An adsorption tower and a device and method for preparing high-purity acetonitrile

Abstract

The present invention provides an adsorption tower and a preparation device and method for high-purity acetonitrile, wherein the tower body includes an inner ring and an outer ring separated by a partition ring wall, and the tower body is vertically separated into N layers, N≥3, and each layer is configured to prevent or allow gas phase and / or liquid phase to circulate between upper and lower layers as needed, and the outer ring of each layer is used to load different adsorbents, and the inner ring of each layer is provided with a stirring mechanism, and the partition ring wall is configured to be able to pass gas phase and / or liquid phase but not solid phase. The adsorption tower of the present invention can realize the function of multi-tower parallel connection by only a single tower, and it is convenient to disassemble and clean at the same time, with high adsorption efficiency and low fixed cost investment. The preparation method of the present invention has high reliability, high product yield and good quality, and its product purity can reach more than 99.99%, which can meet the needs of LC-MS grade acetonitrile reagents. At the same time, the production equipment of the present invention has good stability, is equipped with an adsorption tower of independent design, has high product yield and high quality, and can be semi-automatically operated.

Description

Technical Field

[0001] The invention relates to the field of organic chemical process refining, and in particular to an adsorption tower for refining and purifying industrial acetonitrile and a device and method for preparing high-purity acetonitrile. Background Art

[0002] Acetonitrile (CH3CN) is also called methyl nitrile, with a molecular weight of 41.05, a melting point of -42°C, a boiling point of 81.6°C, and a density of 0.7768 g / cm 3 It is a colorless liquid with an ethereal smell and is very volatile. Due to its high dielectric strength and dipole moment, it is an excellent solvent for inorganic and organic compounds, and its distribution ratio and desorption capacity are better than those of general alcohols. From the perspective of molecular structure, it has both a highly polar nitrile group and a non-polar methyl group, and can undergo alkylation, arylation, phthalation, addition, and intramolecular reactions, and occupies an important position in organic synthesis. The main uses of acetonitrile include use as an extraction agent in petrochemical production, as a raw material or solvent for the production of pharmaceuticals and pesticides, and as a solvent for high-performance liquid chromatography.

[0003] The production methods of acetonitrile can be mainly divided into two categories, direct synthesis and indirect methods. The direct synthesis method includes dozens of synthesis methods such as carbon monoxide ammonia hydrogenation method, methanol ammonia method, ethanol ammonia method, acetic acid ammonia method, acetaldehyde ammonia method, etc.; the indirect method is the propylene ammonia oxidation by-product method. Since acetonitrile is the main by-product in this method and its extraction method cost is relatively low, it is now the main source of industrial acetonitrile. At present, the main production capacity comes from the United States, Western Europe, Japan and China, etc. The purity of industrial acetonitrile produced by them is generally above 99.5%. In order to obtain high-purity acetonitrile that can meet the needs of semiconductor cleaning and as a solvent for various chromatographic and spectral analysis, further refining is required. The main impurities in industrial acetonitrile include water, hydrocyanic acid, acrylonitrile, oxazole, water, acrylic acid, propionitrile, butyronitrile, acetone, etc.

[0004] CN104058994B discloses a continuous preparation method and equipment for high-purity acetonitrile, which mainly uses aluminum oxide for adsorption, then uses potassium permanganate to oxidize small molecular impurities therein, and finally obtains high-purity acetonitrile through distillation. The potassium permanganate used in this method is difficult to clean after the reaction, and the subsequent processing cost is high. At the same time, the adsorption effect of only a single aluminum oxide is poor.

[0005] CN102746187A discloses a method for preparing a LC-MS grade high-purity acetonitrile reagent for liquid chromatography-mass spectrometry, which firstly processes the raw material acetonitrile through a variety of adsorbents for adsorption treatment, then oxidizes it in a reactor through sodium persulfate, potassium iodate or ozone, then performs rectification and dehydration treatment, and finally obtains the LC-MS grade high-purity acetonitrile reagent for liquid chromatography-mass spectrometry by filtering and nitrogen filling canning. The method has a complicated process and involves many steps. Only the adsorption process requires three parallel adsorption towers. At the same time, the reagents used, such as ozone and nitrogen, have high costs and low economic benefits.

[0006] CN105439903B discloses a method for preparing chromatographic acetonitrile by mainly using graphene oxide to adsorb impurities in industrial acetonitrile. The graphene oxide preparation method used in this method is complex and has high process requirements, which is not suitable for large-scale production. At the same time, the preparation method does not consider the problem of moisture introduced during the distillation process. Summary of the invention

[0007] In view of the problems existing in the above-mentioned prior art, the present invention provides a preparation process of high-purity acetonitrile and a production equipment thereof.

[0008] According to a first aspect of the present invention, the present invention provides an adsorption tower, wherein the tower body comprises an inner ring and an outer ring separated by a partition ring wall, and the tower body is divided into N layers in the vertical direction, N≥3, and each layer is configured to prevent or allow the gas phase and / or liquid phase to flow between the upper and lower layers as needed, the outer ring of each layer is used to load different adsorbents, the inner ring of each layer is provided with a stirring mechanism, and the partition ring wall is configured to allow the gas phase and / or liquid phase to pass but not the solid phase.

[0009] According to a second aspect of the present invention, the present invention provides a device for preparing high-purity acetonitrile, the device comprising: a reaction unit, an adsorption unit, a condensation unit, a buffer unit, a distillation unit, a drying unit, a post-cooling unit, a filtering unit and a storage unit connected in series in sequence along a material flow direction;

[0010] The adsorption unit at least comprises the adsorption tower of the present invention; the reaction unit is used to oxidize small molecular impurities in industrial acetonitrile into polar azeotropic impurities;

[0011] The oxidized material is distilled and gasified, and then passes through different adsorbent layers of the adsorption unit to adsorb polar azeotropic impurities, is condensed in the condensation unit, and is buffered in the buffer unit before entering the distillation unit for distillation. The acetonitrile produced in the distillation unit is dried in the drying unit, the dried material enters the post-cooling unit for condensation, and the condensed material enters the filtration unit for filtration to obtain high-purity acetonitrile, which is then sent to the storage unit for storage.

[0012] According to a third aspect of the present invention, the present invention provides a method for preparing high-purity acetonitrile, which is carried out in the device described in the present invention, and the method comprises:

[0013] a) subjecting industrial acetonitrile to alkali pre-treatment in a pre-treatment unit;

[0014] b) feeding the alkali-treated material of step a) into a reaction unit to oxidize small molecular impurities in industrial acetonitrile into polar azeotropic impurities;

[0015] c) distilling the oxidized material in step b) into a gaseous state and then sending it to an adsorption unit to adsorb polar azeotropic impurities, condensing it in a condensation unit, buffering it in a buffer unit, and then sending it to a distillation unit for distillation;

[0016] d) The acetonitrile produced by the distillation unit is dried in the drying unit, the dried material enters the post-cooling unit for condensation, the condensed material enters the filtering unit for filtration to obtain high-purity acetonitrile which is sent to the storage unit for storage.

[0017] The adsorption tower of the present invention has the advantages of high adsorption efficiency and low fixed asset investment. The adsorption tower of the present invention can realize the function of multiple towers in parallel with only a single tower, and is easy to disassemble and clean, has high adsorption efficiency and low fixed cost investment.

[0018] Compared with the adsorption tower used in general processes, the novel high-efficiency adsorption tower used in the device of the present invention can realize the function of multiple towers in parallel with a single tower, and is convenient to disassemble and clean, has high adsorption efficiency and low fixed cost investment.

[0019] The preparation device and method of high-purity acetonitrile of the present invention is a novel method for producing high-purity acetonitrile using industrial acetonitrile as raw material. According to a preferred embodiment of the present invention, a combination of a reactor, an adsorption tower, a distillation tower, a drying device and a microfiltration device of the present invention is used. The method preferably first adds an oxidizing alkali for pretreatment, and then reacts with an oxidant with good oxidizing properties under alkaline conditions in the reactor, which has a better oxidation and impurity removal effect than general industrial acetonitrile; after generating polar impurities with a higher boiling point, the present invention uses each adsorbent for adsorption, preferably adjusts the pH at the same time, and then uses distillation to separate the impurities again, extracts the middle fraction with the highest purity, and preferably removes moisture through a desiccant, and then obtains high-purity acetonitrile after filtration. The preparation method of the present invention has high reliability, high product yield, and good quality. The purity of the product can reach more than 99.99%, which can meet the needs of LC-MS grade acetonitrile reagents.

[0020] Meanwhile, the production equipment of the present invention has good stability, is equipped with a new type of high-efficiency adsorption tower designed independently, has high product yield and high quality, and can be semi-automatically operated.

[0021] In a preferred embodiment of the present invention, an alkaline environment is created by sodium peroxide, sodium superoxide, sodium carbonate, etc., and impurities are oxidized by using hydrogen peroxide, sodium hypochlorite, etc., which have good oxidizing properties in alkaline environments. The oxidation efficiency is high and no dirt that is difficult to clean is generated. At the same time, the method is equipped with a variety of adsorbents such as activated carbon fibers, humic acid, and cation exchange resins. Compared with activated carbon and activated alumina commonly used in general processes, not only can a wider range of impurities be adsorbed, but also, activated carbon fibers have high adsorption efficiency, humic acid is green and environmentally friendly without solid waste treatment, and cation exchange resins can neutralize the alkaline environment to facilitate subsequent distillation and drying. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 A flow chart of a method for preparing high-purity acetonitrile according to one embodiment of the present invention;

[0023] Figure 2 A schematic diagram of the device structure of a production device for high-purity acetonitrile according to an embodiment of the present invention;

[0024] Figure 3 A schematic structural diagram of an adsorption tower according to an embodiment of the present invention;

[0025] Figure 4 The figure is a schematic diagram of the tower structure of an adsorption tower according to an embodiment of the present invention.

[0026] Description of Reference Numerals

[0027] Figure 1 In the figure, a is industrial acetonitrile, b is the top logistics of the adsorption tower, c is the feed logistics of the intermittent distillation tower, d is the top logistics of the intermittent distillation tower, e is the top reflux logistics of the intermittent distillation tower, f is the top discharge logistics of the intermittent distillation tower, g is the side discharge of the intermittent distillation tower, and h is the finished product logistics after refining.

[0028] Figure 2 Among them, 101 is a reactor feed pump, 102 is a reactor, 103 is an adsorption tower, 104 is a front condenser, 105 is a buffer tank, 106 is a distillation tower feed pump, 107 is an intermittent distillation tower, 108 is a tower top condenser, 109 is a drying device, 110 is a post-condenser, 111 is a filter feed pump, 112 is a microfiltration device, and 113 is a finished product tank. DETAILED DESCRIPTION

[0029] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0030] The present invention provides an adsorption tower, wherein the tower body comprises an inner ring and an outer ring separated by a partition ring wall, and the tower body is divided into N layers in the vertical direction, N≥3, each layer is configured to prevent or allow gas phase and / or liquid phase to flow between the upper and lower layers as needed, the outer ring of each layer is used to load different adsorbents, the inner ring of each layer is provided with a stirring mechanism, and the partition ring wall is configured to allow gas phase and / or liquid phase to pass but not solid phase to pass. The adsorption tower of the present invention can realize the function of multi-tower parallel connection by only using a single tower, and is convenient to disassemble and clean, has high adsorption efficiency, and has low fixed cost investment.

[0031] According to a preferred embodiment of the present invention, valves are arranged between each layer, and the valves are provided with valve switches. The connection and disconnection of each layer are maintained by opening and closing the valve switches so that each layer can prevent or allow the gas phase and / or liquid phase to flow between the upper and lower layers as needed.

[0032] According to a preferred embodiment of the present invention, N is 3-5.

[0033] According to a preferred embodiment of the present invention, the inner ring diameter is 1 / 3-2 / 3 of the tower diameter.

[0034] According to a preferred embodiment of the present invention, the outer wall of the outer ring is an outer wall of the tower.

[0035] According to a preferred embodiment of the present invention, the ratio of tower height to tower diameter of the adsorption tower is 1.1-10:1.

[0036] According to a preferred embodiment of the present invention, the adsorption tower has a tower height of 1000-2500 mm and a tower diameter of 300-600 mm.

[0037] According to a preferred embodiment of the present invention, the outer wall of the outer ring of each layer is configured to be openable from the outside to enable the adsorbent to be stored or taken out.

[0038] According to a preferred embodiment of the present invention, the inner ring and / or the outer ring of each layer is configured to be freely detachable.

[0039] According to a preferred embodiment of the present invention, the separation ring wall is a stainless steel wall with holes.

[0040] The adsorption tower of the present invention can be applied to various adsorption fields, and is particularly suitable for being applied to an adsorption unit in an acetonitrile production device process.

[0041] According to the present invention, a device for preparing high-purity acetonitrile is provided, the device comprising: a reaction unit, an adsorption unit, a condensation unit, a buffer unit, a distillation unit, a drying unit, a post-cooling unit, a filtering unit and a storage unit which are sequentially connected in series along a material flow direction;

[0042] The adsorption unit at least comprises the adsorption tower of the present invention; the reaction unit is used to oxidize small molecular impurities in industrial acetonitrile into polar azeotropic impurities;

[0043] The oxidized material is distilled and gasified, and then passes through different adsorbent layers of the adsorption unit to adsorb polar azeotropic impurities, is condensed in the condensation unit, and is buffered in the buffer unit before entering the distillation unit for distillation. The acetonitrile produced in the distillation unit is dried in the drying unit, the dried material enters the post-cooling unit for condensation, and the condensed material enters the filtration unit for filtration to obtain high-purity acetonitrile, which is then sent to the storage unit for storage.

[0044] In the present invention, the buffer unit can be used to reduce the unevenness of the flow in the pipeline and reduce the pressure fluctuation in the system.

[0045] According to a preferred embodiment of the present invention, the device further comprises: a pre-treatment unit for subjecting industrial acetonitrile to alkaline pre-treatment before entering the reaction unit. By alkaline pre-treatment, a higher conversion rate of trace impurities can be achieved compared to direct oxidation reaction.

[0046] According to a preferred embodiment of the present invention, the condensing unit includes a pre-cooler; the buffer unit includes a buffer tank; the distillation unit includes an intermittent distillation tower; the drying unit includes a desiccant adsorption device, the after-cooling unit includes an after-cooler, the filtration unit includes a microfiltration device and the storage unit includes a finished product tank.

[0047] Each unit can be added with various pipelines or valves as well as components that may be needed in the industry as needed. The present invention has no special requirements for this and will not be described in detail here.

[0048] According to a preferred embodiment of the present invention, the device preferably includes: a reactor, an adsorption tower, a pre-cooler, a buffer tank, an intermittent distillation tower, a desiccant adsorption device, an after-cooler, a microfiltration device and a finished product tank which are sequentially connected in series along the material flow direction.

[0049] According to a preferred embodiment of the present invention, preferably, the side line of the intermittent distillation tower is connected to a desiccant adsorption device.

[0050] According to a preferred embodiment of the present invention, the filtration unit is a microfiltration device, and the microfiltration membrane is a polytetrafluoroethylene membrane, a polyacetate fiber membrane or a polystyrene membrane, and the pore size of the microfiltration membrane is preferably 1-10 nm.

[0051] According to a preferred embodiment of the present invention, the adsorption unit is formed on the top of the reaction unit.

[0052] According to a preferred embodiment of the present invention, the adsorption tower is preferably formed on the top of the reaction kettle.

[0053] According to a preferred embodiment of the present invention, a feed pump is installed at the front end outlet of the reactor, and the raw materials are fed into the reactor through the feed pump.

[0054] According to a preferred embodiment of the present invention, a pump is provided on the pipeline connecting the buffer tank and the intermittent distillation tower to deliver the liquid in the buffer tank into the intermittent distillation tower.

[0055] According to a preferred embodiment of the present invention, a reflux branch of a top condenser is provided at the top of the intermittent distillation tower, and a branch pipeline is used to collect distillate as a semi-finished product.

[0056] According to a preferred embodiment of the present invention, a pump is provided on the pipeline connecting the post-condenser and the microfiltration device to send the condensed liquid into the microfiltration device for filtration.

[0057] The present invention provides a method for preparing high-purity acetonitrile. The method is carried out in the device described in the present invention, and the method comprises:

[0058] a) subjecting industrial acetonitrile to alkali pre-treatment in a pre-treatment unit;

[0059] b) feeding the alkali-treated material of step a) into a reaction unit to oxidize small molecular impurities in industrial acetonitrile into polar azeotropic impurities;

[0060] c) distilling the oxidized material in step b) into a gaseous state and then sending it to an adsorption unit to adsorb polar azeotropic impurities, condensing it in a condensation unit, buffering it in a buffer unit, and then sending it to a distillation unit for distillation;

[0061] d) The acetonitrile produced by the distillation unit is dried in the drying unit, the dried material enters the post-cooling unit for condensation, the condensed material enters the filtering unit for filtration to obtain high-purity acetonitrile which is sent to the storage unit for storage.

[0062] According to a preferred embodiment of the present invention, in step a), the alkali used in the alkali pretreatment may be a common alkali, preferably one or more of sodium peroxide, sodium superoxide, sodium carbonate and copper hydroxide. This can improve the conversion rate of impurities in industrial acetonitrile during the oxidation reaction.

[0063] According to a preferred embodiment of the present invention, in step a), the amount of the base used is 0.4%-1% of the mass of industrial acetonitrile, thereby increasing the impurity conversion rate without causing excessive side reactions.

[0064] According to a preferred embodiment of the present invention, in step a), the conditions for the alkali treatment include: fully stirring and mixing industrial acetonitrile and alkali at 15-30° C. for 0.5-1 h.

[0065] According to a preferred embodiment of the present invention, in step b), the oxidant involved in the reaction is one or more of hydrogen peroxide, sodium hypochlorite and ruthenium tetroxide. Thus, no solid waste or solid residue is generated, which has the advantage of being green and environmentally friendly.

[0066] According to a preferred embodiment of the present invention, in step b), the amount of the oxidant used is 0.5%-1.5% of the mass of industrial acetonitrile, thereby allowing the impurities to react fully without causing excessive side reactions.

[0067] According to a preferred embodiment of the present invention, in step b), the oxidation conditions include: reaction pressure of 0.8-1.5 bar, reaction temperature of 75-85° C., reaction time of 1-3 h, and stirring rate of 120-240 r / min.

[0068] According to a preferred embodiment of the present invention, in step c), the adsorbent is selected from one or more of 5A molecular sieve, zeolite, activated carbon fiber, humic acid and cation exchange resin.

[0069] According to a preferred embodiment of the present invention, the pH of the acetonitrile leaving the adsorption unit is controlled between 6-8.

[0070] According to a preferred embodiment of the present invention, the adsorption conditions include: a temperature of 80-110° C., and a gas retention time of 0.5-1.5 h in each layer of the tower.

[0071] According to a preferred embodiment of the present invention, the operating conditions of the distillation unit include: a tower top pressure of 100-200 kPa, a tower top temperature of 70-80 ° C; a reflux ratio of 0.5-3, a tower top distillation rate of 10-30 ml / min, a side line acetonitrile extraction rate of 20-50 ml / min, and preferably, the side line extraction port is 20-50% of the total tower length from the tower top.

[0072] According to a preferred embodiment of the present invention, when the feed liquid in the bottom of the distillation tower drops to the initial 30-50% by volume, new material is added until it reaches 100% of the feed liquid, and a total reflux operation is performed for 1-4 hours after each addition of new material.

[0073] According to a preferred embodiment of the present invention, the drying unit uses a desiccant for drying, and the desiccant is selected from one or more of phosphorus pentoxide, silica gel, calcium chloride, magnesium sulfate and sodium sulfate.

[0074] According to a preferred embodiment of the present invention, the adsorption tower of the adsorption unit includes three layers, and each layer is filled with cation exchange resin from bottom to top; one or more of humic acid, zeolite, activated carbon fiber and 5A molecular sieve; one or more of activated carbon fiber, humic acid and zeolite; the dosage ratio of the adsorbent in each layer from bottom to top is 1-2:1-2:1-2.

[0075] According to a preferred embodiment of the present invention, the small molecule impurities include one or more of hydrocyanic acid, acrylonitrile, oxazole, water, acrylic acid, propionitrile, butyronitrile and acetone.

[0076] According to a preferred embodiment of the present invention, preferably, the desiccant used includes one or more of the following types: one or more of phosphorus pentoxide, silica gel, calcium chloride, magnesium sulfate and sodium sulfate.

[0077] The present invention provides high-purity acetonitrile prepared by the preparation method of the present invention. Preferably, the mass percentage of the high-purity acetonitrile is ≥99.95%, the water content is less than 300ppm, and meets the LC-MS grade.

[0078] According to a preferred embodiment of the method for preparing high-purity acetonitrile of the present invention, industrial acetonitrile is used as a raw material to produce a high-purity acetonitrile reagent that meets the LC-MS grade, comprising the following steps:

[0079] Step 1: pre-treat industrial acetonitrile with alkali, inject it into the oxidation reactor with a pump, stir it thoroughly to carry out the oxidation reaction, and oxidize the small molecular impurities (including acetone, hydrocyanic acid, oxazole, allyl alcohol, etc.) into polar azeotropic impurities.

[0080] Step 2: distilling the acetonitrile after the reaction, passing it through the novel high-efficiency adsorption tower of the present invention at a certain rate to adsorb the polar azeotropic impurities therein.

[0081] Step 3: Pass the adsorbed acetonitrile into an intermittent distillation tower, perform intermittent distillation at a certain vaporization rate, and extract acetonitrile from the side line.

[0082] Step 4: The extracted acetonitrile is subjected to desiccant water absorption and microfiltration operations to obtain high-purity acetonitrile.

[0083] According to a preferred embodiment of the method for preparing high-purity acetonitrile of the present invention, in the step 1, preferably, the alkali used for pretreatment is sodium peroxide, sodium superoxide, sodium carbonate, copper hydroxide, and the added mass is 0.4%-1% of the industrial acetonitrile; the oxidant participating in the oxidation reaction is hydrogen peroxide, sodium hypochlorite, ruthenium tetroxide, and the added mass is 0.5%-1.5% of the industrial acetonitrile.

[0084] According to a preferred embodiment of the method for preparing high-purity acetonitrile of the present invention, in the step 1, preferably, the process parameters of the oxidation reaction are: reaction pressure of 0.8-1.5 bar, reaction temperature of 75-85° C., reaction time of 1-3 h, and stirring rate of 120-240 r / min.

[0085] According to a preferred embodiment of the method for preparing high-purity acetonitrile of the present invention, in the step 2, preferably, the novel high-efficiency adsorption tower contains 3-5 adsorbents, and the types of adsorbents are 5A molecular sieve, zeolite, activated carbon fiber, humic acid and cation exchange resin. The pH of acetonitrile leaving the novel high-efficiency adsorption tower is controlled to be between 6 and 8 by online pH monitoring.

[0086] According to a preferred embodiment of the method for preparing high-purity acetonitrile of the present invention, in the step 2, preferably, the temperature of the new high-efficiency adsorption tower is controlled at 80-110°C, the retention time of the gas in each layer of the tower body is 0.5-1.5h, and the circulation of the gas is controlled by a valve.

[0087] According to a preferred embodiment of a method for preparing high-purity acetonitrile of the present invention, in the step 3, preferably, the process parameters of the intermittent distillation are: the tower top pressure is 100-200 kPa, the tower top temperature is 70-80°C; the reflux ratio is 0.5-3, the tower top distillation rate is controlled at 10-30 ml / min, and the side line extraction rate is 20-50 ml / min; when the feed liquid in the tower bottom drops to 30-50% of the initial, new material is added until it reaches 100% of the raw material liquid, and a total reflux operation is performed for 1-4 hours after each addition of new material.

[0088] According to a preferred embodiment of the method for preparing high-purity acetonitrile of the present invention, in the step three, the distillate obtained by distilling from the top of the tower is collected as a semi-finished product.

[0089] In the above technical solution, in step 4, preferably, the filter membrane of the microfiltration device used is a polytetrafluoroethylene filter membrane, a cellulose acetate filter membrane or a polystyrene filter membrane, and the pore size of the filter membrane is 1-10 nm.

[0090] In the above technical solution, in step 4, the high-purity acetonitrile obtained after the microfiltration operation will be collected in the finished product tank.

[0091] In the above technical solution, in the step 4, the mass percentage of high-purity acetonitrile obtained in the finished product tank is ≥99.95%, and the water content is less than 100 ppm.

[0092] In order to realize the above-mentioned preparation method of high-purity acetonitrile, the present invention also adopts a set of high-purity acetonitrile production equipment, including a reactor, a new high-efficiency adsorption tower, a buffer tank, an intermittent distillation tower, a drying device, a microfiltration device and a finished product tank.

[0093] Among them, the reactor and the new high-efficiency adsorption tower are integrated devices, the adsorption tower and the buffer tank are connected through a front condenser, the buffer tank is connected to the intermittent distillation tower, the top of the intermittent distillation tower is connected to a top condenser, the middle side line is connected to a drying device, the outlet of the drying device is connected to a rear condenser, the inlet of the microfiltration device is connected to the rear condenser, and the outlet is connected to the finished product tank.

[0094] According to the present invention, the new type of high-efficiency adsorption tower used is a three-layer detachable packing tower with a tower height of 1000-2500mm and a tower diameter of 300-600mm. The entire tower body structure is divided into three layers, each layer can be installed with different types of adsorbents, and assembled and disassembled separately. Each layer of the tower body is divided into two structures, an inner ring and an outer ring. The diameter of the inner ring is 1 / 3-2 / 3 of the tower diameter. The outer ring is used to store the adsorbent. The inner ring is equipped with a stirring paddle. The inner and outer rings are separated by a stainless steel wall with holes; the outer wall of the outer ring can be opened from the outside to facilitate the storage and removal of the adsorbent. There are twist-open and close valves on the upper and lower parts of the tower body to prevent or allow gas to flow between the upper and lower layers.

[0095] The present invention is further described below by way of examples and comparative examples, but the method of the present invention is not limited thereto.

[0096] The method of the present invention is further described below in conjunction with embodiments.

[0097] In the following examples, the industrial acetonitrile used has an acidity (in terms of acetic acid) of about 400-700 ppm, a moisture content of about 0.5-0.8%, a hydrocyanic acid content of about 200-400 ppm, an acetone content of about 150-200 ppm, an acrylonitrile content of about 100-300 ppm, a heavy component content of greater than 1000 ppm, and a purity of greater than 99%.

[0098] Figure 1 The present invention is a flowchart of a method for preparing high-purity acetonitrile according to one embodiment of the present invention.

[0099] Figure 2 The present invention is a schematic diagram of the device structure of a high-purity acetonitrile production device according to an embodiment of the present invention.

[0100] Figure 3 It is a schematic structural diagram of an adsorption tower according to an embodiment of the present invention.

[0101] Figure 4 The figure is a schematic diagram of the tower structure of an adsorption tower according to an embodiment of the present invention.

[0102] The following examples are based on Figure 1 and Figure 2 The process and device shown are carried out, and the method includes:

[0103] Industrial acetonitrile a enters the reactor 102 through the reactor feed pump 101 to undergo an oxidation reaction to oxidize small molecules of impurities. After distillation, the gaseous state enters the adsorption tower 103, and the adsorption tower overhead flow b is discharged from the top of the adsorption tower, and then enters the front condenser 104, and then enters the buffer tank 105. Subsequently, the intermittent distillation tower feed flow c is pumped into the intermittent distillation tower 107 through the distillation tower feed pump 106, and the intermittent distillation tower overhead flow d enters the top condenser 108. After that, the intermittent distillation tower overhead discharge flow f flows out, and the intermittent distillation tower overhead reflux flow e returns to the distillation tower. The intermittent distillation tower side line discharge g enters the drying device 109, and then enters the after-condenser 110. Subsequently, it enters the microfiltration device 112 through the filter feed pump 111 for filtration, and the refined finished product flow h enters the finished product tank 113.

[0104] The adsorption tower used in the following examples is as follows: Figure 3 and Figure 4 An adsorption tower, wherein the tower body comprises an inner ring and an outer ring separated by a partition ring wall, and the tower body is divided into three layers in the vertical direction, each layer is separated by a valve and a valve switch is arranged on the valve, the inner ring of each layer is provided with a stirring mechanism, and the outer ring of each layer is filled with different adsorbents, and the partition ring wall is arranged to be a stainless steel wall with holes.

[0105] Wherein, N is 3, the inner ring diameter is 2 / 3 of the tower diameter, the tower height to tower diameter ratio of the adsorption tower is 5:1, the tower height of the adsorption tower is 1500 mm, and the tower diameter is 300 mm. The adsorption tower is arranged above the reactor.

[0106] In the present invention, the cation exchange resin is, for example, 001×7 (732) strong acid styrene cation exchange resin, Amberlite IR120 or D001 macroporous strong acid styrene cation exchange resin, 5A molecular sieve (for example, trade name: Xiens 11113-61-4, Anaiji 69912-79-4 or McLean 69912-79-4), the zeolite is, for example, sulfonated polystyrene or sodium aluminosilicate, the activated carbon fiber is, for example, PAN-based fiber or phenolic-based fiber, and the humic acid is, for example, Aladdin 1415-93-6, McLean 1415-93-6 or Myrel 1415-93-6.

[0107] The following examples are used for exemplary purposes:

[0108] The cation exchange resin is 001×7 (732) strong acid styrene cation exchange resin, 5A molecular sieve (trade name: Xiens 11113-61-4), the zeolite is sodium aluminosilicate, the activated carbon fiber is PAN-based fiber, and the humic acid is Aladdin 1415-93-6 as an example to illustrate the advantages of the present invention.

[0109] Example 1

[0110] Use Figure 1 The process shown in the figure is to first add 1% of the mass fraction of acetonitrile sodium peroxide to industrial acetonitrile a (composition: 99.5% purity, acidity (in terms of acetic acid) of about 500ppm, moisture content of about 0.6%, hydrocyanic acid content of about 300ppm, acetone content of about 200ppm, acrylonitrile of about 200ppm, heavy component content greater than 1000ppm, and the rest of the embodiments are the same as the comparative examples) for alkali pretreatment (conditions include: fully stirring and mixing at 20°C for 1 hour), and then input it into the reactor through the raw material pump. The added oxidant is sodium hypochlorite, which is 1% of the mass of the raw material. The reaction pressure in the reactor is 1.2bar, the temperature is controlled at 80°C, the reaction time is 1.5h, the stirring rate is controlled at 140r / min, and the valve at the bottom of the adsorption tower is controlled to be closed during the reaction. The adsorbents installed in the three-layer tower body of the adsorption tower from bottom to top are cation exchange resin, 5A molecular sieve, and zeolite (the ratio of the three is 1:1:1). After the oxidation is completed, the bottom valve of the adsorption tower is opened, and the other valves are closed. The adsorption temperature is controlled at 92°C. After 1 hour of adsorption, the second valve is opened and the bottom valve is closed. The above operations are repeated in sequence until the gas completely passes through the adsorption tower. The pH of the gas is controlled between 6.5 and 7.5 by online pH monitoring. The gas is then condensed and buffered and sent to the intermittent distillation tower. At the beginning of distillation, the top temperature of the tower is controlled at 75°C, the pressure is 120kPa, and the full reflux operation is performed for 3 hours; then the reflux ratio is adjusted to 1.5, and the extraction rate of the top of the tower is 20ml / min. Then, side line extraction was started with an extraction rate of 40 ml / min, and the distance between the side line extraction port and the tower top was 30% of the total tower length; the gas extracted from the side line was then introduced into a drying device equipped with sodium sulfate, where the average residence time was 0.5 h. After drying and condensation, the gas was pumped into a microfiltration device, where a polystyrene filter membrane was used with a pore size of 5 nm. After filtration, the high-purity acetonitrile obtained was collected in a finished product tank (the results are shown in Table 1).

[0111] Example 2

[0112] Use Figure 1In the process shown, sodium superoxide with a mass fraction of 0.6% of acetonitrile is first added to industrial acetonitrile a for alkaline pretreatment (conditions include: fully stirring and mixing at 25°C for 0.5 hours), and then input into the reactor through the raw material pump. The added oxidant is sodium hypochlorite, with a mass of 1.5% of the raw material. The reaction pressure in the reactor is 0.8 bar, the temperature is controlled at 85°C, the reaction time is 3 hours, the stirring rate is controlled at 180r / min, and the bottom valve of the adsorption tower is controlled to be closed during the reaction. The adsorbents installed from bottom to top in the three-layer tower of the adsorption tower are cation exchange resin, activated carbon fiber, and humic acid (the ratio of the three is 2:1:1). After the oxidation is completed, the bottom valve of the adsorption tower is opened, and the other valves are in a closed state. The adsorption temperature is controlled at 95°C. After adsorption for 0.5 hours, the second valve is opened and the bottom valve is closed. The above operations are repeated in sequence until the gas completely passes through the adsorption tower, and the pH of the gas is controlled to be between 6 and 7 by online pH monitoring. The gas is then sent to the intermittent distillation tower after condensation and buffering. At the beginning of distillation, the tower top temperature is controlled at 80°C, the pressure is at 150kPa, and the full reflux operation is performed for 2h; then the reflux ratio is adjusted to 2, and the extraction rate of the tower top is 15ml / min. The side line extraction is started, and the extraction rate is 45ml / min. The distance between the side line extraction port and the tower top is 20% of the total tower length; then the gas extracted from the side line is passed into the drying device equipped with calcium chloride, and the average residence time in it is 1h. After drying and condensation, it is pumped into the microfiltration device. The filter membrane used is a polytetrafluoroethylene filter membrane with a pore size of 6nm. After filtration, the high-purity acetonitrile obtained is collected in a finished product tank (results are shown in Table 1).

[0113] Example 3

[0114] Use Figure 1In the process shown, 0.9% sodium percarbonate of the mass fraction of acetonitrile is first added to industrial acetonitrile a for alkali pretreatment (conditions include: fully stirring and mixing at 15°C for 0.8 hours), and then input into the reactor through the raw material pump. The added oxidant is ruthenium tetroxide, and the mass is 0.7% of the raw material. The reaction pressure in the reactor is 1.2 bar, the temperature is controlled at 76°C, the reaction time is 1.5 hours, the stirring rate is controlled at 200r / min, and the bottom valve of the adsorption tower is controlled to be closed during the reaction. The adsorbents installed in the three-layer tower of the adsorption tower from bottom to top are cation exchange resin, zeolite, and activated carbon fiber (the ratio of the three is 2:1:2). After the oxidation is completed, all valves of the adsorption tower except the top valve are opened, the adsorption temperature is controlled at 95°C, the total adsorption time is 1 hour, and the pH online monitoring controls the pH of the gas to be between 7-7.5. The gas is then condensed and buffered before being sent to an intermittent distillation tower. At the beginning of distillation, the tower top temperature is controlled at 76°C, the pressure is 140kPa, and the full reflux operation is performed for 2.5 hours. The reflux ratio is then adjusted to 1, and the extraction rate at the tower top is 25ml / min. The side line extraction is started at a rate of 25ml / min, and the distance between the side line extraction port and the tower top is 30% of the total tower length. The gas extracted from the side line is then passed into a drying device equipped with silica gel, where the average residence time is 1.5h. After drying and condensation, the gas is pumped into a microfiltration device. The filter membrane used is a polytetrafluoroethylene filter membrane with a pore size of 10nm. After filtration, the high-purity acetonitrile obtained is collected in a finished product tank (results are shown in Table 1).

[0115] Example 4

[0116] Use Figure 1In the process shown, 0.4% copper hydroxide of the mass fraction of acetonitrile is first added to industrial acetonitrile a for alkaline pretreatment (conditions include: fully stirring and mixing at 25°C for 1 hour), and then input into the reactor through the raw material pump. The added oxidant is hydrogen peroxide, which is 1.5% of the mass of the raw material. The reaction pressure in the reactor is 1 bar, the temperature is controlled at 75°C, the reaction time is 2.5 hours, the stirring rate is controlled at 120r / min, and the bottom valve of the adsorption tower is controlled to be closed during the reaction. The adsorbents installed from bottom to top in the three-layer tower of the adsorption tower are cation exchange resin, activated carbon fiber, and humic acid (the ratio of the three is 1:1:2). After the oxidation is completed, the bottom valve and the second valve of the adsorption tower are opened, and the other valves are closed. The adsorption temperature is controlled at 100°C. After adsorption for 0.75 hours, the third valve is opened and the other valves are closed. The above operations are repeated in sequence until the gas completely passes through the adsorption tower, and the pH of the gas is controlled to be between 6 and 7 by online pH monitoring. The gas is then condensed and buffered before being sent to an intermittent distillation tower. At the beginning of distillation, the tower top temperature is controlled at 70°C, the pressure is 120kPa, and the full reflux operation is performed for 2.5 hours; then the reflux ratio is adjusted to 0.75, and the extraction rate at the tower top is 25ml / min. The side line extraction is started, and the extraction rate is 50ml / min. The distance between the side line extraction port and the tower top is 45% of the total tower length; then the gas extracted from the side line is passed into a drying device equipped with magnesium sulfate, and the average residence time in it is 1.5h. After drying and condensation, it is pumped into a microfiltration device. The filter membrane used is a polyacetate fiber filter membrane with a pore size of 8nm. After filtration, the high-purity acetonitrile obtained is collected in a finished product tank (results are shown in Table 1).

[0117] Example 5

[0118] Use Figure 1In the process shown, sodium carbonate and sodium peroxide (the ratio of the two is 1:1) with a mass fraction of 0.8% of the total mass fraction of acetonitrile are first added to industrial acetonitrile a for alkaline pretreatment (conditions include: fully stirring and mixing at 15°C for 1 hour), and then input into the reactor through the raw material pump. The added oxidant is sodium hypochlorite with a mass of 1.2% of the raw material. The reaction pressure in the reactor is 1.4 bar, the temperature is controlled at 76°C, the reaction time is 2 hours, the stirring rate is controlled at 200r / min, and the bottom valve of the adsorption tower is controlled to be closed during the reaction. The adsorbents installed from bottom to top in the three-layer tower of the adsorption tower are cation exchange resin, humic acid, and activated carbon fiber (the ratio of the three is 1.5:2:1.5). After the oxidation is completed, the bottom valve of the adsorption tower is opened, and the other valves are in a closed state. The adsorption temperature is controlled at 83°C. After adsorption for 0.75 hours, the second valve is opened and the bottom valve is closed. The above operations are repeated in sequence until the gas completely passes through the adsorption tower, and the pH of the gas is controlled to be between 7 and 8 by online pH monitoring. The gas is then condensed and buffered before being sent to an intermittent distillation tower. At the beginning of distillation, the tower top temperature is controlled at 77°C, the pressure is 140kPa, and the full reflux operation is performed for 1h; then the reflux ratio is adjusted to 1.5, and the extraction rate at the tower top is 30ml / min. The side line extraction is started at a rate of 30ml / min, and the distance between the side line extraction port and the tower top is 50% of the total tower length; then the gas extracted from the side line is passed into a drying device equipped with sodium sulfate, and the average residence time in the drying device is 0.75h. After drying and condensation, it is pumped into a microfiltration device. The filter membrane used is a polytetrafluoroethylene filter membrane with a pore size of 5nm. After filtration, the high-purity acetonitrile obtained is collected in a finished product tank (results are shown in Table 1).

[0119] Example 6

[0120] Use Figure 1In the process shown, sodium peroxide and sodium superoxide (the ratio of the two is 1:2) with a total mass fraction of 0.8% of acetonitrile are first added to industrial acetonitrile a for alkaline pretreatment (conditions include: fully stirring and mixing at 25°C for 0.75 hours), and then input into the reactor through the raw material pump. The added oxidant is hydrogen peroxide with a mass of 0.9% of the raw material. The reaction pressure in the reactor is 1 bar, the temperature is controlled at 83°C, the reaction time is 3 hours, the stirring rate is controlled at 130r / min, and the bottom valve of the adsorption tower is controlled to be closed during the reaction. The adsorbents installed from bottom to top in the three-layer tower of the adsorption tower are cation exchange resin, humic acid, and activated carbon fiber (the ratio of the three is 1.5:2:1). After the oxidation is completed, the bottom valve of the adsorption tower is opened, and the other valves are in a closed state. The adsorption temperature is controlled at 100°C. After adsorption for 1.2 hours, the second valve is opened and the bottom valve is closed. The above operations are repeated in sequence until the gas completely passes through the adsorption tower, and the pH of the gas passing through the online pH monitoring is controlled to be between 6.5 and 8. The gas is then condensed and buffered before being sent to an intermittent distillation tower. At the beginning of distillation, the tower top temperature is controlled at 78°C, the pressure is 150kPa, and the full reflux operation is performed for 2 hours; then the reflux ratio is adjusted to 2, and the extraction rate at the tower top is 10ml / min. The side line extraction is started, and the extraction rate is 40ml / min. The distance between the side line extraction port and the tower top is 35% of the total tower length; then the gas extracted from the side line is passed into a drying device equipped with phosphorus pentoxide, and the average residence time in it is 0.5h. After drying and condensation, it is pumped into a microfiltration device. The filter membrane used is a polytetrafluoroethylene filter membrane with a pore size of 4nm. After filtration, the high-purity acetonitrile obtained is collected in a finished product tank (results are shown in Table 1).

[0121] Comparative Example 1

[0122] Use Figure 1In the process shown, without adding alkali for pretreatment, the acetonitrile raw material a is directly pumped into the reactor, and the added oxidant is sodium hypochlorite, which is 1% of the raw material. The reaction pressure in the reactor is 1.2 bar, the temperature is controlled at 80°C, the reaction time is 1.5 hours, the stirring rate is controlled at 140r / min, and the bottom valve of the adsorption tower is controlled to be closed during the reaction. The adsorbents installed from bottom to top in the three-layer tower of the adsorption tower are cation exchange resin, 5A molecular sieve, and zeolite (the ratio of the three is 1:1:1). After the oxidation is completed, the bottom valve and the second valve of the adsorption tower are opened, and the other valves are closed. The adsorption temperature is controlled at 92°C. After adsorption for 1 hour, the third valve is opened and the other valves are closed. The above operations are repeated in sequence until the gas passes through the adsorption tower completely. The pH online monitoring controls the pH of the gas to be between 6.5 and 7.5. The gas is then condensed and sent to an intermittent distillation tower. At the beginning of distillation, the tower top temperature is controlled at 75°C, the pressure is 120kPa, and the full reflux operation is performed for 3 hours; then the reflux ratio is adjusted to 1.5, and the extraction rate of the tower top is 20ml / min. The side line extraction is started, and the extraction rate is 40ml / min. The distance between the side line extraction port and the tower top is 30% of the total tower length; then the gas extracted from the side line is passed into a drying device equipped with sodium sulfate, and the average residence time in it is 0.5h. After drying and condensation, it is pumped into a microfiltration device. The filter membrane used is a polystyrene filter membrane with a pore size of 5nm. After filtration, the acetonitrile obtained is collected in a finished product tank (results are shown in Table 2).

[0123] Comparative Example 2

[0124] Use Figure 1The process shown is that the adsorption tower of the present invention is replaced by three common adsorption towers in parallel. First, sodium peroxide of 1% of the total mass fraction of acetonitrile is added to industrial acetonitrile a for pretreatment (conditions include: fully stirring and mixing at 20°C for 1 hour), and then input into the reactor through the raw material pump. The added oxidant is sodium hypochlorite, and the mass is 1% of the raw material. The reaction pressure in the reactor is 1.2 bar, the temperature is controlled at 80°C, the reaction time is 1.5 hours, and the stirring rate is controlled at 140r / min. The three adsorption towers are respectively filled with cation exchange resin, 5A molecular sieve, and zeolite (the ratio of the three is 1:1:1). After the oxidation is completed, the bottom valve and the second valve of the adsorption tower are opened, and the other valves are in a closed state. The adsorption temperature is controlled at 92°C. After adsorption for 1 hour, the third valve is opened and the other valves are closed. The above operations are repeated in sequence until the gas completely passes through the adsorption tower, and the pH of the gas is controlled to be between 6.5 and 7.5 by online pH monitoring. The gas is then condensed and sent to an intermittent distillation tower. At the beginning of distillation, the tower top temperature is controlled at 75°C, the pressure is 120kPa, and the full reflux operation is performed for 3 hours; then the reflux ratio is adjusted to 1.5, and the extraction rate of the tower top is 20ml / min. The side line extraction is started, and the extraction rate is 40ml / min. The distance between the side line extraction port and the tower top is 30% of the total tower length; then the gas extracted from the side line is passed into a drying device equipped with sodium sulfate, and the average residence time in it is 0.5h. After drying and condensation, it is pumped into a microfiltration device. The filter membrane used is a polystyrene filter membrane with a pore size of 5nm. After filtration, the acetonitrile obtained is collected in a finished product tank (results are shown in Table 2).

[0125] Example 7

[0126] Compared with Example 1, the oxidant used is commonly used potassium permanganate.

[0127] Use Figure 1In the process shown, sodium peroxide of 1% of the total mass fraction of acetonitrile is first added to industrial acetonitrile a for pretreatment (conditions include: fully stirring and mixing at 20°C for 1 hour), and then input into the reactor through the raw material pump. The added oxidant is potassium permanganate commonly used in other processes, with a mass of 1% of the raw material. The reaction pressure in the reactor is 1.2 bar, the temperature is controlled at 80°C, the reaction time is 1.5 hours, and the stirring rate is controlled at 140r / min. The three adsorption towers are respectively filled with cation exchange resin, 5A molecular sieve, and zeolite (the ratio of the three is 1:1:1). After the oxidation is completed, the bottom valve and the second valve of the adsorption tower are opened, and the other valves are closed. The adsorption temperature is controlled at 92°C. After adsorption for 1 hour, the third valve is opened and the other valves are closed. The above operations are repeated in sequence until the gas completely passes through the adsorption tower. The pH online monitoring controls the pH of the gas to be between 6.5 and 7.5. The gas is then condensed and sent to an intermittent distillation tower. At the beginning of distillation, the tower top temperature is controlled at 75°C, the pressure is 120kPa, and the full reflux operation is performed for 3 hours; then the reflux ratio is adjusted to 1.5, and the extraction rate of the tower top is 20ml / min. The side line extraction is started, and the extraction rate is 40ml / min. The distance between the side line extraction port and the tower top is 30% of the total tower length; then the gas extracted from the side line is passed into a drying device equipped with sodium sulfate, and the average residence time in it is 0.5h. After drying and condensation, it is pumped into a microfiltration device. The filter membrane used is a polystyrene filter membrane with a pore size of 5nm. After filtration, the acetonitrile obtained is collected in a finished product tank (results are shown in Table 2).

[0128] Example 8

[0129] Compared with Example 1, no side line extraction is performed in the intermittent distillation tower.

[0130] Use Figure 1In the process shown, sodium peroxide of 1% of the total mass fraction of acetonitrile is first added to industrial acetonitrile a for pretreatment (conditions include: fully stirring and mixing at 20°C for 1 hour), and then input into the reactor through the raw material pump. The added oxidant is sodium hypochlorite, with a mass of 1% of the raw material. The reaction pressure in the reactor is 1.2 bar, the temperature is controlled at 80°C, the reaction time is 1.5 hours, and the stirring rate is controlled at 140r / min. The three adsorption towers are respectively filled with cation exchange resin, 5A molecular sieve, and zeolite (the ratio of the three is 1:1:1). After the oxidation is completed, the bottom valve and the second valve of the adsorption tower are opened, and the other valves are closed. The adsorption temperature is controlled at 92°C. After adsorption for 1 hour, the third valve is opened and the other valves are closed. The above operations are repeated in sequence until the gas completely passes through the adsorption tower. The pH online monitoring controls the pH of the gas to be between 6.5 and 7.5. The gas is then condensed and sent to an intermittent distillation tower. At the beginning of the distillation, the tower top temperature is controlled at 75°C, the pressure is 120 kPa, and the full reflux operation is performed for 3 hours; then the reflux ratio is adjusted to 1.5, and the gas is directly produced from the tower top without side line production, and the production rate is 20 ml / min; the gas produced from the tower top is passed into a drying device equipped with sodium sulfate, and the average residence time therein is 0.5 h. After drying and condensation, it is pumped into a microfiltration device. The filter membrane used is a polystyrene filter membrane with a pore size of 5 nm. After filtration, the acetonitrile obtained is collected in a finished product tank (the results are shown in Table 2).

[0131] Example 9

[0132] Compared with Example 1, the gas finally produced is not dried by a desiccant and is directly subjected to microfiltration operation.

[0133] Use Figure 1In the process shown, sodium peroxide of 1% of the total mass fraction of acetonitrile is first added to industrial acetonitrile a for pretreatment (conditions include: fully stirring and mixing at 20°C for 1 hour), and then input into the reactor through the raw material pump. The added oxidant is sodium hypochlorite, with a mass of 1% of the raw material. The reaction pressure in the reactor is 1.2 bar, the temperature is controlled at 80°C, the reaction time is 1.5 hours, and the stirring rate is controlled at 140r / min. The three adsorption towers are respectively filled with cation exchange resin, 5A molecular sieve, and zeolite (the ratio of the three is 1:1:1). After the oxidation is completed, the bottom valve and the second valve of the adsorption tower are opened, and the other valves are closed. The adsorption temperature is controlled at 92°C. After adsorption for 1 hour, the third valve is opened and the other valves are closed. The above operations are repeated in sequence until the gas completely passes through the adsorption tower. The pH online monitoring controls the pH of the gas to be between 6.5 and 7.5. The gas was then condensed and sent to an intermittent distillation tower. At the beginning of the distillation, the tower top temperature was controlled at 75°C, the pressure was 120kPa, and the full reflux operation was performed for 3 hours. The reflux ratio was then adjusted to 1.5, and the extraction rate at the tower top was 20ml / min. The side line extraction was started at a rate of 40ml / min, and the distance between the side line extraction port and the tower top was 30% of the total tower length. The gas extracted from the side line was then directly condensed and pumped into a microfiltration device without drying. The filter membrane used was a polystyrene filter membrane with a pore size of 5nm. After the filtration was completed, the acetonitrile obtained was collected in a finished product tank (results are shown in Table 2).

[0134] Example 10

[0135] Compared with Example 1, the gas finally produced is not subjected to microfiltration operation.

[0136] Use Figure 1In the process shown, sodium peroxide of 1% of the mass fraction of acetonitrile is first added to industrial acetonitrile a for alkaline pretreatment (conditions include: fully stirring and mixing at 20°C for 1 hour), and then input into the reactor through the raw material pump. The added oxidant is sodium hypochlorite, with a mass of 1% of the raw material. The reaction pressure in the reactor is 1.2 bar, the temperature is controlled at 80°C, the reaction time is 1.5 hours, the stirring rate is controlled at 140r / min, and the bottom valve of the adsorption tower is controlled to be closed during the reaction. The adsorbents installed from bottom to top in the three-layer tower of the adsorption tower are cation exchange resin, 5A molecular sieve, and zeolite (the ratio of the three is 1:1:1). After the oxidation is completed, the bottom valve of the adsorption tower is opened, and the other valves are in a closed state. The adsorption temperature is controlled at 92°C. After adsorption for 1 hour, the second valve is opened and the bottom valve is closed. The above operations are repeated in sequence until the gas completely passes through the adsorption tower, and the pH of the gas passing through the online pH monitoring is controlled to be between 6.5 and 7.5. The gas was then condensed and sent to an intermittent distillation tower. At the beginning of distillation, the tower top temperature was controlled at 75°C, the pressure was 120kPa, and the full reflux operation was performed for 3 hours. The reflux ratio was then adjusted to 1.5, and the extraction rate at the tower top was 20ml / min. The side line extraction was started at a rate of 40ml / min, and the distance between the side line extraction port and the tower top was 30% of the total tower length. The gas extracted from the side line was then passed into a drying device equipped with sodium sulfate, and the average residence time therein was 0.5h. After drying, the gas was condensed and directly sent to a finished product tank to collect the obtained acetonitrile (results are shown in Table 2).

[0137] Table 1

[0138]

[0139] Table 2

[0140]

[0141] According to the comparison of the results of Example 1 in Table 1 with the results of Comparative Example 1 in Table 2, it can be found that the alkali treatment of industrial acetonitrile before the oxidation reaction can effectively improve the index data of the final product compared with no treatment, which proves that the present invention has obvious technical advantages.

[0142] According to the comparison of the results of Example 1 in Table 1 and the results of Comparative Example 2 in Table 2, it can be found that the index data of the final product obtained by using three parallel adsorption towers and the final product obtained by the new high-efficiency adsorption tower adopted in the present invention are basically the same, which proves that the new high-efficiency adsorption tower adopted in the present invention can achieve a technical effect similar to that of three parallel adsorption towers, and its fixed asset investment cost is lower, which proves that the present invention has technical advantages.

[0143] According to the comparison of the results of Example 1 in Table 1 with the results of Example 7 in Table 2, it can be found that the oxidant used in the present invention has higher indicators than the potassium permanganate catalyst commonly used in other technologies for the final acetonitrile product, indicating that the oxidant preferably used in the present invention has a better oxidation effect, proving that the present invention has a technical advantage.

[0144] According to the comparison between the results of Example 1 in Table 1 and the results of Example 8 in Table 2, it can be found that the various indicators of the final product of the intermittent distillation tower using side line extraction are improved compared with not using side line extraction, which proves that the preferred technical solution adopted in the present invention has technical advantages.

[0145] According to the comparison of the results of Example 1 in Table 1 with the results of Example 9 in Table 2, it can be found that the moisture content of the final product is greatly reduced when the desiccant is used compared with no drying, which proves that the preferred technical solution adopted in the present invention has technical advantages.

[0146] According to the comparison between the results of Example 1 in Table 1 and the results of Example 10 in Table 2, it can be found that the various indicators of the final product are improved by using microfiltration operation compared with not using microfiltration operation, which proves that the preferred technical solution adopted in the present invention has technical advantages.

[0147] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A device for preparing high-purity acetonitrile, characterized in that, The device comprises: a reaction unit, an adsorption unit, a condensation unit, a buffer unit, a distillation unit, a drying unit, a post-cooling unit, a filtering unit and a storage unit which are sequentially connected in series along the material flow direction; The reaction unit is used to oxidize small molecular impurities in industrial acetonitrile into polar azeotropic impurities; The oxidized material is distilled and gasified, and then passes through different adsorbent layers of the adsorption unit to adsorb polar azeotropic impurities, is condensed in the condensation unit, is buffered in the buffer unit, and then enters the distillation unit for distillation. The acetonitrile produced by the distillation unit is dried in the drying unit, the dried material enters the post-cooling unit for condensation, and the condensed material enters the filtration unit for filtration to obtain high-purity acetonitrile, which is then sent to the storage unit for storage; The adsorption unit comprises an adsorption tower, the tower body of the adsorption tower comprises an inner ring and an outer ring separated by a partition ring wall, and the tower body is divided into N layers in the vertical direction, N≥3, each layer is configured to prevent or allow gas phase and / or liquid phase to flow between the upper and lower layers as needed, the outer ring of each layer is used to fill different adsorbents, the inner ring of each layer is provided with a stirring mechanism, and the partition ring wall is configured to allow gas phase and / or liquid phase to pass but not solid phase to pass; valves are arranged between each layer, and the valves are provided with valve switches, and the connection and disconnection of each layer are maintained by opening and closing the valve switches so that each layer can prevent or allow gas phase and / or liquid phase to flow between the upper and lower layers as needed; and / or Said N is 3-5; and / or The inner ring diameter is 1 / 3-2 / 3 of the tower diameter; and / or The outer wall of the outer ring is the outer wall of the tower; and / or The ratio of the tower height to the tower diameter of the adsorption tower is 1.1-10:1; and / or The adsorption tower has a height of 1000-2500 mm and a diameter of 300-600 mm; and / or The outer wall of the outer ring of each layer is configured to be openable from the outside to store or remove the adsorbent; and / or The inner ring and / or outer ring of each layer is configured to be freely removable; and / or The separation ring wall is a stainless steel wall with holes.

2. The preparation device according to claim 1, wherein: The device further comprises: a pre-treatment unit, used for subjecting industrial acetonitrile to alkali pre-treatment before entering the reaction unit; and / or The condensing unit includes a pre-cooler; the buffer unit includes a buffer tank; the distillation unit includes an intermittent distillation tower; the drying unit includes a desiccant adsorption device; the after-cooling unit includes an after-cooler; the filtering unit includes a microfiltration device; and the storage unit includes a finished product tank.

3. The preparation device according to claim 2, wherein: The device comprises: a reaction kettle, an adsorption tower, a front cooler, a buffer tank, an intermittent distillation tower, a desiccant adsorption device, an aftercooler, a microfiltration device and a finished product tank which are connected in series in sequence along the material flow direction.

4. The preparation device according to claim 3, wherein: The side line of the intermittent distillation tower is connected to a desiccant adsorption device; The filtration unit is a microfiltration device, and the microfiltration membrane is a polytetrafluoroethylene filter membrane, a polyacetate fiber filter membrane or a polystyrene filter membrane.

5. The preparation device according to claim 4, wherein: The pore size of the microfiltration membrane is 1-10nm.

6. The preparation device according to claim 1, wherein: The adsorption unit is formed on the top of the reaction unit.

7. The preparation device according to claim 6, wherein: The adsorption tower is formed on the top of the reactor.

8. A method for preparing high-purity acetonitrile, characterized in that: The method is carried out in the device according to any one of claims 1 to 7, and the method comprises: a) subjecting industrial acetonitrile to alkaline pretreatment in a pretreatment unit; b) feeding the alkali-treated material of step a) into a reaction unit to oxidize small molecular impurities in industrial acetonitrile into polar azeotropic impurities; c) distilling the oxidized material in step b) into a gaseous state and then sending it to an adsorption unit to adsorb polar azeotropic impurities, condensing it in a condensation unit, buffering it in a buffer unit, and then sending it to a distillation unit for distillation; d) The acetonitrile produced by the distillation unit is dried in the drying unit, the dried material enters the post-cooling unit for condensation, the condensed material enters the filtration unit for filtration to obtain high-purity acetonitrile which is sent to the storage unit for storage.

9. The preparation method according to claim 8, wherein: In step a), The alkali for the alkali pretreatment is one or more of sodium peroxide, sodium superoxide, sodium carbonate and copper hydroxide, and the amount of the alkali is 0.4%-1% of the mass of industrial acetonitrile; and / or The conditions for the alkali pretreatment include: fully stirring and mixing industrial acetonitrile and alkali at 15-30° C. for 0.5-1 h; In step b), The oxidant involved in the reaction is one or more of hydrogen peroxide, sodium hypochlorite and ruthenium tetroxide, and the amount of the oxidant is 0.5%-1.5% of the mass of industrial acetonitrile; and / or The oxidation conditions include: reaction pressure of 0.8-1.5 bar, reaction temperature of 75-85° C., reaction time of 1-3 h, stirring rate of 120-240 r / min; and / or In step c), the adsorbent is selected from one or more of 5A molecular sieve, zeolite, activated carbon fiber, humic acid and cation exchange resin; and / or Controlling the pH of the acetonitrile leaving the adsorption unit to between 6 and 8; and / or The adsorption conditions include: temperature of 80-110°C, gas retention time in each tower layer of 0.5-1.5h; and / or The operating conditions of the distillation unit include: the tower top pressure is 100-200 kPa, the tower top temperature is 70-80°C; the reflux ratio is 0.5-3, the tower top distillation rate is controlled at 10-30 ml / min, and the side line acetonitrile extraction rate is 20-50 ml / min; The drying unit uses a desiccant for drying, and the desiccant is selected from one or more of phosphorus pentoxide, silica gel, calcium chloride, magnesium sulfate and sodium sulfate.

10. The preparation method according to claim 9, wherein: The operating conditions of the distillation unit include: the side line outlet is located 20-50% of the total tower length from the tower top.

11. The preparation method according to claim 9, wherein: When the liquid in the bottom of the distillation tower drops to 30-50% of the initial volume, start adding new material until it reaches 100% of the raw material liquid. After each addition of new material, perform full reflux operation for 1-4 hours.

12. The preparation method according to claim 8, wherein: The adsorption tower of the adsorption unit includes three layers, and each layer is filled with cation exchange resin from bottom to top; one or more of humic acid, zeolite, activated carbon fiber and 5A molecular sieve; one or more of activated carbon fiber, humic acid and zeolite; the dosage ratio of the adsorbent in each layer from bottom to top is 1-2:1-2:1-2.

13. The preparation method according to any one of claims 8 to 12, wherein: The small molecule impurities include one or more of hydrocyanic acid, acrylonitrile, oxazole, water, acrylic acid, propionitrile, butyronitrile and acetone.

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