addition amount of the mixed auxiliary coolant is 1wt% of the ammonium adipate crude product slurry.

[0045] Example 4

[0046] The preparation method of this example is basically the same as that of Example 1, except that:

[0047] The addition amount of the mixed auxiliary coolant is 0.8wt% of the ammonium adipate crude product slurry.

[0048] Example 5

[0049] The preparation method of this example is basically the same as that of Example 1, except that:

[0050] The addition amount of the mixed auxiliary coolant is 2.1wt% of the ammonium adipate crude product slurry.

[0051] Example 6

[0052] The preparation method of this example is basically the same as that of Example 1, except that: in step (2), the mass ratio of hydrogen peroxide to ethanol is 1:0.9.

[0053] Example 7

[0054] The preparation method of this example is basically the same as that of Example 1, except that: in step (2), the mass ratio of hydrogen peroxide to ethanol is 1:1.6.

[0055] Example 8

[0056] The preparation method of this example is basically the same as that of Example 1, except that: in step (2), the concentration of hydrogen peroxide is 5%.

[0057] Example 9

[0058] The preparation method of this example is basically the same as that of Example 1, except that the concentration of hydrogen peroxide in step (2) is 22%.

[0059] Example 10

[0060] The preparation method of this example is basically the same as that of Example 1, except that adipic acid is dissolved in an ammonium adipate mother liquor with a mass content of 20% in step (1).

[0061] Comparative Example 1

[0062] The preparation method of this example is basically the same as that of Example 1, except that no mixed auxiliary coolant is added during crystallization, i.e., step (2) is not included.

[0063] Comparative Example 2

[0064] The preparation method of this example is basically the same as that of Example 1, except that only 1.5wt% of hydrogen peroxide with a concentration of 15% is added to the ammonium adipate crude product slurry during crystallization.

[0065] Comparative Example 3

[0066] The preparation method of this example is basically the same as that of Example 1, except that only 1.5wt% of ethanol with a concentration of 95% is added to the ammonium adipate crude product slurry during crystallization.

[0067] The quality of the finished ammonium adipate products obtained in Examples 1-10 and Comparative Examples 1-3 was analyzed, as shown in Table 1:

[0068] Table 1

[0069]

[0070] As can be seen from Examples 1-10 in Table 1, by adding a certain proportion of a mixed auxiliary coolant composed of hydrogen peroxide and ethanol to the ammonium adipate crude product slurry, the crystallization process is synergistically adjusted, significantly improving the crystal particle size, uniformity, and anti-caking performance.

[0071] As can be seen from the comparison of Examples 1-3 and Examples 4-5, the addition amount of the mixed auxiliary coolant is lower than or higher than the preferred range, resulting in a wider crystal particle size distribution, an increased fine powder ratio, and a shortened anti-caking period. This indicates that when the addition amount is insufficient, it is difficult to sufficiently change the solution polarity and supersaturation, and the crystal growth driving force is insufficient; while excessive addition can easily cause rapid local temperature drop, which destroys the stability of the crystal and affects the uniform growth of the crystal. As can be seen from the comparison of Examples 1-3 and Examples 6-7, when the mass ratio of hydrogen peroxide to ethanol deviates from the preferred range, the crystal particle size uniformity decreases and the anti-caking performance is weakened. When the ethanol ratio is too high, the rapid precipitation of the crystal is easily caused by the sudden drop in the polarity of the system, which is not conducive to the formation of large particle size crystals; while a high hydrogen peroxide ratio can cause the loss of effective components due to heating decomposition, which weakens the synergistic regulation effect. As can be seen from the comparison of Examples 1-3 and Examples 8-9, when the concentration of hydrogen peroxide is lower than or higher than the preferred range, the crystal quality and anti-caking performance are both decreased. When the concentration of hydrogen peroxide is too low, it is difficult to effectively inhibit the esterification reaction and play a synergistic regulation role; while a high concentration can intensify the thermal decomposition, which not only increases the cost, but also can interfere with the stability of the crystallization system.

[0072] As can be seen from the comparison of Example 1 and Example 10, using ammonium adipate mother liquor as the solvent, compared with using water as the solvent, the performance of the ammonium adipate crystals prepared is improved, which indicates that the reuse of ammonium adipate mother liquor not only realizes resource recycling and reduces emissions, but also helps to optimize the crystallization environment and further improve the quality of the crystalline crystals and the anti-caking performance.

[0073] As can be seen from the comparison of Example 1 and Comparative Examples 1-3, without adding the mixed auxiliary coolant or only adding hydrogen peroxide or only adding ethanol as a crystallization promoter during the crystallization of ammonium adipate, the quality and anti-caking performance of the ammonium adipate crystals after crystallization are significantly reduced, which fully illustrates that the addition of the mixed auxiliary coolant plays a key role in increasing the crystal particle size, improving the uniformity of the crystal and delaying caking, and the components hydrogen peroxide and ethanol have a significant synergistic effect, and the use of either component alone cannot achieve the comprehensive technical effect achieved by the present application.

[0074] The above further describes the present application with specific examples, but it should be understood that the specific description herein should not be construed as limiting the spirit and scope of the present application, and various modifications made by those skilled in the art after reading the above description are within the scope of the present application.

Claims

1. A method for preparing ammonium adipate crystals, characterized in that, Includes the following steps: (1) Dissolve adipic acid in a solvent to form an adipic acid solution, introduce ammonia gas into the adipic acid solution, heat, and react to produce crude ammonium adipicate slurry; (2) Add a mixed auxiliary coolant consisting of hydrogen peroxide and ethanol to the crude ammonium adipate slurry, stir and mix evenly to obtain a mixed slurry; (3) Cool the mixed slurry to crystallize, precipitate crystals, and separate the solid and liquid. The solid is ammonium adipate wet base, and the liquid is ammonium adipate mother liquor. (4) The ammonium adipate wet base is dried to obtain the ammonium adipate finished product.

2. The method for preparing ammonium adipate crystals according to claim 1, characterized in that, In step (2), the amount of mixed auxiliary coolant added is 1-2 wt% of the crude ammonium adipate slurry.

3. The method for preparing ammonium adipate crystals according to claim 1, characterized in that, In step (2), the concentration of hydrogen peroxide is 7-20%, and the concentration of ethanol is 95% or higher.

4. The method for preparing ammonium adipate crystals according to claim 3, characterized in that, In step (2), the mass ratio of hydrogen peroxide to ethanol is 1:(1~1.5).

5. The method for preparing ammonium adipate crystals according to claim 1, characterized in that, In step (1), the molar ratio of adipic acid to ammonia is 1:(2~2.2).

6. The method for preparing ammonium adipate crystals according to claim 1, characterized in that, The reaction temperature in step (1) is 60~75℃.

7. The method for preparing ammonium adipate crystals according to claim 1, characterized in that, The reaction endpoint of step (1) is a pH value of 7.3 to 7.

6.

8. The method for preparing ammonium adipate crystals according to claim 1, characterized in that, In step (1), the solvent is water or ammonium adipate mother liquor saturated at room temperature.

9. The method for preparing ammonium adipate crystals according to claim 1, characterized in that, In step (3), the mass content of ammonium adipate in the ammonium adipate mother liquor is 20-40%.

10. The method for preparing ammonium adipate crystals according to claim 1, characterized in that, The ammonium adipate mother liquor separated in step (3) is recycled and reused as the solvent in step (1).

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