Efficient hexanediol purification process based on membrane separation technology

Abstract

The invention relates to the technical field of hexanediol purification, in particular to a high-efficiency hexanediol purification process based on a membrane separation technology, which comprises the following specific steps: removing metal ions from a hexanediol raw material through ion exchange resin; adding the di-tert-butyl p-cresol concentrated solution into the raw materials to obtain a mixed solution; adding the buffer solution into the mixed solution and stirring; adding peroxyformic acid into the mixed solution for reaction; after the reaction is finished, neutralizing with sodium carbonate, and then carrying out extraction treatment; the method comprises the following steps: separating hexanediol through an ultrafiltration membrane and a nanofiltration membrane, and then carrying out reverse osmosis treatment; the hexanediol is obtained. According to the method, peroxyformic acid is added, and organic impurities containing double bonds can be oxidized into functional groups such as epoxy groups or hydroxyl groups, so that the chemical properties of the impurities are changed, the impurities are more easily separated from hexanediol in the subsequent treatment processes such as extraction, and the purity of hexanediol is more favorably improved.

Description

Technical Field

[0001] The invention relates to the technical field of hexanediol purification, in particular to a hexanediol high-efficiency purification process based on membrane separation technology. Background Art

[0002] As an important chemical raw material, hexanediol is widely used in the synthesis of polymer materials such as polyester and polyurethane. In these applications, the purity requirements for hexanediol are getting higher and higher. For example, in the production of high-end polyester fibers, high-purity hexanediol can improve the strength, glossiness and anti-aging properties of the fibers, thereby meeting the production needs of high-quality products. In the pharmaceutical industry, hexanediol is required to have extremely high purity to ensure the safety and effectiveness of drugs; while the cosmetics industry requires high-purity hexanediol to ensure product quality and stability. For example, in skin care products, high-purity hexanediol can be used as a moisturizer and solvent to improve the texture and use effect of the product.

[0003] The traditional distillation method consumes huge energy in the process of hexanediol purification. Because hexanediol has a high boiling point, a large amount of heat energy is required to vaporize hexanediol during distillation, which not only increases production costs, but also does not meet the requirements of energy conservation and emission reduction under the background of increasingly tight energy. The traditional extraction method often has the problem of low separation efficiency when separating hexanediol and impurities. The extraction process may require multiple repeated operations to achieve a good separation effect. Moreover, for some impurities and hexanediol with similar properties, it is difficult to achieve complete separation through simple extraction. In view of this, we propose an efficient hexanediol purification process based on membrane separation technology. Summary of the invention

[0004] The object of the present invention is to provide an efficient purification process for hexanediol based on membrane separation technology, so as to solve the problem that when separating hexanediol and impurities, the separation efficiency is often low, the extraction process may require repeated operations to achieve a good separation effect, and it is difficult to achieve complete separation of some impurities and hexanediol with similar properties by simple extraction.

[0005] To achieve the above object, the present invention provides a high-efficiency purification process for hexanediol based on membrane separation technology, comprising the following steps:

[0006] S1.1, filter the hexanediol raw material, and then pass it through an activated ion exchange resin at a flow rate of 0.5-3 bed volumes / h and a temperature set at 20-40°C to remove polyvalent metal ions;

[0007] Ion exchange resins are highly selective. For polyvalent metal ions (such as calcium, magnesium, iron, etc.) in the hexanediol raw material solution, they can undergo exchange reactions with the specific functional groups on the ion exchange resins, thereby removing these metal ions from the raw material solution. For example, strongly acidic cation exchange resins carry sulfonic acid groups (-SO 3 H) can be exchanged with metal cations. This selective removal method can accurately remove the multivalent metal ions that affect the purity and subsequent processing performance of hexanediol without significantly affecting the structure and properties of hexanediol itself.

[0008] S1.2, dissolving di-tert-butyl-p-cresol in ethanol, stirring at a speed of 100-200 rpm at room temperature to obtain a di-tert-butyl-p-cresol concentrate with a concentration of 5-10%; adding the di-tert-butyl-p-cresol concentrate to the hexanediol raw material treated with the resin, and continuing to stir to obtain a mixed solution;

[0009] S1.3, dissolving the buffer in deionized water, stirring thoroughly until dissolved, to obtain a buffer solution with a concentration of 0.05-0.2 mol / L; adding the buffer solution to the mixed solution, stirring continuously at a speed of 200-500 rpm at room temperature with a magnetic stirrer until the pH value of the mixed solution reaches 6-8;

[0010] S1.4, adding peroxyformic acid with a concentration of 0.5-2% to the mixed solution, stirring continuously at a speed of 200-500rpm at a temperature of 25-35°C for 1-2h; after the reaction is completed, neutralizing the remaining peroxyformic acid with sodium carbonate to obtain a hexylene glycol solution containing formic acid and acetic acid, and then extracting the solution to obtain a pretreated hexylene glycol solution;

[0011] Performic acid can selectively treat impurities in hexanediol raw material solution through oxidation reaction. In the production process of hexanediol, performic acid can oxidize organic impurities containing double bonds into functional groups such as epoxy or hydroxyl groups, thereby changing the chemical properties of these impurities. This change makes it easier to separate the impurities from hexanediol in subsequent treatment processes such as extraction. At the same time, the products of performic acid oxidation are relatively easy to handle, and the by-products such as formic acid and acetic acid usually produced can be separated from the hexanediol solution through extraction treatment. Compared with the complex and difficult-to-separate by-products that may be produced by some other oxidants, the products of performic acid oxidation are easier to remove, which is more conducive to improving the purity of hexanediol.

[0012] The main function of di-tert-butyl-p-cresol is to protect hexanediol from oxidation by reacting preferentially with oxidizing factors. This characteristic can significantly reduce the occurrence of oxidative side reactions and ensure the purity of hexanediol. In the subsequent process of adding buffers and oxidants, the chemical environment of hexanediol changes, and the presence of di-tert-butyl-p-cresol helps to maintain the chemical stability of hexanediol, so that it will not undergo structural changes due to oxidation, thereby maintaining a high purity in the subsequent processing process.

[0013] S1.5, treating the pretreated hexanediol solution through an ultrafiltration membrane separation system, wherein the system pressure is set to 0.1-0.4 MPa, the transmembrane pressure difference is set to 0.1-0.5 MPa, and the hexanediol solution flows through the ultrafiltration membrane at a temperature of 20-40° C. at a flow rate of 1-3 m / s to obtain a preliminarily purified hexanediol solution;

[0014] S1.6, the preliminarily purified hexanediol solution is separated again by a nanofiltration membrane made of sulfonated polyethersulfone, the molecular weight cutoff of the nanofiltration membrane is 500-800Da;

[0015] S1.7. Pass the hexanediol solution in S1.6 through a polyamide composite membrane to obtain purified hexanediol.

[0016] Ultrafiltration membranes are mainly used to remove macromolecular substances in solutions, such as polymers, protein impurities and colloids produced by polymerization reactions. These macromolecular substances cannot pass through ultrafiltration membranes due to their large molecular weight (usually between 1000 and 300,000 Daltons), and are thus retained on one side of the membrane to achieve preliminary purification; the pore size of nanofiltration membranes is between 0.001-0.01 μm, which can effectively retain some small molecular organic matter and salts, but allow hexanediol molecules to pass through. This selective retention makes nanofiltration membranes very effective in further purifying hexanediol solutions; reverse osmosis membranes are used for deep purification, and can almost completely retain the remaining small molecular impurities and salts, thereby greatly improving the purity of hexanediol.

[0017] Preferably, in S1.1, the ion exchange resin is any one of 732 strong acid styrene cation exchange resin or CD552 resin.

[0018] Preferably, in S1.2, the stirring is performed with a stirrer at a speed of 200-500 rpm and a stirring time of 10-30 min.

[0019] Preferably, in S1.3, the buffer is any one of potassium dihydrogen phosphate and sodium dihydrogen phosphate.

[0020] Preferably, in S1.3, the mixture is stirred thoroughly with a stirrer at a speed of 200-400 rpm for a time of 10-30 min.

[0021] Preferably, in S1.4, the extraction treatment is to add the hexanediol solution containing formic acid and acetic acid and isopropanol into a separatory funnel, invert it 10-15 times to fully mix the two phases, let it stand for 5-10 minutes, and let the two phases separate naturally; collect the upper liquid and heat it through a rotary evaporator to obtain a pretreated hexanediol solution.

[0022] Preferably, the vacuum degree of the rotary evaporator is 20-50 mmHg, the temperature is 40-50°C, the rotation speed is 80-120 rpm, and the condenser temperature is -10 to -20°C.

[0023] Preferably, in S1.5, the material of the ultrafiltration membrane is any one of polyethersulfone or polyvinylidene fluoride, and the molecular weight cutoff of the ultrafiltration membrane is 1000-10000Da.

[0024] Preferably, in S1.6, the pressure of the nanofiltration membrane separation system is 0.5MPa-2MPa, the temperature is 20°C-40°C, the flow rate is 1-3m / s, and the transmembrane pressure difference is 0.1-0.5MPa.

[0025] Preferably, in S1.7, the hexanediol solution is subjected to reverse osmosis treatment through a polyamide composite membrane at a temperature of 15-40°C at a flow rate of 0.5-2 m / s, the system pressure is 1-10 MPa, and the transmembrane pressure difference is 0.5-2 MPa.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] 1. In the high-efficiency purification process of hexanediol based on membrane separation technology, performic acid is added. Since performic acid can selectively treat impurities in the hexanediol raw material solution through oxidation reaction, in the production process of hexanediol, performic acid can oxidize organic impurities containing double bonds into functional groups such as epoxy groups or hydroxyl groups, thereby changing the chemical properties of these impurities, making them easier to separate from hexanediol in subsequent extraction and other treatment processes, which is more conducive to improving the purity of hexanediol.

[0028] 2. In the efficient purification process of hexanediol based on membrane separation technology, the addition of di-tert-butyl-p-cresol plays an important role in maintaining the chemical stability of hexanediol. In the subsequent process of adding oxidants, the chemical environment of hexanediol will change, and di-tert-butyl-p-cresol can effectively prevent hexanediol from undergoing structural changes due to oxidation, thereby maintaining a high purity in the subsequent processing process. DETAILED DESCRIPTION

[0029] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] Activation of ion exchange resin: First, soak the resin in deionized water to fully swell it, soak it in 5% hydrochloric acid solution for 3 hours, and then rinse it with deionized water until it is neutral; then soak it in 5% sodium hydroxide solution for 3 hours, and then load the treated resin into the ion exchange column.

[0031] The ion exchange resin is any one of 732 strong acid styrene cation exchange resin or CD552 resin, preferably CD552 resin.

[0032] The buffer is any one of potassium dihydrogen phosphate and sodium dihydrogen phosphate, preferably potassium dihydrogen phosphate.

[0033] The material of the ultrafiltration membrane is any one of polyethersulfone or polyvinylidene fluoride, preferably polyvinylidene fluoride.

[0034] Example 1: A highly efficient purification process for hexanediol based on membrane separation technology, comprising the following steps:

[0035] S1.1, filter the hexanediol raw material, and then pass it through an activated ion exchange resin at a flow rate of 2 bed volumes / h and the temperature is set at 30°C to remove multivalent metal ions;

[0036] S1.2, dissolving di-tert-butyl-p-cresol in ethanol, stirring at a speed of 150 rpm at room temperature to obtain a di-tert-butyl-p-cresol concentrate with a concentration of 8%; adding the di-tert-butyl-p-cresol concentrate to the hexylene glycol raw material treated with the resin, and continuing to stir with a stirrer at a speed of 300 rpm for 30 minutes to obtain a mixed solution;

[0037] S1.3, dissolve potassium dihydrogen phosphate buffer in deionized water, stir with a stirrer at 400 rpm until dissolved, the stirring time is 30 min, and obtain a buffer solution with a concentration of 0.1 mol / L; add the buffer solution to the mixed solution, and continue stirring with a magnetic stirrer at 400 rpm at room temperature until the pH value of the mixed solution reaches 7;

[0038] S1.4, adding 0.5% peroxyformic acid to the mixed solution, stirring continuously at 300 rpm at a temperature of 35°C for 2 hours; after the reaction is completed, neutralizing the remaining peroxyformic acid with sodium carbonate to obtain a hexylene glycol solution containing formic acid and acetic acid, and then extracting the solution;

[0039] Add the hexanediol solution containing formic acid and acetic acid and isopropanol into a separatory funnel, invert it 15 times to fully mix the two phases, let it stand for 10 minutes, and let the two phases separate naturally; collect the upper liquid and heat it through a rotary evaporator, the vacuum degree of the rotary evaporator is 30 mmHg, the temperature is 40°C, the rotation speed is 100 rpm, and the condenser temperature is -15°C to obtain a pretreated hexanediol solution;

[0040] S1.5, treating the pretreated hexanediol solution through an ultrafiltration membrane separation system made of polyvinylidene fluoride, wherein the system pressure is set to 0.4 MPa, the transmembrane pressure difference is set to 0.3 MPa, and the hexanediol solution flows through the ultrafiltration membrane at a flow rate of 2 m / s at a temperature of 30°C, and the molecular weight cutoff of the ultrafiltration membrane is 5000 Da, thereby obtaining a preliminarily purified hexanediol solution;

[0041] S1.6, the preliminarily purified hexanediol solution is separated again by a nanofiltration membrane made of sulfonated polyethersulfone, the molecular weight cutoff of the nanofiltration membrane is 600Da; the pressure of the nanofiltration membrane separation system is 1.52MPa, the temperature is 40°C, the flow rate is 2m / s, and the transmembrane pressure difference is 0.3MPa;

[0042] S1.7. The hexanediol solution in S1.6 is passed through a polyamide composite membrane and subjected to reverse osmosis treatment at a temperature of 25°C and a flow rate of 1.5 m / s. The system pressure is 6 MPa and the transmembrane pressure difference is 1.5 MPa to obtain purified hexanediol.

[0043] Example 2: A highly efficient purification process for hexanediol based on membrane separation technology, comprising the following steps:

[0044] S1.1, filter the hexanediol raw material, and then pass it through an activated ion exchange resin at a flow rate of 2 bed volumes / h and the temperature is set at 30°C to remove multivalent metal ions;

[0045] S1.2, dissolving di-tert-butyl-p-cresol in ethanol, stirring at a speed of 150 rpm at room temperature to obtain a di-tert-butyl-p-cresol concentrate with a concentration of 8%; adding the di-tert-butyl-p-cresol concentrate to the hexylene glycol raw material treated with the resin, and continuing to stir with a stirrer at a speed of 300 rpm for 30 minutes to obtain a mixed solution;

[0046] S1.3, dissolve potassium dihydrogen phosphate buffer in deionized water, stir with a stirrer at 400 rpm until dissolved, the stirring time is 30 min, and obtain a buffer solution with a concentration of 0.1 mol / L; add the buffer solution to the mixed solution, and continue stirring with a magnetic stirrer at 400 rpm at room temperature until the pH value of the mixed solution reaches 7;

[0047] S1.4, adding 1% peroxyformic acid to the mixed solution, stirring continuously at 300 rpm at a temperature of 35°C for 2 hours; after the reaction is completed, neutralizing the remaining peroxyformic acid with sodium carbonate to obtain a hexylene glycol solution containing formic acid and acetic acid, and then extracting the solution;

[0048] Add the hexanediol solution containing formic acid and acetic acid and isopropanol into a separatory funnel, invert it 15 times to fully mix the two phases, let it stand for 10 minutes, and let the two phases separate naturally; collect the upper liquid and heat it through a rotary evaporator, the vacuum degree of the rotary evaporator is 30 mmHg, the temperature is 40°C, the rotation speed is 100 rpm, and the condenser temperature is -15°C to obtain a pretreated hexanediol solution;

[0049] S1.5, treating the pretreated hexanediol solution through an ultrafiltration membrane separation system made of polyvinylidene fluoride, wherein the system pressure is set to 0.4 MPa, the transmembrane pressure difference is set to 0.3 MPa, and the hexanediol solution flows through the ultrafiltration membrane at a flow rate of 2 m / s at a temperature of 30°C, and the molecular weight cutoff of the ultrafiltration membrane is 5000 Da, thereby obtaining a preliminarily purified hexanediol solution;

[0050] S1.6, the preliminarily purified hexanediol solution is separated again by a nanofiltration membrane made of sulfonated polyethersulfone, the molecular weight cutoff of the nanofiltration membrane is 600Da; the pressure of the nanofiltration membrane separation system is 1.52MPa, the temperature is 40°C, the flow rate is 2m / s, and the transmembrane pressure difference is 0.3MPa;

[0051] S1.7. The hexanediol solution in S1.6 is passed through a polyamide composite membrane and subjected to reverse osmosis treatment at a temperature of 25°C and a flow rate of 1.5 m / s. The system pressure is 6 MPa and the transmembrane pressure difference is 1.5 MPa to obtain purified hexanediol.

[0052] Example 3: A highly efficient purification process for hexanediol based on membrane separation technology, comprising the following steps:

[0053] S1.1, filter the hexanediol raw material, and then pass it through an activated ion exchange resin at a flow rate of 2 bed volumes / h and the temperature is set at 30°C to remove multivalent metal ions;

[0054] S1.2, dissolving di-tert-butyl-p-cresol in ethanol, stirring at a speed of 150 rpm at room temperature to obtain a di-tert-butyl-p-cresol concentrate with a concentration of 8%; adding the di-tert-butyl-p-cresol concentrate to the hexylene glycol raw material treated with the resin, and continuing to stir with a stirrer at a speed of 300 rpm for 30 minutes to obtain a mixed solution;

[0055] S1.3, dissolve potassium dihydrogen phosphate buffer in deionized water, stir with a stirrer at 400 rpm until dissolved, the stirring time is 30 min, and obtain a buffer solution with a concentration of 0.1 mol / L; add the buffer solution to the mixed solution, and continue stirring with a magnetic stirrer at 400 rpm at room temperature until the pH value of the mixed solution reaches 7;

[0056] S1.4, adding 1.5% peroxyformic acid to the mixed solution, stirring continuously at 300 rpm at a temperature of 35°C for 2 hours; after the reaction is completed, neutralizing the remaining peroxyformic acid with sodium carbonate to obtain a hexylene glycol solution containing formic acid and acetic acid, and then extracting the solution;

[0057] Add the hexanediol solution containing formic acid and acetic acid and isopropanol into a separatory funnel, invert it 15 times to fully mix the two phases, let it stand for 10 minutes, and let the two phases separate naturally; collect the upper liquid and heat it through a rotary evaporator, the vacuum degree of the rotary evaporator is 30 mmHg, the temperature is 40°C, the rotation speed is 100 rpm, and the condenser temperature is -15°C to obtain a pretreated hexanediol solution;

[0058] S1.5, treating the pretreated hexanediol solution through an ultrafiltration membrane separation system made of polyvinylidene fluoride, wherein the system pressure is set to 0.4 MPa, the transmembrane pressure difference is set to 0.3 MPa, and the hexanediol solution flows through the ultrafiltration membrane at a flow rate of 2 m / s at a temperature of 30°C, and the molecular weight cutoff of the ultrafiltration membrane is 5000 Da, thereby obtaining a preliminarily purified hexanediol solution;

[0059] S1.6, the preliminarily purified hexanediol solution is separated again by a nanofiltration membrane made of sulfonated polyethersulfone, the molecular weight cutoff of the nanofiltration membrane is 600Da; the pressure of the nanofiltration membrane separation system is 1.52MPa, the temperature is 40°C, the flow rate is 2m / s, and the transmembrane pressure difference is 0.3MPa;

[0060] S1.7. The hexanediol solution in S1.6 is passed through a polyamide composite membrane and subjected to reverse osmosis treatment at a temperature of 25°C and a flow rate of 1.5 m / s. The system pressure is 6 MPa and the transmembrane pressure difference is 1.5 MPa to obtain purified hexanediol.

[0061] Comparative Example 1

[0062] The method of Example 3 was used to remove peroxyformic acid.

[0063] Comparative Example 2

[0064] The method of Example 3 was used to remove di-tert-butyl-p-cresol.

[0065] Comparative Example 3

[0066] The method of Example 3 was adopted without using membrane separation technology.

[0067] The present invention provides a high-efficiency purification process for hexanediol based on membrane separation technology by pretreating hexanediol raw materials, wherein the inspection items and inspection standards of the purification process are as follows:

[0068] With reference to standard GB / T30305-2013, gas chromatography was adopted, n-butanol was used as solvent to dissolve the sample, the sample was vaporized under the selected working conditions and then separated by a capillary column, detected by a flame ionization detector (FID), and quantified by the area normalization method, to determine the purity of hexanediol; purity determination can directly reflect the effect of the purification process on impurity removal. If the purity reaches the expected standard, it indicates that the process can effectively separate the target substance from the impurities.

[0069] Several identical basic samples were selected, and a known amount of hexanediol was added to some of the samples as a standard to ensure that the added amount was within the expected concentration range. The same pretreatment and analysis process was performed on all samples (including the unspiked control group), and the difference in response values ​​between the spiked samples and the control group was compared to calculate the recovery rate. The stable high recovery rate was determined through multiple experiments, which proved that the purification process has good stability and reliability.

[0070] According to the above standards, the data obtained are shown in Table 1:

[0071] Table 1 Purity and recovery of hexanediol in Examples 1-3 and Comparative Examples 1-3

[0072] Implementation / Comparative Example purity% Recovery rate % Example 1 99.932 94.1 Example 2 99.935 94.2 Example 3 99.936 94.8 Comparative Example 1 88.782 66.3 Comparative Example 2 89.025 68.9 Comparative Example 3 88.385 64.2

[0073] It can be seen from Table 1 that the hexylene glycol in the raw materials in Examples 1-3 exhibits significantly high purity and high recovery rate; Taking Example 3 as the optimal example, combined with Comparative Example 1, it can be seen that when peroxyformic acid is removed, the purity and recovery rate of hexylene glycol in the raw materials are significantly reduced;

[0074] For organic impurities containing double bonds, performic acid can oxidize them into functional group compounds that are easier to separate. If performic acid is removed, these impurities will not be completely oxidized and converted, thereby interfering with the normal separation and recovery of hexanediol, making it difficult to effectively separate hexanediol from impurities, and ultimately affecting the purity and recovery rate of the product. In addition, the presence of performic acid is essential to maintaining the chemical balance of the reaction system. It can preferentially react with certain substances that may cause side reactions and effectively inhibit the occurrence of other adverse side reactions. Once performic acid is removed, some components in the system may undergo other types of reactions to generate new impurities, resulting in reduced purity and recovery rate of hexanediol.

[0075] Comparing Example 3 with Comparative Example 2, it can be seen that when di-tert-butyl-p-cresol is removed, the purity and recovery rate of hexylene glycol in the raw material are significantly reduced;

[0076] Di-tert-butyl-p-cresol can react with oxidizing factors preferentially, effectively blocking the propagation of the oxidation chain reaction. Once di-tert-butyl-p-cresol is removed, hexanediol loses a layer of antioxidant barrier and becomes easily oxidized, generating a variety of oxidation by-products including aldehydes and acids, which affect the purity of hexanediol. During the processing of hexanediol, without the protection provided by di-tert-butyl-p-cresol, even slight changes in the chemical environment may trigger adverse reactions such as decomposition or polymerization of hexanediol, forming additional pollutants, further weakening the purity of hexanediol, and increasing its loss in the separation process, ultimately affecting the recovery rate.

[0077] Furthermore, it can be seen from the comparison between the best example 3 and the comparative example 3 that when the membrane separation technology is not used,

[0078] The purity and recovery rate of pentanediol in the raw material are significantly reduced;

[0079] The purification of hexanediol usually uses traditional separation methods such as distillation and extraction. The distillation process consumes a lot of energy to vaporize the liquid, which increases the cost. In addition, it is difficult to achieve efficient separation of impurities with similar boiling points in hexanediol by conventional distillation, and they are easily evaporated together, thereby reducing the purity of hexanediol. The extraction separation method relies on the difference in the distribution coefficients of the solute in two immiscible solvents. However, in many common extraction solvent systems, the distribution coefficients of hexanediol and impurities are not much different, resulting in difficulty in completely separating hexanediol from the raw materials during the extraction process, thereby reducing the purity of hexanediol. At the same time, the extraction process may require multiple repeated operations to achieve a better separation effect, which will also lead to the loss of hexanediol and reduce the recovery rate.

[0080] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. The above embodiments and descriptions are only preferred examples of the present invention and are not intended to limit the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A highly efficient purification process for hexanediol based on membrane separation technology, characterized in that: The following steps are involved: S1.1, filter the hexanediol raw material, and then pass it through an activated ion exchange resin at a flow rate of 0.5-3 bed volumes / h and a temperature set at 20-40°C to remove polyvalent metal ions; S1.2, dissolving di-tert-butyl-p-cresol in ethanol, stirring at a speed of 100-200 rpm at room temperature to obtain a di-tert-butyl-p-cresol concentrate with a concentration of 5-10%; adding the di-tert-butyl-p-cresol concentrate to the hexanediol raw material treated with the resin, and continuing to stir to obtain a mixed solution; S1.3, dissolve the buffer in deionized water, stir thoroughly until dissolved, and obtain a buffer solution with a concentration of 0.05-0.2 mol / L; Add the buffer solution to the mixed solution, and continue stirring at 200-500 rpm with a magnetic stirrer at room temperature until the pH value of the mixed solution reaches 6-8; S1.4, adding peroxyformic acid with a concentration of 0.5-2% to the mixed solution, stirring continuously at a speed of 200-500rpm at a temperature of 25-35°C for 1-2h; after the reaction is completed, neutralizing the remaining peroxyformic acid with sodium carbonate to obtain a hexylene glycol solution containing formic acid and acetic acid, and then extracting the solution to obtain a pretreated hexylene glycol solution; S1.5, treating the pretreated hexanediol solution through an ultrafiltration membrane separation system, wherein the system pressure is set to 0.1-0.4 MPa, the transmembrane pressure difference is set to 0.1-0.5 MPa, and the hexanediol solution flows through the ultrafiltration membrane at a temperature of 20-40° C. at a flow rate of 1-3 m / s to obtain a preliminarily purified hexanediol solution; S1.6, the preliminarily purified hexanediol solution is separated again by a nanofiltration membrane made of sulfonated polyethersulfone, the molecular weight cutoff of the nanofiltration membrane is 500-800Da; S1.

7. Pass the hexanediol solution in S1.6 through a polyamide composite membrane to obtain purified hexanediol.

2. The high-efficiency purification process for hexanediol based on membrane separation technology according to claim 1, characterized in that: In the above S1.1, the ion exchange resin is any one of 732 strong acid styrene cation exchange resin or CD552 resin.

3. The high-efficiency purification process for hexanediol based on membrane separation technology according to claim 1, characterized in that: In S1.2, stirring is performed with a stirrer at a speed of 200-500 rpm and a stirring time of 10-30 min.

4. The high-efficiency purification process for hexanediol based on membrane separation technology according to claim 1, characterized in that: In the above S1.3, the buffer is any one of potassium dihydrogen phosphate and sodium dihydrogen phosphate.

5. The high-efficiency purification process for hexanediol based on membrane separation technology according to claim 1, characterized in that: In the above S1.3, the mixture is stirred thoroughly with a stirrer at a speed of 200-400 rpm for 10-30 min.

6. The high-efficiency purification process for hexanediol based on membrane separation technology according to claim 1, characterized in that: In S1.4, the extraction treatment is to add the hexylene glycol solution containing formic acid and acetic acid and isopropanol into a separatory funnel, invert it 10-15 times to fully mix the two phases, and let it stand for 5-10 minutes to allow the two phases to separate naturally; The upper liquid was collected and heated by a rotary evaporator to obtain a pretreated hexylene glycol solution.

7. The high-efficiency purification process for hexanediol based on membrane separation technology according to claim 6, characterized in that: The vacuum degree of the rotary evaporator is 20-50 mmHg, the temperature is 40-50°C, the rotation speed is 80-120 rpm, and the condenser temperature is -10 to -20°C.

8. The high-efficiency purification process for hexanediol based on membrane separation technology according to claim 1, characterized in that: In S1.5, the material of the ultrafiltration membrane is any one of polyethersulfone or polyvinylidene fluoride, and the molecular weight cutoff of the ultrafiltration membrane is 1000-10000Da.

9. The high-efficiency purification process for hexanediol based on membrane separation technology according to claim 1, characterized in that: In S1.6, the pressure of the nanofiltration membrane separation system is 0.5-2 MPa, the temperature is 20°C-40°C, the flow rate is 1-3 m / s, and the transmembrane pressure difference is 0.1-0.5 MPa.

10. The high-efficiency purification process for hexanediol based on membrane separation technology according to claim 1, characterized in that: In S1.7, the hexanediol solution is subjected to reverse osmosis treatment through the polyamide composite membrane at a temperature of 15-40° C. at a flow rate of 0.5-2 m / s, the system pressure is 1-10 MPa, and the transmembrane pressure difference is 0.5-2 MPa.