A method for preparing high-purity sorbitol from starch

Abstract

This invention proposes a method for preparing high-purity sorbitol from starch, belonging to the field of sugar alcohol separation and purification technology. The method involves steps such as starch hydrolysis to glucose, catalytic hydrogenation, pretreatment, membrane separation purification, chromatographic purification, post-treatment of the purified solution, and finished product testing to prepare sorbitol. This effectively solves the problems of low purification efficiency and limited purity improvement associated with single separation techniques. The final sorbitol product obtained has a purity of ≥98.5%, with a maximum of 99.2%, fully meeting the high-purity requirements of sorbitol in high-end fields such as functional foods, special medical foods, and pharmaceutical preparations, and significantly expanding the application scenarios of sorbitol.

Description

Technical Field

[0001] This invention belongs to the field of sugar alcohol separation and purification technology, specifically relating to a method for preparing high-purity sorbitol from starch. Background Technology

[0002] With the improvement of people's living standards, health problems such as obesity, diabetes, cardiovascular disease, and oral diseases caused by high-sugar diets are becoming increasingly prominent. The research and application of low-calorie functional sweeteners has become a research hotspot in the food and pharmaceutical fields. Sorbitol, as a high-value-added product of starch deep processing, has a sweetness similar to sucrose but with lower calories. It can satisfy people's demand for sweetness while reducing calorie intake. At the same time, it cannot be used by oral bacteria to produce acid, which can inhibit the growth of streptococci and reduce the risk of oral diseases such as tooth decay. Therefore, it is widely used in important fields closely related to people's health, such as food, medicine, and daily chemicals.

[0003] The applications of sorbitol are closely related to its purity. High-end fields such as special medical purpose foods, functional foods, and pharmaceutical preparations place extremely high demands on the purity of sorbitol. In the pharmaceutical field, sorbitol can be used directly as an active ingredient in the treatment of cerebral edema and glaucoma, and it can also be used as a laxative. It is also a commonly used filler, sweetener, humectant, and coating material in pharmaceutical preparations. In the field of special medical foods, high-purity sorbitol is one of the core raw materials for nutritional formulas for special populations, providing them with professional and personalized nutritional support.

[0004] Currently, the mainstream industrial process for preparing sorbitol uses renewable, widely available, and low-cost starch as raw material. Starch is first hydrolyzed to convert it into glucose, and then sorbitol is obtained through the hydrogenation reduction of the glucose solution. At present, the industry's efforts to improve sorbitol purity mainly focus on optimizing the starch hydrolysis process to produce glucose, thereby increasing the purity of the glucose solution. However, this method has a very limited effect on improving the purity of the final sorbitol product. The industry pays very little attention to optimizing and improving the separation and purification technology during the glucose hydrogenation to sorbitol conversion process. Traditional sorbitol purification methods often employ crystallization and recrystallization, which suffer from low separation efficiency, high energy consumption, low product yield, and high labor and equipment maintenance costs. Single membrane separation or chromatographic separation technologies also have shortcomings such as insufficient purification depth and an inability to balance separation efficiency and product purity, making it difficult to meet the production demands of high-purity sorbitol in high-end applications. Therefore, developing a highly efficient, stable, energy-saving preparation method that can significantly improve the purity of sorbitol products has become an urgent technical problem to be solved in the industry. Summary of the Invention

[0005] This invention addresses the problems of existing technologies by providing a method for preparing high-purity sorbitol from starch.

[0006] To achieve the above objectives, the technical solution adopted in this application is as follows: A method for preparing high-purity sorbitol from starch, the specific steps of which are as follows: Step 1: Preparation of glucose from starch hydrolysis: Using starch as raw material, after adding deionized water to make a slurry, α-amylase is added sequentially for liquefaction hydrolysis, and saccharifying enzyme is added for saccharification hydrolysis to obtain glucose solution; Step 2: Catalytic hydrogenation: The glucose solution obtained in Step 1 is concentrated to obtain a glucose concentrate, which is then transferred to a high-pressure reactor. A ruthenium-based catalyst is added, and hydrogen gas is introduced to carry out a hydrogenation reduction reaction. After the reaction is completed, the catalyst is removed by filtration to obtain a crude sorbitol solution. Step 3: Pretreatment: Adjust the temperature and pH of the crude sorbitol solution obtained in Step 2, let it stand and remove the precipitate to obtain the pretreated crude sorbitol solution. Step 4: Membrane separation and purification: The crude sorbitol solution pretreated in Step 3 is subjected to micron-level microfiltration and nanofiltration in sequence to remove impurities and obtain the purified sorbitol initial solution. Step 5: Chromatographic separation and purification: The sorbitol purified initial solution obtained in Step 4 is passed into a moving bed chromatography system for deep separation and purification to obtain the sorbitol purified solution; Step 6: Post-treatment of the purified liquor: The sorbitol purified liquor obtained in Step 5 is subjected to vacuum concentration, activated carbon decolorization, ion exchange resin desalination, and spray drying in sequence to obtain the sorbitol product. Step 7: Finished product testing: The purity of sorbitol in the finished sorbitol product is determined by high performance liquid chromatography.

[0007] Preferably, in step one, the starch is any one of corn starch, potato starch, or rice starch; the ratio of starch to deionized water is 500 g:500 mL to 1000 g:1000 mL. The amount of α-amylase added is 0.6% to 0.8% of the starch mass; the liquefaction and hydrolysis temperature is 85℃ to 90℃, the liquefaction and hydrolysis pH is 6.2 to 6.8, and the liquefaction and hydrolysis time is 2.5 h to 3.5 h. The amount of saccharifying enzyme added is 0.6% to 0.8% of the starch mass; the saccharification and hydrolysis temperature is 60℃ to 65℃, the saccharification and hydrolysis pH is 4.5 to 5.0, and the saccharification and hydrolysis time is 5 h to 7 h.

[0008] Preferably, in step two, the amount of ruthenium-based catalyst added is 6% to 10% of the glucose mass in the glucose concentrate; the hydrogen pressure of the hydrogenation reduction reaction is 4 MPa, the reaction temperature is 110℃ to 130℃, the stirring speed is 700 rpm, the hydrogen flow rate is 0.6 L / min, and the reaction time is 3.5 h to 5 h.

[0009] Preferably, in step three, adjusting the temperature and pH of the crude sorbitol solution obtained in step two is as follows: adjusting the temperature of the crude sorbitol solution to 38℃~45℃, adjusting the pH to 7.2 using a 10% sodium hydroxide solution; and allowing it to stand for 30 minutes.

[0010] Preferably, in step four, the micron-level microfiltration treatment uses an Al2O3 ceramic microfiltration membrane with a pore size of 0.1 μm, a treatment temperature of 38℃~45℃, and an operating pressure of 0.4 MPa~0.8 MPa. The micron-level microfiltration treatment is used to remove polysaccharides and residual catalyst particles. The nano-level nanofiltration treatment uses a polyamide composite nanofiltration membrane with a molecular weight cutoff of 200 Da and a negatively charged surface, a treatment temperature of 45℃, and an operating pressure of 1.9 MPa. The nano-level nanofiltration treatment is used to remove unreacted glucose and mannitol impurities.

[0011] Preferably, in step five, the moving bed chromatography system adopts a 5-column tandem mode, with the chromatographic column filled with a strong acid styrene-based cation exchange resin with a resin particle size of 120 μm to 180 μm and an exchange capacity of 4.8 mmol / g; the eluent for chromatographic separation is deionized water, and the column temperature is controlled at 88℃ to 92℃.

[0012] As a preferred embodiment, in step six, the endpoint of the vacuum concentration of the sorbitol purified solution is that the solid content of the sorbitol purified solution is not less than 70%; the amount of activated carbon added is 0.5% of the mass of the concentrated sorbitol purified solution; the decolorization temperature is 60℃~70℃ and the decolorization time is 30 min; The ion exchange resin desalination operation involves sequentially processing with cation exchange resin and anion exchange resin.

[0013] Preferably, sensing components are installed at the microfiltration membrane outlet, nanofiltration membrane inlet and outlet, and chromatographic column inlet and outlet to collect process parameters of the separation process in real time within the threshold range. Specifically, the sensing components include a pressure sensor, a flow sensor, a concentration sensor, and a temperature sensor; the process parameters collected in real time include microfiltration operating pressure, nanofiltration membrane flux, chromatographic resolution, material feed concentration, and material temperature.

[0014] Preferably, the pressure sensor is located at the inlet of the microfiltration membrane, and the microfiltration operating pressure is 0.4 MPa to 0.8 MPa. The flow sensor is located at the outlet of the nanofiltration membrane permeate, and the nanofiltration membrane flux is 15 LMH~25 LMH. The concentration sensor detects the concentration of suspended solids in the liquid. The concentration sensor is respectively installed at the inlet of the microfiltration membrane, the inlet of the nanofiltration membrane, and the inlet of the chromatography system. The material inlet concentration at the microfiltration membrane inlet is 30% Brix to 35% Brix; the material inlet concentration at the nanofiltration membrane inlet is 30% Brix to 38% Brix; and the material inlet concentration at the chromatography system inlet is 30% Brix to 40% Brix. The temperature sensors are respectively installed at the microfiltration membrane inlet and the microfiltration membrane permeate outlet, the nanofiltration membrane inlet and the nanofiltration membrane permeate outlet, the chromatographic system inlet and the chromatographic column purified liquid outlet; each temperature detection threshold is the control temperature of the above-mentioned micron-level microfiltration treatment, nano-level nanofiltration treatment and moving bed chromatographic system column temperature. The chromatographic resolution is automatically detected by the moving bed chromatography (SMB) system to ensure that the resolution R ≥ 1.5.

[0015] Preferably, the retentate produced by the membrane microfiltration and nanofiltration in step four, as well as the impurity enrichment produced by the deep separation and purification of the moving bed chromatography system in step five, can be refluxed back to step two or step four.

[0016] Compared with the prior art, the advantages and positive effects of the present invention are as follows: This application discloses a method for preparing high-purity sorbitol from starch. The method involves steps such as starch hydrolysis to glucose, catalytic hydrogenation, pretreatment, membrane separation purification, chromatographic purification, post-treatment of the purified solution, and finished product testing. This method effectively solves the problems of low purification efficiency and limited purity improvement associated with single separation technologies. The final sorbitol product has a purity of ≥98.5%, reaching up to 99.2%, fully meeting the high-purity requirements of functional foods, special medical foods, and pharmaceutical preparations, significantly expanding the application scenarios of sorbitol. Compared to traditional crystallization and recrystallization purification processes, the combined membrane separation and chromatographic separation process of this invention significantly improves separation efficiency, eliminating the need for repeated crystallization operations and greatly reducing process energy consumption. Simultaneously, through online acquisition and intelligent dynamic control of multiple parameters throughout the entire process, separation process parameters can be optimized in real time, effectively avoiding the impact of material fluctuations on the separation effect, ensuring long-term stable and efficient operation of the entire separation and purification process, and reducing manual operation costs and equipment maintenance costs. In addition, the retentate containing unreacted raw materials and some products generated in the membrane separation stage, as well as the impurity enrichment liquid generated in the chromatographic separation stage, are all recycled back to the preceding process for reuse. This achieves closed-loop and efficient utilization of raw materials, reduces raw material waste and waste liquid discharge, and significantly reduces overall production costs while improving product yield. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 The purity determination results are for the sorbitol prepared in Example 1; Figure 2 The purity determination results are for the sorbitol prepared in Example 2; Figure 3 The results show the purity determination of the sorbitol prepared in Example 3. Detailed Implementation

[0019] To better understand the above-mentioned objectives, features, and advantages of the present invention, the present invention will be further described below in conjunction with the accompanying drawings and embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.

[0020] Numerous specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways than those described herein, and therefore the invention is not limited to the specific embodiments disclosed in the following specification.

[0021] This application includes corn starch, potato starch, rice starch, α-amylase, saccharifying enzyme, ruthenium-based catalyst, high-purity hydrogen, sodium hydroxide, ceramic microfiltration membrane (0.1 μm pore size, Al2O3 material), polyamide composite nanofiltration membrane (200 Da molecular weight cutoff, negatively charged surface), cation exchange resin, anion exchange resin, and activated carbon (0.5%). All of the above raw materials were purchased from the market and used directly. Example 1, such as Figure 1 As shown, a method for preparing high-purity sorbitol from starch includes the following specific steps: Starch hydrolysis to prepare glucose: Weigh 500 g of corn starch, add 500 mL of deionized water, and stir well to make starch slurry; add 2.0 g of α-amylase (0.4% w / w of starch mass), and liquefy and hydrolyze for 2.5 h at 85℃ and pH 6.2 to obtain dextrin solution; then add saccharifying enzyme (0.6% w / w of starch mass) to the dextrin solution, and continue saccharification and hydrolysis for 5 h at 60℃ and pH 4.5 to obtain glucose solution.

[0022] Catalytic hydrogenation: The glucose solution obtained above was concentrated to 35% by mass and transferred to a high-pressure reactor. Ruthenium-based catalyst was added (the amount added was 6% w / w of the dry glucose mass). Hydrogen gas was introduced to the system pressure of 4 MPa, the temperature was raised to 125℃, the stirring speed was controlled at 700 rpm and the hydrogen flow rate was 0.6 L / min, and the reaction was maintained at this temperature for 4 h. After the reaction was completed, the catalyst in the system was removed by filtration to obtain crude sorbitol solution.

[0023] Pretreatment: The temperature of the above crude sorbitol solution was adjusted to 42℃, and the pH of the system was adjusted to 7.2 using a 10% sodium hydroxide solution. After standing for 30 min, a small amount of catalyst residue precipitate was removed from the system to obtain the pretreated crude sorbitol solution for later use.

[0024] Membrane separation and purification: (1) Micron-level filtration: The pretreated crude sorbitol solution was passed into a ceramic microfiltration membrane device. A ceramic microfiltration membrane with a pore size of 0.1 μm and made of Al2O3 was used to filter the system under the conditions of operating pressure of 0.4 MPa and temperature of 42℃ to remove polysaccharides and residual catalyst particles. (2) Nanofiltration: The microfiltration permeate is passed into a nanofiltration membrane device. A polyamide composite nanofiltration membrane with a molecular weight cutoff of 200 Da and a negatively charged surface is used for separation under the conditions of operating pressure of 1.9 MPa and temperature of 45℃ to remove some unreacted glucose and mannitol impurities in the system and obtain sorbitol purified initial solution.

[0025] Chromatographic separation and purification: The above-mentioned purified sorbitol initial solution was passed into a moving bed chromatography (SMB) system for further purification. The chromatographic column was packed with a strong acid styrene-based cation exchange resin with a particle size of 120 μm to 180 μm and an exchange capacity of 4.8 mmol / g. The moving bed chromatography system adopted a 5-column tandem mode, with deionized water as the eluent and the column temperature controlled at 88℃. The target eluent was collected to obtain the purified sorbitol solution.

[0026] Post-treatment of the refined liquor: The above sorbitol refined liquor was fed into a vacuum concentrator and concentrated to a solid content of 70%; 0.5% (w / w, based on the mass of the concentrated liquor) of activated carbon was added to the concentrated liquor, and the liquor was kept at 60℃ for 30 min for decolorization. The activated carbon was then removed by filtration; the decolorized material was then subjected to desalting treatment by cation exchange resin and anion exchange resin in sequence; the desalted material was then spray-dried to obtain the sorbitol product.

[0027] Purity testing: The purity of the prepared sorbitol product was determined by high performance liquid chromatography (HPLC). Three parallel measurements yielded purity values ​​of 98.4%, 98.5%, and 98.8%, with an average value of 98.6%. The purity test results are as follows: Figure 1 As shown.

[0028] Example 2, as Figure 2 As shown, a method for preparing high-purity sorbitol from starch includes the following specific steps: Starch hydrolysis to prepare glucose: Weigh 700 g of potato starch, add 700 mL of deionized water, and stir well to make starch slurry; add 4.2 g of α-amylase (0.6% w / w of starch mass), and liquefy and hydrolyze for 3 h at 88℃ and pH 6.5 to obtain dextrin solution; then add saccharifying enzyme (0.7% w / w of starch mass) to the dextrin solution, and continue saccharification and hydrolysis for 6 h at 62℃ and pH 4.8 to obtain glucose solution.

[0029] Catalytic hydrogenation: The glucose solution obtained above was concentrated to 35% by mass and transferred to a high-pressure reactor. Ruthenium-based catalyst was added (8% w / w of dry glucose mass). Hydrogen gas was introduced to a system pressure of 4 MPa, and the temperature was raised to 120°C. The stirring speed was controlled at 700 rpm and the hydrogen flow rate at 0.6 L / min. The reaction was maintained at this temperature for 3.5 h. After the reaction was completed, the catalyst in the system was removed by filtration to obtain crude sorbitol solution.

[0030] Pretreatment: The temperature of the above crude sorbitol solution was adjusted to 40℃, and the pH of the system was adjusted to 7.2 using a 10% sodium hydroxide solution. After standing for 30 min, a small amount of catalyst residue precipitate was removed from the system to obtain the pretreated crude sorbitol solution for later use.

[0031] Membrane separation and purification: (1) Micron-level filtration: The pretreated crude sorbitol solution was passed into a ceramic microfiltration membrane device. A ceramic microfiltration membrane with a pore size of 0.1 μm and a material of Al2O3 was used for filtration under the conditions of operating pressure of 0.6 MPa and temperature of 38℃ to remove polysaccharides and residual catalyst particles from the system. (2) Nanofiltration: The microfiltration permeate is passed into a nanofiltration membrane device. A polyamide composite nanofiltration membrane with a molecular weight cutoff of 200 Da and a negatively charged surface is used for separation under the conditions of operating pressure of 1.9 MPa and temperature of 45℃ to remove some unreacted glucose and mannitol impurities in the system and obtain sorbitol purified initial solution.

[0032] Chromatographic separation and purification: The above-mentioned purified sorbitol initial solution was passed into a moving bed chromatography (SMB) system for further purification. The chromatographic column was packed with a strong acid styrene-based cation exchange resin with a particle size of 120 μm to 180 μm and an exchange capacity of 4.8 mmol / g. The moving bed chromatography system adopted a 5-column tandem mode, with deionized water as the eluent and the column temperature controlled at 90℃. The target eluent was collected to obtain the purified sorbitol solution.

[0033] Post-treatment of the refined liquor: The above sorbitol refined liquor was fed into a vacuum concentrator and concentrated to a solid content of 70%; 0.5% (w / w, based on the mass of the concentrated liquor) of activated carbon was added to the concentrated liquor, and the liquor was kept at 65°C for 30 min for decolorization, and the activated carbon was removed by filtration; the decolorized material was then subjected to desalting treatment by cation exchange resin and anion exchange resin in sequence; the desalted material was then spray-dried to obtain the sorbitol product.

[0034] Purity testing: The purity of the prepared sorbitol product was determined by high performance liquid chromatography (HPLC). Three parallel measurements yielded purity values ​​of 98.5%, 98.9%, and 99.2%, with an average value of 98.9%. The purity test results are as follows: Figure 2 As shown.

[0035] Example 3, as Figure 3 As shown, a method for preparing high-purity sorbitol from starch includes the following specific steps: Starch hydrolysis to prepare glucose: Weigh 1000 g of rice starch, add 1000 mL of deionized water, and stir well to make starch slurry; add 8.0 g of α-amylase (0.8% w / w of starch mass), and liquefy and hydrolyze for 3.5 h at 90℃ and pH 6.8 to obtain dextrin solution; then add saccharifying enzyme (0.8% w / w of starch mass) to the dextrin solution, and continue saccharification and hydrolysis for 7 h at 65℃ and pH 5.0 to obtain glucose solution.

[0036] Catalytic hydrogenation: The glucose solution obtained above was concentrated to 35% by mass and transferred to a high-pressure reactor. Ruthenium-based catalyst was added (the amount added was 10% w / w of the dry glucose mass). Hydrogen gas was introduced to the system pressure of 4 MPa, the temperature was raised to 130℃, the stirring speed was controlled at 700 rpm and the hydrogen flow rate was 0.6 L / min, and the reaction was maintained at this temperature for 5 h. After the reaction was completed, the catalyst in the system was removed by filtration to obtain crude sorbitol solution.

[0037] Pretreatment: The temperature of the above crude sorbitol solution was adjusted to 45℃, and the pH of the system was adjusted to 7.2 using a 10% sodium hydroxide solution. After standing for 30 min, a small amount of catalyst residue precipitate was removed from the system to obtain the pretreated crude sorbitol solution for later use.

[0038] Membrane separation and purification: (1) Micron-level filtration: The pretreated crude sorbitol solution was passed into a ceramic microfiltration membrane device. A ceramic microfiltration membrane with a pore size of 0.1 μm and a material of Al2O3 was used to filter the system under the conditions of operating pressure of 0.8 MPa and temperature of 45℃ to remove polysaccharides and residual catalyst particles. (2) Nanofiltration: The microfiltration permeate is passed into a nanofiltration membrane device. A polyamide composite nanofiltration membrane with a molecular weight cutoff of 200 Da and a negatively charged surface is used for separation under the conditions of operating pressure of 1.9 MPa and temperature of 45℃ to remove some unreacted glucose and mannitol impurities in the system and obtain sorbitol purified initial solution.

[0039] Chromatographic separation and purification: The above-mentioned purified sorbitol initial solution was passed into a moving bed chromatography (SMB) system for further purification. The chromatographic column was packed with a strong acid styrene-based cation exchange resin with a particle size of 120 μm to 180 μm and an exchange capacity of 4.8 mmol / g. The moving bed chromatography system adopted a 5-column tandem mode, with deionized water as the eluent and the column temperature controlled at 92℃. The target eluent was collected to obtain the purified sorbitol solution.

[0040] Post-treatment of the refined liquor: The above sorbitol refined liquor was fed into a vacuum concentrator and concentrated to a solid content of 70%; 0.5% (w / w, based on the mass of the concentrated liquor) of activated carbon was added to the concentrated liquor, and the liquor was kept at 70°C for 30 min for decolorization, and the activated carbon was removed by filtration; the decolorized material was then subjected to desalting treatment by cation exchange resin and anion exchange resin in sequence; the desalted material was then spray-dried to obtain the sorbitol product.

[0041] Purity testing: The purity of the prepared sorbitol product was determined by high-performance liquid chromatography (HPLC). Three parallel measurements yielded purity values ​​of 98.8%, 98.4%, and 99.2%, with an average value of 98.8%. The purity test results are shown below. Figure 3 As shown The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments that can be applied to other fields. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A method for preparing high purity sorbitol from starch, characterized by, The specific steps are as follows: Step 1: Preparation of glucose from starch hydrolysis: Using starch as raw material, after adding deionized water to make a slurry, α-amylase is added sequentially for liquefaction hydrolysis, and saccharifying enzyme is added for saccharification hydrolysis to obtain glucose solution; Step 2: Catalytic hydrogenation: The glucose solution obtained in Step 1 is concentrated to obtain a glucose concentrate, which is then transferred to a high-pressure reactor. A ruthenium-based catalyst is added, and hydrogen gas is introduced to carry out a hydrogenation reduction reaction. After the reaction is completed, the catalyst is removed by filtration to obtain a crude sorbitol solution. Step 3: Pretreatment: Adjust the temperature and pH of the crude sorbitol solution obtained in step two, let it stand and remove the precipitate to obtain the pretreated crude sorbitol solution; Step 4: Membrane separation and purification: The crude sorbitol solution pretreated in Step 3 is subjected to micron-level microfiltration and nanofiltration in sequence to remove impurities and obtain the purified sorbitol initial solution. Step 5: Chromatographic separation and purification: The sorbitol purified initial solution obtained in Step 4 is passed into a moving bed chromatography system for deep separation and purification to obtain the sorbitol purified solution; Step 6: Post-treatment of the purified liquor: The sorbitol purified liquor obtained in Step 5 is subjected to vacuum concentration, activated carbon decolorization, ion exchange resin desalination, and spray drying in sequence to obtain the sorbitol product. Step 7: Finished product testing: The purity of sorbitol in the finished sorbitol product is determined by high performance liquid chromatography.

2. A process for the preparation of high purity sorbitol from starch as claimed in claim 1 wherein, In step one, the starch is any one of corn starch, potato starch or rice starch; the ratio of starch to deionized water is 500 g:500 mL to 1000 g:1000 mL. The amount of α-amylase added is 0.6% to 0.8% of the starch mass; the liquefaction and hydrolysis temperature is 85℃ to 90℃, the liquefaction and hydrolysis pH is 6.2 to 6.8, and the liquefaction and hydrolysis time is 2.5 h to 3.5 h. The amount of saccharifying enzyme added is 0.6% to 0.8% of the starch mass; the saccharification and hydrolysis temperature is 60℃ to 65℃, the saccharification and hydrolysis pH is 4.5 to 5.0, and the saccharification and hydrolysis time is 5 h to 7 h.

3. A process for the preparation of high purity sorbitol from starch as claimed in claim 1 wherein, In step two, the amount of ruthenium-based catalyst added is 6% to 10% of the glucose mass in the glucose concentrate; the hydrogen pressure for the hydrogenation reduction reaction is 4 MPa, the reaction temperature is 110℃ to 130℃, the stirring speed is 700 rpm, the hydrogen flow rate is 0.6 L / min, and the reaction time is 3.5 h to 5 h.

4. A process for the preparation of high purity sorbitol from starch as claimed in claim 1 wherein, In step three, the temperature and pH of the crude sorbitol solution obtained in step two are adjusted as follows: the temperature of the crude sorbitol solution is adjusted to 38℃~45℃, and the pH is adjusted to 7.2 using a 10% sodium hydroxide solution; the standing time is 30 min.

5. A process for the preparation of high purity sorbitol from starch as claimed in claim 1 wherein, In step four, the micron-level microfiltration treatment uses an Al2O3 ceramic microfiltration membrane with a pore size of 0.1 μm, a treatment temperature of 38℃~45℃, and an operating pressure of 0.4 MPa~0.8 MPa. The micron-level microfiltration treatment is used to remove polysaccharides and residual catalyst particles. The nano-level nanofiltration treatment uses a polyamide composite nanofiltration membrane with a molecular weight cutoff of 200 Da and a negatively charged surface, a treatment temperature of 45℃, and an operating pressure of 1.9 MPa. The nano-level nanofiltration treatment is used to remove unreacted glucose and mannitol impurities.

6. A process for the preparation of high purity sorbitol from starch as claimed in claim 1 wherein, In step five, the moving bed chromatography system adopts a 5-column tandem mode, with the chromatographic column filled with a strong acid styrene-based cation exchange resin. The resin particle size is 120 μm to 180 μm and the exchange capacity is 4.8 mmol / g. The eluent for chromatographic separation is deionized water, and the column temperature is controlled at 88℃ to 92℃.

7. A process for the preparation of high purity sorbitol from starch as claimed in claim 1 wherein, In step six, the endpoint of the sorbitol purified solution concentration under reduced pressure is that the solid content of the sorbitol purified solution is not less than 70%; the amount of activated carbon added is 0.5% of the mass of the concentrated sorbitol purified solution; the decolorization temperature is 60℃~70℃ and the decolorization time is 30 min. The ion exchange resin desalination operation involves sequentially processing with cation exchange resin and anion exchange resin.

8. The process for preparing high purity sorbitol from starch as claimed in claim 1 wherein, The retentate produced by the membrane microfiltration and nanofiltration processes in step four, as well as the impurity enrichment produced by the deep separation and purification of the moving bed chromatography system in step five, can all be refluxed back to step two or step four.

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