Process and apparatus for the synthesis of alkyl nitrites

Abstract

The application relates to the technical field of nitrite synthesis, and discloses a synthesis method and a synthesis device of alkyl nitrite. The synthesis method comprises the following steps: firstly, mixing gaseous nitric oxide and gaseous oxygen to obtain a mixture through a first reaction; and then, mixing the mixture with alkyl alcohol to obtain alkyl nitrite through a second reaction. The synthesis method greatly shortens the reaction time, increases the yield of alkyl nitrite, does not have a complicated post-treatment process and a large amount of by-product nitric acid, and is beneficial to cost saving and time saving.

Description

Technical Field

[0001] This invention relates to the field of nitrite ester synthesis technology, specifically to a method and apparatus for synthesizing alkyl nitrite esters. Background Technology

[0002] The molecular formula of nitrite is C x H 2x+1 NO2. Nitrite esters, as highly efficient and green multifunctional reagents, can participate widely in various organic transformations, such as oxidation, diazotization, nitrosation, nitration, and oxime reactions. Tert-butyl nitrite can also be used as an intermediate for hypertensive agents, rocket fuel, and in the preparation of aryl azides from aromatic amines with azidotrimethylsilane. Although it has been widely used in organic synthesis, it still has great potential for development. While nitrite esters have a wide range of applications, their synthesis is not simple. Currently, the most common methods are the reaction of chloroalkanes with silver nitrate in diethyl ether, or the reaction of the corresponding alcohols with sodium nitrite and sulfuric acid.

[0003] Currently, the main methods for synthesizing alkyl nitrites include the following:

[0004] (1) Synthesis of alkyl nitrite esters: The corresponding alcohol is added dropwise to an ice-water solution of sulfuric acid at 0°C, followed by an aqueous solution of nitrite over 1 hour. The reaction mixture is heated to room temperature and stirred overnight. After extraction and separation, the organic phase is washed three times with water and three times with saturated sodium bicarbonate, and then distilled to obtain pure alkyl nitrite esters. This method requires a long reaction time and complex post-processing steps, which is not conducive to further development of the process.

[0005] (2) The method of preparing the product by reacting chloroalkanes with silver nitrate in diethyl ether requires a large amount of chloroalkanes and silver nitrate, which is too costly and the source of raw materials is not widely available.

[0006] (3) The method of preparing nitrites by reacting alcohol with sodium nitrite and sulfuric acid also has many disadvantages. First, the use of strong acidic substances places extremely high demands on the reaction equipment, and the post-treatment neutralization process is time-consuming and labor-intensive, which undoubtedly increases the cost of this method. Nitrites are carcinogenic substances, and their safety during use needs to be fully considered, while also taking into account environmental protection issues.

[0007] CN104411677A discloses a method for manufacturing nitrite esters, as well as a method for manufacturing dialkyl oxalate and dialkyl carbonate esters. The method includes: supplying ethanol to the upper part of a reaction tower for nitrite ester production and allowing it to flow downwards from the upper part of the tower; and supplying nitric oxide and oxygen, or a mixture thereof, to the lower part of the reaction tower, causing the nitric oxide, oxygen, and ethanol to react to generate nitrite esters. During the synthesis of ethyl nitrite esters, a large amount of nitric acid is generated. This may be because nitric oxide and oxygen are simultaneously introduced into the ethanol system with a short residence time, leading to unreacted nitric oxide and oxygen reacting with the water produced in the reaction to generate a large amount of nitric acid. It is foreseeable that the yield of ethyl nitrite esters synthesized by this method will not be very high. Finally, the optimal temperature conditions for this reaction even reach 60°C. Nitrite esters are relatively unstable, especially ethyl nitrite esters, which are easily decomposed by heat, further increasing the amount of nitric acid and reducing the yield of the target product, nitrite esters. Moreover, the production process generates a large amount of highly toxic "yellow fumes," i.e., nitric oxide, posing a significant danger and making the operation cumbersome.

[0008] Therefore, there is an urgent need for a simple method and apparatus for synthesizing alkyl nitrites. Summary of the Invention

[0009] The purpose of this invention is to overcome the problems of low yield, complex preparation steps, and cumbersome operation of existing technologies for alkyl nitrites, and to provide a method and apparatus for synthesizing alkyl nitrites. This method has the characteristics of high yield of alkyl nitrites, simple preparation steps, and easy operation.

[0010] To achieve the above objectives, the present invention provides a method for synthesizing alkyl nitrites, the method comprising: firstly mixing gaseous nitric oxide and gaseous oxygen, and then reacting them in a first reaction to obtain a mixture; and then mixing the mixture with an alkyl alcohol in a second reaction to obtain alkyl nitrites.

[0011] Another aspect of the present invention provides an apparatus for synthesizing alkyl nitrites, the apparatus comprising a tubular reactor, a first static mixer and a second static mixer, wherein the second static mixer is located between the tubular reactor and the first static mixer; the first static mixer is connected to a first storage container for storing gaseous nitric oxide and a second storage container for storing gaseous oxygen, and the second static mixer is connected to a third storage container for storing alkyl alcohols.

[0012] The beneficial technical effects achieved by the present invention through the above technical solution are as follows:

[0013] 1) This invention first reacts gaseous nitric oxide and gaseous oxygen to combine them into a mixture of nitric oxide and nitrogen dioxide. This mixture is then reacted with an alkyl alcohol to generate alkyl nitrite esters. The synthesis method of this invention can be completed at room temperature and in a short time, greatly shortening the reaction time. The yield and purity of the obtained alkyl nitrite esters are very high. There are no complicated post-processing steps or large amounts of nitric acid byproducts generated. The operation is simple and quick, which helps to save costs and time.

[0014] 2) The method of the present invention uses alkyl alcohols, which are relatively inexpensive products in industry, as starting materials. Compared with chloroalkanes, they are more widely available and cheaper, and do not require the use of expensive chemicals such as silver nitrate.

[0015] 3) The method of the present invention avoids the use of these two types of substances, which increase costs and pose safety hazards and environmental pollution, compared to the system of concentrated sulfuric acid and nitrite. Attached Figure Description

[0016] Figure 1 This is an apparatus for synthesizing alkyl nitrites provided in one embodiment of the present invention. Detailed Implementation

[0017] The endpoints and any values ​​of the ranges disclosed herein 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 the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0018] The first aspect of the present invention provides a method for synthesizing alkyl nitrites, the method comprising: firstly mixing gaseous nitric oxide and gaseous oxygen, and then reacting them in a first reaction to obtain a mixture; then mixing the mixture with an alkyl alcohol in a second reaction to obtain an alkyl nitrite.

[0019] The synthesis method specifically includes: first, mixing gaseous nitric oxide and gaseous oxygen in a first mixture, followed by a first reaction to obtain a first mixture; then, mixing the first mixture with an alkyl alcohol in a second mixture to obtain a second mixture; reacting the second mixture and then performing post-treatment to obtain an alkyl nitrite ester.

[0020] This invention first reacts gaseous nitric oxide and gaseous oxygen, causing excess nitric oxide to combine with oxygen to form nitrogen dioxide, resulting in a mixture of nitrogen dioxide and the remaining nitric oxide. This mixture is then reacted with an alkyl alcohol to produce an alkyl nitrite ester. This reaction can be completed at room temperature and within a short time; the operation is simple and rapid, and the yield and purity of the obtained alkyl nitrite ester are both high.

[0021] The synthesis method of the present invention facilitates the full reaction of the mixture with the alcohol, greatly shortens the reaction time, increases the yield of alkyl nitrite esters, and avoids complicated post-processing and the generation of a large amount of nitric acid byproducts, which helps to save costs and time.

[0022] In some embodiments of the present invention, the molar ratio of the alkyl alcohol, gaseous nitric oxide, and gaseous oxygen is 4:0.8-1.5:0.3-0.5, for example 4:0.8:0.3, 4:0.8:0.4, 4:0.8:0.5, 4:0.9:0.3, 4:1:0.3, 4:1.1:0.3, 4:1.2:0.3, 4:1.3:0.3, 4:1.4:0.3, 4:1.5:0.3, 4:0.8:0.4, 4:0.9:0.4, 4:1:0.4, 4:1.1:0.4, 4:1.2:0.5, 4:1.3:0.5, 4:1.4:0.5, 4:1.5:0.5, and any value within any range of any two values.

[0023] In some embodiments of the present invention, the alkyl alcohol has the structural formula R-OH, wherein R is a C1-C8 alkyl group.

[0024] In some embodiments of the present invention, the alkyl alcohol is selected from one or more of methanol, ethanol, propanol, tert-butanol, isoamyl alcohol, cyclohexanol, heptanol, and octanol.

[0025] In some embodiments of the present invention, the reaction temperature is -20°C to 5°C, preferably -5°C to 0°C, and the reaction time is 1-2 min.

[0026] In some embodiments of the present invention, the reaction is carried out in a tubular reactor, which is sequentially connected to a second static mixer and a first static mixer, the first static mixer being connected to a first storage container and a second storage container, and the second static mixer being connected to a third storage container; wherein gaseous nitric oxide is stored in the first storage container, gaseous oxygen is stored in the second storage container, and alkyl alcohol is stored in the third storage container.

[0027] In this invention, a tubular reactor is a reactor composed of tubes, and a flow reactor is a reactor in which the reaction liquid flows forward in the tubes during the reaction process.

[0028] In some embodiments of the present invention, the tubular reactor has a diameter of 1-10 mm and a length of 1-50 m.

[0029] In some embodiments of the present invention, the yield of the alkyl nitrite is not less than 90%.

[0030] In some embodiments of the present invention, the yield of nitric acid is no more than 5%, preferably less than 0.1%, during the reaction.

[0031] In this invention, nitric acid was not detected in the product, therefore it can be inferred that the method of this invention produces almost no nitric acid, and preferably the yield of nitric acid is 0.

[0032] A second aspect of the present invention provides an apparatus for synthesizing alkyl nitrite esters, such as... Figure 1 As shown, the synthesis apparatus includes a tubular reactor 1, a first static mixer 2, and a second static mixer 3, wherein the second static mixer 3 is located between the tubular reactor 1 and the first static mixer 2, the first static mixer 2 is connected to a first storage tank 4 for storing gaseous nitric oxide and a second storage tank 5 for storing gaseous oxygen, and the second static mixer 3 is connected to a third storage tank 6 for storing alkyl alcohols.

[0033] In some embodiments of the present invention, the diameter of the tubular reactor 1 is 1-10 mm and the length is 1-50 m.

[0034] In some embodiments of the present invention, the synthesis apparatus further includes a separating tank 7, which is connected to the tubular reactor 1.

[0035] In this invention, the feed liquid generated after the reaction in the tubular reactor enters the separatory tank, where it quickly separates into an upper alkyl nitrite phase and a lower aqueous phase. The lower aqueous phase is discharged from the bottom of the separatory tank, and the upper alkyl nitrite phase is extracted from the top of the separatory tank and then subjected to product distillation to obtain the alkyl nitrite product.

[0036] According to a particularly preferred embodiment of the present invention, a method for synthesizing alkyl nitrites using a tubular reactor, employing, as... Figure 1 The apparatus shown specifically includes the following steps:

[0037] (1) Store gaseous nitric oxide in the first storage container 4, gaseous oxygen in the second storage container 5, and alkyl alcohol in the third storage container 6;

[0038] (2) The liquids in the first storage container 4 and the second storage container 5 are continuously transported to the first static mixer 2 by the first metering pump P1 and the second metering pump P2 respectively for the first mixing to obtain the first mixture;

[0039] (3) The first mixture is transported to the second static mixer 3, and the liquid in the third storage tank 6 is continuously transported to the second static mixer 3 via the third metering pump P3, so that it is mixed with the first mixture in the second static mixer 3. At the same time, the first throttle valve, the second throttle valve and the third throttle valve are controlled so that the feed molar ratio of alkyl alcohol, gaseous nitric oxide and gaseous oxygen is 4:0.8-1.5:0.3-0.5, to obtain the second mixture;

[0040] (4) The second mixture is continuously fed into a tubular reactor 1 with a pipe length of 1-50m and a pipe diameter of 1-10mm. The reaction is carried out at -20℃ to 5℃ (preferably -5℃ to 0℃). After a residence time of 1-2min, the reaction liquid enters the separatory tank 7. The liquid in the separatory tank is then post-treated to obtain alkyl nitrite.

[0041] In step (4), the post-processing steps include: rapidly separating the reacted liquid into an upper alkyl nitrite phase and a lower aqueous phase in a separatory tank, discharging the lower aqueous phase from the bottom of the separatory tank, and extracting the upper alkyl nitrite phase from the top of the separatory tank for product distillation to obtain the alkyl nitrite product.

[0042] The method of the present invention is a pipeline-based continuous preparation method for alkyl nitrite esters.

[0043] To further understand the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0044] Unless otherwise specified, all reagents involved in the embodiments of this invention are commercially available products and can be purchased through commercial channels.

[0045] Example 1

[0046] Gaseous nitric oxide is stored in the first storage container, gaseous oxygen is stored in the second storage container, and propanol is stored in the third storage container.

[0047] The liquid in the first reservoir and the liquid in the second reservoir are continuously pumped into the first static mixer by the first metering pump and the second metering pump, respectively, and the first mixing is carried out in the first static mixer to obtain the first mixture;

[0048] The first mixture is fed into the second static mixer, and the liquid in the third reservoir is continuously fed into the second static mixer via the third metering pump, so that it is mixed with the first mixture in the second static mixer. At the same time, the first throttle valve, the second throttle valve and the third throttle valve are controlled so that the feed molar ratio of propanol, gaseous nitric oxide and gaseous oxygen is 4:1:0.5, to obtain the second mixture.

[0049] The second mixture was fed into a tubular reactor with a diameter of 4 mm and a length of 40 m, and the reaction was carried out at -5 °C. After a residence time of 60 s, the reaction solution was transferred into a separatory tank to obtain 11.2 g of propyl nitrite.

[0050] Tests showed that the yield of propyl nitrite was 95%, the purity was 97%, and no nitric acid was detected.

[0051] Example 2

[0052] Gaseous nitric oxide is stored in the first storage container, gaseous oxygen is stored in the second storage container, and tert-butanol is stored in the third storage container.

[0053] The liquid in the first reservoir and the liquid in the second reservoir are continuously pumped into the first static mixer by the first metering pump and the second metering pump, respectively, and the first mixing is carried out in the first static mixer to obtain the first mixture;

[0054] The first mixture is fed into the second static mixer, and the liquid in the third reservoir is continuously fed into the second static mixer via the third metering pump, so that it is mixed with the first mixture in the second static mixer. At the same time, the first throttle valve, the second throttle valve and the third throttle valve are controlled so that the feed molar ratio of tert-butanol, gaseous nitric oxide and gaseous oxygen is 4:1:0.3, so as to obtain the second mixture.

[0055] The second mixture was fed into a tubular reactor with a diameter of 4 mm and a length of 40 m, and reacted at -0 °C. After a residence time of 60 s, the reaction solution was transferred to a separatory tank to obtain 13 g of tert-butyl nitrite.

[0056] The yield of tert-butyl nitrite was 93%, the purity was 95%, and no nitric acid was detected.

[0057] Example 3

[0058] Gaseous nitric oxide is stored in the first storage container, gaseous oxygen is stored in the second storage container, and cyclohexanol is stored in the third storage container.

[0059] The liquid in the first reservoir and the liquid in the second reservoir are continuously pumped into the first static mixer by the first metering pump and the second metering pump, respectively, and the first mixing is carried out in the first static mixer to obtain the first mixture;

[0060] The first mixture is fed into the second static mixer, and the liquid in the third reservoir is continuously fed into the second static mixer via the third metering pump, so that it is mixed with the first mixture in the second static mixer. At the same time, the first throttle valve, the second throttle valve and the third throttle valve are controlled so that the feed molar ratio of cyclohexanol, gaseous nitric oxide and gaseous oxygen is 4:1.1:0.5, so as to obtain the second mixture.

[0061] The second mixture was fed into a tubular reactor with a diameter of 10 mm and a length of 20 m, and reacted at 5 °C. After a residence time of 120 s, the reaction solution was transferred to a separatory tank to obtain 15 g of cyclohexyl nitrite.

[0062] The yield of cyclohexyl nitrite was 90%, the purity was 95%, and the yield of nitric acid was 2%.

[0063] Example 4

[0064] Gaseous nitric oxide is stored in the first storage container, gaseous oxygen is stored in the second storage container, and isoamyl alcohol is stored in the third storage container.

[0065] The liquid in the first reservoir and the liquid in the second reservoir are continuously pumped into the first static mixer by the first metering pump and the second metering pump, respectively, and the first mixing is carried out in the first static mixer to obtain the first mixture;

[0066] The first mixture is fed into the second static mixer, and the liquid in the third reservoir is continuously fed into the second static mixer via the third metering pump, so that it is mixed with the first mixture in the second static mixer. At the same time, the first throttle valve, the second throttle valve and the third throttle valve are controlled so that the feed molar ratio of isoamyl alcohol, gaseous nitric oxide and gaseous oxygen is 4:0.8:0.5, so as to obtain the second mixture.

[0067] The second mixture was fed into a tubular reactor with a diameter of 5 mm and a length of 30 m, and reacted at -10 °C. After a residence time of 80 s, the reaction solution was transferred to a separatory tank to obtain 11 g of amyl nitrite.

[0068] The yield of isoamyl nitrite was 91%, the purity was 96%, and the yield of nitric acid was 1%.

[0069] Example 5

[0070] Gaseous nitric oxide is stored in the first storage container, gaseous oxygen is stored in the second storage container, and ethanol is stored in the third storage container.

[0071] The liquid in the first reservoir and the liquid in the second reservoir are continuously pumped into the first static mixer by the first metering pump and the second metering pump, respectively, and the first mixing is carried out in the first static mixer to obtain the first mixture;

[0072] The first mixture is fed into the second static mixer, and the liquid in the third reservoir is continuously fed into the second static mixer via the third metering pump, so that it is mixed with the first mixture in the second static mixer. At the same time, the first throttle valve, the second throttle valve and the third throttle valve are controlled so that the feed molar ratio of isoamyl alcohol, gaseous nitric oxide and gaseous oxygen is 4:1.5:0.4, so as to obtain the second mixture.

[0073] The second mixture was fed into a tubular reactor with a diameter of 4 mm and a length of 50 m, and reacted at -10 °C. After a residence time of 80 s, the reaction solution was transferred to a separatory tank to obtain 14.3 g of ethyl nitrite.

[0074] Tests showed that the yield of ethyl nitrite was 95%, the purity was 95%, and the yield of nitric acid was 1%.

[0075] Example 6

[0076] Ethyl nitrite was prepared according to the method of Example 5, except that the second mixture was fed into a tubular reactor and reacted at -0°C.

[0077] Tests showed that the yield of ethyl nitrite was 92%, the purity was 95%, and the yield of nitric acid was 5%.

[0078] Example 7

[0079] Ethyl nitrite was prepared according to the method of Example 5, except that the second mixture was fed into a tubular reactor with a diameter of 6 mm and a length of 50 m.

[0080] Tests showed that the yield of ethyl nitrite was 90%, the purity was 95%, and the yield of nitric acid was 4%.

[0081] Example 8

[0082] Ethyl nitrite was prepared according to the method of Example 5, except that the second mixture was fed into a tubular reactor with a diameter of 1 mm and a length of 50 m.

[0083] Tests showed that the yield of ethyl nitrite was 93%, the purity was 95%, and the yield of nitric acid was 1%.

[0084] Example 9

[0085] Ethyl nitrite was prepared according to the method of Example 5, except that the second mixture was fed into a tubular reactor with a diameter of 10 mm and a length of 30 m.

[0086] Tests showed that the yield of ethyl nitrite was 90%, the purity was 95%, and the yield of nitric acid was 4%.

[0087] Comparative Example 1

[0088] Ethyl nitrite was synthesized according to the method of Example 5, except that gaseous nitric oxide, gaseous oxygen and ethanol were directly fed into a tubular reactor for reaction, wherein the feed molar ratio of ethanol, gaseous nitric oxide and gaseous oxygen was 4:1.5:0.4.

[0089] The yield of ethyl nitrite was 40%, the purity was 95%, and the yield of nitric acid was 25%.

[0090] Comparative Example 2

[0091] Nitrite esters are prepared according to method CN104411677A. Ethanol is supplied to the upper part of a reaction tower for nitrite ester production and allowed to flow down from the upper part of the tower to the lower part. Nitric oxide and oxygen, or a mixture thereof, are supplied to the lower part of the reaction tower, and the nitric oxide, oxygen, and ethanol react to produce nitrite esters. The feed molar ratio of ethanol, nitric oxide, and oxygen is 4:1.5:0.4, and the reaction temperature in the reaction tower is 60°C.

[0092] Tests showed that the yield of ethyl nitrite was 45%, the purity was 95%, and the yield of nitric acid was 25%.

[0093] The results above show that the alkyl nitrite esters prepared by the method of the present invention have high yield and purity.

[0094] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for synthesizing alkyl nitrites, characterized in that, The synthesis method includes: first, mixing gaseous nitric oxide and gaseous oxygen in a first mixture and undergoing a first reaction to obtain a mixture; then, mixing the mixture with an alkyl alcohol in a second mixture and undergoing a second reaction to obtain an alkyl nitrite ester.

2. The synthesis method according to claim 1, wherein, The molar ratio of the alkyl alcohol, gaseous nitric oxide, and gaseous oxygen is 4:0.8-1.5:0.3-0.

5.

3. The synthesis method according to claim 1 or 2, wherein, The alkyl alcohol has the structural formula R-OH, where R is a C1-C8 alkyl group.

4. The synthesis method according to claim 3, wherein, The alkyl alcohol is selected from one or more of methanol, ethanol, propanol, tert-butanol, isoamyl alcohol, cyclohexanol, heptanol, and octanol.

5. The synthesis method according to any one of claims 1-4, wherein, The reaction temperature is -20°C to 5°C, preferably -5°C to 0°C, and the reaction time is 1-2 minutes.

6. The synthesis method according to any one of claims 1-5, wherein, The reaction is carried out in a tubular reactor, which is connected in sequence to a second static mixer and a first static mixer. The first static mixer is connected to a first storage container and a second storage container, and the second static mixer is connected to a third storage container. Gaseous nitric oxide is stored in the first storage container, gaseous oxygen is stored in the second storage container, and alkyl alcohol is stored in the third storage container. Preferably, the tubular reactor has a diameter of 1-10 mm and a length of 1-50 m.

7. The synthesis method according to any one of claims 1-6, wherein, The yield of the alkyl nitrite is not less than 90%; And / or, during the reaction, the yield of nitric acid is no more than 5%.

8. An apparatus for synthesizing alkyl nitrite esters, characterized in that, The synthesis apparatus includes a tubular reactor, a first static mixer, and a second static mixer, wherein the second static mixer is located between the tubular reactor and the first static mixer; the first static mixer is connected to a first storage container for storing gaseous nitric oxide and a second storage container for storing gaseous oxygen, and the second static mixer is connected to a third storage container for storing alkyl alcohols.

9. The synthesis apparatus according to claim 8, wherein, The tubular reactor has a diameter of 1-10 mm and a length of 1-50 m.

10. The synthesis apparatus according to claim 8 or 9, wherein, The synthesis apparatus also includes a separatory tank, which is connected to the tubular reactor.

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