A kind of preparation method of chromatography grade acetonitrile

Abstract

The present invention provides a method for preparing chromatographic-grade acetonitrile, belonging to the field of chromatographic-grade acetonitrile. The method for preparing chromatographic-grade acetonitrile comprises the following steps: pretreatment, low-temperature plasma oxidation and impurity removal, adsorption and impurity removal, and distillation and refining. The method for preparing chromatographic-grade acetonitrile of the present invention eliminates the need for the addition of strong oxidants and alkaline neutralizers, effectively avoiding secondary contamination caused by the introduction of additional chemical reagents. It can efficiently remove impurities from industrial-grade acetonitrile under mild conditions while ensuring refining efficiency.

Description

Technical Field

[0001] The present invention relates to the field of chromatographic grade acetonitrile, in particular to a method for preparing chromatographic grade acetonitrile. Background Art

[0002] Acetonitrile (CH3CN), also known as methyl cyanide, is the simplest saturated aliphatic nitrile compound. It is a colorless, transparent liquid at room temperature and pressure with a distinctive ether-like odor. Acetonitrile exhibits excellent solvent properties, dissolving a wide range of inorganic, organic, and gaseous compounds. Furthermore, it is a relatively stable nitrile compound and is not susceptible to oxidation or reduction reactions. In the pharmaceutical industry, acetonitrile is used as an intermediate in the synthesis of vitamin B1, the antihypertensive drugs moxonidine and cortisone, sulfonamides, and other drugs. In the petrochemical industry, acetonitrile is used as an extractant for butadiene and isoprene, and as a raw material for the synthesis of fine chemicals such as dyes, surfactants, pesticides, fragrances, and organic synthesis. In instrumental analysis, acetonitrile is used as a mobile phase solvent in thin-layer chromatography, paper chromatography, spectroscopy, polarography, and high-performance liquid chromatography (HPLC). It is also used as a solvent for DNA synthesis and purification, in the synthesis of organic materials, and in cleaning electronic components. With the continuous development of technology in high-end application fields, the purity requirements for acetonitrile are also increasing, and chromatographic grade acetonitrile is often required to meet its application requirements.

[0003] Chromatographic-grade acetonitrile refers to acetonitrile with a purity of at least 99.9% and exhibiting minimal or no absorption in the near-UV region. Due to its minimal or no absorption in the near-UV region, it is used as an organic modifier and solvent in thin-layer chromatography, paper chromatography, gas chromatography, and especially high-performance liquid chromatography. Furthermore, as a highly polar, high-purity solvent, chromatographic-grade acetonitrile has excellent solubility for compounds such as oils and fats, making it suitable as a semiconductor cleaning agent to remove grease, fingerprints, and other substances from silicon wafers.

[0004] Existing chromatography-grade acetonitrile is made by using industrial-grade acetonitrile as raw material and refining and removing impurities. For industrial-grade acetonitrile prepared by acetic acid ammoniation method, its impurities generally include acetaldehyde, acetone, acrolein, acrylonitrile, methanol, isopropanol, etc. The existing chromatography-grade acetonitrile preparation method is mainly to combine the methods of oxidation and impurity removal by adding strong oxidants or photocatalysts, multi-stage distillation and impurity removal, and multi-stage adsorption and impurity removal. However, the method of using oxidant oxidation and impurity removal requires the use of strong oxidants such as potassium permanganate and concentrated sulfuric acid, and requires the use of alkaline neutralizers to adjust the pH, which will introduce additional chemical reagents, not only causing secondary pollution to acetonitrile, but also increasing the pressure of subsequent distillation and adsorption treatment, reducing the subsequent refining efficiency and effect; the method of using multi-stage distillation and impurity removal has the risk of thermal decomposition or polymerization for the high-temperature distillation environment of industrial-grade acetonitrile, and the impurity removal efficiency is low, and it is no longer possible to achieve efficient impurity removal of acetonitrile under mild conditions. Summary of the Invention

[0005] To solve the technical problems existing in the prior art, the present invention provides a method for preparing chromatographic-grade acetonitrile, which does not require the addition of strong oxidants and alkaline neutralizers, effectively avoids the secondary contamination problem caused by the introduction of additional chemical reagents, and can efficiently remove impurities from industrial-grade acetonitrile under mild conditions while ensuring the refining efficiency.

[0006] In order to solve the above technical problems, the technical solutions adopted by the present invention are as follows:

[0007] A method for preparing chromatographic-grade acetonitrile comprises the following steps: pretreatment, low-temperature plasma oxidation and impurity removal, adsorption and impurity removal, and distillation and purification.

[0008] In the pretreatment, industrial-grade acetonitrile flows through an adsorption column filled with 3A molecular sieve to obtain a pretreated liquid;

[0009] The low-temperature plasma oxidation and impurity removal comprises the following steps: uniformly mixing a pretreatment liquid and a supported catalyst, placing the mixture in a treatment chamber of a low-temperature plasma treatment device, using a mixture of argon and oxygen as a reaction gas under argon atmosphere protection, controlling the discharge voltage of the low-temperature plasma treatment to be 25-27 kV, the discharge frequency to be 55-60 Hz, and the discharge power to be 220-250 W, and continuously introducing the reaction gas below the liquid level of the pretreatment liquid for bubbling after activation by low-temperature plasma discharge at room temperature; and filtering after the bubbling is completed to obtain an oxidation and impurity removal liquid;

[0010] The supported catalyst is prepared by using carboxylated multi-walled carbon nanotubes as a support, which is immersed in a metal salt loading solution containing manganese and lanthanum, and then dried and calcined.

[0011] The adsorption impurity removal, oxidation impurity removal liquid flows through the adsorption column filled with mesoporous activated carbon and 5A molecular sieve in sequence to obtain the adsorption impurity removal liquid;

[0012] The adsorption and impurity removal liquid is refined by distillation to obtain chromatographic grade acetonitrile.

[0013] Preferably, in the pretreatment, the flow rate of industrial-grade acetonitrile is 200-220 mL / min, and the residence time of industrial-grade acetonitrile in the adsorption column is 17-26 min.

[0014] Preferably, in the low-temperature plasma oxidation and impurity removal, the volume ratio of argon and oxygen in the reaction gas is 100:7-8;

[0015] The total volume of the reaction gas introduced is 5-6 times the total volume of the pretreatment liquid;

[0016] The weight ratio of the loaded catalyst to the pretreatment liquid is 1.2-1.5:100.

[0017] Preferably, in the low-temperature plasma oxidation and impurity removal, the reaction gas is activated by low-temperature plasma discharge and then bubbled into the pretreatment liquid through a microporous aeration head or a gas distributor provided at the bottom of the treatment chamber;

[0018] The bubbling time was controlled to be 420-480s.

[0019] Furthermore, the preparation method of the supported catalyst is as follows: dissolving manganese nitrate and lanthanum nitrate in deionized water to prepare a metal salt supported liquid; immersing carboxylated multi-walled carbon nanotubes in the metal salt supported liquid, immersing at 40-45°C, and separating to obtain a solid; and calcining the dried solid at 320-330°C to obtain a supported catalyst.

[0020] Preferably, in the preparation of the supported catalyst, the metal salt concentration of the metal salt supported liquid is 0.2-0.3 mol / L;

[0021] The molar ratio of manganese nitrate to lanthanum nitrate is 2-2.3:0.4-0.5.

[0022] Preferably, in the preparation of the supported catalyst, the weight ratio of carboxylated multi-walled carbon nanotubes to the metal salt supported liquid is 1:8-10;

[0023] The calcination time at 320-330°C is 3-4h.

[0024] In the adsorption impurity removal, the flow rate of the oxidative impurity removal liquid is 100-110 mL / min;

[0025] The residence time of the oxidation and impurity removal liquid in each adsorption column is 35-55 minutes.

[0026] Preferably, in the adsorption and impurity removal, the average particle size of the mesoporous activated carbon is 80-100 μm, and the specific surface area is 1200-1300 m 2 / g, and the average pore size is 3-8nm.

[0027] Preferably, the distillation and purification is carried out by introducing the adsorption and impurity removal liquid into a distillation tower, controlling the bottom temperature of the distillation tower to 85-87°C, the top temperature to 80-83°C, and the reflux ratio to 5-6:1, and performing distillation and purification to obtain chromatographic grade acetonitrile.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] (1) The method for preparing chromatographic-grade acetonitrile of the present invention first uses a pretreatment step to remove most of the water in industrial-grade acetonitrile using an adsorption column filled with 3A molecular sieve to obtain a pretreatment liquid. This is to avoid the problem of excessive water content in acetonitrile interfering with plasma treatment during the subsequent low-temperature plasma oxidation and impurity removal process, thereby improving the treatment efficiency and treatment performance of the subsequent low-temperature plasma oxidation and impurity removal. Then, in the low-temperature plasma oxidation and impurity removal step, by using a reaction gas with a specific composition and ratio, under specific plasma treatment process parameters (discharge voltage, discharge frequency, discharge power), the reaction gas is discharged and activated and then bubbled into the pretreatment liquid. At the same time, the impurity components in the pretreatment liquid are selectively catalyzed by the loaded catalyst to perform controllable high-selective oxidation and degradation. Furthermore, by precisely controlling the aforementioned reaction gas ratio, plasma treatment process parameters, and bubbling time, excessive oxidation of acetonitrile is avoided, the acetonitrile component in the pretreatment liquid is retained, and an oxidation and impurity removal liquid is obtained. Then, in the adsorption and impurity removal step, the oxidized impurity removal liquid is sequentially subjected to adsorption and impurity removal by an adsorption column filled with mesoporous activated carbon and 5A molecular sieve, and the impurity components remaining in the oxidized impurity removal liquid are adsorbed to obtain an adsorption and impurity removal liquid. Finally, the adsorption and impurity removal liquid is refined by rectification to obtain chromatographic grade acetonitrile. The aforementioned technical means cooperate and act synergistically with each other, without the need to add additional strong oxidants and alkaline neutralizers, effectively avoiding the secondary pollution problem caused by the introduction of additional chemical reagents, and can efficiently remove impurities from industrial-grade acetonitrile under mild conditions while ensuring the refining efficiency, providing a new process route for the preparation of chromatographic grade acetonitrile.

[0030] (2) According to the test, the purity of the chromatographic grade acetonitrile prepared by the preparation method of the chromatographic grade acetonitrile of the present invention exceeds 99.98wt%, the moisture content is 0.0027-0.0031wt%, the acidity is 0.0002-0.0003mmol / g, the alkalinity is undetectable, the evaporation residue is 0.8-0.9ppm, and the yield is 99.1-99.4%; the absorbance of the chromatographic grade acetonitrile prepared at 200nm is 0.012-0.015, the absorbance at 210nm is 0.004-0.005, the absorbance at 220nm is 0.001-0.003, the absorbance at 230nm is 0.001, the absorbance at 240nm is 0, and the absorbance at 250nm is 0.

[0031] (3) The results of the test showed that the quality of the chromatographic grade acetonitrile prepared by the preparation method of the chromatographic grade acetonitrile of the present invention was stable; the fluctuations of its yield, moisture content, acidity, evaporation residue, absorbance at 200 nm, and absorbance at 210 nm were all within the allowable threshold range, and the batch consistency was good. DETAILED DESCRIPTION

[0032] In order to provide a clearer understanding of the technical features, objectives, and effects of the present invention, specific embodiments of the present invention are now described. It should be noted that the following detailed description is illustrative and is intended to further illustrate the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0033] It should be noted that the terms used herein are intended only to describe specific embodiments and are not intended to limit the exemplary embodiments of the present invention. As used herein, "first," "second," and the like are used to distinguish similar objects and are not used to describe a specific order or precedence. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0034] The embodiment of the present invention provides a method for preparing chromatographic-grade acetonitrile, which comprises the following steps: pretreatment, low-temperature plasma oxidation and impurity removal, adsorption and impurity removal, and distillation and purification.

[0035] The pretreatment method is as follows: under room temperature, industrial-grade acetonitrile is passed through an adsorption column filled with 3A molecular sieve at a flow rate of 200-220 mL / min, and the residence time of the industrial-grade acetonitrile in the adsorption column is controlled to be 17-26 minutes to obtain a pretreated liquid.

[0036] In the pretreatment, the height of the adsorption column filled with 3A molecular sieve is 1-1.1 m, and the inner diameter is 7-8 cm; the filling height of the 3A molecular sieve is 80-85% of the height of the adsorption column.

[0037] The low-temperature plasma oxidation impurity removal method comprises the following steps: adding a supported catalyst to a pretreatment liquid, ultrasonically dispersing the pretreatment liquid for 10-20 minutes, and then placing the pretreatment liquid in a treatment chamber of a low-temperature plasma treatment device; completely replacing the air in the treatment chamber with argon; using a mixture of argon and oxygen (volume ratio of 100:7-8) as the reaction gas; controlling the discharge voltage of the low-temperature plasma treatment to be 25-27 kV, the discharge frequency to be 55-60 Hz, and the discharge power to be 220-250 W; continuously passing the reaction gas between two discharge plates of the low-temperature plasma treatment device under room temperature for discharge activation, and then continuously introducing the reaction gas below the liquid surface of the pretreatment liquid for uniform bubbling, so that the impurity components in the pretreatment liquid are controllably oxidized and degraded, and oxidative degradation of acetonitrile is avoided; the bubbling time is controlled to be 420-480 seconds; after the bubbling is completed, the low-temperature plasma oxidation impurity removal is completed; and after filtering and recovering the solid matter, an oxidation impurity removal liquid is obtained; and simultaneously, during the low-temperature plasma oxidation impurity removal process, waste gas generated is collected and discharged to a waste gas treatment device for treatment.

[0038] In the low-temperature plasma oxidation and impurity removal, bubbles are preferably evenly distributed into the pretreatment liquid through a microporous aeration head or a gas distributor with an average pore size of 50-60 μm provided at the bottom of the treatment chamber to achieve sufficient gas-liquid contact.

[0039] In the low-temperature plasma oxidation and impurity removal, the total volume of the reaction gas introduced is 5-6 times the total volume of the pretreatment liquid.

[0040] In the low-temperature plasma oxidation and impurity removal, the weight ratio of the supported catalyst to the pretreatment liquid is 1.2-1.5:100.

[0041] The supported catalyst is prepared by using carboxylated multi-walled carbon nanotubes as carriers, immersing them in a loading liquid for loading, and then drying and calcining. Specifically, manganese nitrate and lanthanum nitrate are added to deionized water, stirred and dissolved to prepare a metal salt loading liquid with a concentration of 0.2-0.3 mol / L; the carboxylated multi-walled carbon nanotubes are added to the metal salt loading liquid, stirred at 40-45° C. for 3-4 hours, and then centrifuged to obtain a solid; the solid is dried at 110-120° C. for 10-12 hours, calcined at 320-330° C. for 3-4 hours, and ground evenly to prepare the supported catalyst.

[0042] In the preparation of the supported catalyst, the molar ratio of manganese nitrate to lanthanum nitrate is 2-2.3:0.4-0.5;

[0043] The weight ratio of the carboxylated multi-walled carbon nanotubes to the metal salt loading liquid is 1:8-10.

[0044] The adsorption impurity removal method is as follows: under room temperature conditions, the oxidizing impurity removal liquid is passed through adsorption columns filled with mesoporous activated carbon and 5A molecular sieve at a flow rate of 100-110 mL / min in sequence, and the residence time of the oxidizing impurity removal liquid in each adsorption column is controlled to be 35-55 minutes to obtain the adsorption impurity removal liquid.

[0045] In the adsorption and impurity removal, the height of the adsorption column filled with mesoporous activated carbon is 1-1.1m, and the inner diameter is 7-8cm; the filling height of the mesoporous activated carbon is 80-85% of the height of the adsorption column; the height of the adsorption column filled with 5A molecular sieve is 1-1.1m, and the inner diameter is 7-8cm; the filling height of the 5A molecular sieve is 80-85% of the height of the adsorption column.

[0046] The mesoporous activated carbon used in the adsorption and impurity removal has an average particle size of 80-100 μm and a specific surface area of ​​1200-1300 m 2 / g, and the average pore size is 3-8nm.

[0047] The distillation and purification method comprises the following steps: introducing the adsorption and impurity removal liquid into a distillation tower, controlling the bottom temperature of the distillation tower to be 85-87° C., the top temperature to be 80-83° C., and the reflux ratio to be 5-6:1, and performing distillation and purification to obtain chromatographic grade acetonitrile.

[0048] The present invention will be further described below with reference to some specific embodiments.

[0049] Example 1

[0050] This embodiment provides a method for preparing chromatographic grade acetonitrile, wherein the purity is 99.53 wt%, the water content is 0.18 wt%, the acidity (in terms of acetic acid) is 0.005 mmol / g, and the basicity (in terms of OH) is 0. - The evaporation residue was treated with 0.008 wt% of industrial grade acetonitrile, and the specific steps were as follows:

[0051] 1. Preprocessing

[0052] Under room temperature conditions, industrial-grade acetonitrile was passed through an adsorption column filled with 3A molecular sieve at a flow rate of 200 mL / min, and the residence time of the industrial-grade acetonitrile in the adsorption column was controlled to be 19.2 min to obtain a pretreated solution.

[0053] The adsorption column filled with 3A molecular sieve has a height of 1 m and an inner diameter of 7 cm; the filling height of the 3A molecular sieve is 80% of the height of the adsorption column.

[0054] 2. Low-temperature plasma oxidation and impurity removal

[0055] The loaded catalyst was added to the pretreatment liquid, ultrasonically dispersed for 10 minutes, and then placed in a treatment chamber of a low-temperature plasma treatment device. Argon was used to completely replace the air in the treatment chamber. A mixture of argon and oxygen (volume ratio of 100:7) was used as the reaction gas. The discharge voltage of the low-temperature plasma treatment was controlled to be 25 kV, the discharge frequency was 60 Hz, and the discharge power was 220 W. Under room temperature conditions, the reaction gas continuously passed between two discharge plates of the low-temperature plasma treatment device for discharge activation, and then continuously bubbled into the pretreatment liquid through a microporous aeration head with an average pore size of 50 μm provided at the bottom of the treatment chamber to achieve sufficient gas-liquid contact, so that the impurity components in the pretreatment liquid were controllably oxidized and degraded, and acetonitrile oxidative degradation was avoided. The bubbling time was controlled at 480 seconds. After the bubbling was completed, the low-temperature plasma oxidation and impurity removal was completed, and the solid matter (loaded catalyst) was filtered and recovered to obtain an oxidized and impurity-removed liquid. At the same time, during the low-temperature plasma oxidation and impurity removal process, the waste gas generated was collected and discharged to a waste gas treatment device for treatment.

[0056] During the low-temperature plasma oxidation and impurity removal process, the total volume of the reaction gas introduced is 5 times the total volume of the pretreatment liquid.

[0057] The weight ratio of the loaded catalyst to the pretreatment liquid was 1.2:100.

[0058] The preparation method of the loaded catalyst comprises the following steps: adding manganese nitrate and lanthanum nitrate into deionized water, stirring and dissolving, and preparing a metal salt loaded liquid with a concentration of 0.2 mol / L; adding carboxylated multi-walled carbon nanotubes into the metal salt loaded liquid, stirring at 40° C. for 3 hours, and centrifuging to obtain a solid; drying the solid at 110° C. for 10 hours, calcining at 320° C. for 3 hours, and grinding the solid to obtain a loaded catalyst loaded with copper oxide, cobalt oxide, and lanthanum oxide.

[0059] In the preparation of the supported catalyst, the molar ratio of manganese nitrate to lanthanum nitrate was 2:0.4.

[0060] The weight ratio of the carboxylated multi-walled carbon nanotubes to the metal salt loading liquid is 1:8.

[0061] 3. Adsorption and impurity removal

[0062] Under room temperature conditions, the oxidizing impurity removal liquid was passed through adsorption columns filled with mesoporous activated carbon and 5A molecular sieves in sequence at a flow rate of 100 mL / min, and the residence time of the oxidizing impurity removal liquid in each adsorption column was controlled to be 38.5 min to obtain the adsorption impurity removal liquid.

[0063] The height of the adsorption column filled with mesoporous activated carbon is 1 m and the inner diameter is 7 cm; the filling height of the mesoporous activated carbon is 80% of the height of the adsorption column.

[0064] The adsorption column filled with 5A molecular sieve has a height of 1 m and an inner diameter of 7 cm; the filling height of 5A molecular sieve is 80% of the height of the adsorption column.

[0065] The average particle size of mesoporous activated carbon is 100 μm and the specific surface area is 1300 m 2 / g, and the average pore diameter is 5nm.

[0066] 4. Distillation and refining

[0067] The adsorption and impurity removal liquid was introduced into a distillation tower, and the bottom temperature of the distillation tower was controlled at 85°C, the top temperature was controlled at 80°C, and the reflux ratio was 5:1. Distillation and purification were carried out to obtain chromatographic grade acetonitrile.

[0068] Example 2

[0069] This embodiment provides a method for preparing chromatographic grade acetonitrile, wherein the purity is 99.53 wt%, the water content is 0.18 wt%, the acidity (in terms of acetic acid) is 0.005 mmol / g, and the basicity (in terms of OH) is 0. - The evaporation residue was treated with 0.008 wt% of industrial grade acetonitrile, and the specific steps were as follows:

[0070] 1. Preprocessing

[0071] Under room temperature conditions, industrial-grade acetonitrile was passed through an adsorption column filled with 3A molecular sieve at a flow rate of 210 mL / min, and the residence time of the industrial-grade acetonitrile in the adsorption column was controlled to be 18.3 min to obtain a pretreated solution.

[0072] The adsorption column filled with 3A molecular sieve has a height of 1 m and an inner diameter of 7 cm; the filling height of the 3A molecular sieve is 80% of the height of the adsorption column.

[0073] 2. Low-temperature plasma oxidation and impurity removal

[0074] The loaded catalyst was added to the pretreatment liquid, ultrasonically dispersed for 15 minutes, and then placed in a treatment chamber of a low-temperature plasma treatment device. Argon was used to completely replace the air in the treatment chamber. A mixture of argon and oxygen (volume ratio of 100:7.5) was used as the reaction gas. The discharge voltage of the low-temperature plasma treatment was controlled to be 26 kV, the discharge frequency was 60 Hz, and the discharge power was 240 W. Under room temperature conditions, the reaction gas continuously passed between two discharge plates of the low-temperature plasma treatment device for discharge activation, and then continuously bubbled into the pretreatment liquid through a microporous aeration head with an average pore size of 50 μm provided at the bottom of the treatment chamber to achieve sufficient gas-liquid contact, so that the impurities in the pretreatment liquid were controllably oxidized and degraded, and acetonitrile oxidative degradation was avoided. The bubbling time was controlled at 450 seconds. After the bubbling was completed, the low-temperature plasma oxidation and impurity removal was completed, and the solid matter (loaded catalyst) was filtered and recovered to obtain an oxidized and impurity-removed liquid. At the same time, during the low-temperature plasma oxidation and impurity removal process, the waste gas generated was collected and discharged to a waste gas treatment device for treatment.

[0075] During the low-temperature plasma oxidation and impurity removal process, the total volume of the reaction gas introduced is 5.7 times the total volume of the pretreatment liquid.

[0076] The weight ratio of the loaded catalyst to the pretreatment liquid was 1.4:100.

[0077] The preparation method of the supported catalyst comprises the following steps: adding manganese nitrate and lanthanum nitrate into deionized water, stirring and dissolving, and preparing a metal salt supported liquid with a concentration of 0.25 mol / L; adding carboxylated multi-walled carbon nanotubes into the metal salt supported liquid, stirring at 42° C. for 3.5 hours, and centrifuging to obtain a solid; drying the solid at 115° C. for 11 hours, calcining at 325° C. for 3.5 hours, and grinding the solid to obtain a supported catalyst.

[0078] In the preparation of the supported catalyst, the molar ratio of manganese nitrate to lanthanum nitrate was 2.1:0.43.

[0079] The weight ratio of the carboxylated multi-walled carbon nanotubes to the metal salt loading liquid is 1:9.

[0080] 3. Adsorption and impurity removal

[0081] Under room temperature conditions, the oxidizing impurity removal liquid was passed through adsorption columns filled with mesoporous activated carbon and 5A molecular sieve at a flow rate of 105 mL / min in sequence, and the residence time of the oxidizing impurity removal liquid in each adsorption column was controlled to be 36.7 min to obtain the adsorption impurity removal liquid.

[0082] The height of the adsorption column filled with mesoporous activated carbon is 1 m and the inner diameter is 7 cm; the filling height of the mesoporous activated carbon is 80% of the height of the adsorption column.

[0083] The adsorption column filled with 5A molecular sieve has a height of 1 m and an inner diameter of 7 cm; the filling height of 5A molecular sieve is 80% of the height of the adsorption column.

[0084] The average particle size of mesoporous activated carbon is 100 μm and the specific surface area is 1300 m 2 / g, and the average pore diameter is 5nm.

[0085] 4. Distillation and refining

[0086] The adsorption and impurity removal liquid was introduced into a distillation tower, and the bottom temperature of the distillation tower was controlled at 86°C, the top temperature was controlled at 82°C, and the reflux ratio was controlled at 5.8:1. Distillation and purification were performed to obtain chromatographic grade acetonitrile.

[0087] Example 3

[0088] This embodiment provides a method for preparing chromatographic grade acetonitrile, wherein the purity is 99.53 wt%, the water content is 0.18 wt%, the acidity (in terms of acetic acid) is 0.005 mmol / g, and the basicity (in terms of OH) is 0. - The evaporation residue was treated with 0.008 wt% of industrial grade acetonitrile, and the specific steps were as follows:

[0089] 1. Preprocessing

[0090] Under room temperature conditions, industrial-grade acetonitrile was passed through an adsorption column filled with 3A molecular sieve at a flow rate of 220 mL / min, and the residence time of the industrial-grade acetonitrile in the adsorption column was controlled to be 17.5 min to obtain a pretreated solution.

[0091] The adsorption column filled with 3A molecular sieve has a height of 1 m and an inner diameter of 7 cm; the filling height of the 3A molecular sieve is 80% of the height of the adsorption column.

[0092] 2. Low-temperature plasma oxidation and impurity removal

[0093] The loaded catalyst was added to the pretreatment liquid, ultrasonically dispersed for 20 minutes, and then placed in a treatment chamber of a low-temperature plasma treatment device. Argon was used to completely replace the air in the treatment chamber. A mixture of argon and oxygen (volume ratio of 100:8) was used as the reaction gas. The discharge voltage of the low-temperature plasma treatment was controlled to be 27 kV, the discharge frequency was 60 Hz, and the discharge power was 250 W. Under room temperature conditions, the reaction gas continuously passed between two discharge plates of the low-temperature plasma treatment device for discharge activation, and then continuously bubbled into the pretreatment liquid through a gas distributor with an average pore size of 50 μm provided at the bottom of the treatment chamber to achieve sufficient gas-liquid contact, so that the impurity components in the pretreatment liquid were controllably oxidized and degraded, and acetonitrile oxidative degradation was avoided. The bubbling time was controlled at 420 s. After the bubbling was completed, the low-temperature plasma oxidation and impurity removal was completed, and the solid matter (loaded catalyst) was filtered and recovered to obtain an oxidized and impurity-removed liquid. At the same time, during the low-temperature plasma oxidation and impurity removal process, the waste gas generated was collected and discharged to a waste gas treatment device for treatment.

[0094] During the low-temperature plasma oxidation and impurity removal process, the total volume of the reaction gas introduced is 6 times the total volume of the pretreatment liquid.

[0095] The weight ratio of the loaded catalyst to the pretreatment liquid was 1.5:100.

[0096] The preparation method of the supported catalyst comprises the following steps: adding manganese nitrate and lanthanum nitrate into deionized water, stirring and dissolving, and preparing a metal salt supported liquid with a concentration of 0.3 mol / L; adding carboxylated multi-walled carbon nanotubes into the metal salt supported liquid, stirring at 45° C. for 4 hours, and centrifuging to obtain a solid; drying the solid at 120° C. for 12 hours, calcining at 330° C. for 4 hours, and grinding the solid to obtain a supported catalyst.

[0097] In the preparation of the supported catalyst, the molar ratio of manganese nitrate to lanthanum nitrate was 2.3:0.5.

[0098] The weight ratio of the carboxylated multi-walled carbon nanotubes to the metal salt loading liquid is 1:10.

[0099] 3. Adsorption and impurity removal

[0100] Under room temperature conditions, the oxidizing impurity removal liquid was passed through adsorption columns filled with mesoporous activated carbon and 5A molecular sieve at a flow rate of 110 mL / min in sequence, and the residence time of the oxidizing impurity removal liquid in each adsorption column was controlled to be 35 min to obtain the adsorption impurity removal liquid.

[0101] The height of the adsorption column filled with mesoporous activated carbon is 1 m and the inner diameter is 7 cm; the filling height of the mesoporous activated carbon is 80% of the height of the adsorption column.

[0102] The adsorption column filled with 5A molecular sieve has a height of 1 m and an inner diameter of 7 cm; the filling height of 5A molecular sieve is 80% of the height of the adsorption column.

[0103] The average particle size of mesoporous activated carbon is 100 μm and the specific surface area is 1300 m 2 / g, and the average pore diameter is 5nm.

[0104] 4. Distillation and refining

[0105] The adsorption and impurity removal liquid was introduced into a distillation tower, and the bottom temperature of the distillation tower was controlled at 87°C, the top temperature was controlled at 83°C, and the reflux ratio was 6:1. Distillation and purification were carried out to obtain chromatographic grade acetonitrile.

[0106] Comparative Example 1

[0107] The technical solution of Example 2 is adopted, except that the supported catalyst used in the low-temperature plasma oxidation and impurity removal step is omitted.

[0108] Comparative Example 2

[0109] The technical solution of Example 2 is adopted, with the following differences: 1) the pretreatment step is omitted, and industrial-grade acetonitrile is directly subjected to low-temperature plasma oxidation to remove impurities; 2) in the adsorption removal step, 3A molecular sieve is used instead of mesoporous activated carbon.

[0110] The purity, moisture content, acidity (in acetic acid), basicity (in OH) of the acetonitrile products obtained in Examples 1-3 and Comparative Examples 1-2 were detected and counted respectively. - The absorbance of each acetonitrile product at 200nm, 210nm, 220nm, 230nm, 240nm, and 250nm was measured. The specific results are shown in the following table:

[0111]

[0112] As can be seen, the method for preparing chromatographic-grade acetonitrile of the present invention first uses a pretreatment step to remove most of the water in industrial-grade acetonitrile using an adsorption column filled with 3A molecular sieve to obtain a pretreatment liquid. This avoids the problem of excessive water content in the acetonitrile interfering with the plasma treatment during the subsequent low-temperature plasma oxidation and impurity removal process, thereby improving the treatment efficiency and performance of the subsequent low-temperature plasma oxidation and impurity removal. Then, in the low-temperature plasma oxidation and impurity removal step, by using a reactant gas with a specific composition and ratio and under specific plasma treatment process parameters (discharge voltage, discharge frequency, and discharge power), the reactant gas is activated by discharge and then bubbled into the pretreatment liquid. Simultaneously, the supported catalyst selectively catalyzes the impurities, thereby achieving controllable and highly selective oxidative degradation of the impurities in the pretreatment liquid. Furthermore, by precisely controlling the aforementioned reactant gas ratio, plasma treatment process parameters, and bubbling time, excessive oxidation of the acetonitrile is avoided, the acetonitrile component in the pretreatment liquid is retained, and an oxidative impurity removal liquid is produced. In the adsorption step, the oxidized impurity-removal liquid is sequentially passed through adsorption columns packed with mesoporous activated carbon and 5A molecular sieves to specifically adsorb any remaining impurities, producing an adsorption-removal liquid. Finally, the adsorption-removal liquid is purified by distillation to produce chromatography-grade acetonitrile.

[0113] It can be seen from Comparative Example 1 that after omitting loaded catalyst in low-temperature plasma oxidation impurity removal step, due to the lack of loaded catalyst to the selective catalysis of impurity components in pre-treatment liquid, under the conditions of the reaction gas of same composition and proportioning, same plasma treatment process parameter, same bubbling time, the oxidation impurity removal effect for impurity components in pre-treatment liquid is reduced;And, the impurity components remaining in its obtained oxidation impurity removal liquid also cannot be effectively removed by subsequent adsorption impurity removal, rectification and purification process. Specifically manifested as, the purity, acidity, basicity and yield of the acetonitrile product obtained in Comparative Example 1 all show relatively obvious deterioration, and the absorbance of acetonitrile product at 200nm, 210nm, 220nm, 230nm, 240nm, 250nm all show relatively obvious rising, also show that its refining impurity removal effect for technical grade acetonitrile is reduced.

[0114] It can be seen from Comparative Example 2 that after omitting the pretreatment step, it is impossible to avoid the problem of interfering with the plasma treatment due to the excessively high moisture content in industrial-grade acetonitrile during the low-temperature plasma oxidation and impurity removal process, which directly leads to the treatment efficiency and treatment performance of the low-temperature plasma oxidation and impurity removal. At the same time, 3A molecular sieves are used to replace mesoporous activated carbon in the adsorption and impurity removal step, and it is impossible to achieve targeted adsorption of residual impurity components in the oxidation and impurity removal liquid. Specifically, the purity, acidity, and basicity of the acetonitrile product obtained in Comparative Example 2 all show a certain degree of deterioration, and the absorbance of the acetonitrile product at 200nm, 210nm, 220nm, 230nm, 240nm, and 250nm all show a certain degree of increase.

[0115] Furthermore, chromatography-grade acetonitrile was prepared five times using the technical solutions of Example 2 and Comparative Example 1, respectively, to verify batch consistency. During this process, the supported catalyst used in Example 2 was not replaced and was reused five times. The yield, moisture content, acidity, evaporation residue, absorbance at 200 nm, and absorbance at 210 nm of each batch of acetonitrile product were measured and statistically analyzed. The aforementioned indicators were compared with the corresponding indicators of the acetonitrile product produced in the first batch to determine whether the indicator fluctuation exceeded the threshold.

[0116] Specifically, the criterion for determining the yield of the acetonitrile product is: whether the difference between the acetonitrile yield (%) of the current batch and the acetonitrile yield (%) of the first batch is within the range of ±1.5%; within the threshold range, it is an acceptable fluctuation in the production index; exceeding the threshold range, it is an unacceptable fluctuation in the production index.

[0117] The criteria for determining the moisture content of acetonitrile products is: whether the difference between the moisture content (wt%) of the current batch of acetonitrile and the moisture content (wt%) of the first batch of acetonitrile is within the range of ±0.0005wt%; within the threshold range, it is an acceptable production indicator fluctuation; outside the threshold range, it is an unacceptable production indicator fluctuation.

[0118] The criteria for determining the acidity of acetonitrile products are: whether the difference between the acidity (mmol / g) of the current batch of acetonitrile and the acidity (mmol / g) of the first batch of acetonitrile is within the range of ±0.0001mmol / g; fluctuations within the threshold range are considered acceptable production indicator fluctuations, while fluctuations beyond the threshold range are considered unacceptable production indicator fluctuations.

[0119] The criteria for determining the evaporation residue of acetonitrile products are: whether the difference between the acetonitrile evaporation residue (ppm) of the current batch and the acetonitrile evaporation residue (ppm) of the first batch is within the range of ±0.5ppm; within the threshold range, it is an acceptable production indicator fluctuation; exceeding the threshold range, it is an unacceptable production indicator fluctuation.

[0120] The judgment standard for the 200nm absorbance of acetonitrile products is: whether the difference between the 200nm absorbance of the current batch of acetonitrile and the 200nm absorbance of the first batch of acetonitrile is within the range of ±0.002; within the threshold range, it is an acceptable production indicator fluctuation, and beyond the threshold range, it is an unacceptable production indicator fluctuation.

[0121] The judgment standard for the 210nm absorbance of acetonitrile products is: whether the difference between the 210nm absorbance of the current batch of acetonitrile and the 210nm absorbance of the first batch of acetonitrile is within the range of ±0.001; within the threshold range, it is an acceptable production indicator fluctuation; exceeding the threshold range is an unacceptable production indicator fluctuation.

[0122] The specific results are shown in the following table:

[0123]

[0124] It can be seen that the preparation method of chromatographic grade acetonitrile of the present invention, the quality of chromatographic grade acetonitrile prepared using technical grade acetonitrile as raw material is stable, and the fluctuation of each index is within the allowed threshold range, and batch consistency is good; At the same time, the reuse performance of the loaded catalyst adopted in the low-temperature plasma oxidation and impurity removal step is good, and it can still maintain good catalytic performance after repeated reuse. It can be seen from Comparative Example 1 that after omitting the loaded catalyst in the low-temperature plasma oxidation and impurity removal step, the batch consistency of the acetonitrile product obtained is reduced, and the stable quality of the acetonitrile product cannot be maintained. It is specifically manifested as the fluctuation of the yield, acidity, 200nm absorbance, and 210nm absorbance of the acetonitrile product obtained exceeds the allowed threshold range.

[0125] Unless otherwise specified, all percentages used in the present invention are by mass.

[0126] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art will be able to modify the technical solutions described in the aforementioned embodiments or substitute equivalents for some of the technical features. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A method for preparing chromatographic grade acetonitrile, characterized in that, The process consists of the following steps: pretreatment, low-temperature plasma oxidation and impurity removal, adsorption and impurity removal, and distillation and refining; In the pretreatment, industrial-grade acetonitrile flows through an adsorption column filled with 3A molecular sieve to obtain a pretreated liquid; The low-temperature plasma oxidation and impurity removal comprises the following steps: uniformly mixing a pretreatment liquid and a supported catalyst, placing the mixture in a treatment chamber of a low-temperature plasma treatment device, using a mixture of argon and oxygen as a reaction gas under argon atmosphere protection, controlling the discharge voltage of the low-temperature plasma treatment to be 25-27 kV, the discharge frequency to be 55-60 Hz, and the discharge power to be 220-250 W, and continuously introducing the reaction gas below the liquid level of the pretreatment liquid for bubbling after activation by low-temperature plasma discharge at room temperature; and filtering after the bubbling is completed to obtain an oxidation and impurity removal liquid; The supported catalyst is prepared by using carboxylated multi-walled carbon nanotubes as a support, which are immersed in a metal salt loading solution containing manganese and lanthanum, and then dried and calcined. The adsorption impurity removal, oxidation impurity removal liquid flows through the adsorption column filled with mesoporous activated carbon and 5A molecular sieve in sequence to obtain the adsorption impurity removal liquid; The adsorption and impurity removal liquid is refined by distillation to obtain chromatographic grade acetonitrile.

2. The preparation method of chromatography grade acetonitrile according to claim 1, wherein In the pretreatment, the flow rate of industrial-grade acetonitrile is 200-220 mL / min, and the residence time of industrial-grade acetonitrile in the adsorption column is 17-26 min.

3. The preparation method of chromatography grade acetonitrile according to claim 1, wherein In the low-temperature plasma oxidation and impurity removal, the volume ratio of argon and oxygen in the reaction gas is 100:7-8; The total volume of the reaction gas introduced is 5-6 times the total volume of the pretreatment liquid; The weight ratio of the loaded catalyst to the pretreatment liquid is 1.2-1.5:

100.

4. The preparation method of chromatography grade acetonitrile according to claim 1, wherein In the low-temperature plasma oxidation and impurity removal, the reaction gas is activated by low-temperature plasma discharge and then bubbled into the pretreatment liquid through a microporous aeration head or a gas distributor arranged at the bottom of the treatment chamber; The bubbling time was controlled to be 420-480s.

5. The method for preparing chromatography-grade acetonitrile according to claim 1, wherein The preparation method of the supported catalyst comprises the following steps: dissolving manganese nitrate and lanthanum nitrate in deionized water to prepare a metal salt supported liquid; immersing carboxylated multi-walled carbon nanotubes in the metal salt supported liquid at 40-45° C., and separating to obtain a solid; and calcining the dried solid at 320-330° C. to prepare the supported catalyst.

6. The method for preparing chromatography-grade acetonitrile according to claim 5, wherein In the preparation of the supported catalyst, the metal salt concentration of the metal salt supported liquid is 0.2-0.3 mol / L; The molar ratio of manganese nitrate to lanthanum nitrate is 2-2.3:0.4-0.

5.

7. The method for preparing chromatography-grade acetonitrile according to claim 5, wherein In the preparation of the supported catalyst, the weight ratio of carboxylated multi-walled carbon nanotubes to metal salt supported liquid is 1:8-10; The calcination time at 320-330°C is 3-4h.

8. The method for preparing chromatography-grade acetonitrile according to claim 1, wherein In the adsorption impurity removal, the flow rate of the oxidative impurity removal liquid is 100-110 mL / min; The residence time of the oxidation and impurity removal liquid in each adsorption column is 35-55 minutes.

9. The method for preparing chromatography-grade acetonitrile according to claim 1, wherein In the adsorption and impurity removal, the average particle size of the mesoporous activated carbon is 80-100 μm, and the specific surface area is 1200-1300 m 2 / g, and the average pore size is 3-8nm.

10. The method for preparing chromatography-grade acetonitrile according to claim 1, wherein The distillation and refining process comprises introducing the adsorption and impurity removal liquid into a distillation tower, controlling the bottom temperature of the distillation tower to be 85-87° C., the top temperature to be 80-83° C., and the reflux ratio to be 5-6:1, and performing distillation and refining to obtain chromatographic grade acetonitrile.

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