Method for increasing yield of by-product 3-methylpyridine in pyridine base synthesis process and pyridine base synthesis method

Abstract

The invention relates to the technical field of organic synthesis of 3-methylpyridine, in particular to a method for increasing the yield of a byproduct 3-methylpyridine in a pyridine base synthesis process and a pyridine base synthesis method. Generally, in the process of synthesizing the pyridine base by using formaldehyde and acetaldehyde, taking the molar ratio of the reaction raw materials formaldehyde to acetaldehyde at about 1: 1 as an example, the molar ratio of the reaction product pyridine base to the reaction byproduct 3-methylpyridine is about 8: 2, and the molar yield is about 77%. In the pyridine base synthesis process, a certain proportion of the aldehyde group-containing three-carbon compound is added into the reaction raw materials, so that the yield of the reaction byproduct 3-methylpyridine can be effectively increased, and the yield of the pyridine base is reduced.

Description

Technical Field

[0001] The present application relates to the technical field of organic synthesis of 3-methylpyridine, and in particular to a method for increasing the yield of 3-methylpyridine as a byproduct in the synthesis process of pyridine base, and a method for synthesizing pyridine base. Background Art

[0002] 3-Methylpyridine is an important pyridine derivative, which is mainly used in the fields of pesticides, medicines, feed additives, spices, etc. 3-Methylpyridine can be used not only to produce vitamins such as niacin and niacinamide, but also to produce pesticides such as imidacloprid and pyrimidine.

[0003] The source of 3-methylpyridine is mainly a by-product obtained when pyridine base is synthesized from formaldehyde and acetaldehyde in a fluidized bed reactor. In the reaction of pyridine base synthesis, the molar ratio of the product pyridine base to the by-product 3-methylpyridine is about 8:2.

[0004] However, at present, the demand for 3-methylpyridine in the downstream market is increasing, and the market price of 3-methylpyridine is also higher than that of pyridine base. Therefore, it is necessary to find new methods to increase the production capacity of 3-methylpyridine. Summary of the invention

[0005] The present application provides a method for increasing the yield of 3-methylpyridine, a by-product in the synthesis process of pyridine base, and a synthesis method of pyridine base, aiming to increase the yield of 3-methylpyridine, a by-product in the synthesis process of pyridine base.

[0006] Generally, in the process of synthesizing pyridine base from formaldehyde and acetaldehyde, taking the molar ratio of the reaction raw materials formaldehyde to acetaldehyde as about 1:1, the molar ratio of the reaction product pyridine base to the reaction by-product 3-methylpyridine is about 8:2, and the molar yield is about 77%.

[0007] The present application can effectively increase the yield of the reaction byproduct 3-methylpyridine and reduce the yield of pyridine base by adding a certain proportion of a three-carbon compound with an aldehyde group to the reaction raw materials during the synthesis of pyridine base. Through experiments, it was found that the method changes the ratio of 3-methylpyridine to pyridine base in the synthesis process of pyridine base by adjusting the ratio of the added three-carbon compound with an aldehyde group to acetaldehyde.

[0008] The present application has respectively tested the process of synthesizing pyridine base by adding different proportions (10wt.%, 20wt.%, 30wt.%, 40wt.%, 50wt.%) of three-carbon compounds with aldehyde groups to the reaction raw materials. It can be seen from the test results that with the increase in the amount of the above-mentioned materials added, the output of the reaction product pyridine base decreases, while the output of the reaction byproduct 3-methylpyridine increases. It is finally concluded that when the amount of the three-carbon compound with aldehyde group added to the reaction raw materials is 30wt.%, the molar ratio of the reaction product pyridine base to the reaction byproduct 3-methylpyridine is 8:5.2, and the molar yield is about 79%. By using the method provided by the present application, the production capacity of 3-methylpyridine is significantly improved.

[0009] In a first aspect, the present application provides a method for increasing the yield of 3-methylpyridine, a by-product in the synthesis process of pyridine base, using the following technical scheme:

[0010] A method for increasing the yield of byproduct 3-methylpyridine in the process of pyridine base synthesis comprises adding a three-carbon compound with an aldehyde group into the reaction raw material for synthesizing the pyridine base.

[0011] Optionally, the three-carbon compound with an aldehyde group is added to the reaction raw material in an amount of 10-50 wt.%.

[0012] Optionally, the three-carbon compound with an aldehyde group is added to the reaction raw materials in an amount of 20-40 wt.%.

[0013] Optionally, the three-carbon compound with an aldehyde group is added to the reaction raw material in an amount of 30 wt.%.

[0014] Optionally, the three-carbon compound having an aldehyde group includes propionaldehyde.

[0015] Optionally, the reaction raw materials are formaldehyde and acetaldehyde.

[0016] Optionally, the weight ratio of the formaldehyde to the acetaldehyde is (1-3):1.

[0017] In a second aspect, the present application provides a method for synthesizing a pyridine base, using the following technical solution:

[0018] A method for synthesizing a pyridine base, the method specifically comprising the following steps:

[0019] Prepare the reaction raw materials for synthesizing pyridine base as required, and add the three-carbon compound with aldehyde group into the reaction raw materials according to the above method;

[0020] Under the action of a pyridine base synthesis catalyst, the reaction is carried out in an ammonia environment at a temperature of 350-500° C., and the reaction product is cooled and collected to obtain the reaction product pyridine base and the reaction by-product 3-methylpyridine.

[0021] Optionally, the cooling temperature is (-15) to (-5) °C.

[0022] Optionally, samples are taken and analyzed every hour during the reaction, and the reaction is stopped after the contents of the reaction product and the reaction by-product decrease significantly.

[0023] Optionally, the reaction time is 5-10 hours.

[0024] Optionally, the amount of the pyridine base synthesis catalyst used is 100-150g, and the feed mass space velocity is 0.3-1h -1 .

[0025] Optionally, the regeneration temperature of the pyridine base synthesis catalyst is 400-600° C., and the calcination time is 2-8 h.

[0026] In summary, the present application includes at least one of the following beneficial technical effects:

[0027] The present application aims to increase the yield of 3-methylpyridine, a byproduct of the synthesis of pyridine base. Generally, in the process of synthesizing pyridine base using formaldehyde and acetaldehyde, taking the molar ratio of the reaction raw materials formaldehyde to acetaldehyde as about 1:1 as an example, the molar ratio of the reaction product pyridine base to the reaction byproduct 3-methylpyridine is about 8:2, and the molar yield is about 77%.

[0028] The present application can effectively increase the yield of the reaction byproduct 3-methylpyridine and reduce the yield of pyridine base by adding a certain proportion of a three-carbon compound with an aldehyde group to the reaction raw materials during the synthesis of pyridine base. Through experiments, it was found that the method changes the ratio of 3-methylpyridine to pyridine base in the synthesis process of pyridine base by adjusting the ratio of the added three-carbon compound with an aldehyde group to acetaldehyde. DETAILED DESCRIPTION

[0029] Before describing the embodiments of the present application in detail, it should be understood that the terms used herein are only used for the purpose of describing specific embodiments. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by ordinary technicians in the field to which the terms belong.

[0030] It should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. Further, in the description of this application, unless otherwise specified, the meaning of "plurality" is two or more.

[0031] The endpoints and any values ​​of the ranges disclosed in this application 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.

[0032] In the present application, the terms "comprise" or "include" are open expressions, that is, including the contents specified in the present application but not excluding other contents.

[0033] The present application provides a method for increasing the yield of 3-methylpyridine, a byproduct in the process of synthesizing pyridine base. The method specifically comprises adding a three-carbon compound with an aldehyde group to the reaction raw material for synthesizing pyridine base.

[0034] The present application also provides a method for synthesizing a pyridine base. The method specifically comprises the following steps:

[0035] Prepare the reaction raw materials for synthesizing pyridine base as required, and add the three-carbon compound with aldehyde group to the reaction raw materials according to the above method;

[0036] Under the action of a pyridine base synthesis catalyst, the reaction is carried out in an ammonia environment at a temperature of 350-500° C., and the reaction product is cooled and collected to obtain the reaction product pyridine base and the reaction by-product 3-methylpyridine.

[0037] In a specific embodiment, a method for synthesizing a pyridine base comprises the following steps:

[0038] (1) Formaldehyde and acetaldehyde are prepared in a weight ratio of (1-3):1, and a three-carbon compound with an aldehyde group is added in an amount of 10-50wt.%.

[0039] (2) Load 100-150g of pyridine base synthesis catalyst and control the feed mass space velocity to 0.3-1h -1 .

[0040] (3) Raise the temperature of the heater and preheater to 350-500°C, replace the system with nitrogen, and then introduce ammonia at 1-5 L / min for reaction. Connect a condenser to the reaction system to cool and collect the reaction product. The cooling temperature is (-15) to (-5)°C.

[0041] (4) During the reaction, samples were taken every hour and analyzed using an Agilent 7820 gas chromatograph with TCD detector to record the contents of pyridine, 3-methylpyridine, and 2-methylpyridine.

[0042] (5) Sampling and analysis are performed until the content of the reaction product and the reaction by-product decreases significantly, and then the reaction is stopped. The reaction time is 5-10 hours. After the reaction is stopped, the pyridine base synthesis catalyst is removed and regenerated.

[0043] In order to make the purpose, technical scheme and advantages of the present application clearer, the technical scheme in the embodiments of the present application will be clearly and completely described below. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without making creative work belong to the scope of protection of the present application. The embodiments described below are exemplary and are only used to explain the present application, and cannot be interpreted as limiting the present application.

[0044] If no specific techniques or conditions are specified in the examples, the techniques or conditions described in the literature in the field or the product instructions are used. If no manufacturer is specified for the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0045] The present application is further described in detail below in combination with embodiments, comparative examples and test results.

[0046] Comparative Example

[0047] This comparative example provides a method for synthesizing pyridine base.

[0048] The synthesis method specifically comprises the following steps:

[0049] (1) Formaldehyde and acetaldehyde are prepared in a weight ratio of 2:1.

[0050] (2) The raw material tank was filled with nitrogen to maintain pressure, and 150 g of pyridine catalyst was loaded from the top of the fluidized bed reactor.

[0051] (3) Heat the heater and preheater to 400°C, replace the system with nitrogen, turn off the nitrogen, feed ammonia at 2L / min, and start the feed reaction after the system stabilizes. The feed mass space velocity is 0.5h -1 The reaction system was followed by a condenser to cool and collect the reaction product. The cooling temperature was -10°C.

[0052] (4) During the reaction, samples were taken every hour and analyzed using an Agilent 7820 gas chromatograph TCD detector to record the contents of pyridine, 3-methylpyridine and 2-methylpyridine and calculate the molar yield.

[0053] (5) Sampling and analysis were performed until the contents of the reaction product and the reaction by-product decreased significantly, and then the reaction was stopped. The reaction time was 8 hours. After the reaction was stopped, the pyridine base synthesis catalyst was removed and regenerated.

[0054] The analysis of the product by Agilent 7820 gas chromatograph TCD detector showed that the molar ratio of the reaction product pyridine to the reaction byproduct 3-methylpyridine was 8:2. The molar yield was calculated to be about 77%.

[0055] Examples 1-5

[0056] Example 1-5 provides a method for synthesizing a pyridine base to obtain 3-methylpyridine, a by-product of the reaction.

[0057] The difference between the above synthesis method and the comparative example is that different amounts of propionaldehyde are added to the reaction raw materials, as shown in Table 1. The rest of the operation steps are consistent with those of Comparative Example 1.

[0058] The differences between the above embodiment and the comparative example are as follows:

[0059] The difference between Examples 1-5 and the comparative example is that 10-50 wt. % of propionaldehyde is added to the reaction raw materials respectively.

[0060] Table 1 Synthesis methods and products of various embodiments and comparative examples

[0061]

[0062] Test results

[0063] The products obtained by the synthesis methods provided in the above examples and comparative examples are specifically shown in Table 1.

[0064] As can be seen from Table 1, the present application has respectively tested the process of synthesizing pyridine base by adding propionaldehyde in different proportions (10wt.%, 20wt.%, 30wt.%, 40wt.%, 50wt.%) to the reaction raw materials. From the test results, it can be seen that with the increase in the amount of the above-mentioned materials added, the output of the reaction product pyridine base decreases, while the output of the reaction by-product 3-methylpyridine increases. It is finally concluded that when the amount of propionaldehyde added to the reaction raw materials is 30wt.%, the molar ratio of the reaction product pyridine base to the reaction by-product 3-methylpyridine is 8:5.2, and the molar yield is about 79%. By using the method provided by the present application, the production capacity of 3-methylpyridine is significantly improved.

[0065] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example" or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0066] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit it. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for increasing the yield of 3-methylpyridine, a by-product in the synthesis process of pyridine base, It is characterized in that A three-carbon compound with an aldehyde group is added to the reaction raw materials for synthesizing pyridine base.

2. The method according to claim 1, It is characterized in that The amount of the three-carbon compound with an aldehyde group added to the reaction raw material is 10-50wt.%; Optionally, the amount of the three-carbon compound with an aldehyde group added to the reaction raw material is 20-40wt.%; Optionally, the tricarbon compound with an aldehyde group is added in an amount of 30 wt.% in the reaction raw materials.

3. The method according to claim 1, It is characterized in that The three-carbon compound having an aldehyde group includes propionaldehyde.

4. The method according to claim 1, It is characterized in that The reaction raw materials are formaldehyde and acetaldehyde.

5. The method according to claim 4, It is characterized in that The weight ratio of the formaldehyde to the acetaldehyde is (1-3):

1.

6. A method for synthesizing a pyridine base, It is characterized in that The synthesis method specifically comprises the following steps: Prepare the reaction raw materials for synthesizing pyridine base as required, and add the three-carbon compound with aldehyde group to the reaction raw materials according to the method described in any one of claims 1 to 5; Under the action of a pyridine base synthesis catalyst, the reaction is carried out in an ammonia environment at a temperature of 350-500° C., and the reaction product is cooled and collected to obtain the reaction product pyridine base and the reaction by-product 3-methylpyridine.

7. The synthesis method according to claim 6, It is characterized in that The cooling temperature is (-15)~(-5)°C.

8. The synthesis method according to claim 6, It is characterized in that During the reaction, samples were taken and analyzed every hour, and the reaction was stopped when the contents of the reaction product and the reaction by-product decreased significantly; Optionally, the reaction time is 5-10 hours.

9. The synthesis method according to claim 6, It is characterized in that The usage of the pyridine base synthesis catalyst is 100-150g, and the feed mass space velocity is 0.3-1h -1 .

10. The synthesis method according to claim 6, It is characterized in that The regeneration temperature of the pyridine base synthesis catalyst is 400-600° C., and the calcination time is 2-8 hours.

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