Method for continuously preparing benzoxazolone

Abstract

The invention relates to the technical field of organic synthesis, and particularly provides a method for continuously preparing benzoxazolone. The method comprises the following steps: continuously inputting molten 2-aminophenol and urea into a micro-channel reactor with a part of polytetrafluoroethylene film inner wall, transferring a product into hot water after the reaction is completed, cooling, crystallizing, filtering and drying to obtain the benzoxazolone. The selective release of ammonia gas is realized by optimizing reaction conditions and adopting a polytetrafluoroethylene film, so that the reaction efficiency and the environmental protection property are improved. According to the method, the reaction is carried out under the solvent-free condition, the generation of three wastes is remarkably reduced, the reaction time and temperature are controllable, and high yield and high purity are ensured.

Description

Technical Field

[0001] The invention relates to the technical field of organic synthesis, and in particular to a method for continuously preparing benzoxazolone. Background Art

[0002] Benzoxazolone, CAS: 59-49-4, its molecular formula is C 7 H 5 NO 2 , which has important uses in pesticides, medicine and other fields.

[0003] In the prior art, the synthesis methods of benzoxazolone mainly include the following: 1. 2-aminophenol and urea are subjected to high-temperature cyclization in a sulfuric acid aqueous solution. The byproduct ammonia produced by the method will be directly absorbed by sulfuric acid, but the presence of sulfuric acid will cause certain corrosion damage to the equipment, and the reaction system is complex, and it is easy to produce redundant three wastes. 2. 2-aminophenol and urea are used to synthesize benzoxazolone at high temperature in DMF. This method requires the use of a chromatography column to purify the benzoxazolone in the product, and the yield is low, the operation is complicated, and it is not conducive to industrial production. 3. 2-aminophenol and urea are reacted and synthesized in a horizontal double-helix reactor under molten conditions, and ammonia is discharged by negative pressure. This method has low three wastes, simple post-processing process, and easy operation. However, the horizontal double-helix reactor used in this scheme is suitable for continuous small-scale experiments, not suitable for amplification, and the size of the equipment will directly affect the problems in fluid dynamics, such as uneven boring distribution, low stirring efficiency, etc., which is not conducive to amplification.

[0004] In view of the above-mentioned shortcomings, how to provide a more environmentally friendly and more efficient preparation method of benzoxazolone has become one of the technical problems that need to be solved urgently. Summary of the invention

[0005] In order to solve this problem, a method for continuously preparing benzoxazolone is proposed, which adopts a microchannel reactor as a synthesis process and optimizes the reaction conditions to improve environmental protection and reaction efficiency.

[0006] The technical solution of the present invention is implemented as follows: The present invention provides a method for continuously preparing benzoxazolone, which comprises: continuously inputting molten 2-aminophenol and urea into a microchannel reactor having a partial polytetrafluoroethylene film inner wall, transferring the product into hot water after the reaction is completed, cooling and crystallizing, filtering and drying to obtain benzoxazolone.

[0007] The invention is based on the reaction principle of preparing benzoxazolone by heating reaction under solvent-free conditions using 2-aminophenol and urea as raw materials, adopts a microchannel reactor to replace a conventional intermittent or continuous reactor, solves the problem of uniform external mixing of materials in the conventional reactor during the scale-up production process, and at the same time, by partially arranging a polytetrafluoroethylene film on the inner wall of the microchannel reactor, the reaction byproduct ammonia is released, and the gas generation is prevented from having unnecessary negative effects on the flow rate, pressure and other states of the materials in the microchannel reactor. The preparation method of benzoxazolone can be suitable for industrial scale-up production, and is also suitable for small-scale and pilot tests at the laboratory level.

[0008] In some embodiments, the diameter of the microchannel reactor is 0.5-2 mm, preferably 1 mm.

[0009] In some embodiments, the reaction time of 2-aminophenol and urea in the microchannel reactor is 10-20 min, and the reaction temperature is 100-120°C.

[0010] Due to the use of a microchannel reactor, the material mixing efficiency is higher and the heat transfer efficiency is higher, so the reaction temperature is preferably 100-120°C and the reaction time is preferably 10-20 minutes. Within this temperature range, the reaction speed is faster and the side reactions are less, ensuring a high yield and high purity of benzoxazolone. Shorter reaction time improves production efficiency.

[0011] In some embodiments, the mass flow ratio of 2-aminophenol to urea is 1:(1.1-1.5).

[0012] The optimized molar ratio can ensure a high conversion rate of the reaction, avoid excess or deficiency of reactants, reduce the formation of by-products, and improve the yield of the product.

[0013] In some embodiments, the inner wall of the polytetrafluoroethylene film accounts for 10-25% of the inner wall area of ​​the microchannel reactor.

[0014] Reasonable film coverage can effectively improve the gas separation efficiency, ensure that ammonia can be released in time, avoid the negative impact of accumulation in the reactor on the reaction, and also avoid excessive polytetrafluoroethylene film inner wall affecting the liquid flow resistance, which is not conducive to the flow transmission of materials.

[0015] In some embodiments, the inner walls of the polytetrafluoroethylene films are arranged in an array at equal intervals along the extension direction of the cavity of the microchannel reactor.

[0016] This arrangement helps to evenly distribute the reactants, improve the uniformity of the reaction, ensure the stability of the reaction process, and at the same time ensure that there are channels for rapid gas release throughout the entire flow process in the microchannel reactor.

[0017] In some embodiments, the outer side of the inner wall of the polytetrafluoroethylene film is connected to the negative pressure cavity, and the vacuum degree in the negative pressure cavity is -0.01 MPa to -0.03 MPa.

[0018] The negative pressure environment helps to quickly discharge ammonia and reduce the gas pressure in the reactor, thereby improving the safety and efficiency of the reaction.

[0019] In some embodiments, the pore size of the inner wall of the polytetrafluoroethylene film is 0.1-0.3 μm, and the thickness is 50-100 μm.

[0020] Appropriate pore size and thickness can ensure the selective permeation of ammonia while not affecting the fluidity of the reactants, thereby improving the overall reaction efficiency.

[0021] In some embodiments, the inner wall of the polytetrafluoroethylene film is a hydrophilically modified polytetrafluoroethylene film.

[0022] In some embodiments, the preparation method of the hydrophilic modified polytetrafluoroethylene film includes: preparing PVA into a 10wt% aqueous solution with deionized water as a solvent, heating and stirring until completely dissolved, adding polytetrafluoroethylene particles with a pore size of 0.1-0.3μm, stirring evenly and then coating, drying at room temperature and then drying at 60°C for 2h, and then using air as a gas plasma source to plasma treat the film-formed polytetrafluoroethylene film for 2-5min, with a processing power of 50-100W, to obtain a hydrophilic modified polytetrafluoroethylene film.

[0023] The hydrophilic modification increases the hydrophilicity of the film, helps to improve the reaction environment, promotes the dispersion and mixing of reactants, and improves the reaction efficiency.

[0024] In some embodiments, the hot water temperature is 50-90°C, and the cooling crystallization temperature is 10-30°C.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] The present invention proposes a method for continuously preparing benzoxazolone based on a microchannel reactor, which achieves the selective release of ammonia by optimizing the reaction conditions and using a polytetrafluoroethylene film, thereby improving the reaction efficiency and environmental protection. The method reacts under solvent-free conditions, significantly reduces the generation of three wastes, and the reaction time and temperature are controllable, ensuring high yield and high purity. At the same time, the hydrophilic modification and reasonable layout of the polytetrafluoroethylene film effectively promote the rapid discharge of gas and the mixing of reactants, further improving the overall reaction efficiency. The process is not only suitable for laboratory small-scale tests, but also can meet the needs of industrial large-scale production, and has good application prospects. DETAILED DESCRIPTION

[0027] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0028] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the embodiments of the present invention belong. If the definitions set forth in this section are contrary to or otherwise inconsistent with the definitions set forth in the patents, patent applications, published patent applications, and other publications incorporated herein by reference, the definitions listed in this section take precedence over the definitions incorporated herein by reference.

[0029] Unless otherwise specified, the methods used in the following examples are all conventional methods. Unless otherwise specified, the materials, reagents and instruments used are all conventional materials, reagents and instruments in the art, and can be obtained by those skilled in the art through commercial channels.

[0030] When an amount, concentration or other value or parameter is expressed as a range, a preferred range or a range defined by a series of upper preferred values ​​and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pairing of any range upper limit or preferred value with any range lower limit or preferred value, regardless of whether the range is disclosed separately. For example, when a range of "1 to 5" is disclosed, the described range should be interpreted as including the range "1 to 4", "1 to 3", "1 to 2", "1 to 2 and 4 to 5", "1 to 3 and 5", etc. When a numerical range is described herein, unless otherwise stated, the range is intended to include its end values ​​and all integers and fractions within the range. In the present specification and claims, range definitions can be combined and / or interchanged, and if not otherwise stated, these ranges include all subranges contained therein.

[0031] Example 1

[0032] This embodiment uses a microchannel reactor to continuously prepare benzoxazolone, and the specific method is as follows:

[0033] The diameter of the microchannel is 1 mm, the temperature in the microchannel reactor is 100° C., the mass flow ratio of 2-aminophenol to urea is 1:1.2, one side of the inner wall of the microchannel is provided with a polytetrafluoroethylene film with a semicircular arc surface arranged at intervals, the interval between adjacent polytetrafluoroethylene films is the same as the length of the polytetrafluoroethylene film, the total area of ​​the polytetrafluoroethylene film accounts for 20% of the inner wall area of ​​the microchannel reactor, the pore size of the polytetrafluoroethylene film is 0.2 μm, the thickness is 80 μm, the reaction time is 15 minutes, the reaction product is mixed with 60° C. hot water, the mass flow rate of the hot water is twice the mass flow rate of 2-aminophenol, and then the mixed hot water is cooled to 20° C., filtered, and dried to obtain benzoxazolone.

[0034] Example 2

[0035] This embodiment uses a microchannel reactor to continuously prepare benzoxazolone, and the specific method is as follows:

[0036] The diameter of the microchannel is 0.5 mm, the temperature in the microchannel reactor is 110° C., the mass flow ratio of 2-aminophenol to urea is 1:1.4, wherein one side of the inner wall of the microchannel is provided with a polytetrafluoroethylene film with a semicircular arc surface arranged at intervals, the spacing between adjacent polytetrafluoroethylene films is the same as the length of the polytetrafluoroethylene film, the total area of ​​the polytetrafluoroethylene film accounts for 20% of the inner wall area of ​​the microchannel reactor, the pore size of the polytetrafluoroethylene film is 0.2 μm, the thickness is 80 μm, the reaction time is 15 minutes, the reaction product is mixed with 50° C. hot water, the mass flow rate of the hot water is twice the mass flow rate of 2-aminophenol, and then the mixed hot water is cooled to 10° C., filtered, and dried to obtain benzoxazolone.

[0037] Example 3

[0038] This embodiment uses a microchannel reactor to continuously prepare benzoxazolone, and the specific method is as follows:

[0039] The diameter of the microchannel is 1 mm, the temperature in the microchannel reactor is 120° C., the mass flow ratio of 2-aminophenol to urea is 1:1.5, wherein one side of the inner wall of the microchannel is provided with a polytetrafluoroethylene film with a semicircular arc surface arranged at intervals, the spacing between adjacent polytetrafluoroethylene films is the same as the length of the polytetrafluoroethylene film, the total area of ​​the polytetrafluoroethylene film accounts for 20% of the inner wall area of ​​the microchannel reactor, the pore size of the polytetrafluoroethylene film is 0.2 μm, the thickness is 80 μm, the reaction time is 15 minutes, the reaction product is mixed with 90° C. hot water, the mass flow rate of the hot water is twice the mass flow rate of 2-aminophenol, and then the mixed hot water is cooled to 30° C., filtered, and dried to obtain benzoxazolone.

[0040] Example 3

[0041] This embodiment is based on the embodiment 1, and the only difference is that a polytetrafluoroethylene film with a continuous semicircular arc surface is provided on one side of the inner wall of the microchannel.

[0042] Example 4

[0043] This embodiment is based on the embodiment 1, except that the total area of ​​the polytetrafluoroethylene film accounts for 10% of the inner wall area of ​​the microchannel reactor.

[0044] Example 5

[0045] This embodiment is based on the embodiment 1, except that the total area of ​​the polytetrafluoroethylene film accounts for 25% of the inner wall area of ​​the microchannel reactor.

[0046] Example 6

[0047] This embodiment is based on the embodiment 1, and the only difference is that a negative pressure cavity is provided on the side where the polytetrafluoroethylene film is located to collect ammonia gas under negative pressure, and the vacuum degree of the negative pressure is -0.01 MPa.

[0048] Example 7

[0049] This embodiment is based on the embodiment 1, and the only difference is that a negative pressure cavity is provided on the side where the polytetrafluoroethylene film is located to collect ammonia gas under negative pressure, and the vacuum degree of the negative pressure is -0.02 MPa.

[0050] Example 8

[0051] This embodiment is based on the embodiment 1, and the only difference is that a negative pressure cavity is provided on the side where the polytetrafluoroethylene film is located to collect ammonia gas under negative pressure, and the vacuum degree of the negative pressure is -0.03 MPa.

[0052] Example 9

[0053] This embodiment is based on the embodiment 1, except that the pore size of the polytetrafluoroethylene film is 0.1 μm and the thickness is 50 μm.

[0054] Example 10

[0055] This embodiment is based on the embodiment 1, except that the pore size of the polytetrafluoroethylene film is 0.3 μm and the thickness is 100 μm.

[0056] Embodiment 11

[0057] This embodiment is based on the embodiment 1, and the only difference is that the polytetrafluoroethylene film is a hydrophilic modified polytetrafluoroethylene film, and the preparation method is as follows: PVA is prepared into a 10wt% aqueous solution with deionized water as a solvent, heated and stirred until completely dissolved, polytetrafluoroethylene particles with a pore size of 0.2μm are added, and after stirring evenly, it is coated, dried at room temperature and then dried at 60°C for 2h, and then the film-formed polytetrafluoroethylene film is plasma treated for 3min with air as a gas plasma source, and the processing power is 70W, so as to obtain a hydrophilic modified polytetrafluoroethylene film with a thickness of 80μm.

[0058] Comparative Example 1

[0059] This comparative example is based on Example 1, except that the total area of ​​the polytetrafluoroethylene film accounts for 5% of the inner wall area of ​​the microchannel reactor.

[0060] Comparative Example 2

[0061] This comparative example is based on Example 1, except that the total area of ​​the polytetrafluoroethylene film accounts for 30% of the inner wall area of ​​the microchannel reactor.

[0062] Comparative Example 3

[0063] This comparative example is based on Example 1, except that a negative pressure cavity is provided on the side where the polytetrafluoroethylene film is located to collect ammonia gas under negative pressure, and the negative pressure vacuum degree is -0.05 MPa.

[0064] Comparative Example 4

[0065] This comparative example is based on Example 1, except that no polytetrafluoroethylene film is provided on the inner wall of the microchannel.

[0066] The benzoxazolone prepared in the above examples and comparative examples was tested and the yield was calculated to obtain the results shown in the following table:

[0067]

[0068]

[0069] It can be seen from the above data that Example 1 and its related examples effectively improve the release efficiency of ammonia by setting a polytetrafluoroethylene film on the inner wall of the microchannel, reducing the negative impact on the reaction conditions. In particular, in Examples 6, 7, and 8, by adjusting the negative pressure environment, the emission of ammonia is further improved, and the yield and purity are also improved accordingly. Comparative Example 4 does not set a polytetrafluoroethylene film, resulting in ammonia accumulation, a significant decrease in reaction efficiency, and a low yield and purity (only 70% and 80%).

[0070] In Example 11, the dispersion of the reactants was significantly improved by hydrophilic modification of the polytetrafluoroethylene film, and the overall reaction efficiency was increased, and the yield and purity were both the highest (93% and 98%). In other examples, the reaction environment of the unmodified film was relatively poor, and the yield and purity were lower than those of Example 11.

[0071] Example 3 further improved the reaction rate by increasing the reaction temperature (120°C) and maintaining a suitable flow ratio (1:1.5), and the yield and purity were excellent. The large film area in Comparative Example 2 resulted in obstructed flow and low reaction efficiency (76% and 85%), while the insufficient film area in Comparative Example 1 also resulted in poor ammonia emission and low yield (78% and 88%).

[0072] The optimized reaction time (15 min) and temperature (100-120° C.) showed a trend of improving yield and purity in all examples. If the reaction time is too long or too short, the reaction efficiency and product quality will be affected.

[0073] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for continuously preparing benzoxazolone, characterized in that: The molten 2-aminophenol and urea are continuously introduced into a microchannel reactor with a partial polytetrafluoroethylene film inner wall. After the reaction is completed, the product is transferred to hot water, cooled for crystallization, filtered and dried to obtain benzoxazolone.

2. The method for continuously preparing benzoxazolone according to claim 1, characterized in that: The reaction time of 2-aminophenol and urea in the microchannel reactor is 10-20 minutes, and the reaction temperature is 100-120°C.

3. The method for continuously preparing benzoxazolone according to claim 1, characterized in that: The mass ratio flow rate of 2-aminophenol and urea is 1:(1.1-1.5).

4. The method for continuously preparing benzoxazolone according to claim 1, characterized in that: The inner wall of the polytetrafluoroethylene film accounts for 10-25% of the inner wall area of ​​the microchannel reactor.

5. The method for continuously preparing benzoxazolone according to claim 4, characterized in that: The inner walls of the polytetrafluoroethylene films are arranged in an array with equal spacing along the extension direction of the cavity of the microchannel reactor.

6. The method for continuously preparing benzoxazolone according to claim 4, characterized in that: The outer side of the inner wall of the polytetrafluoroethylene film is connected to the negative pressure cavity, and the vacuum degree in the negative pressure cavity is -0.01MPa to -0.03Mpa.

7. The method for continuously preparing benzoxazolone according to claim 1, characterized in that: The pore size of the inner wall of the polytetrafluoroethylene film is 0.1-0.3 μm, and the thickness is 50-100 μm.

8. The method for continuously preparing benzoxazolone according to claim 1, characterized in that: The inner wall of the polytetrafluoroethylene film is a hydrophilic modified polytetrafluoroethylene film.

9. The method for continuously preparing benzoxazolone according to claim 8, characterized in that: The preparation method of the hydrophilic modified polytetrafluoroethylene film comprises: preparing a 10wt% aqueous solution of PVA with deionized water as a solvent, heating and stirring until completely dissolved, adding polytetrafluoroethylene particles with a pore size of 0.1-0.3μm, stirring evenly and then coating, drying at room temperature and then drying at 60°C for 2h, and then using air as a gas plasma source to perform plasma treatment on the film-formed polytetrafluoroethylene film for 2-5min at a treatment power of 50-100W to obtain a hydrophilic modified polytetrafluoroethylene film.

10. The method for continuously preparing benzoxazolone according to claim 1, characterized in that: The hot water temperature is 50-90℃, and the cooling crystallization temperature is 10-30℃.

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