Synthesis method of phthalimido peroxyhexanoic acid

Abstract

The invention belongs to the technical field of organic synthesis, and particularly relates to a synthetic method of phthalimido peroxyhexanoic acid. According to the method, the molecular sieve, the acidic resin or the supported metal oxide is adopted as a heterogeneous catalyst to replace traditional concentrated sulfuric acid, and the continuous flow microchannel reactor system is combined, so that safe, efficient and environment-friendly synthesis of the phthalimido peroxyhexanoic acid is realized. The method solves the problems of serious equipment corrosion, environmental pollution caused by waste acid, poor reaction selectivity and low process safety in the prior art, realizes cyclic utilization of the catalyst and continuous and automatic control of the process, and has remarkable industrial application value.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of organic synthesis, and particularly relates to a synthesis method of phthalimido peroxyhexanoic acid, and particularly to a synthesis method using a heterogeneous catalyst and a continuous flow microchannel reactor. BACKGROUND

[0002] Phthalimido peroxyhexanoic acid has excellent bleaching and disinfecting properties, and is widely used in various fields. It can effectively remove stubborn stains (grass stains, tea stains, coffee stains, tomato stains, etc.), eliminate odors, and kill bacteria, bacteria, and fungi on textiles and hard surfaces, and is also used as a powerful whitening and anti-plaque agent in the personal care industry. In addition, its ecotoxicological properties are very environmentally friendly, gentle to the skin and odorless, and does not release volatile organic compounds (VOCs) or chlorine into the environment. As an active ingredient of high-efficiency low-temperature bleaching agent, it does not need to use activators, preservatives, neutralizers or alkalis. The existing contract process has certain disadvantages.

[0003] At present, the traditional batch kettle reactor is mainly used in industry, concentrated sulfuric acid is used as catalyst, and it is prepared by condensation reaction of phthalic anhydride and caprolactam, and then oxidized by hydrogen peroxide. The synthesis route is as follows:

[0004]

[0005] The first step (S1) uses phthalic anhydride and 6-aminohexanoic acid as raw materials to synthesize the intermediate, and the by-product is water. The water vapor produced under high temperature conditions is not conducive to the reaction, inhibits the reaction, and has certain requirements for the equipment, and the price of 6-aminohexanoic acid is relatively high, which does not have advantages in production cost.

[0006]

[0007] The second step (S2) generally uses 10V concentrated sulfuric acid as solvent, and a large amount of waste acid is generated during post-processing, which pollutes the environment. Oxidation reaction with 50% and above concentration of H2O2 has high safety risk.

[0008] The above synthesis process has many defects: first, the use of concentrated sulfuric acid as catalyst leads to serious equipment corrosion, a large amount of waste acid is generated after reaction, and the environment is seriously polluted; second, side reactions easily occur under the catalysis of concentrated sulfuric acid, the selectivity of the product is poor, and the purity is not high; third, hydrogen peroxide decomposes violently under strong acid conditions, and the heat is concentrated, the heat transfer efficiency of the traditional kettle reactor is low, which easily leads to local overheating, and causes safety accidents such as temperature runaway and explosion; in addition, the batch operation has low production efficiency, and the product quality has large batch-to-batch difference, which is not conducive to large-scale industrial production.

[0009] For the problem of acid catalyst, although there are studies trying to replace liquid acid with solid acid catalyst, but it does not involve the preparation of peroxycarboxylic acid. In the reactor technology, compared with the traditional tank reactor, the microreactor is based on the principle of repeated impact under the push of high-pressure constant-flow pump to carry out the reaction, which has the advantages of high-speed mixing, high-efficiency heat transfer, good repeatability, rapid system response, easy automation control, almost no amplification effect and high safety performance. But there is no related report on the synthesis of phthalimido peroxyhexanoic acid by using microreactor.

[0010] The present application develops a set of continuous flow microreactor, and applies the continuous flow microreaction technology to the preparation process of phthalimido peroxyhexanoic acid, so as to solve the problems of low condensation reaction rate, high raw material cost, use of high-concentration H2O2 in oxidation reaction, and great safety risk of explosion in storage, transportation and use. SUMMARY

[0011] In view of the above technical problems of the phthalimido peroxyhexanoic acid tank reaction synthesis method, such as low reaction rate of raw materials, high cost of raw materials, use of high-concentration H2O2 in oxidation reaction, and great safety risk of explosion in storage, transportation and use, the present application provides a continuous flow microreaction synthesis method of phthalimido peroxyhexanoic acid. Concentrated sulfuric acid can easily corrode equipment, easily cause side reactions, and has poor product selectivity, and a large amount of waste acid is also easily produced. The present application uses a heterogeneous catalyst to replace concentrated sulfuric acid, which eliminates waste acid pollution from the source, and the catalyst can be recycled, which meets the principle of green chemistry. In addition, the continuous flow microchannel reactor has extremely high specific surface area, excellent heat transfer efficiency and high safety, and the total cost of the project is low, and the production capacity is improved.

[0012] To achieve the above object, the present application adopts the following technical scheme:

[0013] The present application provides a method for synthesizing phthalimido peroxyhexanoic acid by using a continuous flow microreactor, and the reaction device comprises an intermediate storage tank, a hydrogen peroxide storage tank and a catalyst slurry storage tank, which are respectively connected with a reactor system through a precision feeding pump;

[0014] The reactor system comprises a straight-flow microchannel reactor and an enhanced mixing microchannel reactor arranged in series, and the microchannel has a characteristic size of 10-500 μm;

[0015] The synthesis method of phthalimido peroxyhexanoic acid comprises the following steps:

[0016] (1) Condensation reaction step: heating phthalic anhydride and caprolactam in a protective atmosphere to carry out melt condensation reaction, to generate phthalimido hexanoic acid intermediate;

[0017] (2) Oxidation reaction step: the intermediate is subjected to oxidation reaction with hydrogen peroxide in the presence of a heterogeneous catalyst in a continuous flow microchannel reactor to obtain phthalimidyl peroxyhexanoic acid.

[0018] The specific reaction route is as follows:

[0019]

[0020] The specific process route is shown in the accompanying Figure 1

[0021] The heterogeneous catalyst is selected from at least one of a molecular sieve, an acidic resin, and a supported metal oxide.

[0022] The heterogeneous catalyst includes at least one of sulfonated polysiloxane, heteroatom-substituted zeolite, styrene-divinylbenzene copolymer sulfonic acid resin, perfluorosulfonic acid resin, WO3 / ZrO2, MoO3 / Al2O3, and Nb2O5 / SiO2.

[0023] These heterogeneous catalysts, as solid, water-insoluble and stable sulfuric acid substitutes, can be separated from the reaction system by simple filtration and can be recycled for use, fundamentally solving the problem of waste acid pollution.

[0024] The condensation reaction step is carried out in a high-pressure reaction kettle, the reaction temperature is 100-160°C, and the reaction time is 6-24 hours.

[0025] In the condensation reaction step, the molar ratio of phthalic anhydride to caprolactam is 0.8:1-1.2:1.

[0026] In the oxidation reaction step, the concentration of hydrogen peroxide is 15-30%.

[0027] In the oxidation reaction step, the mass ratio of heterogeneous catalyst to phthalimidyl hexanoic acid intermediate is 1:10 to 1:50, and the reaction temperature is controlled at 0-25°C.

[0028] In some embodiments, the synthesis method of the present application comprises the following steps:

[0029] (1) Condensation reaction: under the protection of argon or nitrogen, phthalic anhydride and caprolactam are added to a high-pressure reaction kettle at a molar ratio of 0.8:1-1.2:1, the temperature is controlled in the range of 100-160°C, the reaction is carried out for 6-24 hours, and after the reaction is completed, the temperature is lowered to 100-120°C to obtain a phthalimidyl hexanoic acid intermediate.

[0030] ​(2) Oxidation reaction: the above intermediate is prepared into a solution with a proper solvent, preferably ethyl acetate, acetone or ethanol; then a slurry is formed with a heterogeneous catalyst, and is input into a continuous flow micro-channel reactor system through a feed pump; a 15-30% concentration hydrogen peroxide solution is input into the reactor system through another feed pump; the reaction temperature is controlled within a range of 0-25°C, and the residence time of the material in the reaction channel is controlled to be 5-30 minutes by adjusting the motor speed; and the reaction process is monitored in real time through an online detection device.

[0031] (3) Catalyst separation and circulation: after the reaction is completed, the reaction mixture is input into an online filtration system to realize the separation of the catalyst and the reaction liquid; the separated catalyst is washed, dried and activated, and then is recycled; and the catalyst can be recycled for 5-10 times while maintaining a high activity.

[0032] (4) Product purification: the reaction liquid after the catalyst is separated is concentrated under reduced pressure, is cooled and crystallized, is filtered, is washed and is dried to obtain a high-purity phthalimido peroxyhexanoic acid product.

[0033] The continuous flow micro-channel reactor system adopted in the application is as shown in Figure 4 The continuous flow micro-channel reactor system adopted in the application mainly comprises:

[0034] A material supply system: comprising an intermediate storage tank, a hydrogen peroxide storage tank and a catalyst slurry storage tank, which are connected with the reactor system through precise feed pumps respectively;

[0035] A reaction system: comprising a straight-flow micro-channel reactor and an enhanced mixing micro-channel reactor arranged in series, and the micro-channel has a characteristic size of 10-500 μm.

[0036] The continuous flow micro-channel reactor system adopted in the application further comprises:

[0037] A control system: comprising a temperature sensor, a pressure sensor, a flow controller and a computer control system, which realizes the accurate control of the reaction conditions;

[0038] A product collection and catalyst separation system: comprising a product collection tank, an online filter and a catalyst regeneration device.

[0039] The reactor system can not only increase the driving force in the transfer process such as temperature and concentration gradient, but also greatly increase the transfer area, effectively reduce the mass transfer resistance, and accurately control the reaction conditions through the reduction of the characteristic size. It is especially suitable for processes such as peroxide synthesis which are controlled by transfer, and can replace batch reactors, greatly improving the production efficiency and safety.

[0040] According to another aspect of the application, the above phthalimido peroxyhexanoic acid is applied in bleaching agents, disinfectants, oxidants or high molecular polymerization initiators.

[0041] The beneficial effects of the present application relative to the prior art include:

[0042] The present application adopts a continuous method to synthesize phthalimido peroxyhexanoic acid. Compared with the traditional preparation method, the non-homogeneous catalyst is used to replace the traditional concentrated sulfuric acid to eliminate waste acid pollution from the source, the catalyst can be recycled, and the green chemistry principle is met. The continuous flow micro-channel reactor is used to replace the traditional batch reactor, the oxidation reaction uses low concentration of H2O2 to reduce the safety risk, and at the same time, the use amount of concentrated H2SO4 is greatly reduced to reduce the generation of waste acid. The overall synthesis process is shortened, the operation is simple, the cost is greatly reduced, and the industrial application is easy. BRIEF DESCRIPTION OF DRAWINGS

[0043] Figure 1 is a synthesis route diagram of the phthalimido peroxyhexanoic acid of the present application.

[0044] Figure 2 is the HPLC chart of compound 2 of the present application. H NMR is as shown. Figure 2

[0045] Figure 3 is the HPLC chart of compound 3.

[0046] Figure 4 is a structure diagram of the continuous flow micro-channel reactor system of the present application. DETAILED DESCRIPTION

[0047] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor are within the scope of protection of the present application.

[0048] The non-homogeneous catalyst described in the present application is commercially available unless otherwise specified.

[0049] Example 1

[0050] Condensation reaction: under the protection of argon, 1.30 kg of phthalic anhydride and 1.0 kg of caprolactam are added to a high-pressure reaction kettle, the temperature is controlled at 140℃, and the reaction is carried out for 12 hours. After the reaction is completed, the temperature is lowered to 120℃, and the phthalimido hexanoic acid intermediate is obtained.

[0051] ​Oxidation reaction: The intermediate was prepared into a 30% solution with ethyl acetate, mixed with the heteroatom-substituted zeolite molecular sieve Sn-DZ-1 catalyst (mass ratio of catalyst to intermediate was 1:20) to form a slurry, which was input into a continuous flow micro-channel reactor system through a feed pump at a flow rate of 50 mL / min; at the same time, a 20% concentration hydrogen peroxide solution was input into the reactor system at an appropriate flow rate; the reaction temperature was controlled at 15°C, and the motor speed was adjusted to make the residence time of the material 15 minutes.

[0052] Catalyst separation and product purification: The reaction mixture entered an online filter, and the separated catalyst was washed with ethanol, vacuum dried, and recycled; the filtrate was concentrated under reduced pressure, cooled and crystallized, filtered under reduced pressure, and washed with purified water three times, and then vacuum dried to obtain 2.25 kg of white solid product with a purity of 92%.

[0053] Example 2

[0054] Catalyst preparation: The sulfonated polysiloxane solid acid catalyst was prepared according to the method disclosed in CN1113076C.

[0055] Condensation reaction: The same as Example 1.

[0056] Oxidation reaction: The intermediate was prepared into a 25% solution with acetone, mixed with the sulfonated polysiloxane catalyst (mass ratio of catalyst to intermediate was 1:15) to form a slurry, which was input into a reactor through a feed pump; at the same time, an 18% concentration hydrogen peroxide solution was input into the reactor; the reaction temperature was controlled at 20°C, and the residence time of the material was 20 minutes.

[0057] Catalyst separation and product purification: The same as Example 1, and 2.18 kg of product was obtained with a purity of 90%.

[0058] Example 3

[0059] Condensation reaction: The same as Example 1.

[0060] Oxidation reaction: The intermediate was prepared into a 35% solution with isopropyl alcohol, mixed with the WO3 / ZrO2 catalyst (mass ratio of catalyst to intermediate was 1:25) to form a slurry, which was input into a reactor through a feed pump; at the same time, a 25% concentration hydrogen peroxide solution was input into the reactor; the reaction temperature was controlled at 10°C, and the residence time of the material was 10 minutes.

[0061] Comparative Example 1 (traditional method)

[0062] According to the traditional method described in the background art: condensation reaction is the same as example 1; oxidation reaction stage, the intermediate is dissolved in 5 times the volume of concentrated sulfuric acid, slowly add 18% hydrogen peroxide after cooling to 20℃, control the reaction temperature not more than 30℃, after the end of the addition, continue to stir for 6 hours, the post-processing is the same as example 1. The product 2.20 kg, purity 82%.

[0063] Comparison of experimental data

[0064] In order to show the advantages of the present application more intuitively, the key data of each example and comparative example are summarized in the following table.

[0065]

[0066]

[0067] From the above table, it can be seen that the product purity, reaction efficiency, environmental friendliness and process control precision of each example of the present application are significantly better than those of the traditional method.

[0068] Catalyst recycling experiment

[0069] The catalyst of example 1 was recycled for experiment, and the results were as follows:

[0070] Cycles 1 2 3 4 5 Product purity (%) 92 91 90 89 88 Catalyst activity (%) 100 98 95 92 90

[0071] Experiments show that the heterogeneous catalyst used in the present application can maintain more than 90% of the initial activity after 5 cycles, which shows that it has excellent stability and recycling performance.

[0072] Finally, it should be pointed out that: the above only for the preferred embodiments of the present application, and not for limiting the present application, although the present application has been described in detail with reference to the foregoing examples, for those skilled in the art, it still can modify the technical solutions recorded in the foregoing examples, or make equivalent replacement for part of the technical features, any modification, equivalent replacement, improvement, etc. within the spirit and principles of the present application, should be included in the protection scope of the present application.

Claims

1. A method for synthesizing phthalimide-peroxyhexanoic acid, characterized in that, The reaction apparatus includes an intermediate storage tank, a hydrogen peroxide storage tank, and a catalyst slurry storage tank, which are connected to the reactor system via precision feed pumps. The reactor system includes a direct-flow microchannel reactor and an enhanced mixing microchannel reactor arranged in series, with the microchannel characteristic size being 10-500 μm; Synthesis method of phthalimide peroxyhexanoic acid Includes the following steps: Includes the following steps: (1) Condensation reaction step: Phthalic anhydride and caprolactam are heated under a protective atmosphere to carry out a melt condensation reaction to generate phthalimide hexanoic acid intermediate; (2) Oxidation reaction step: The intermediate is oxidized with hydrogen peroxide in the presence of a heterogeneous catalyst in a continuous flow microchannel reactor to obtain phthalimide peroxyhexanoic acid. The heterogeneous catalyst is selected from at least one of molecular sieves, acidic resins, and supported metal oxides.

2. The method as described in claim 1, characterized in that, The heterogeneous catalyst includes at least one of sulfonated polysiloxane, heteroatom-substituted zeolite, styrene-divinylbenzene copolymer sulfonic acid resin, perfluorosulfonic acid resin, WO3 / ZrO2, MoO3 / Al2O3, and Nb2O5 / SiO2.

3. The method as described in claim 1, characterized in that: The condensation reaction step is carried out in a high-pressure reactor at a temperature of 100-160℃ for 6-24 hours; the molar ratio of phthalic anhydride to caprolactam is 0.8:1 to 1.2:

1.

4. The method as described in claim 1, characterized in that: In the oxidation reaction step, the concentration of hydrogen peroxide is 15-30%; the mass ratio of the heterogeneous catalyst to the phthalimide hexanoic acid intermediate is 1:10 to 1:50; and the reaction temperature is controlled at 0-25℃.

5. The method as described in claim 1, characterized in that: The oxidation reaction step is carried out in a continuous flow microchannel reactor with controllable residence time; the residence time of the material in the reaction channel is controlled by adjusting the motor speed; the total residence time of the reaction is 5-30 minutes.

6. The method as described in claim 1, characterized in that: Includes the following steps: (1) Condensation reaction: Under the protection of argon or nitrogen, phthalic anhydride and caprolactam are added to a high-pressure reactor in a molar ratio of 0.8:1 to 1.2:

1. The temperature is controlled within the range of 100-160℃ and the reaction is carried out for 6-24 hours. After the reaction is completed, the temperature is lowered to 100-120℃ to obtain phthalimide hexanoic acid intermediate. (2) Oxidation reaction: The above intermediate is prepared into a solution with an appropriate amount of solvent, preferably ethyl acetate, acetone or ethanol; then it is combined with a heterogeneous catalyst to form a slurry, which is fed into the continuous flow microchannel reactor system through a feed pump; at the same time, a 15-30% hydrogen peroxide solution is fed into the reactor system through another feed pump; the reaction temperature is controlled within the range of 0℃ to 25℃, and the residence time of the material in the reaction channel is controlled to be 5-30 minutes by adjusting the motor speed; the reaction process is monitored in real time by an online detection device. (3) Catalyst separation and recycling: After the reaction is completed, the reaction mixture enters the online filtration system to separate the catalyst from the reaction liquid; the separated catalyst is washed, dried and activated and then recycled. The catalyst can be recycled 5-10 times while maintaining high activity; (4) Product purification: The reaction solution after catalyst separation is concentrated under reduced pressure, cooled and crystallized, filtered, washed and dried to obtain high-purity phthalimide peroxyhexanoic acid product.

7. The use of phthalimide peroxyhexanoic acid synthesized by any one of claims 1-6 in bleaching agents, disinfectants, oxidants or polymer initiators.

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