Purification method of organic solvent

Abstract

The invention provides an organic solvent purification method, which comprises: (1) contacting an organic solvent with a 3A molecular sieve adsorption column to obtain a first purification liquid, and embedding a carbon quantum dot coating on the inner wall of the 3A molecular sieve adsorption column; (2) contacting the primary purified solution in the step (1) with a 4A molecular sieve to obtain a secondary purified solution; (3) contacting the secondary purified solution obtained in the step (2) with a neutral alumina adsorption column to obtain a third purified solution; (4) adsorbing the third purified liquid in the step (3) through ion exchange resin to obtain a fourth purified liquid; (5) adsorbing the fourth purified solution in the step (4) through a NaA type polyamide molecular sieve membrane to obtain a purified organic solvent; according to the purification method disclosed by the invention, the near-anhydrous organic solvent with high purity not lower than 99.9% can be finally obtained, the moisture content can reach below 50ppm, the fluorescence wavelength is below 240nm, the absorbance is not higher than 0.1%, and the light transmittance is obviously increased.

Description

Technical Field

[0001] The present invention relates to the field of organic synthesis, and in particular to a method for purifying an organic solvent. Background Art

[0002] Organic solvents are a large class of organic compounds that are widely used in life and production. They have a small molecular weight and are present in coatings, adhesives, paints and detergents. They are liquid at room temperature. Organic solvents include many types of substances, such as alkanes, alkenes, alcohols, aldehydes, amines, esters, ethers, ketones, aromatic hydrocarbons, hydrogenated hydrocarbons, terpenes, halogenated hydrocarbons, heterocyclic compounds, nitrogen-containing compounds and sulfur-containing compounds, etc. Most of them are toxic to the human body. In chemical experiments and production, commonly used solvents include tetrahydrofuran, dichloromethane, ethyl acetate, acetone, acetonitrile and methanol, etc. These solvents have good solubility in reaction and treatment systems. However, in the experimental process of organic chemistry, the purity and water content of the solvent directly affect the efficiency of the reaction and the quality of the product. The commercially available solvents are generally industrial grade or analytical grade, and a distillation device needs to be set up to obtain refined solvents with high purity and low water content.

[0003] Currently, chemical methods are generally used to purify and dry solvents for optimal results. For example, for common solvents such as tetrahydrofuran and toluene, dehydration and impurity removal are typically performed in the laboratory using sodium wire reflux under a nitrogen atmosphere. For common solvents such as ethyl acetate and acetonitrile, calcium hydride can be used for distillation and dehydration under an inert gas atmosphere to remove impurities. While these methods are effective, they are energy-intensive and pose a high risk of safety hazards. In industrial production, CN200610033048.8 provides a method for purifying ethyl acetate by dehydration and refining in a distillation tower to isolate high-purity ethyl acetate, but this process is energy-intensive. CN200810038696.19 discloses a method for purifying and drying acetonitrile. This method involves adding polymer monomers to industrial-grade acetonitrile, adding an initiator, and heating to polymerize impurities. This is followed by distillation and separation to obtain a semi-finished acetonitrile with high transmittance. This is then electrochemically treated to obtain high-quality acetonitrile with low water content. This method yields a high-purity product, but the steps are complex, time-consuming, and costly, making industrial production of this method unsuitable. CN020022135230.5 discloses a process for dehydrating and purifying tetrahydrofuran, which involves reacting acetonitrile with water to form a high-boiling-point compound, heating the mixture to 80-90°C, and distilling the tetrahydrofuran. This method can reduce the water content of the tetrahydrofuran to below 100 ppm while removing mechanical impurities and other components, but it consumes a significant amount of energy. The acetone purification technology employed in CN200980149353.5 utilizes an alkaline and oxidizing reagent in conjunction with multiple distillation devices. However, this method is costly, complex, and difficult to operate.

[0004] Therefore, most of the current solvent purification methods have problems such as complex equipment, difficult operation and high cost. How to develop a new solvent purification method is of great significance for solvent purification and recycling. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the present invention aims to provide a method for purifying an organic solvent to solve the problems of complex equipment, difficult operation and high cost in most commonly used solvent purification methods.

[0006] To achieve this object, the present invention adopts the following technical solutions:

[0007] The present invention provides a method for purifying an organic solvent, which comprises the following steps:

[0008] (1) contacting an organic solvent with a 3A molecular sieve adsorption column to obtain a first purified solution, wherein the inner wall of the 3A molecular sieve adsorption column is embedded with a carbon quantum dot coating;

[0009] (2) contacting the first purified solution from step (1) with 4A molecular sieve to obtain a second purified solution;

[0010] (3) contacting the second purified solution from step (2) with a neutral alumina adsorption column to obtain a third purified solution;

[0011] (4) adsorbing the third purified solution in step (3) through an ion exchange resin to obtain a fourth purified solution;

[0012] (5) The fourth purified liquid in step (4) is adsorbed on a NaA type polyamide molecular sieve membrane to obtain a purified organic solvent.

[0013] The purification method provided by the present invention reduces energy consumption and a preparation process with simple purification steps to minimize purification costs. At the same time, the prepared common solvent can meet the requirements of anhydrous synthesis of pharmaceutical intermediates or materials, controls the water content to be below 50 ppm, and has an ultraviolet absorption absorbance of no more than 0.1% at a wavelength of 240 nm.

[0014] This application identifies a process flow for solvent purification by adsorption using a combination of several adsorbent materials, and finds that the method is universally applicable to methanol, ethanol, isopropanol, and acetonitrile. The adsorbent material, a NaA-type polyamide molecular sieve membrane, exhibits strong water absorption (low silicon-aluminum ratio) and pores with a molecular dynamics diameter of 0.41 nm.

[0015] The NaA type polyamide molecular sieve membrane used in the present invention has an octahedral cubic pore type and a pore size of 0.41 nm. The separation flux can reach no less than 10 kg / (m 2h), can absorb the residual water molecules in the above operation, and the separation purity can reach 99.9%.

[0016] In the present invention, the carbon quantum dot coating is a layered structure composed of zero-dimensional carbon nanomaterials, ultrafine, dispersed, quasi-spherical carbon nanoparticles with a size of less than 10nm.

[0017] Compared with the existing distillation, rectification or single adsorption steps, the water removal effect of the present invention is almost close to that of the pure product through the linkage of multiple steps.

[0018] In the present invention, the organic solvent is generally an aqueous analytical grade organic solvent.

[0019] Preferably, the organic solvent in step (1) is any one of methanol, ethanol, isopropanol or acetonitrile.

[0020] Preferably, the contact time in step (1) is 30 to 40 minutes, for example, 30 minutes, 33 minutes, 35 minutes, 38 minutes or 40 minutes.

[0021] In step (1), the 3A molecular sieve adsorption can achieve the effects of fast water absorption rate and strong water absorption capacity, and can remove most of the water in the solvent.

[0022] Preferably, the contact time in step (2) is 20 to 30 minutes, for example, 20 minutes, 25 minutes or 30 minutes.

[0023] In step (2), the 4A molecular sieve can further adsorb water molecules and can also adsorb a small amount of molecular residues such as methanol, ethanol, isopropanol and carbon dioxide.

[0024] In the present invention, a carbon quantum dot coating is embedded in the inner wall of the 3A molecular sieve adsorption column, and its fluorescence resonance energy transfer effect is used to monitor the adsorption saturation in real time. At the same time, a magnetic field-assisted molecular sieve regeneration system is introduced, and a superconducting magnet is used to generate a 0.5T magnetic field to directional arrange the adsorbed water molecules, thereby reducing the regeneration energy consumption by 70%.

[0025] Preferably, the mesh size of the neutral alumina in any one of step (3) is 100 to 150 meshes, for example, it can be 100 mesh, 110 mesh, 120 mesh, 130 mesh, 140 mesh or 150 mesh.

[0026] In step (3), neutral alumina can remove aldehydes, quinones, ketones, and unstable small molecular trace impurities in certain glycosides and acid-base solutions, greatly reducing the impurity content in the solvent.

[0027] Preferably, the contact time in step (3) is 20 to 30 minutes, for example, 20 minutes, 22 minutes, 25 minutes, 28 minutes or 30 minutes.

[0028] Preferably, the ion exchange resin in step (4) comprises an acidic ion exchange resin and / or a basic ion exchange resin.

[0029] Preferably, in step (4), trace acidic and alkaline impurities contained in the organic solvent can be removed.

[0030] Preferably, the adsorption time in step (4) is 10 to 20 minutes, for example, 10 minutes, 15 minutes or 20 minutes.

[0031] Preferably, the adsorption time in step (5) is 10 to 20 minutes, for example, 10 minutes, 15 minutes or 20 minutes.

[0032] Beneficial effects:

[0033] The purification method provided by the present invention can ultimately obtain a near-anhydrous organic solvent with a high purity of not less than 99.9%, a moisture content of less than 50 ppm, an absorbance of less than 0.1% at a fluorescence wavelength below 240 nm, and significantly increased transmittance. DETAILED DESCRIPTION

[0034] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention are clearly and completely described below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts are within the scope of protection of the present invention.

[0035] The acidic ion exchange resin used in the present invention is Amberlite-HPR8300H; the basic ion exchange resin is Amberlite(R)-IRA910.

[0036] Example 1

[0037] In this example, acetonitrile was purified by the following method

[0038] (1) Acetonitrile was contacted with a 3A molecular sieve adsorption column for 35 minutes to obtain a first purified solution, and the inner wall of the 3A molecular sieve adsorption column was embedded with a carbon quantum dot coating;

[0039] (2) contacting the first purified solution from step (1) with 4A molecular sieve for 25 minutes to obtain a second purified solution;

[0040] (3) contacting the second purified solution from step (2) with a 120-mesh neutral alumina adsorption column for 30 minutes to obtain a third purified solution;

[0041] (4) The third purified solution in step (3) is sequentially adsorbed on an acidic ion exchange resin and a basic ion exchange resin for 10 minutes each to obtain a fourth purified solution;

[0042] (5) The fourth purified liquid in step (4) is adsorbed on a NaA type polyamide molecular sieve membrane for 15 minutes to obtain purified acetonitrile.

[0043] Example 2

[0044] In this example, ethanol was purified by the following method

[0045] (1) contacting ethanol with a 3A molecular sieve adsorption column for 30 minutes to obtain a first purified solution, wherein the inner wall of the 3A molecular sieve adsorption column is embedded with a carbon quantum dot coating;

[0046] (2) contacting the first purified solution from step (1) with 4A molecular sieve for 30 minutes to obtain a second purified solution;

[0047] (3) contacting the second purified solution from step (2) with a 150-mesh neutral alumina adsorption column for 20 minutes to obtain a third purified solution;

[0048] (4) The third purified solution in step (3) is sequentially adsorbed on an acidic ion exchange resin and a basic ion exchange resin for 10 minutes each to obtain a fourth purified solution;

[0049] (5) The fourth purified liquid in step (4) is adsorbed on a NaA type polyamide molecular sieve membrane for 10 minutes to obtain purified ethanol.

[0050] Example 3

[0051] In this example, isopropanol was purified by the following method

[0052] (1) isopropyl alcohol was contacted with a 3A molecular sieve adsorption column for 40 minutes to obtain a first purified solution, and the inner wall of the 3A molecular sieve adsorption column was embedded with a carbon quantum dot coating;

[0053] (2) contacting the first purified solution from step (1) with 4A molecular sieve for 20 minutes to obtain a second purified solution;

[0054] (3) contacting the second purified solution from step (2) with a 150-mesh neutral alumina adsorption column for 30 minutes to obtain a third purified solution;

[0055] (4) The third purified solution in step (3) is sequentially adsorbed on an acidic ion exchange resin and a basic ion exchange resin for 10 minutes each to obtain a fourth purified solution;

[0056] (5) The fourth purified liquid in step (4) is adsorbed on a NaA type polyamide molecular sieve membrane for 20 minutes to obtain purified isopropyl alcohol.

[0057] Comparative Example 1

[0058] The difference between this comparative example and Example 1 is that this comparative example does not include step (2) to obtain purified acetonitrile.

[0059] Comparative Example 2

[0060] The difference between this comparative example and Example 1 is that this comparative example does not include step (3) to obtain purified acetonitrile.

[0061] Comparative Example 3

[0062] The difference between this comparative example and Example 1 is that this comparative example does not include step (2) and step (3), and purified acetonitrile is obtained.

[0063] Comparative Example 4

[0064] The difference between this comparative example and Example 1 is that after step (1) of this comparative example, adsorption is first performed on an acidic ion exchange resin and a basic ion exchange resin, and then adsorption is performed on a 4A molecular sieve and neutral alumina to obtain purified acetonitrile.

[0065] Comparative Example 5

[0066] The difference between this comparative example and Example 1 is that after step (1) of this comparative example, adsorption is first performed on an acidic ion exchange resin and a basic ion exchange resin, and then adsorption is performed on a 4A molecular sieve and neutral alumina to obtain purified acetonitrile.

[0067] Comparative Example 6

[0068] The difference between this comparative example and Example 1 is that the 3A molecular sieve in step (1) is replaced by silica gel.

[0069] Comparative Example 7

[0070] The difference between this comparative example and Example 1 is that the 4A molecular sieve in step (2) is replaced by 5A molecular sieve.

[0071] Comparative Example 8

[0072] The difference between this comparative example and Example 1 is that the modified polyamide membrane adsorption in step (5) is replaced by coconut shell activated carbon.

[0073] The solvent after the above adsorption was subjected to water content determination, fluorescence absorbance and transmittance test. The specific test results are shown in Table 1 below:

[0074] Moisture content was determined using a coulometric Karl Fischer titration method using a Mettler-Toledo C20 instrument. Fluorescence absorbance and transmittance were measured using a UV spectrophotometer using a PerkinElmer UV / US Lambda 365 instrument.

[0075] Table 1

[0076]

[0077]

[0078] From the data in the table we can see that:

[0079] NaA-type polyamide molecular sieve membranes have excellent water absorption and impurity adsorption properties due to their unique pore structure. Using 3A and 4A molecular sieves pretreated at the front end can achieve the best adsorption effect. However, the adsorption and removal of impurities is far inferior to the water absorption effect. Therefore, the addition of ion exchange resins and neutral alumina adsorption columns can not only remove small molecules or visible light impurities, but also remove trace amounts of water and metal ions.

[0080] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A method for purifying an organic solvent, characterized in that: The purification method comprises the following steps: (1) contacting an organic solvent with a 3A molecular sieve adsorption column to obtain a first purified solution, wherein the inner wall of the 3A molecular sieve adsorption column is embedded with a carbon quantum dot coating; (2) contacting the first purified solution from step (1) with 4A molecular sieve to obtain a second purified solution; (3) contacting the second purified solution from step (2) with a neutral alumina adsorption column to obtain a third purified solution; (4) adsorbing the third purified solution in step (3) through an ion exchange resin to obtain a fourth purified solution; (5) The fourth purified liquid in step (4) is adsorbed on a NaA type polyamide molecular sieve membrane to obtain a purified organic solvent.

2. The purification method according to claim 1, wherein The organic solvent in step (1) is any one of methanol, ethanol, isopropanol or acetonitrile.

3. The purification method according to claim 1 or 2, characterized in that The contact time in step (1) is 30 to 40 minutes.

4. The purification method according to any one of claims 1 to 3, characterized in that The contact time in step (2) is 20 to 30 minutes.

5. The purification method according to any one of claims 1 to 4, characterized in that The mesh size of the neutral alumina in any one of the steps (3) is 100 to 150 meshes.

6. The purification method according to any one of claims 1 to 5, characterized in that The contact time in step (3) is 20 to 30 minutes.

7. The purification method according to any one of claims 1 to 6, characterized in that The ion exchange resin in step (4) includes acidic ion exchange resin and / or basic ion exchange resin.

8. The purification method according to any one of claims 1 to 7, characterized in that The adsorption time in step (4) is 10 to 20 minutes.

9. The purification method according to any one of claims 1 to 8, characterized in that The adsorption time in step (5) is 10 to 20 minutes.

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