Method for preparing polyhydric alcohol by utilizing erythritol nanofiltration trapped fluid and chromatographic raffinate

Abstract

The invention belongs to the technical field of sugar alcohol preparation, and relates to a method for preparing polyhydric alcohol by utilizing erythritol nanofiltration trapped fluid and chromatographic raffinate, which comprises the following steps: sequentially carrying out first decoloration, first ion exchange and evaporation pretreatment on mixed liquor of the erythritol nanofiltration trapped fluid and the chromatographic raffinate to obtain sugar liquor with the concentration of 50-55% (w / w), and then carrying out hydrotreating to obtain the polyhydric alcohol with the concentration of 50-55% (w / w). The hydrogenation treatment temperature is 130-145 DEG C, the pH value of the hydrogenation reaction feed liquid is 5.5-6.5, and the hydrogenation reaction pressure is 6.2-8.0 MPa; the hydrogenated liquid is sequentially subjected to secondary decoloration, secondary ion exchange and mixed bed process treatment, impurities are removed, and then an evaporator is used for concentration treatment to obtain a liquid polyhydric alcohol product meeting industrial requirements. According to the method, the utilization rate of the erythritol waste mother liquor is increased, the added value of the product is increased, and the treatment load of a sewage system is reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of sugar alcohol preparation, and particularly relates to a method for preparing polyols by using the nanofiltration retentate of erythritol and the raffinate of chromatography. Background Art

[0002] Erythritol is prepared from high-quality starch. Through the processes of enzymatic liquefaction, saccharification, filtration, decolorization, sugar nanofiltration, and evaporation, high-purity glucose syrup (glucose syrup content ≥ 99%) is obtained. Then, erythritol solution is obtained through fermentation, and crystalline erythritol is obtained through processes such as membrane filtration, alcohol nanofiltration, primary crystallization, decolorization, ion exchange, and secondary crystallization. Among them, the retentate produced in the alcohol nanofiltration process is directly discharged as sewage, and its main components are erythritol (≤30%), maltose syrup (15 - 25%), and oligosaccharides (35 - 65%); the raffinate obtained by softening and chromatographing the primary mother liquor for desalting and impurity removal is also directly discharged as sewage, and its main components are erythritol (≤20%), maltose syrup (20 - 30%), and oligosaccharides (30 - 70%).

[0003] To improve the added value of the nanofiltration retentate of erythritol and the raffinate of chromatography (hereinafter collectively referred to as erythritol waste mother liquor), a method for separating and purifying erythritol from the mother liquor after multiple crystallizations of erythritol is disclosed in the patent with the publication number CN102603478A. The inventive method dilutes the mother liquor after multiple crystallizations of erythritol with pure water, and then uses ultrafiltration membrane and nanofiltration membrane technologies to remove impurities and purify the mother liquor after multiple crystallizations of erythritol. Combined with activated carbon decolorization and ion exchange technology, qualified crystalline erythritol products are produced at one time. Its specific steps include pretreatment, ultrafiltration treatment, nanofiltration treatment, activated carbon decolorization, ion exchange, concentration, and crystallization. The content of erythritol in the mother liquor after multiple crystallizations mentioned in this process is between 30% and 60%, and this patent does not mention the treatment of erythritol waste mother liquor with a lower content of erythritol.

[0004] The mother liquor of erythritol production has attracted industry attention, and multiple invention patent applications for the treatment of erythritol mother liquor have been made public. Among them, CN102826958A and CN102964213A mainly purify the mother liquor through processes such as decolorization, membrane filtration, and ion exchange, and then recover erythritol in the mother liquor through concentration and crystallization. CN102826959A recovers erythritol crystals by adding organic solvents to the mother liquor. CN103373901A inoculates a special yeast strain in the mother liquor, consumes other components in the mother liquor through cultivation, improves the purity of erythritol in the mother liquor, and then recovers erythritol through purification and concentration. The application of CN102742761A directly uses the decolorized erythritol mother liquor as a cement retarder. However, the above patent applications mainly focus on the process technology of recovering erythritol from the mother liquor and are not applicable to the disposal of existing erythritol waste mother liquor, and the erythritol waste mother liquor has not been fully utilized. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a method for preparing polyols by using erythritol nanofiltration retentate and chromatographic raffinate. The mixed solution of erythritol nanofiltration retentate and chromatographic raffinate is sequentially subjected to activated carbon decolorization, ion exchange, concentration, and hydrogenation treatment to obtain the required polyol hydrogenation solution, and the hydrogenation solution is further subjected to activated carbon decolorization, ion exchange, mixed bed exchange, and concentration to obtain a polyol product meeting industry requirements.

[0006] The present invention is realized as follows: A method for preparing polyols by using erythritol nanofiltration retentate and chromatographic raffinate is provided, including the following steps: Step 1: The mixed solution of the collected erythritol nanofiltration retentate and chromatographic raffinate is sequentially passed through first decolorization, first ion exchange, and evaporation pretreatment to obtain a sugar solution with a mass percentage of 50-55%, and then hydrogenation treatment is carried out. The temperature of the hydrogenation treatment is 130-145 °C, the pH value of the hydrogenation reaction feed liquid is 5.5-6.5, the hydrogenation reaction pressure is 6.2-8.0 MPa, and the conversion rate of hydrogenation is measured to be above 99.80%, and the content of reducing sugar in the hydrogenation solution is below 0.15%; Step 2: The hydrogenated hydrogenation solution is sequentially passed through second decolorization, second ion exchange, and mixed bed processes to remove impurities, and then concentrated by an evaporator to obtain liquid polyols; in the liquid polyols, the content of maltitol is 14.94-29.90%, the content of erythritol is ≤24.93%, the content of oligosaccharide alcohols is 51.00-60.00%, and the content of reducing sugar is 0.10-0.20%.

[0007] Compared with the prior art, the method for preparing polyols using the erythritol nanofiltration retentate and chromatographic raffinate in the present invention obtains polyol products through the processes of refining - hydrogenation - re - refining of the erythritol waste mother liquor, increases the value of the erythritol waste mother liquor, reduces the treatment load on the sewage system, and stabilizes the entire production system. The method of the present invention also has the following characteristics: 1. Improve the utilization rate of the erythritol waste mother liquor and enhance the added value of the product; 2. Use the hydrogenation method to reduce the reducing sugar in the erythritol waste mother liquor, reduce the color risk during the process, and improve the quality of the final product; 3. Simple operation, short production cycle, comprehensive utilization of by - products, and good economic benefits. Specific Embodiments

[0008] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clear and understandable, the present invention will be further described in detail below with reference to the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0009] A preferred embodiment of the method for preparing polyols using the erythritol nanofiltration retentate and chromatographic raffinate in the present invention includes the following steps: Step 1: The mixed solution of the collected erythritol nanofiltration retentate and chromatographic raffinate is successively passed through the first decolorization, the first ion exchange, and evaporation pretreatment to obtain a sugar solution with a mass percentage of 50 - 55%. Then, hydrogenation treatment is carried out. The temperature of the hydrogenation treatment is 130 - 145 °C, the pH value of the hydrogenation reaction feed liquid is 5.5 - 6.5, the hydrogenation reaction pressure is 6.2 - 8.0 MPa, the conversion rate of hydrogenation is measured to be above 99.80%, and the reducing sugar content in the hydrogenated liquid is below 0.15%.

[0010] Step 2: The hydrogenated liquid is successively passed through the second decolorization, the second ion exchange, and the mixed bed process to remove impurities, and then concentrated by an evaporator to obtain liquid polyols; in the liquid polyols, the maltitol content is 14.94 - 29.9%, the erythritol content is ≤24.93%, the oligosaccharide alcohol content is 51.00 - 60.00%, and the reducing sugar content is 0.10 - 0.20%.

[0011] The following further illustrates the method for preparing polyols using the erythritol nanofiltration retentate and chromatographic raffinate in the present invention through specific embodiments.

[0012] Example 1

[0013] The first embodiment of the method for preparing polyols using the erythritol nanofiltration retentate and chromatographic raffinate in the present invention includes the following steps: Step 11: The mixed solution of the erythritol nanofiltration retentate and the chromatographic raffinate collected is successively passed through first decolorization, first ion exchange, and evaporation pretreatment to obtain a sugar solution with a mass percentage of 52.5%. Then, hydrogenation treatment is carried out. The temperature of the hydrogenation treatment is 135 °C, the pH value of the hydrogenation reaction feed liquid is 5.6, and the hydrogenation reaction pressure is 7.5 MPa. The conversion rate of hydrogenation is measured to be 99.87%, and the reducing sugar content in the hydrogenated liquid is 0.12%.

[0014] Step 12: The hydrogenated liquid is successively passed through second decolorization, second ion exchange, and mixed bed process to remove impurities, and then concentrated by an evaporator to obtain liquid polyol; in the liquid polyol, the maltitol content is 14.94%, the erythritol content is 24.93%, the oligosaccharide alcohol content is 60.00%, and the reducing sugar content is 0.13%, meeting the control index that the reducing sugar in the polyol product meeting industry requirements is lower than 0.3%.

[0015] Example 2

[0016] The second example of the method for preparing polyol using erythritol nanofiltration retentate and chromatographic raffinate of the present invention includes the following steps: Step 21: The mixed solution of the erythritol nanofiltration retentate and the chromatographic raffinate collected is successively passed through first decolorization, first ion exchange, and evaporation pretreatment to obtain a sugar solution with a mass percentage of 51.5%. Then, hydrogenation treatment is carried out. The temperature of the hydrogenation treatment is 138 °C, the pH value of the hydrogenation reaction feed liquid is 6.3, and the hydrogenation reaction pressure is 7.0 MPa. The conversion rate of hydrogenation is measured to be 99.84%, and the reducing sugar content in the hydrogenated liquid is 0.13%.

[0017] Step 22: The hydrogenated liquid is successively passed through second decolorization, second ion exchange, and mixed bed process to remove impurities, and then concentrated by an evaporator to obtain liquid polyol; in the liquid polyol, the maltitol content is 24.93%, the erythritol content is 19.90%, the oligosaccharide alcohol content is 55.00%, and the reducing sugar content is 0.17%, meeting the control index that the reducing sugar in the polyol product meeting industry requirements is lower than 0.3%.

[0018] Example 2

[0019] The third example of the method for preparing polyol using erythritol nanofiltration retentate and chromatographic raffinate of the present invention includes the following steps: Step 31: The mixed solution of the collected erythritol nanofiltration retentate and chromatographic raffinate is successively passed through the first decolorization, the first ion exchange, and evaporation pretreatment to obtain a sugar solution with a mass percentage of 50.0%. Then, hydrogenation treatment is carried out. The temperature of the hydrogenation treatment is 130°C, the pH value of the hydrogenation reaction feed liquid is 5.5, and the hydrogenation reaction pressure is 6.2 MPa. The conversion rate of hydrogenation is measured to be 99.91%, and the content of reducing sugar in the hydrogenated liquid is 0.10%.

[0020] Step 32: The hydrogenated liquid is successively passed through the second decolorization, the second ion exchange, and the mixed bed process to remove impurities, and then concentrated by an evaporator to obtain a liquid polyol. In the liquid polyol, the content of maltitol is 29.90%, the content of erythritol is 19.00%, the content of oligosaccharide alcohol is 51.00%, and the content of reducing sugar is 0.10%, meeting the control index that the reducing sugar in the polyol product meeting the industry requirements is less than 0.3%.

[0021] Example 4

[0022] The fourth example of the method for preparing polyol by using erythritol nanofiltration retentate and chromatographic raffinate in the present invention includes the following steps: Step 41: The mixed solution of the collected erythritol nanofiltration retentate and chromatographic raffinate is successively passed through the first decolorization, the first ion exchange, and evaporation pretreatment to obtain a sugar solution with a mass percentage of 55.0%. Then, hydrogenation treatment is carried out. The temperature of the hydrogenation treatment is 145°C, the pH value of the hydrogenation reaction feed liquid is 6.5, and the hydrogenation reaction pressure is 8.0 MPa. The conversion rate of hydrogenation is measured to be 99.82%, and the content of reducing sugar in the hydrogenated liquid is 0.15%.

[0023] Step 42: The hydrogenated liquid is successively passed through the second decolorization, the second ion exchange, and the mixed bed process to remove impurities, and then concentrated by an evaporator to obtain a liquid polyol. In the liquid polyol, the content of maltitol is 20.90%, the content of erythritol is 22.90%, the content of oligosaccharide alcohol is 56.00%, and the content of reducing sugar is 0.20%, meeting the control index that the reducing sugar in the polyol product meeting the industry requirements is less than 0.3%.

[0024] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing polyols using erythritol nanofiltration retentate and chromatography raffinate, characterized in that: The steps include: Step 1, the mixed solution of the collected erythritol nanofiltration retentate and the chromatographic raffinate is subjected to a first decolorization, a first ion exchange, and an evaporation pretreatment in sequence to obtain a sugar solution with a mass percentage of 50-55%, and then subjected to a hydrogenation treatment, wherein the temperature of the hydrogenation treatment is 130-145° C., the pH value of the hydrogenation reaction liquid is 5.5-6.5, the hydrogenation reaction pressure is 6.2-8.0 MPa, the conversion rate of hydrogenation is determined to be above 99.80%, and the reducing sugar content in the hydrogenated liquid is obtained to be below 0.15%; Step 2: The hydrogenated liquid after hydrogenation is sequentially subjected to a second decolorization, a second ion exchange, and a mixed bed process to remove impurities, and then concentrated using an evaporator to obtain a liquid polyol; in the liquid polyol, the maltitol content is 14.94-29.90%, the erythritol content is ≤24.93%, the oligosaccharide alcohol content is 51.00-60.00% and the reducing sugar content is 0.10-0.20%.

2. The method for preparing polyols using erythritol nanofiltration retentate and chromatography raffinate as claimed in claim 1, characterized in that: The steps include: Step 11, the mixed solution of the collected erythritol nanofiltration retentate and the chromatographic raffinate is subjected to a first decolorization, a first ion exchange, and an evaporation pretreatment in sequence to obtain a sugar solution with a mass percentage of 52.5%, and then subjected to a hydrogenation treatment, the temperature of the hydrogenation treatment is 135° C., the pH value of the hydrogenation reaction liquid is 5.6, the hydrogenation reaction pressure is 7.5 MPa, the conversion rate of hydrogenation is measured to be 99.87%, and the reducing sugar content in the hydrogenated liquid is 0.12%; Step 12: The hydrogenated liquid after hydrogenation is sequentially subjected to a second decolorization, a second ion exchange, and a mixed bed process to remove impurities, and then concentrated using an evaporator to obtain a liquid polyol; in the liquid polyol, the maltitol content is 14.94%, the erythritol content is 24.93%, the oligosaccharide alcohol content is 60.00%, and the reducing sugar content is 0.13%.

3. The method for preparing polyols by using erythritol nanofiltration retentate and chromatography raffinate as claimed in claim 1, characterized in that: The steps include: Step 21, the mixed solution of the collected erythritol nanofiltration retentate and the chromatographic raffinate is subjected to a first decolorization, a first ion exchange, and an evaporation pretreatment in sequence to obtain a sugar solution with a mass percentage of 51.5%, and then subjected to a hydrogenation treatment, the temperature of the hydrogenation treatment is 138° C., the pH value of the hydrogenation reaction liquid is 6.3, the hydrogenation reaction pressure is 7.0 MPa, the hydrogenation conversion rate is measured to be 99.84%, and the reducing sugar content in the hydrogenated liquid is 0.13%; Step 22: The hydrogenated liquid after hydrogenation is sequentially subjected to a second decolorization, a second ion exchange, and a mixed bed process to remove impurities, and then concentrated using an evaporator to obtain a liquid polyol; in the liquid polyol, the maltitol content is 24.93%, the erythritol content is 19.90%, the oligosaccharide alcohol content is 55.00%, and the reducing sugar content is 0.17%.

4. The method for preparing polyols by using erythritol nanofiltration retentate and chromatography raffinate as claimed in claim 1, characterized in that: The steps include: Step 31, the mixed solution of the collected erythritol nanofiltration retentate and the chromatographic raffinate is subjected to a first decolorization, a first ion exchange, and an evaporation pretreatment in sequence to obtain a sugar solution with a mass percentage of 50.0%, and then subjected to a hydrogenation treatment, the temperature of the hydrogenation treatment is 130° C., the pH value of the hydrogenation reaction liquid is 5.5, the hydrogenation reaction pressure is 6.2 MPa, the hydrogenation conversion rate is measured to be 99.91%, and the reducing sugar content in the hydrogenated liquid is 0.10%; Step 32: The hydrogenated liquid after hydrogenation is sequentially subjected to a second decolorization, a second ion exchange, and a mixed bed process to remove impurities, and then concentrated using an evaporator to obtain a liquid polyol; in the liquid polyol, the maltitol content is 29.90%, the erythritol content is 19.00%, the oligosaccharide alcohol content is 51.00%, and the reducing sugar content is 0.10%.

5. The method for preparing polyols using erythritol nanofiltration retentate and chromatography raffinate as claimed in claim 1, characterized in that: The steps include: Step 41, subjecting the collected mixed solution of the erythritol nanofiltration retentate and the chromatographic raffinate to a first decolorization, a first ion exchange, and an evaporation pretreatment in sequence to obtain a sugar solution with a mass percentage of 55.0%, and then subjecting the mixture to a hydrogenation treatment at a temperature of 145° C., a pH value of the hydrogenation reaction liquid of 6.5, a hydrogenation reaction pressure of 8.0 MPa, and a hydrogenation conversion rate of 99.82%, and obtaining a reducing sugar content of 0.15% in the hydrogenated solution; Step 42: The hydrogenated liquid after hydrogenation is sequentially subjected to a second decolorization, a second ion exchange, and a mixed bed process to remove impurities, and then concentrated using an evaporator to obtain a liquid polyol; in the liquid polyol, the content of maltitol is 20.90%, the content of erythritol is 22.90%, the content of oligosaccharide alcohol is 56.00%, and the content of reducing sugar is 0.20%.