Method for reducing the content of impurities in dehydrated sugar alcohols and use

Abstract

The present application relates to the field of dehydrated sugar alcohol purification, and discloses a method for reducing the impurity content in dehydrated sugar alcohol and application, the method comprising: (1) dissolving the dehydrated sugar alcohol crude product in an organic solvent and then performing crystallization; (2) performing solid-liquid separation on the mixed solution obtained in step (1), and then performing chromatographic separation on the obtained mother liquor. According to the present application, the impurities in the dehydrated sugar alcohol crude product can be selectively separated through crystallization and chromatographic separation. The method for reducing the impurity content in dehydrated sugar alcohol is simple in experimental device, mild in operation condition, obvious in impurity separation effect, and high in product purity. The dehydrated sugar alcohol after the above impurity reduction can be used for synthesizing polyol ester, and the obtained polyol ester has good performance indexes.

Description

Technical Field

[0001] This invention relates to the field of dehydrated sugar alcohol purification, specifically to a method and application for reducing the impurity content in dehydrated sugar alcohols. Background Technology

[0002] Isosorbide is an important biomass-based derivative chemical. As a safe, non-toxic, and renewable rigid-structure diol, it is widely used not only in pharmaceuticals, surfactants, and plastic additives, but also shows promise in the field of novel polymer materials. For example, isosorbide can replace traditional diols in modified polyester synthesis; it can replace bisphenol A and other diphenol compounds in polycarbonate synthesis, significantly improving the resin's light transmittance, weather resistance, impact resistance, and scratch resistance. Trace impurities in isosorbide can affect polymer color, molecular weight, glass transition temperature, hardness, and scratch resistance, therefore, strict requirements are placed on the impurities in isosorbide products used for polymerization. Most impurities in isosorbide are byproducts of the sorbitol dehydration process, exhibiting diversity and similar physicochemical properties, making removal difficult using traditional methods.

[0003] Currently reported synthetic routes for isosorbide mainly use sorbitol as a raw material and solid or liquid acids as catalysts for catalytic dehydration. Multiple dehydration pathways exist, often accompanied by side reactions. These include elimination reactions, substitution reactions, aldol condensation reactions, degradation, or polymerization between hexahydrol molecules or other dehydration intermediates. The liquid acid process, primarily concentrated sulfuric acid, is more commonly used industrially. This process suffers from equipment corrosion and a long process route. Byproducts include numerous dehydrated oligosaccharides, polyhydroxy compounds, aromatic furan rings, and residual acids, which, even after separation and purification, are insufficient to meet the requirements of polymerization production. Solid acids mainly consist of molecular sieves, ion exchange resins, metal phosphates, and heteropoly acids. While the solid acid process reduces the types of impurities compared to the sulfuric acid method, trace impurities are still unavoidable. Since these impurities are mostly polyhydroxy compounds with similar structures to isosorbide, they are difficult to remove completely by distillation or crystallization alone, affecting the performance of the polymerized product.

[0004] The main purification methods for isosorbide include recrystallization, evaporation, and distillation. For example, US15538301 discloses a method for producing and purifying high-purity dehydrated sugar alcohols. This method involves reacting the sugar alcohol in a reactor in the presence of an acid catalyst, evaporating the reaction product, cooling the evaporated product to remove water and obtain crude dehydrated sugar alcohol, and then introducing the crude dehydrated sugar alcohol into a melt crystallization process to obtain high-purity dehydrated sugar alcohol. However, this method requires sophisticated equipment, and other impurities in the sugar alcohol are not separated and characterized. US14441406 discloses a method for preparing high-purity anhydrous sugar alcohols by sequentially combining thin-film distillation and short-path distillation. Acid is added to hydrogenated sugar to convert it into anhydrous sugar alcohol, and then isosorbide with a purity of over 98% is obtained by sequentially using a combination of an external condenser-type scraped-film evaporator and an internal condenser-type short-path evaporator. However, information on the specific types of impurities is not obtained, and it is unclear whether the isosorbide meets the requirements for polymerization grade. CN101691376A discloses a method for purifying isosorbide using diol recrystallization. The method of purifying isosorbide by recrystallization of diols uses diols instead of ordinary non-reactive organic solvents. The diol solvents used do not need to be removed, simplifying the purification process, reducing solvent removal steps, and avoiding post-processing problems caused by low-boiling-point organic solvents in subsequent polymerization. However, the diol used is still present in the isosorbide product, which may affect subsequent polymerization. CN116554188A discloses a method for preparing isosorbide, using distillation for product purification. No solvent is added during separation and purification, making it more environmentally friendly. The isosorbide prepared by this invention achieves a purity of 99.5%, but the method and types of trace impurities are not specified, which may affect subsequent polymerization. CN114437099A discloses a method for preparing high-purity isosorbide and the obtained isosorbide. Using hexitol as a raw material, isosorbide is obtained through catalytic dehydration, followed by extraction, decolorization, and recrystallization to obtain high-purity isosorbide. No neutralization is required after the reaction, and desalting is unnecessary during product purification. Extraction separation is employed, eliminating the need for high-temperature vacuum distillation, thus reducing equipment investment and increasing separation efficiency. However, the process is lengthy, and the methods and types for separating trace impurities are not clearly defined. CN104822684B discloses a method for preparing color-stable isosorbide, which involves chromatographic separation. The main focus is on separating ionic species. A mixture of crude dehydrated hexyl alcohols is passed through a strong acid cation exchange resin, and size exclusion chromatography is used to separate the ionic species from other mixtures. The residue after separation is further decolorized, adsorbed, and processed in a fixed bed to obtain a product rich in one or more dehydrated hexyl alcohols. The patent does not specify the methods and types for separating trace impurities, nor their impact on the polymerization reaction. Summary of the Invention

[0005] The purpose of this invention is to overcome the problem that impurities in crude dehydrated sugar alcohols cannot be selectively separated in the prior art, and to provide a method and application for reducing the impurity content in dehydrated sugar alcohols. This method has the advantages of high impurity enrichment and separation and high selective separation of impurities.

[0006] To achieve the above objectives, a first aspect of the present invention provides a method for reducing the impurity content in dehydrated sugar alcohols, the method comprising:

[0007] (1) The crude dehydrated sugar alcohol is dissolved in an organic solvent and then crystallized.

[0008] (2) After solid-liquid separation of the mixture obtained in step (1), the resulting mother liquor is separated by chromatography.

[0009] A second aspect of the present invention provides the application of the method described in the first aspect in the synthesis of polyol esters.

[0010] The above technical solution achieves at least the following beneficial effects: This invention, through crystallization and chromatographic separation, can selectively separate impurities from crude dehydrated sugar alcohols. Furthermore, the method for reducing the impurity content in dehydrated sugar alcohols according to this invention involves simple experimental equipment, mild operating conditions, significant impurity separation effect, and high product purity. The dehydrated sugar alcohols with reduced impurities obtained through the above method can be used to synthesize polyol esters, and the resulting polyol esters exhibit excellent performance indicators. Detailed Implementation

[0011] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0012] The first aspect of the present invention provides a method for reducing the impurity content in dehydrated sugar alcohols, the method comprising:

[0013] (1) The crude dehydrated sugar alcohol is dissolved in an organic solvent and then crystallized.

[0014] (2) After solid-liquid separation of the mixture obtained in step (1), the resulting mother liquor is separated by chromatography.

[0015] During their research, the inventors of this invention discovered that crystallization and chromatographic separation can not only efficiently enrich impurities, but also selectively separate impurities from crude dehydrated sugar alcohols, thereby obtaining high-purity dehydrated sugar alcohols.

[0016] In this invention, preferably, the crude dehydrated sugar alcohol comprises dehydrated sugar alcohol and impurities; wherein, the dehydrated sugar alcohol can be a common dehydrated sugar alcohol in the art, for example, it can be at least one of isosorbide, isomannitol, isoadulol, dehydrated glucose, defructose and dehydrated mannitol; the impurities can be common impurities among the above-mentioned dehydrated sugar alcohols, for example, it can be at least one of levulinic acid, isomannitol, 1,5-dehydrated sorbitol, 2,6-dehydrated sorbitol, 2,5-dehydrated sorbitol and furanoic acid.

[0017] In this invention, preferably, the content of dehydrated sugar alcohol in the crude dehydrated sugar alcohol product is 90-99 wt% (for example, it can be any two values ​​from 90 wt%, 90.5 wt%, 91 wt%, 91.5 wt%, 92 wt%, 92.5 wt%, 93 wt%, 93.5 wt%, 94 wt%, 94.5 wt%, 95 wt%, 95.5 wt%, 96 wt%, 96.5 wt%, 97 wt%, 97.5 wt%, 98 wt%, 98.5 wt%, 99 wt%, or any value within that range); the content of impurities is 1-10 wt% (for example, it can be any two values ​​from 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, or any value within that range). It is understood that the lower the impurity content in the raw material, the better.

[0018] In this invention, the organic solvent can be a common solvent capable of dissolving dehydrated sugar alcohols. Preferably, the organic solvent is selected from at least one of methanol, ethanol, isopropanol, dichloromethane, chloroform, acetone, acetonitrile, methyl acetate, ethyl acetate, methyl tert-butyl ether, tetrahydrofuran, and xylene. More preferably, it is selected from at least two of these solvents, and even more preferably, it is selected from two of these solvents (e.g., methanol / ethyl acetate, ethanol / ethyl acetate, acetone / ethanol, acetone / acetonitrile, ethanol / acetonitrile, acetone / ethyl acetate, methanol / tetrahydrofuran, or isopropanol / ethyl acetate). When there are two organic solvents, the volume percentages of the two solvents are 10-90 vol% (e.g., 10 vol%, 15 vol%, 20 vol%, 25 vol%, 30 vol%, 35 vol%). The range of any two values ​​from 10 vol%, 40 vol%, 45 vol%, 50 vol%, 55 vol%, 60 vol%, 65 vol%, 70 vol%, 75 vol%, 80 vol%, 85 vol%, 90 vol%, and the values ​​within that range) and 10-90 vol% (for example, the range of any two values ​​from 10 vol%, 15 vol%, 20 vol%, 25 vol%, 30 vol%, 35 vol%, 40 vol%, 45 vol%, 50 vol%, 55 vol%, 60 vol%, 65 vol%, 70 vol%, 75 vol%, 80 vol%, 85 vol%, 90 vol%) and the values ​​within that range).

[0019] In this invention, preferably, the crystallization method is as follows:

[0020] S1. The first part of the crude dehydrated sugar alcohol is dissolved in an organic solvent and then subjected to the first crystallization.

[0021] S2. Take out the crystals from the first crystallization and mix the remaining mother liquor from the first crystallization with the second part of the dehydrated sugar alcohol crude product for a second crystallization;

[0022] Preferably, step S2 is performed at least once.

[0023] It is understood that "step S2 is performed at least once" means that step S2 is performed at least once during the crystallization process. For example, when step S2 is performed once, the specific crystallization operation is as follows: the first part of the crude dehydrated sugar alcohol is dissolved in an organic solvent and crystallized for the first time; the crystals from the first crystallization are taken out and the remaining mother liquor from the first crystallization is mixed with the second part of the crude dehydrated sugar alcohol for the second crystallization. When step S2 is performed twice, the specific crystallization operation is as follows: the first part of the crude dehydrated sugar alcohol is dissolved in an organic solvent and crystallized for the first time; the crystals from the first crystallization are taken out and the remaining mother liquor from the first crystallization is mixed with the second part of the crude dehydrated sugar alcohol for the second crystallization; the crystals from the second crystallization are taken out and the remaining mother liquor from the second crystallization is mixed with the third part of the crude dehydrated sugar alcohol for the third crystallization. The remaining number of times is performed follows the same pattern.

[0024] In this invention, preferably, the amount of the first portion of dehydrated sugar alcohol crude product used relative to 100 mL of organic solvent is 10-50 g (for example, it can be any two values ​​formed by 10 g, 15 g, 20 g, 25 g, 30 g, 35 g, 40 g, 45 g, 50 g, or any value within that range).

[0025] In this invention, preferably, step S2 is performed 1-3 times.

[0026] In this invention, preferably, the crystallization conditions include: a crystallization temperature of 0-15℃, preferably 4-10℃ (for example, any two values ​​from 4℃, 4.5℃, 5℃, 5.5℃, 6℃, 6.5℃, 7℃, 7.5℃, 8℃, 8.5℃, 9℃, 9.5℃, 10℃, or any value within that range); and a crystallization time of 2-30h, preferably 6-24h (for example, any two values ​​from 6h, 7h, 8h, 9h, 10h, 11h, 12h, 13h, 14h, 15h, 16h, 17h, 18h, 19h, 20h, 21h, 22h, 23h, 24h, or any value within that range). The conditions for the first and second crystallizations can each be independently within the above ranges and may be the same or different.

[0027] In this invention, preferably, the weight ratio of the crude dehydrated sugar alcohol used in the previous crystallization process to that in the subsequent crystallization process is 1:1-5.

[0028] In this invention, by crystallizing multiple times and adding crude dehydrated sugar alcohol before each crystallization cycle, the impurity content in the mother liquor increases. Then, by using appropriate organic solvents, specific impurities are enriched in the mother liquor, thereby increasing the selectivity of impurity separation and the purity of dehydrated sugar alcohol, and reducing the difficulty of impurity separation.

[0029] In this invention, preferably, the packing material used in the chromatographic separation is selected from at least one of neutral silica gel, neutral activated carbon, basic activated carbon, neutral alumina, basic alumina, ion exchange resin, and polystyrene microspheres; wherein, preferably, the average particle size of the packing material is 25-250 μm (for example, it can be any two values ​​formed by 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, 110 μm, 120 μm, 130 μm, 140 μm, 150 μm, 160 μm, 170 μm, 180 μm, 190 μm, 200 μm, 210 μm, 220 μm, 230 μm, 240 μm, 250 μm, or a value within that range).

[0030] In this invention, preferably, the chromatographic separation is performed at least once, preferably 1-3 times; the method for multiple chromatographic separations is to collect the eluent after the previous chromatographic separation and continue chromatographic separation.

[0031] In this invention, preferably, the eluent used in the chromatographic separation is selected from at least two of methanol, ethanol, dichloromethane, chloroform, acetone, acetonitrile, methyl acetate, ethyl acetate, methyl tert-butyl ether, and tetrahydrofuran; more preferably, two or three (e.g., methanol / ethyl acetate / dichloromethane, ethyl acetate / dichloromethane, methanol / chloroform, methanol / ethyl acetate / methyl tert-butyl ether, acetone / ethyl acetate / dichloromethane, methanol / dichloromethane, methanol / acetonitrile / ethanol); and even more preferably, two or three. Preferably, when two eluents are used, the volume percentages of the higher polarity solvent and the lower polarity solvent are 10-40 vol% (e.g., 10 vol%). The range formed by any two values ​​from 10%, 12vol%, 14vol%, 16vol%, 18vol%, 20vol%, 22vol%, 24vol%, 26vol%, 28vol%, 30vol%, 32vol%, 34vol%, 36vol%, 38vol%, 40vol%, and values ​​within that range) and 60-90vol% (e.g., 60vol%, 62vol%, 64vol%, 66vol%, 68vol%, 70vol%, 72vol%, 74vol%, 76vol%, 78vol%, 80vol%, 82vol%). The range formed by any two values ​​from 84 vol%, 86 vol%, 88 vol%, and 90 vol%, and the values ​​within that range); when there are three eluents, the volume contents of the high-polarity solvent, medium-polarity solvent, and low-polarity solvent in the eluent are 0-20 vol% (e.g., any two values ​​formed by any two values ​​from 0 vol%, 2 vol%, 4 vol%, 6 vol%, 8 vol%, 10 vol%, 12 vol%, 14 vol%, 16 vol%, 18 vol%, and 20 vol%), 10-20 vol% (e.g., 10 vol%, 11 vol%, 12 vol%), and 12 vol% respectively. The range of 10%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, and 20% vol%, and the values ​​within that range, and 60-90% vol% (e.g., a range of 60%, 62%, 64%, 66%, 68%, 70%, 72%, 74%, 76%, 78%, 80%, 82%, 84%, 86%, 88%, and 90% vol%). The terms "higher polarity," "lower polarity," "higher polarity," "medium polarity," and "lower polarity" mentioned above have no specific meaning; they only represent relative polarity.

[0032] In this invention, after multiple crystallizations, chromatographic separation is performed. During the chromatographic separation process, different packing materials and eluents are used to selectively separate impurities in the crude dehydrated sugar alcohol, which can effectively improve the purity and recovery rate of the product.

[0033] In this invention, preferably, the impurity is levulinic acid, and the crystallization conditions include: 10-25 vol% organic solvent A and 75-90 vol% organic solvent B; organic solvent A is selected from organic solvents with a polarity not lower than acetone (e.g., methanol or ethanol), and organic solvent B is selected from organic solvents with a polarity lower than acetone (e.g., ethyl acetate); the chromatographic separation conditions include: 10-15 vol% eluent a, 10-15 vol% eluent b, and 70-75 vol% eluent c used for chromatographic separation; eluent a is selected from organic solvents with a polarity higher than acetone (e.g., methanol or ethanol), eluent b is selected from organic solvents with a polarity not higher than acetone and not lower than methyl acetate (e.g., ethyl acetate), and eluent c is selected from organic solvents with a polarity lower than methyl acetate (e.g., dichloromethane).

[0034] Alternatively, the impurity is isomannitol, and the crystallization conditions include: 40-60 vol% organic solvent C and 40-60 vol% organic solvent D; organic solvent C is selected from organic solvents with a polarity not higher than acetone (e.g., acetone), and organic solvent D is selected from organic solvents with a polarity higher than acetone (e.g., acetonitrile or ethanol); the chromatographic separation conditions include: 15-20 vol% eluent d and 80-85 vol% eluent e used in chromatographic separation; eluent d is selected from organic solvents with a polarity not lower than methyl acetate (e.g., ethyl acetate or methanol), and eluent e is selected from organic solvents with a polarity lower than methyl acetate (e.g., dichloromethane or chloroform).

[0035] Alternatively, the impurity is 1,5-sorbitol, and the crystallization conditions include: 40-60 vol% organic solvent E and 40-60 vol% organic solvent F; organic solvent E is selected from organic solvents with a polarity not less than acetone (e.g., ethanol or acetone), and organic solvent F is selected from organic solvents with a polarity not less than methyl acetate (e.g., acetonitrile or ethyl acetate); the chromatographic separation conditions include: 10-20 vol% eluent f, 10-15 vol% eluent g, and 70-80 vol% eluent h used in chromatographic separation; eluent f is selected from organic solvents with a polarity not less than acetone (e.g., methanol or acetone), eluent g is selected from organic solvents with a polarity less than acetone and not less than methyl acetate (e.g., ethyl acetate), and eluent h is selected from organic solvents with a polarity less than methyl acetate (e.g., methyl tert-butyl ether or dichloromethane).

[0036] Alternatively, the impurity is 2,6-sorbitol, and the crystallization conditions include: 75-85 vol% organic solvent G and 15-25 vol% organic solvent H; organic solvent G is selected from organic solvents with a polarity not less than acetone (e.g., methanol), and organic solvent H is selected from organic solvents with a polarity less than acetone (e.g., tetrahydrofuran or ethyl acetate); the chromatographic separation conditions include: the eluent used for chromatographic separation is 10-20 vol% organic solvent with a polarity not less than acetone (e.g., methanol) and 80-90 vol% organic solvent with a polarity less than acetone (e.g., dichloromethane), or 10-20 vol% organic solvent with a polarity not less than methanol and a polarity less than acetonitrile (e.g., methanol), 10-30 vol% organic solvent with a polarity not less than acetonitrile (e.g., acetonitrile), and 60-70 vol% organic solvent with a polarity less than methanol and a polarity not less than acetone (e.g., ethanol).

[0037] Alternatively, the impurity is 2,5-sorbitol, and the crystallization conditions include: 85-90 vol% organic solvent I and 10-15 vol% organic solvent J; organic solvent I is selected from organic solvents with a polarity not less than acetone (e.g., ethanol or isopropanol), and organic solvent J is selected from organic solvents with a polarity less than acetone and not less than methyl acetate (e.g., ethyl acetate); the chromatographic separation conditions include: 10-15 vol% eluent i and 85-90 vol% eluent j used for chromatographic separation; eluent i is selected from organic solvents with a polarity not less than acetone (e.g., methanol), and eluent j is selected from organic solvents with a polarity less than methyl acetate (e.g., dichloromethane).

[0038] In a preferred embodiment of the present invention, the impurity is levulinic acid, and the crystallization conditions include: step S2 is performed once; the organic solvent is 10-25 vol% organic solvent A and 75-90 vol% organic solvent B; organic solvent A is selected from methanol, ethanol and isopropanol, and organic solvent B is ethyl acetate or methyl acetate; the chromatographic separation conditions include: chromatographic separation is performed once; the average particle size of the packing material is 75-150 μm; the eluent used in the chromatographic separation is 10-15 vol% eluent a, 10-15 vol% eluent b and 70-75 vol% eluent c; eluent a is selected from methanol, ethanol and isopropanol, eluent b is selected from ethyl acetate or methyl acetate, and eluent c is selected from dichloromethane or chloroform;

[0039] Alternatively, the impurity is isomannitol, and the crystallization conditions include: step S2 is performed twice; the organic solvent is 40-60 vol% organic solvent C and 40-60 vol% organic solvent D; organic solvent C is selected from acetone or methyl tert-butyl ether, and organic solvent D is one of methanol, ethanol, isopropanol, and acetonitrile; the chromatographic separation conditions include: chromatographic separation is performed once; the average particle size of the packing material is 48-150 μm; the eluent used in the chromatographic separation is 15-20 vol% eluent d and 80-85 vol% eluent e; eluent d is selected from methanol, ethanol, isopropanol, ethyl acetate, and methyl acetate, and eluent e is selected from dichloromethane or chloroform;

[0040] Alternatively, the impurity is 1,5-sorbitol, and the crystallization conditions include: step S2 is performed three times; the organic solvent is 40-60 vol% organic solvent E and 40-60 vol% organic solvent F; organic solvent E is selected from methanol, ethanol, isopropanol, and acetone, and organic solvent F is selected from methyl acetate, ethyl acetate, and acetonitrile; the chromatographic separation conditions include: chromatographic separation is performed once; the average particle size of the packing material is 38-150 μm; the eluent used in the chromatographic separation is 10-20 vol% eluent f, 10-15 vol% eluent g, and 70-80 vol% eluent h; eluent f is selected from methanol, ethanol, isopropanol, and acetone, eluent g is selected from methyl acetate or ethyl acetate, and eluent h is selected from dichloromethane, chloroform, and methyl tert-butyl ether;

[0041] Alternatively, the impurity is 2,6-sorbitol, and the crystallization conditions include: step S2 is performed three times; the organic solvent is 75-85 vol% organic solvent G and 15-25 vol% organic solvent H; organic solvent G is selected from methanol, ethanol and isopropanol, and organic solvent H is selected from methyl acetate, ethyl acetate and tetrahydrofuran; the chromatographic separation conditions include: chromatographic separation is performed once; the average particle size of the packing material is 48-150 μm; the eluent used in the chromatographic separation is 10-20 vol% methanol and 80-90 vol% dichloromethane or chloroform, or 10-20 vol% methanol, 10-30 vol% acetonitrile and 60-70 vol% ethanol;

[0042] Alternatively, the impurity is 2,5-sorbitol, and the crystallization conditions include: step S2 is performed three times; the organic solvent is 85-90 vol% organic solvent I and 10-15 vol% organic solvent J; organic solvent I is selected from methanol, ethanol, and isopropanol, and organic solvent J is methyl acetate or ethyl acetate; the chromatographic separation conditions include: chromatographic separation is performed twice; the average particle size of the packing material for the two chromatographic separations is 75-150 μm and 48-75 μm or 75-150 μm and 38-48 μm, respectively; the eluent used in the chromatographic separation is 10-15 vol% eluent i and 85-90 vol% eluent j; eluent i is selected from methanol, ethanol, and isopropanol, and eluent j is selected from dichloromethane or chloroform.

[0043] During their research, the inventors of this invention discovered that by limiting specific crystallization and chromatographic separation conditions, the aforementioned impurities can not only be more easily enriched in the mother liquor, thereby increasing the selectivity of impurity separation and the purity of dehydrated sugar alcohol, and reducing the difficulty of impurity separation, but also highly selectively separate impurities in crude dehydrated sugar alcohol, effectively improving product purity and recovery rate.

[0044] In a preferred embodiment of the present invention, the step before chromatographic separation further includes: taking the last filtration mother liquor and mixing it with 75-150μm and / or 150-250μm neutral silica powder, evaporating the solvent, and then introducing it into the chromatographic column for chromatographic separation.

[0045] In this invention, preferably, the crude dehydrated sugar alcohol can be prepared using methods commonly used in the art. For example, it can be prepared by mixing the sugar alcohol with a catalyst under vacuum to carry out a dehydration reaction; the product obtained after the dehydration reaction is completed is distilled to obtain the crude dehydrated sugar alcohol (i.e., dehydrated sugar alcohol distillate); or the product obtained after the dehydration reaction is completed is subjected to chromatographic separation to obtain the crude dehydrated sugar alcohol.

[0046] It is understood that the purpose of performing chromatographic separation on the product obtained after the dehydration reaction is to remove the heavy components in the product obtained after the dehydration reaction. The chromatographic separation packing can be a packing commonly used in the art for separating heavy components, such as neutral silica powder.

[0047] In this invention, preferably, the vacuum degree under the vacuum state is 10-300 mbar (for example, it can be any two values ​​formed by 10 mbar, 20 mbar, 40 mbar, 60 mbar, 80 mbar, 100 mbar, 120 mbar, 140 mbar, 160 mbar, 180 mbar, 200 mbar, 220 mbar, 240 mbar, 260 mbar, 280 mbar, and 300 mbar, and the values ​​within that range); the dehydration reaction conditions include: a reaction temperature of 115-150℃ (for example, it can be any two values ​​formed by 115℃, 120℃, 125℃, 130℃, 135℃, 140℃, 145℃, and 150℃, and the values ​​within that range); and a reaction time of 4-10 h (for example, it can be any two values ​​formed by 4 h, 5 h, 6 h, 7 h, 8 h, 9 h, and 10 h, and the values ​​within that range).

[0048] In this invention, preferably, the distillation conditions include: a distillation temperature of 150-260℃, more preferably 170-220℃ (for example, it can be any two values ​​formed by 170℃, 175℃, 180℃, 185℃, 190℃, 195℃, 200℃, 205℃, 210℃, 215℃, 220℃, or values ​​within that range); and a distillation pressure of 1-40 mbar, preferably 2-10 mbar (for example, it can be 2 mbar, 2.5 mbar, 3 mbar, 3.5 mbar, 4 mbar, 4.5 mbar, 5 mbar, 5...). The distillation time is 1-6 hours, preferably 2-4 hours (e.g., any two values ​​from 5 mbar, 6 mbar, 6.5 mbar, 7 mbar, 7.5 mbar, 8 mbar, 8.5 mbar, 9 mbar, 9.5 mbar, 10 mbar, or any value within that range);

[0049] In this invention, preferably, the sugar alcohol can be a sugar alcohol commonly used in the art for dehydration, for example, it can be at least one of sorbitol, glucose, fructose, mannitol, xylitol and idole.

[0050] In this invention, preferably, the catalyst can be a catalyst commonly used in the dehydration process of sugar alcohols, for example, it can be at least one of sulfuric acid, hydrochloric acid, methanesulfonic acid, p-toluenesulfonic acid, glacial acetic acid, sulfonic acid resin, hydrogen-form ion exchange resin, phosphotungstic acid and hydrotalcite.

[0051] In this invention, preferably, the mass ratio of the catalyst to the sugar alcohol is 0.1-10:100, more preferably 0.5-5.5:100 (for example, it can be any two ratios from 0.5:100, 0.8:100, 1:100, 1.2:100, 1.4:100, 1.6:100, 1.8:100, 2:100, 2.3:100, 2.5:100, 2.8:100, 3:100, 3.5:100, 4:100, 4.5:100, 5:100, 5.5:100, forming a range or ratios within that range).

[0052] A second aspect of the present invention provides the application of the method described in the first aspect in the synthesis of polyol esters.

[0053] In this invention, preferably, the dehydrated sugar alcohol is a diol (such as isosorbide). This invention also relates to a method for synthesizing a polyol ester, the method comprising: preparing a dehydrated sugar alcohol according to the aforementioned method; and contacting the obtained dehydrated sugar alcohol with a diester to perform a transesterification reaction. The diester may be polyethylene terephthalate.

[0054] The present invention will be described in detail below through examples. In the following examples, the sorbitol raw material is a commercially available product from Innochem with a purity of 95 wt%; brand A is a commercial sample of Innochem brand isosorbitol A20143; and product B is a commercial sample of Yuanye brand isosorbitol S28319-500g.

[0055] The isosorbide content obtained from crystallization, the isosorbide content in the mother liquor, and the impurity content in the mother liquor were obtained by high performance liquid chromatography with internal standard method; the purity was determined by high performance liquid chromatography.

[0056] Isosorbide recovery rate in the mother liquor after the last crystallization = (mass of isosorbide crystals filtered from the mother liquor after multiple crystallizations + mass of isosorbide fraction obtained by column chromatography) / total mass of isosorbide in the multiple added isosorbide distillates;

[0057] The recovery rate of levulinic acid = the amount of levulinic acid crystals / the total mass of levulinic acid contained in the isosorbide distillate;

[0058] Recovery rate of a certain impurity = mass of the certain impurity obtained by column chromatography / total mass of the certain impurity contained in the isosorbide distillate added multiple times.

[0059] The isosorbide distillate comprises: 95 wt% isosorbide, 0.5 wt% levulinic acid, 0.5 wt% isomannitol, 1.5 wt% 1,5-ahydrosorbitol, 1 wt% 2,6-ahydrosorbitol, and 1.5 wt% 2,5-ahydrosorbitol.

[0060] Example 1

[0061] Separation of levulinic acid: 30 g of isosorbide distillate was dissolved in 100 mL of a methanol / ethyl acetate mixed solvent (volume ratio 10:90). The solution was allowed to stand at 4°C for 6 hours to crystallize, and the initial crystals were filtered off. 30 g of isosorbide distillate was added again to the mother liquor, and the crystallization process was repeated once more. The first crystallization yielded isosorbide with a content greater than 99.0 wt%, and the mother liquor contained 92 wt% isosorbide, 3 wt% levulinic acid, and 5 wt% other impurities. The second crystallization yielded isosorbide with a content greater than 98.7 wt%, and the mother liquor contained 89 wt% isosorbide, 5 wt% levulinic acid, and 6 wt% other impurities. Take 100 mL of the final filtrate, add 150-250 μm neutral silica gel powder, stir well, evaporate the solvent, and pack it into a chromatographic column containing 75-150 μm neutral silica gel. The eluent is a mixed solvent of methanol / ethyl acetate / dichloromethane in a volume ratio of 15:15:70. Collect the eluent, evaporate the solvent, and chromatographically separate isosorbide, levulinic acid, and other mixed impurities. After chromatographic separation, solvent evaporation, and secondary crystallization, the recovery rate of isosorbide in the mother liquor is approximately 85 wt%, with a chromatographic purity greater than 99.7 wt%. The recovery rate of levulinic acid is 77 wt%, and it is identified as levulinic acid by chromatographic analysis and NMR. Other impurities cannot be separated under these conditions.

[0062] Example 2

[0063] Separation of levulinic acid: 30 g of isosorbide distillate was dissolved in 100 mL of a mixed solvent of ethanol and ethyl acetate (volume ratio 25:75). The solution was allowed to stand at 4°C for 6 hours to crystallize, and the initial crystals were filtered off. Another 30 g of isosorbide distillate was added to the mother liquor, and the crystallization process was repeated once more. The first crystallization yielded an isosorbide content greater than 99.3 wt%, with the mother liquor containing 94 wt% isosorbide, 3 wt% levulinic acid, and 3 wt% other impurities. The second crystallization yielded an isosorbide content greater than 98.7 wt%, with the mother liquor containing 91 wt% isosorbide, 4 wt% levulinic acid, and 5 wt% other impurities. Take 100 mL of the final filtrate, add 150-250 μm neutral silica gel powder, stir well, evaporate the solvent, and pack it into a chromatographic column containing 75-150 μm neutral silica gel. The eluent is a mixed solvent of methanol / ethyl acetate / dichloromethane in a volume ratio of 10:15:75. Collect the eluent, evaporate the solvent, and chromatographically separate isosorbide, levulinic acid, and other mixed impurities. After chromatographic separation, solvent evaporation, and secondary crystallization, the recovery rate of isosorbide in the mother liquor is approximately 87 wt%, with a chromatographic purity greater than 99.6 wt%. The recovery rate of levulinic acid is 80 wt%, and it is identified as levulinic acid by chromatographic analysis and NMR. Other impurities cannot be separated under these conditions.

[0064] Example 3

[0065] Isomannitol separation: 30g of isosorbide distillate was dissolved in 100mL of acetone / ethanol mixed solvent (volume ratio 50:50). The solution was allowed to stand at 4℃ for 6 hours to crystallize, and the initial crystals were filtered off. 30g of isosorbide distillate was added again to the mother liquor, and the above crystallization steps were repeated once more. The isosorbide content obtained from the first crystallization was greater than 99.3wt%, the isosorbide content in the mother liquor was 93wt%, the isomannitol content was 2wt%, and the content of other impurities was 5wt%. The isosorbide content obtained from the second crystallization was greater than 98.1wt%, the isosorbide content in the mother liquor was 91wt%, the isomannitol content was 3wt%, and the content of other impurities was 6wt%. Take 100 mL of the final filtrate and add 150-250 μm neutral silica gel powder. After evaporating the solvent, pack the solution into a chromatographic column containing 75-150 μm neutral silica gel. The eluent is a mixture of ethyl acetate and dichloromethane at a volume ratio of 17:83. Collect the eluent and evaporate the solvent. Chromatographic separation yields isosorbide, isomannitol, and other mixed impurities. After chromatographic separation, solvent evaporation, and secondary crystallization, the isosorbide recovery rate in the mother liquor is approximately 88 wt%, with a chromatographic purity greater than 99.8 wt%. The isomannitol recovery rate is 85 wt%, and it is identified as isomannitol by chromatographic analysis and NMR. Other impurities cannot be separated under these conditions.

[0066] Example 4

[0067] Isomannitol separation: 30g of isosorbide distillate was dissolved in 100mL of acetone / acetonitrile mixed solvent (volume ratio 50:50). The solution was allowed to stand at 4℃ for 6 hours to crystallize, and the initial crystals were filtered off. 30g of isosorbide distillate was added again to the mother liquor, and the above crystallization steps were repeated once more. The isosorbide content obtained from the first crystallization was greater than 99.3wt%, the isosorbide content in the mother liquor was 93wt%, the isomannitol content was 2wt%, and the content of other impurities was 5wt%. The isosorbide content obtained from the second crystallization was greater than 98.1wt%, the isosorbide content in the mother liquor was 91wt%, the isomannitol content was 3wt%, and the content of other impurities was 6wt%. Take 100 mL of the final filtrate, add 150-250 μm neutral silica gel powder, stir well, evaporate the solvent, and pack it into a chromatographic column containing 48-75 μm neutral silica gel. The eluent is a methanol / chloroform mixture with a volume ratio of 20:80. Collect the eluent, evaporate the solvent, and chromatographically separate isosorbide, isomannitol, and other mixed impurities. After chromatographic separation, solvent evaporation, and secondary crystallization, the isosorbide recovery rate in the mother liquor is approximately 87 wt%, with a chromatographic purity greater than 99.7 wt%. The isomannitol recovery rate is 89 wt%, and it is identified as isomannitol by chromatographic analysis and NMR. Other impurities cannot be separated under these conditions.

[0068] Example 5

[0069] Separation of 1,5-Dehydrated sorbitol: 30 g of isosorbide distillate was dissolved in 100 mL of a 50:50 ethanol / acetonitrile mixed solvent. The solution was allowed to stand at 4°C for 6 hours to crystallize, and the initial crystals were filtered off. 30 g of isosorbide distillate was added again to the mother liquor, and the crystallization process was repeated twice. The first crystallization yielded isosorbide content greater than 99.3 wt%, the mother liquor contained 93 wt% isosorbide, 2 wt% 1,5-dehydrated sorbitol, and 3 wt% other impurities. The second crystallization yielded isosorbide content greater than 98.1 wt%, the mother liquor contained 91.0 wt% isosorbide, 3 wt% 1,5-dehydrated sorbitol, and 6 wt% other impurities. 30 g of isosorbide distillate was added again to the mother liquor from the crystallization process. The third crystallization yielded an isosorbide content greater than 97.8 wt%, an isosorbide content of 88 wt% in the mother liquor, a 1,5-anhydrosorbitol content of 5 wt%, and other impurities of 7 wt%. 100 mL of the final filtration mother liquor was taken, and 150-250 μm neutral silica gel powder was added. The mixture was stirred thoroughly, and after solvent evaporation, it was packed into a chromatographic column containing 75-150 μm neutral silica gel. The eluent was a mixed solvent of methanol / ethyl acetate / methyl tert-butyl ether in a volume ratio of 17:10:73. After collecting the eluent, the solvent was evaporated, and isosorbide, 1,5-anhydrosorbitol, and other mixed impurities were separated chromatographically. After chromatographic separation and solvent evaporation, the isosorbide recovery rate in the mother liquor after three crystallizations was approximately 90 wt%, and the chromatographic purity was greater than 98.1 wt%. The recovery rate of 1,5-sorbitol was 81 wt%, and it was identified as 1,5-sorbitol by chromatographic analysis and NMR. Other impurities could not be separated under these conditions.

[0070] Example 6

[0071] Separation of 1,5-Dehydrated sorbitol: 30 g of isosorbide distillate was dissolved in 100 mL of acetone / ethyl acetate mixed solvent (50:50 volume ratio). The solution was allowed to stand at 4°C for 6 hours to crystallize, and the initial crystals were filtered off. 30 g of isosorbide distillate was added again to the mother liquor, and the crystallization process was repeated twice. The first crystallization yielded isosorbide content greater than 99.3 wt%, the mother liquor contained 93 wt% isosorbide, 2 wt% 1,5-dehydrated sorbitol, and 5 wt% other impurities. The second crystallization yielded isosorbide content greater than 98.1 wt%, the mother liquor contained 91.0 wt% isosorbide, 3 wt% 1,5-dehydrated sorbitol, and 6 wt% other impurities. 30 g of isosorbide distillate was added again to the mother liquor from the crystallization process. The third crystallization yielded isosorbide with a content greater than 97.8 wt%, isosorbide content in the mother liquor was 88 wt%, 1,5-adenosorbitol content was 5 wt%, and other impurities content was 8 wt%. 100 mL of the final filtration mother liquor was taken, and 150-250 μm neutral silica gel powder was added. After evaporating the solvent, the solution was packed into a chromatographic column containing 38-48 μm neutral silica gel. The eluent was a mixed solvent of acetone / ethyl acetate / dichloromethane in a volume ratio of 10:10:80. After collecting the eluent and evaporating the solvent, isosorbide, 1,5-adenosorbitol, and other mixed impurities were separated chromatographically. After chromatographic separation and solvent evaporation, the recovery rate of isosorbide in the mother liquor after three crystallizations was approximately 90 wt%, and the chromatographic purity was greater than 98.5 wt%. The recovery rate of 1,5-sorbitol was 93 wt%, and it was identified as 1,5-sorbitol by chromatographic analysis and NMR. Other impurities could not be separated under these conditions.

[0072] Example 7

[0073] Separation of 2,6-Dehydrated sorbitol: 30 g of isosorbide distillate was dissolved in 100 mL of a methanol / tetrahydrofuran mixed solvent (80:20 volume ratio). The solution was placed in a crystallization vessel at 5 °C and allowed to stand for 12 hours to crystallize. The initial crystals were filtered off. 30 g of isosorbide distillate was added again to the mother liquor, and the crystallization process was repeated twice. The first crystallization yielded isosorbide content greater than 99.0 wt%, with the mother liquor containing 92 wt% isosorbide, 2 wt% ... 30 g of isosorbide distillate was added again to the mother liquor from the crystallization process. The third crystallization yielded isosorbide content greater than 97.8 wt%, the mother liquor contained 82 wt% isosorbide, 7 wt% 2,6-ahydrosorbitol, and 11 wt% other impurities. 100 mL of the final filtration mother liquor was taken, and 150-250 μm neutral silica gel powder was added. After solvent evaporation, the solution was packed into a 38-150 μm neutral alumina column. The eluent was a methanol / dichloromethane mixture at a volume ratio of 17:83. After collecting the eluent and evaporating the solvent, isosorbide, 2,6-ahydrosorbitol, and other mixed impurities were separated chromatographically. After chromatographic separation and solvent evaporation, the isosorbide recovery rate in the mother liquor after three crystallizations was approximately 92 wt%, with a chromatographic purity greater than 99.3 wt%. The 2,6-ahydrosorbitol recovery rate was 90 wt%, and it was identified as 2,6-ahydrosorbitol by chromatographic analysis and NMR. Other impurities cannot be separated under these conditions.

[0074] Example 8

[0075] Separation of 2,6-Dehydrated sorbitol: 30 g of isosorbide distillate was dissolved in 100 mL of a methanol / ethyl acetate mixed solvent (80:20 volume ratio). The solution was placed in a crystallization vessel at 5 °C and allowed to stand for 12 hours to crystallize. The initial crystals were filtered off. 30 g of isosorbide distillate was added again to the mother liquor, and the above crystallization steps were repeated twice. The first crystallization yielded isosorbide with a content greater than 99.0 wt%, and the mother liquor contained 92 wt% isosorbide, 3 wt% 2,6-dehydrated sorbitol, and 4 wt% other impurities. The second crystallization yielded isosorbide with a content greater than 98.5 wt%, and the mother liquor contained 89.0 wt% isosorbide, 7 wt% 2,6-dehydrated sorbitol, and 4 wt% other impurities. 30 g of isosorbide distillate was added again to the mother liquor from the crystallization process. The third crystallization yielded isosorbide content greater than 97.8 wt%, the mother liquor contained 82 wt% isosorbide, 11 wt% 2,6-ahydrosorbitol, and 87 wt% other impurities. 100 mL of the final filtration mother liquor was taken, and 150-250 μm neutral silica gel powder was added. After evaporating the solvent, the solution was packed into a chromatographic column containing 38-150 μm basic alumina. The eluent was a methanol / acetonitrile / ethanol mixture with a volume ratio of 15:20:65. After collecting the eluent and evaporating the solvent, isosorbide, 2,6-ahydrosorbitol, and other mixed impurities were separated chromatographically. After chromatographic separation and solvent evaporation, the isosorbide recovery rate in the mother liquor after three crystallizations was approximately 90 wt%, and the chromatographic purity was greater than 99.7 wt%. The recovery rate of 2,6-sorbitol was 84 wt%, and it was identified as 2,6-sorbitol by chromatographic analysis and NMR. Other impurities could not be separated under these conditions.

[0076] Example 9

[0077] Separation of 2,5-Dehydrated sorbitol: 30 g of isosorbide distillate was dissolved in 100 mL of a mixed solvent of isopropanol and ethyl acetate (90:10 volume ratio). The solution was placed in a crystallization vessel at 0°C and allowed to stand for 12 hours to crystallize. The initial crystals were filtered off. 30 g of isosorbide distillate was added again to the mother liquor, and the crystallization process was repeated twice. The first crystallization yielded isosorbide with a content greater than 99.5 wt%, and the mother liquor contained 94 wt% isosorbide, 3 wt% 2,5-dehydrated sorbitol, and 3 wt% other impurities. The second crystallization yielded isosorbide with a content greater than 98.9 wt%, and the mother liquor contained 89.0 wt% isosorbide, 7 wt% 2,5-dehydrated sorbitol, and 4 wt% other impurities. 30 g of isosorbide distillate was added again to the mother liquor from crystallization. The third filtration yielded isosorbide with a content greater than 98.8 wt%, isosorbide content in the mother liquor was 83 wt%, 2,5-ahydrosorbitol content was 10 wt%, and other impurities were 7 wt%. 100 mL of the final filtration mother liquor was taken, and 75-150 μm neutral silica gel powder was added. The mixture was stirred until homogeneous, and after evaporating the solvent, it was packed into a chromatographic column containing 75-150 μm neutral silica gel. The eluent was a methanol / dichloromethane mixture at a volume ratio of 10:90 to remove the product. The eluent was collected and then added to a chromatographic column packed with 48-75 μm neutral silica gel. After collecting the second eluent, the solvent was evaporated, and isosorbide, 2,5-ahydrosorbitol, and other mixed impurities were separated by chromatography. After chromatographic separation, solvent evaporation, and three crystallizations, the isosorbide recovery rate in the mother liquor was approximately 88 wt%, with a chromatographic purity greater than 99.5 wt%. The 2,5-anhydrosorbitol recovery rate was 77 wt%, and it was identified as 2,5-anhydrosorbitol by chromatographic analysis and NMR. Other impurities could not be separated under these conditions.

[0078] Example 10

[0079] Separation of 2,5-Dehydrated sorbitol: 30 g of isosorbide distillate was dissolved in 100 mL of a 90:10 ethanol / ethyl acetate mixed solvent. The solution was placed in a crystallization vessel at 0°C and allowed to stand for 24 hours to crystallize. The initial crystals were filtered off. 30 g of isosorbide distillate was added again to the mother liquor, and the crystallization process was repeated twice. The first crystallization yielded isosorbide with a content greater than 99.7 wt%, and the mother liquor contained 89 wt% isosorbide, 6 wt% 2,5-dehydrated sorbitol, and 5 wt% other impurities. The second crystallization yielded isosorbide with a content greater than 99.0 wt%, and the mother liquor contained 84.0 wt% isosorbide, 8 wt% 2,5-dehydrated sorbitol, and 8 wt% other impurities. 30 g of isosorbide distillate was added again to the mother liquor from crystallization. The third elution yielded isosorbide content greater than 98.7 wt%, isosorbide content in the mother liquor was 80 wt%, 2,5-ahydrosorbitol content was 9 wt%, and other impurities content was 11 wt%. 100 mL of the final filtration mother liquor was taken, and 75-150 μm neutral silica gel powder was added. The mixture was stirred thoroughly, and after evaporating the solvent, it was packed into a chromatographic column containing 75-150 μm neutral silica gel. The eluent was a methanol / dichloromethane mixture at a volume ratio of 15:85 to remove the product. The eluent was collected and then added to a chromatographic column packed with 38-48 μm neutral silica gel for a second elution. After collecting the second eluent, the solvent was evaporated, and isosorbide, 2,5-ahydrosorbitol, and other mixed impurities were separated by chromatography. After chromatographic separation, solvent evaporation, and three crystallizations, the recovery rate of isosorbide in the mother liquor was approximately 88 wt%, with a chromatographic purity greater than 99.5 wt%. The recovery rate of 2,5-ahydrosorbitol was 86 wt%, and it was identified as 2,5-ahydrosorbitol by chromatographic analysis and NMR. Other impurities could not be separated under these conditions.

[0080] Comparative Example 1

[0081] Take 30g of isosorbide distillate, dissolve it in 90mL of ethanol, place the solution at 4℃ for 6 hours to crystallize, filter to obtain white isosorbide crystals with a purity of 98.5wt%, of which there are 5 kinds of impurities with a content greater than 0.1wt%, which cannot be separated under these conditions.

[0082] Comparative Example 2

[0083] Take 30g of isosorbide distillate, dissolve it in 90mL of acetone, let the solution stand at 4℃ for 6 hours to crystallize, filter to obtain white isosorbide crystals with a purity of 98.0wt%, of which there are 4 kinds of impurities with a content greater than 0.1wt%, which cannot be separated under these conditions.

[0084] Comparative Example 3

[0085] Dissolve 30 g of isosorbide distillate in 30 mL of hot methanol. Add the methanol mixture to 75-150 μm neutral silica gel powder, stir well, evaporate the solvent, and pack the solution into a chromatographic column containing 75-150 μm neutral silica gel. The eluent is a methanol / dichloromethane mixture with a volume ratio of 15:85. Column chromatography yields a fraction containing isosorbide. After evaporating the solvent, an oily isosorbide solution with a purity of 97 wt% is obtained. Three impurities with a content greater than 0.1 wt% were present, and these impurities could not be separated under these conditions.

[0086] Application examples

[0087] Modification experiments were conducted on ethylene glycol terephthalate using purified isosorbide from the examples and comparative examples, as well as commercially available isosorbide samples from brands A and B. The specific conditions were as follows: the molar ratio of isosorbide (the above products) to ethylene glycol was 1:4, the molar ratio of alcohol to acid was (isosorbide + ethylene glycol) / terephthalic acid = 1.5, the catalyst was germanium dioxide, the catalyst dosage was 500 μg / g, the esterification temperature was 240℃, the esterification time was 80 min, the polycondensation temperature was 275℃, and the polycondensation time was 100 min.

[0088] The polyester prepared above was tested, and the results are shown in Table 1. The weight-average molecular weight of the polyester was determined using the GPC method; the polyester Tg temperature was determined using the DSC method. Colorimetry results are from colorimeter measurements.

[0089] Table 1

[0090]

[0091]

[0092] As can be seen from the data of the above embodiments and the results in Table 1, Examples 1-10 of the method for reducing the impurity content in dehydrated sugar alcohols using the present invention have higher isosorbide purity, fewer types of impurities, and can also recover single impurities accordingly. The modified polyester has significantly better physical parameters and other effects.

[0093] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for reducing the impurity content in dehydrated sugar alcohols, characterized in that, The method includes: (1) The crude dehydrated sugar alcohol is dissolved in an organic solvent and then crystallized. (2) After solid-liquid separation of the mixture obtained in step (1), the resulting mother liquor is separated by chromatography.

2. The method according to claim 1, wherein, The crude dehydrated sugar alcohol product includes dehydrated sugar alcohol and impurities; Preferably, the crude dehydrated sugar alcohol contains 90-99 wt% dehydrated sugar alcohol and 1-10 wt% impurities. Preferably, the dehydrated sugar alcohol is selected from at least one of isosorbide, isomannitol, isoadulol, dehydrated glucose, defructose, and dehydrated mannitol; Preferably, the impurities include at least one of levulinic acid, isomannitol, 1,5-sorbitol, 2,6-sorbitol, and 2,5-sorbitol and furanoic acid.

3. The method according to claim 1 or 2, wherein, The organic solvent is selected from at least one of methanol, ethanol, isopropanol, dichloromethane, chloroform, acetone, acetonitrile, methyl acetate, ethyl acetate, methyl tert-butyl ether, tetrahydrofuran, and xylene, preferably at least two; Preferably, when there are two organic solvents, the volume contents of the two solvents are 10-90 vol% and 10-90 vol%, respectively.

4. The method according to claim 1, wherein, The crystallization method is as follows: S1. The first part of the crude dehydrated sugar alcohol is dissolved in an organic solvent and then subjected to the first crystallization. S2. Take out the crystals from the first crystallization and mix the remaining mother liquor from the first crystallization with the second part of the dehydrated sugar alcohol crude product for a second crystallization; Preferably, step S2 is performed at least once.

5. The method according to claim 4, wherein, The amount of the first portion of crude dehydrated sugar alcohol relative to 100 mL of organic solvent is 10-50 g; And / or, in the process of the previous crystallization and the subsequent crystallization, the weight ratio of the crude dehydrated sugar alcohol is 1:1-5; And / or, step S2 is performed 1-3 times.

6. The method according to claim 1 or 4, wherein, The crystallization conditions include: a crystallization temperature of 0-15℃, preferably 4-10℃; and a crystallization time of 2-30h, preferably 6-24h.

7. The method according to claim 1, wherein, The packing material used for chromatographic separation is selected from at least one of neutral silica gel, neutral activated carbon, basic activated carbon, neutral alumina, basic alumina, ion exchange resin and polystyrene microspheres; Preferably, the average particle size of the filler is 25-250 μm; And / or, the chromatographic separation is performed at least once.

8. The method according to claim 1, wherein, The eluent used in the chromatographic separation is selected from at least two of methanol, ethanol, dichloromethane, chloroform, acetone, acetonitrile, methyl acetate, ethyl acetate, methyl tert-butyl ether, and tetrahydrofuran, preferably two or three. Preferably, when there are two or three eluents, the volume content of each eluent is 0-20 vol%, 10-20 vol%, and 60-90 vol%, respectively; And / or, the chromatographic separation is performed 1-3 times.

9. The method according to claim 4, wherein, The impurity is levulinic acid, and the crystallization conditions include: organic solvents of 10-25 vol% organic solvent A and 75-90 vol% organic solvent B; organic solvent A is selected from organic solvents with a polarity not lower than acetone, and organic solvent B is selected from organic solvents with a polarity lower than acetone; the chromatographic separation conditions include: the eluent used in chromatographic separation is 10-15 vol% eluent a, 10-15 vol% eluent b, and 70-75 vol% eluent c; eluent a is selected from organic solvents with a polarity higher than acetone, eluent b is selected from organic solvents with a polarity not higher than acetone and not lower than methyl acetate, and eluent c is selected from organic solvents with a polarity lower than methyl acetate. Alternatively, the impurity is isomannitol, and the crystallization conditions include: organic solvent C of 40-60 vol% and organic solvent D of 40-60 vol%; organic solvent C is selected from organic solvents with a polarity not higher than acetone, and organic solvent D is selected from organic solvents with a polarity higher than acetone; the chromatographic separation conditions include: eluent d of 15-20 vol% and eluent e of 80-85 vol%; eluent d is selected from organic solvents with a polarity not lower than methyl acetate, and eluent e is selected from organic solvents with a polarity lower than methyl acetate; Alternatively, the impurity is 1,5-sorbitol, and the crystallization conditions include: organic solvents of 40-60 vol% organic solvent E and 40-60 vol% organic solvent F; organic solvent E is selected from organic solvents with a polarity not less than acetone, and organic solvent F is selected from organic solvents with a polarity not less than methyl acetate; the chromatographic separation conditions include: the eluent used in the chromatographic separation is 10-20 vol% eluent f, 10-15 vol% eluent g, and 70-80 vol% eluent h; eluent f is selected from organic solvents with a polarity not less than acetone, eluent g is selected from organic solvents with a polarity less than acetone but not less than methyl acetate, and eluent h is selected from organic solvents with a polarity less than methyl acetate. Alternatively, the impurity is 2,6-sorbitol, and the crystallization conditions include: 75-85 vol% organic solvent G and 15-25 vol% organic solvent H; organic solvent G is selected from organic solvents with a polarity not less than acetone, and organic solvent H is selected from organic solvents with a polarity less than acetone; the chromatographic separation conditions include: the eluent used in chromatographic separation is 10-20 vol% organic solvent with a polarity not less than acetone and 80-90 vol% organic solvent with a polarity less than acetone, or 10-20 vol% organic solvent with a polarity not less than methanol and a polarity less than acetonitrile, 10-30 vol% organic solvent with a polarity not less than acetonitrile and 60-70 vol% organic solvent with a polarity less than methanol and a polarity not less than acetone; Alternatively, the impurity is 2,5-sorbitol, and the crystallization conditions include: 85-90 vol% organic solvent I and 10-15 vol% organic solvent J; organic solvent I is selected from non-polar... I97307BHY Organic solvents with a polarity lower than acetone, wherein organic solvent J is selected from organic solvents with a polarity lower than acetone and a polarity not lower than methyl acetate; the chromatographic separation conditions include: the eluent used in chromatographic separation is 10-15 vol% eluent i and 85-90 vol% eluent j; eluent i is selected from organic solvents with a polarity not lower than acetone, and eluent j is selected from organic solvents with a polarity lower than methyl acetate.

10. The use of the method according to any one of claims 1-9 in the synthesis of polyol esters.

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