Vinylpyridine with low oxygen-containing compound content and preparation method thereof
By adding formaldehyde multiple times in the reaction between methylpyridine and formaldehyde and optimizing the reaction conditions, the oxygen-containing compound content of vinylpyridine is successfully reduced, its purity and production efficiency are improved, and the cost and efficiency in the existing technology are solved. Low problem.
Patent Information
- Application Number
- CN202310704464.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-06-14
- Publication Date
- 2024-12-17
AI Technical Summary
In the prior art, the production cost and efficiency of 2-vinylpyridine and 4-vinylpyridine with low oxygen-containing compound content is high, and the side reaction is high, and the content of compounds containing oxygen atoms is high, which affects the separation process. Difficulty.
The molar ratio of the initial methylpyridine to formaldehyde was used to react in (4:1)-(13:1), and the temperature was raised to 120℃-300℃. The formaldehyde content was controlled by adding multiple times. The formaldehyde content was ≤5wt.%, and the formaldehyde content was ≤5wt.%, and the Distillation is carried out at 50℃-200℃ to optimize reaction conditions to reduce side reactions and improve purity and efficiency.
It effectively reduces the oxygen-containing compound content of vinylpyridine, improves the purity and distillation efficiency of the product, reduces the occurrence of side reactions, and reduces production costs.
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Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of preparation and application of chemical products, and specifically relates to vinyl pyridine with low oxygen-containing compound content and a preparation method thereof. Background Art
[0002] Vinylpyridine is usually divided into 2-vinylpyridine and 4-vinylpyridine. In the prior art, 2-vinylpyridine or 4-vinylpyridine is a raw material of 2-picoline or 4-picoline, which is reacted to generate hydroxyethylpyridine through high temperature and high pressure or in the presence of a catalyst, and then separated to obtain 2-vinylpyridine and 4-vinylpyridine. However, under high temperature and high pressure, hydroxyl easily reacts with substances containing groups such as aldehyde groups and carboxyl groups to generate compounds (oxygenated compounds) containing oxygen atoms, which not only affects the conversion rate of formaldehyde, but also increases the difficulty of subsequent separation processes. Therefore, the existing preparation of 2-vinylpyridine and 4-vinylpyridine with low oxygenated compound content becomes a technical difficulty.
[0003] CN200410024128.8 discloses an industrial-scale process for preparing 2-vinylpyridine, which uses 2-hydroxyethylpyridine as a raw material to remove a molecule of water in the presence of a catalyst to generate 2-vinylpyridine, then separates the water by alkali precipitation or salting out, and then obtains 2-vinylpyridine by vacuum distillation. This process directly uses 2-hydroxyethylpyridine as a raw material to prepare 2-vinylpyridine, and its cost price is relatively high.
[0004] CN201410340140.3 discloses an efficient and environmentally friendly method for preparing 2-vinylpyridine, which uses 2-hydroxyethylpyridine and a catalyst for reactive distillation to obtain 2-vinylpyridine and water, and then obtains 2-vinylpyridine by reduced pressure distillation. The production efficiency is low.
[0005] CN201610624825.X discloses a process for preparing 4-vinyl pyridine on an industrial scale, which uses 4-hydroxyethyl pyridine as a raw material, performs a dehydration reaction in the presence of a catalyst, and then obtains 4-vinyl pyridine by vacuum distillation. This process directly uses 4-hydroxyethyl pyridine as a raw material to prepare 4-vinyl pyridine, and its cost price is relatively high.
[0006] CN200410024127.3 discloses an industrial-scale process for preparing 2-hydroxyethylpyridine, which uses 2-methylpyridine as a starting material and reacts with paraformaldehyde in the presence of a catalyst to produce 2-hydroxyethylpyridine. The process used in the present invention adopts an intermittent method for feeding once, so it has more by-products and lower production efficiency.
[0007] Although the above method can produce 2-vinylpyridine or 4-vinylpyridine, it has high production cost and low production efficiency, and has many side reactions. The content of compounds containing oxygen atoms (oxygen-containing compounds) in the reaction products is high. Summary of the invention
[0008] The technical problem to be solved by the present invention is to overcome the above-mentioned defects in the prior art and provide a method for preparing vinyl pyridine, wherein the produced vinyl pyridine has a low content of oxygen-containing compounds.
[0009] The method for preparing vinyl pyridine with low oxygen-containing compound content of the present invention comprises the following steps:
[0010] (1) mixing initial picoline and initial formaldehyde, raising the temperature to 120° C.-300° C. for reaction until the formaldehyde content is ≤5 wt.%, adding formaldehyde to the reaction system, and continuing the reaction until the formaldehyde content is ≤5 wt.%, repeating the above step of adding formaldehyde, and reacting until the molar percentage content of picoline in the reaction system is ≤85%, thereby obtaining a reaction product;
[0011] (2) The reaction product is heated to 50° C.-200° C. and distilled until the vinyl pyridine content in the system is ≥85 wt.%, to obtain vinyl pyridine with a low oxygen-containing compound content.
[0012] In step (1), the picoline is 2-picoline or 4-picoline.
[0013] In step (2), the vinyl pyridine is 2-vinyl pyridine or 4-vinyl pyridine.
[0014] In step (1), the molar ratio of the initial picoline to the initial formaldehyde is (4:1)-(13:1), preferably (10:1)-(5:1). The temperature is raised to 120°C-300°C for reaction, preferably 150°C-250°C.
[0015] In step (1), the molar amount of formaldehyde added to the reaction system is 1.5%-15%, preferably 3%-13% of the initial picoline.
[0016] The reaction described in step (1) is carried out in a batch reactor or a continuous reactor, wherein the continuous reactor is a tubular reactor or a series of tank reactors.
[0017] The distillation pressure in step (2) is 0.001Mpa-0.1Mpa, preferably 0.03Mpa-0.08Mpa.
[0018] The content of oxygen-containing compounds in the vinyl pyridine obtained in step (2) is 0.001 wt.%-5 wt.%, and is further controlled within 3.5 wt.%. The reaction product is heated to 50°C-200°C, preferably 80°C-150°C.
[0019] A vinyl pyridine with low oxygen-containing compound content is prepared by the preparation method of vinyl pyridine with low oxygen-containing compound content.
[0020] The low oxygen-containing compound content vinyl pyridine prepared by the present invention can be used to prepare latex.
[0021] Specifically, the method for preparing vinyl pyridine with low oxygen-containing compound content comprises the following steps:
[0022] (1) Initial 2-methylpyridine or 4-methylpyridine and initial formaldehyde are uniformly mixed in a molar ratio of (4:1)-(13:1) and added to a reactor, and the temperature is raised to 120°C-300°C for reaction. Formaldehyde is detected during the reaction. When the formaldehyde content is ≤5wt.%, formaldehyde is added to the reaction system in a molar amount of 1.5%-15% of the initial methylpyridine, and the reaction is continued until the formaldehyde content is ≤5wt.%. The above steps and amounts of adding formaldehyde are repeated to react until the molar percentage content of 2-methylpyridine or 4-methylpyridine in the reaction system is ≤85%, thereby obtaining a reaction product. During the entire reaction, 2-methylpyridine or 4-methylpyridine is kept in excess.
[0023] (2) adding the reaction product to a distillation tower, raising the temperature to 50° C.-200° C., adjusting the distillation pressure to 0.001 MPa-0.1 MPa, and performing distillation operation until the vinyl pyridine content in the system is ≥85 wt.%, to obtain 2-vinyl pyridine or 4-vinyl pyridine with a low oxygen-containing compound content.
[0024] The present invention adopts excessive picoline to react with formaldehyde, and in the reaction process, a process of adding formaldehyde in small amounts and multiple times to react with excessive picoline is coordinated with the reaction conditions, so that formaldehyde in the system preferentially reacts with picoline as a nucleophilic reagent to generate hydroxyethylpyridine through nucleophilic addition reaction, inhibits the aldol condensation reaction of formaldehyde and hydroxyethylpyridine and other side reactions of formaldehyde in the system, so that the content of compounds containing oxygen atoms brought by the side reaction of formaldehyde in the reaction product is low. In addition, the method of the present invention improves the efficiency of the distillation process due to the reduction of side reaction products in the reaction of formaldehyde and picoline, thereby effectively improving the production efficiency.
[0025] Compared with the prior art, the present invention has the following beneficial effects:
[0026] (1) The vinyl pyridine prepared by the method of the present invention has a low content of oxygen-containing compounds and high purity.
[0027] (2) The method for preparing vinyl pyridine with low oxygen-containing compound content of the present invention reduces the occurrence of side reactions and improves the distillation efficiency of the reaction product. DETAILED DESCRIPTION
[0028] In order to better understand the technical solution of the present invention, the content of the present invention is further described below in conjunction with the embodiments, but the content of the present invention is not limited to the following embodiments.
[0029] Unless otherwise specified, the raw materials used in the following examples and comparative examples of the present invention were obtained from commercial channels.
[0030] Example 1
[0031] The method for preparing 2-vinylpyridine with low oxygen-containing compound content comprises the following steps:
[0032] (1) Initial 2-methylpyridine and initial formaldehyde were mixed uniformly at flow rates of 40 kg / h and 1.65 kg / h, respectively, and then continuously added to a tubular reactor at a temperature of 120° C. for reaction, and the formaldehyde content at each position in the tubular reactor was detected. At the position of the reactor where the formaldehyde content was 4.9 wt.%, formaldehyde was added at a constant flow rate of 0.6 kg / h; the reaction was continued, and the formaldehyde content of the downstream pipe section was continuously detected. At the position where the formaldehyde content was 4.7 wt.%, formaldehyde was added at a constant flow rate of 0.41 kg / h; and the detection was continued. The formaldehyde content in the downstream pipe section is detected, and when the formaldehyde content drops to 4.7wt.%, formaldehyde is continuously added at a constant flow rate of 0.4kg / h; the formaldehyde content in the downstream pipe section is continuously detected, and when the formaldehyde content drops to 4.6wt.%, formaldehyde is continuously added at a constant flow rate of 0.32kg / h; the formaldehyde content in the downstream pipe section is continuously detected, and when the formaldehyde content drops to 4.4wt.%, formaldehyde is continuously added at a constant flow rate of 0.2kg / h, until the molar percentage content of 2-methylpyridine in the reaction system reaches 84.8%, thereby obtaining a reaction product.
[0033] (2) The reaction product is added to a distillation tower, the temperature is raised to 100° C., and the distillation pressure is adjusted to 0.1 MPa for distillation operation until the 2-vinylpyridine content in the system reaches 85.4 wt.%, thereby obtaining 2-vinylpyridine with a low oxygen-containing compound content.
[0034] Example 2
[0035] The method for preparing 4-vinylpyridine with low oxygen-containing compound content comprises the following steps:
[0036] (1) Initial 4-methylpyridine and initial formaldehyde are mixed uniformly at flow rates of 40 kg / h and 1.29 kg / h, respectively, and then continuously added to a tubular reactor at a temperature of 150° C. for reaction, the formaldehyde content at each position in the tubular reactor is detected, and formaldehyde is added at a constant flow rate of 0.62 kg / h at the position of the reactor where the formaldehyde content is 4.6 wt.%; the reaction is continued, and the formaldehyde content of the downstream pipe section is continuously detected, and when the formaldehyde content is 4.4 wt.%, formaldehyde is added at a constant flow rate of 0.44 kg / h; the formaldehyde content of the downstream pipe section is continuously detected, and when the formaldehyde content drops to 4.9 wt.%, formaldehyde is continuously added at a constant flow rate of 0.4 kg / h; the formaldehyde content of the downstream pipe section is continuously detected, and when the formaldehyde content drops to 4.8 wt.%, formaldehyde is added at a constant flow rate of 0.2 kg / h; the addition is repeated four or more times until the 4-methylpyridine molar percentage content in the reaction system reaches 84.2%, thereby obtaining a reaction product.
[0037] (2) The reaction product was added to a distillation tower, the temperature was raised to 120° C., and the distillation pressure was adjusted to 0.08 MPa for distillation operation until the 4-vinylpyridine content in the system reached 85.3 wt.%, to obtain 4-vinylpyridine with a low oxygen-containing compound content.
[0038] Example 3
[0039] The method for preparing 4-vinylpyridine with low oxygen-containing compound content comprises the following steps:
[0040] (1) Initial 4-methylpyridine and initial formaldehyde are mixed uniformly at flow rates of 40 kg / h and 2.17 kg / h, respectively, and then continuously added to a tubular reactor at a temperature of 200° C. for reaction, the formaldehyde content at each position in the tubular reactor is detected, and formaldehyde is added at a constant flow rate of 0.43 kg / h at the reactor position where the formaldehyde content is 4.8 wt.%; the reaction is continued, and the formaldehyde content of the downstream pipe section is continuously detected, and when the formaldehyde content is 4.6 wt.%, formaldehyde is added at a constant flow rate of 0.42 kg / h; the formaldehyde content of the downstream pipe section is continuously detected, and when the formaldehyde content drops to 4.5 wt.%, formaldehyde is added at a constant flow rate of 0.24 kg / h; the addition is repeated three or more times until the molar percentage of 4-methylpyridine in the reaction system reaches 84.3%, thereby obtaining a reaction product.
[0041] (2) The reaction product was added to a distillation tower, the temperature was raised to 150° C., and the distillation pressure was adjusted to 0.05 MPa for distillation operation until the 4-vinylpyridine content in the system reached 85.6 wt.%, to obtain 4-vinylpyridine with a low oxygen-containing compound content.
[0042] Example 4
[0043] The method for preparing 2-vinylpyridine with low oxygen-containing compound content comprises the following steps:
[0044] (1) Initial 2-methylpyridine and initial formaldehyde are mixed uniformly at flow rates of 40 kg / h and 2.58 kg / h, respectively, and then continuously added to a tubular reactor at a temperature of 250° C. for reaction, the formaldehyde content at each position in the tubular reactor is detected, and formaldehyde is added at a constant flow rate of 0.2 kg / h at the reactor position where the formaldehyde content is 4.7 wt.%; the reaction is continued, and the formaldehyde content of the downstream pipe section is continuously detected. When the formaldehyde content is 4.8 wt.%, formaldehyde is added at a constant flow rate of 0.19 kg / h; the addition is repeated twice or more until the molar percentage of 2-methylpyridine in the reaction system reaches 84.6%, thereby obtaining a reaction product.
[0045] (2) The reaction product was added to a distillation tower, the temperature was raised to 170° C., and the distillation pressure was adjusted to 0.03 MPa for distillation operation until the 2-vinylpyridine content in the system reached 85.1 wt.%, to obtain 2-vinylpyridine with a low oxygen-containing compound content.
[0046] Example 5
[0047] The method for preparing 2-vinylpyridine with low oxygen-containing compound content comprises the following steps:
[0048] (1) Initial 2-methylpyridine and initial formaldehyde are mixed uniformly at flow rates of 40 kg / h and 3.22 kg / h, respectively, and then continuously added to a tubular reactor at a temperature of 300° C. for reaction, and the formaldehyde content at various positions in the tubular reactor is detected. At the position of the reactor where the formaldehyde content is 4.8 wt.%, formaldehyde is added at a constant flow rate of 0.2 kg / h; until the molar percentage of 2-methylpyridine in the reaction system reaches 84.2%, thereby obtaining a reaction product.
[0049] (2) The reaction product is added to a distillation tower, the temperature is raised to 200° C., and the distillation pressure is adjusted to 0.001 MPa for distillation operation until the 2-vinylpyridine content in the system reaches 85.2 wt.%, thereby obtaining 2-vinylpyridine with a low oxygen-containing compound content.
[0050] Comparative Example 1
[0051] A method for preparing 2-vinylpyridine comprises the following steps:
[0052] (1) Initial 2-methylpyridine and initial formaldehyde were mixed uniformly at flow rates of 40 kg / h and 3.22 kg / h, respectively, and then continuously added into a tubular reactor at a temperature of 200° C. for reaction. The molar percentage content of 2-methylpyridine in the reaction system was detected to be 84.7%, thereby obtaining a reaction product.
[0053] (2) The reaction product was added to a distillation tower, the temperature was raised to 150° C., and the distillation pressure was adjusted to 0.05 MPa to perform distillation operation until the 2-vinylpyridine content in the system reached 85.6 wt.%, to obtain 2-vinylpyridine.
[0054] Comparative Example 2
[0055] A method for preparing 4-vinylpyridine comprises the following steps:
[0056] (1) Initial 4-methylpyridine and initial formaldehyde were mixed uniformly at flow rates of 40 kg / h and 3.42 kg / h, respectively, and then continuously added into a tubular reactor at a temperature of 300° C. for reaction. The molar percentage content of 4-methylpyridine in the reaction system was detected to be 84.3%, and a reaction product was obtained.
[0057] (2) The reaction product was added to a distillation tower, the temperature was raised to 200° C., and the distillation pressure was adjusted to 0.01 MPa to perform distillation operation until the 4-vinylpyridine content in the system reached 85.1 wt.%, to obtain 4-vinylpyridine.
[0058] Comparative Example 3
[0059] A method for preparing 2-vinylpyridine comprises the following steps:
[0060] (1) Initial 2-methylpyridine and initial formaldehyde are mixed uniformly at flow rates of 40 kg / h and 3.68 kg / h, respectively, and then continuously added to a tubular reactor at a temperature of 250° C. for reaction, the formaldehyde content at each position in the tubular reactor is detected, and formaldehyde is added at a constant flow rate of 0.2 kg / h at the reactor position where the formaldehyde content is 4.8 wt.%; the reaction is continued, and the formaldehyde content of the downstream pipe section is continuously detected. When the formaldehyde content is 4.6 wt.%, formaldehyde is added at a constant flow rate of 0.19 kg / h; the addition is repeated twice or more until the molar percentage of 2-methylpyridine in the reaction system reaches 84.6%, thereby obtaining a reaction product.
[0061] (2) The reaction product was added to a distillation tower, the temperature was raised to 180° C., and the distillation pressure was adjusted to 0.03 MPa to perform distillation operation until the 2-vinylpyridine content in the system reached 85.3 wt.%, to obtain 2-vinylpyridine.
[0062] Comparative Example 4
[0063] A method for preparing 2-vinylpyridine comprises the following steps:
[0064] (1) Initial 2-methylpyridine and initial formaldehyde were mixed uniformly at flow rates of 40 kg / h and 1 kg / h, respectively, and then continuously added to a tubular reactor at a temperature of 150° C. for reaction, and the formaldehyde content at each position in the tubular reactor was detected. At the position of the reactor where the formaldehyde content was 4.7 wt.%, formaldehyde was added at a constant flow rate of 0.6 kg / h; the reaction was continued, and the formaldehyde content of the downstream pipe section was continuously detected. At the position where the formaldehyde content was 4.8 wt.%, formaldehyde was added at a constant flow rate of 0.5 kg / h; and the detection was continued. The formaldehyde content in the upstream pipe section is detected, and formaldehyde is continuously added at a constant flow rate of 0.4 kg / h when the formaldehyde content drops to 4.6 wt.%; the formaldehyde content in the downstream pipe section is continuously detected, and formaldehyde is continuously added at a constant flow rate of 0.4 kg / h when the formaldehyde content drops to 4.9 wt.%; the formaldehyde content in the downstream pipe section is continuously detected, and formaldehyde is continuously added at a constant flow rate of 0.4 kg / h when the formaldehyde content drops to 4.3 wt.% until the molar percentage content of 2-methylpyridine in the reaction system reaches 84.8%, thereby obtaining a reaction product.
[0065] (2) The reaction product was added to a distillation tower, the temperature was raised to 120° C., and the distillation pressure was adjusted to 0.03 MPa to perform distillation operation until the 2-vinylpyridine content in the system reached 85.3 wt.%, to obtain 4-vinylpyridine.
[0066] Comparative Example 5
[0067] A method for preparing 2-vinylpyridine comprises the following steps:
[0068] (1) Initial 2-methylpyridine and initial formaldehyde were mixed uniformly at flow rates of 40 kg / h and 0.43 kg / h, respectively, and then continuously added to a tubular reactor at a temperature of 120° C. for reaction, and the formaldehyde content at each position in the tubular reactor was detected. At the position of the reactor where the formaldehyde content was 4.8 wt.%, formaldehyde was added at a constant flow rate of 0.6 kg / h; the reaction was continued, and the formaldehyde content of the downstream pipe section was continuously detected. At the position where the formaldehyde content was 4.7 wt.%, formaldehyde was added at a constant flow rate of 0.41 kg / h; and the detection was continued. The formaldehyde content in the downstream pipe section is detected, and when the formaldehyde content drops to 4.6wt.%, formaldehyde is continuously added at a constant flow rate of 0.4kg / h; the formaldehyde content in the downstream pipe section is continuously detected, and when the formaldehyde content drops to 4.6wt.%, formaldehyde is continuously added at a constant flow rate of 0.32kg / h; the formaldehyde content in the downstream pipe section is continuously detected, and when the formaldehyde content drops to 4.4wt.%, formaldehyde is continuously added at a constant flow rate of 0.2kg / h, until the molar percentage content of 2-methylpyridine in the reaction system reaches 84.5%, thereby obtaining a reaction product.
[0069] (2) The reaction product was added to a distillation tower, the temperature was raised to 100° C., and the distillation pressure was adjusted to 0.008 MPa to perform distillation operation until the 2-vinylpyridine content in the system reached 85.2 wt.%, to obtain 2-vinylpyridine.
[0070] The content of 2-vinylpyridine or 4-vinylpyridine in the above Examples 1-5 and Comparative Examples 1-5 was detected according to the method in CN202110548295.6 published on September 7, 2021.
[0071] Formaldehyde Formaldehyde content test method: GB / T 9009-2011.
[0072] The detection method of the oxygen-containing compound in the prepared 2-vinylpyridine or 4-vinylpyridine is as follows:
[0073] The test was performed using a gas chromatograph equipped with a hydrogen flame ionization detector. The chromatographic column and operating conditions used are shown in Table 1.
[0074] Table 1 Test conditions
[0075]
[0076]
[0077] After all parts of the chromatograph reach the above conditions and stabilize, the sample is injected into the chromatographic column and analyzed in reverse order, and the component content is calculated by the peak area normalization method, and the arithmetic mean of the results of two parallel determinations is taken as the determination result, and the absolute difference of the two parallel determination results is not greater than 0.02%, and the peak retention time of the oxygen-containing compound in the gas chromatography is 4.2min-4.5min. The detection results of the oxygen-containing compounds in 2-vinylpyridine or 4-vinylpyridine of Examples 1-5 and Comparative Examples 1-2 are shown in Table 2.
[0078] Table 2 Test results
[0079] project Oxygen-containing compound content (wt.%) Example 1 0.21 Example 2 0.087 Example 3 0.001 Example 4 0.12 Example 5 0.49 Comparative Example 1 0.65 Comparative Example 2 0.67 Comparative Example 3 0.79 Comparative Example 4 0.65 Comparative Example 5 0.54
[0080] From the above examples and comparative examples, and the above table, it can be seen that Example 43 and Comparative Example 1 use the same content of 2-vinylpyridine and formaldehyde for reaction, and Example 5 and Comparative Example 2 use the same content of 4-vinylpyridine and formaldehyde for reaction. It can be seen that the use of the method described in this method to add formaldehyde step by step for reaction can effectively reduce the content of oxygen-containing compounds. From Example 3 and Example 5, it can be seen that when the same molar number of vinylpyridine and formaldehyde are used for reaction, formaldehyde can be effectively added after multiple additions to reduce the content of oxygen-containing compounds. From Examples 1-5 and Comparisons 1 and 2, it can be seen that the vinylpyridine prepared by the method described in the present invention can effectively reduce the content of oxygen-containing compounds in the product. Example 4 and Comparative Example 3 react under the same formaldehyde addition conditions. It can be seen that when the initial formaldehyde content is high, the content of oxygen-containing compounds will increase. This is because a high formaldehyde concentration is conducive to the generation of oxygen-containing compounds. Example 1 and Comparative Example 4 react under the same initial 2-methylpyridine and initial formaldehyde content conditions. It can be seen that the content of oxygen-containing compounds in the reaction system increases with the increase in the amount of formaldehyde added. In Example 1 and Comparative Example 5, under the same formaldehyde addition conditions, when the initial formaldehyde concentration is low, the content of oxygen-containing compounds will also increase. In Comparative Example 4, when formaldehyde is added, the local concentration of formaldehyde at the addition port is high, which increases the degree of local side reactions. Therefore, the more formaldehyde is added, the higher the content of oxygen-containing compounds. Comparative Example 5 is because the initial formaldehyde content is low. In order to ensure the full reaction of 2-vinylpyridine in the reaction system, the added formaldehyde needs a longer time to react with 2-methylpyridine. As the time formaldehyde exists in the system increases, the side reaction time of formaldehyde is also relatively increased, so the content of oxygen-containing compounds increases accordingly.
[0081] It can be seen from Examples 1-5 and Comparative Examples 1-5 and 2 that the vinyl pyridine prepared by the method of the present invention can effectively reduce the content of oxygen-containing compounds in the product.
[0082] Of course, the above contents are only preferred embodiments of the present invention and cannot be considered to limit the scope of the embodiments of the present invention. The present invention is not limited to the above examples, and equal changes and improvements made by ordinary technicians in the technical field within the essential scope of the present invention should all fall within the scope of the patent coverage of the present invention.
Claims
1. A method for preparing vinyl pyridine with low oxygen-containing compound content, Features: The following steps are involved: (1) mixing initial picoline and initial formaldehyde, raising the temperature to 120° C.-300° C. for reaction until the formaldehyde content is ≤5 wt.%, adding formaldehyde to the reaction system, and continuing the reaction until the formaldehyde content is ≤5 wt.%, repeating the above step of adding formaldehyde, and reacting until the molar percentage content of picoline in the reaction system is ≤85%, thereby obtaining a reaction product; (2) The reaction product is heated to 50° C.-200° C. and distilled until the vinyl pyridine content in the system is ≥85 wt.%, to obtain vinyl pyridine with a low oxygen-containing compound content.
2. The method for preparing vinyl pyridine with low oxygen-containing compound content according to claim 1, Features: In step (1), the picoline is 2-picoline or 4-picoline.
3. The method for preparing vinyl pyridine with low oxygen-containing compound content according to claim 1, Features: In step (2), the vinyl pyridine is 2-vinyl pyridine or 4-vinyl pyridine.
4. The method for preparing vinyl pyridine with low oxygen-containing compound content according to claim 1, Features: The molar ratio of the initial picoline to the initial formaldehyde in step (1) is (4:1)-(13:1).
5. The method for preparing vinyl pyridine with low oxygen-containing compound content according to claim 1, Features: In step (1), the molar amount of formaldehyde added to the reaction system is 1.5%-15% of the initial picoline.
6. The method for preparing vinyl pyridine with low oxygen-containing compound content according to claim 1, Features: The distillation pressure in step (2) is 0.001Mpa-0.1Mpa.
7. The method for preparing vinyl pyridine with low oxygen-containing compound content according to claim 1, Features: The content of oxygen-containing compounds in the vinylpyridine obtained in step (2) is 0.001wt.%-5wt.%.
8. A vinylpyridine having a low oxygenate content, Features: The invention is prepared by the method for preparing vinyl pyridine with low oxygen-containing compound content as described in any one of claims 1 to 7.