A method for removing trace amounts of colored substances from 2,5-furandicarboxylic acid

Abstract

The application provides a method for removing trace colored substances in 2,5-furan dicarboxylic acid. The application first uses dialdehyde and amine to synthesize high-temperature-resistant porous material containing polyamino, and then removes trace colored substances by chemical adsorption under high-temperature conditions. Under the condition of more than 100 DEG C, the trace colored substances with content below 1000 ppm in 2,5-furan dicarboxylic acid are adsorbed, and the decolorization rate reaches more than 95%. The application utilizes the high-temperature stability of porous material formed by aldehyde and amine, the thermal stability of amide bond formed by amino and colored substances, and the difference in reactivity of carboxyl in 2,5-furan dicarboxylic acid and carboxyl in colored substances with amino, and specifically removes trace colored substances in 2,5-furan dicarboxylic acid. The application provides a new scheme for the decolorization process of refined 2,5-furan dicarboxylic acid.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of organic matter decolorization, and particularly relates to a method for removing trace colored substances in 2,5-furan dicarboxylic acid. BACKGROUND

[0002] 2,5-furan dicarboxylic acid (FDCA) is an important bio-based platform compound. Because it is a binary acid with a rigid aromatic ring structure, it can be used for the synthesis of polyesters such as polyethylene glycol 2,5-furan dicarboxylate (PEF), and its thermodynamic performance is better than that of traditional petroleum-based polyester polyethylene terephthalate (PET). The water and CO2 barrier properties are also superior to PET. PET is also known as "polyester fiber" or "polyester". Plastic bottles, toothbrush cups, and mobile phone tempered films used daily are all derived from PET. In April 2023, the domestic polyester production capacity was adjusted to 74.42 million tons, of which the production capacity of bottle-grade PET and film-grade PET accounted for 15.495 million tons, showing a growing trend. Therefore, as a material that can replace PET, PEF has a very huge market application prospect and estimated demand. As a raw material for the synthesis of PEF, the quality of FDCA is important. Its main synthesis route is to dehydrate monosaccharides such as fructose to generate 5-hydroxymethylfurfural, and then further oxidize it to generate FDCA. At the same time, caramel-like colored substances contained in 5-hydroxymethylfurfural are also oxidized into colored substances containing carboxylic acid. Through conventional recrystallization and physical adsorption with activated carbon, trace colored substances below 1000 ppm are difficult to remove, and cannot meet the color requirements of polymerization grade. Therefore, exploring new decolorization methods and effectively adsorbing and removing trace substances contained in FDCA are of great significance to improve the color quality of FDCA and meet the requirements of polymerization grade. SUMMARY

[0003] To solve all or part of the above technical problems, the present application provides the following technical solutions:

[0004] The main purpose of the present application is to provide a method for removing trace colored substances in 2,5-furan dicarboxylic acid, comprising: mixing and reacting an amine compound and an organic compound containing a dialdehyde group in a first solvent to obtain a porous adsorbent;

[0005] Dissolving 2,5-furan dicarboxylic acid to be decolored in a second solvent to form a 2,5-furan dicarboxylic acid solution, mixing and contacting the porous adsorbent with the 2,5-furan dicarboxylic acid solution, so that the trace colored substances in the 2,5-furan dicarboxylic acid are adsorbed by the porous adsorbent and removed from the 2,5-furan dicarboxylic acid.

[0006] The basic principle of the present application is that the reaction of an amine compound and an organic compound containing a dialdehyde group can generate a porous adsorbent rich in amino groups (-NH2) and high-temperature-resistant chemical bonds (-RC=N-). The amino groups on the porous adsorbent can form relatively stable amide bonds with the carboxyl groups on the colored substances in FDCA (containing a large number of carboxyl groups after oxidation) below 200℃, so that the colored substances are adsorbed by the porous adsorbent, and the amide bonds formed by the carboxyl groups in FDCA and the amino groups on the porous adsorbent under the influence of the lone pair of electrons on the furan ring need to be above 230℃, based on the difference in reactivity between the two, the porous material can achieve the specific adsorption of colored substances in FDCA, especially the specific adsorption of trace colored substances, and the loss of FDCA is not easy during the adsorption process; and the porous adsorbent is a porous material, which has high-efficiency adsorption performance mainly by chemical adsorption and supplemented by pore physical adsorption; based on the fact that amino groups can react with carboxyl groups on colored substances to form amide bonds, and amide bonds have good thermal stability and are not easy to desorb in a high-temperature environment, thereby realizing efficient and stable chemical adsorption, solving the problem that the adsorbent in the prior art is easy to desorb under high-temperature conditions. The present application can efficiently remove trace colored substances which are extremely difficult to remove from bio-based platform compound FDCA, which has important practical application value for improving the color quality of FDCA and meeting the requirements of polymerization grade. And the present application provides a new method for removing trace colored substances from FDCA.

[0007] In some embodiments, the porous adsorbent further contains carbon-nitrogen double bonds. That is, the porous adsorbent itself has high-temperature-resistant chemical bonds (-RC=N-), which is suitable for use in a high-temperature environment. For example, an amine compound containing two or more amino groups can be reacted with an organic compound containing a dialdehyde group to obtain a porous adsorbent containing carbon-nitrogen double bonds.

[0008] In some embodiments, the temperature at which the mass loss of the porous adsorbent in a nitrogen environment reaches 5% is above 300℃, that is, the porous adsorbent has good high-temperature stability.

[0009] In some embodiments, the morphology of the porous adsorbent is spherical or irregular spherical, and the size is 10-500μm.

[0010] In some embodiments, the specific surface area of the porous adsorbent is above 540m 2 / g, and has a rich porous structure.

[0011] In some embodiments, the colored substance includes a colored substance containing carboxyl groups formed in the oxidation process of a saccharide organic material in the process of preparing FDCA from the saccharide organic material as a raw material; for example, caramel-like substances contained in 5-hydroxymethylfurfural are oxidized to form colored substances containing carboxyl groups. That is, in the process of preparing furan-based carboxylic acids from biomass-derived organic materials (such as saccharide organic materials) as raw materials, these biomass-based organic materials can form colored substances containing carboxyl groups in the oxidation process, which are difficult to remove from furan-based carboxylic acid samples, especially when the content of colored substances is trace, the effect of traditional decolorization methods is not significant, and even the furan-based carboxylic acid sample can be lost. The decolorization method provided by the present application can remove these colored substances.

[0012] Of course, it should be understood that the removal method can also remove other types of colored substances that can exist in FDCA. For colored substances that have active groups on the surface and can chemically react with the porous adsorbent, the porous adsorbent can effectively adsorb them based on the combined action of chemical adsorption and physical adsorption; for colored substances that do not contain reactive groups, the porous adsorbent provided by the present application can effectively adsorb them based on physical adsorption.

[0013] In some embodiments, the amine compound includes one or a combination of ammonia, aqueous ammonia, aromatic diamine, C2-C 12 alkyl diamine, polyamine, but is not limited to this.

[0014] In some embodiments, the aromatic diamine includes one or a combination of p-xylylenediamine, p-phenylenediamine, m-xylylenediamine, m-phenylenediamine, o-xylylenediamine, o-phenylenediamine, but is not limited to this.

[0015] In some embodiments, the C2-C 12 alkyl diamine includes one or a combination of ethylenediamine, propylenediamine, oxalyl diamine, octylenediamine, adipoyl diamine, pyridine-3,5-diamine, maleic acid diamine, 2,2-dimethyl-1,3-propanediamine, but is not limited to this.

[0016] In some embodiments, the polyamine includes one or a combination of diethylenetriamine, N-butylthiophosphoric acid triamine, bis(hexamethylene)triamine, pyrimidine-4,5,6-triamine, 4H-1,2,4-triazole-3,4,5-triamine, tris(2-aminoethyl)amine, tris(4-aminophenyl)amine, but is not limited to this.

[0017] In some embodiments, the organic material containing a dialdehyde group includes C2-C 10one or more of a combination of alkanedial, aromatic ring dialdehyde, but not limited to this.

[0018] In some embodiments, the C2~C 10 The alkanedial includes pentanedial and / or octanedial, but not limited to this.

[0019] In some embodiments, the aromatic ring dialdehyde includes one or more of a combination of o-phthaldehyde, m-phthaldehyde, p-phthaldehyde, furan dialdehyde, but not limited to this.

[0020] In some embodiments, the first solvent includes one or more of a combination of C1~C 10 The alkyl alcohol solvent, the alkanes solvent, the amide solvent or water includes one or more of a combination of methanol, ethanol, cyclohexanol, isopropyl alcohol, n-octanol, decanol or ethylene glycol, but not limited to this.

[0021] In some embodiments, the C1~C 10 The alkyl alcohol solvent includes one or more of a combination of methanol, ethanol, cyclohexanol, isopropyl alcohol, n-octanol, decanol or ethylene glycol, but not limited to this.

[0022] The alkanes solvent includes one or more of a combination of dichloromethane, trichloromethane, n-hexane, cyclohexane, n-octane, benzene or toluene, but not limited to this.

[0023] The amide solvent includes N,N-dimethylformamide and / or N,N-dimethylacetamide, but not limited to this.

[0024] In some embodiments, the method for preparing the porous adsorbent specifically includes: using the first solvent to prepare the amine compound and the organic compound containing dialdehyde group into amine compound solution and dialdehyde organic compound solution respectively; mixing the two solutions by at least dropwise to form the mixed reaction system.

[0025] In some embodiments, the dropwise speed is 1~600mL / min. For example, the upper limit of the dropwise speed is 30mL / min, 35mL / min, 40mL / min, 45mL / min, 50mL / min, 55mL / min or 60mL / min, and the lower limit of the dropwise speed is 1mL / min, 5mL / min, 10mL / min, 15mL / min, 20mL / min or 25mL / min.

[0026] In some embodiments, the reaction temperature for preparing the porous adsorbent is 20-100°C. For example, the upper limit of the reaction temperature can be 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, or 100°C, and the lower limit of the reaction temperature can be 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, or 65°C.

[0027] In some embodiments, the molar ratio of the amine compound to the organic compound containing a dialdehyde group is 2:3-3:1. For example, the molar ratio of the amine compound to the organic compound containing a dialdehyde group can be 1:1-1.5:1, 1.5:1-2:1, 2:1-2.5:1, or 2.5:1-3:1.

[0028] In some embodiments, the mass percentage concentration of the amine compound and the organic compound containing a dialdehyde group is 10-60% respectively. Within this concentration range, the uniform dispersion of the reactants is facilitated, the reaction is orderly, the reaction rate is appropriate, and the solvent is saved. If the concentration is too high, the reaction product may agglomerate, and thus the concentration needs to be kept appropriate.

[0029] In some embodiments, the reaction time for preparing the porous adsorbent is 0.5-24 hours.

[0030] In some typical embodiments, the method for preparing the porous adsorbent comprises the following steps:

[0031] The amine compound and the organic compound containing a dialdehyde group are respectively prepared into an amine compound solution and a dialdehyde organic compound solution using a first solvent;

[0032] The temperature of the amine compound solution and the dialdehyde organic compound solution is kept at 20-100°C, and the two solutions are mixed by dropwise addition, so that the molar ratio of the amine compound to the organic compound containing a dialdehyde group in the mixed reaction system is 2:3-3:1. After the dropwise addition is completed, the reaction is continued by stirring for 0.5-24 hours to obtain the porous adsorbent.

[0033] The solid precipitate is collected by filtration, washed until the pH of the washing liquid is 6-8, and then dried.

[0034] In some embodiments, the second solvent comprises one or a combination of water, an alcohol solvent, an alkane solvent, a sulfoxide solvent, an amide solvent, a pyrrolidone solvent, an organic acid solvent, or an ionic liquid, but is not limited thereto.

[0035] In some embodiments, the alcohol solvent comprises one or a combination of methanol, ethanol, butanol, isopropanol, octanol, decanol, or ethylene glycol, but is not limited thereto.

[0036] In some embodiments, the alkane solvent includes dichloromethane, trichloromethane, n-hexane, cyclohexane, n-octane, benzene, or toluene, or a combination of one or more thereof, but is not limited thereto.

[0037] The sulfoxide solvent includes thionyl chloride and / or dimethyl sulfoxide, but is not limited thereto.

[0038] In some embodiments, the amide solvent includes N,N-dimethylformamide and / or N,N-dimethylacetamide, but is not limited thereto.

[0039] In some embodiments, the pyrrolidone solvent includes N-methyl pyrrolidone, but is not limited thereto.

[0040] In some embodiments, the organic acid solvent includes a combination of one or more of acetic acid, propionic acid, and trifluoroacetic acid, but is not limited thereto.

[0041] In some embodiments, the ionic liquid includes a combination of one or more of quaternary ammonium ionic liquid, imidazole ionic liquid, and pyridine ionic liquid, but is not limited thereto.

[0042] In some embodiments, the colored substance includes a colored substance containing a carboxyl group formed in an oxidation process of a saccharide organic material in a process of preparing 2,5-furandicarboxylic acid using the saccharide organic material as a raw material.

[0043] In some embodiments, the removal method can remove the colored substance in the 2,5-furandicarboxylic acid sample in an amount of 1000 ppm or less, and preferably, the removal method can remove the colored substance in the 2,5-furandicarboxylic acid sample in an amount of 200 ppm or less. For example, the method provided by the present application can achieve good decolorization for a sample in which the upper limit of the content of the colored substance is 1000 ppm, 900 ppm, 800 ppm, 700 ppm, 600 ppm, 500 ppm, or 200 ppm, and the lower limit is 50 ppm, 100 ppm, or 150 ppm.

[0044] In some embodiments, the temperature condition is maintained at 100-200°C during the adsorption of the colored substance by the porous adsorbent, and preferably, the temperature condition is maintained at 140-160°C. For example, the lower limit of the adsorption temperature condition can be 100°C, 110°C, 120°C, 130°C, and 140°C, and the upper limit of the adsorption temperature condition can be 150°C, 160°C, 170°C, 180°C, 190°C, and 200°C.

[0045] In some embodiments, the contact time of the porous adsorbent with the 2,5-furan dicarboxylic acid sample to be decolorized is 10 minutes to 12 hours to achieve sufficient decolorization, and the contact time can be shorter when the content of the colored substance is low or the temperature is high, and the contact time can be longer when the content of the colored substance is high or the temperature is low.

[0046] In some embodiments, a batch adsorption method and / or a fixed bed adsorption method is used to allow the porous adsorbent to adsorb the colored substance.

[0047] In some embodiments, in the batch adsorption method, the amount of the porous adsorbent is 1 to 20 wt% of the mass of the 2,5-furan dicarboxylic acid, and preferably 5 to 10 wt%.

[0048] In some embodiments, in the fixed bed adsorption method, the space velocity of the 2,5-furan dicarboxylic acid sample is 10 h -1 to 100 h -1 , and preferably 40 h -1 to 60 h -1 .

[0049] Compared with the prior art, the present application has at least the following beneficial effects:

[0050] (1) The present application uses a porous adsorbent rich in amino groups to remove trace amounts of colored substances in a 2,5-furan dicarboxylic acid sample; the porous adsorbent has excellent adsorption and decolorization effects with chemical adsorption as the main method and pore physical adsorption as the auxiliary method, and it can achieve efficient adsorption of trace amounts of colored substances with a concentration of 1000 ppm or less at a temperature higher than 100℃, and the decolorization rate is more than 95%;

[0051] (2) The amino groups on the porous adsorbent of the present application form amide bonds with the carboxyl groups contained in the colored substances to achieve chemical adsorption, and these amide bonds have high temperature stability and are not easy to desorb even at high temperatures, solving the problem of easy desorption of the colored substances in the conventional physical adsorption method of the prior art at high temperatures; further, the porous adsorbent itself can contain high-temperature resistant chemical bonds (-RC=N-), and thus the material itself has excellent high-temperature thermal stability and is suitable for use at high temperatures;

[0052] (3) The amino active groups contained on the surface of the porous adsorbent of the present application have poor reactivity with the carboxylic acids on the FDCA and the colored substances, and thus the specific removal of the colored substances in the FDCA sample can be achieved without causing loss of the FDCA sample, and the porous adsorbent is suitable for application in the removal of colored substances generated in the process of preparing FDCA from sugar organic matter;

[0053] (4) The application provides a method for efficiently removing trace colored substances in a bio-based platform compound FDCA, which has important practical application value for improving the color quality of FDCA and meeting the requirements of polymerization grade. BRIEF DESCRIPTION OF DRAWINGS

[0054] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or prior art description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments described in the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0055] Figure 1 It is a removal method schematic diagram of the porous adsorbent used in an embodiment of the present application to adsorb colored substances in 2,5-furan dicarboxylic acid;

[0056] Figure 2 It is a thermogravimetric analysis diagram of the porous adsorbent prepared in embodiment 2 of the present application;

[0057] Figure 3 It is a Fourier infrared spectrum of the porous adsorbent synthesized in embodiment 4 of the present application measured by potassium bromide tabletting method;

[0058] Figure 4 It is a standard curve of platinum-cobalt color number and ion concentration used in the embodiment of the present application to test the removal rate of colored substances. DETAILED DESCRIPTION

[0059] The technical solutions of the present application will be described in detail below in combination with specific embodiments, so that those skilled in the art can better understand and implement the technical solutions of the present application. The specific functional details disclosed herein should not be interpreted as limiting, but only as a basis for the claims and for teaching those skilled in the art to employ the representative basis of the present application in different ways in any appropriate detailed embodiment.

[0060] The present application calculates the removal rate of colored substances by the following method:

[0061] Because there are many kinds of trace colored substances in bio-based organic matter, and there is a lack of standard substances, but most of them are yellow or light yellow, therefore, the platinum-cobalt color number is used, the platinum-cobalt ion is used as a reference, the relationship curve of platinum-cobalt color number and platinum-cobalt ion concentration is established, the color depth of the sample before and after decolorization is tested by a colorimeter, the corresponding ion concentration is calculated, and the removal rate of adsorbed colored substances is calculated according to the following formula:

[0062]

[0063] In the formula, p is the removal rate of colored substances, %; Co and C e respectively are initial concentration and equilibrium concentration after adsorption by activated carbon of the colored substance, ppm (mg / L).

[0064] The relationship curve between platinum-cobalt color number and ion concentration is shown in Figure 4 When testing using the standard curve, samples with darker color can be diluted for testing, and the concentration needs to be multiplied by the dilution factor when calculating.

[0065] The reagents used in the examples of the present application are all commercially available AR grade reagents, FDCA is obtained from experimental synthesis, the method is referred to ZL201911134925.4 "Low-temperature preparation method of 2,5-furan dicarboxylic acid", and the platinum-cobalt color standard solution is a commercially available standard substance, which meets the standard of "GB / T 3143-1982 Liquid chemical product color determination method (Hazen unit-platinum-cobalt color number)".

[0066] Example 1

[0067] 200 mL of 0.25 mol / L ammonia water was diluted with water to 0.0625 mol / L, and the temperature was kept at 20℃. 0.0167 mol (2.2355 g) of isophthalaldehyde was dissolved in methanol to prepare a 30% mass concentration isophthalaldehyde-methanol solution, and the temperature was kept at 20℃. The isophthalaldehyde-methanol solution was added to the ammonia water at a speed of 60 mL / h, and stirred at 200 rpm for 24 hours. The precipitate was collected by filtration, washed with water to pH 7-7.5, and dried at 60℃ under vacuum to obtain a porous adsorbent.

[0068] The porous adsorbent described in this example was used to remove trace amounts of colored substances in 2,5-furan dicarboxylic acid, and the specific process parameters and removal effects are shown in Table 1.

[0069] Example 2

[0070] 2.5 mol of p-xylylenediamine was dissolved in methanol to prepare a 10% mass fraction solution, and the temperature was kept at 50℃. 1 mol of 2,5-furan dicarboxaldehyde was dissolved in methanol to prepare a 10% mass concentration 2,5-furan dicarboxaldehyde-methanol solution, and the temperature was kept at 50℃. The 2,5-furan dicarboxaldehyde-methanol solution was added to the p-xylylenediamine-methanol solution at a speed of 10 mL / h, and stirred at 300 rpm. After the addition was completed, the stirring was continued for 2 hours. The precipitate was collected by filtration, washed with methanol and water to pH 7.0-7.5, and dried at 60℃ under vacuum to obtain a porous adsorbent.

[0071] The porous adsorbent of this example was subjected to thermogravimetric analysis (TG), and the results are shown in Figure 2Td(5%, N2) > 300°C, indicating that it has good heat resistance. The specific surface area of the porous adsorbent was tested by gas adsorption method, and the specific surface area was 630 m 2 / g.

[0072] The porous adsorbent described in this example was used to remove trace amounts of colored substances in 2, 5-furan dicarboxylic acid, and the specific process parameters and removal effects are shown in Table 1.

[0073] Example 3

[0074] Dissolve 1 mol of p-phenylenediamine in methanol to form a 10% mass fraction solution, and keep the temperature at 50°C. Dissolve 1 mol of glutaraldehyde in water to form a 10% mass concentration glutaraldehyde aqueous solution, and keep the temperature at 50°C. Add the glutaraldehyde aqueous solution to the p-phenylenediamine solution at a rate of 10 mL / h, and stir at 300 rpm. After the addition is completed, continue stirring for 2 hours. Filter and collect the precipitate, wash with methanol and water until the pH value is 7.0-7.5, and vacuum dry at 60°C to obtain the porous adsorbent.

[0075] Test the specific surface area of the porous adsorbent by gas adsorption method, and the specific surface area is 540 m 2 / g.

[0076] The porous adsorbent described in this example was used to remove trace amounts of colored substances in 2, 5-furan dicarboxylic acid, and the specific process parameters and removal effects are shown in Table 1.

[0077] Example 4

[0078] Dissolve 1.5 mol of m-xylylenediamine in ethanol to form a 10% mass fraction solution, and keep the temperature at 50°C. Dissolve 1 mol of 2, 5-furan dicarboxaldehyde in methanol to form a 10% mass concentration 2, 5-furan dicarboxaldehyde-methanol solution, and keep the temperature at 50°C. Add the m-xylylenediamine-ethanol solution to the 2, 5-furan dicarboxaldehyde solution at a rate of 1 mL / h, and stir at 300 rpm. After the addition is completed, continue stirring for 2 hours. Filter and collect the precipitate, wash with methanol and water until the pH value is 7.0-7.5, and vacuum dry at 60°C to obtain the porous adsorbent.

[0079] Test the specific surface area of the porous adsorbent by gas adsorption method, and the specific surface area is 690 m 2 / g. The Fourier infrared spectrum of the adsorbent synthesized in this example is shown in Figure 3 Table 1, and compared with 2, 5-furan dicarboxaldehyde and m-xylylenediamine, the synthesized adsorbent obviously generates a C=N double bond, and the -NH2 group is obviously weakened, indicating that the amino group and the aldehyde group form a -C=N- connection.

[0080] The porous adsorbent described in the example is used to remove trace colored substances in 2,5-furanic acid. The specific process parameters and removal effects are shown in Table 1.

[0081] Example 5

[0082] 1.2 mol of m-phenylenediamine and 0.8 mol of ethylenediamine are dissolved in ethylene glycol to form a 20% mass fraction solution, and the temperature is kept at 100°C. 2 mol of suberic aldehyde is dissolved in ethylene glycol to form a 20% mass fraction suberic aldehyde-ethylene glycol solution, and the temperature is kept at 100°C. The suberic aldehyde-ethylene glycol solution is added dropwise into the diamine-containing mixed solution at a speed of 30 mL / h, and reflux reaction is carried out with 600 rpm stirring. After the dropwise addition is completed, the stirring is continued for 0.5 hours. The precipitate is collected by filtration, washed with water to a pH value of 7.0-7.5, and vacuum dried at 60°C to obtain the porous adsorbent.

[0083] The specific surface area is tested by gas adsorption, and the specific surface area is 570 m 2 / g.

[0084] The porous adsorbent described in the example is used to remove trace colored substances in 2,5-furanic acid. The specific process parameters and removal effects are shown in Table 1.

[0085] Example 6

[0086] 1 mol of octanediamine is dissolved in ethanol to form a 10% mass fraction solution, and the temperature is kept at 50°C. 1 mol of o-phthaldehyde is dissolved in methanol to form a 10% mass fraction o-phthaldehyde-methanol solution, and the temperature is kept at 50°C. The octanediamine-ethanol solution is added dropwise into the o-phthaldehyde solution at a dropwise addition speed of 30 mL / h, and stirred at 300 rpm. After the dropwise addition is completed, the stirring is continued for 12 hours. The precipitate is collected by filtration, washed with methanol and water to a pH value of 7.0-7.5, and vacuum dried at 60°C to obtain the porous adsorbent.

[0087] The specific surface area is tested by gas adsorption, and the specific surface area is 640 m 2 / g.

[0088] The porous adsorbent described in the example is used to remove trace colored substances in 2,5-furanic acid. The specific process parameters and removal effects are shown in Table 1.

[0089] Example 7

[0090] Dissolve 1 mol of ethylenediamine in isopropanol to form a 10% by mass solution, and keep the temperature at 80°C. Dissolve 1 mol of 2,5-furandicarboxaldehyde in methanol to form a 10% by mass 2,5-furandicarboxaldehyde-methanol solution, and keep the temperature at 80°C. Add the ethylenediamine-isopropanol solution to the 2,5-furandicarboxaldehyde solution at a dropwise addition rate of 20 mL / h, and stir at 300 rpm. After the dropwise addition is completed, continue stirring for 6 hours. Filter and collect the precipitate, wash with methanol and water until the pH is 7.0-7.5, and dry under vacuum at 60°C to obtain the porous adsorbent.

[0091] The specific surface area is tested by gas adsorption, and the specific surface area is 710 m 2 / g.

[0092] The porous adsorbent described in this example is used to remove trace amounts of colored substances in 2,5-furandicarboxylic acid, and the specific process parameters and removal effects are shown in Table 1.

[0093] Example 8

[0094] Dissolve 1 mol of ethylenediamine in isopropanol to form a 10% by mass solution, and keep the temperature at 80°C. Dissolve 1 mol of 2,5-furandicarboxaldehyde in methanol to form a 10% by mass 2,5-furandicarboxaldehyde-methanol solution, and keep the temperature at 80°C. Add the ethylenediamine-isopropanol solution to the 2,5-furandicarboxaldehyde solution at a dropwise addition rate of 20 mL / h, and stir at 300 rpm. After the dropwise addition is completed, continue stirring for 6 hours. Filter and collect the precipitate, wash with methanol and water until the pH is 7.0-7.5, and dry under vacuum at 60°C to obtain the porous adsorbent.

[0095] The specific surface area is tested by gas adsorption, and the specific surface area is 710 m 2 / g.

[0096] The porous adsorbent described in this example is used to remove trace amounts of colored substances in 2,5-furandicarboxylic acid, and the specific process parameters and removal effects are shown in Table 1.

[0097] Example 9

[0098] Dissolve 1 mol of ethylenediamine in isopropanol to form a 10% by mass solution, and keep the temperature at 80°C. Dissolve 1 mol of 2,5-furandicarboxaldehyde in methanol to form a 10% by mass 2,5-furandicarboxaldehyde-methanol solution, and keep the temperature at 80°C. Add the ethylenediamine-isopropanol solution to the 2,5-furandicarboxaldehyde solution at a dropwise addition rate of 20 mL / h, and stir at 300 rpm. After the dropwise addition is completed, continue stirring for 6 hours. Filter and collect the precipitate, wash with methanol and water until the pH is 7.0-7.5, and dry under vacuum at 60°C to obtain the porous adsorbent.

[0099] The specific surface area was measured using gas adsorption, and the specific surface area was 660 m². 2 / g.

[0100] The porous adsorbent described in this embodiment was used to remove trace colored substances from 2,5-furandicarboxylic acid. The specific process parameters and removal effect are shown in Table 1.

[0101] Example 10

[0102] 2 mol of tris(2-aminoethyl)amine was dissolved in toluene to prepare a 30% (w / w) solution, and the solution was kept at a constant temperature of 40°C. 2.4 mol of terephthalaldehyde was dissolved in toluene to prepare a 30% (w / w) terephthalaldehyde-toluene solution, and the solution was kept at a constant temperature of 40°C. The tris(2-aminoethyl)amine-toluene solution was added dropwise to the terephthalaldehyde solution at a rate of 10 mL / h, with stirring at 200 rpm. After the addition was complete, stirring was continued for 8 hours. The precipitate was filtered and collected, washed with water until the pH reached 7.0–7.5, and then dried under vacuum at 120°C to obtain the adsorbent for later use. The specific surface area was measured using gas adsorption, and the specific surface area was 770 m². 2 / g.

[0103] The porous adsorbent described in this embodiment is used to remove trace colored substances from 2,5-furandicarboxylic acid. Figure 1 This is a schematic diagram of the method for removing colored substances from 2,5-furandicarboxylic acid by adsorbing with a porous adsorbent in an embodiment of the present invention. The specific process parameters and removal effects are shown in Table 1.

[0104] The adsorption effect of the porous adsorbents prepared in the above embodiments was tested, and the details are as follows:

[0105] FDCA with colored substance concentrations of 1000 ppm, 500 ppm, 200 ppm, and 100 ppm were used as samples for batch adsorption and fixed-bed adsorption experiments, respectively. In batch adsorption, the FDCA concentration depended on the solubility of FDCA in each solvent, and saturated solutions of the respective solvents at the specified temperature were prepared. The solvents used are shown in Table 1. The adsorbent dosage in batch adsorption was expressed as the mass ratio of adsorbent to FDCA. In fixed-bed adsorption, the adsorbent dosage was expressed as space velocity (in FDCA), i.e., the flow rate of the FDCA solution (unit: cm). 3 / h) divided by adsorbent loading (cm) 3 Airspeed is measured in h. -1 .

[0106] Table 1 shows the adsorption effect of the porous adsorbent in the relevant examples.

[0107]

[0108] In summary, the porous adsorbent formed by using aldehyde and amine contains high-temperature resistant chemical bonds (-RC=N-), so it has good high-temperature thermal stability and can be used in high-temperature environment; the reaction activity of the amino group on the porous adsorbent and the carboxyl group on the colored substance and the carboxyl group on the FDCA is poor, so that the colored substance in the FDCA is removed specifically; the porous adsorbent has high-efficiency adsorption performance with chemical adsorption as the main and physical adsorption as the auxiliary. The decolorization method can remove trace colored substances (1000 ppm or less) in the FDCA, and the decolorization rate is more than 95%, which significantly improves the color quality of the FDCA and meets the requirements of polymerization grade.

[0109] Aspects, embodiments, features, and examples of the present application should be considered in all respects as illustrative only and not restrictive, the scope of the present application being defined only by the claims. Other embodiments, modifications, and uses thereof will occur to those skilled in the art upon consideration of the specification, and it is intended to cover all such embodiments, modifications, and uses within the scope of the claimed application.

[0110] In addition, the present inventors have also carried out tests with other raw materials, process operations and process conditions described in the specification with reference to the foregoing embodiments, and all have obtained relatively ideal results.

[0111] Although the present application has been described with reference to illustrative embodiments, workers skilled in the art will recognize that various other changes, omissions, and / or additions can be made thereto and still fall within the spirit and scope of the application, as set forth in the following claims. In addition, many modifications can be made to adapt a particular situation or material to the teachings of the application without departing from the scope thereof. Therefore, the present disclosure is not intended to be limited to the disclosed embodiments beyond the scope of the claims presented below. Moreover, unless specifically stated otherwise, any use of the terms first, second, etc. do not denote any order or importance, but rather the terms first, second, etc. are used to distinguish one element from another.

Claims

1. A method for removing trace colored substances from 2,5-furandicarboxylic acid, characterized in that, include: A amine compound and an organic compound containing a dialdehyde group are mixed in a first solvent and reacted to obtain a porous adsorbent. The 2,5-furandicarboxylic acid to be decolorized is dissolved in a second solvent to form a 2,5-furandicarboxylic acid solution. Under a temperature of 100-200°C, the porous adsorbent is mixed and contacted with the 2,5-furandicarboxylic acid solution, thereby allowing trace colored substances in the 2,5-furandicarboxylic acid to be adsorbed by the porous adsorbent and removed from the 2,5-furandicarboxylic acid.

2. The method for removing trace colored substances from 2,5-furandicarboxylic acid according to claim 1, characterized in that: The amine compounds include ammonia gas, ammonia water, aromatic diamines, and C2-C4 compounds. 12 One or more of alkyl diamines and polyamines.

3. The method for removing trace colored substances from 2,5-furandicarboxylic acid according to claim 1, characterized in that: The organic compounds containing dialdehyde groups include C2 to C3 groups. 10 It is one or a combination of alkane dialdehydes and aromatic dialdehydes.

4. The method for removing trace colored substances from 2,5-furandicarboxylic acid according to claim 2, characterized in that: The aromatic diamine includes one or more of p-phenylenediamine, p-phenylenediamine, m-phenylenediamine, o-phenylenediamine, and o-phenylenediamine; the C2-C 12 Alkyl diamines include one or more of ethylenediamine, propylenediamine, oxalyldiamine, octyldiamine, adipamide, pyridine-3,5-diamine, maleic acid diamine, and 2,2-dimethyl-1,3-propanediamine; the polyamines include one or more of diethylenetriamine, N-butylthiophosphate triamine, bis(hexamethylene)triamine, pyrimidine-4,5,6-triamine, 4H-1,2,4-triazole-3,4,5-triamine, tris(2-aminoethyl)amine, and tris(4-aminophenyl)amine.

5. The method for removing trace colored substances from 2,5-furandicarboxylic acid according to claim 3, characterized in that: The C2~C 10 The alkane dialdehydes include glutaraldehyde and / or octanedialdehyde; the aromatic ring dialdehydes include one or a combination of o-phthalaldehyde, iso-phthalaldehyde, terephthalaldehyde, and furanyl dialdehyde.

6. The method for removing trace colored substances from 2,5-furandicarboxylic acid according to claim 1, characterized in that: The first solvent includes C1 to C2. 10 It can be one or a combination of alkyl alcohol solvents, alkane solvents, amide solvents, pyrrolidone solvents, organic acid solvents, or water.

7. The method for removing trace colored substances from 2,5-furandicarboxylic acid according to claim 6, characterized in that: The C1~C 10 The alkyl alcohol solvents include one or more of methanol, ethanol, cyclohexanol, isopropanol, n-octanol, decanol, or ethylene glycol; the alkane solvents include one or more of dichloromethane, chloroform, n-hexane, cyclohexane, n-octane, benzene, or toluene; and the amide solvents include N,N-dimethylformamide and / or N,N-dimethylacetamide.

8. The method for removing trace colored substances from 2,5-furandicarboxylic acid according to claim 1, characterized in that, The reaction temperature for preparing the porous adsorbent is 20–100 °C.

9. The method for removing trace colored substances from 2,5-furandicarboxylic acid according to claim 1, characterized in that: The molar ratio of the amine compound to the organic compound containing a dialdehyde group is 2:3 to 3:

1.

10. The method for removing trace colored substances from 2,5-furandicarboxylic acid according to claim 1, characterized in that: The mass concentrations of the amine compounds and the organic compounds containing dialdehyde groups are 10% to 60%, respectively.

11. The method for removing trace colored substances from 2,5-furandicarboxylic acid according to claim 1, characterized in that: The reaction time for preparing the porous adsorbent is 0.5 to 24 hours.

12. The method for removing trace colored substances from 2,5-furandicarboxylic acid according to claim 1, characterized in that: The second solvent includes one or a combination of water, alcohol solvents, alkane solvents, sulfoxide solvents, amide solvents, pyrrolidone solvents, organic acid solvents, or ionic liquids.

13. The method for removing trace colored substances from 2,5-furandicarboxylic acid according to claim 12, characterized in that: The alcohol solvents include one or more of methanol, ethanol, butanol, isopropanol, octanol, decanol, or ethylene glycol; the alkane solvents include one or more of dichloromethane, chloroform, n-hexane, cyclohexane, n-octane, benzene, or toluene; the sulfoxide solvents include thionyl chloride and / or dimethyl sulfoxide; the amide solvents include N,N-dimethylformamide and / or N,N-dimethylacetamide; the pyrrolidone solvents include N-methylpyrrolidone; the organic acid solvents include one or more of acetic acid, propionic acid, and trifluoroacetic acid; and the ionic liquids include one or more of quaternary ammonium ionic liquids, imidazole ionic liquids, and pyridine ionic liquids.

14. The method for removing trace colored substances from 2,5-furandicarboxylic acid according to claim 1, characterized in that: The colored substances include those containing carboxyl groups formed during the oxidation of saccharide organics in the preparation of 2,5-furandicarboxylic acid using saccharide organics as raw materials.

15. The method for removing trace colored substances from 2,5-furandicarboxylic acid according to claim 1, characterized in that: The removal method can remove colored substances with a content of less than 1000 ppm from 2,5-furandicarboxylic acid samples.

16. The method for removing trace colored substances from 2,5-furandicarboxylic acid according to claim 15, characterized in that: The removal method can remove colored substances with a content of less than 200 ppm from 2,5-furandicarboxylic acid samples.

17. The method for removing trace colored substances from 2,5-furandicarboxylic acid according to claim 1, characterized in that, The porous adsorbent is mixed and contacted with a 2,5-furandicarboxylic acid solution at a temperature of 140–160°C to carry out adsorption.

18. The method for removing trace colored substances from 2,5-furandicarboxylic acid according to claim 1, characterized in that: The contact time between the porous adsorbent and the 2,5-furandicarboxylic acid to be decolorized is 10 min to 12 h.

19. The method for removing trace colored substances from 2,5-furandicarboxylic acid according to claim 1, characterized in that: The adsorption is carried out using batch adsorption and / or fixed-bed adsorption.

20. The method for removing trace colored substances from 2,5-furandicarboxylic acid according to claim 19, characterized in that: In the batch adsorption method, the amount of the porous adsorbent is 1 to 20 wt% of the mass of 2,5-furandicarboxylic acid.

21. The method for removing trace colored substances from 2,5-furandicarboxylic acid according to claim 20, characterized in that: The amount of the porous adsorbent used is 5 to 10 wt% of the mass of 2,5-furandicarboxylic acid.

22. The method for removing trace colored substances from 2,5-furandicarboxylic acid according to claim 19, characterized in that: In the fixed-bed adsorption method, the space velocity of 2,5-furandicarboxylic acid is 10 h⁻¹. -1 ~100h -1 .

23. The method for removing trace colored substances from 2,5-furandicarboxylic acid according to claim 22, characterized in that: The space velocity of 2,5-furandicarboxylic acid was 40 h⁻¹. -1 ~60h -1 .

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