Method for purifying acetonitrile

Abstract

The invention discloses a method for purifying acetonitrile, and belongs to the technical field of organic solvent purification. The acetonitrile purification method comprises the following steps: dehydrating an acetonitrile solution through a membrane dehydration device, enabling the dehydrated acetonitrile to pass through an adsorption column filled with a magnetic iron oxide / graphene composite adsorbent, and collecting effluent; and carrying out normal pressure rectification on the effluent, controlling the reflux ratio to be 10: 1-8, the heating temperature of the rectification kettle to be 110-150 DEG C, the temperature of the acetonitrile liquid in the kettle to be 80-90 DEG C and the temperature of the distilled liquid to be 75-85 DEG C, and collecting to obtain purified acetonitrile. The method effectively solves the problems that a traditional potassium permanganate oxidant is adopted for purification at present, impurities generated by reaction are insoluble in water and difficult to remove, the environment is polluted to a certain extent, the impurities need to be filtered and removed, the operation is tedious and the like, is green and safe, and does not generate waste residues; and the final acetonitrile yield is greater than 90%, and the purity reaches 99.99%.

Description

Technical Field

[0001] The present invention relates to a method for purifying acetonitrile, belonging to the technical field of organic solvent purification. Background Art

[0002] Acetonitrile, also known as methyl cyanide, is a colorless transparent liquid with a molecular weight of 41.052, a melting point of -45°C, a boiling point of 81 - 82°C at 760 mmHg, a density of 0.786 g / cm 3 , a flash point of 12.8°C (CC), and is the simplest saturated aliphatic nitrile. Due to its unique functional group nitrile group, it has excellent solvent properties, can dissolve a variety of organic, inorganic, and gaseous substances, has a better distribution ratio and desorption capacity, is somewhat toxic, and is infinitely miscible with water and alcohol. The carbon-nitrogen triple bond in acetonitrile is prone to typical nitrile reactions, so acetonitrile can not only be used as a solvent but also be used to produce many nitrogen-containing compounds and is an important organic intermediate.

[0003] Currently, the commonly used methods for producing acetonitrile are roughly divided into two categories: direct synthesis methods and indirect methods. The direct synthesis methods include more than a dozen synthesis methods such as carbon monoxide ammoniation hydrogenation method and ethanol ammoniation method. The indirect method is mainly the by-product method of propylene ammoxidation. And the commonly used methods for purifying acetonitrile include adsorption - rectification purification method, alkali washing - adsorption - rectification purification method, extraction - rectification purification method, etc.

[0004] For example, a method for purifying acetonitrile disclosed in Chinese Patent CN11003053A is to extract the crude acetonitrile three times with dichloromethane and then purify the acetonitrile by rectification. However, in this process, dichloromethane is used as the extractant, resulting in a large amount of solvent usage and cumbersome operation.

[0005] For example, a method for purifying high-purity anhydrous acetonitrile disclosed in Chinese Patent CN110683967A first adsorbs impurities with activated carbon fiber, then decomposes impurities by ultraviolet photocatalytic oxidation technology, then removes acid impurities with a NaOH intermittent adsorption column, removes metal ion impurities and moisture with molecular sieve, and finally obtains the finished acetonitrile through distillation, vacuum rectification, and pressure rectification. However, the process of impurity decomposition in the early stage of this process is complex, and the product yield after purification is not mentioned.

[0006] For example, a method for purifying chromatographic grade acetonitrile disclosed in Chinese Patent CN112174852A is to successively carry out oxidation and neutralization reaction, impurity removal treatment with an adsorption column, and rectification treatment on industrial acetonitrile, and finally obtain chromatographic grade acetonitrile. This process has low processing capacity and is not suitable for large-scale industrial production.

[0007] As disclosed in Chinese Patent CN1328994A, a purification method of high-purity acetonitrile is provided, which adopts a combined process flow, including dehydrogenation of hydrocyanic acid tower, chemical treatment, vacuum, and pressure azeotropic distillation. The liquid phase is extracted from the upper side line of the rectifying section of the dehydrogenation of hydrocyanic acid tower. However, the designed process in this technology is relatively long and the control parameters are complex, which is not suitable for large-scale industrial production.

[0008] Chinese Patent CN101597241A discloses a method for purifying ultra-clean high-purity acetonitrile. The method is as follows: First, a polymer monomer is added to industrial acetonitrile, and an initiator is added. Heating is carried out to combine impurities into polymers. Then, distillation separation is adopted to obtain semi-finished acetonitrile with high light transmittance. After that, electrochemical treatment is carried out to obtain high-purity acetonitrile. The product obtained by this method has high purity, but the steps are relatively cumbersome and time-consuming. The loss rate is high, the yield is low, the efficiency is low, and the time cost is high during the purification process of industrial acetonitrile in the early stage. It is not suitable for large-scale industrial production, and the value of industrial production is not great.

[0009] Since the common pollutants in industrial acetonitrile are water, acetamide, acetic acid, and ammonia water, currently, the oxidation method (potassium permanganate-based oxidant) is used for the removal of impurities in acetonitrile. It can only remove unsaturated hydrocarbon compounds such as acrylonitrile. The reflux ratio of subsequent rectification separation is slightly reduced, and the energy consumption reduction is not obvious. At the same time, new impurities are generated during the oxidation reaction, and there are also impurities that are insoluble in water, which need to be removed by filtration. The filtration operation is relatively cumbersome, and there is also a risk of unclear filtration. The generated solid waste residue is also difficult to handle. Summary of the Invention

[0010] In view of the defects and deficiencies in the prior art, the present invention provides a purification method of acetonitrile, which effectively solves the problem that the impurities generated by the reaction are insoluble in water and difficult to remove, and need to be removed by filtration, and the operation is cumbersome. It overcomes the problems of complex and cumbersome industrial acetonitrile purification process and long time consumption; achieves the effect of reducing the energy consumption of subsequent rectification. The final yield of acetonitrile reaches more than 90%, and the purity reaches 99.99%.

[0011] The object of the present invention is to provide a purification method of acetonitrile, and the method includes the following steps:

[0012] (1) The acetonitrile solution obtained in production is dehydrated through a membrane dehydration device. The dehydrated acetonitrile passes through an adsorption column filled with a magnetic iron oxide / graphene composite adsorbent. The pressure of the adsorption tank is controlled at 0.01 - 0.5 MPa, and the flow rate is controlled at 50 - 100 L / h. The effluent is collected.

[0013] (2) The effluent obtained in step (1) is subjected to atmospheric rectification. The reflux ratio is controlled at 10:1 - 8, the heating temperature of the rectification kettle is 110 - 150 °C, the temperature of the acetonitrile liquid in the kettle is 80 - 90 °C, and the temperature of the distillate is 75 - 85 °C. The purified acetonitrile is collected.

[0014] In one embodiment, the dosage of the magnetic iron oxide / graphene oxide composite adsorbent in step (1) is 0.01-0.15% of the acetonitrile solution.

[0015] In one embodiment, the specific source of the acetonitrile solution produced in step (1) is as follows: acetic acid and liquid ammonia are introduced into the vaporization chamber for preheating and vaporization, then enter the mixer for mixing, and then enter the fixed-bed reactor equipped with a catalyst for catalytic reaction. The reaction gas is condensed and absorbed by water to obtain a crude acetonitrile solution.

[0016] In one embodiment, the preparation of the magnetic iron oxide / graphene oxide composite adsorbent in step (1) includes: graphene oxide is ultrasonically dispersed in a mixed solution of deionized water and propylene glycol, then silicate and iron hydroxide are dissolved in the mixed solution, and the reaction is carried out at 150-250 °C for 10-15 h in a sealed environment. The reactants are washed clean to obtain the magnetic iron oxide / graphene oxide composite adsorbent.

[0017] In one embodiment, the volume ratio of deionized water to propylene glycol in the mixed solution of deionized water and propylene glycol is 8-14:1.

[0018] In one embodiment, the ultrasonic dispersion temperature is 40-60 °C and the time is 2-4 h.

[0019] In one embodiment, the silicate is one or more of quartz, anorthite and talc.

[0020] In one embodiment, the graphene oxide:silicate:iron hydroxide = 15-35:1:1.

[0021] In one embodiment, the size of the graphene oxide microflakes is 0.5-3 μm and the thickness is 0.55-1.2 nm.

[0022] Another object of the present invention is to provide an application of the above-mentioned method in the quality inspection of acetonitrile production.

[0023] The beneficial effects of the present invention:

[0024] (1) The magnetic iron oxide / graphene oxide composite adsorbent prepared by the present invention has a more efficient and simple adsorption efficiency, achieving the effect of reducing the energy consumption of subsequent rectification. Finally, the acetonitrile yield is greater than 95% and the purity reaches 99.99%;

[0025] (2) The acetonitrile purification method of the present invention effectively solves the problems that the traditional potassium permanganate-based oxidants used in current purification and the impurities generated by the reaction are insoluble in water and difficult to remove, causing certain pollution to the environment and requiring filtration and removal, with cumbersome operations. Moreover, it is green and safe without the generation of waste residues. Brief Description of the Drawings

[0026] Figure 1 This is a schematic flow chart of the acetonitrile purification of the present invention. Detailed Embodiments

[0027] The following are descriptions of the preferred embodiments of the present invention. It should be understood that the embodiments are for better explaining the present invention and are not used to limit the present invention.

[0028] The specific preparation process and purity of the crude acetonitrile solution obtained from the production reaction involved in the present invention: Acetic acid and liquid ammonia are introduced into the vaporization chamber for preheating and vaporization, then enter the mixer for mixing, and then enter the fixed-bed reactor equipped with a catalyst for catalytic reaction. The reaction gas is condensed and absorbed by water to obtain a crude acetonitrile solution. The acetonitrile solution is evaporated to remove water, and then dehydrated by a membrane to obtain a 99% acetonitrile semi-finished product.

[0029] The parameters of graphene oxide and the information of the purchasing manufacturer involved in the embodiments of the present invention:

[0030] Graphene oxide appears as a brownish-black powder, tapped density: 0.7 - 1.2 g / cm 3 , powder diameter D50: 15 - 30 μm, microflake size 0.5 - 3 μm, thickness 0.55 - 1.2 nm; purchased from Changzhou Sixth Element Materials Technology Co., Ltd.

[0031] Modified activated carbon, in black powder form, iodine adsorption ≥ 900 mg / g, iron content ≤ 0.05%, moisture content ≤ 10%, specification 200 mesh; purchased from Zhengzhou Kelin Water Purification Materials Co., Ltd. Modification method: The surface functional groups of activated carbon are reduced and modified by a reducing agent to increase the oxygen-containing basic groups on the surface of activated carbon and enhance surface non-polarity. The specific operation is: Immerse in ammonia water under an N 2 inert gas to obtain activated carbon with a relatively high content of basic groups.

[0032] Example 1

[0033] A method for purifying acetonitrile, comprising the following steps:

[0034] (1) Put 100 g of graphene oxide in 500 ml of a mixed solution of deionized water and propylene glycol (the volume ratio of deionized water to propylene glycol is 10:1), ultrasonicate at 50 °C for 3 h, then dissolve 5 g of silicate (anorthite) and 5 g of iron hydroxide in the mixed solution, and carry out a reaction at 200 °C for 12 h in a sealed environment. After the reaction; wash the reactants clean to obtain a magnetic iron oxide / graphene oxide composite adsorbent; wherein the mass ratio of graphene oxide: silicate: iron hydroxide = 20:1:1;

[0035] (2) First, pass the acetonitrile solution obtained from the 20 kg production reaction through a membrane dehydration device to remove the water in the acetonitrile. After dehydration, the acetonitrile is passed into an adsorption column filled with 20 g of the magnetic iron oxide / graphene oxide composite adsorbent prepared in step (1) for adsorption. Control the pressure in the adsorption tank to be 0.3 MPa and the flow rate to be 80 L / h for impurity removal. Then, rectify the acetonitrile obtained after the adsorption treatment. The heating temperature of the rectification still is 130 °C, the temperature of the acetonitrile liquid in the still is 85 °C, the temperature of the distillate is 80 °C, and the reflux ratio is controlled at 10:2. Finally, collect the purified acetonitrile at a flow rate of 20 mL / min.

[0036] The purified acetonitrile obtained in this example is 1759 g, with a yield of 93.4% and a purity of 99.99%.

[0037] Example 2

[0038] A method for purifying acetonitrile, comprising the following steps:

[0039] (1) Place 100 g of graphene oxide in a mixed solution of deionized water and propylene glycol (the volume ratio of deionized water to propylene glycol is 10:1), ultrasonicate for 1 h at 50 °C, then dissolve 4 g of silicate (anorthite) and 4 g of iron hydroxide in the mixed solution, and react at 200 °C for 12 h in a sealed environment. After the reaction, wash the reactants clean to obtain the magnetic iron oxide / graphene oxide composite adsorbent; wherein, the mass ratio of graphene oxide:silicate:iron hydroxide = 25:1:1;

[0040] (2) First, pass the acetonitrile solution obtained from the 20 kg production reaction through a membrane dehydration device to remove the water in the acetonitrile. After dehydration, the acetonitrile is passed into an adsorption column filled with 20 g of the magnetic iron oxide / graphene oxide composite adsorbent prepared in step (1) for adsorption. Control the pressure in the adsorption tank to be 0.3 MPa and the flow rate to be 80 L / h for impurity removal. Then, rectify the acetonitrile obtained after the adsorption treatment. The heating temperature of the rectification still is 130 °C, the temperature of the acetonitrile liquid in the still is 85 °C, the temperature of the distillate is 80 °C, and the reflux ratio is controlled at 10:4. Finally, collect the purified acetonitrile at a flow rate of 20 mL / min.

[0041] The purified acetonitrile obtained in this example is 1907 g, with a yield of 94.4% and a purity of 99.99%.

[0042] Example 3

[0043] A method for purifying acetonitrile, comprising the following steps:

[0044] (1) Place 120 g of graphene oxide in a mixed solution of deionized water and propylene glycol (the volume ratio of deionized water to propylene glycol is 10:1), ultrasonicate at 50 °C for 3 h, then dissolve 4 g of silicate, 4 g of anorthite and 4 g of iron hydroxide in the mixed solution, and carry out the reaction in a sealed environment at 200 °C for 12 h. After the reaction, wash the reactants clean to obtain a magnetic iron oxide / graphene oxide composite adsorbent; wherein, the mass ratio of graphene oxide:silicate:iron hydroxide = 30:1:1;

[0045] (2) First pass the 20 kg of acetonitrile solution obtained from the production reaction through a membrane dehydration device to remove the water in the acetonitrile. After dehydration, the acetonitrile is passed into an adsorption column equipped with 20 g of the magnetic iron oxide / graphene oxide composite adsorbent prepared in step (1) for adsorption. Control the pressure in the adsorption tank at 0.3 MPa and the flow rate at 80 L / h for impurity removal. Rectify the acetonitrile obtained after the adsorption treatment. The heating temperature of the rectification still is 130 °C, the temperature of the acetonitrile liquid in the still is 85 °C, the temperature of the distillate is 80 °C, control the reflux ratio at 10:6, and finally collect the purified acetonitrile at a flow rate of 20 mL / min.

[0046] The purified acetonitrile obtained in this example is 1808 g, the yield is 96.8%, and the purity is 99.99%.

[0047] Example 4

[0048] A method for purifying acetonitrile, comprising the following steps:

[0049] (1) Place 100 g of graphene oxide in a mixed solution of deionized water and propylene glycol (the volume ratio of deionized water to propylene glycol is 10:1), ultrasonicate at 50 °C for 3 h, then dissolve 4 g of silicate (anorthite) and 4 g of iron hydroxide in the mixed solution, and carry out the reaction in a sealed environment at 250 °C for 12 h. After the reaction, wash the reactants clean to obtain a magnetic iron oxide / graphene oxide composite adsorbent; wherein, the mass ratio of graphene oxide:silicate:iron hydroxide = 25:1:1;

[0050] (2) First pass the 20 kg of acetonitrile solution obtained from the production reaction through a membrane dehydration device to remove the water in the acetonitrile. After dehydration, the acetonitrile is passed into an adsorption column equipped with 20 g of the magnetic iron oxide / graphene oxide composite adsorbent prepared in step (1) for adsorption. Control the pressure in the adsorption tank at 0.3 MPa and the flow rate at 80 L / h for impurity removal. Rectify the acetonitrile obtained after the adsorption treatment. The heating temperature of the rectification still is 130 °C, the temperature of the acetonitrile liquid in the still is 85 °C, the temperature of the distillate is 80 °C, control the reflux ratio at 10:8, and finally collect the purified acetonitrile at a flow rate of 20 mL / min.

[0051] The purified acetonitrile obtained in this example is 1658 g, the yield is 92.4%, and the purity is 99.99%.

[0052] Comparative Example 1

[0053] The acetonitrile solution obtained from the 20 kg production reaction is first passed through a membrane dehydration device to remove the water in the acetonitrile. After dehydration, the acetonitrile is introduced into a 20 g modified activated carbon adsorption column for adsorption. The pressure of the adsorption tank is controlled at 0.3 MPa, and the flow rate is controlled at 80 L / h for impurity removal. The acetonitrile obtained after the adsorption treatment is rectified. The heating temperature of the rectification kettle is 130 °C, the temperature of the acetonitrile liquid in the kettle is 85 °C, the temperature of the distillate is 80 °C, and the reflux ratio is controlled at 10:8. Finally, the purified acetonitrile is collected at a flow rate of 20 mL / min.

[0054] The purified acetonitrile obtained in this comparative example is 1828 g, the yield is 91.4%, and the purity is 99.84%.

[0055] Comparative Example 2

[0056] (1) 100 g of graphene oxide is placed in a mixed solution of deionized water and propylene glycol (the volume ratio of deionized water to propylene glycol is 10:1), and ultrasonicated at 50 °C for 3 h. Then, 4 g of silicate (anorthite) and 4 g of alumina are dissolved in the mixed solution, and the reaction is carried out at 200 °C for 12 h in a sealed environment. After the reaction, the reactants are washed clean to obtain a magnetic alumina / graphene oxide composite adsorbent; wherein, the mass ratio of graphene oxide:silicate:alumina = 25:1:1;

[0057] (2) The acetonitrile solution obtained from the 20 kg production reaction is first passed through a membrane dehydration device to remove the water in the acetonitrile. After dehydration, the acetonitrile is introduced into an adsorption column equipped with 20 g of the magnetic alumina / graphene oxide composite adsorbent prepared in step (1) for adsorption. The pressure of the adsorption tank is controlled at 0.3 MPa, and the flow rate is controlled at 80 L / h for impurity removal. The acetonitrile obtained after the adsorption treatment is rectified. The heating temperature of the rectification kettle is 130 °C, the temperature of the acetonitrile liquid in the kettle is 85 °C, the temperature of the distillate is 80 °C, and the reflux ratio is controlled at 10:8. Finally, the purified acetonitrile is collected at a flow rate of 20 mL / min.

[0058] The purified acetonitrile obtained in this comparative example is 1854 g, the yield is 92.7%, and the purity is 99.88%.

[0059] Comparative Example 3

[0060] (1) Put 100 g of graphene oxide in a mixed solution of deionized water and propylene glycol (the volume ratio of deionized water to propylene glycol is 10:1), ultrasonicate at 50 °C for 3 h, then dissolve 4 g of silicate (anorthite) and 4 g of iron hydroxide in the mixed solution, and carry out the reaction in a sealed environment at 150 °C for 5 h. After the reaction, wash the reactants clean to obtain a magnetic iron oxide / graphene oxide composite adsorbent; wherein, the mass ratio of graphene oxide: silicate: iron hydroxide = 25:1:1;

[0061] (2) First pass the 20 kg of acetonitrile solution obtained from the production reaction through a membrane dehydration device to remove the water in the acetonitrile. After dehydration, the acetonitrile is introduced into an adsorption column equipped with 20 g of the magnetic iron oxide / graphene oxide composite adsorbent prepared in step (1) for adsorption. Control the pressure in the adsorption tank at 0.3 MPa and the flow rate at 80 L / h for impurity removal. Rectify the acetonitrile obtained after the adsorption treatment. The heating temperature of the rectification kettle is 130 °C, the temperature of the acetonitrile liquid in the kettle is 85 °C, the temperature of the distillate is 80 °C, and the reflux ratio is controlled at 10:8. Finally, collect the purified acetonitrile at a flow rate of 20 mL / min.

[0062] The purified acetonitrile obtained in this comparative example is 1828 g, the yield is 91.4%, and the purity is 99.82%.

[0063] The embodiments provided above are not intended to limit the scope covered by the present invention, nor are the described steps intended to limit their execution order. Obvious improvements made by those skilled in the art in combination with the existing common general knowledge also fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for purifying acetonitrile, characterized in that, the method comprises the following steps: (1) Dehydrate the produced acetonitrile solution through a membrane dehydration device, and pass the dehydrated acetonitrile through an adsorption column filled with a magnetic iron oxide / graphene composite adsorbent. Control the pressure of the adsorption tank at 0.01 - 0.5 MPa and the flow rate at 50 - 100 L / h, and collect the effluent; (2) Carry out atmospheric distillation on the effluent obtained in step (1). Control the reflux ratio at 10:1 - 8, the heating temperature of the distillation kettle at 110 - 150 °C, the temperature of the acetonitrile liquid in the kettle at 80 - 90 °C, and the temperature of the distillate at 75 - 85 °C, and collect the purified acetonitrile.

2. The method according to claim 1, characterized in that, the dosage of the magnetic iron oxide / graphene oxide composite adsorbent in step (1) is 0.01 - 0.15% of the acetonitrile solution.

3. The method according to claim 1, characterized in that, the specific source of the acetonitrile solution produced in step (1) is: Pass acetic acid and liquid ammonia into the vaporization chamber for preheating and vaporization, then enter the mixer for mixing, and then enter the fixed bed reactor equipped with a catalyst for catalytic reaction. The reaction gas is condensed and absorbed by water to obtain crude acetonitrile.

4. The method according to claim 1, characterized in that, the preparation of the magnetic iron oxide / graphene oxide composite adsorbent in step (1) includes: Ultrasonically disperse graphene oxide in a mixed solution of deionized water and propylene glycol, then dissolve silicate and iron hydroxide in the mixed solution, and keep it at 150 - 250 °C for 10 - 15 h in a sealed environment for reaction. Wash the reactants clean to obtain the magnetic iron oxide / graphene oxide composite adsorbent.

5. The method according to claim 4, characterized in that, the volume ratio of deionized water to propylene glycol in the mixed solution of deionized water and propylene glycol is 8 - 14:

1.

6. The method according to claim 4, characterized in that, the ultrasonic dispersion temperature is 40 - 60 °C and the time is 2 - 4 h.

7. The method according to claim 4, characterized in that, the silicate is one or more of quartz, anorthite, and talc.

8. The method according to claim 4, characterized in that, the graphene oxide:silicate:iron hydroxide = 15 - 35:1:

1.

9. The method according to claim 4, characterized in that, the size of the graphene oxide microplates is 0.5 - 3 μm and the thickness is 0.55 - 1.2 nm.

10. The application of the method according to any one of claims 1 - 9 in the quality inspection of acetonitrile production.

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