阅读说明：本技术 一种α型L-谷氨酸晶种的制备方法 (Preparation method of alpha-type L-glutamic acid seed crystal ) 是由 张方坤 杜康 单宝明 徐啟蕾 于 2020-12-09 设计创作，主要内容包括：本发明公开了一种α型L-谷氨酸晶种的制备方法,属于工业结晶过程高纯度晶种的制备技术领域,所述制备方法包括以下步骤：将L-谷氨酸晶体溶于溶剂中得到L-谷氨酸溶液(所述L-谷氨酸溶液浓度为40-50g/L),以所述L-谷氨酸溶液为原料,在搅拌状态下降温至室温(搅拌速率以溶液不发生沉淀为宜),析出晶体,待溶液由透明变成乳浊液状,结晶结束,迅速将溶液进行固液分离,将分离得到的固体洗涤、干燥,即得到α型L-谷氨酸晶种。本发明制备的α型L-谷氨酸晶型稳定,晶种均匀,晶种质量高,纯度高,晶型纯度高达100％。(The invention discloses a preparation method of alpha-type L-glutamic acid seed crystal, belonging to the technical field of preparation of high-purity seed crystal in industrial crystallization process, and the preparation method comprises the following steps: dissolving L-glutamic acid crystals in a solvent to obtain an L-glutamic acid solution (the concentration of the L-glutamic acid solution is 40-50g/L), taking the L-glutamic acid solution as a raw material, cooling to room temperature under a stirring state (the stirring speed is proper to prevent the solution from precipitating), separating out the crystals, quickly carrying out solid-liquid separation on the solution after the solution is changed into an emulsion from a transparent state, washing and drying the separated solid to obtain the alpha-type L-glutamic acid seed crystal. The alpha-L-glutamic acid prepared by the invention has stable crystal form, uniform crystal seeds, high crystal seed quality and high purity, and the crystal form purity reaches 100%.)

1. A preparation method of alpha-type L-glutamic acid seed crystal is characterized by comprising the following steps: dissolving L-glutamic acid crystals in a solvent to obtain an L-glutamic acid solution, taking the L-glutamic acid solution as a raw material, cooling to room temperature under a stirring state, precipitating crystals, quickly performing solid-liquid separation on the solution after the solution is changed into an emulsion from a transparent state, and washing and drying the separated solid to obtain the alpha-type L-glutamic acid crystal seed.

2. The method for preparing alpha-type L-glutamic acid seed crystal according to claim 1, wherein the L-glutamic acid crystal is in amorphous form and has a purity of not less than 99%.

3. The method of claim 1, wherein the solvent is distilled or deionized water.

4. The method for producing α -form L-glutamic acid seed crystals according to claim 1, wherein the L-glutamic acid solution is heated to 75 to 85 ℃ and kept for 30 to 120 min.

5. The method of claim 1, wherein the L-glutamic acid solution is cooled to 15-25 ℃ at a rate of 0.8 ℃/min-2 ℃/min.

6. The method of claim 1, wherein the solution is left for 0-6min after it is changed from transparent to emulsion.

7. The method of claim 1, wherein the isolated solid is washed with ethanol.

8. The method for preparing alpha-form L-glutamic acid seed crystals according to claim 7, wherein the purity of ethanol is not less than 95%.

9. The method for preparing alpha-form L-glutamic acid seed crystals according to claim 1, wherein the drying temperature is 35 to 55 ℃ and the drying time is 1 to 10 hours.

Technical Field

The invention relates to the technical field of preparation of high-purity seed crystals in industrial crystallization processes, in particular to a preparation method of alpha-type L-glutamic acid seed crystals.

Background

Glutamic acid of chemical formula N₅H₉NO₄It is a colorless crystal, has delicate flavor, is slightly soluble in water, and is hardly soluble in ethanol and acetone. The glutamic acid is divided into L-glutamic acid,D-glutamic acid and DL-glutamic acid, L-glutamic acid being a major constituent of proteins, are useful in the food industry and the pharmaceutical industry. L-glutamic acid is classified into alpha-type L-glutamic acid and beta-type L-glutamic acid. alpha-L-glutamic acid is a metastable crystal form, and in the preparation process of the crystal seed, due to the defects of equipment and technical methods, if the variable control of the crystallization process is improper, the crystal can be transformed into the beta crystal form, so that the high-purity alpha-L-glutamic acid crystal seed is difficult to obtain.

The Chinese patent with the application number of CN201710852566.0 and the name of 'a preparation method of L-glutamic acid' adopts the following crystallization steps: preparing monosodium glutamate solution by taking monosodium glutamate as a raw material, adding sulfuric acid into the monosodium glutamate solution in batches to prepare crystal slurry, and carrying out centrifugation or suction filtration and drying treatment on the crystal slurry to obtain the L-glutamic acid. The preparation method of the L-glutamic acid has great defects: the addition of sulfuric acid can generate acidic waste liquid in the crystallization process, which is harmful to the environment. ② the crystallization time is long and the production efficiency is low. Thirdly, the produced L-glutamic acid has large particle size distribution range, low purity and poor product quality. And fourthly, the alpha-type L-glutamic acid or the beta-type L-glutamic acid cannot be determined to be crystallized. Chinese patent CN200880016235.2 segmented a method for preparing alpha-form L-glutamic acid crystals by adding acid to glutamate solution so that pH is lowered to isoelectric point of glutamic acid. However, it is difficult to obtain high purity (chemical purity and crystal form purity) crystals of α -form L-glutamic acid by the above method. Some documents obtain the alpha-form L-glutamic acid crystals by adding seed crystals, but the purity of the seed crystals is crucial to obtain a single crystal form product. At present, no method for obtaining high-purity alpha-type L-glutamic acid seed crystals is available.

Disclosure of Invention

The invention aims to provide a preparation method of alpha-type L-glutamic acid seed crystals, which aims to solve the problems in the prior art and improve the purity of alpha-type L-glutamic acid.

In order to achieve the purpose, the invention provides the following scheme:

the invention provides a preparation method of alpha-type L-glutamic acid seed crystal, which comprises the following steps: dissolving L-glutamic acid crystals in a solvent to obtain an L-glutamic acid solution (the concentration of the L-glutamic acid solution is 40-50g/L), taking the L-glutamic acid solution as a raw material, cooling to room temperature under a stirring state (the stirring speed is proper to prevent the solution from precipitating), separating out the crystals, quickly carrying out solid-liquid separation on the solution after the solution is changed into an emulsion from a transparent state, washing and drying the separated solid to obtain the alpha-type L-glutamic acid seed crystal.

As a further improvement of the invention, the L-glutamic acid crystal has no crystal form requirement, and the purity is more than or equal to 99 percent.

As a further improvement of the invention, the solvent is distilled water or deionized water.

As a further improvement of the invention, the L-glutamic acid solution is rapidly heated to 75-85 ℃ at the speed of 1 ℃/min and is kept for 30-120min, so that the L-glutamic acid crystal is completely dissolved in the solvent.

As a further improvement of the invention, the L-glutamic acid solution is cooled to 15-25 ℃ at the speed of 0.8-2 ℃/min.

As a further improvement of the invention, the solution is kept for 0-6min after the solution is changed from transparent to emulsion. Crystal transformation can occur when the residence time is too long, and a beta crystal form or a mixed crystal form is generated.

As a further improvement of the invention, the solid obtained by separation is washed with ethanol.

As a further improvement of the invention, the purity of the ethanol is more than or equal to 95 percent.

As a further improvement of the invention, the drying temperature is 35-55 ℃, and the drying time is 1-10 h.

The invention discloses the following technical effects:

the invention obtains the high-purity alpha-type L-glutamic acid crystal seed by controlling the operating conditions (temperature, cooling rate, solution concentration and other variables) of the crystallization process, spontaneously nucleating and crystallizing the high-purity metastable crystal form in the cooling crystallization process and controlling the crystallization time to avoid the crystal transformation phenomenon. The L-glutamic acid is insoluble in ethanol, the water on the surface of the crystal can be removed by washing with the ethanol, the crystal is prevented from being dissolved, transformed into the crystal and even adhered in the drying process due to overhigh temperature, and the crystal washed by the ethanol is dried again, so that the dispersibility can be improved. The preparation method of the alpha-type L-glutamic acid crystal seed provided by the invention has the characteristic of high efficiency, the prepared crystal form is stable, the crystal seed is uniform, the crystal seed quality is high, the purity is high, and the crystal form purity is up to 100%.

The invention can adopt batch small batch production or continuous crystallization production, has simple and flexible operation, stable crystal form and high purity of the crystal product, can be used as a preparation method of the high-purity crystal seed of the L-glutamic acid, and improves the crystallization efficiency and the product quality.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without inventive exercise.

FIG. 1 is an electron microscope photograph of seed crystals of alpha-form L-glutamic acid prepared in example 1;

FIG. 2 is an XRD pattern of seed crystals of alpha-form L-glutamic acid prepared in example 1;

FIG. 3 is an electron microscope photograph of seed crystals of alpha-form L-glutamic acid prepared in example 2;

FIG. 4 is an XRD pattern of seed crystals of alpha-form L-glutamic acid prepared in example 2;

FIG. 5 is an electron microscope photograph of seed crystals of alpha-form L-glutamic acid prepared in example 3;

FIG. 6 is an XRD pattern of seeds of alpha-form L-glutamic acid prepared in example 3;

FIG. 7 is an electron microscope photograph of seed crystals of alpha-form L-glutamic acid prepared in example 4;

FIG. 8 is an electron microscope photograph of seed crystals of alpha-form L-glutamic acid prepared in example 5;

FIG. 9 is an electron microscope photograph of L-glutamic acid seed crystals prepared in comparative example 1;

FIG. 10 is an XRD pattern of L-glutamic acid seed crystal prepared in comparative example 1;

FIG. 11 is an electron microscope photograph of L-glutamic acid seed crystals prepared in comparative example 2;

FIG. 12 is an XRD pattern of L-glutamic acid seed crystals prepared in comparative example 2;

FIG. 13 is an electron microscope photograph of L-glutamic acid seed crystals prepared in comparative example 3;

FIG. 14 is an XRD pattern of L-glutamic acid seed crystals prepared in comparative example 3;

FIG. 15 is an electron microscope photograph of L-glutamic acid seed crystals prepared in comparative example 4.

Detailed Description

Reference will now be made in detail to various exemplary embodiments of the invention, the detailed description should not be construed as limiting the invention but as a more detailed description of certain aspects, features and embodiments of the invention.

It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. Further, for numerical ranges in this disclosure, it is understood that each intervening value, between the upper and lower limit of that range, is also specifically disclosed. Every smaller range between any stated value or intervening value in a stated range and any other stated or intervening value in a stated range is encompassed within the invention. The upper and lower limits of these smaller ranges may independently be included or excluded in the range.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference herein for the purpose of disclosing and describing the methods and/or materials associated with the documents. In case of conflict with any incorporated document, the present specification will control.

It will be apparent to those skilled in the art that various modifications and variations can be made in the specific embodiments of the present disclosure without departing from the scope or spirit of the disclosure. Other embodiments will be apparent to those skilled in the art from consideration of the specification. The description and examples are intended to be illustrative only.

As used herein, the terms "comprising," "including," "having," "containing," and the like are open-ended terms that mean including, but not limited to.

The purity of the crystal form is the crystal form purity, not the chemical purity, and only one crystal form is the crystal form purity of 100%.

Example 1

Adding 45g of L-glutamic acid into 1L of water solution at 45 ℃ to prepare supersaturated solution, rapidly heating to 75 ℃, and keeping for 60 min; then, cooling to 15 ℃ at the speed of 1.5 ℃/min, stirring at the speed of 250r/min, standing for 5min after the solution is changed into emulsion from transparent, and finishing crystallization; thereafter, the crystallization solution was filtered with a filter, and the filtered solid crystals were added to 95% ethanol and washed 2 times; and finally, drying the washed L-glutamic acid crystal for 2 hours at the temperature of 45 ℃ to obtain the alpha-type L-glutamic acid crystal seed.

The electron microscope picture and XRD picture of the alpha-form L-glutamic acid crystal prepared in this example are shown in figure 1 and figure 2, and the crystal obtained from figure 2 can be determined to be alpha-form L-glutamic acid crystal seed crystal, and no peak of beta-form crystal is seen, so that the crystal only has alpha-form crystal form. The crystal form purity is 100%, and the crystal form of the alpha-type L-glutamic acid crystal seed is regular and uniform in size as can be seen from figure 2.

Example 2

Adding 180g of L-glutamic acid into 4L of aqueous solution at the temperature of 35 ℃ to prepare supersaturated solution, heating to 80 ℃, and keeping for 1h to fully dissolve crystals, wherein the stirring speed is 300 r/min; then, cooling to 18 ℃ at the speed of 2 ℃/min, maintaining the temperature until the solution is changed into emulsion from transparency, and staying for 6min after the cooling is finished; then filtering out solid L-glutamic acid, adding the solid L-glutamic acid into 99% ethanol for washing for 3 times, and finally drying the washed L-glutamic acid crystal at 40 ℃ to obtain the dried alpha-type L-glutamic acid crystal seed. An electron micrograph of the α -form L-glutamic acid seed crystals prepared in this example is shown in FIG. 3. Fig. 4 is an XRD pattern of the α -form L-glutamic acid seed crystal prepared in this example, from fig. 4, it can be confirmed that the prepared α -form L-glutamic acid seed crystal is obtained, and no peak of the β -form crystal is seen, and it can be confirmed that the crystal is only the α -form crystal.

Example 3

Adding 48g of L-glutamic acid crude product into 1L of water solution at the temperature of 45 ℃ to prepare supersaturated solution, heating to 85 ℃, and maintaining for 40 min; then, cooling to 20 ℃ at the speed of 1.5 ℃/min, maintaining the temperature until the solution is changed into emulsion from transparency, and staying for 3min after the cooling is finished; then filtering out solid L-glutamic acid, adding the solid L-glutamic acid into 99% ethanol for washing for 2 times, and finally drying the washed L-glutamic acid crystal at 35 ℃ to obtain the dried alpha-type L-glutamic acid crystal seed. An electron microscope image of the α -form L-glutamic acid seed crystal prepared in this example is shown in fig. 5, an XRD image of the α -form L-glutamic acid seed crystal is shown in fig. 6, and from fig. 6, it can be confirmed that the prepared α -form L-glutamic acid seed crystal is an α -form L-glutamic acid seed crystal, and no peak of the β -form crystal is seen, and it can be confirmed that the crystal has only the α -form.

Example 4

Adding 450g of L-glutamic acid into 10L of aqueous solution at the temperature of 45 ℃ to prepare supersaturated solution, rapidly heating to 85 ℃, and keeping for 120 min; then, cooling to 25 ℃ at the speed of 1 ℃/min, stirring at the speed of 150r/min, standing for 6min after the solution is changed into emulsion from transparent, and finishing crystallization; thereafter, the crystallization solution was filtered with a filter, and the filtered solid crystals were added to 95% ethanol and washed 2 times; and finally, drying the washed L-glutamic acid crystal for 8 hours at the temperature of 55 ℃ to obtain the alpha-type L-glutamic acid crystal seed.

An electron micrograph of the α -form L-glutamic acid crystals prepared in this example is shown in FIG. 7.

Example 5

Adding 420g of L-glutamic acid into 10L of aqueous solution at the temperature of 45 ℃ to prepare supersaturated solution, rapidly heating to 75 ℃, and keeping for 90 min; then, cooling to 20 ℃ at the speed of 0.8 ℃/min, stirring at the speed of 250r/min, standing for 3min after the solution is changed into emulsion from transparent, and finishing crystallization; thereafter, the crystallization solution was filtered with a filter, and the filtered solid crystals were added to 95% ethanol and washed 2 times; and finally, drying the washed L-glutamic acid crystal for 1h at the temperature of 50 ℃ to obtain the alpha-type L-glutamic acid crystal seed.

An electron micrograph of the α -form L-glutamic acid crystals prepared in this example is shown in FIG. 8.

Comparative example 1

Adding 45g of L-glutamic acid into 1L of water solution at 45 ℃ to prepare supersaturated solution, rapidly heating to 100 ℃, and keeping for 120 min; then, cooling to 25 ℃ at the speed of 2 ℃/min, stirring at the speed of 250r/min, standing for 30min after the solution is changed into emulsion from transparent, and finishing crystallization; thereafter, the crystallization solution was filtered with a filter, and the filtered solid crystals were added to 95% ethanol and washed 2 times; and finally, drying the washed L-glutamic acid crystal for 8 hours at the temperature of 55 ℃ to obtain the L-glutamic acid seed crystal. The electron micrograph of the L-glutamic acid seed crystal obtained in this comparative example is shown in FIG. 9, the XRD pattern is shown in FIG. 10, and it is understood from FIG. 10 that the alpha form accounts for 98%.

Comparative example 2

Adding 45g of L-glutamic acid into 1L of water solution at 45 ℃ to prepare supersaturated solution, rapidly heating to 85 ℃, and keeping for 120 min; then, cooling to 35 ℃ at the speed of 0.1 ℃/min, stirring at the speed of 250r/min, standing for 50min after the solution is changed into emulsion from transparent, and finishing crystallization; thereafter, the crystallization solution was filtered with a filter, and the filtered solid crystals were added to 95% ethanol and washed 2 times; finally, the washed L-glutamic acid crystals were dried at 55 ℃ for 8 hours to obtain mixed crystals of alpha-form and beta-form L-glutamic acid, and the electron micrograph and XRD pattern of the crystals of L-glutamic acid obtained in this comparative example are shown in FIG. 11 and FIG. 12, respectively, showing that the alpha-form accounts for 95%.

Comparative example 3

Adding 600g of L-glutamic acid into 1L of water solution at 60 ℃ to prepare supersaturated solution, rapidly heating to 85 ℃, and keeping for 120 min; then, cooling to 25 ℃ at the speed of 2 ℃/min, stirring at the speed of 250r/min, standing for 6min after the solution is changed into emulsion from transparent, and finishing crystallization; thereafter, the crystallization solution was filtered with a filter, and the filtered solid crystals were added to 95% ethanol and washed 2 times; and finally, drying the washed L-glutamic acid crystal for 8 hours at the temperature of 55 ℃ to obtain the beta-type L-glutamic acid crystal seed.

The electron micrograph of the L-glutamic acid seed crystal obtained in this comparative example is shown in FIG. 13, the XRD pattern is shown in FIG. 14, and it is understood from FIG. 14 that all the L-glutamic acids are in the beta form.

Comparative example 4

Adding 450g of L-glutamic acid into 10L of aqueous solution at the temperature of 45 ℃ to prepare supersaturated solution, rapidly heating to 85 ℃, and keeping for 120 min; then, cooling to 45 ℃ at the speed of 0.2 ℃/min, stirring at the speed of 250r/min, standing for 2 hours after the solution is changed into emulsion from transparent, and finishing crystallization; thereafter, the crystallization solution was filtered with a filter, and the filtered solid crystals were added to 95% ethanol and washed 2 times; and finally, drying the washed L-glutamic acid crystal for 8 hours at the temperature of 55 ℃ to obtain the beta-type L-glutamic acid crystal seed. An electron micrograph of the β type L-glutamic acid seed crystal obtained in this comparative example is shown in FIG. 15.

The above-described embodiments are merely illustrative of the preferred embodiments of the present invention, and do not limit the scope of the present invention, and various modifications and improvements of the technical solutions of the present invention can be made by those skilled in the art without departing from the spirit of the present invention, and the technical solutions of the present invention are within the scope of the present invention defined by the claims.