Synthesis method of micro-channel continuous flow buffer system initiator

Abstract

The invention discloses a synthesis method of a microchannel continuous flow buffer system initiator, and relates to the technical field of chemical engineering. The synthesis method comprises the following steps: reacting materials in the micro-channel reactor, simultaneously performing heat exchange in the micro-channel reactor, mixing hydrogen peroxide and a buffer solution in the first reaction module, mixing acyl chloride and protonic acid in the second reaction module, and performing heat exchange reaction in the micro-channel reactor, thereby obtaining the product. The last reaction module is cooled to terminate the reaction, an oil-water separation device is connected behind the last reaction module, and the obtained oil phase is the peroxidation initiator. In the synthesis method, one molecule of hydrogen peroxide can produce two hydrogen ions, the acidity is gradually enhanced, the reaction rate is rapidly increased, and after a certain degree is reached, a decomposition reaction can occur; the micro-channel reactor is strong in mixing and high in heat exchange rate, and meanwhile, an acidic buffer system is adopted, so that protonic acid keeps a certain concentration, the reaction rate is increased, the reaction temperature is reduced, the oil phase proportion is increased, and the reaction yield is increased.

Description

Technical Field

[0001] The present invention relates to the field of chemical engineering technology, and particularly relates to a method for synthesizing an initiator of a microchannel continuous flow buffer system. Background Art

[0002] Peroxide initiators play a crucial role in polymerization reactions. By selecting appropriate initiators, the polymerization reaction process can be effectively controlled, thereby obtaining polymer products with expected properties, and are mainly used in the polymerization of monomers such as vinyl chloride, ethylene, and styrene. Peroxide initiators refer to a class of compounds containing a peroxy group (-O-O-), and after heating, the -O-O- bond breaks and splits into two corresponding free radicals, thereby initiating the polymerization of monomers. Due to the presence of its peroxy bond, it is prone to self-decomposition and generates gas, and is prone to explosion, and needs to be stored at low temperature. Now most enterprises choose organic peroxides as initiators. There are many types of peroxide initiators, and their structures are different, and their activities vary greatly. The peroxidation reaction is defined as the process of introducing a peroxy group into an organic compound molecule to obtain a peroxide product. The process of replacing the hydrogen atom of hydrogen peroxide with groups such as alkyl and acyl groups to form the corresponding organic peroxide also belongs to the peroxidation process. The peroxidation process is used to prepare organic peroxides and is widely used in fields such as curing agents, bleaching agents, deodorants, catalysts, preservatives, and oxidants. The peroxidation process involves peroxy groups and peroxide products with unstable properties. If the operation is improper, the risk of causing fire and explosion accidents is relatively high. Therefore, it is very important to clarify the dangerous characteristics of the peroxidation process for formulating corresponding safety control measures.

[0003] For a class of peroxide initiators such as diisobutyryl peroxide, bis(2-ethylhexyl) peroxydicarbonate, 3,5,5-trimethylhexanoyl peroxide, etc., in the first step, under alkaline conditions, hydrogen peroxide is added and stirred to produce O 2 2- negative ions, and then acyl chloride is added. Due to the influence of chlorine ions and double bond oxygen atoms in acyl chloride, a carbocation center is formed at the acyl carbon, and O 2 2- negative ions attack the carbocation center, then form an intermediate transition carbocation center, and then attack the carbocation acyl chloride ion to form a peroxidized organic matter. The reaction mechanism is as follows:

[0004]

[0005]

[0006] Chinese patents CN111548295A, CN116396200A, and CN109400514A all disclose the production of initiators in a traditional reactor: in a strongly alkaline condition, such as sodium hydroxide or potassium hydroxide solution, hydrogen peroxide is added, and after stirring evenly, isononanoyl chloride, diethylhexyl chloroformate, or 3,5,5-hexanoyl is added dropwise while controlling the temperature to produce the initiator product. The reactions disclosed in the above patents are all traditional batch reactions. Under the stirring action, a two-phase water-oil reaction occurs at the water-oil interface, and the reaction rate is slow.

[0007] In the process of traditional chemical reactions, it is often difficult to control the reaction conditions, especially when precise control of the reaction rate and product selectivity is required. Microchannel reactors, with their unique structure and operating characteristics, offer the possibility of achieving efficient and precise chemical reactions. "Li Lixia, Yin Guoqiang, Liu Song, et al. Research progress on the synthesis of peroxides in microchannel reactors [J]. Dyes and Pigments, 2022, 59(01): 51-55+62." discloses the advantages of microreactors: compared with batch reactors, microreactors can effectively reduce the explosion hazard when synthesizing peroxides, have efficient mass and heat transfer, reduce the reaction time, and improve the product yield. However, due to the small diameter of the channels in the microreactor, when the raw materials contain solid particles or solids precipitate out in the product, blockage is likely to occur, greatly reducing the reaction effect; in terms of the application scope, it needs to be expanded. Due to the limitations of the microreactor's own conditions, the reaction effect of some reactions in the microreactor is not good, and it is necessary to explore a more reasonable alternative reaction process route technically and find more suitable reaction conditions.

[0008] Chinese patent CN117924134A discloses a method for preparing bis(2-ethylhexyl) peroxydicarbonate in one step, including the following steps: (1) Mixing an aqueous hydrogen peroxide solution and a phase transfer catalyst to prepare solution 1; (2) Pumping solution 1 prepared in step (1), an aqueous sodium hydroxide solution, and a (2-ethyl) hexyl chloroformate solution into a micromixer for premixing and then entering a micro-packed bed reactor for reaction to obtain reaction solution 2; (3) Passing the reaction solution 2 prepared in step (2) into a separation tank for static stratification and taking the upper oil phase to obtain bis(2-ethylhexyl) peroxydicarbonate; the reaction temperature in step (2) is 50°C; the reaction time is 8 min. The reaction temperature in this patent is 50°C, and the peroxide initiator -OO- is relatively fragile, and high temperature and long reaction time are likely to cause its decomposition.

[0009] In view of this, to solve the deficiencies of the prior art, the present invention provides a method for synthesizing an initiator with a microchannel continuous flow buffer system. Summary of the Invention

[0010] The object of the present invention is to provide a method for synthesizing an initiator in a microchannel continuous flow buffer system, which greatly improves the content and yield of the initiator.

[0011] To achieve the above object of the invention, the technical solution of the present invention is as follows:

[0012] The present invention provides a method for synthesizing an initiator in a microchannel continuous flow buffer system, comprising the following steps: the materials are reacted through a microchannel reactor while heat exchange is carried out through the microchannel reactor, hydrogen peroxide and the buffer solution are mixed through a first reaction module, acyl chloride and protonic acid are mixed through a second reaction module, after heat exchange reaction through the microchannel reactor, the last reaction module is cooled to terminate the reaction, and an oil-water separation device is connected after the last reaction module, and the obtained oil phase is the peroxide initiator, and the obtained water phase is the remaining buffer solution.

[0013] In one aspect of the present invention, the initiator is selected from any one of diisobutyryl peroxide, bis(3-methoxybutyl) peroxydicarbonate, bis(2-ethylhexyl) peroxydicarbonate, bis(4-tert-butylcyclohexyl) peroxydicarbonate, 1,1,3,3-tetramethylbutyl peroxypivalate, and bis(3,3,5-trimethylhexyl) peroxide.

[0014] In one aspect of the present invention, the acyl chloride is selected from any one of isobutyryl chloride, 3-methoxybutyryl chloride, 2-ethylhexyl chloroformate, 4-tert-butylcyclohexyl chloroformate, 1,1,3,3-tetramethylbutyl pivaloyl chloride, and 3,3,5-trimethylhexanoyl chloride.

[0015] In one aspect of the present invention, the material of the microchannel reactor is one or a combination of glass and silicon carbide.

[0016] In one aspect of the present invention, the concentration of hydrogen peroxide is 20-70%; the protonic acid is selected from any one of hydrochloric acid, sulfuric acid, phosphoric acid, and trifluoroacetic acid; the concentration of the protonic acid is 0.01-1 mol / L.

[0017] In one aspect of the present invention, the buffer solution is a phosphate buffer system; the phosphate buffer system includes sodium dihydrogen phosphate, disodium hydrogen phosphate, phosphoric acid, and water.

[0018] In one aspect of the present invention, the concentration of sodium dihydrogen phosphate is 1.38 g / L-138 g / L; the concentration of disodium hydrogen phosphate is 1.42 g / L-142 g / L; the pH of the phosphate buffer system is 6-7.

[0019] In one aspect of the present invention, the microchannel reactor comprises 2 - 10 reaction modules; the temperature of the heat exchange reaction is 0 - 30 °C; the last 1 - 5 reaction modules in the microchannel reactor adopt low-temperature quenching reaction; the temperature of the quenching reaction is 0 - 10 °C.

[0020] In one aspect of the present invention, the molar ratio of hydrogen peroxide to acyl chloride is 1 - 3:1; the mass ratio of buffer solution to acyl chloride is 0.5 - 5:1; the mass ratio of protonic acid to acyl chloride is 0.001 - 1:1.

[0021] In one aspect of the present invention, the oil-water separation device adopts static liquid separation or an oil-water separator; the remaining buffer solution can be reused. When the pH of the remaining buffer solution is less than 5, sodium hydroxide is added to adjust the pH to 6 - 7 and then reused.

[0022] The beneficial effects of the present invention are as follows:

[0023] The present invention uses a protonic acid as a catalyst. In the first step, it reacts with acyl chloride to form a carbocation, and then an electronegative substance attacks the carbocation center, increasing the reaction rate. During the reaction process, one molecule of hydrogen peroxide will produce two hydrogen ions, gradually increasing the acidity, and the reaction rate will increase rapidly. After reaching a certain level, a decomposition reaction will occur. Therefore, by using a microchannel reactor with strong mixing and fast heat exchange rate, and adopting an acidic buffer system to keep the protonic acid at a certain concentration, the reaction rate can be increased, the reaction temperature can be reduced, the proportion of the oil phase can be increased, and the reaction yield can be improved.

[0024] Reaction mechanism under acidic conditions:

[0025]

[0026] Decomposition reaction under strong acid conditions:

[0027] Description of the drawings

[0028] Figure 1 It is a device diagram of the microchannel reactor. Detailed implementation manners

[0029] The following non-limiting examples can enable those of ordinary skill in the art to understand the present invention more comprehensively, but do not limit the present invention in any way. The following content is merely an exemplary illustration of the scope claimed by the present invention. Those skilled in the art can make various changes and modifications to the invention according to the disclosed content, and it should also fall within the scope claimed by the present invention.

[0030] The present invention will be further described by way of specific embodiments. All kinds of chemical reagents used in the embodiments of the present invention are obtained through conventional commercial channels unless otherwise specified. Unless otherwise specified, the contents described hereinafter are mass contents. Unless otherwise specified, it is understood that the operations are carried out at room temperature.

[0031] Example 1

[0032] (1) In a Corning G1 microchannel reactor, 30 g / min of 27.5% hydrogen peroxide was introduced into glass module 1, and 23.61 g / min of phosphate buffer solution was introduced. The preparation method of this phosphate buffer solution: 13.8 g of sodium dihydrogen phosphate and 14.2 g of disodium hydrogen phosphate were respectively dissolved in sufficient water, then mixed evenly. The two solutions were mixed and made up to 1 L with water. During the mixing process, phosphoric acid was added to adjust the pH value to 7.

[0033] (2) 23.64 g / min of 99% 2-ethylhexyl chloroformate was introduced into glass module 2, and 0.2361 g / min of 0.1 mol / L hydrochloric acid was introduced.

[0034] (3) The molar ratio of hydrogen peroxide to 2-ethylhexyl chloroformate in the reactor was 2:1; the mass ratio of phosphate buffer solution to 2-ethylhexyl chloroformate was 1:1.

[0035] (4) After passing through 10 modules for reaction, the reaction temperature was 20 °C, and the quenching reaction was carried out in the last module at a temperature of -5 °C.

[0036] (5) After the reaction was completed, the reaction mixture was collected for 1 min, allowed to stand for layer separation, the aqueous phase and the oil phase (initiator product) were weighed, the content was detected, and the yield of bis(2-ethylhexyl) peroxydicarbonate initiator was calculated.

[0037] Example 2

[0038] 30 g / min of 27.5% hydrogen peroxide in step (1) of Example 1 was replaced with 15 g / min of 27.5% hydrogen peroxide, and the remaining processes were the same as those in Example 1. The molar ratio of hydrogen peroxide to 2-ethylhexyl chloroformate in the reactor was 1:1.

[0039] Example 3

[0040] 30 g / min of 27.5% hydrogen peroxide in step (1) of Example 1 was replaced with 9 g / min of 27.5% hydrogen peroxide, and the remaining processes were the same as those in Example 1. The molar ratio of hydrogen peroxide to 2-ethylhexyl chloroformate in the reactor was 0.6:1.

[0041] Example 4

[0042] Replace 30 g / min of 27.5% hydrogen peroxide in step (1) of Example 1 with 45 g / min of 27.5% hydrogen peroxide, and the remaining processes are the same as those in Example 1. The molar ratio of hydrogen peroxide to 2-ethylhexyl chloroformate in the reactor is 3:1.

[0043] Example 5

[0044] Replace 23.61 g / min of phosphate buffer solution in step (1) of Example 1 with 11.81 g / min of phosphate buffer solution, and the remaining processes are the same as those in Example 1. The mass ratio of phosphate buffer solution to 2-ethylhexyl chloroformate is 0.5:1.

[0045] Example 6

[0046] Replace 23.61 g / min of phosphate buffer solution in step (1) of Example 1 with 118.06 g / min of phosphate buffer solution, and the remaining processes are the same as those in Example 1. The mass ratio of phosphate buffer solution to 2-ethylhexyl chloroformate is 5:1.

[0047] Example 7

[0048] Replace 0.2361 g / min of 0.1 mol / L hydrochloric acid in step (2) of Example 1 with 0.2361 g / min of 1 mol / L hydrochloric acid, and the remaining processes are the same as those in Example 1.

[0049] Example 8

[0050] Replace 0.2361 g / min of 0.1 mol / L hydrochloric acid in step (2) of Example 1 with 0.0236 g / min of 0.1 mol / L hydrochloric acid, and the remaining processes are the same as those in Example 1.

[0051] Example 9

[0052] Replace the reaction temperature of 20 °C in step (4) of Example 1 with a reaction temperature of 5 °C, and the remaining processes are the same as those in Example 1.

[0053] Example 10

[0054] Replace 23.64 g / min of 99% 2-ethylhexyl chloroformate in step (2) of Example 1 with 21.34 g / min of 99% isononanoyl chloride (the molar amounts of 2-ethylhexyl chloroformate and isononanoyl chloride are the same), and the remaining processes are the same as those in Example 1. The initiator obtained is bis(3,5,5-trimethylhexanoyl) peroxide.

[0055] Example 11

[0056] Use the aqueous phase separated in step (5) of Example 1 as the phosphate buffer solution, with the flow rate of the phosphate buffer solution being 23.61 g / min, and the remaining processes being the same as those in Example 1.

[0057] Example 12

[0058] Replace 23.64 g / min of 99% 2-ethylhexyl chloroformate in step (2) of Example 1 with 14.50 g / min of 99% 3-methoxybutyryl, and the remaining processes are the same as those in Example 1.

[0059] Example 13

[0060] Replace 23.64 g / min of 99% 2-ethylhexyl chloroformate in step (2) of Example 1 with 14.50 g / min of 99% 4-tert-butylcyclohexyl chloroformate, and the remaining processes are the same as those in Example 1.

[0061] Example 14

[0062] Replace 23.64 g / min of 99% 2-ethylhexyl chloroformate in step (2) of Example 1 with 21.35 g / min of 98% 1,1,3,3-tetramethylbutyl pivalate, and the remaining processes are the same as those in Example 1.

[0063] Example 15

[0064] Replace 23.64 g / min of 99% 2-ethylhexyl chloroformate in step (2) of Example 1 with 17.70 g / min of 99% 3,3,5-trimethylhexanoyl, and the remaining processes are the same as those in Example 1.

[0065] Example 16

[0066] Replace 0.2361 g / min of 0.1 mol / L hydrochloric acid in step (2) of Example 1 with 0.1281 g / min of 0.1 mol / L sulfuric acid, and the remaining processes are the same as those in Example 1.

[0067] Example 17

[0068] Replace 0.2361 g / min of 0.1 mol / L hydrochloric acid in step (2) of Example 1 with 0.0787 g / min of 0.1 mol / L phosphoric acid, and the remaining processes are the same as those in Example 1.

[0069] The initiator contents and yields obtained in Examples 1 - 17 are shown in Table 1.

[0070] Table 1

[0071]

[0072]

[0073] Examples 1-9 illustrate that for different feed ratios, buffer concentrations, protonic acid concentrations, and reaction temperatures, the reaction can achieve high yields and high contents. Example 10 illustrates that this reaction can be used to produce initiators such as bis(2-ethylhexyl) peroxydicarbonate and 3,5,5-trimethylhexanoyl peroxide. Example 11 illustrates that the buffer can be used continuously. Examples 12-15 illustrate the applicability to different acyl chlorides, and Examples 16 and 17 illustrate that different protonic acid systems can be used.

[0074] Comparative Example 1

[0075] Replace 30 g / min of 27.5% hydrogen peroxide in step (1) of Example 1 with 6 g / min of 27.5% hydrogen peroxide, and the remaining processes are the same as in Example 1. The molar ratio of hydrogen peroxide to 2-ethylhexyl chloroformate in the reactor is 0.4:1.

[0076] Comparative Example 2

[0077] Replace 0.2361 g / min of 0.1 mol / L hydrochloric acid in step (2) of Example 1 with 0.2361 g / min of 2 mol / L hydrochloric acid, and the remaining processes are the same as in Example 1.

[0078] Comparative Example 3

[0079] Replace 23.61 g / min of phosphate buffer in step (1) of Example 1 with 5.9 g / min of phosphate buffer, and the remaining processes are the same as in Example 1. The mass ratio of phosphate buffer to 2-ethylhexyl chloroformate is 0.25:1.

[0080] The initiator contents and yields obtained in Comparative Examples 1-3 are shown in Table 2.

[0081] Table 2

[0082] Case Output / g Content Yield Comparative Example 1 19.23 80.33％ 73.49％ Comparative Example 2 2.55 0.87％ 0.11％ Comparative Example 3 20.57 90.27％ 88.34％

[0083] Comparative Example 1 shows that a low feed ratio will lead to incomplete reaction, thus reducing the content and yield of the initiator. Comparative Example 2 shows that too high a protonic acid concentration will lead to too fast a reaction rate, thus resulting in extremely low content and yield of the initiator. Comparative Example 3 shows that too little phosphate buffer will lead to a reduction in the initiator yield.

[0084] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for synthesizing an initiator for a microchannel continuous flow buffer system, characterized in that: The method comprises the following steps: materials react through a microchannel reactor and simultaneously exchange heat through the microchannel reactor, hydrogen peroxide and a buffer solution are mixed through a first reaction module, acyl chloride and a protonic acid are mixed through a second reaction module, after heat exchange reaction in the microchannel reactor, the last reaction module is cooled to terminate the reaction, an oil-water separation device is connected after the last reaction module, the obtained oil phase is a peroxidation initiator, and the obtained water phase is a residual buffer solution.

2. The synthesis reaction according to claim 1, characterized in that The initiator is selected from any one of diisobutyryl peroxide, bis(3-methoxybutyl) peroxydicarbonate, bis(2-ethylhexyl) peroxydicarbonate, bis(4-tert-butylcyclohexyl) peroxydicarbonate, 1,1,3,3-tetramethylbutyl peroxypivalate, and di(3,3,5-trimethylhexyl) peroxide.

3. The synthesis reaction according to claim 1, characterized in that The acyl chloride is selected from any one of isobutyryl chloride, 3-methoxybutyryl, 2-ethylhexyl chloroformate, 4-tert-butylcyclohexyl chloroformate, 1,1,3,3-tetramethylbutyryl pivalate, and 3,3,5-trimethylhexanoyl.

4. The synthesis reaction according to claim 1, characterized in that The material of the microchannel reactor is glass, silicon carbide or a combination of the two.

5. The synthesis reaction according to claim 1, characterized in that The concentration of the hydrogen peroxide is 20-70%; the protonic acid is selected from any one of hydrochloric acid, sulfuric acid, phosphoric acid and trifluoroacetic acid; and the concentration of the protonic acid is 0.01-1 mol / L.

6. The synthesis reaction according to claim 1, characterized in that The buffer is a phosphate buffer system; the phosphate buffer system comprises sodium dihydrogen phosphate, disodium hydrogen phosphate, phosphoric acid and water.

7. The synthesis reaction according to claim 6, characterized in that The concentration of the sodium dihydrogen phosphate is 1.38 g / L-138 g / L; the concentration of the sodium dihydrogen phosphate is 1.42 g / L-142 g / L; and the pH of the phosphate buffer system is 6-7.

8. The synthesis reaction according to claim 1, characterized in that The microchannel reactor comprises 2-10 reaction modules; the temperature of the heat exchange reaction is 0-30°C; the last 1-5 reaction modules in the microchannel reactor adopt a low-temperature quenching reaction; the temperature of the quenching reaction is 0-10°C.

9. The synthesis reaction according to claim 1, characterized in that The molar ratio of the hydrogen peroxide to the acyl chloride is 1-3:1; the mass ratio of the buffer to the acyl chloride is 0.5-5:1; and the mass ratio of the protonic acid to the acyl chloride is 0.001-1:

1.

10. The synthesis reaction according to claim 1, characterized in that The oil-water separation device adopts static liquid separation or an oil-water separator; the remaining buffer solution can be reused. When the pH of the remaining buffer solution is less than 5, sodium hydroxide is added to adjust the pH to 6-7 before reuse.

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