CN117486756B - Preparation method of high-purity acetonitrile - Google Patents

Preparation method of high-purity acetonitrile Download PDF

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CN117486756B
CN117486756B CN202311811477.3A CN202311811477A CN117486756B CN 117486756 B CN117486756 B CN 117486756B CN 202311811477 A CN202311811477 A CN 202311811477A CN 117486756 B CN117486756 B CN 117486756B
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reactor
acetonitrile
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CN117486756A (en
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吴绍帅
包瑞
万柄呈
朱宝仁
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Ningxia Zhonghui Chemical Co ltd
Weifang Zhonghui Chemical Co ltd
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Weifang Zhonghui Chemical Co ltd
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Abstract

The invention provides a preparation method of high-purity acetonitrile, belonging to the field of high-purity acetonitrile. The preparation method of the high-purity acetonitrile comprises the following steps: preheating, primary reaction, secondary reaction, primary cooling and impurity removal, secondary cooling and impurity removal and rectification. The preparation method of the high-purity acetonitrile can effectively inhibit side reaction in the process of generating acetonitrile by reacting acetic acid with ammonia gas, reduce the impurity content in the prepared acetonitrile, improve the purity and yield of the acetonitrile, and simplify the subsequent refining process; the problems of quick attenuation of the catalyst activity and short overall catalytic life are effectively avoided, and the efficient, stable and continuous operation of production can be realized; and further improves the storage stability of the acetonitrile catalyst prepared by acetic acid ammoniation.

Description

Preparation method of high-purity acetonitrile
Technical Field
The invention relates to the field of high-purity acetonitrile, in particular to a preparation method of high-purity acetonitrile.
Background
Acetonitrile is a colorless transparent liquid, and its most important uses are as a solvent, such as a solvent for extracting butadiene and a solvent for organic synthesis. Meanwhile, acetonitrile is an important raw material of medicines (vitamin B1) and flavor intermediates, and high-purity acetonitrile can be used as a mobile phase of liquid chromatography or an important solvent for preparing medicines such as purified insulin, taxol and the like.
The synthesis method of acetonitrile in the prior art mainly comprises the following steps: acetonitrile as a byproduct of the preparation of acrylonitrile by ammoxidation of propylene, an acetylene ammonification method, an ethanol ammonification method and an acetic acid ammonification method. At present, the acetic acid ammonification method has the advantages of mild reaction conditions, simple operation and higher product yield, and becomes an important direction of acetonitrile preparation research.
In the traditional process for synthesizing acetonitrile by an acetic acid ammonification method, gasified ammonia gas and acetic acid are generally put into a reaction kettle, and ammonification reaction is carried out under the action of a catalyst taking aluminum oxide and activated clay as carriers to obtain an acetonitrile crude product; the crude product is refined to remove impurities, and the like, so as to prepare the high-purity acetonitrile.
However, in the existing method for preparing high-purity acetonitrile by ammonifying acetic acid, in the actual production process of acetonitrile generated by reacting acetic acid with ammonia gas, side reactions cannot be effectively inhibited, more impurities exist in the prepared crude acetonitrile product, and the purity and yield of acetonitrile are low; in the subsequent refining process of preparing high-purity acetonitrile by adopting an acetonitrile crude product, the difficulty of removing impurities is high, the operation is complex, the refining energy consumption is high, and the production efficiency is poor; furthermore, in the process of continuously producing acetonitrile by acetic acid ammoniation, the catalyst has the problems of quick attenuation of catalytic activity, short overall catalytic life and high catalytic production cost, and the continuous production interruption caused by stopping production and changing the catalyst can not maintain the high-efficiency stable continuous operation of a production system. Meanwhile, the storage stability of the existing acetonitrile catalyst prepared by acetic acid ammoniation needs to be further improved.
Disclosure of Invention
In order to solve the technical problems in the prior art, the invention provides the preparation method of the high-purity acetonitrile, which can effectively inhibit side reaction in the process of generating acetonitrile by reacting acetic acid with ammonia gas, reduce the impurity content in the prepared acetonitrile, improve the purity and yield of the acetonitrile, and has simple subsequent refining process; the problems of quick attenuation of the catalyst activity and short overall catalytic life are effectively avoided, and the efficient, stable and continuous operation of production can be realized; and further improves the storage stability of the acetonitrile catalyst prepared by acetic acid ammoniation.
In order to solve the technical problems, the technical scheme adopted by the invention is as follows:
The preparation method of the high-purity acetonitrile comprises the following steps: preheating, primary reaction, secondary reaction, primary cooling and impurity removal, secondary cooling and impurity removal and rectification.
The preheating method comprises the steps of respectively metering acetic acid and ammonia gas, feeding the metered acetic acid and ammonia gas into a first micro-reactor of a micro-channel reaction device, and controlling the temperature of the first micro-reactor to be 140-150 ℃ to obtain a preheated material;
In the preheating, the molar ratio of acetic acid to ammonia is 1:1.2-1.3.
The primary reaction method comprises the steps of feeding preheated materials into a second micro-reactor of a micro-channel reaction device, controlling the temperature of the second micro-reactor to be 380-400 ℃, and controlling the residence time of the materials in the second micro-reactor to be 180-210s to obtain a primary reactant;
In the first-stage reaction, a micro-reaction catalyst is filled in the second micro-reactor; in the second microreactor, the loading of the microreaction catalyst is 0.8-1% of the total feeding weight of acetic acid in 1h in the preheating step.
The micro-reaction catalyst is prepared by the following steps: preparing a precursor, preparing an active matrix and performing composite molding.
The method for preparing the precursor comprises the steps of putting lanthanum nitrate hexahydrate and zirconium nitrate pentahydrate into deionized water, performing ultrasonic dispersion for 10-20min, stirring and putting glycine and citric acid into the solution, and continuing stirring for 10-20min after putting materials into the solution; then stirring and heating to 180-190 ℃ at a heating rate of 3-3.5 ℃/min, preserving heat for 30-40min, naturally cooling to 50-60 ℃, preserving heat, regulating the pH value to 9-10 by adopting ammonia water, and filtering out solid matters; washing the solid with deionized water to neutrality, transferring into a roasting furnace, heating to 350-400 ℃ at a heating rate of 4-5 ℃/min, and roasting for 2-3h at a temperature maintaining speed to obtain the precursor.
In the preparation of the precursor, the weight ratio of lanthanum nitrate hexahydrate to zirconium nitrate pentahydrate to glycine to citric acid to deionized water is 173-217:172-215:15-22.5:19-28:1400-1500.
The method for preparing the active matrix comprises the steps of putting a precursor, cerium oxide and praseodymium oxide into a high-temperature ball mill, completely replacing air in the high-temperature ball mill by adopting argon, controlling the ball-material ratio to be 8-10:1, controlling the ball milling rotating speed to be 100-150rpm, performing heat preservation and ball milling for 9-10 hours at 550-600 ℃, and naturally cooling to room temperature to obtain a ball-milled material; and uniformly mixing the ball-milling material and the mesoporous activated carbon according to the weight ratio of 1:0.5-0.6, and granulating to obtain the active matrix.
In the preparation of the active matrix, the weight ratio of the precursor to the cerium oxide to the praseodymium oxide is 50-55:4-5:1.5-2;
the particle size of the mesoporous activated carbon is 120-150 mu m, and the specific surface area is 1000-1100m 2/g.
The composite molding method comprises the steps of adding isopropyl aluminum into deionized water with the weight being 1.8-2.2 times of that of the aluminum under the stirring condition at the feeding rate of 6-7 g/min; heating to 80-90 ℃ after the input of isopropyl aluminum is completed, and preserving heat and stirring for 40-50min; continuously adding 1-1.1mol/L nitric acid solution under stirring, and carrying out heat preservation, reflux and stirring for 5-6 h; continuously adding copper nitrate solution with the concentration of 0.1-0.12mol/L under the stirring condition, and keeping the temperature at 60-70 ℃ and stirring for 1-2h to prepare sol solution; adding the active matrix into sol solution, uniformly dispersing by ultrasonic, stirring for 20-40min, and filtering out solid matters; transferring the solid into a roasting furnace, heating to 700-750 ℃ at a heating rate of 3-4 ℃/min, and roasting for 2-3h at a temperature maintaining speed to obtain the micro-reaction catalyst.
In the composite molding, the weight ratio of the isopropyl aluminum to the nitric acid solution to the copper nitrate solution is 1:0.4-0.45:2.3-2.5;
the volume ratio of the active matrix to the sol solution is 0.25-0.3:1.
The method for the secondary reaction comprises the steps that a primary reactant is fed into a third micro-reactor of a micro-channel reaction device, the temperature of the third micro-reactor is controlled to be 300-330 ℃, and the retention time of materials in the third micro-reactor is 120-180s, so that a secondary reactant is obtained;
In the second-stage reaction, a micro-reaction catalyst is filled in the third micro-reactor, and the micro-reaction catalyst is the same as the micro-reaction catalyst in the first-stage reaction; in the third microreactor, the loading of the microreaction catalyst is 0.8-1% of the total feeding weight of acetic acid in 1h in the preheating step.
The first-stage cooling and impurity removing method is that the second-stage reactant is fed into a fourth micro-reactor of a micro-channel reaction device, the temperature of the fourth micro-reactor is controlled to be 85-90 ℃, and the residence time of materials in the fourth micro-reactor is controlled to be 420-480s, so that the first-stage impurity removing is obtained.
In the first-stage cooling and impurity removal process, a fourth micro-reactor is filled with a mixture of mesoporous activated carbon and modified hydrotalcite; the weight ratio of the mesoporous activated carbon to the modified hydrotalcite is 1:1.8-2; the loading amount of the mesoporous activated carbon and the modified hydrotalcite is 1.5-1.6% of the total weight of acetic acid fed in 1h in the preheating step;
The mesoporous activated carbon has a particle size of 150-200 μm, a specific surface area of 1100-1200m 2/g, an average pore diameter of 5-10nm, and graphitization degree (XRD method) of 55-60%.
The preparation method of the modified hydrotalcite comprises the steps of adding cerium nitrate hexahydrate, aluminum nitrate nonahydrate, zinc nitrate hexahydrate and magnesium nitrate hexahydrate into deionized water under stirring, and uniformly stirring to obtain a first liquid; under the stirring condition, sodium carbonate and sodium hydroxide are added into deionized water, and uniformly stirred to obtain a second liquid; dropwise adding the second liquid into the first liquid under the stirring condition of 200-300rpm until the pH value of the first liquid is 9.5-10.5, stopping dropwise adding the second liquid, continuing stirring for 2-3h, standing for 22-24h, and filtering out solid matters; washing solid with deionized water for 3-4 times, drying at 95-105 deg.C for 10-12 hr, transferring into roasting furnace, heating to 500-530 deg.C, roasting for 3-4 hr, naturally cooling, and grinding uniformly to obtain modified hydrotalcite.
In the preparation of the modified hydrotalcite, in a first liquid, the weight ratio of cerium nitrate hexahydrate, aluminum nitrate nonahydrate, zinc nitrate hexahydrate, magnesium nitrate hexahydrate and deionized water is 14-14.5:12-12.5:3.8-4:12.5-13:100-110;
in the second liquid, the weight ratio of the sodium carbonate to the sodium hydroxide to the deionized water is 5.3-5.5:4-4.2:100.
The method for removing impurities by cooling the second stage comprises the steps of feeding the first-stage impurities into a fifth micro-reactor of a micro-channel reaction device, controlling the temperature of the fifth micro-reactor to be 75-80 ℃, cooling, removing impurities, and discharging to obtain second-stage impurity removing liquid;
In the secondary cooling and impurity removal, a fifth micro-reactor is filled with a mixture of mesoporous activated carbon and modified hydrotalcite, and the modified hydrotalcite is the same as the modified hydrotalcite adopted in the primary cooling and impurity removal; the weight ratio of the mesoporous activated carbon to the modified hydrotalcite is 1:1.8-2; the loading of the mesoporous activated carbon and the modified hydrotalcite is 1.7-1.8% of the total weight of acetic acid fed in 1h in the preheating step.
The rectification method comprises the steps of introducing secondary impurity removal liquid into a buffer tank, and rectifying by adopting a continuous rectifying device to obtain high-purity acetonitrile;
in the rectification, the rectification temperature is 90-100 ℃, and the rectification pressure is 0.2-0.3MPa.
Compared with the prior art, the invention has the beneficial effects that:
(1) According to the preparation method of the high-purity acetonitrile, in the preheating step, a first micro-reactor of a micro-channel reaction device is adopted to carry out mixed preheating on acetic acid and ammonia; in the first stage reaction process, carrying out first-stage acetic acid ammoniation reaction in a second microreactor in the presence of a microreaction catalyst; in the second-stage reaction process, carrying out second-stage acetic acid ammoniation reaction in a third microreactor in the presence of a microreaction catalyst; then sequentially carrying out primary cooling impurity removal and secondary cooling impurity removal on the secondary reactant under the condition of mesoporous activated carbon and modified hydrotalcite, carrying out targeted adsorption on impurities generated in the ammonification reaction process of acetic acid, obtaining cooled secondary impurity removal liquid, and rectifying to obtain high-purity acetonitrile; in the process of generating acetonitrile by reacting acetic acid with ammonia gas, the generation of side reaction can be effectively inhibited, the impurity content in the prepared acetonitrile is reduced, the purity and yield of the acetonitrile are improved, the pressure and energy consumption of the subsequent refining process are reduced, the refining operation process is simplified, and the production efficiency is improved; meanwhile, in the preparation process of the micro-reaction catalyst, lanthanum nitrate, zirconium nitrate and glycine are adopted to prepare and obtain a precursor doped with lanthanum zirconate and carbon; then performing high-temperature ball milling on the precursor, cerium oxide and praseodymium oxide to further obtain cerium and praseodymium doped precursors (namely ball milling matters); mixing the ball-milled material with mesoporous activated carbon to prepare an active matrix; then compounding the active matrix with CuO/gamma-Al 2O3 to prepare a micro-reaction catalyst; the catalytic stability of the micro-reaction catalyst in the micro-channel reaction is improved pertinently, the problems of rapid activity decay and short overall catalytic life of the catalyst are effectively avoided, and the efficient, stable and continuous production of acetonitrile by micro-channel acetic acid ammoniation is realized; and the storage stability of the micro-reaction catalyst is improved, and the problems of caking, pulverization, reduced catalytic activity and the like of the micro-reaction catalyst in the long-term storage process are avoided. Furthermore, cerium/zinc elements are adopted for hydrotalcite modification to prepare modified hydrotalcite, and the modified hydrotalcite is matched with mesoporous activated carbon and is used for primary cooling impurity removal and secondary cooling impurity removal, and aiming at micro-channel reaction conditions and secondary reactant working conditions, impurities in the secondary reactant are subjected to targeted adsorption while the secondary reactant is cooled, so that the impurity content in acetonitrile synthesized materials is further reduced, and the efficient performance of subsequent refining procedures is facilitated.
(2) In the preparation method of the high-purity acetonitrile, the content of acetonitrile in the prepared secondary impurity-removing liquid (namely acetonitrile synthetic liquid) can reach 57.0wt%, the content of impurities can be reduced to 0.08wt%, and the yield of acetonitrile can reach 94.9%.
(3) According to the preparation method of the high-purity acetonitrile, the purity of the prepared high-purity acetonitrile is 99.95-99.98wt%, the moisture content is 0.005-0.008wt%, the acidity is not more than 0.0002mmol/L, the alkalinity is not more than 0.0001mmol/L, and the evaporation residue is not more than 0.0004wt%.
(4) By adopting the preparation method of the high-purity acetonitrile, after the high-purity acetonitrile is continuously prepared for 120 days, the acetonitrile content in the prepared secondary impurity-removing liquid can still reach 56.8wt%, the acetonitrile yield can still reach 94.6, and the impurity content is not more than 0.15wt%.
(5) In the preparation method of the high-purity acetonitrile, the adopted micro-reaction catalyst has no caking or pulverization phenomenon after standing and storing for 360 days in an environment with the temperature of 28 ℃ and the relative humidity of 50%, and has good storage stability and no obvious difference with a new catalyst after long-term storage.
Detailed Description
Specific embodiments of the present invention will now be described in order to provide a clearer understanding of the technical features, objects and effects of the present invention.
Example 1
A preparation method of high-purity acetonitrile specifically comprises the following steps:
1. preheating
Acetic acid is conveyed into a first micro-reactor of the micro-channel reaction device after being metered; simultaneously, gasifying liquid ammonia into ammonia gas by a carburetor, and conveying the ammonia gas into a first micro-reactor of the micro-channel reaction device after metering; the temperature of the first micro-reactor was controlled at 140℃and the residence time of the material in the first micro-reactor was 100s, obtaining a preheated material.
In the preheating process, the molar ratio of acetic acid to ammonia is 1:1.2.
2. First-order reaction
And (3) feeding the preheated materials into a second micro-reactor of the micro-channel reaction device, controlling the temperature of the second micro-reactor to be 380 ℃ and the material residence time to be 180s, so as to obtain a first-stage reactant.
Wherein the second microreactor is filled with a microreaction catalyst; in the second microreactor, the loading of the microreaction catalyst was 0.8% of the total weight of acetic acid fed in 1h in the preheating step.
The micro-reaction catalyst is prepared by the following steps:
1) Preparation of the precursor
Putting lanthanum nitrate hexahydrate and zirconium nitrate pentahydrate into deionized water, performing ultrasonic dispersion for 10min, stirring and putting glycine and citric acid into the deionized water, and continuing stirring for 10min after the putting of each material is completed; then stirring and heating to 180 ℃ at a heating rate of 3 ℃/min, preserving heat for 30min, naturally cooling to 50 ℃, preserving heat, regulating the pH value to 9 by adopting ammonia water, and filtering out solid matters; washing the solid to be neutral by deionized water, transferring into a roasting furnace, heating to 350 ℃ at a heating rate of 4 ℃/min, and carrying out heat preservation and roasting for 2 hours to obtain the precursor.
Wherein the weight ratio of lanthanum nitrate hexahydrate to zirconium nitrate pentahydrate to glycine to citric acid to deionized water is 173:172:15:19:1400.
2) Preparation of the active matrix
Putting the precursor, cerium oxide and praseodymium oxide into a high-temperature ball mill, completely replacing air in the high-temperature ball mill by adopting argon, controlling the ball-material ratio to be 8:1, controlling the ball milling rotation speed to be 100rpm, performing heat preservation and ball milling at 550 ℃ for 9 hours, and naturally cooling to room temperature to obtain a ball-milled material; and uniformly mixing the ball-milling material and the mesoporous activated carbon according to the weight ratio of 1:0.5, and granulating to obtain the active matrix.
Wherein the weight ratio of the precursor, the cerium oxide and the praseodymium oxide is 50:4:1.5.
The particle size of the mesoporous activated carbon is 120 mu m, and the specific surface area is 1000m 2/g.
3) Composite forming
Under the stirring condition, adding isopropyl aluminum into deionized water with the weight being 1.8 times of that of the isopropyl aluminum at the feeding rate of 6 g/min; after the input of the isopropyl aluminum is completed, the temperature is raised to 80 ℃, and the mixture is stirred for 40min under heat preservation; continuously adding a nitric acid solution with the concentration of 1mol/L under the stirring condition, and carrying out heat preservation, reflux and stirring for 5 hours; continuously adding copper nitrate solution with the concentration of 0.1mol/L under the stirring condition, and carrying out heat preservation and stirring for 1h at 60 ℃ to obtain sol solution; adding the active matrix into the sol solution, uniformly dispersing by ultrasonic, stirring for 20min, and filtering out solid matters; transferring the solid into a roasting furnace, heating to 700 ℃ at a heating rate of 3 ℃/min, and roasting for 2 hours at a temperature maintaining speed to obtain the micro-reaction catalyst.
Wherein the weight ratio of the isopropyl aluminum to the nitric acid solution to the copper nitrate solution is 1:0.4:2.3.
The volume ratio of the active matrix to the sol solution was 0.25:1.
3. Secondary reaction
And feeding the first-stage reactant into a third micro-reactor of the micro-channel reaction device, controlling the temperature of the third micro-reactor to be 300 ℃ and the material residence time to be 120s, so as to obtain a second-stage reactant.
Wherein, the third micro-reactor is filled with a micro-reaction catalyst which is the same as the micro-reaction catalyst in the primary reaction.
In the third microreactor, the loading of the microreaction catalyst is 0.8% of the total weight of acetic acid fed in 1h in the preheating step.
4. First-stage cooling impurity removal
And feeding the second-stage reactant into a fourth micro-reactor of the micro-channel reaction device, controlling the temperature of the fourth micro-reactor to 850 ℃, and controlling the material residence time to 420s to obtain the first-stage impurity removal.
Wherein, the fourth micro-reactor is filled with a mixture of mesoporous activated carbon and modified hydrotalcite; the weight ratio of the mesoporous activated carbon to the modified hydrotalcite is 1:1.8; the loading of the mesoporous activated carbon and the modified hydrotalcite is 1.5 percent of the total weight of acetic acid fed in 1 hour in the preheating step.
The mesoporous activated carbon has a particle size of 150 μm, a specific surface area of 1100m 2/g, an average pore diameter of 5nm, and a graphitization degree (XRD method) of 55%.
The modified hydrotalcite is prepared by the following method:
Under the stirring condition, cerium nitrate hexahydrate, aluminum nitrate nonahydrate, zinc nitrate hexahydrate and magnesium nitrate hexahydrate are put into deionized water and uniformly stirred to obtain a first liquid; under the stirring condition, sodium carbonate and sodium hydroxide are added into deionized water, and uniformly stirred to obtain a second liquid; under the stirring condition of 200rpm, dropwise adding the second liquid into the first liquid at the dropwise adding rate of 20mL/min until the pH value of the first liquid is 9.5, stopping dropwise adding the second liquid, continuously stirring for 2h, standing for 22h, and filtering out a solid; washing the solid by deionized water for 3 times, preserving heat and drying for 10 hours at 95 ℃, transferring into a roasting furnace, heating to 500 ℃, preserving heat and roasting for 3 hours, naturally cooling, and grinding uniformly to obtain the modified hydrotalcite.
In the first liquid, the weight ratio of cerium nitrate hexahydrate, aluminum nitrate nonahydrate, zinc nitrate hexahydrate, magnesium nitrate hexahydrate and deionized water is 14:12:3.8:12.5:100.
In the second liquid, the weight ratio of sodium carbonate to sodium hydroxide to deionized water is 5.3:4:100.
5. Two-stage cooling and impurity removing
Feeding the first-stage impurity removal into a fifth micro-reactor of the micro-channel reaction device, controlling the temperature of the fifth micro-reactor to be 75 ℃, cooling, removing impurities, and discharging to obtain a second-stage impurity removal liquid.
Wherein, the fifth micro-reactor is filled with a mixture of mesoporous activated carbon and modified hydrotalcite, and the modified hydrotalcite is the same as the modified hydrotalcite adopted for primary cooling and impurity removal; the weight ratio of the mesoporous activated carbon to the modified hydrotalcite is 1:1.8; the loading of the mesoporous activated carbon and the modified hydrotalcite is 1.7 percent of the total weight of acetic acid fed in 1 hour in the preheating step.
In the secondary impurity removing liquid, the acetonitrile content is 56.3wt%, the impurity content is 0.09wt%, and the acetonitrile yield is 94.1%.
6. Rectifying
And (3) introducing the secondary impurity removing liquid into a buffer tank, and rectifying by adopting a continuous rectifying device to obtain the high-purity acetonitrile with the purity of more than 99.9%.
Wherein the rectification temperature is 90 ℃, and the rectification pressure is 0.3MPa.
Example 2
A preparation method of high-purity acetonitrile specifically comprises the following steps:
1. preheating
Acetic acid is conveyed into a first micro-reactor of the micro-channel reaction device after being metered; simultaneously, gasifying liquid ammonia into ammonia gas by a carburetor, and conveying the ammonia gas into a first micro-reactor of the micro-channel reaction device after metering; the temperature of the first micro-reactor was controlled at 145 ℃ and the residence time of the material in the first micro-reactor was 110s, obtaining a preheated material.
In the preheating process, the molar ratio of acetic acid to ammonia is 1:1.25.
2. First-order reaction
And (3) feeding the preheated materials into a second micro-reactor of the micro-channel reaction device, controlling the temperature of the second micro-reactor to be 390 ℃ and the material residence time to be 200s, so as to obtain a first-stage reactant.
Wherein the second microreactor is filled with a microreaction catalyst; in the second microreactor, the loading of the microreaction catalyst was 0.9% of the total weight of acetic acid fed in 1h in the preheating step.
The micro-reaction catalyst is prepared by the following steps:
1) Preparation of the precursor
Putting lanthanum nitrate hexahydrate and zirconium nitrate pentahydrate into deionized water, performing ultrasonic dispersion for 15min, stirring and putting glycine and citric acid into the deionized water, and continuing stirring for 15min after the putting of each material is completed; then stirring and heating to 185 ℃ at a heating rate of 3.2 ℃/min, preserving heat for 35min, naturally cooling to 55 ℃, preserving heat, regulating the pH value to 9.5 by adopting ammonia water, and filtering out solid matters; washing the solid to be neutral by deionized water, transferring the solid into a roasting furnace, heating to 375 ℃ at a heating rate of 4.5 ℃/min, and carrying out heat preservation roasting for 2.5 hours to obtain the precursor.
Wherein, the weight ratio of lanthanum nitrate hexahydrate to zirconium nitrate pentahydrate to glycine to citric acid to deionized water is 195:193:19:22.5:1450.
2) Preparation of the active matrix
Putting the precursor, cerium oxide and praseodymium oxide into a high-temperature ball mill, completely replacing air in the high-temperature ball mill by adopting argon, controlling the ball-material ratio to be 9:1, controlling the ball milling rotation speed to be 120rpm, performing heat preservation ball milling at the ball milling temperature of 580 ℃ for 9.5 hours, and naturally cooling to room temperature to obtain a ball-milled material; and uniformly mixing the ball-milling material and the mesoporous activated carbon according to the weight ratio of 1:0.55, and granulating to obtain the active matrix.
Wherein the weight ratio of the precursor, the cerium oxide and the praseodymium oxide is 52:4.5:1.8.
The particle size of the mesoporous activated carbon is 130 mu m, and the specific surface area is 1050m 2/g.
3) Composite forming
Under the stirring condition, adding isopropyl aluminum into deionized water with the weight being 2 times of that of the isopropyl aluminum at the feeding rate of 6.5 g/min; after the input of the isopropyl aluminum is completed, the temperature is raised to 85 ℃, and the mixture is stirred for 45min under heat preservation; continuously adding a nitric acid solution with the concentration of 1.05mol/L under the stirring condition, and carrying out heat preservation, reflux and stirring for 5.5 hours; continuously adding copper nitrate solution with the concentration of 0.11mol/L under the stirring condition, and keeping the temperature at 65 ℃ and stirring for 1.5h to obtain sol solution; adding the active matrix into the sol solution, uniformly dispersing by ultrasonic, stirring for 30min, and filtering out solid matters; transferring the solid into a roasting furnace, heating to 720 ℃ at a heating rate of 3.5 ℃/min, and roasting for 2.5h at a temperature maintaining speed to obtain the micro-reaction catalyst.
Wherein the weight ratio of the isopropyl aluminum to the nitric acid solution to the copper nitrate solution is 1:0.42:2.4.
The volume ratio of the active matrix to the sol solution was 0.28:1.
3. Secondary reaction
And feeding the first-stage reactant into a third micro-reactor of the micro-channel reaction device, controlling the temperature of the third micro-reactor to 320 ℃ and the material residence time to 160s, so as to obtain a second-stage reactant.
Wherein, the third micro-reactor is filled with a micro-reaction catalyst which is the same as the micro-reaction catalyst in the primary reaction.
In the third microreactor, the loading of the microreaction catalyst is 0.9% of the total weight of acetic acid fed in 1h in the preheating step.
4. First-stage cooling impurity removal
And feeding the second-stage reactant into a fourth micro-reactor of the micro-channel reaction device, controlling the temperature of the fourth micro-reactor to be 87 ℃ and the material residence time to be 450s, so as to obtain the first-stage impurity removal.
Wherein, the fourth micro-reactor is filled with a mixture of mesoporous activated carbon and modified hydrotalcite; the weight ratio of the mesoporous activated carbon to the modified hydrotalcite is 1:1.9; the loading of the mesoporous activated carbon and the modified hydrotalcite is 1.55 percent of the total weight of acetic acid fed in 1 hour in the preheating step.
The mesoporous activated carbon has a particle size of 180 μm, a specific surface area of 1150m 2/g, an average pore diameter of 7nm, and a graphitization degree (XRD method) of 57%.
The modified hydrotalcite is prepared by the following method:
Under the stirring condition, cerium nitrate hexahydrate, aluminum nitrate nonahydrate, zinc nitrate hexahydrate and magnesium nitrate hexahydrate are put into deionized water and uniformly stirred to obtain a first liquid; under the stirring condition, sodium carbonate and sodium hydroxide are added into deionized water, and uniformly stirred to obtain a second liquid; dropwise adding the second liquid into the first liquid at a dropwise adding rate of 22mL/min under the stirring condition of 250rpm until the pH value of the first liquid is 10, stopping dropwise adding the second liquid, continuously stirring for 2.5h, standing for 23h, and filtering out a solid; washing the solid by deionized water for 4 times, preserving heat at 100 ℃ and drying for 11 hours, transferring into a roasting furnace, heating to 515 ℃, preserving heat and roasting for 3.5 hours, naturally cooling, and grinding uniformly to obtain the modified hydrotalcite.
In the first liquid, the weight ratio of cerium nitrate hexahydrate, aluminum nitrate nonahydrate, zinc nitrate hexahydrate, magnesium nitrate hexahydrate and deionized water is 14.2:12.3:3.9:12.7:105.
In the second liquid, the weight ratio of sodium carbonate to sodium hydroxide to deionized water is 5.4:4.1:100.
5. Two-stage cooling and impurity removing
Feeding the first-stage impurity removal into a fifth micro-reactor of the micro-channel reaction device, controlling the temperature of the fifth micro-reactor to be 76 ℃, cooling, removing impurities, and discharging to obtain a second-stage impurity removal liquid.
Wherein, the fifth micro-reactor is filled with a mixture of mesoporous activated carbon and modified hydrotalcite, and the modified hydrotalcite is the same as the modified hydrotalcite adopted for primary cooling and impurity removal; the weight ratio of the mesoporous activated carbon to the modified hydrotalcite is 1:1.9; the loading of the mesoporous activated carbon and the modified hydrotalcite is 1.75 percent of the total weight of acetic acid fed in 1 hour in the preheating step.
In the secondary impurity removing liquid, the acetonitrile content is 57.0wt%, the impurity content is 0.08wt%, and the acetonitrile yield is 94.9%.
6. Rectifying
And (3) introducing the secondary impurity removing liquid into a buffer tank, and rectifying by adopting a continuous rectifying device to obtain the high-purity acetonitrile with the purity of more than 99.9%.
Wherein the rectification temperature is 95 ℃ and the rectification pressure is 0.25MPa.
Example 3
A preparation method of high-purity acetonitrile specifically comprises the following steps:
1. preheating
Acetic acid is conveyed into a first micro-reactor of the micro-channel reaction device after being metered; simultaneously, gasifying liquid ammonia into ammonia gas by a carburetor, and conveying the ammonia gas into a first micro-reactor of the micro-channel reaction device after metering; the temperature of the first micro-reactor was controlled at 150℃and the residence time of the material in the first micro-reactor was 120s, obtaining a preheated material.
In the preheating process, the molar ratio of acetic acid to ammonia is 1:1.3.
2. First-order reaction
And (3) feeding the preheated materials into a second micro-reactor of the micro-channel reaction device, controlling the temperature of the second micro-reactor to be 400 ℃ and the material residence time to be 210s, so as to obtain a first-stage reactant.
Wherein the second microreactor is filled with a microreaction catalyst; in the second microreactor, the loading of the microreaction catalyst is 1% of the total weight of acetic acid fed in 1h in the preheating step.
The micro-reaction catalyst is prepared by the following steps:
1) Preparation of the precursor
Putting lanthanum nitrate hexahydrate and zirconium nitrate pentahydrate into deionized water, performing ultrasonic dispersion for 20min, stirring and putting glycine and citric acid, and continuing stirring for 20min after the putting of each material is completed; then stirring and heating to 190 ℃ at a heating rate of 3.5 ℃/min, preserving heat for 40min, naturally cooling to 60 ℃, preserving heat, regulating the pH value to 10 by adopting ammonia water, and filtering out solid matters; washing the solid to be neutral by deionized water, transferring the solid into a roasting furnace, heating to 400 ℃ at a heating rate of 5 ℃/min, and carrying out heat preservation and roasting for 3 hours to obtain the precursor.
Wherein the weight ratio of lanthanum nitrate hexahydrate to zirconium nitrate pentahydrate to glycine to citric acid to deionized water is 217:215:22.5:28:1500.
2) Preparation of the active matrix
Putting the precursor, cerium oxide and praseodymium oxide into a high-temperature ball mill, completely replacing air in the high-temperature ball mill by adopting argon, controlling the ball-material ratio to be 10:1, controlling the ball milling rotation speed to be 150rpm, performing heat preservation and ball milling at 600 ℃ for 10 hours, and naturally cooling to room temperature to obtain a ball-milled material; and uniformly mixing the ball-milling material and the mesoporous activated carbon according to the weight ratio of 1:0.6, and granulating to obtain the active matrix.
Wherein the weight ratio of the precursor, cerium oxide and praseodymium oxide is 55:5:2.
The particle size of the mesoporous activated carbon is 150 mu m, and the specific surface area is 1100m 2/g.
3) Composite forming
Under the stirring condition, adding isopropyl aluminum into deionized water with the weight being 2.2 times of that of the isopropyl aluminum at the feeding rate of 7 g/min; after the input of the isopropyl aluminum is completed, the temperature is raised to 90 ℃, and the mixture is stirred for 50 minutes with heat preservation; continuously adding a nitric acid solution with the concentration of 1.1mol/L under the stirring condition, and carrying out heat preservation, reflux and stirring for 6 hours; continuously adding copper nitrate solution with the concentration of 0.12mol/L under the stirring condition, and carrying out heat preservation and stirring for 2 hours at the temperature of 70 ℃ to obtain sol solution; adding the active matrix into the sol solution, uniformly dispersing by ultrasonic, stirring for 40min, and filtering out solid matters; transferring the solid into a roasting furnace, heating to 750 ℃ at a heating rate of 4 ℃/min, and roasting for 3 hours at a temperature maintaining speed to obtain the micro-reaction catalyst.
Wherein the weight ratio of the isopropyl aluminum to the nitric acid solution to the copper nitrate solution is 1:0.45:2.5.
The volume ratio of the active matrix to the sol solution is 0.3:1.
3. Secondary reaction
And feeding the first-stage reactant into a third micro-reactor of the micro-channel reaction device, controlling the temperature of the third micro-reactor to be 330 ℃, and controlling the material residence time to be 180s to obtain a second-stage reactant.
Wherein, the third micro-reactor is filled with a micro-reaction catalyst which is the same as the micro-reaction catalyst in the primary reaction.
In the third microreactor, the loading of the microreaction catalyst is 1% of the total weight of acetic acid fed in 1h in the preheating step.
4. First-stage cooling impurity removal
And feeding the second-stage reactant into a fourth micro-reactor of the micro-channel reaction device, controlling the temperature of the fourth micro-reactor to be 90 ℃ and the material residence time to be 480s, so as to obtain the first-stage impurity removal.
Wherein, the fourth micro-reactor is filled with a mixture of mesoporous activated carbon and modified hydrotalcite; the weight ratio of the mesoporous activated carbon to the modified hydrotalcite is 1:2; the loading of the mesoporous activated carbon and the modified hydrotalcite is 1.6 percent of the total weight of acetic acid fed in 1 hour in the preheating step.
The mesoporous activated carbon has a particle size of 200 μm, a specific surface area of 1200m 2/g, an average pore diameter of 10nm, and a graphitization degree (XRD method) of 60%.
The modified hydrotalcite is prepared by the following method:
Under the stirring condition, cerium nitrate hexahydrate, aluminum nitrate nonahydrate, zinc nitrate hexahydrate and magnesium nitrate hexahydrate are put into deionized water and uniformly stirred to obtain a first liquid; under the stirring condition, sodium carbonate and sodium hydroxide are added into deionized water, and uniformly stirred to obtain a second liquid; dropwise adding the second liquid into the first liquid at a dropwise adding rate of 25mL/min under the stirring condition of 300rpm until the pH value of the first liquid is 10.5, stopping dropwise adding the second liquid, continuously stirring for 3h, standing for 24h, and filtering out a solid; washing the solid by deionized water for 4 times, preserving heat at 105 ℃ and drying for 12 hours, transferring into a roasting furnace, heating to 530 ℃, preserving heat and roasting for 4 hours, naturally cooling, and grinding uniformly to obtain the modified hydrotalcite.
In the first liquid, the weight ratio of cerium nitrate hexahydrate, aluminum nitrate nonahydrate, zinc nitrate hexahydrate, magnesium nitrate hexahydrate and deionized water is 14.5:12.5:4:13:110.
In the second liquid, the weight ratio of sodium carbonate to sodium hydroxide to deionized water is 5.5:4.2:100.
5. Two-stage cooling and impurity removing
Feeding the first-stage impurity removal into a fifth micro-reactor of the micro-channel reaction device, controlling the temperature of the fifth micro-reactor to be 80 ℃, cooling, removing impurities, and discharging to obtain a second-stage impurity removal liquid.
Wherein, the fifth micro-reactor is filled with a mixture of mesoporous activated carbon and modified hydrotalcite, and the modified hydrotalcite is the same as the modified hydrotalcite adopted for primary cooling and impurity removal; the weight ratio of the mesoporous activated carbon to the modified hydrotalcite is 1:2; the loading of the mesoporous activated carbon and the modified hydrotalcite is 1.8 percent of the total weight of acetic acid fed in 1 hour in the preheating step.
In the secondary impurity removing liquid, the acetonitrile content is 56.6wt%, the impurity content is 0.09wt%, and the acetonitrile yield is 94.5%.
6. Rectifying
And (3) introducing the secondary impurity removing liquid into a buffer tank, and rectifying by adopting a continuous rectifying device to obtain the high-purity acetonitrile with the purity of more than 99.9%.
Wherein the rectification temperature is 100 ℃, and the rectification pressure is 0.2MPa.
Comparative example 1
The technical scheme of the embodiment 2 is adopted, and the difference is that: 1) In the preparation of the micro-reaction catalyst, the step of preparing an active matrix is omitted; the precursor prepared by the precursor preparation step is roasted for 5 hours at 580 ℃ to replace an active matrix and is used in the composite forming step; 2) In the steps of primary cooling and impurity removal and secondary cooling and impurity removal, the addition of the modified hydrotalcite is omitted, and mesoporous activated carbon is adopted to complement the weight parts of the modified hydrotalcite.
In the second-stage impurity removal liquid prepared in comparative example 1, the acetonitrile content was 51.4wt%, the impurity content was 0.32wt%, and the acetonitrile yield was 89.8%.
Comparative example 2
The technical scheme of the embodiment 2 is adopted, and the difference is that: 1) In the preparation of the micro-reaction catalyst, the composite molding step is modified as follows: putting the active matrix into a copper nitrate solution (with the mass concentration of 8 wt%) with the volume of 3.5 times, stirring and immersing for 6 hours, transferring into a roasting furnace, heating to 720 ℃ at the heating rate of 3.5 ℃/min, and carrying out heat preservation and roasting for 2.5 hours to obtain a reaction catalyst; 2) The first-stage cooling and impurity removing step is omitted.
In the second-stage impurity removal liquid prepared in comparative example 2, the acetonitrile content was 47.8wt%, the impurity content was 0.18wt%, and the acetonitrile yield was 85.6%.
The purity, moisture content, acidity, basicity, and evaporation residue of the high purity acetonitrile obtained in examples 1 to 3 were measured. The specific results are shown below:
further, the acetonitrile content and impurity content in the secondary impurity-removing solutions prepared in examples 1 to 3, comparative example 1 and comparative example 2 were detected and the acetonitrile yield was counted after 120 days of continuous preparation of the high-purity acetonitrile by the preparation methods of the high-purity acetonitrile in examples 1 to 3, comparative example 1 and comparative example 2, respectively. The specific results are shown below:
Further, the micro-reaction catalysts used in example 2, comparative example 1 and comparative example 2 were placed in an environment with a temperature of 28 ℃ and a relative humidity of 50%, and after standing and storage for 360 days, whether agglomeration or pulverization occurred in each micro-reaction catalyst was observed; and the preparation method of the high-purity acetonitrile in the embodiment 2 is adopted to prepare the high-purity acetonitrile, the acetonitrile content and the impurity content in the prepared secondary impurity removal liquid are respectively detected, and the acetonitrile yield is counted. The specific results are shown below:
It can be seen that in the preparation method of the high-purity acetonitrile, in the preheating step, the first micro-reactor of the micro-channel reaction device is adopted to carry out mixed preheating on acetic acid and ammonia; in the first stage reaction process, carrying out first-stage acetic acid ammoniation reaction in a second microreactor in the presence of a microreaction catalyst; in the second-stage reaction process, carrying out second-stage acetic acid ammoniation reaction in a third microreactor in the presence of a microreaction catalyst; then sequentially carrying out primary cooling impurity removal and secondary cooling impurity removal on the secondary reactant under the condition of mesoporous activated carbon and modified hydrotalcite, carrying out targeted adsorption on impurities generated in the ammonification reaction process of acetic acid, obtaining cooled secondary impurity removal liquid, and rectifying to obtain high-purity acetonitrile; in the process of generating acetonitrile by reacting acetic acid with ammonia gas, the generation of side reaction can be effectively inhibited, the impurity content in the prepared acetonitrile is reduced, the purity and yield of the acetonitrile are improved, the pressure and energy consumption of the subsequent refining process are reduced, the refining operation process is simplified, and the production efficiency is improved; meanwhile, in the preparation process of the micro-reaction catalyst, lanthanum nitrate, zirconium nitrate and glycine are adopted to prepare and obtain a precursor doped with lanthanum zirconate and carbon; then performing high-temperature ball milling on the precursor, cerium oxide and praseodymium oxide to further obtain cerium and praseodymium doped precursors (namely ball milling matters); mixing the ball-milled material with mesoporous activated carbon to prepare an active matrix; then compounding the active matrix with CuO/gamma-Al 2O3 to prepare a micro-reaction catalyst; the catalytic stability of the micro-reaction catalyst in the micro-channel reaction is improved pertinently, the problems of rapid activity decay and short overall catalytic life of the catalyst are effectively avoided, and the efficient, stable and continuous production of acetonitrile by micro-channel acetic acid ammoniation is realized; and the storage stability of the micro-reaction catalyst is improved, and the problems of caking, pulverization, reduced catalytic activity and the like of the micro-reaction catalyst in the long-term storage process are avoided. Furthermore, cerium/zinc elements are adopted for hydrotalcite modification to prepare modified hydrotalcite, and the modified hydrotalcite is matched with mesoporous activated carbon and is used for primary cooling impurity removal and secondary cooling impurity removal, and aiming at micro-channel reaction conditions and secondary reactant working conditions, impurities in the secondary reactant are subjected to targeted adsorption while the secondary reactant is cooled, so that the impurity content in acetonitrile synthesized materials is further reduced, and the efficient performance of subsequent refining procedures is facilitated.
As can be seen from comparative example 1, the step of preparing an active matrix is omitted in the preparation of the micro-reaction catalyst, and the catalytic performance of the micro-reaction catalyst is reduced to a certain extent, which is specifically represented by the reduction of the acetonitrile content and the yield in the secondary impurity removal liquid; meanwhile, the adding of the modified hydrotalcite is omitted in the steps of primary cooling impurity removal and secondary cooling impurity removal, impurities in the secondary reactant cannot be effectively adsorbed, and the impurities in the secondary impurity removal liquid cannot be controlled at a lower level. Further, the long-term catalytic performance of the micro-reaction catalyst is reduced to a certain extent, the overall catalytic life is shortened, and after 120 days of continuously preparing the high-purity acetonitrile, the acetonitrile content and the yield of the prepared secondary impurity-removing liquid are obviously reduced; and the micro-reaction catalyst has slight pulverization phenomenon after standing and storing for 360 days in an environment with the temperature of 28 ℃ and the relative humidity of 50%, and the micro-reaction catalyst is adopted for acetonitrile preparation, so that the catalytic activity is reduced, and the capability of inhibiting side reactions is reduced, and is particularly shown by the degradation of acetonitrile content, yield and impurity content indexes in secondary impurity removal liquid.
As can be seen from comparative example 2, the composite molding step is changed in the preparation of the micro-reaction catalyst, and the active matrix is not composited with gamma-Al 2O3, but directly adopts an impregnation method to load CuO; the catalytic performance of the prepared micro-reaction catalyst is obviously reduced, and the specific expression is that the acetonitrile content and the yield in the secondary impurity removal liquid are obviously reduced; meanwhile, after the primary cooling and impurity removing step is omitted, impurities in the secondary reactant cannot be effectively adsorbed while the temperature is effectively reduced. Further, the long-term catalytic performance of the micro-reaction catalyst is reduced to a certain extent, the overall catalytic life is shortened, and after 120 days of continuously preparing the high-purity acetonitrile, the acetonitrile content and the yield of the prepared secondary impurity-removing liquid are obviously reduced; and the micro-reaction catalyst has slight caking phenomenon after standing and storing for 360 days in an environment with the temperature of 28 ℃ and the relative humidity of 50%, and the micro-reaction catalyst is adopted for acetonitrile preparation, so that the catalytic activity is reduced, and the capability of inhibiting side reactions is reduced, and the micro-reaction catalyst is particularly characterized in that the deterioration of acetonitrile content, yield and impurity content indexes in secondary impurity removal liquid is realized.
The percentages used in the present invention are mass percentages unless otherwise indicated.
Finally, it should be noted that: the foregoing description is only a preferred embodiment of the present invention, and the present invention is not limited thereto, but it is to be understood that modifications and equivalents of some of the technical features described in the foregoing embodiments may be made by those skilled in the art, although the present invention has been described in detail with reference to the foregoing embodiments. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (8)

1. The preparation method of the high-purity acetonitrile is characterized by comprising the following steps of: preheating, primary reaction, secondary reaction, primary cooling and impurity removal, secondary cooling and impurity removal and rectification;
The preheating method comprises the steps of feeding acetic acid and ammonia gas into a first micro-reactor of a micro-channel reaction device, controlling the temperature of the first micro-reactor to be 140-150 ℃ and the residence time of materials in the first micro-reactor to be 100-120s to obtain a preheated material;
in the preheating, the molar ratio of acetic acid to ammonia is 1:1.2-1.3;
The primary reaction method comprises the steps of feeding preheated materials into a second micro-reactor of a micro-channel reaction device, controlling the temperature of the second micro-reactor to be 380-400 ℃, and controlling the residence time of the materials in the second micro-reactor to be 180-210s to obtain a primary reactant;
the second microreactor is filled with a microreaction catalyst; the loading amount of the micro-reaction catalyst in the second micro-reactor is 0.8-1% of the total feeding weight of acetic acid in 1h in the preheating step;
The preparation method of the micro-reaction catalyst comprises the following steps: preparing a precursor, preparing an active matrix and performing composite molding;
The method for preparing the precursor comprises the steps of putting lanthanum nitrate hexahydrate and zirconium nitrate pentahydrate into deionized water, dispersing uniformly, and stirring and putting glycine and citric acid; stirring and heating to 180-190 ℃, preserving heat, cooling to 50-60 ℃, preserving heat, regulating the pH value to 9-10, and filtering out solid matters; washing and roasting the solid by deionized water to obtain a precursor;
the method for preparing the active matrix comprises the steps of putting a precursor, cerium oxide and praseodymium oxide into a high-temperature ball mill, and performing heat preservation ball milling in an argon environment at a temperature of 550-600 ℃ to obtain a ball-milled product; uniformly mixing the ball-milling material with mesoporous activated carbon, and granulating to obtain an active matrix;
the composite molding method comprises the steps of putting isopropyl aluminum into deionized water, heating to 80-90 ℃, and preserving heat and stirring; continuously adding a nitric acid solution under the stirring condition, and carrying out heat preservation, reflux and stirring; continuously adding copper nitrate solution under stirring, and keeping the temperature at 60-70 ℃ for stirring to obtain sol solution; adding the active matrix into sol solution, uniformly dispersing, stirring, filtering out solid, and roasting to obtain a micro-reaction catalyst;
The method for the secondary reaction comprises the steps that a primary reactant is fed into a third micro-reactor of a micro-channel reaction device, the temperature of the third micro-reactor is controlled to be 300-330 ℃, and the retention time of materials in the third micro-reactor is 120-180s, so that a secondary reactant is obtained;
The third microreactor is filled with a microreaction catalyst which is the same as the microreaction catalyst in the primary reaction; the loading amount of the micro-reaction catalyst in the third micro-reactor is 0.8-1% of the total feeding weight of acetic acid in 1h in the preheating step;
The first-stage cooling and impurity removing method comprises the steps that a second-stage reactant is fed into a fourth micro-reactor of a micro-channel reaction device, the temperature of the fourth micro-reactor is controlled to be 85-90 ℃, and the residence time of materials in the fourth micro-reactor is controlled to be 420-480s, so that first-stage impurity removing is obtained;
the fourth micro-reactor is filled with a mixture of mesoporous activated carbon and modified hydrotalcite, and the weight ratio of the mesoporous activated carbon to the modified hydrotalcite is 1:1.8-2;
The loading amount of the mesoporous activated carbon and the modified hydrotalcite in the fourth micro-reactor is 1.5-1.6% of the total feeding weight of acetic acid in 1h in the preheating step;
The preparation method of the modified hydrotalcite comprises the steps of putting cerium nitrate hexahydrate, aluminum nitrate nonahydrate, zinc nitrate hexahydrate and magnesium nitrate hexahydrate into deionized water, and uniformly stirring to obtain a first liquid; under the stirring condition, sodium carbonate and sodium hydroxide are added into deionized water, and uniformly stirred to obtain a second liquid; dropwise adding the second liquid into the first liquid under the stirring condition until the pH value of the first liquid is 9.5-10.5, stopping dropwise adding the second liquid, continuing stirring, standing, and filtering out solid matters; washing, drying and roasting the solid by deionized water to obtain modified hydrotalcite;
The second-stage cooling impurity removal is carried out, the first-stage impurity removal is fed into a fifth micro-reactor of the micro-channel reaction device, the temperature of the fifth micro-reactor is controlled to be 75-80 ℃, the second-stage impurity removal is carried out, and the second-stage impurity removal liquid is obtained after discharging;
The fifth microreactor is filled with a mixture of mesoporous activated carbon and modified hydrotalcite, the modified hydrotalcite is the same as the modified hydrotalcite adopted for primary cooling and impurity removal, and the weight ratio of the mesoporous activated carbon to the modified hydrotalcite is 1:1.8-2;
The loading amount of the mesoporous activated carbon and the modified hydrotalcite in the fifth micro-reactor is 1.7-1.8% of the total feeding weight of acetic acid in 1h in the preheating step.
2. The method for preparing high-purity acetonitrile according to claim 1, wherein the rectification method is to rectify the secondary impurity-removing liquid by adopting a continuous rectification device to prepare the high-purity acetonitrile;
The rectification temperature of the rectification is 90-100 ℃, and the rectification pressure is 0.2-0.3MPa.
3. The method for preparing high purity acetonitrile according to claim 1, wherein in the preparation precursor, the heating rate to 180-190 ℃ is 3-3.5 ℃/min;
The roasting temperature is 350-400 ℃, the roasting temperature rising rate is 4-5 ℃/min, and the roasting time is 2-3h;
lanthanum nitrate hexahydrate, zirconium nitrate pentahydrate, glycine, citric acid and deionized water in a weight ratio of 173-217:172-215:15-22.5:19-28:1400-1500.
4. The method for preparing high-purity acetonitrile according to claim 1, wherein in the preparation of the active matrix, the ball milling time is 9-10 hours;
the weight ratio of the ball milling material to the mesoporous activated carbon is 1:0.5-0.6;
The weight ratio of the precursor, cerium oxide and praseodymium oxide is 50-55:4-5:1.5-2;
the particle size of the mesoporous activated carbon is 120-150 mu m, and the specific surface area is 1000-1100m 2/g.
5. The method for preparing high-purity acetonitrile according to claim 1, wherein in the composite molding, the feeding rate of isopropyl aluminum is 6-7g/min;
the concentration of the nitric acid solution is 1-1.1mol/L;
The concentration of the copper nitrate solution is 0.1-0.12mol/L;
The roasting temperature is 700-750 ℃, the roasting temperature rising rate is 3-4 ℃/min, and the roasting time is 2-3h.
6. The method for preparing high-purity acetonitrile according to claim 1, wherein in the composite molding, the weight ratio of isopropyl aluminum to deionized water is 1:1.8-2.2;
the weight ratio of the isopropyl aluminum to the nitric acid solution to the copper nitrate solution is 1:0.4-0.45:2.3-2.5;
the volume ratio of the active matrix to the sol solution is 0.25-0.3:1.
7. The method for preparing high purity acetonitrile according to claim 1, wherein in the primary cooling and impurity removal, the mesoporous activated carbon has a particle size of 150-200 μm, a specific surface area of 1100-1200m 2/g, an average pore diameter of 5-10nm, and a graphitization degree of 55-60%.
8. The method for preparing high-purity acetonitrile according to claim 1, wherein in the preparation of the modified hydrotalcite, the dropping rate of the second liquid is 20 to 25mL/min;
In the first liquid, the weight ratio of cerium nitrate hexahydrate to aluminum nitrate nonahydrate to zinc nitrate hexahydrate to magnesium nitrate hexahydrate to deionized water is 14-14.5:12-12.5:3.8-4:12.5-13:100-110;
in the second liquid, the weight ratio of the sodium carbonate to the sodium hydroxide to the deionized water is 5.3-5.5:4-4.2:100.
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