Process for the preparation of monohydrated lactitol and its use

Abstract

The application provides a preparation method of monohydrate lactitol and application thereof, and relates to the technical field of lactitol preparation.The crystallization process of the preparation method adopts intermittent material taking, and is a method capable of realizing continuous evaporation and cooling crystallization.Further, in the process of continuous production, the method does not need to repeatedly add crystal seeds, and can reduce the preparation step of crystal seeds, reduce the time for crystal growing, realize the technical effect of low energy consumption and continuous production.The preparation method effectively controls the crystal shape, makes the finished product monohydrate lactitol uniform in size, mainly concentrates in 0.250-0.425 mm, has good processability and fluidity, is not easy to be caked in the storage process, and improves the quality of the monohydrate lactitol crystal.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of lactitol preparation, and particularly relates to a preparation method of monohydrate lactitol and application thereof. BACKGROUND

[0002] The chemical name of lactitol is 4-O-beta-D-galactopyranose-D-sorbitol. Lactitol is a white crystal or crystalline powder, and mainly exists in the form of anhydrous lactitol, monohydrate lactitol and dihydrate lactitol. At present, the most common and widely used lactitol on the market is monohydrate lactitol. Lactitol is a low-calorie sweetener with mild sweetness and only half the calories of sucrose. Lactitol has high stability and extremely low hygroscopicity, and is a good sucrose substitute. In addition, lactitol has prebiotic efficacy, can regulate intestinal flora and improve the immunity of the body, can effectively treat constipation, can protect the liver, and can be used in the pharmaceutical industry. The GI value of lactitol is only 2-3, and the metabolism of lactitol does not depend on insulin, so lactitol can be used as a sweetener for diabetic patients. Due to the good performance of lactitol, lactitol is usually applied to candies, baked goods, chocolates and other foods, and can also be applied to daily chemical products.

[0003] Patent CN113817001A discloses a production process of lactitol crystals. However, the crystallization temperature in the process is 78-98 DEG C, the crystallization temperature control is relatively high, the equipment and pipeline insulation requirements are high, and the energy consumption is also high. Patent CN103980329A discloses a lactitol crystallization process. However, the process mainly has the problem of discontinuity in production, and is not suitable for large-scale production. Therefore, there is an urgent need for a preparation method with low energy consumption, which can realize continuous production and prepare monohydrate lactitol with uniform and consistent morphology. SUMMARY

[0004] In view of the above technical problems, the first purpose of the present application is to provide a preparation method of monohydrate lactitol. The preparation method only needs to add crystal seeds once, and does not need to add crystal seeds repeatedly, thereby reducing the time for crystal growth, realizing continuous evaporation and crystallization production, effectively controlling the crystal morphology, and making the crystal size mainly concentrated in 0.250-0.425 mm. The prepared monohydrate lactitol product has uniform and consistent size, good processability and flowability, and is easy to store without caking.

[0005] The second purpose of the present application is to provide the application of the above preparation method in continuous production of monohydrate lactitol crystals and / or improvement of the quality of monohydrate lactitol crystals.

[0006] In order to achieve the above purposes of the present application, the technical scheme of the present application is as follows:

[0007] The present application provides a preparation method of monohydrate lactitol, which comprises the following steps:

[0008] (1) lactitol A liquid and lactitol powder are mixed in a proportion of 30-33% of the volume of the container, and evaporative crystallization is performed;

[0009] (2) lactitol B liquid is added during evaporative crystallization to a proportion of 61-67% of the volume of the container, and evaporative crystallization is performed for 2-4 hours until the solid content is 85-87%, and the reaction is stopped, and the container is left to stand for 45-60 minutes;

[0010] (3) a lactitol monohydrate liquid is obtained by cooling and crystallization from the bottom of the container, and lactitol monohydrate is obtained by centrifugation and drying;

[0011] The lactitol A liquid is a lactitol solution with a purity of 92-93% and a solid content of 79-81%;

[0012] The lactitol powder is added in an amount of 3-5 ‰ of the dry mass of the lactitol A liquid;

[0013] The lactitol B liquid is a lactitol solution with a purity of ≥95% and a solid content of 55-60%.

[0014] As an embodiment, the following step is further included: (4) after the removal of the liquid, the remaining liquid in the container is subjected to evaporative crystallization, and the operation of steps (2) to (3) is repeated.

[0015] As an embodiment, the evaporative crystallization is performed at a temperature of 60-70°C, a stirring speed of 120-170 rpm, and a pressure of -0.06 to -0.08 MPa.

[0016] As an embodiment, the lactitol A liquid is prepared by catalytic hydrogenation of a 45-50% lactose solution, and a lactitol hydrogenation liquid with a purity of 92-93% is obtained after reaction for 3-3.5 hours, followed by decolorization, ion exchange, and concentration.

[0017] As an embodiment, the lactitol B liquid is prepared by catalytic hydrogenation of a 45-50% lactose solution, and a lactitol hydrogenation liquid with a purity of ≥95% is obtained after reaction for 4-5 hours, followed by decolorization, ion exchange, and concentration.

[0018] As an embodiment, the hydrogenation is performed at a temperature of 110-130°C, a reactor pressure of 4-5 MPa, and a stirring speed of 400-600 rpm.

[0019] As an embodiment, the concentration is vacuum concentration, and the pressure is -0.06 to -0.1 MPa, and the temperature is 65-75°C.

[0020] As an implementation form, in the step (1), the lactitol powder is sieved to 200-220 meshes.

[0021] As an implementation form, in the step (3), the temperature is decreased from 60-70 ℃ to 45-50 ℃, and the temperature decreasing frequency is 0.3-0.6 ℃ / h.

[0022] The application also provides the application of the preparation method in continuous production of lactitol monohydrate crystals and / or improvement of the quality of lactitol monohydrate crystals.

[0023] Compared with the prior art, the application has the following beneficial effects:

[0024] 1. The application is a method capable of realizing continuous evaporation and temperature decreasing crystallization. In the crystallization process, less crystal seeds are added, and the crystal seeds are small in size. After a period of heat preservation, the crystal seeds grow up, thereby playing a role in inducing crystallization.

[0025] 2. In the application, the small crystals in the remaining solution after taking out the material are used as the crystal seeds for continuous evaporation and crystallization. The crystals are basically uniform in size and shape, can effectively control the shape of the crystals, and make the size of the finished product lactitol monohydrate mainly concentrate in 0.250-0.425 mm, so that the finished product has good processability and fluidity and is not easy to be caked during storage. The application realizes the infinite circulation of continuous crystallization through taking out the material and feeding the material. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 It is a process flow diagram for continuous production of lactitol monohydrate.

[0027] Figure 2 It is a crystal morphology diagram of lactitol monohydrate prepared in Example 1.

[0028] Figure 3 It is a crystal morphology diagram of lactitol monohydrate prepared in Example 2.

[0029] Figure 4 It is a crystal morphology diagram of lactitol monohydrate prepared in Example 3.

[0030] Figure 5 It is a crystal morphology diagram of lactitol monohydrate prepared in Example 4.

[0031] Figure 6 It is a crystal morphology diagram of lactitol monohydrate prepared in Comparative Example 1.

[0032] Figure 7 It is a crystal morphology diagram of lactitol monohydrate prepared in Comparative Example 2.

[0033] Figure 8 It is a crystal morphology diagram of lactitol monohydrate prepared in Comparative Example 3.

[0034] Figure 9 The lactitol monohydrate crystal morphology chart prepared for Comparative Example 4. DETAILED DESCRIPTION

[0035] The present application provides a preparation method of lactitol monohydrate, comprising the following steps:

[0036] (1) mixing lactitol A liquid and lactitol powder in a proportion of 30% to 33% of the volume of the container, and evaporating and crystallizing;

[0037] The lactitol A liquid is a lactitol solution with a purity of 92% to 93% and a solid content of 79% to 81%.

[0038] The addition amount of the lactitol powder is 3 to 5 ‰ of the dry matter mass of the lactitol A liquid.

[0039] In the present application, the preparation method of the lactitol A liquid comprises catalytic hydrogenation of a lactose solution with a concentration of 45% to 50% and a pH value of 7.0 to 8.0, and the reaction is carried out for 3 to 3.5 hours to obtain a lactitol hydrogenation liquid with a purity of 92% to 93%, followed by decolorization, ion exchange and concentration. In the present application, 0.5 to 1.0% of magnesium strips and 0.5 to 2.0% of sodium citrate are added before the catalytic reaction, wherein the magnesium strips and sodium citrate serve as a buffer to maintain the alkaline environment during the reaction. As an optional embodiment, the catalyst for the catalytic hydrogenation is Raney nickel, and the addition amount of the catalyst is 2 to 5%; the temperature for the catalytic hydrogenation is 110 to 130℃, and the temperature is preferably 110℃, 115℃, 120℃, 125℃ or 130℃; hydrogen gas is introduced during the catalytic hydrogenation to make the pressure reach 4 to 5 MPa; and the stirring speed during the catalytic hydrogenation is 400 to 600 rpm, and the stirring speed is preferably 500 rpm.

[0040] In the present application, the decolorization is carried out by using an activated carbon column to obtain a lactitol solution with a light transmittance of ≥95.0%; and the temperature for the decolorization is 70 to 80℃, and the temperature is preferably 75℃. In the present application, the ion exchange resin is a combination of positive resin-negative resin-positive resin-negative resin to obtain a lactitol solution with a light transmittance of ≥98.0% and a pH value of 4.5 to 7.0; the positive resin is preferably D001, and the negative resin is preferably D354; the flow rate for the ion exchange is 1.5 to 2.5 BV / h, and the flow rate is preferably 2 BV / h; and the temperature for the ion exchange is 30 to 40℃, and the temperature is preferably 35℃.

[0041] In the present application, the lactitol solution with solid content of 79-81% is prepared by concentration, the concentration is vacuum concentration, the vacuum pressure is -0.06 to -0.1 Mpa, preferably -0.07 Mpa, -0.08 Mpa, -0.09 Mpa or -0.1 Mpa; the concentration temperature is 65-75℃, preferably 65℃, 67℃, 70℃, 72℃ or 75℃. In the present application, the lactose is derived from commercially available products.

[0042] In the present application, the lactitol powder is prepared by crushing 200-200 mesh sieve. In the present application, the lactitol powder is used as the seed crystal of evaporation crystallization, which plays a role in inducing crystallization. In the present application, the lactitol is derived from commercially available products.

[0043] In the present application, 30-33% lactitol A liquid of the container volume is added to the container, then 3-5‰ lactitol powder of the dry matter mass of lactitol A liquid is added, the temperature of the container is controlled at 60-62℃ before evaporation crystallization, preferably 60℃, 61℃ or 62℃, and is stabilized for 3-5 h. Under the above conditions of the present application, the lactitol powder seed crystal is grown for a period of time, which is beneficial to the subsequent induced crystallization.

[0044] (2) During the evaporation crystallization, lactitol B liquid is supplemented to 61-67% of the container volume, the evaporation crystallization is stopped when the solid content is 85-87% after 2-4 h, and is placed for 45-60 min;

[0045] The lactitol B liquid is a lactitol solution with purity ≥95% and solid content of 55-60%.

[0046] In the present application, the preparation method of the lactitol B liquid includes catalytic hydrogenation of 45-50% lactose solution with pH value of 7.0-8.0, reaction for 4-5 h to obtain lactitol hydrogenation liquid with purity ≥95%, and then decolorization, ion exchange and concentration are carried out in sequence. In the present application, 0.5-1.0% magnesium strip and 0.5-2.0% sodium citrate are added before catalytic reaction, wherein the magnesium strip and sodium citrate play a buffering role to maintain the alkaline environment during the reaction. As an optional embodiment, the catalyst for catalytic hydrogenation is Raney nickel, and the addition amount of the catalyst is 2-5%; the catalytic hydrogenation temperature is 110-130℃, preferably 110℃, 115℃, 120℃, 125℃ or 130℃; hydrogen is introduced to make the pressure reach 4-5 MPa during the catalytic hydrogenation; the stirring speed of the catalytic hydrogenation is 400-600 rpm, preferably 500 rpm.

[0047] In the present application, the decolorization adopts activated carbon column decolorization to obtain lactitol solution with light transmittance ≥ 95.0%; the temperature of the decolorization is 70-80℃, and the temperature is preferably 75℃. In the present application, the ion exchange resin adopts the combination of positive resin-negative resin-positive resin-negative resin to obtain lactitol solution with light transmittance ≥ 98.0% and pH 4.5-7.0; the positive resin is preferably D001, and the negative resin is preferably D354; the flow rate of the ion exchange is 1.5-2.5 BV / h, and the flow rate is preferably 2 BV / h; the temperature of the ion exchange is 30-40℃, and the temperature is preferably 35℃.

[0048] In the present application, lactitol solution with solid content of 55-60% is prepared by concentration, the concentration is vacuum concentration, the vacuum pressure is -0.06--0.1 Mpa, and the pressure is preferably -0.07 Mpa, -0.08 Mpa, -0.09 Mpa or -0.1 Mpa; the temperature of the concentration is 65-75℃, and the temperature is preferably 65℃, 67℃, 70℃, 72℃ or 75℃. In the present application, lactose is derived from commercially available products.

[0049] In the present application, lactitol B solution is supplemented during evaporation crystallization, and the flow rate of the supplement is not specifically limited. During the evaporation crystallization process, the temperature and concentration of the feed liquid are controlled, and the flow rate needs to be adjusted according to the change in concentration. The supplement is stopped when the supplementing volume accounts for 61-67% of the volume of the container, the evaporation crystallization is stopped after 2-4 h when the solid content is 85%-87%, and the crystallization reaction is stopped after standing for 45-60 min. As an alternative embodiment, in the present application, the temperature of the evaporation crystallization is 60-70℃, and is preferably 60℃, 62℃, 65℃, 67℃ or 70℃; the stirring speed of the evaporation crystallization is 120-170 rpm, and is preferably 120 rpm, 130 rpm, 140 rpm, 150 rpm, 160 rpm or 170 rpm; and the pressure of the evaporation crystallization is -0.06--0.08 Mpa, and is preferably -0.06 Mpa, -0.07 Mpa or -0.08 Mpa.

[0050] In the present application, after the evaporation crystallization reaction is completed, the standing time is 45-60 min, and the standing time is preferably 45 min, 50 min, 55 min or 60 min.

[0051] (3) The feed liquid with a volume accounting for 30-33% of the volume of the container is taken out from the bottom of the container, cooled and crystallized to obtain lactitol monohydrate feed liquid, and then centrifuged and dried to obtain lactitol monohydrate.

[0052] In the present application, the withdrawn feed liquid is subjected to cooling crystallization, wherein the temperature is reduced from 60-70℃ to 45-50℃, and the cooling rate is 0.3-0.6℃ / h, and the cooling rate is preferably 0.3℃ / h, 0.4℃ / h, 0.5℃ / h or 0.6℃ / h.

[0053] In the present application, monohydrate lactitol is prepared by centrifugation and drying of a lactitol feed liquid. The centrifugation is carried out at a temperature of 45-50℃, and the temperature is preferably 45℃, 46℃, 47℃, 48℃, 49℃ or 50℃; the centrifugation is carried out at a speed of 500-1000 rpm; and after centrifugation, drying is carried out, and as an optional embodiment, the drying is preferably fluidized bed drying, wherein the inlet air temperature during drying is controlled to be 70-100℃, and the temperature is preferably 70℃, 80℃, 90℃ or 100℃; and the relative humidity during drying is ≤50%. The monohydrate lactitol prepared after cooling crystallization has a purity of ≥99%, a moisture content of 4.5-6.5%, and the crystal size is uniform, with more than 80% concentrated in the range of 0.250-0.425 mm, and has good processability and flowability. The lactitol A liquid in the present application has a purity of 92-93% as the crystallization feed liquid; the lactitol B liquid has a purity of ≥95% as the make-up feed liquid, and in the process of evaporation crystallization, by supplementing the high-purity feed liquid, the initial purity of the crystallization tank after continuous circulation can be maintained at 92-93%, and thus the withdrawn feed liquid has a high purity due to the high purity of the crystals and the presence of part of the mother liquor, and the overall purity of the monohydrate lactitol obtained is higher than 98%, thereby ensuring the purity and uniformity of the crystals.

[0054] (4) After the withdrawal of the feed liquid, the remaining feed liquid in the container is subjected to evaporation crystallization, and the operations of steps (2) to (3) are repeated.

[0055] In the present application, the lactitol B liquid is supplemented into the remaining feed liquid after the withdrawal of the feed liquid according to the method described in step (2), and continuous production is achieved by the withdrawal and make-up of the feed liquid to realize continuous crystallization. The upper liquid after standing in the present application still contains crystals with uniform size and small volume, and thus it can be directly used as the crystal seeds for continuous evaporation crystallization without the need for heat preservation and crystal growth, thereby reducing the steps for preparing the crystal seeds and the time for crystal growth, and simplifying the method and the loss of energy consumption.

[0056] Based on the above preparation method, continuous production of monohydrate lactitol can be achieved, and the crystal shape can be effectively controlled, so that the particle size of the monohydrate lactitol is concentrated in the range of 0.250-0.425 mm, and has good processability and flowability. The present application also provides the above preparation method for continuous production of monohydrate lactitol crystals and / or improvement of the quality of monohydrate lactitol crystals.

[0057] In order to make the purpose, technical scheme and advantages of the present application clearer and more apparent, the present application will be described in detail below with reference to the examples, but they should not be understood as limiting the scope of protection of the present application.

[0058] The materials, reagents, etc. used in the following examples, unless otherwise specified, can be obtained from commercial sources, such as the reagents, consumables, etc. related to the present application, and are generally used according to the conventional conditions, or according to the conditions recommended by the company.

[0059] Example 1

[0060] A method for preparing lactitol monohydrate is as follows (see the schematic diagram of the process flow for continuous production Figure 1 ) :

[0061] (1) Add lactitol A liquid into the evaporation crystallization tank to 30% of the volume of the evaporation crystallization tank, then add 3‰ of the dry matter mass of lactitol A liquid as seed crystals, and mix well. The temperature of the evaporation crystallization tank is 60°C, and it is stabilized for 3 h.

[0062] The preparation method of lactitol A liquid is as follows: 45% lactose solution system with pH value of 7.0 is added with 5% Raney nickel, then 1.0% magnesium strip and 0.5% sodium citrate are added, and catalytic hydrogenation is carried out under the conditions of temperature of 130°C, stirring speed of 500 rpm, and hydrogen gas being introduced to make the pressure 5 MPa, and the reaction is carried out for 3.5 h to obtain lactitol hydrogenation liquid with purity of 92.65%. The 92.65% lactitol hydrogenation liquid is decolorized using an activated carbon column under the condition of 75°C to obtain lactitol solution with transmittance of 96.5%. Ion exchange is carried out using the combination of resins D001-D354-D001-D354 under the conditions of 35°C and flow rate of 2.0 BV / h to obtain lactitol solution with transmittance of 99.2% and pH value of 5.3. The 92.65% lactitol after refining is vacuum concentrated under the conditions of pressure of -0.06 Mpa and temperature of 75°C to obtain lactitol solution with solid content of 79%.

[0063] Preparation of seed crystals: lactitol is crushed through a 200-220 mesh sieve.

[0064] (2) Lactitol B liquid is supplemented during the evaporation crystallization process, and the flow rate of the supplement is not specifically limited. During the evaporation crystallization process, the temperature and concentration of the feed liquid are controlled, and the flow rate needs to be adjusted according to the change in concentration. The supplement is stopped when the volume ratio of the evaporation crystallization tank reaches 61%. At the same time of supplementing lactitol B liquid, evaporation crystallization is carried out under the conditions of temperature of 60-68°C, stirring speed of 150 rpm, and pressure of -0.08 Mpa. The crystallization reaction is stopped when the solid content in the feed liquid is 85% after 2 h of evaporation crystallization, and the system is allowed to stand for 60 min.

[0065] The preparation method of lactitol B solution is as follows: 45% lactose solution with pH value of 7.0 is added with 5% Raney nickel, then 1.0% magnesium strip and 0.5% sodium citrate, and catalytic hydrogenation is carried out under the conditions of temperature of 130°C, stirring speed of 500 rpm, and hydrogen inlet to make the pressure reach 5 MPa, and reaction for 4 h to obtain lactitol hydrogenation solution with purity of 95.84%. The 95.84% lactitol hydrogenation solution is subjected to decolorization by using an activated carbon column under the condition of 75°C to obtain lactitol solution with transmittance of 96.5%. Ion exchange is carried out by using the combination of resins D001-D354-D001-D354 under the conditions of 35°C and flow rate of 2.0 BV / h to obtain lactitol solution with transmittance of 99.2% and pH value of 5.3. The 95.84% lactitol after refinement is subjected to vacuum concentration under the conditions of pressure of -0.06 MPa and temperature of 75°C to obtain lactitol solution with solid content of 55%.

[0066] (3) 30% of the volume of the liquid in the evaporation crystallization tank is discharged to the cooling crystallization tank, cooling is completed at a cooling rate of 0.3°C / h from 68°C to 50°C to obtain lactitol monohydrate solution. Then, the lactitol monohydrate solution is centrifuged at 45°C and a rotation speed of 1000 rpm to obtain crystals, and the crystals are dried in a fluidized bed at 70°C and a relative humidity of ≤50% to obtain lactitol monohydrate crystals.

[0067] (4) After the liquid is discharged, the remaining liquid in the evaporation crystallization tank is repeatedly circulated according to steps (2) to (3) for 7 times, and each time the obtained product has purity of ≥99.4%, moisture content of 4.5-6.5%, and crystal size of 0.250-0.425 mm, accounting for 82.0-85.3% of lactitol monohydrate.

[0068] Example 2

[0069] A method for preparing lactitol monohydrate is as follows:

[0070] (1) Lactitol A solution is added to the evaporation crystallization tank to a volume of 31%, and then 4‰ of crystal seeds based on the dry matter mass of the lactitol A solution are added and mixed, and the temperature of the evaporation crystallization tank is 61°C, and the temperature is stabilized for 4 h.

[0071] The preparation method of lactitol A liquid: 48%, pH 7.5 lactose solution system is added with 4% Raney nickel, then 0.8% magnesium strip and 1.0% sodium citrate, catalytic hydrogenation is carried out under the conditions that the temperature is 125 ℃, the stirring speed is 500 rpm, hydrogen is introduced to make the pressure 5 MPa, and the reaction is carried out for 3.5 h to obtain 92.65% lactitol hydrogenation liquid. The 92.65% lactitol hydrogenation liquid is decolorized by using an activated carbon column under the condition that the temperature is 75 ℃ to obtain a lactitol solution with a transmittance of 95.7%. Ion exchange is carried out by using the combination of resins D001-D354-D001-D354 under the conditions that the temperature is 35 ℃ and the flow rate is 2.0 BV / h to obtain a lactitol solution with a transmittance of 98.5% and pH 4.8. The 92.65% lactitol after refining is vacuum concentrated under the conditions that the pressure is -0.08 Mpa and the temperature is 70 ℃ to obtain a lactitol solution with a solid content of 80%.

[0072] Preparation of crystal seeds: lactitol is crushed through a 200-200 mesh sieve.

[0073] (2) Lactitol B liquid is supplemented during the evaporation crystallization process, and the flow rate of the supplement is not specifically limited. During the evaporation crystallization process, the temperature and concentration of the feed liquid are controlled, and the flow rate needs to be adjusted according to the change in the concentration. The supplement is stopped when the volume ratio of the supplement to the evaporation crystallization tank is 62%. At the same time of supplementing the lactitol B liquid, evaporation crystallization is carried out under the conditions that the temperature is 61-69 ℃, the stirring speed is 150 rpm, and the pressure is -0.08 Mpa. The crystallization reaction is stopped when the solid content in the feed liquid is 86% after evaporation crystallization for 3 h, and the system is allowed to stand for 45 min.

[0074] The preparation method of lactitol B liquid: 48%, pH 7.5 lactose solution system is added with 4% Raney nickel, then 0.8% magnesium strip and 1.0% sodium citrate, catalytic hydrogenation is carried out under the conditions that the temperature is 125 ℃, the stirring speed is 500 rpm, hydrogen is introduced to make the pressure 5 MPa, and the reaction is carried out for 3.5 h to obtain 92.65% lactitol hydrogenation liquid. The 92.65% lactitol hydrogenation liquid is decolorized by using an activated carbon column under the condition that the temperature is 75 ℃ to obtain a lactitol solution with a transmittance of 95.7%. Ion exchange is carried out by using the combination of resins D001-D354-D001-D354 under the conditions that the temperature is 35 ℃ and the flow rate is 2.0 BV / h to obtain a lactitol solution with a transmittance of 98.5% and pH 4.8. The 92.65% lactitol after refining is vacuum concentrated under the conditions that the pressure is -0.08 Mpa and the temperature is 70 ℃ to obtain a lactitol solution with a solid content of 80%.

[0075] (3) The 31% of the volume of the liquid in the evaporative crystallization tank is discharged to the cooling crystallization tank, and the cooling frequency is 0.4°C / h, and the temperature is reduced from 69°C to 50°C to complete the cooling crystallization, and monohydrate lactitol liquid is obtained. Then, the monohydrate lactitol liquid is centrifuged at 50°C and a speed of 500 rpm to obtain crystals, and then fluidized bed drying is performed at 100°C and a relative humidity of ≤50% to obtain monohydrate lactitol crystals.

[0076] (4) After the liquid is discharged, the remaining liquid in the evaporative crystallization tank continues to repeat steps (2) to (3), and the purity of the product obtained each time is ≥99.4%, the moisture content is 4.5-6.5%, and the crystal size is 0.250-0.425 mm, accounting for 82.0-85.3% of monohydrate lactitol.

[0077] Example 3

[0078] A method for preparing monohydrate lactitol is as follows:

[0079] (1) Lactitol A liquid is added to the evaporative crystallization tank, and the volume of the evaporative crystallization tank is 33%, and then 5‰ of the dry matter mass of the lactitol A liquid is added to the crystallization tank, and the temperature of the evaporative crystallization tank is 62°C, and the temperature is stabilized for 5 hours.

[0080] The preparation method of lactitol A liquid is as follows: 50% lactose solution system with pH value of 8.0 is added with 3% Raney nickel, then 0.5% magnesium strip and 2.0% sodium citrate are added, and catalytic hydrogenation is carried out under the conditions of temperature of 115°C, stirring speed of 500 rpm, and hydrogen pressure of 5 MPa, and reaction time of 3.5 hours to obtain 92.65% lactitol hydrogenation liquid. The 92.65% lactitol hydrogenation liquid is decolorized by activated carbon column at 75°C to obtain lactitol solution with a transmittance of 96.6%. The combination of resins D001-D354-D001-D354 is used for ion exchange at 35°C and a flow rate of 2.0 BV / h to obtain lactitol solution with a transmittance of 98.5% and a pH of 5.9. The 92.65% lactitol after refining is vacuum concentrated at a pressure of -0.1 Mpa and a temperature of 65°C to obtain lactitol solution with a solid content of 81%.

[0081] Preparation of the seed crystal: lactitol is crushed through a 200-200 mesh sieve.

[0082] (2) During the evaporation and crystallization process, lactitol B solution is added. The flow rate of the addition is not specifically limited. During the evaporation and crystallization process, the temperature and concentration of the solution are controlled. The flow rate needs to be adjusted according to the concentration change. The addition is stopped when the volume of the evaporation and crystallization tank reaches 66%. While adding lactitol B solution, evaporation and crystallization are carried out at a temperature of 62~70℃, a stirring speed of 150 rpm, and a pressure of -0.07 MPa. The crystallization reaction is stopped when the solid content in the solution reaches 87% after 4 hours of evaporation and crystallization, and the solution is allowed to stand for 45 minutes.

[0083] Preparation method of lactitol B solution: 3% Raney nickel (by mass) was added to a 50% lactose solution system with pH 8.0, followed by 0.5% magnesium strips and 2.0% sodium citrate. Catalytic hydrogenation was carried out at 115℃, a stirring speed of 500 rpm, and a pressure of 5 MPa under hydrogen gas. The reaction was allowed to proceed for 4.5 h to obtain a lactitol hydrogenated solution with a purity of 95.47%. The 95.47% lactitol hydrogenated solution was decolorized using an activated carbon column at 75℃ to obtain a lactitol solution with a transmittance of 96.6%. Ion exchange was performed using a combination of resins D001-D354-D001-D354 at 35℃ and a flow rate of 2.0 BV / h to obtain a lactitol solution with a transmittance of 98.5% and a pH of 5.9. The purified lactitol with a purity of 95.47% was concentrated under vacuum at a pressure of -0.1 MPa and a temperature of 65°C to obtain a lactitol solution with a solid content of 60%.

[0084] (3) Discharge 33% of the container volume of the liquid from the bottom of the evaporation crystallizer to the cooling crystallizer, and cool down at a frequency of 0.6℃ / h, from 70℃ to 50℃ to complete the cooling crystallization, to obtain lactitol monohydrate liquid. Then, centrifuge the lactitol monohydrate liquid at 50℃ and 1000 rpm to obtain crystals, and then perform fluidized bed drying at 80℃ and relative humidity ≤50% to obtain lactitol monohydrate crystals.

[0085] (4) After the liquid is discharged, the remaining liquid in the evaporation crystallizer continues to repeat steps (2) to (3) for 7 times. Each time, the purity of the finished product is ≥99.4%, the moisture content is 4.5~6.5%, and the crystal size is 0.250~0.425 mm, accounting for 82.0~85.3% of the lactitol monohydrate.

[0086] Example 4

[0087] A method for preparing lactitol monohydrate is as follows:

[0088] (1) Add lactitol A solution to the evaporation crystallizer until it reaches 30% of the volume of the evaporation crystallizer. Then add seed crystals of 3‰ of the dry matter mass of lactitol A solution and mix well. The temperature of the evaporation crystallizer is 61℃ and it is stable for 4 h.

[0089] The preparation method of lactitol A solution: 50%, pH 7.0 lactose solution system is added with 4.5% Raney nickel, then 0.5% magnesium strip and 1.5% sodium citrate, catalytic hydrogenation under the conditions of temperature 110℃, stirring speed 500 rpm, hydrogen is introduced to make the pressure to 5 MPa, reaction for 3.5 h to obtain 92.65% purity lactitol hydrogenation solution. The 92.65% lactitol hydrogenation solution is decolorized by activated carbon column at 75℃ to obtain lactitol solution with a transmittance of 95.9%. Ion exchange is carried out using the combination of resins D001-D354-D001-D354 at 35℃ and a flow rate of 2.0 BV / h to obtain lactitol solution with a transmittance of 99.0% and pH 6.2. The 92.65% purity lactitol after refining is vacuum concentrated under the conditions of pressure -0.1 Mpa and temperature 75℃ to obtain lactitol solution with a solid content of 80%.

[0090] Preparation of crystal seeds: lactitol is crushed to pass through a 200-200 mesh sieve.

[0091] (2) Lactitol B solution is supplemented during the evaporation crystallization process, and the flow rate of the supplement is not specifically limited. During the evaporation crystallization process, the temperature and concentration of the feed liquid are controlled, and the flow rate needs to be adjusted according to the change in concentration. The supplement is stopped when the volume ratio of the supplement to the evaporation crystallization tank is 61%. At the same time of supplementing lactitol B solution, evaporation crystallization is carried out under the conditions of temperature 61-68℃, stirring speed 150 rpm and pressure -0.06 Mpa. The crystallization reaction is stopped when the solid content in the feed liquid is 85% after evaporation crystallization for 2 h, and the liquid is allowed to stand for 45 min.

[0092] The preparation method of lactitol B solution: 50%, pH 7.0 lactose solution system is added with 4.5% Raney nickel, then 0.5% magnesium strip and 1.5% sodium citrate, catalytic hydrogenation under the conditions of temperature 110℃, stirring speed 500 rpm, hydrogen is introduced to make the pressure to 5 MPa, reaction for 5 h to obtain 96.29% purity lactitol hydrogenation solution. The 96.29% lactitol hydrogenation solution is decolorized by activated carbon column at 75℃ to obtain lactitol solution with a transmittance of 95.9%. Ion exchange is carried out using the combination of resins D001-D354-D001-D354 at 35℃ and a flow rate of 2.0 BV / h to obtain lactitol solution with a transmittance of 99.0% and pH 6.2. The 96.29% purity lactitol after refining is vacuum concentrated under the conditions of pressure -0.1 Mpa and temperature 75℃ to obtain lactitol solution with a solid content of 60%.

[0093] (3) 30% of the volume of the liquid in the evaporation crystallization tank is discharged to the cooling crystallization tank, and cooling is completed at a cooling rate of 0.5 ℃ / h from 68 ℃ to 50 ℃ to obtain monohydrate lactitol liquid, then the monohydrate lactitol liquid is centrifuged at 45 ℃ and a rotation speed of 800 rpm to obtain crystals, and the crystals are dried in a fluidized bed at 90 ℃ and a relative humidity of ≤50% to obtain monohydrate lactitol crystals.

[0094] (4) After the liquid is discharged, the remaining liquid in the evaporation crystallization tank is repeatedly circulated according to steps (2) to (3) for 7 times, and the purity of the product obtained each time is ≥99.4%, the moisture content is 4.5-6.5%, and the crystal size of the monohydrate lactitol is 0.250-0.425 mm, accounting for 82.0-85.3%.

[0095] Comparative Example 1

[0096] Compared with Example 1, the solid content of the lactitol solution added in step (2) is 45%, and other conditions are the same as those in Example 1. After repeating 7 times, the monohydrate lactitol crystals obtained each time are larger, and the crystals larger than 0.425 mm are more, and the crystal size in the range of 0.250-0.425 mm accounts for 64.6%. This shows that, to achieve the same solid content, too high or too low concentration of the added material will make the overall size of the crystals larger.

[0097] Comparative Example 2

[0098] Compared with Example 1, the solid content of the lactitol solution added in step (2) is 65%, and other conditions are the same as those in Example 1. After repeating 7 times, the monohydrate lactitol crystals obtained each time are larger, and the crystals larger than 0.425 mm are more, and the crystal size in the range of 0.250-0.425 mm accounts for 58.4%. This shows that, to achieve the same solid content, too high or too low concentration of the added material will make the overall size of the crystals larger.

[0099] Comparative Example 3

[0100] Compared with Example 1, 25% of the volume of the liquid in the evaporation crystallization tank is discharged to the cooling crystallization tank in step (3), and other conditions are the same as those in Example 1. After repeating 7 times, the purity of the monohydrate lactitol obtained each time is 94-95%, and the crystals are larger, and the crystals larger than 0.425 mm are more, and the crystal size in the range of 0.250-0.425 mm accounts for 72.8%. This shows that too high or too low volume of the discharged liquid will affect the purity of the crystals, and also make the overall size of the crystals larger.

[0101] Comparative Example 4

[0102] Compared with Example 1, step (3) is to discharge 40% of the volume of the liquid from the evaporation crystallization tank to the cooling crystallization tank, and the other conditions are consistent with Example 1. After repeating 7 times, the purity of monohydrate lactitol obtained finally is 94-95%, the crystal size is larger, and the crystal size of 0.250-0.425 mm accounts for 73.3%. Therefore, the volume of the discharged liquid is too high or too low, which will affect the purity of crystallization and also make the overall size of the crystal larger.

[0103] Comparative Example 5

[0104] Compared with Example 1, step (2) is to add lactitol B liquid while evaporating and crystallizing at a temperature of 60-75°C. When the final liquid temperature reaches 75°C, the other conditions are consistent with Example 1. When the volume of the liquid in the evaporation crystallization tank is 61% of the volume of the evaporation crystallization tank, the solid content of the liquid reaches 90.0%, which leads to high viscosity of the centrifuged material, incomplete removal of the mother liquor, and the purity of the material is 98.34%. During the drying process, caking occurs, and the crystal that meets the requirements cannot be obtained.

[0105] Test Example 1 Product Particle Size

[0106] The particle size directly affects the flowability of the particles. The higher the proportion of the particle size of 0.250-0.425 mm, the better the flowability, which can improve the production efficiency and the stability of the preparation. The proportion of the monohydrate lactitol prepared according to the preparation methods of Examples 1-4 and Comparative Examples 1-5 in the particle size of 0.250-0.425 mm is shown in Table 1, and the crystal morphology of the monohydrate lactitol prepared in each group is shown in Figures 2-9 .

[0107] Table 1 Product Particle Size

[0108]

[0109] Test Example 2 Determination of Particle Flowability

[0110] The angle of repose is an important indicator of flowability. When the angle of repose is <30°, the flowability is excellent. The monohydrate lactitol prepared in Examples 1-4 and Comparative Examples 1-5 is subjected to angle of repose detection, and the detection results are shown in Table 2.

[0111] The angle of repose detection method is as follows: a dry and clean funnel is fixed on an iron stand, and the lowermost funnel opening is 2.5 cm (H) from the horizontally placed coordinate paper. The monohydrate lactitol is poured along the funnel wall into the funnel until the last funnel forms a particle cone tip that touches the funnel opening. The cone diameter (2R) is measured on the coordinate paper, tan θ = H / R, and θ is the angle of repose.

[0112] Table 2 Granule flowability test

[0113]

[0114] From the above results, it can be seen that the preparation method of the present application not only enables continuous production in 7 cycles, but also enables almost no difference in the finished product each time, and improves the flowability and quality of the product.

[0115] The above only describes the embodiments of the present application, and does not limit the patent scope of the present application, and any equivalent structure or equivalent process transformation using the content of the present application specification, or direct or indirect application in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A process for the preparation of monohydrate lactitol, characterized by, The method comprises the following steps: (1) mixing lactitol A liquid and lactitol powder in a proportion of 30-33% of the volume of the container, and evaporating and crystallizing; (2) supplementing lactitol B liquid to a proportion of 61-67% of the volume of the container during the evaporating and crystallizing process, evaporating and crystallizing for 2-4 hours, stopping the reaction when the solid content is 85-87%, and standing for 45-60 minutes; (3) taking out a lactitol monohydrate liquid in a proportion of 30-33% of the volume of the container from the bottom of the container, cooling and crystallizing to obtain a lactitol monohydrate liquid, and then centrifuging and drying to obtain lactitol monohydrate; (4) after taking out the liquid, continuing to evaporate and crystallize the remaining liquid in the container, and repeating the operations of steps (2) and (3); the lactitol A liquid is a lactitol solution with a purity of 92-93% and a solid content of 79-81%; the lactitol powder is added in an amount of 3-5 ‰ of the dry matter mass of the lactitol A liquid; the lactitol B liquid is a lactitol solution with a purity of ≥95% and a solid content of 55-60%; the evaporating and crystallizing is performed at a temperature of 60-70°C, a stirring speed of 120-170 rpm, and a pressure of -0.06 to -0.08 MPa.

2. The production method according to claim 1, characterized by, The preparation method of the lactitol A liquid comprises catalytic hydrogenation of a 45-50% lactose solution, reaction for 3-3.5 hours to obtain a lactitol hydrogenation liquid with a purity of 92-93%, and then decolorization, ion exchange, and concentration in sequence.

3. The method of claim 1, wherein, The preparation method of the lactitol B liquid comprises catalytic hydrogenation of a 45-50% lactose solution, reaction for 4-5 hours to obtain a lactitol hydrogenation liquid with a purity of ≥95%, and then decolorization, ion exchange, and concentration in sequence.

4. The production method according to claim 2 or 3, characterized by, The hydrogenation is performed at a temperature of 110-130°C, a reactor pressure of 4-5 MPa, and a stirring speed of 400-600 rpm.

5. The production method according to claim 2 or 3, characterized by, The concentration is vacuum concentration at a pressure of -0.06 to -0.1 MPa and a temperature of 65-75°C.

6. The method of claim 1, wherein, In step (1), the lactitol powder is sieved to 200-220 mesh.

7. The preparation method according to claim 1, characterized in that, In step (3), the cooling and crystallization is performed at a temperature decreasing from 60-70°C to 45-50°C at a cooling rate of 0.3-0.6°C / h.

8. Use of the preparation method of any one of claims 1-7 in continuous production of lactitol monohydrate crystals and / or improving the quality of lactitol monohydrate crystals.

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