An electronic-grade pyridine separation and purification method

Abstract

The present invention relates to the field of purification of electronic chemicals, and particularly to a method for separating and purifying electronic-grade pyridine, comprising the following steps: (S.1) adding an alcoholate to industrial-grade pyridine and carrying out a reflux reaction so that the water in the industrial-grade pyridine reacts with sodium alkoxide; (S.2) continuously adding the said impurity removal reagent to the system and carrying out a reflux reaction so that the alkylpyridine in the industrial-grade pyridine couples with the impurity removal reagent; (S.3) filtering to remove the impurity removal reagent; (S.4) carrying out rectification to obtain electronic-grade pyridine. The purification method in the present invention can effectively remove pyridine homologues, amine compounds and moisture doped in crude pyridine. After purification, the purity of pyridine can be increased to above 4N grade. At the same time, this purification method in the present invention also has the effects of simple steps and low cost, which is conducive to large-scale industrial application.

Description

Technical Field

[0001] The present invention relates to the field of purification of electronic chemicals, and particularly to a method for separating and purifying electronic-grade pyridine. Background Art

[0002] In the semiconductor field, currently, the SOD (Spin On Dielecterics) process is used to replace the original CVD (Chemical Vapor Deposition) process, and polysilazane is required as a filling material in the SOD process. During the production process of polysilazane, pyridine can be used as a catalyst, thereby effectively reducing the reaction temperature.

[0003] Pyridine is a six-membered heterocyclic compound containing one nitrogen heteroatom, which can be regarded as a compound in which one (CH) in the benzene molecule is replaced by N, so it is also called azobenzene. It can be obtained from natural coal tar or prepared from acetaldehyde and ammonia. In industrial production, pyridine mostly adopts the aldehyde-ammonia method. This method uses molecular sieve as a catalyst, and formaldehyde or acetaldehyde and ammonia as raw materials, and undergoes a gas-phase condensation reaction at high temperature to produce pyridine. However, the by-products of pyridine prepared by this reaction are relatively complex, mainly including methylpyridine, methylamine, polyalkylpyridine and water, etc. After introducing these impurities into polysilazane, they will absorb UV at 315 nm, resulting in a decrease in the yield of electronic materials and various other adverse effects. Therefore, it is urgent to provide a method for separating and purifying electronic-grade pyridine.

[0004] Chinese Patent CN109912500A discloses a method and device for refining crude pyridine into high-purity pyridine series products. Azeotropic distillation, atmospheric and vacuum distillation and heat integration technology are used to separate pyridine, o-methylpyridine, dimethylpyridine, trimethylpyridine and other series products. The purity of the pyridine product is 99.8 wt%, which does not meet the requirements of high-purity pyridine. In addition, the method described in this patent is a multi-step distillation method with high energy consumption and high product cost.

[0005] Chinese Patent CN101337923B discloses a method for purifying crude pyridine. The crude pyridine is vaporized and mixed with air in a molar ratio of 1:50-150, and reacted through an oxidation catalyst at a gas hourly space velocity of 300-1000 h-1 at 250-400 °C. After the reaction, it is distilled, and the fraction at 115.5 °C is collected at atmospheric pressure to obtain high-purity pyridine with a purity of 99.9 wt%. This method requires a high-temperature oxidation reaction above 250 °C, which is a reaction separation and purification method with high energy consumption. -1 The present invention relates to the field of purification of electronic chemicals, and particularly to a method for separating and purifying electronic-grade pyridine. Summary of the Invention

[0006] The present invention aims to overcome the defects in the prior art that the operation in the purification process of pyridine is complex, the purification purity is low, and the energy consumption is high, and provides a method for separating and purifying electronic-grade pyridine to overcome the above defects.

[0007] To achieve the above-mentioned invention purpose, the present invention is realized through the following technical solutions:

[0008] In the first aspect, the present invention provides an impurity removal reagent for purifying pyridine

[0009] The impurity removal reagent contains inorganic particles;

[0010] and a cross-linked polymer coating wrapped outside the inorganic particles;

[0011] The polymer coating contains a chain segment with an aldehyde group.

[0012] As described in the background art, the impurities in crude pyridine often include water, ammonia, and pyridine homologues containing alkyl groups. Among them, these pyridine homologues containing alkyl groups are difficult to remove by conventional distillation methods because their molecular weights and vaporization temperatures are relatively close to those of pyridine. The inventors of this application accidentally found in the experiment that these pyridine homologues with alkyl groups (such as methyl) can react with compounds containing aldehyde groups in the presence of a dehydrating agent, thereby dehydrating and coupling to obtain new substances. Based on this discovery, the inventors proposed a reagent for removing pyridine homologues in pyridine.

[0013] The impurity removal reagent in the present invention is composed of inorganic particles and a polymer coating wrapped outside them. Since the polymer coating contains a chain segment with an aldehyde group, in the presence of a dehydrating agent, the pyridine homologues in pyridine (such as methylpyridine, dimethylpyridine, trimethylpyridine, etc.) can undergo a coupling reaction with the polymer coating. Therefore, as the reaction proceeds, these impurities in pyridine can be gradually reduced until completely removed. At the same time, after the reaction is completed, these new substances formed by the pyridine homologues and the polymer of the aldehyde group-containing chain segment are still connected to the polymer coating and thus will not be introduced into pyridine.

[0014] In addition, the ease of post-treatment after impurity removal with pyridine is also a key factor that needs to be considered in the present invention. The applicant has found that pyridine, as a good solvent, also has good solubility for polymers. Therefore, if a conventional linear polymer is used for impurity removal with pyridine, the impurity removal reagent will dissolve in pyridine. Although we can distill pyridine out of the system, due to the presence of the impurity-removing polymer, the viscosity of the system will increase. Therefore, after distilling to a certain extent, it will become increasingly difficult to distill pyridine. Therefore, the polymer coating in the present invention is a cross-linked polymer coating, so it will not dissolve in pyridine. After the impurity removal treatment, only a simple filtration step is required to separate pyridine from the impurity removal reagent, thus simplifying the subsequent separation and purification steps.

[0015] Although the subsequent treatment steps will be simplified by the above cross-linking treatment, the inventors have found that when the cross-linked polymer coating is swollen by pyridine after impurity removal, it will be suspended or dispersed in pyridine for a long time, thus making it impossible to carry out the post-treatment steps in a timely manner. Therefore, a certain amount of inorganic particles is added to the impurity removal reagent. Due to their large self-weight, after the impurity removal is completed, only a period of waiting is required for them to flocculate to the bottom of the reactor, thus further facilitating the subsequent operations.

[0016] Preferably, the cross-linked polymer coating further comprises a polyacrylamide chain segment.

[0017] In the present invention, in order to further improve the reaction efficiency between the cross-linked polymer coating and the pyridine homolog impurities in pyridine, a certain amount of polyacrylamide chain segments are specifically added to the cross-linked polymer coating. It contains amide groups, so it has a certain electron-donating ability, which improves the activity of aldehyde groups and makes the reaction between aldehyde groups and pyridine homologs easier. At the same time, due to the presence of amide groups, ammonia in pyridine can form hydrogen bonds with them, which is more conducive to removing amine impurities contained in pyridine.

[0018] In a second aspect, the present invention also provides a method for preparing the impurity removal reagent, comprising the following steps:

[0019] (1) Surface-modify the inorganic particles so that double bond groups are grafted onto the surface of the inorganic particles;

[0020] (2) Subject the surface-modified inorganic particles to free radical polymerization with monomers containing aldehyde groups and vinyl groups and acrylamide, so as to coat a cross-linked polymer coating on the surface of the inorganic particles;

[0021] (3) Dry and pulverize the whole system to obtain the impurity removal reagent.

[0022] In the process of preparing the impurity removal reagent in the present invention, the inorganic particles are first surface-modified. For example, they can be graft-modified with a silane coupling agent, so that multiple double bond groups are grafted on the surface of the inorganic particles. Therefore, when they are free-radically polymerized with a monomer containing aldehyde groups, vinyl groups, and acrylamide, a cross-linked product can be obtained. Finally, the obtained product only needs to be dried and pulverized to obtain the impurity removal reagent. The whole reaction step is simple and the raw material cost is low.

[0023] Preferably, the inorganic particles include any one of titanium dioxide, silicon dioxide, diatomite, calcium carbonate, ceramic powder, and clay particles.

[0024] Preferably, the monomer containing aldehyde groups and vinyl groups includes any one of acrolein, 2-vinylbenzaldehyde, 4-vinylbenzaldehyde, and 2-vinyl-2-butenal.

[0025] In a third aspect, the present invention also provides an electronic-grade pyridine separation and purification method, including the following steps:

[0026] (S.1) Add an alcoholate to industrial-grade pyridine and carry out a reflux reaction to cause the water in the industrial-grade pyridine to react with sodium alkoxide.

[0027] (S.2) Continue to add the impurity removal reagent to the system and carry out a reflux reaction to cause the alkylpyridine in the industrial-grade pyridine to couple with the impurity removal reagent.

[0028] (S.3) Filter to remove the impurity removal reagent.

[0029] (S.4) Carry out rectification to obtain electronic-grade pyridine.

[0030] In the impurity removal process of the present invention, an alcoholate is selected as the dehydrating agent, which can produce the following beneficial effects:

[0031] (1) The present invention is carried out under the reflux of pyridine, so the temperature is above 120°C. However, since water can form an azeotrope with pyridine, it is difficult to completely remove water from pyridine. However, after adding the alcoholate, due to the hydrolysis property of the alcoholate, corresponding alcohol and base will be formed after its hydrolysis (for example, sodium methoxide will form methanol and sodium hydroxide when encountering water), and the formed alcohol will be gradually separated from the system with the reflux effect, so that the water content in pyridine is effectively reduced as the reaction continues.

[0032] (2) Since water is generated during the coupling process of alkylpyridine and the impurity removal reagent in step (2), the dehydration efficiency of the dehydrating agent has an important impact on the speed of the coupling reaction. Due to the extreme sensitivity of the alcoholate to water, it has extremely strong dehydration efficiency, making the reaction always proceed in the forward direction.

[0033] (3) In the prior art, there is also a method using acetic anhydride as a dehydrating agent. However, acetic anhydride itself has a certain volatility. Therefore, under reflux conditions, the concentration of acetic anhydride will continuously decrease, resulting in a continuous decrease in the reaction rate. At the same time, in subsequent processing, acetic anhydride will also enter the pyridine product through distillation, thus forming impurities, thereby reducing the quality of pyridine. In the present invention, an alcoholate is used as the dehydrating agent. It is a salt itself and will form a base after dehydration. Therefore, it will not sublime. Even if a part of it dissolves in pyridine, it can be separated by distillation. Therefore, it will not affect the quality of the subsequent pyridine finished product.

[0034] Preferably, in the step (1), the alcoholate is the sodium salt or potassium salt of methanol or ethanol.

[0035] Preferably, the addition amount of the alcoholate is 5-15% of the mass of industrial-grade pyridine.

[0036] Preferably, the addition amount of the impurity removal reagent is 10-20% of the mass of industrial-grade pyridine.

[0037] Preferably, in the step (S.3), the system temperature needs to be reduced to below 0 °C before filtration.

[0038] In the present invention, under reflux conditions, some amino impurities in pyridine will not form hydrogen bonds with the polyacrylamide chain segments, but these hydrogen bonds will be broken due to high temperature. However, when the temperature decreases, the hydrogen bonds will re-form at this time, thereby having a certain adsorption effect on such amine impurities.

[0039] Therefore, the present invention has the following beneficial effects:

[0040] (1) The present invention can have a good removal effect on pyridine homologues that are difficult to remove by conventional means, greatly improving the purification effect of pyridine;

[0041] (2) The purification method in the present invention is simple, which is conducive to large-scale industrial application;

[0042] (3) The impurity removal reagent used in the present invention has a low cost. Detailed implementation manners

[0043] The following further describes the present invention with specific embodiments. Those of ordinary skill in the art will be able to implement the present invention based on these descriptions. In addition, the embodiments of the present invention involved in the following description are usually only a part of the embodiments of the present invention, rather than all the embodiments. Therefore, all other embodiments obtained by those of ordinary skill in the art without creative efforts based on the embodiments of the present invention should fall within the protection scope of the present invention.

[0044]

Preparation of impurity removal reagent

[0045] Impurity Removal Reagent A:

[0046] (1) Dissolve 10 g of γ-methacryloxypropyltrimethoxysilane in 50 ml of ethanol, then evenly spray it on the surface of 100 g of diatomite, and after drying, obtain surface-modified diatomite;

[0047] (2) Add 1 part of 1% EDTA solution to 200 parts of an aqueous solution of 20% acrylamide and 10% acrolein, then add 460 parts of deionized water and 50 parts of surface-modified diatomite, and under the condition of continuously passing nitrogen, add 3 parts each of 5% ammonium persulfate and sodium bisulfite solutions, and stir at 50 °C for 4 hours;

[0048] (3) Stop the reaction, remove the moisture under vacuum, and then crush the solid to obtain Impurity Removal Reagent A.

[0049] Impurity Removal Reagent B:

[0050] (1) Dissolve 5 g of γ-methacryloxypropyltrimethoxysilane in 50 ml of ethanol, then evenly spray it on the surface of 100 g of clay particles, and after drying, obtain surface-modified clay particles;

[0051] (2) Add 1 part of 1% EDTA solution to 200 parts of an aqueous solution of 20% acrylamide and 10% acrolein, then add 460 parts of deionized water and 100 parts of surface-modified clay particles, and under the condition of continuously passing nitrogen, add 3 parts each of 5% ammonium persulfate and sodium bisulfite solutions, and stir at 50 °C for 4 hours;

[0052] (3) Stop the reaction, remove the moisture under vacuum, and then crush the solid to obtain Impurity Removal Reagent B.

[0053] Impurity Removal Reagent C:

[0054] (1) Dissolve 5 g of γ-methacryloxypropyltrimethoxysilane in 50 ml of ethanol, then evenly spray it on the surface of 100 g of clay particles, and after drying, obtain surface-modified clay particles;

[0055] (2) Add 1 part of 1% EDTA solution to 200 parts of an aqueous solution of 20% acrylamide and 15% 2-vinylbenzaldehyde, then add 460 parts of deionized water and 100 parts of surface-modified clay particles, and under the condition of continuously passing nitrogen, add 3 parts each of 5% ammonium persulfate and sodium bisulfite solutions, and stir at 50 °C for 4 hours;

[0056] (3) Stop the reaction, remove the moisture under vacuum, and then crush the solid to obtain Impurity Removal Reagent C.

[0057] Impurity Removal Reagent D:

[0058] (1) Dissolve 10 g of γ-methacryloxypropyltrimethoxysilane in 50 ml of ethanol, then evenly spray it on the surface of 100 g of diatomite. After drying, the surface-modified diatomite is obtained;

[0059] (2) Add 1 part of 1% EDTA solution to 200 parts of an aqueous solution of acrolein with a concentration of 30%, then add 460 parts of deionized water and 50 parts of surface-modified diatomite. Under the condition of continuously passing nitrogen, add 3 parts each of 5% ammonium persulfate and sodium bisulfite solution, and stir at 50 °C for 4 hours;

[0060] (3) Stop the reaction, remove the moisture under vacuum, and then crush the solid to obtain the impurity removal reagent D.

[0061] Example 1

[0062] A method for separating and purifying electronic-grade pyridine includes the following steps: Add 10 kg of sodium methoxide to 100 kg of industrial-grade pyridine, heat up to the reflux of pyridine so that the water in the industrial-grade pyridine reacts with sodium methoxide. After reacting for 1 h, continue to add 10 kg of impurity removal reagent A to the system, and continue the reflux reaction for 8 h to couple the alkylpyridine in the industrial-grade pyridine with the impurity removal reagent. Stop heating, then gradually lower the temperature of the system to -10 °C, keep it for 3 h, then filter to recover the impurity removal reagent A and the excess sodium methoxide to obtain a filtrate. Distill the filtrate under a pressure of -0.06 MPa, remove the light components, and collect the components between 86 and 87 °C to obtain electronic-grade pyridine.

[0063] Example 2

[0064] A method for separating and purifying electronic-grade pyridine includes the following steps: Add 10 kg of sodium methoxide to 100 kg of industrial-grade pyridine, heat up to the reflux of pyridine so that the water in the industrial-grade pyridine reacts with sodium methoxide. After reacting for 1 h, continue to add 10 kg of impurity removal reagent B to the system, and continue the reflux reaction for 8 h to couple the alkylpyridine in the industrial-grade pyridine with the impurity removal reagent. Stop heating, then gradually lower the temperature of the system to -10 °C, keep it for 3 h, then filter to recover the impurity removal reagent B and the excess sodium methoxide to obtain a filtrate. Distill the filtrate, and collect the components between 86 and 87 °C to obtain electronic-grade pyridine.

[0065] Example 3

[0066] An electronic-grade pyridine separation and purification method, comprising the following steps: adding 10 kg of sodium methoxide to 100 kg of industrial-grade pyridine, heating up to the reflux of pyridine to cause the water in the industrial-grade pyridine to react with sodium methoxide. After reacting for 1 h, continue to add 10 kg of impurity removal reagent C to the system, and continue the reflux reaction for 8 h to couple the alkylpyridine in the industrial-grade pyridine with the impurity removal reagent. Stop heating, then gradually lower the temperature of the system to -10 °C, keep it for 3 h, and then filter to recover the impurity removal reagent C and the excess sodium methoxide to obtain a filtrate. Rectify the filtrate under a pressure of -0.06 MPa, remove the light components, and collect the components between 86 and 87 °C to obtain electronic-grade pyridine.

[0067] Example 4

[0068] An electronic-grade pyridine separation and purification method, comprising the following steps: adding 5 kg of sodium methoxide to 100 kg of industrial-grade pyridine, heating up to the reflux of pyridine to cause the water in the industrial-grade pyridine to react with sodium methoxide. After reacting for 1 h, continue to add 10 kg of impurity removal reagent A to the system, and continue the reflux reaction for 8 h to couple the alkylpyridine in the industrial-grade pyridine with the impurity removal reagent. Stop heating, then gradually lower the temperature of the system to -10 °C, keep it for 3 h, and then filter to recover the impurity removal reagent A and the excess sodium methoxide to obtain a filtrate. Rectify the filtrate under a pressure of -0.06 MPa, remove the light components, and collect the components between 86 and 87 °C to obtain electronic-grade pyridine.

[0069] Example 5

[0070] An electronic-grade pyridine separation and purification method, comprising the following steps: adding 15 kg of sodium methoxide to 100 kg of industrial-grade pyridine, heating up to the reflux of pyridine to cause the water in the industrial-grade pyridine to react with sodium methoxide. After reacting for 1 h, continue to add 10 kg of impurity removal reagent A to the system, and continue the reflux reaction for 8 h to couple the alkylpyridine in the industrial-grade pyridine with the impurity removal reagent. Stop heating, then gradually lower the temperature of the system to -10 °C, keep it for 3 h, and then filter to recover the impurity removal reagent A and the excess sodium methoxide to obtain a filtrate. Rectify the filtrate under a pressure of -0.06 MPa, remove the light components, and collect the components between 86 and 87 °C to obtain electronic-grade pyridine.

[0071] Example 6

[0072] An electronic-grade pyridine separation and purification method, comprising the following steps: adding 10 kg of sodium methoxide to 100 kg of industrial-grade pyridine, heating to the reflux of pyridine to cause the water in the industrial-grade pyridine to react with sodium methoxide, after reacting for 1 h, adding 5 kg of impurity removal reagent A to the system, continuing the reflux reaction for 8 h to couple the alkyl pyridine in the industrial-grade pyridine with the impurity removal reagent, stopping heating, then gradually reducing the temperature of the system to -10 °C, keeping it for 3 h, filtering to recover the impurity removal reagent A and the excess sodium methoxide to obtain a filtrate, rectifying the filtrate under a pressure of -0.06 MPa, removing the light components, and collecting the components between 86 and 87 °C to obtain electronic-grade pyridine.

[0073] Example 7

[0074] An electronic-grade pyridine separation and purification method, comprising the following steps: adding 10 kg of sodium methoxide to 100 kg of industrial-grade pyridine, heating to the reflux of pyridine to cause the water in the industrial-grade pyridine to react with sodium methoxide, after reacting for 1 h, adding 15 kg of impurity removal reagent A to the system, continuing the reflux reaction for 8 h to couple the alkyl pyridine in the industrial-grade pyridine with the impurity removal reagent, stopping heating, then gradually reducing the temperature of the system to -10 °C, keeping it for 3 h, filtering to recover the impurity removal reagent A and the excess sodium methoxide to obtain a filtrate, rectifying the filtrate under a pressure of -0.06 MPa, removing the light components, and collecting the components between 86 and 87 °C to obtain electronic-grade pyridine.

[0075] Example 8

[0076] An electronic-grade pyridine separation and purification method, comprising the following steps: adding 10 kg of sodium methoxide to 100 kg of industrial-grade pyridine, heating to the reflux of pyridine to cause the water in the industrial-grade pyridine to react with sodium methoxide, after reacting for 1 h, adding 10 kg of impurity removal reagent D to the system, continuing the reflux reaction for 8 h to couple the alkyl pyridine in the industrial-grade pyridine with the impurity removal reagent, stopping heating, then gradually reducing the temperature of the system to -10 °C, keeping it for 3 h, filtering to recover the impurity removal reagent D and the excess sodium methoxide to obtain a filtrate, rectifying the filtrate under a pressure of -0.06 MPa, removing the light components, and collecting the components between 86 and 87 °C to obtain electronic-grade pyridine.

[0077] The purified pyridine in Examples 1 to 8 was subjected to a purity test, and the test results are shown in Table 1 below:

[0078] Table 1

[0079]

[0080] As can be seen from the data in the above table, the purification method in the present invention can effectively remove pyridine homologues, amine compounds and moisture doped in crude pyridine. After purification, the purity of pyridine can be increased to more than 4N grade. At the same time, this purification method in the present invention also has the effects of simple steps and low cost, which is conducive to large-scale industrial application.

Claims

1. An impurity removal reagent for purifying pyridine, characterized in that, the impurity removal reagent contains inorganic particles; and a cross-linked polymer coating wrapped outside the inorganic particles; the cross-linked polymer coating contains segments with aldehyde groups; the cross-linked polymer coating also contains polyacrylamide segments.

2. A method for preparing the impurity removal reagent according to claim 1, characterized in that, it includes the following steps: (1) Perform surface modification on the inorganic particles so that double bond groups are grafted on the surface of the inorganic particles; (2) Subject the surface-modified inorganic particles to free radical polymerization with monomers containing aldehyde groups and vinyl groups and acrylamide, so as to coat a cross-linked polymer coating on the surface of the inorganic particles; (3) Dry and pulverize the whole system to obtain the impurity removal reagent.

3. According to the method described in claim 2, characterized in that, the inorganic particles include any one of titanium dioxide, silicon dioxide, diatomite, calcium carbonate, ceramic powder, and clay particles.

4. According to the method described in claim 2, characterized in that, the monomers containing aldehyde groups and vinyl groups include any one of acrolein, 2-vinylbenzaldehyde, 4-vinylbenzaldehyde, and 2-vinyl-2-butenal.

5. An electronic-grade pyridine separation and purification method, characterized in that, it includes the following steps: (S.1) Add an alcoholate to industrial-grade pyridine and reflux to react, so that the water in the industrial-grade pyridine reacts with the alcoholate; (S.2) Continue to add the impurity removal reagent described in claim 1 to the system and reflux to react, so that the alkylpyridine in the industrial-grade pyridine couples with the impurity removal reagent; (S.3) Filter out the impurity removal reagent; (S.4) Rectify to obtain electronic-grade pyridine.

6. According to an electronic-grade pyridine separation and purification method described in claim 5, characterized in that, the alcoholate in step (S.1) is the sodium salt or potassium salt of methanol or ethanol.

7. According to an electronic-grade pyridine separation and purification method described in claim 5 or 6, characterized in that, the addition amount of the alcoholate is 5-15% of the mass of industrial-grade pyridine.

8. According to an electronic-grade pyridine separation and purification method described in claim 5, characterized in that, the addition amount of the impurity removal reagent is 5-15% of the mass of industrial-grade pyridine.

9. According to an electronic-grade pyridine separation and purification method described in claim 5, characterized in that, the temperature of the system needs to be reduced below 0 °C before filtration in step (S.3).

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