Method for crystallization of erythritol

Abstract

The present invention relates to the field of crystallization and purification of erythritol, and more particularly to a method for crystallizing erythritol. The method comprises: (1) mixing an erythritol concentrate with erythritol seed crystals to obtain a mixture; (2) subjecting the mixture to pre-crystallization and cooling crystallization in the intermittent presence of an inert gas to obtain a slurry; and (3) subjecting the slurry to solid-liquid separation to obtain erythritol crystals and a mother liquor. This method eliminates the use of organic reagents, ensuring production process safety and avoiding organic reagent residues. Furthermore, it achieves a high erythritol crystallization yield within a short crystallization time, resulting in higher purity and more uniform particles of erythritol crystals. The method is simple in process, easily industrializable, low in cost, and environmentally friendly.

Description

Technical Field

[0001] The present invention relates to the field of crystallization and purification of erythritol, and in particular to a method for crystallizing erythritol. Background Art

[0002] With the global spread of chronic diseases such as obesity, diabetes, and the "three highs", "healthy intake" of sugar in the diet has become a new health issue. Among them, the development and application of low-calorie sweeteners is one of the most effective ways.

[0003] Erythritol, a natural sugar and functional sweetener, is widely used in the development of low-calorie health foods, functional foods and beverages for people with diabetes and glucose intolerance, and children's tooth cleaning products. The market prospects are very promising. Domestic erythritol production is already among the largest in the world, with an annual capacity of approximately 58,000 tons. Industrial production of erythritol primarily utilizes fermentation. After purification, the fermentation broth is evaporated and concentrated, and then cooled and crystallized to produce erythritol crystals.

[0004] Erythritol is highly soluble in water, requiring a high degree of supersaturation for crystallization. Currently, two commonly used erythritol crystallization techniques generally operate on two principles. The first involves adding an organic solvent to reduce the free water content in the crystallization solution and promote the precipitation of erythritol crystals. This technique suffers from issues such as high organic solvent consumption, increased crystallization costs, increased safety risks during the production process, and the risk of residual organic reagents. The other involves a two-step crystallization process: first, concentration crystallization. Once the concentrated crystallization mother liquor reaches a high concentration, the temperature is lowered for crystallization. For example, CN104086365B discloses a method for recycling erythritol production mother liquor to produce mixed sugar alcohol products. This method recycles excess erythritol from the erythritol crystallization mother liquor, improving erythritol utilization and overall yield. However, this method employs the traditional evaporation-concentration followed by cooling crystallization, resulting in a low single-step crystallization yield. While this process has certain advantages, it ultimately suffers from a small evaporation area and low heat transfer efficiency. Furthermore, existing erythritol crystallization methods are often limited by the initial supersaturation of the crystallization mother liquor.

[0005] Therefore, there is an urgent need to develop a method for crystallizing erythritol with a safe production process, a high crystallization yield of erythritol, more uniform erythritol crystal particles, and good industrialization prospects. Summary of the Invention

[0006] The purpose of the present invention is to overcome the above-mentioned problems existing in the prior art and provide a method for crystallizing erythritol. The method can obtain a higher crystallization yield of erythritol while ensuring the safety of the production process and avoiding the residue of organic reagents without using organic reagents. The obtained erythritol crystals have higher purity and more uniform particles. The process is simple, easy to industrialize, low cost and environmentally friendly.

[0007] In order to achieve the above object, the present invention provides a method for crystallizing erythritol, which comprises:

[0008] (1) mixing the erythritol concentrate with erythritol seed crystals to obtain a mixture;

[0009] (2) in the intermittent presence of an inert gas, subjecting the mixture to pre-crystallization and cooling crystallization to obtain a slurry;

[0010] (3) subjecting the slurry to solid-liquid separation to obtain erythritol crystals and mother liquor.

[0011] Through the above technical solution, the present invention can achieve the following beneficial effects:

[0012] 1. The method of the present invention can obtain a higher crystallization yield of erythritol within a shorter crystallization time and avoid crystal agglomeration. The obtained erythritol crystals have higher purity and more uniform particles.

[0013] 2. The method of the present invention does not use organic reagents, is safe and environmentally friendly, can avoid organic reagent residues, and is not limited by the initial supersaturation of the crystallization mother liquor. In addition, the method of the present invention is simple in process, easy to industrialize, low in cost, and has good industrialization prospects. DETAILED DESCRIPTION

[0014] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0015] The present invention provides a method for crystallizing erythritol, which comprises:

[0016] (1) mixing the erythritol concentrate with erythritol seed crystals to obtain a mixture;

[0017] (2) in the intermittent presence of an inert gas, subjecting the mixture to pre-crystallization and cooling crystallization to obtain a slurry;

[0018] (3) subjecting the slurry to solid-liquid separation to obtain erythritol crystals and mother liquor.

[0019] According to the present invention, preferably, the method for obtaining an erythritol concentrate comprises: purifying an erythritol solution to be purified to obtain a purified erythritol solution, and concentrating the purified erythritol solution to obtain an erythritol concentrate;

[0020] Wherein, the purity of the purified erythritol solution is not less than 95% by weight.

[0021] The erythritol solution to be purified can be any one of naturally extracted, enzymatically synthesized, or chemically synthesized erythritol solutions, or a mixture of two or three thereof. For example, the erythritol solution to be purified can be obtained by converting fructose via erythritol-3-epimerase catalysis.

[0022] Wherein, the purification method can be a membrane filtration purification method.

[0023] According to the present invention, in order to obtain a higher crystallization yield of erythritol in a shorter crystallization time, and to make the obtained erythritol crystals have higher purity and more uniform particles, preferably, the concentration of the erythritol concentrate is 500-700 g / L (for example, it can be 500 g / L, 510 g / L, 520 g / L, 530 g / L, 540 g / L, 550 g / L, 560 g / L, 570 g / L, 580 g / L, 590 g / L, 600 g / L, 610 g / L, 620 g / L, 630 g / L, 640 g / L, 650 g / L, 660 g / L, 670 g / L, 680 g / L, 690 g / L, 700 g / L). More preferably, the concentration of the erythritol concentrate is 550 g / L-650 g / L, more preferably 600 g / L.

[0024] It is understandable that the "purity" and "concentration" mentioned are different concepts. In actual production, the solution containing erythritol often contains other sugars or alcohols in addition to erythritol. Purity refers to the ratio of the weight of erythritol in the solution containing erythritol to the total weight of the dry matter in the solution (all sugars and alcohols in the solution); while concentration refers to the ratio of the sum of the weights of all sugars and alcohols in the solution containing erythritol to the total weight of the solution.

[0025] According to the present invention, the concentration method is not particularly limited and can be a conventional choice in the art. Preferably, the concentration method is reduced pressure concentration. It is understood that in reduced pressure concentration, the concentration pressure is generally as low as possible, but taking into account cost and ease of operation, the concentration pressure is based on the principle of being able to achieve faster concentration of the purified erythritol solution at a lower temperature.

[0026] Among them, in order to facilitate operation during the industrial scale-up process and lower the threshold for process technology scale-up, the equipment used for concentration can be single-effect, double-effect, triple-effect, or quadruple-effect concentration equipment.

[0027] According to the present invention, in order to avoid caramelization reaction caused by excessively high local temperature of erythritol during the concentration process, resulting in browning of the concentrated liquid, so that the final erythritol crystals appear yellow, preferably, the temperature during the concentration process should be controlled to be no higher than 80°C (for example, it can be 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C).

[0028] According to the present invention, in order to obtain a higher crystallization yield of erythritol in a shorter crystallization time, preferably, relative to 1L of erythritol concentrate, the amount of the erythritol seed crystals is 1-50g (for example, 1g, 5g, 10g, 20g, 30g, 40g, 50g), more preferably 10-30g, more preferably 20g.

[0029] According to the present invention, in order to obtain a higher crystallization yield of erythritol in a shorter crystallization time, and to make the obtained erythritol crystals have higher purity and more uniform particles, preferably, the temperature of the inert gas is 20-40°C (for example, it can be 20°C, 25°C, 30°C, 35°C, 40°C), and the water content is 0.5-1.5 weight% (0.5 weight%, 0.8 weight%, 1 weight%, 1.2 weight%, 1.5 weight%); more preferably, the temperature of the inert gas is 25-35°C, and the water content is 0.8-1 weight%; more preferably, the temperature of the inert gas can be 30°C, and the water content is 0.9 weight%.

[0030] In order to ensure that the inert gas is in sufficient contact with the mixture, thereby obtaining a higher crystallization yield of erythritol in a shorter crystallization time, and obtaining erythritol crystals with higher purity and more uniform particles, the inert gas is preferably introduced from the bottom of the mixture. It is understood that a gas distributor may be provided at the bottom of the mixture in order to ensure that the introduced inert gas is as dispersed and uniform as possible in contact with the mixture.

[0031] The inert gas is a gas that does not react with the mixed material. For example, the inert gas may be at least one of air, nitrogen, and carbon dioxide.

[0032] It is understood that, since the erythritol concentrate and the erythritol seed crystals have been mixed before the inert gas is introduced into the mixture, crystals will be produced in the mixture regardless of whether the inert gas is introduced into the mixture.

[0033] The inventors of the present invention have found in their research that when the inert gas as described above is introduced into the mixture, crystal agglomeration can be further avoided, and at the same time, part of the moisture in the mixture can be taken away, thereby further increasing the supersaturation of the mixture and further promoting crystallization.

[0034] According to the present invention, in order to obtain the crystallization yield of higher erythritol in a shorter crystallization time, and make the erythritol crystal purity obtained higher, particle is more uniform, preferably, the method for passing into inert gas comprises: every 5-30min (such as, can be 5min, 10min, 15min, 20min, 25min, 30min) pass into an inert gas, and keep passing into 5-30s (such as, can be 5s, 10s, 15s, 20s, 25s, 30s), repeat passing into and not passing into operation until pre-crystallization and decrease temperature crystalline end.Preferred, the method for passing into inert gas comprises: every 10-20min pass into an inert gas, and keep passing into 10-20s, repeat passing into and not passing into operation until pre-crystallization and decrease temperature crystalline end.Preferred, every 15min pass into an inert gas, and keep passing into 15s, repeat passing into and not passing into operation until pre-crystallization and decrease temperature crystalline end.

[0035] The inventors of the present invention have found in the study that, in the process of alternately passing and not passing inert gas as described above, the passing gas will push the liquid and crystal particles in the mixture to tumble, avoid agglomeration, and cause the temperature of the mixture to rise, taking away part of the moisture in the mixture. After stopping the passing of gas, the temperature will gradually fall back, which can make the supersaturation of the mixture steadily increase within a more suitable range. Therefore, the amount of crystal precipitation will steadily increase, so that the steady accumulation of erythritol can be achieved in alternating steps. Among them, it can be understood that if the amount of crystal precipitation is too large within a certain period of time, it is easy to make the crystal particle size too small and the particles are not uniform enough; if the amount of crystal precipitation is too small within a certain period of time, the crystallization yield of erythritol is too low, and the purpose of obtaining a higher crystallization yield of erythritol cannot be achieved.

[0036] According to the present invention, in order to obtain a higher crystallization yield of erythritol in a shorter crystallization time and to make the obtained erythritol crystals have higher purity and more uniform particles, preferably, the introduction rate of the inert gas is 0.5-2 L / min relative to 1 L of erythritol concentrate.

[0037] According to the present invention, in order to allow the inert gas to come into more complete contact with the mixture, thereby obtaining a higher erythritol crystallization yield in a shorter crystallization time, and making the obtained erythritol crystals of higher purity and more uniform particles, preferably, the inert gas is introduced from the bottom of the mixture. In order to allow the introduced inert gas to be dispersed as much as possible and to come into contact with the mixture as evenly as possible, a gas distributor may be provided at the bottom of the mixture.

[0038] According to the present invention, in order to obtain a higher crystallization yield of erythritol and make the obtained erythritol crystals have higher purity and more uniform particles, preferably, the total time of the pre-crystallization and cooling crystallization is 8-12h (for example, it can be 8h, 9h, 10h, 11h, 12h).

[0039] According to the present invention, in order to obtain a higher crystallization yield of erythritol, and to make the obtained erythritol crystals have a higher purity and the particles are more uniform, the conditions of the pre-crystallization include: a temperature of 20-60°C (for example, 20°C, 30°C, 40°C, 50°C, 60°C), a time of 2-4h (for example, 2h, 3h, 4h), and a stirring rate of 60-180rpm (for example, 60rpm, 80rpm, 100rpm, 120rpm, 150rpm, 180rpm). It can be understood that the temperature of the pre-crystallization is the temperature of the mixture, and the stirring rate is the stirring rate in the mixture. More preferably, the temperature of the pre-crystallization is 30-50°C.

[0040] According to the present invention, preferably, the conditions for the decrease temperature crystallization include: a cooling rate of 15-20°C / h, cooling to 5-15°C and maintaining a temperature of 5-15°C, and a stirring rate of 60-180rpm. It is understandable that there is a significant difference in temperature between pre-crystallization and decrease temperature crystallization, so it is necessary to cool the mixture. By adopting the cooling rate as described above, it is possible to gradually increase the supersaturation while avoiding excessive temperature changes, which affects the purity and particle uniformity of the erythritol crystals. It is understandable that the time for decrease temperature crystallization includes the time for cooling and the time for maintenance. Among them, the time for decrease temperature crystallization is such that the total time for pre-crystallization and decrease temperature crystallization is 8-12h, and generally decrease temperature crystallization lasts 5-8h (for example, it can be a numerical value within the numerical range formed by any two values ​​of 5h, 6h, 7h, 8h and above).

[0041] According to the present invention, the solid-liquid separation method is not particularly limited and can be a conventional choice in the art. For example, the solid-liquid separation method can be selected from at least one of filtration separation and centrifugal separation.

[0042] According to the present invention, in order to obtain erythritol crystals of higher purity, after solid-liquid separation, the method further includes: drying the obtained erythritol crystals. The drying method can be conventional in the art, for example, at least one selected from fluidized bed drying and vacuum drying.

[0043] According to the present invention, in order to further improve the yield of erythritol crystals, preferably, the method further comprises: taking a portion of the mother liquor, returning it to mix with the purified erythritol solution, and concentrating them together;

[0044] The amount of the mother liquor is such that after the mother liquor is returned and mixed with the purified erythritol solution, the purity of the obtained material is not less than 95% by weight.

[0045] According to the present invention, in order to further improve the yield of erythritol crystals, preferably, the remaining part of the mother liquor is returned to be mixed with the erythritol solution to be purified and purified together.

[0046] According to a particularly preferred embodiment of the present invention, erythritol crystallization is carried out according to the following method:

[0047] (1) Purifying the erythritol solution to be purified by a membrane filtration method to obtain a purified erythritol solution with a purity of not less than 95% by weight.

[0048] The purified erythritol solution is concentrated under reduced pressure at a temperature not higher than 80° C. to a concentration of 590-610 g / L to obtain an erythritol concentrate.

[0049] Take erythritol seed crystals, mix them with the above-mentioned erythritol concentrate (relative to 1 L of erythritol concentrate, the amount of the erythritol seed crystals is 18-22 g), and stir them so that the erythritol seed crystals are dispersed more evenly to obtain a mixture.

[0050] (2) The mixture is placed in a crystallization tank, and air is introduced from the bottom of the crystallization tank every 14-16 minutes. The air is introduced for 14-16 seconds, and the introduction and non-adherence operations are repeated until the pre-crystallization and cooling crystallization are completed. The air temperature is 30-33° C. and the water content is 0.85-0.95% by weight. The inert gas introduction rate is 1-1.4 L / min relative to 1 L of erythritol concentrate.

[0051] The pre-crystallization conditions include: a temperature of 38-42°C, a time of 3-3.5 hours, and a stirring rate of 80-120 rpm. After the pre-crystallization is completed, the crystallization is carried out by cooling. The cooling crystallization conditions include: cooling to 5-8°C at a cooling rate of 15-16°C / h, crystallizing to obtain a slurry. The cooling crystallization lasts for 5-7 hours and the stirring rate is 80-120 rpm.

[0052] (3) The slurry is separated by centrifugation to obtain a solid phase and a liquid phase, wherein the liquid phase is the mother liquor; the solid phase is vacuum dried in a vacuum drying oven to obtain erythritol crystals.

[0053] A portion of the mother liquor is returned to be mixed with the purified erythritol solution and concentrated together; wherein the amount of the mother liquor is such that the purity of the resulting material after being returned to be mixed with the purified erythritol solution is not less than 95% by weight. The remaining portion of the mother liquor is returned to be mixed with the erythritol solution to be purified and purified together.

[0054] The present invention will be described in detail below by way of examples. In the following examples:

[0055] The triple-effect concentration equipment was purchased from Zhejiang Kemei Pharmaceutical Machinery Co., Ltd.

[0056] Vacuum drying oven, model DZF-6050, purchased from Shanghai Bozheng Industrial Co., Ltd.;

[0057] Centrifugal filter, model SSC300, purchased from Yongle Machinery Equipment Manufacturing Co., Ltd.;

[0058] Example 1

[0059] For illustrating the method for crystallizing erythritol provided by the present invention

[0060] (1) The erythritol solution to be purified is purified by a membrane filtration method to obtain a purified erythritol solution with a purity of 96% by weight.

[0061] The purified erythritol solution was concentrated under reduced pressure in a triple-effect concentration device at 75° C. to a concentration of 600 g / L to obtain an erythritol concentrate.

[0062] The above 100 L of erythritol concentrate was mixed with 2 kg of erythritol seed crystals (ie, the amount of erythritol seed crystals used was 20 g relative to 1 L of erythritol concentrate), and stirred so that the erythritol seed crystals were evenly dispersed to obtain a mixture.

[0063] (2) The mixture is placed in a crystallization tank with a gas distributor at the bottom, and air is introduced from the bottom of the crystallization tank every 15 minutes and maintained for 15 seconds, and the operation of introducing and not introducing air is repeated until the pre-crystallization and cooling crystallization are completed. The air temperature is 30° C. and the water content is 0.9% by weight; the inert gas introduction rate is 1.2 L / min relative to 1 L of erythritol concentrate.

[0064] The pre-crystallization conditions included: a temperature of 40°C, a time of 3 hours, and a stirring rate of 100 rpm. After the pre-crystallization, the crystallization process proceeded to cooling crystallization. The cooling crystallization process included: cooling to 5°C at a cooling rate of 15°C / h, then maintaining the temperature at 5°C for crystallization to obtain a slurry. The cooling crystallization process lasted for 5 hours, with a stirring rate of 100 rpm.

[0065] (3) The slurry is separated by centrifugation to obtain a solid phase and a liquid phase, wherein the liquid phase is the mother liquor; the solid phase is vacuum dried in a vacuum drying oven to obtain erythritol crystals.

[0066] A portion of the mother liquor is returned to be mixed with the purified erythritol solution and concentrated together; wherein the amount of the mother liquor is such that the purity of the resulting material after being returned to be mixed with the purified erythritol solution is not less than 95% by weight. The remaining portion of the mother liquor is returned to be mixed with the erythritol solution to be purified and purified together.

[0067] Example 2

[0068] For illustrating the method for crystallizing erythritol provided by the present invention

[0069] (1) The erythritol solution to be purified is purified by a membrane filtration method to obtain a purified erythritol solution with a purity of 96% by weight.

[0070] The purified erythritol solution was concentrated under reduced pressure in a triple-effect concentration device at 70° C. to a concentration of 650 g / L to obtain an erythritol concentrate.

[0071] The above 920 L of erythritol concentrate and 9.2 kg of erythritol seed crystals were mixed (ie, with respect to 1 L of erythritol concentrate, the amount of erythritol seed crystals was 10 g), and stirred so that the erythritol seed crystals were dispersed more evenly to obtain a mixture.

[0072] (2) The mixture is placed in a crystallization tank with a gas distributor at the bottom, and air is introduced from the bottom of the crystallization tank every 10 minutes and maintained for 10 seconds, and the operation of introducing and not introducing air is repeated until the pre-crystallization and cooling crystallization are completed. The temperature of the air is 35° C. and the water content is 1% by weight; the inert gas is introduced at a rate of 2 L / min relative to 1 L of erythritol concentrate.

[0073] The pre-crystallization conditions included: a temperature of 50°C, a time of 2 hours, and a stirring rate of 50 rpm. After the pre-crystallization, cooling crystallization was performed. Cooling crystallization conditions included: cooling to 12°C at a cooling rate of 18°C / h, then maintaining the temperature at 12°C for crystallization to obtain a slurry. Cooling crystallization lasted for 8 hours, with a stirring rate of 50 rpm.

[0074] (3) The slurry is separated by centrifugation to obtain a solid phase and a liquid phase, wherein the liquid phase is the mother liquor; the solid phase is vacuum dried in a vacuum drying oven to obtain erythritol crystals.

[0075] A portion of the mother liquor is returned to be mixed with the purified erythritol solution and concentrated together; wherein the amount of the mother liquor is such that the purity of the resulting material after being returned to be mixed with the purified erythritol solution is not less than 95% by weight. The remaining portion of the mother liquor is returned to be mixed with the erythritol solution to be purified and purified together.

[0076] Example 3

[0077] For illustrating the method for crystallizing erythritol provided by the present invention

[0078] (1) The erythritol solution to be purified is purified by a membrane filtration method to obtain a purified erythritol solution with a purity of 97% by weight.

[0079] The purified erythritol solution was concentrated under reduced pressure in a triple-effect concentration device at 65° C. to a concentration of 550 g / L to obtain an erythritol concentrate.

[0080] The above 1091 L of erythritol concentrate was mixed with 32.7 kg of erythritol seed crystals (ie, the amount of erythritol seed crystals used was 30 g relative to 1 L of erythritol concentrate) and stirred to disperse the erythritol seed crystals more evenly to obtain a mixture.

[0081] (2) The mixture is placed in a crystallization tank with a gas distributor at the bottom, and air is introduced from the bottom of the crystallization tank every 20 minutes. After the introduction is maintained for 20 seconds, the introduction and non-introduction operations are repeated until the pre-crystallization and cooling crystallization are completed. The air temperature is 25° C. and the water content is 0.8% by weight. The inert gas introduction rate is 0.5 L / min relative to 1 L of erythritol concentrate.

[0082] The pre-crystallization conditions included: a temperature of 30°C, a time of 4 hours, and a stirring rate of 300 rpm. After the pre-crystallization, the crystallization was performed by cooling at a rate of 20°C / h, cooling to 15°C, and maintaining the temperature at 15°C to obtain a slurry. The cooling crystallization lasted for 8 hours, with a stirring rate of 300 rpm.

[0083] (3) The slurry is separated by centrifugation to obtain a solid phase and a liquid phase, wherein the liquid phase is the mother liquor; the solid phase is vacuum dried in a vacuum drying oven to obtain erythritol crystals.

[0084] A portion of the mother liquor is returned to be mixed with the purified erythritol solution and concentrated together; wherein the amount of the mother liquor is such that the purity of the resulting material after being returned to be mixed with the purified erythritol solution is not less than 95% by weight. The remaining portion of the mother liquor is returned to be mixed with the erythritol solution to be purified and purified together.

[0085] Example 4

[0086] For illustrating the method for crystallizing erythritol provided by the present invention

[0087] (1) The erythritol solution to be purified is purified by a membrane filtration method to obtain a purified erythritol solution with a purity of 95% by weight.

[0088] The purified erythritol solution was concentrated under reduced pressure in a triple-effect concentration device at 80° C. to a concentration of 500 g / L to obtain an erythritol concentrate.

[0089] The above 1200 L of erythritol concentrate was mixed with 60 kg of erythritol seed crystals (ie, the amount of erythritol seed crystals used was 50 g relative to 1 L of erythritol concentrate), and stirred so that the erythritol seed crystals were evenly dispersed to obtain a mixture.

[0090] (2) The mixture is placed in a crystallization tank with a gas distributor at the bottom, and air is introduced from the bottom of the crystallization tank every 30 minutes. After the introduction is maintained for 30 seconds, the introduction and non-introduction operations are repeated until the pre-crystallization and cooling crystallization are completed. The air temperature is 40° C. and the water content is 0.5% by weight. The inert gas introduction rate is 1.5 L / min relative to 1 L of erythritol concentrate.

[0091] The pre-crystallization conditions included: a temperature of 60°C, a time of 4 hours, and a stirring rate of 200 rpm. After the pre-crystallization, the crystallization process proceeded to cooling crystallization. The cooling crystallization process involved cooling the crystallization process to 10°C at a cooling rate of 15°C / h and maintaining the temperature at 10°C to produce a slurry. The cooling crystallization process lasted for 8 hours.

[0092] (3) The slurry is separated by centrifugation to obtain a solid phase and a liquid phase, wherein the liquid phase is the mother liquor; the solid phase is vacuum dried in a vacuum drying oven to obtain erythritol crystals.

[0093] A portion of the mother liquor is returned to be mixed with the purified erythritol solution and concentrated together; wherein the amount of the mother liquor is such that the purity of the resulting material after being returned to be mixed with the purified erythritol solution is not less than 95% by weight. The remaining portion of the mother liquor is returned to be mixed with the erythritol solution to be purified and purified together.

[0094] Example 5

[0095] For illustrating the method for crystallizing erythritol provided by the present invention

[0096] (1) The erythritol solution to be purified is purified by a membrane filtration method to obtain a purified erythritol solution with a purity of 95% by weight.

[0097] 6000 L of the purified erythritol solution was taken and concentrated under reduced pressure in a triple-effect concentration device at 75° C. to a concentration of 700 g / L to obtain an erythritol concentrate.

[0098] The above 857 L of erythritol concentrate and 0.857 kg of erythritol seed crystals were mixed (ie, the amount of erythritol seed crystals used was 1 g relative to 1 L of erythritol concentrate) and stirred to disperse the erythritol seed crystals more evenly to obtain a mixture.

[0099] (2) The mixture is placed in a crystallization tank with a gas distributor at the bottom, and air is introduced from the bottom of the crystallization tank every 5 minutes and maintained for 5 seconds, and the operation of introducing and not introducing air is repeated until the pre-crystallization and cooling crystallization are completed. The temperature of the air is 20° C. and the water content is 1.5% by weight; the inert gas is introduced at a rate of 0.8 L / min relative to 1 L of erythritol concentrate.

[0100] The pre-crystallization conditions included: a temperature of 20°C, a time of 3 hours, and a stirring rate of 200 rpm. After the pre-crystallization, the crystallization was performed by cooling down. The crystallization was performed by cooling down to 10°C at a cooling rate of 15°C / h and maintaining the temperature at 10°C to obtain a slurry. The cooling down crystallization lasted for 7 hours.

[0101] (3) The slurry is separated by centrifugation to obtain a solid phase and a liquid phase, wherein the liquid phase is the mother liquor; the solid phase is vacuum dried in a vacuum drying oven to obtain erythritol crystals.

[0102] A portion of the mother liquor is returned to be mixed with the purified erythritol solution and concentrated together; wherein the amount of the mother liquor is such that the purity of the resulting material after being returned to be mixed with the purified erythritol solution is not less than 95% by weight. The remaining portion of the mother liquor is returned to be mixed with the erythritol solution to be purified and purified together.

[0103] Example 6

[0104] For illustrating the method for crystallizing erythritol provided by the present invention

[0105] (1) The erythritol solution to be purified is purified by a membrane filtration method to obtain a purified erythritol solution with a purity of 95% by weight.

[0106] The purified erythritol solution was concentrated under reduced pressure in a triple-effect concentration device at 50° C. to a concentration of 700 g / L to obtain an erythritol concentrate.

[0107] 2 kg of erythritol seed crystals were mixed with the above 1000 L of erythritol concentrate (ie, the amount of the erythritol seed crystals was 2 g relative to 1 L of erythritol concentrate), and stirred so that the erythritol seed crystals were dispersed more evenly to obtain a mixture.

[0108] (2) The mixture is placed in a crystallization tank with a gas distributor at the bottom, and air is introduced from the bottom of the crystallization tank every 25 minutes for pre-crystallization. The introduction of air is maintained for 25 seconds, and the operation of introducing and not introducing air is repeated until the pre-crystallization and cooling crystallization are completed. The air temperature is 40° C. and the water content is 1.5% by weight. The inert gas is introduced at a rate of 1 L / min relative to 1 L of erythritol concentrate.

[0109] The pre-crystallization conditions included a temperature of 20°C, a time of 3 hours, and a stirring rate of 200 rpm. After the pre-crystallization, the crystallization process proceeded to cooling crystallization. The cooling crystallization process involved cooling the crystallization process to 5°C at a cooling rate of 15°C / h to produce a slurry. The cooling crystallization process lasted for 7 hours.

[0110] (3) The slurry is separated by centrifugation to obtain a solid phase and a liquid phase, wherein the liquid phase is the mother liquor; the solid phase is vacuum dried in a vacuum drying oven to obtain erythritol crystals.

[0111] A portion of the mother liquor is returned to be mixed with the purified erythritol solution and concentrated together; wherein the amount of the mother liquor is such that the purity of the resulting material after being returned to be mixed with the purified erythritol solution is not less than 95% by weight. The remaining portion of the mother liquor is returned to be mixed with the erythritol solution to be purified and purified together.

[0112] Comparative Example 1

[0113] 100 L of the purified erythritol solution obtained in Example 1 was taken and concentrated crystallized and cooled crystallized using the method in CN104086365B.

[0114] Comparative Example 2

[0115] 100 L of the purified erythritol solution obtained in Example 1 was taken and an organic solvent was added to perform crystallization using the method described in CN201210364267.X.

[0116] Comparative Example 3

[0117] Erythritol crystallization was carried out according to the method of Example 1, except that air was not introduced into the mixture.

[0118] Test Case

[0119] The purity, yield and particle uniformity of the erythritol crystals obtained in Examples 1-6 and Comparative Examples 1-3 were tested. The results are shown in Table 1.

[0120] The purity test method is as follows: prepare a 10.0 mg / mL erythritol standard solution (erythritol standard, purchased from Shanghai Aladdin Reagent Co., Ltd.), and dilute it into solutions with concentrations of 10.0 mg / mL, 8.0 mg / mL, 6.0 mg / mL, 4.0 mg / mL, 2.0 mg / mL, 1.0 mg / mL, 0.5 mg / mL, and 0.25 mg / mL. Use a high performance liquid chromatography system to measure the peak area of ​​the erythritol standard solution, and draw a standard curve with the peak area (average of 3 sets of parallel samples) as the ordinate and the solution concentration as the abscissa. The erythritol samples in Examples 1-7 and Comparative Examples 1-4 are quantitatively analyzed based on the standard curve. Chromatographic conditions were as follows: an Agilent 1260 Series HPLC system was used, including a G1311C quaternary pump, a G1316A column oven, a G1329B autosampler, and a G1236A differential refractometer. The column was a Waters sugar-Pak I column (10 μm, 6.5 mm × 300 mm). The column temperature was 80°C, the RID detection temperature was 55°C, and the mobile phase was water at a flow rate of 0.4 mL / min. All samples were filtered through a 0.45 μm microfiltration membrane before injection.

[0121] The yield is calculated as follows: the crystallization yield is calculated as follows: crystallization yield = (mass of erythritol crystals) / (volume of erythritol concentrate*concentration)*100%.

[0122] The particle uniformity is detected by using 40-mesh and 60-mesh sieves to determine the ratio of the weight of erythritol particles with a particle size range of 40-60 mesh to the total mass of erythritol crystals. The higher the ratio, the better the uniformity.

[0123] Table 1

[0124] serial number Product purity (%) Product yield (%) 40-60 mesh crystal ratio (%) Example 1 99.80 61.04 66.00 Example 2 99.73 59.75 64.71 Example 3 99.70 57.75 63.58 Example 4 99.67 55.00 62.14 Example 5 99.64 53.14 58.39 Example 6 99.52 53.00 59.15 Comparative Example 1 99.16 40.72 37.08 Comparative Example 2 99.46 48.77 18.05 Comparative Example 3 99.00 40.11 7.62

[0125] As can be seen from the results in Table 1, the purity, concentration, and uniformity of the erythritol prepared in Examples 1-6 using the technical solution of the present invention are good, among which the purity, concentration, and uniformity of the erythritol prepared in Examples 1-3 are even better. The purity, concentration, and uniformity of the erythritol prepared in Comparative Examples 1-3 are poor.

[0126] In addition, the technical solution of the present invention can avoid the use of organic reagents, making the production process safer and environmentally friendly, and avoiding organic reagent residues. Moreover, the process is simple, low-cost, and easy to industrialize, with good industrial prospects.

[0127] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as the contents disclosed by the present invention and fall within the scope of protection of the present invention.

Claims

1. A method for crystallizing erythritol, characterized in that: The method includes: (1) purifying an erythritol solution to be purified to obtain a purified erythritol solution, and concentrating the purified erythritol solution to obtain an erythritol concentrate; wherein the erythritol solution to be purified is any one of erythritol solutions obtained by natural extraction, enzymatic synthesis, or chemical synthesis, or a mixture of two or three of the above, the purity of the purified erythritol solution is not less than 95% by weight, and the concentration of the erythritol concentrate is 500-700 g / L; mixing the erythritol concentrate with erythritol seed crystals to obtain a mixture, wherein the amount of the erythritol seed crystals used is 1-50 g relative to 1 L of the erythritol concentrate; (2) in the intermittent presence of an inert gas, the mixture is subjected to pre-crystallization and cooling crystallization to obtain a slurry, wherein the inert gas is a gas that does not react with the mixture and is selected from one of air, nitrogen and carbon dioxide; the method of introducing the inert gas comprises: introducing the inert gas once every 5-30 minutes, and maintaining the introduction for 5-30 seconds, repeating the operation of introducing and not introducing the inert gas until the pre-crystallization and cooling crystallization are completed, the total time of the pre-crystallization and cooling crystallization is 8-12 hours, the conditions of the pre-crystallization comprise: a temperature of 20-60°C, a time of 2-4 hours, and a stirring rate of 60-180 rpm, and the conditions of the cooling crystallization comprise: a cooling rate of 15-20°C / h, cooling to 5-15°C and maintaining the temperature at 5-15°C, and a stirring rate of 60-180 rpm; (3) The slurry is subjected to solid-liquid separation to obtain erythritol crystals and mother liquor.

2. The method according to claim 1, wherein The concentration of the erythritol concentrate is 550-650 g / L.

3. The method according to claim 1, wherein Relative to 1 L of erythritol concentrated solution, the amount of the erythritol seed crystals used is 10-30 g.

4. The method according to any one of claims 1 to 3, wherein: The temperature of the inert gas is 20-40° C., and the water content is 0.5-1.5% by weight.

5. The method according to any one of claims 1 to 3, wherein: The temperature of the inert gas is 25-35° C., and the water content is 0.8-1% by weight.

6. The method according to any one of claims 1 to 3, wherein: The method of introducing the inert gas includes: introducing the inert gas once every 10-20 minutes, maintaining the introduction for 10-20 seconds, and repeating the operation of introducing and not introducing the inert gas until the pre-crystallization and the cooling crystallization are completed.

7. The method according to any one of claims 1 to 3, wherein: The inert gas introduction rate is 0.5-2 L / min relative to 1 L of erythritol concentrate.

8. The method according to any one of claims 1 to 3, wherein: The temperature of the pre-crystallization is 30-50°C.

9. The method according to claim 1, wherein: The method further comprises: taking a portion of the mother liquor, returning the mother liquor to mix with the purified erythritol solution, and concentrating the mixture together; The amount of the mother liquor is such that after the mother liquor is returned and mixed with the purified erythritol solution, the purity of the obtained material is not less than 95% by weight.

10. The method according to claim 9, wherein: The remaining mother liquor is returned to be mixed with the erythritol solution to be purified and purified together.