CN108164460B - Method for preparing 3-methylpyridine-N-oxide - Google Patents
Method for preparing 3-methylpyridine-N-oxide Download PDFInfo
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- C07D213/00—Heterocyclic compounds containing six-membered rings, not condensed with other rings, with one nitrogen atom as the only ring hetero atom and three or more double bonds between ring members or between ring members and non-ring members
- C07D213/02—Heterocyclic compounds containing six-membered rings, not condensed with other rings, with one nitrogen atom as the only ring hetero atom and three or more double bonds between ring members or between ring members and non-ring members having three double bonds between ring members or between ring members and non-ring members
- C07D213/89—Heterocyclic compounds containing six-membered rings, not condensed with other rings, with one nitrogen atom as the only ring hetero atom and three or more double bonds between ring members or between ring members and non-ring members having three double bonds between ring members or between ring members and non-ring members with hetero atoms directly attached to the ring nitrogen atom
Abstract
A method for preparing 3-methylpyridine-N-oxide, belonging to the synthesis technology of pesticide/pharmaceutical chemical intermediates. According to the invention, 3-methylpyridine and hydrogen peroxide are rapidly mixed in a micro mixer and oxidized in a micro reactor under a high temperature condition, and the generated 3-methylpyridine-N-oxide solution is subjected to flash evaporation to obtain the product. Compared with the prior art, the oxidation reaction process is carried out in the microreactor, the heat exchange characteristic is better, the controllability of the reaction is enhanced, the reaction hot spot in equipment is eliminated, and the upper limit of the operation temperature is improved; in addition, the content of the micro mixer is easy to realize rapid mixing, uniform reaction environment is instantly achieved, reaction efficiency is improved, and reaction flux is easy to realize amplification; the process is optimized, the utilization efficiency of the hydrogen peroxide is higher, and the energy consumption of the subsequent purification and other processes can be reduced while the raw materials are saved.
Description
Technical Field
The invention relates to a preparation method of 3-methylpyridine-N-oxide, belonging to the technical field of synthesis of pesticide/pharmaceutical chemical intermediates.
Background
3-methylpyridine-N-OXIDE (3-METHYLPYRIDINE N-OXIDE) is generally white to light yellow crystal and is an intermediate for the synthesis of important drugs such as imidacloprid, acetamiprid and the like. At present, 2-chloro-3-methylpyridine and 2-chloro-5-methylpyridine synthesized by the reaction of 3-methylpyridine-N-oxide and phosphorus oxychloride are widely applied to the synthesis of pesticides and medicines.
In the current research (CN102718705B, CN105001155A, CN104974088B, CN 106749000a), hydrogen peroxide is generally used as the oxidant, wherein the mass fraction of hydrogen peroxide is between 25% and 30%. Under the action of catalyst (titanium-silicon molecular sieve, transition metal oxide or its salt, etc.), under the condition of heating it reacts with 3-methylpyridine raw material in the presence of catalyst to obtain the invented product. Specifically, a certain amount of 3-methylpyridine is added into a reaction kettle, acid and a catalyst are added, hydrogen peroxide is dropwise added in batches at the temperature of 60-75 ℃, then the temperature is kept for 7-8 hours, and then flash evaporation is carried out to obtain the 3-methylpyridine-N-oxide. Because the oxidation reaction releases heat, and oxygen generated by the decomposition of the hydrogen peroxide is an efficient combustion improver, a series of troublesome problems of slow temperature response, long reaction period, difficult amplification and the like exist in the actual operation process of the process, and the energy consumption and the material consumption in the production process are greatly increased. Therefore, it is necessary to develop a more efficient and safe synthesis technique.
Disclosure of Invention
The invention aims to provide a method for preparing 3-methylpyridine-N-oxide, which aims to solve a series of troublesome problems of slow temperature response, long reaction period, difficult amplification and the like in the actual operation process, further reduce the energy consumption and material consumption in the production process and further enable the preparation process to be carried out more efficiently and more safely.
The technical scheme of the invention is as follows:
a process for preparing 3-methylpyridine-N-oxide, characterized in that it comprises the following steps:
1) uniformly mixing the feed liquid A of the 3-methylpyridine and a catalyst in a storage tank A to prepare feed liquid A, wherein the catalyst accounts for 1-5% of the mass fraction of the 3-methylpyridine; simultaneously, placing a hydrogen peroxide feed liquid B in a storage tank B;
2) conveying the feed liquid A and the feed liquid B into a micro mixer, so that the average flow velocity of the total flow of the feed liquid A and the feed liquid B at a mixing position is at least 1m/s, and obtaining a mixed liquid C; carrying out oxidation reaction on the mixed solution C in a high-temperature reaction section of the microreactor at the temperature of 75-90 ℃ to obtain a reaction solution D containing 3-methylpyridine-N-oxide;
3) cooling the reaction solution D to 20-30 ℃ in a low-temperature cooling section of the microreactor, conveying the reaction solution D back to the storage tank A, mixing the reaction solution D with the original feed liquid in the storage tank A under stirring until the feed liquid in the storage tank B is completely mixed with the feed liquid A through the micromixer and reacts, and obtaining a mixed solution E containing 3-methylpyridine-N-oxide in the storage tank A;
4) inputting the mixed solution E into a microreactor for reaction, introducing the reaction liquid after the reaction into a storage tank A, stopping introducing the solution E until the concentration of hydrogen peroxide in the storage tank A reaches or is lower than 1%, pumping the reaction liquid in the microreactor into the storage tank A, and obtaining a solution F containing 3-methylpyridine-N-oxide in the storage tank A;
5) carrying out flash evaporation on the solution F obtained in the step 4) in a flash evaporation tank to evaporate the 3-methylpyridine-N-oxide, and carrying out fractional condensation and drying on the evaporated 3-methylpyridine-N-oxide to obtain a product of the 3-methylpyridine-N-oxide; and recovering and reusing the residual solid containing the catalyst after flash evaporation.
Preferably, the catalyst adopts a mixture of phosphomolybdic acid and molybdenum trioxide, wherein the mass ratio of the phosphomolybdic acid to the molybdenum trioxide is 1: 2 to 2: 1.
Preferably, in step 1), the purity of the 3-methylpyridine used should be greater than or equal to 80%; the mass fraction of the hydrogen peroxide is 25-35%, and the pH value of the hydrogen peroxide is buffered to be 3.8-4.2 by using a phosphate buffer solution.
Preferably, the molar ratio of hydrogen peroxide to 3-methylpyridine in the step 2) is 1.1-1.2: 1.
in the above technical scheme, the micro mixer preferably adopts a micro channel mixer, a membrane dispersion micro mixer or a micro sieve mixer.
The invention is also characterized in that: a stirring device is arranged in the storage tank A, and the temperature of the storage tank A (1) is controlled to be 20-30 ℃.
More preferably, in step 3), the mixed solution C is reacted in the microreactor for a time period sufficient to ensure that the concentration of hydrogen peroxide in the reaction solution D at any given moment is 5% or less.
Compared with the prior art, the invention has the following advantages and prominent technical effects: according to the invention, a micro-reaction process is utilized, the 3-methylpyridine-catalyst mixture and hydrogen peroxide are rapidly mixed in a micro-mixer, and an oxidation reaction is carried out in a micro-reactor under a high-temperature condition, compared with the existing research, the oxidation reaction needing to be heated is improved from a reaction kettle to be carried out in the micro-reactor, so that a container containing a large amount of feed liquid can be effectively prevented from being directly heated, and the accurate control of the reaction can be more easily realized; under the process, the heat exchange capacity of equipment is greatly enhanced, the oxidation reaction can be safely and stably carried out at the temperature of 90 ℃, the reaction rate of the oxidation reaction is higher, the raw material consumption is lower, the time required by single batch reaction is shorter, and the subsequent flash separation cost of the product liquid is lower; the two streams of fluid are quickly and efficiently mixed in the micro mixer, a uniform reaction environment is instantly achieved, and the reaction efficiency is high; the flux amplification process of the micro-reaction process is simple, so that the amplification of industrial production is easier to realize.
Drawings
FIG. 1 is a process flow diagram of the present invention.
In the figure: 1- -A storage tank; 2-B storage tank; 3-3-methylpyridine and a catalyst delivery pump; 4-hydrogen peroxide delivery pump; 5-a micro mixer; 6-a microreactor high-temperature reaction section; 7-a microreactor low-temperature cooling section; 8-a flash separator; 9-3-methylpyridine-N-oxide product; and (5) recycling the 10-catalyst.
Detailed Description
The invention is further illustrated with reference to the following figures and examples.
Referring to fig. 1, the present invention provides a method for preparing 3-methylpyridine-N-oxide, which specifically comprises the following steps:
1) placing the feed liquid A of the 3-methylpyridine and the catalyst in a storage tank A1 to uniformly mix the feed liquid A and the catalyst at normal temperature, wherein a stirring device is arranged in the storage tank A1 to keep stirring, so that the feed liquid in the storage tank A1 is always in a uniform state, and the catalyst accounts for 1-5% of the mass fraction of the 3-methylpyridine; the catalyst is preferably a mixture of phosphomolybdic acid and molybdenum trioxide, and the mass ratio of the phosphomolybdic acid to the molybdenum trioxide is 1: 2-2: 1, other catalysts with the effect of catalyzing the reaction can be used, such as titanium silicalite molecular sieves, transition metal oxides or salts thereof, and the like; the purity of the 3-methylpyridine used should be greater than or equal to 80%; the mass fraction of the hydrogen peroxide is preferably between 25 and 35 percent, and the hydrogen peroxide needs to be buffered by a phosphate buffer solution, so that the pH value of the hydrogen peroxide is between 3.8 and 4.2. Meanwhile, placing a hydrogen peroxide feed liquid B in a storage tank B2; and controlling the low-temperature cooling section 7 of the microreactor to enable the temperature of the storage tank A1 to be always between 20 and 30 ℃ in the operation process.
2) Conveying the feed liquid A and the feed liquid B into a micro mixer 5, and quickly mixing at normal temperature to obtain a mixed liquid C; wherein the molar ratio of hydrogen peroxide to 3-methylpyridine is preferably 1.1-1.2: 1, which is the material condition that ensures that the reaction is fully taking place; the average flow velocity of the total flow of the feed liquid A and the feed liquid B at the mixing position during mixing is at least 1m/s, which is an important condition for ensuring that the feed liquid A and the feed liquid B realize rapid mixing and further rapid reaction in a micro mixer; the flow rate of the mixing part is ensured to ensure that the molar ratio of the hydrogen peroxide to the 3-methylpyridine is 0.05-0.25: 1, the arrangement helps to enhance the controllability of the reaction, and reduce the decomposition of hydrogen peroxide while sufficiently accelerating the main reaction; mixing to obtain a mixed solution C, and carrying out oxidation reaction on the mixed solution C in a high-temperature reaction section 6 of the microreactor at the temperature of 75-90 ℃ to obtain a reaction solution D containing 3-methylpyridine-N-oxide; the reaction time in the high-temperature reaction section 6 of the microreactor is such that the concentration of hydrogen peroxide in the reaction solution D at any time is equal to or lower than 5%.
The micro mixer can adopt a micro channel mixer, a membrane dispersion micro mixer or a micro sieve mixer and other mixing devices with quick mixing effect, such as the micro mixers introduced in patents CN200510012114.9 and CN200710177813.8, can realize high-efficiency mixing between two streams of fluid, and instantly achieve uniform reaction environment, and other devices capable of realizing quick mixing can also be used in the invention.
3) Cooling the reaction solution D to below 30 ℃ in a low-temperature cooling section 7 of the microreactor, generally at 20-30 ℃, then conveying the reaction solution D back to the storage tank A1, mixing the reaction solution D with the original feed liquid in the storage tank A1 under stirring until the feed liquid in the storage tank B2 is completely mixed with the feed liquid A through the micromixer 5 and reacts, and then conveying the reaction solution D into the storage tank A1; a, a storage tank 1 needs to be subjected to heat preservation treatment, and the temperature of the storage tank is controlled to be 20-30 ℃ through cooling; obtaining a mixed solution E containing 3-methylpyridine-N-oxide in a storage tank 1A;
4) inputting the mixed solution E into a high-temperature reaction section 6 of the microreactor for reaction, introducing the reaction liquid after the reaction into a storage tank A1, and stopping introducing the solution E until the concentration of hydrogen peroxide in the storage tank A1 reaches or is lower than 1% to obtain a solution F containing 3-methylpyridine-N-oxide;
5) carrying out flash evaporation on the solution F obtained in the step 4) in a flash evaporation tank 8 to evaporate the 3-methylpyridine-N-oxide, and carrying out fractional condensation and drying on the evaporated 3-methylpyridine-N-oxide to obtain a product of the 3-methylpyridine-N-oxide; and recovering the residual solid containing the catalyst after the flash evaporation, and adding the recovered solid into the storage tank 1A for continuous use.
The following specific examples are set forth to provide a further understanding of the invention to those of ordinary skill in the art.
Example 1
1) Weighing 240g of 3-methylpyridine and 2.4g of catalyst to prepare a feed liquid A, weighing 275g of 35 wt% hydrogen peroxide solution, and stabilizing the solution to pH 4 by using a phosphate buffer solution to prepare a feed liquid B; wherein the catalyst is phosphomolybdic acid and molybdenum trioxide according to the mass ratio of 2: 1 are mixed.
2) Controlling the heating temperature of the high-temperature reaction section 6 of the microreactor to be 75 ℃, and respectively introducing the feed liquid A and the feed liquid B obtained in the step 1) into a micromixer 5 at the flow rates of 50mL/min and 2mL/min, wherein A is a continuous phase, B is a dispersed phase, the structure of the micromixer 5 is disclosed in patent CN200510012114.9, 5 parallel channels are contained, and a 10-micron stainless steel porous medium is used as a dispersion medium. The retention time of the mixed liquid C in the high-temperature reaction section 6 of the micro-reactor is 4 min. After about 2 hours, the mixing and reaction process is completed, the product solution in the storage tank A1 is calibrated by using ultra-high performance liquid chromatography, and the yield of the 3-methylpyridine-N-oxide reaches 82.4 percent.
Example 2
1) Weighing 240g of 3-methylpyridine and 9.6g of catalyst to prepare a feed liquid A, weighing 275g of 35 wt% hydrogen peroxide solution, and stabilizing the solution to pH 4 by using a phosphate buffer solution to prepare a feed liquid B; wherein the catalyst is phosphomolybdic acid and molybdenum trioxide according to the mass ratio of 1: 1 are mixed.
2) Controlling the heating temperature of the high-temperature reaction section 6 of the microreactor to be 90 ℃, and respectively introducing the feed liquid A and the feed liquid B obtained in the step 1) into a micromixer 5 at the flow rates of 50mL/min and 5mL/min, wherein A is a continuous phase, B is a dispersed phase, the structure of the micromixer 5 is disclosed in patent CN200510012114.9, 5 parallel channels are contained, and a 10-micron stainless steel porous medium is used as a dispersion medium. The retention time of the mixed liquid C in the high-temperature reaction section 6 of the micro-reactor is 6 min. After about 0.8h, the mixing and reaction process is completed, the product solution in the storage tank A1 is calibrated by using ultra-high performance liquid chromatography, and the yield of the 3-methylpyridine-N-oxide reaches 90.7 percent.
Example 3
1) Weighing 240g of 3-methylpyridine and 12.0g of catalyst to prepare a feed liquid A, weighing 360g of 27 wt% hydrogen peroxide solution, and stabilizing the solution to pH 4 by using a phosphate buffer solution to prepare a feed liquid B; wherein the catalyst is phosphomolybdic acid and molybdenum trioxide according to the mass ratio of 1: 2, mixing the components.
2) Controlling the heating temperature of the high-temperature reaction section 6 of the microreactor to be 80 ℃, and respectively introducing the feed liquid A and the feed liquid B obtained in the step 1) into a micromixer 5 at the flow rates of 50mL/min and 5mL/min, wherein A is a continuous phase, B is a dispersed phase, the structure of the micromixer 5 is disclosed in patent CN200510012114.9, 10 parallel channels are contained, and a stainless steel porous medium of 10 micrometers is used as a dispersion medium. The retention time of the mixed liquid C in the high-temperature reaction section 6 of the micro-reactor is 4 min. After about 2.6 hours of mixing and reaction, the yield of the 3-methylpyridine-N-oxide reaches 91.0 percent by using ultra-high performance liquid chromatography for calibration.
Example 4
1) 480g of 3-methylpyridine and 24g of catalyst are weighed to prepare a feed liquid A, 550g of 35 wt% hydrogen peroxide solution is weighed, and a phosphate buffer solution is used for stabilizing the pH value to 4 to prepare a feed liquid B; wherein the catalyst is phosphomolybdic acid and molybdenum trioxide according to the mass ratio of 1: 1 are mixed.
2) And (2) controlling the heating temperature of the high-temperature reaction section 6 of the microreactor to be 85 ℃, and introducing the feed liquid A and the feed liquid B obtained in the step (1) into a micromixer 5 at the flow rates of 100mL/min and 5mL/min respectively, wherein A is a continuous phase, B is a disperse phase, the structure of the micromixer 5 is disclosed in patent CN200710177813.8, and the number of parallel channels is 10. The retention time of the mixed liquid C in the high-temperature reaction section 6 of the micro-reactor is 2 min. The mixing and reaction process is completed in about 1.6h to obtain a product solution E1, and the yield of the 3-methylpyridine-N-oxide reaches 85.0 percent by using ultra-high performance liquid chromatography for calibration.
3) And (3) reducing the temperature of the high-temperature reaction section 6 of the microreactor to 75 ℃, and continuously circulating the solution E12h to further convert the reaction to obtain a final product solution F. The yield of the 3-methylpyridine-N-oxide reaches 90.4 percent by using ultra-high performance liquid chromatography for calibration.
Example 5
1) 1000g of 3-methylpyridine and 30g of catalyst are weighed to prepare feed liquid A, 1200g of 35 wt% hydrogen peroxide solution is weighed, and the solution is stabilized to pH 4 by using phosphate buffer to prepare feed liquid B. Equally dividing the feed liquid B into B1 and B2 for later use; wherein the catalyst is phosphomolybdic acid and molybdenum trioxide according to the mass ratio of 1: 1 are mixed.
2) Controlling the temperature of the high-temperature reaction section 6 of the microreactor to be 85 ℃, and respectively introducing the feed liquid A and the feed liquid B1 obtained in the step 1) into a micromixer 5 at the flow rates of 200mL/min and 20mL/min, wherein A is a continuous phase, B1 is a dispersed phase, and the structure of the micromixer 5 is disclosed in patent CN201110179977.0, wherein the number of through grooves on the first fluid distribution plate is 1, the width of each through groove is 2mm, and the length-width ratio is 5. The number of logical groove on the fluid mixing plate is 1, and the width that leads to the groove is 1mm, and the degree of depth is 0.3 mm. The retention time of the mixed liquid C in the high-temperature reaction section 6 of the micro-reactor is 2 min. The mixing and reaction process was completed for about 0.5h to obtain a product solution E1.
3) Controlling the heating temperature of the high-temperature reaction section 6 of the microreactor to be 85 ℃, and respectively introducing the feed liquid E1 and the feed liquid B2 obtained in the step 2) into a micromixer at the flow rates of 200mL/min and 10mL/min, wherein E1 is a continuous phase, B2 is a disperse phase, and the structure of the micromixer 5 is as described in the step (2). The retention time of the mixed liquid C in the high-temperature reaction section 6 of the micro-reactor is 2 min. The mixing and reaction process is completed in about 1h to obtain a product solution E2, and the yield of the 3-methylpyridine-N-oxide reaches 87.0 percent by using ultra-high performance liquid chromatography for calibration.
4) And (3) reducing the temperature of the high-temperature reaction section 6 of the microreactor to 75 ℃, and continuously circulating the solution E21h to obtain a final product solution F. The yield of the 3-methylpyridine-N-oxide reaches 94.6 percent by using ultra-high performance liquid chromatography for calibration.
Example 6
1) 1000g of 3-methylpyridine and 30g of catalyst are weighed to prepare feed liquid A, 1400g of 30 wt% hydrogen peroxide solution is weighed, and the solution is stabilized to pH 4 by using phosphate buffer to prepare feed liquid B. Equally dividing the feed liquid B into B1 and B2 for later use; wherein the catalyst is phosphomolybdic acid and molybdenum trioxide according to the mass ratio of 1: 1 are mixed.
2) Controlling the temperature of the high-temperature reaction section 6 of the microreactor to be 85 ℃, and respectively introducing the feed liquid A and the feed liquid B1 obtained in the step 1) into a micromixer 5 at the flow rates of 200mL/min and 20mL/min, wherein A is a continuous phase, B1 is a dispersed phase, and the structure of the micromixer 5 is disclosed in patent CN201110179977.0, wherein the number of through grooves on the first fluid distribution plate is 1, the width of each through groove is 2mm, and the length-width ratio is 5. The number of logical groove on the fluid mixing plate is 1, and the width that leads to the groove is 1mm, and the degree of depth is 0.3 mm. The mixing and reaction process was completed for about 0.5h to obtain a product solution E1.
3) Controlling the temperature of the high-temperature reaction section 6 of the microreactor to be 85 ℃, and respectively introducing the feed liquid E1 and the feed liquid B2 obtained in the step 2) into the micromixer 5 at the flow rates of 200mL/min and 10mL/min, wherein E1 is a continuous phase, B2 is a disperse phase, and the structure of the micromixer 5 is as described in the step (2). The retention time of the mixed liquid C in the high-temperature reaction section 6 of the micro-reactor is 2 min. The mixing and reaction process is completed in about 1h to obtain a product solution E2, and the yield of the 3-methylpyridine-N-oxide reaches 85.7 percent by using ultra-high performance liquid chromatography for calibration.
4) And (3) reducing the temperature of the high-temperature reaction section 6 of the microreactor to 75 ℃, and continuously circulating the solution E21h to obtain a final product solution F. The yield of the 3-methylpyridine-N-oxide reaches 94.1 percent by using ultra-high performance liquid chromatography for calibration.
Claims (5)
1. A process for preparing 3-methylpyridine-N-oxide, characterized in that it comprises the following steps:
1) uniformly mixing the feed liquid A of the 3-methylpyridine and a catalyst in a storage tank (1) A to prepare feed liquid A, wherein the catalyst accounts for 1-5% of the mass fraction of the 3-methylpyridine; meanwhile, placing a hydrogen peroxide feed liquid B in a storage tank B (2); the catalyst adopts a mixture of phosphomolybdic acid and molybdenum trioxide, wherein the mass ratio of the phosphomolybdic acid to the molybdenum trioxide is 1: 2-2: 1;
2) conveying the feed liquid A and the feed liquid B into a micro mixer (5) to ensure that the average flow velocity of the total flow of the feed liquid A and the feed liquid B at a mixing position is at least 1m/s, so as to obtain a mixed liquid C; the mixed solution C is subjected to oxidation reaction in a microreactor high-temperature reaction section (6) at the temperature of 75-90 ℃ to obtain a reaction solution D containing 3-methylpyridine-N-oxide; the molar ratio of the total amount of the hydrogen peroxide and the 3-methylpyridine fed is 1.1-1.2: 1, and the flow rate at the mixing part ensures that the molar ratio of the hydrogen peroxide to the 3-methylpyridine is 0.05-0.25: 1;
3) cooling the reaction solution D in a low-temperature cooling section (7) of the microreactor to 20-30 ℃, then conveying the cooled reaction solution D back to the storage tank A (1), mixing the cooled reaction solution D with the original feed liquid in the storage tank A (1) under stirring until the feed liquid in the storage tank B (2) is completely mixed with the feed liquid A through the micromixer (5) and reacts, and obtaining a mixed solution E containing 3-methylpyridine-N-oxide in the storage tank A (1);
4) inputting the mixed solution E into the microreactor high-temperature reaction section (6) for reaction, introducing the reaction liquid after the reaction into the A storage tank (1), stopping introducing the solution E until the concentration of hydrogen peroxide in the A storage tank (1) reaches or is lower than 1%, pumping out the reaction liquid in the microreactor high-temperature reaction section (6) and the microreactor low-temperature cooling section (7) into the A storage tank (1), and obtaining a solution F containing 3-methylpyridine-N-oxide in the A storage tank (1);
5) carrying out flash evaporation on the solution F obtained in the step 4) in a flash separator (8) to evaporate the 3-methylpyridine-N-oxide, and condensing and drying the evaporated 3-methylpyridine-N-oxide step by step to obtain a product of the 3-methylpyridine-N-oxide; and recovering and reusing the residual solid containing the catalyst after flash evaporation.
2. A process for preparing 3-methylpyridine-N-oxide according to claim 1, wherein: in the step 1), the purity of the used 3-methylpyridine is more than or equal to 80 percent; the mass fraction of the hydrogen peroxide is 25-35%, and the pH value of the hydrogen peroxide is buffered to be 3.8-4.2 by using a phosphate buffer solution.
3. The method of claim 1, wherein the micromixer is a microchannel mixer, a membrane dispersion micromixer, or a micromesh mixer.
4. The method for preparing 3-methylpyridine-N-oxide according to claim 1, wherein the A tank (1) is provided with a stirring device, and the temperature of the A tank (1) is controlled between 20 ℃ and 30 ℃.
5. The method of claim 1, wherein the mixed solution C is reacted in the high temperature reaction zone of the microreactor in step 2) for a time period equal to or less than 5% of the hydrogen peroxide concentration in the reaction solution D at any given time.
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| CN1736577A (en) * | 2005-07-08 | 2006-02-22 | 清华大学 | Multi-channeled micro-structured reactor |
| CN102942523A (en) * | 2012-12-05 | 2013-02-27 | 寿光富康制药有限公司 | Preparation method of omeprazole intermediate 2,3,5-trimethylpyridyl-N-oxide |
| CN103570617A (en) * | 2013-11-15 | 2014-02-12 | 浙江荣凯化工科技有限公司 | Preparation method of 3-cyano-pyridine N-oxide |
| CN104447531A (en) * | 2014-11-27 | 2015-03-25 | 爱斯特（成都）生物制药有限公司 | Preparation method of 3,5-dibromopyridine-N-oxide |
| CN105153019A (en) * | 2015-08-10 | 2015-12-16 | 安徽国星生物化学有限公司 | 2-pyridinemethanol and synthetic method thereof |
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Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1736577A (en) * | 2005-07-08 | 2006-02-22 | 清华大学 | Multi-channeled micro-structured reactor |
| CN102942523A (en) * | 2012-12-05 | 2013-02-27 | 寿光富康制药有限公司 | Preparation method of omeprazole intermediate 2,3,5-trimethylpyridyl-N-oxide |
| CN103570617A (en) * | 2013-11-15 | 2014-02-12 | 浙江荣凯化工科技有限公司 | Preparation method of 3-cyano-pyridine N-oxide |
| CN104447531A (en) * | 2014-11-27 | 2015-03-25 | 爱斯特（成都）生物制药有限公司 | Preparation method of 3,5-dibromopyridine-N-oxide |
| CN105153019A (en) * | 2015-08-10 | 2015-12-16 | 安徽国星生物化学有限公司 | 2-pyridinemethanol and synthetic method thereof |
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