Process for the preparation of isooctyl nitrate and its use

Abstract

The present application relates to the field of micro-channel reactor synthesis, and discloses a preparation method of isooctyl nitrate and application thereof.The preparation method of isooctyl nitrate comprises the following steps: 1) a step of contacting acid and isooctyl alcohol in one or more reaction modules; and 2) a step of purifying the reaction product to obtain isooctyl nitrate, wherein the reaction module comprises a micro-channel reactor and a tubular reactor connected in sequence, and the acid comprises sulfuric acid and nitric acid.The preparation method of isooctyl nitrate has the characteristics of high isooctyl alcohol conversion rate, high product purity, small pressure drop of the reaction system and large production capacity.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of micro-channel reactor synthesis, in particular to a preparation method of isooctyl nitrate and application thereof. BACKGROUND

[0002] Isooctyl nitrate is an important diesel additive. Traditional production of isooctyl nitrate is mostly carried out in a tank reactor, and the reaction process is difficult to control, the heat is concentrated, and the process is highly dangerous. The micro-channel reactor is a new technology that has developed rapidly in recent years, and due to its unique characteristic size, it is suitable for processes with large heat release, fast reaction rate, and high production process danger. In order to further improve the purity of the product and the conversion rate of the raw material, a new preparation method needs to be further developed. SUMMARY

[0003] The purpose of the present application is to provide a preparation method of isooctyl nitrate and application thereof, which has the characteristics of high conversion rate of isooctyl alcohol, high purity of product, small pressure drop of reaction system and large production capacity.

[0004] In order to achieve the above-mentioned purpose, the present application provides a preparation method of isooctyl nitrate, which comprises the following steps:

[0005] 1) a step of introducing acid and isooctyl alcohol into one or more reaction modules for contact reaction;

[0006] 2) a step of purifying the reaction product to obtain isooctyl nitrate,

[0007] wherein the reaction module comprises a micro-channel reactor and a tubular reactor connected in sequence,

[0008] the acid comprises sulfuric acid and nitric acid.

[0009] Preferably, the acid is introduced in the following mode A) and / or B):

[0010] A) the sulfuric acid and the nitric acid are mixed in a molar ratio of 1.5-2.5:1 to obtain a mixed acid, which is then introduced into the reaction module, and the molar ratio of the mixed acid to the isooctyl alcohol is 1.0-1.5:1 based on the nitric acid;

[0011] B) the sulfuric acid and the nitric acid are simultaneously introduced into the reaction module in a molar ratio of 1.5-2.5:1, and the molar ratio of the nitric acid to the isooctyl alcohol is 1.0-1.5:1.

[0012] Preferably, in mode A), the molar ratio of sulfuric acid to nitric acid in the mixed acid is 1.5-2.3:1;

[0013] Preferably, in mode A), the content of water in the mixed acid is 8-18 mass%.

[0014] Preferably, in the mode B), sulfuric acid and nitric acid are simultaneously introduced into the reaction module according to a molar ratio of 1.5-2.3:1.

[0015] Preferably, in the mode B), the content of water in the acid is 8-18 mass%.

[0016] Preferably, the reaction module is 1-10, preferably 1-8, more preferably 1-5.

[0017] Preferably, in the reaction module, the volume of the tubular reactor is 3-35 times, preferably 4-20 times, more preferably 4-10 times of the microchannel volume of the microchannel reactor.

[0018] Preferably, the conditions of the contact reaction include a reaction temperature of 30℃ or lower and a total reaction time of 30-400 seconds; more preferably, the conditions of the contact reaction include a reaction temperature of 5-30℃ and a total reaction time of 40-350 seconds.

[0019] Preferably, in the reaction module, the residence time of the microchannel reactor is 1-60 seconds and the residence time of the tubular reactor is 10-280 seconds; more preferably, in the reaction module, the residence time of the microchannel reactor is 3-30 seconds and the residence time of the tubular reactor is 10-200 seconds.

[0020] Preferably, in the step 2), the method of purification includes neutralization, washing and drying after separation of the aqueous phase and the organic phase.

[0021] Preferably, the method further includes a step of recovering waste acid in the aqueous phase.

[0022] Preferably, in the mode A), the molar ratio of the mixed acid to the isooctanol, calculated based on nitric acid, is 1.1-1.4:1.

[0023] Preferably, in the mode B), the molar ratio of the nitric acid to the isooctanol is 1.1-1.4:1.

[0024] The second aspect of the present application provides an application of the preparation method of the present application in the preparation of isooctyl nitrate.

[0025] Through the above technical solution, the preparation method of isooctyl nitrate provided by the present application can make the reactants fully mix and react, the conversion rate of isooctanol is high, and the byproduct is less. At the same time, the problem of large pressure drop and limited processing capacity when only using a microchannel reactor for reaction is avoided. Moreover, the method also reduces the circulation amount of waste acid and sulfuric acid, improves the economy and is more environmentally friendly. DETAILED DESCRIPTION

[0026] The endpoints of the ranges and any values disclosed herein are not limited to the precise values recited as the exact dimensions are not considered critical for the purposes of the application. The endpoints of the ranges and any values are provided as approximations only and are understood to encompass a range of values which are near the recited values. For values which are less than one, the endpoints of the ranges and any values are provided as approximations only and are understood to encompass a range of values which are near the recited values.

[0027] The first aspect of the present application provides a method for preparing isooctyl nitrate, characterized in comprising the following steps:

[0028] 1) a step of feeding an acid and isooctyl alcohol into one or more reaction modules for contact reaction;

[0029] 2) a step of purifying the reaction product to obtain isooctyl nitrate,

[0030] wherein the reaction module comprises a microchannel reactor and a tubular reactor connected in sequence,

[0031] the acid comprises sulfuric acid and nitric acid.

[0032] The inventors of the present application have found that when a microchannel reactor and a tubular reactor are used in sequence to prepare isooctyl nitrate, the reactants can be fully mixed and reacted, the conversion rate of isooctyl alcohol and the purity of the product can be improved, and the problems of large pressure drop and limited capacity when only a microchannel reactor is used for reaction can be avoided.

[0033] According to the present application, the acid can be fed into the reaction module by mixing sulfuric acid and nitric acid before feeding, or by feeding sulfuric acid and nitric acid into the microchannel reactor of the reaction module and then mixing, therefore, preferably, the acid is fed into the reaction module by the following methods A) and / or B):

[0034] A) the sulfuric acid and the nitric acid are mixed in a molar ratio of 1.5-2.5:1 to obtain a mixed acid, and the mixed acid is fed into the reaction module, and the molar ratio of the mixed acid to the isooctyl alcohol, calculated based on the nitric acid, is 1.0-1.5:1;

[0035] B) the sulfuric acid and the nitric acid are fed into the reaction module at the same time in a molar ratio of 1.5-2.5:1, and the molar ratio of the nitric acid to the isooctyl alcohol is 1.0-1.5:1.

[0036] According to the present application, in order to further improve the conversion rate of isooctyl alcohol and the purity of the product, preferably, in method A), the molar ratio of sulfuric acid to nitric acid in the mixed acid is 1.5-2.3:1; more preferably, in method A), the molar ratio of sulfuric acid to nitric acid in the mixed acid is 1.7-2.2:1; further preferably, in method A), the molar ratio of sulfuric acid to nitric acid in the mixed acid is 1.8-2.2:1.

[0037] According to the present application, in order to improve the reaction rate and reduce side reactions, preferably, in mode A), the content of water in the mixed acid is 8-18 mass%; more preferably, the content of water in the mixed acid is 8-15 mass%; further preferably, the content of water in the mixed acid is 8-12 mass%.

[0038] According to the present application, in order to further improve the conversion rate of isooctanol and the purity of the product, preferably, in mode B), sulfuric acid and nitric acid are simultaneously introduced into the reaction module at a molar ratio of 1.5-2.3:1; more preferably, in mode B), sulfuric acid and nitric acid are simultaneously introduced into the reaction module at a molar ratio of 1.7-2.2:1; preferably, in mode B), sulfuric acid and nitric acid are simultaneously introduced into the reaction module at a molar ratio of 1.8-2.2:1.

[0039] According to the present application, in order to improve the reaction rate and reduce side reactions, preferably, in mode B), the content of water in the acid is 8-18 mass%; more preferably, the content of water in the acid is 8-15 mass% or less; further preferably, the content of water in the acid is 8-12 mass%.

[0040] According to the present application, when the ratio of nitric acid to isooctanol in the reaction module is within a specific range, the conversion rate of isooctanol and the purity of the product can be further improved, and the amount of waste acid and sulfuric acid circulating can also be reduced, preferably, in mode A), the molar ratio of the mixed acid to the isooctanol calculated based on nitric acid is 1.1-1.4:1; more preferably, in mode A), the molar ratio of the mixed acid to the isooctanol calculated based on nitric acid is 1.1-1.3:1.

[0041] Preferably, in mode B), the molar ratio of the nitric acid to the isooctanol is 1.1-1.4:1; more preferably, in mode B), the molar ratio of the nitric acid to the isooctanol is 1.1-1.3:1.

[0042] According to the present application, preferably, the reaction module group of the micro-channel reactor is a plate-type micro-channel reactor sheet; more preferably, the reaction module group of the micro-channel reactor is one or more of tubular straight-through channel structure, heart-shaped channel structure, and Zig-zag channel structure.

[0043] According to the present application, the micro-channel reactor can be obtained by commercial purchase, for example, a micro-channel reactor purchased from Shandong Haomai Group, a micro-channel reactor purchased from Maynus Group, USA, a micro-channel reactor purchased from Effine Chemical Technology (Shanghai) Co., Ltd., etc.

[0044] In the present application, by using the reaction module, the reaction liquid first passes through the micro-channel reactor, and the reaction liquid is in a fully mixed state in the micro-channel reactor, but the pressure drop is high, by using the tubular reactor, the pressure drop can be reduced, and the above-mentioned mixed state can also be maintained in the tubular reactor, so as to reduce the pressure drop and improve the processing capacity of the device.

[0045] Preferably, the reaction module is composed of a micro-channel reactor and a tubular reactor connected in sequence.

[0046] In the present application, the number of reaction modules is appropriately set, as long as sufficient reaction can be ensured, preferably, the number of reaction modules is 1-10, more preferably 1-8, and further preferably 1-5.

[0047] As the number of reaction modules, for example, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, etc. can be given.

[0048] According to the present application, preferably, in the reaction module, the volume of the tubular reactor is 3-35 times, preferably 4-20 times, and more preferably 4-10 times of the volume of the micro-channel of the micro-channel reactor.

[0049] According to the present application, preferably, the structure of the tubular reactor is a hollow circular tube or a circular tube with different structure fillers; more preferably, the tubular reactor is a hollow circular tube with a pipe diameter of 3-20 mm; further preferably, the tubular reactor is a hollow circular tube with a pipe diameter of 3-15 mm; more preferably, the tubular reactor is a hollow circular tube with a pipe diameter of 3-10 mm; more preferably, the tubular reactor is a hollow circular tube with a pipe diameter of 3-5 mm.

[0050] According to the present application, in order to improve the reaction rate while having higher product purity and isooctanol conversion rate, preferably, the conditions of the contact reaction include: the reaction temperature is 30℃ or lower, and the total reaction time is 30-400 seconds; more preferably, the conditions of the contact reaction include: the reaction temperature is 5-30℃, and the total reaction time is 40-350 seconds.

[0051] In order to further improve the reaction efficiency and to enable the reactants to be fully reacted in the tubular reactor in a fully mixed state so as to reduce the occurrence of side reactions, preferably, in the reaction module, the residence time of the microchannel reactor is 1-60 seconds and the residence time of the tubular reactor is 10-280 seconds; more preferably, in the reaction module, the residence time of the microchannel reactor is 3-30 seconds and the residence time of the tubular reactor is 10-200 seconds; further preferably, in the reaction module, the residence time of the microchannel reactor is 4-20 seconds and the residence time of the tubular reactor is 20-100 seconds; and more further preferably, in the reaction module, the residence time of the microchannel reactor is 5-10 seconds and the residence time of the tubular reactor is 20-50 seconds.

[0052] According to the present application, the method of purification in step 2) is not particularly limited and can be a method of purification commonly used in the art. In order to reduce the operation difficulty and the preparation cost, preferably, the method of purification comprises neutralization, washing and drying after separation of the aqueous phase and the organic phase.

[0053] The method of purification is not particularly limited and can be a method of purification commonly used in the art. In order to reduce the operation difficulty and the preparation cost, the method of purification comprises neutralization, washing and drying after separation of the aqueous phase and the organic phase.

[0054] According to the present application, the method of neutralization is not particularly limited and can be a method of neutralization commonly used in the art, for example, the neutralization can be performed by adding a base. The base can be, for example, one or more of sodium hydroxide, sodium carbonate and sodium bicarbonate, and is preferably sodium bicarbonate. The amount of the base can be adjusted as needed, provided that the pH value after addition of the base is 6.5-7.5, and is not particularly limited.

[0055] According to the present application, the method of washing is not particularly limited and can be a method of washing commonly used in the art, for example, the washing can be performed by using water.

[0056] According to the present application, the method of drying is not particularly limited and can be a method of drying commonly used in the art, for example, the drying can be heating drying and / or reduced pressure drying.

[0057] According to the present application, in order to reduce the waste discharge in the preparation process, preferably, the preparation method of the present application further comprises a step of recovering the waste acid in the aqueous phase. The method of recovering the waste acid is not particularly limited and can be a method of recovery commonly used in the art, for example, one or more of concentration, extraction, resin exchange, diffusion chromatography membrane, oxidation and crystallization.

[0058] The second aspect of the present application provides the use of the method of the present application in the preparation of isooctyl nitrate. The method for preparing isooctyl nitrate provided by the present application can make the reactants fully mix and react, the conversion rate of isooctyl alcohol is high, and the amount of by-product is small, and at the same time, the problem of large pressure drop and limited processing capacity when only using a micro-channel reactor for reaction is avoided. Moreover, the method also reduces the amount of waste acid and the circulation amount of sulfuric acid, improves the economy and is more environmentally friendly.

[0059] The present application will be described in detail below through examples, but the present application is not limited to the following examples only.

[0060] The micro-channel reactor used in the following examples is manufactured by Shandong Haomai Group, and the model is RMCS181003. The tubular reactor used is a hollow circular tube with an inner diameter of 3 mm (the volume is 8 times the volume of the micro-channels of the micro-channel reactor).

[0061] Example 1

[0062] (1) 98 mass% concentrated sulfuric acid and 68 mass% concentrated nitric acid were mixed in a molar ratio of sulfuric acid to nitric acid of 2:1 to obtain a mixed acid (the water content in the mixed acid was 11.5 mass%). The mixed acid and isooctyl alcohol were simultaneously pumped into the subsequent reactor in a molar ratio of the mixed acid to isooctyl alcohol based on nitric acid of 1.2:1. The reactor was composed of micro-channel reactors and tubular reactors connected alternately, wherein there were 2 micro-channel reactors and 2 tubular reactors. During the reaction, the reaction temperature in the micro-channel reactors and the tubular reactors was controlled at 10°C, and the mixed acid and isooctyl alcohol passed through the micro-channel reactors and the tubular reactors, wherein the residence time of the material in the first micro-channel reactor was 10 seconds, the residence time of the material in the second micro-channel reactor was 5 seconds, and the residence time of the material in the tubular reactors was 40 seconds, and the total time was 95 seconds.

[0063] (2) The reaction product obtained in step (1) was passed into an oil-water separation device to separate the aqueous phase and the organic phase, the organic phase was subjected to alkali washing and neutralization with a 10 wt% sodium bicarbonate alkaline solution, the alkali washing product was subjected to water washing with 1 volume of water, and then dried to obtain isooctyl nitrate. The purity of the obtained isooctyl nitrate is shown in Table 1.

[0064] Example 2

[0065] Isooctyl nitrate was prepared in the same manner as in Example 1, except that in step (1), the molar ratio of sulfuric acid to nitric acid was 2.3:1. The conversion rate of isooctyl alcohol and the purity of the obtained product are shown in Table 1.

[0066] Example 3

[0067] Isopropyl nitrate was prepared in the manner of Example 1 except that in step (1) the molar ratio of sulfuric acid to nitric acid was 1.8:1. Isopropyl alcohol conversion and product purity obtained are shown in Table 1.

[0068] Example 4

[0069] Isopropyl nitrate was prepared in the manner of Example 1 except that during the reaction the temperature in the microchannel reactor and the tube reactor was controlled at 5°C and the mixed acid and isopropyl alcohol were passed through the microchannel reactor and the tube reactor, where the first microchannel reactor had a residence time of 10 seconds, the second microchannel reactor had a residence time of 5 seconds, and the tube reactor had a residence time of 50 seconds, for a total of 115 seconds. Isopropyl alcohol conversion and product purity obtained are shown in Table 1.

[0070] Example 5

[0071] Isopropyl nitrate was prepared in the manner of Example 1 except that during the reaction the temperature in the microchannel reactor and the tube reactor was controlled at 30°C and the mixed acid and isopropyl alcohol were passed through the microchannel reactor and the tube reactor, where the first microchannel reactor had a residence time of 10 seconds, the second microchannel reactor had a residence time of 5 seconds, and the tube reactor had a residence time of 25 seconds, for a total of 65 seconds. Isopropyl alcohol conversion and product purity obtained are shown in Table 1.

[0072] Example 6

[0073] The reactor was composed of microchannel reactors and tube reactors connected alternately, where there were 3 microchannel reactors and 3 tube reactors. During the reaction, the temperature in the microchannel reactor and the tube reactor was controlled at 10°C and the mixed acid and isopropyl alcohol were passed through the microchannel reactor and the tube reactor, where the first microchannel reactor had a residence time of 10 seconds, the second microchannel reactor had a residence time of 5 seconds, the third microchannel reactor had a residence time of 5 seconds, the first tube reactor had a residence time of 25 seconds, the second tube reactor had a residence time of 25 seconds, and the third tube reactor had a residence time of 25 seconds, for a total of 90 seconds.

[0074] Example 7

[0075] Isopropyl nitrate was prepared in the manner of Example 1 except that in step (1) the molar ratio of the mixed acid to isopropyl alcohol, based on nitric acid, was 1.4:1. Isopropyl alcohol conversion and product purity obtained are shown in Table 1.

[0076] Example 8

[0077] Isopropyl nitrate was prepared in the same manner as Example 1, except that in step (1), the molar ratio of the mixed acid to isopropyl alcohol, calculated as nitric acid, was 1.1:1. The isopropyl alcohol conversion and the purity of the product obtained are shown in Table 1.

[0078] Comparative Example 1

[0079] Isopropyl nitrate was prepared in the same manner as Example 1, except that the entire process was carried out using a microchannel reactor, and no tubular reactor was used. The reaction was carried out through the microchannel reactor for 80 s.

[0080] Comparative Example 2

[0081] Isopropyl nitrate was prepared in the same manner as Example 1, except that the tubular reactor and the microchannel reactor were sequentially exchanged, and the tubular reactor was used first, followed by the microchannel reactor. The isopropyl alcohol conversion and the purity of the product obtained are shown in Table 1.

[0082] The "system pressure drop" in Table 1 refers to the difference between the inlet pressure and the outlet pressure of the entire reaction system.

[0083] Table 1

[0084]

[0085] As can be seen from the results in Table 1, the reaction system using the method of the embodiments of the present application has a lower pressure drop at the same product purity and isopropyl alcohol conversion, and can achieve a higher production capacity.

[0086] The above describes the preferred embodiments of the present application in detail, but the present application is not limited thereto. Within the technical concept of the present application, various simple modifications can be made to the technical solutions of the present application, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be considered as disclosed by the present application, and all fall within the protection scope of the present application.

Claims

1. A method for preparing isooctyl nitrate, characterized in that, Includes the following steps: 1) The step of introducing acid and isooctyl alcohol into 2-10 reaction modules for contact reaction; 2) The step of purifying the reaction product to obtain isooctyl nitrate. The reaction module consists of a microchannel reactor and a tubular reactor connected in sequence. The acids include sulfuric acid and nitric acid; The acid is introduced in the following manner: A) and / or B): A) The sulfuric acid and nitric acid are mixed in a molar ratio of 1.5-2.5:1 to obtain a mixed acid, which is then introduced into the reaction module. The molar ratio of the mixed acid to the isooctanol, calculated as nitric acid, is 1.0-1.5:1, and the water content in the mixed acid is 8-18% by mass. B) The sulfuric acid and nitric acid are simultaneously introduced into the reaction module at a molar ratio of 1.5-2.5:1, and the molar ratio of the nitric acid to the isooctyl alcohol is 1.0-1.5:1, and the water content in the acid is 8-18% by mass. The volume of the tubular reactor is 4-20 times the volume of the microchannel reactor. The conditions for the contact reaction include: a reaction temperature of 5-10°C and a total reaction time of 30-400 seconds; In the reaction module, the residence time of the microchannel reactor is 3-30 seconds, and the residence time of the tubular reactor is 10-200 seconds.

2. The preparation method according to claim 1, wherein, In method A), the molar ratio of sulfuric acid to nitric acid in the mixed acid is 1.5-2.3:

1.

3. The preparation method according to claim 1, wherein, In method B), sulfuric acid and nitric acid are simultaneously introduced into the reaction module at a molar ratio of 1.5-2.3:

1.

4. The preparation method according to claim 1, wherein, The number of reaction modules is 2-8.

5. The preparation method according to claim 4, wherein, The number of reaction modules is 2-5.

6. The preparation method according to claim 1, wherein, In the reaction module, the volume of the tubular reactor is 4-10 times the volume of the microchannel reactor.

7. The preparation method according to claim 1, wherein, In step 3), the purification method includes: separating the aqueous phase and the organic phase, followed by neutralization, washing, and drying.

8. The preparation method according to claim 1, wherein, The method also includes a step of recovering waste acid from the aqueous phase.

9. The preparation method according to claim 1, wherein, In method A), the molar ratio of the mixed acid, calculated as nitric acid, to the isooctyl alcohol is 1.1-1.4:

1.

10. The preparation method according to claim 1, wherein, In method B), the molar ratio of nitric acid to isooctyl alcohol is 1.1-1.4:

1.

11. The application of the preparation method according to any one of claims 1-10 in the preparation of isooctyl nitrate.

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