阅读说明：本技术 一种2-甲基-5硝基咪唑连续硝化工艺 (2-methyl-5 nitroimidazole continuous nitration process ) 是由 杨战厂 高倩 于 2021-10-20 设计创作，主要内容包括：本发明公开了一种2-甲基-5硝基咪唑连续硝化工艺,其生产工艺包括以下歩骤：发烟硝酸与硫酸铵混合形成A混合物；复合催化剂浓硫酸-醋酐与2-甲基咪唑-混合形成B混合物。两组混合物,分别由稳流输送泵送入多段微管式反应器中进行反应,反应完成液连续加水终止反应后,再进行中和、分离、烘干得到成品。本发明的优点：通过该工艺可实现2-甲基-5硝基咪唑硝化工段的低温连续反应、平稳、安全、高效、高转化率、降低硝酸用量等效果。(The invention discloses a 2-methyl-5 nitroimidazole continuous nitration process, which comprises the following steps: mixing fuming nitric acid and ammonium sulfate to form a mixture A; the composite catalyst concentrated sulfuric acid-acetic anhydride and 2-methylimidazole are mixed to form a mixture B. And feeding the two groups of mixtures into a multi-section micro-tube type reactor for reaction by a steady flow conveying pump, continuously adding water into the reaction solution after the reaction is finished, and then neutralizing, separating and drying to obtain a finished product. The invention has the advantages that: the process can realize the effects of low-temperature continuous reaction, stability, safety, high efficiency, high conversion rate, reduction of the dosage of nitric acid and the like in the nitration section of the 2-methyl-5 nitroimidazole.)

1. A2-methyl-5 nitroimidazole continuous nitration process is characterized in that: which comprises the following steps:

firstly, dissolving ammonium sulfate in fuming nitric acid to form a mixture A;

dissolving 2-methylimidazole in a concentrated sulfuric acid-acetic anhydride composite catalyst to form a mixture B;

step three, respectively feeding the mixture A and the mixture B into a multi-section micro-tube reactor for reaction through a mixture A steady flow delivery pump (1) and a mixture B steady flow delivery pump (2) in sequence;

and step four, continuously injecting water to stop the reaction after the reaction finished liquid flows out of the multi-section micro-tube reactor.

2. The continuous nitration process of 2-methyl-5-nitroimidazole according to claim 1, characterized in that: the mass fraction of fuming nitric acid in the first step is more than or equal to 98%, the mass ratio of fuming nitric acid to ammonium sulfate is 2.5-3.5, the mass fraction of concentrated sulfuric acid in the second step is more than or equal to 98%, and the mass ratio of concentrated sulfuric acid to 2-methylimidazole is 1.5-2.5; the mass ratio of the acetic anhydride to the 2-methylimidazole is 1.5-3.

3. The continuous nitration process of 2-methyl-5-nitroimidazole according to claim 1, characterized in that: and in the third step, the mixture A steady flow conveying pump (1) and the mixture B steady flow conveying pump (2) are three-pump-head diaphragm metering pumps with the phase difference of 120 degrees.

4. The continuous nitration process of 2-methyl-5-nitroimidazole according to claim 1, characterized in that: the mixture A and the mixture B are respectively injected into the mixer I (3) by a mixture A steady flow delivery pump (1) and a mixture B steady flow delivery pump (2) and then sequentially enter a multi-stage micro-tube reactor for reaction, the multi-stage micro-tube reactor is formed by mutually connecting a plurality of micro-tube reactors in series, and the number of stages of the multi-stage micro-tube reactor is more than or equal to 2.

5. The continuous nitration process of 2-methyl-5-nitroimidazole according to claim 1, characterized in that: the multistage micro-tube reactor consists of a first-stage reactor (4), a second-stage reactor (5), a third-stage reactor (6) and a fourth-stage reactor (7), mixed liquid from the mixer I (3) sequentially enters the first-stage reactor (4), the second-stage reactor (5), the third-stage reactor (6) and the fourth-stage reactor (7), reaction completion liquid flowing out of the fourth-stage reactor (7) enters a mixer II (8), and meanwhile, continuous water injection and dilution are carried out on the reaction completion liquid through a water injection pump (9) until the reaction is terminated.

6. The continuous nitration process of 2-methyl-5-nitroimidazole according to claim 4, wherein: the microtube reactor comprises a plurality of microtubes (10) and a sleeve (11) which are parallel, the plurality of microtubes (10) are parallel to each other and are arranged in the sleeve (11), the lower end of the microtube (10) is connected with a distribution disc (12), the lower end of the distribution disc (12) is connected with a reaction liquid feeding hole (13), the upper end of the microtube (10) is connected with a collection disc (14), the upper end of the collection disc (14) is connected with a reaction liquid discharging hole (15), the lower end of one side of the sleeve (11) is connected with a circulating warm water inlet (16), and the upper end of the other side of the sleeve is connected with a circulating warm water outlet (17).

7. The continuous nitration process of claim 6, wherein the nitration process comprises the following steps: the number of the parallel microtubes (10) in each microtube reactor is more than or equal to 10, the microtubes (10) are made of 316 stainless steel, and the inner diameter of each microtube (10) is 0.5-6 mm.

8. The continuous nitration process of claim 6, wherein the nitration process comprises the following steps: the temperature of the circulating warm water is 40-60 ℃, the reaction temperature of materials in the micro-tube reactor is 40-70 ℃, the temperature of the mixture A is controlled to be 25-35 ℃, the temperature of the mixture B is controlled to be 25-45 ℃, the temperature of the mixture A is controlled not to exceed 50 ℃ in the preparation process, and the temperature of the mixture B is controlled not to exceed 100 ℃ in the preparation process.

9. The continuous nitration process of 2-methyl-5-nitroimidazole according to claim 1, characterized in that: the mass flow ratio of the mixture A to the mixture B is as follows: 0.2-0.3, and sequentially feeding the mixture A and the mixture B into the multi-section micro-tube reactor for reaction by a mixture A steady flow conveying pump (1) and a mixture B steady flow conveying pump (2) respectively, wherein the total reaction time is not less than 15 seconds.

10. The continuous nitration process of 2-methyl-5-nitroimidazole according to claim 1, characterized in that: and after the reaction finished liquid flows out of the multi-section micro-tube reactor, continuously injecting water to stop the reaction, wherein the volume of the injected water is more than or equal to the volume of the total reaction liquid.

Technical Field

The invention relates to a 2-methyl-5 nitroimidazole continuous nitration process, and belongs to the technical field of micro-reactions.

Background

In recent years, microreaction has been used in nitration reactions, and the production of 2-methyl-5-nitroimidazole has also begun to search for a microreaction technical route. CN20170834974.3, application No. 201910495647.9, application No. 202010731906.6, application No. 202010358018.4, application No. CN202011637985.1 and the like disclose a micro-reaction synthesis technology related to the synthesis of 2-methyl-5 nitroimidazole.

The prior micro-reaction technology has the following technical problems: the production process is unstable, the energy consumption is high, the equipment processing and investment are large, great safety risks exist, the industrial production is difficult to realize, and the like.

In the practice 201910495647.9 of the applicant, it is found that when the concentrated sulfuric acid-ammonium sulfate 2 methylimidazole compound A described in claim 1 is prepared, the temperature of the concentrated sulfuric acid is controlled to be 5-15 ℃ in the early stage, and during industrial production, refrigeration equipment is required for maintenance, so that additional energy consumption and equipment investment are increased; 2. the material B is stored in the material B tank at 5-15 ℃ in the same way, so that refrigeration equipment and extra energy consumption are increased; 3. in claim 1, the material A is delivered to a SiC/tetrafluoro microchannel reactor by a first tetrafluoro pump in step 3, the material A is dosed according to the concentrated sulfuric acid-ammonium sulfate-2-methylimidazole ratio described in claim 2 by the applicant, the temperature of the material A is 10-120 ℃ according to the claim 1, the material A is found to be almost solid at 10-60 ℃, the material A cannot be delivered by the tetrafluoro pump in step three, the temperature is high when the material A is delivered at 60-120 ℃, the damage to the tetrafluoro pump is large, the pump delivery is not favorable, the pump output is difficult to output stable flow, the production process is unstable, when the reaction is carried out at the reaction temperature described in step 3, the output of the reactor is unstable, a large amount of yellowish-brown nitric acid smoke is generated, and the industrialization is difficult to realize in practice 201910495647.9.

The applicant has found that when 202010731906.6 is practiced, the effluent liquid from the outlet of the microreactor generates a large amount of gas and brownish-yellow soot without using ammonium sulfate, the pressure fluctuation in the reaction process is large and unstable, the temperature of the reaction liquid collected in the aging kettle continuously rises, (indicating that the reaction does not completely react in the microreactor), and the large amount of gas and brownish-yellow soot are generated. When the aging kettle is cooled and fails, the process is easy to generate temperature runaway spray and even explode as the traditional kettle type process, and has great danger. The problems of complex processing technology, high manufacturing cost and the like of the solid super acid loaded by the micro-channel reactor.

The applicant of application No. CN202011637985.1 has found that after the material A is mixed by concentrated nitric acid-ammonium sulfate-2-methylimidazole-concentrated sulfuric acid, the preparation process needs to be controlled at 0 ℃, refrigeration equipment is needed, and the equipment investment is increased. The mixed concentrated nitric acid-ammonium sulfate-2-methylimidazole-concentrated sulfuric acid has nitration reaction and serious danger, a mixture storage tank for storing the material A is equivalent to a traditional reaction kettle, a large amount of material A can react for a long time, and when the material A fails to be cooled, the material A storage tank can generate a large amount of gas, and the sprayed material even explodes.

Disclosure of Invention

The technical problem to be solved by the invention is to provide a 2-methyl-5 nitroimidazole continuous nitration process, which can realize the effects of low-temperature continuous reaction, stability, safety, high efficiency, high conversion rate, reduction of the dosage of nitric acid and the like in a 2-methyl-5 nitroimidazole nitration section.

The invention is realized by the following scheme: a2-methyl-5 nitroimidazole continuous nitration process comprises the following steps:

firstly, dissolving ammonium sulfate in fuming nitric acid to form a mixture A;

dissolving 2-methylimidazole in a concentrated sulfuric acid-acetic anhydride composite catalyst to form a mixture B;

step three, respectively feeding the mixture A and the mixture B into a multi-section micro-tube reactor for reaction through a mixture A steady flow delivery pump and a mixture B steady flow delivery pump in sequence;

and step four, continuously injecting water to stop the reaction after the reaction finished liquid flows out of the multi-section micro-tube reactor.

The mass fraction of fuming nitric acid in the first step is more than or equal to 98%, the mass ratio of fuming nitric acid to ammonium sulfate is 2.5-3.5, the mass fraction of concentrated sulfuric acid in the second step is more than or equal to 98%, and the mass ratio of concentrated sulfuric acid to 2-methylimidazole is 1.5-2.5; the mass ratio of the acetic anhydride to the 2-methylimidazole is 1.5-3.

And in the third step, the mixture A steady flow delivery pump and the mixture B steady flow delivery pump are three-pump-head diaphragm metering pumps with the phase difference of 120 degrees.

The mixture A and the mixture B are respectively injected into the mixer I by a mixture A steady flow delivery pump and a mixture B steady flow delivery pump and then sequentially enter the multi-section micro-tube reactor for reaction, the multi-section micro-tube reactor is formed by mutually connecting a plurality of micro-tube reactors in series, and the number of sections of the multi-section micro-tube reactor is more than or equal to 2.

The multistage micro-tube reactor consists of a first-stage reactor, a second-stage reactor, a third-stage reactor and a fourth-stage reactor, mixed liquid from the first mixer sequentially enters the first-stage reactor, the second-stage reactor, the third-stage reactor and the fourth-stage reactor, reaction completion liquid flowing out of the fourth-stage reactor enters a second mixer, meanwhile, continuous water injection and dilution are carried out on the reaction completion liquid through a water injection pump until the reaction is terminated, and the reaction liquid is neutralized, separated and dried after the reaction is terminated to obtain a finished product.

The micro-tube reactor is composed of a plurality of micro-tubes and a sleeve, the micro-tubes are arranged in the sleeve in parallel, the lower ends of the micro-tubes are connected with a distribution disc, the lower ends of the distribution disc are connected with a reaction liquid feeding hole, the upper ends of the micro-tubes are connected with a collection disc, the upper ends of the collection disc are connected with a reaction liquid discharging hole, the lower end of one side of the sleeve is connected with a circulating warm water inlet, and the upper end of the other side of the sleeve is connected with a circulating warm water outlet.

The number of the parallel microtube pipes in each microtube reactor is more than or equal to 10, the microtubes are made of 316 stainless steel, and the inner diameters of the microtubes are 0.5-6 mm.

The temperature of the circulating warm water is 40-60 ℃, the reaction temperature of materials in the micro-tube reactor is 40-70 ℃, the temperature of the mixture A is controlled to be 25-35 ℃, the temperature of the mixture B is controlled to be 25-45 ℃, the temperature of the mixture A is controlled not to exceed 50 ℃ in the preparation process, and the temperature of the mixture B is controlled not to exceed 100 ℃ in the preparation process.

The mass flow ratio of the mixture A to the mixture B is as follows: and 0.2-0.3, and sequentially feeding the mixture A and the mixture B into the multistage micro-tube reactor for reaction by a mixture A steady flow conveying pump and a mixture B steady flow conveying pump respectively, wherein the total reaction time is not less than 15 seconds.

And after the reaction finished liquid flows out of the multi-section micro-tube reactor, continuously injecting water to stop the reaction, wherein the volume of the injected water is more than or equal to the volume of the total reaction liquid.

The invention has the beneficial effects that:

1. according to the 2-methyl-5 nitroimidazole continuous nitration process, the mixture A (at 25-35 ℃) and the mixture B (at 25-45 ℃) are fed at normal temperature or slightly higher than the normal temperature without refrigeration equipment, so that the energy consumption is low, and due to the addition of acetic anhydride, the viscosity of the mixture B is greatly reduced at 25-45 ℃ and the conveying by a pump is facilitated;

2. the 2-methyl-5 nitroimidazole continuous nitration process adopts a 316 stainless steel micro-tube reactor, has simple structure, easy manufacture, no need of solid acid as a catalyst and less investment;

3. the AB two groups of mixed materials of the 2-methyl-5 nitroimidazole continuous nitration process have stable properties, and water is directly injected into the reaction liquid from the outlet of the micro-tube reactor to terminate the reaction, so that the process solves the safety risk caused by the continuous reaction of the reaction completion liquid in the aging kettle in the prior art; all reactants are mixed together and then enter the reactor for reaction, and the mixture reacts before entering the reactor, so that the safety risk is great;

4. the 2-methyl-5-nitroimidazole continuous nitration process adopts concentrated sulfuric acid and acetic anhydride as composite catalysts, adopts acetic anhydride as a mild nitration reaction catalyst, reduces the dosage of the concentrated sulfuric acid as a strong nitration reaction catalyst after adding the acetic anhydride, leads the reaction to be mild, does not generate gas and brown yellow smoke in the reaction process, has stable reaction process and leads the yield of the product 2-methyl-5-nitroimidazole to be more than 85 percent;

5. the 2-methyl-5 nitroimidazole continuous nitration process can realize the low-temperature 40-70 ℃ continuous reaction of the 2-methyl-5 nitroimidazole nitration section, is stable, safe and efficient, has high conversion rate of more than 85 percent, and can realize the industrialization of the 2-methyl-5 nitroimidazole nitration section.

Drawings

FIG. 1 is a schematic flow diagram of a continuous nitration process of 2-methyl-5 nitroimidazole according to the present invention.

FIG. 2 is a schematic diagram of the structure of a micro-tube reactor of the present invention.

In the figure: the device comprises a mixture A flow stabilizing and conveying pump 1, a mixture b flow stabilizing and conveying pump 2, a mixer I3, a first section reactor 4, a second section reactor 5, a third section reactor 6, a fourth section reactor 7, a mixer II 8, a water injection pump 9, a micro pipe 10, a sleeve pipe 11, a distribution disc 12, a reaction liquid feed port 13, a collection disc 14, a reaction liquid discharge port 15, a circulating warm water inlet 16, a circulating warm water inlet 17 and a circulating warm water outlet 18.

Detailed Description

The invention is further described below with reference to fig. 1-2, without limiting the scope of the invention.

In which like parts are designated by like reference numerals. It is noted that the terms "front", "back", "left", "right", "upper" and "lower" used in the following description refer to directions in the drawings, the terms "inner" and "outer" refer to directions toward and away from, respectively, the geometric center of a particular component, and the drawings are in greatly simplified form and employ non-precise ratios, merely for the purpose of facilitating and distinctly aiding in the description of the embodiments of the present invention.

In the following description, for purposes of clarity, not all features of an actual implementation are described, well-known functions or constructions are not described in detail since they would obscure the invention with unnecessary detail, it being understood that in the development of any actual embodiment, numerous implementation details must be set forth in order to achieve the developer's specific goals, such as compliance with system-related and business-related constraints, changing from one implementation to another, and it being recognized that such development effort might be complex and time consuming, but would nevertheless be a routine undertaking for those of ordinary skill in the art.

Example 1: a2-methyl-5 nitroimidazole continuous nitration process is carried out according to the following steps:

step 1, preparation of mixture A

Starting the mixture A stirring kettle, adding 900Kg of fuming nitric acid, opening a cooling water switch of the mixture A stirring kettle, slowly adding 330Kg of ammonium sulfate, controlling the temperature in the preparation process to be not more than 50 ℃, and cooling the material to 30 ℃ by normal temperature water after the preparation is finished.

Step 2, preparing mixture B

And starting the stirring kettle of the mixture B, adding 2000Kg of 98% concentrated sulfuric acid, opening a cooling water switch of the stirring kettle of the mixture B, slowly adding 1000Kg of 2-methylimidazole, controlling the temperature to be not more than 100 ℃, and adding 2000Kg of acetic anhydride after the 2-methylimidazole is added. Stirring uniformly, and cooling to 30 ℃.

Step three, the mixture A and the mixture B enter a micro-tube reactor for reaction

Starting warm water circulation to preheat a four-section micro-tube reactor (a first reactor 4, a second reactor 5, a third reactor 6 and a fourth reactor 7) at 50 ℃, starting a reaction stopping water injection pump 9 in advance to set the flow rate to be 12000g/min, and stabilizing; starting the mixture A steady flow conveying metering pump 1, setting the flow rate to be 2070g/min, and after the pump A runs stably; and finally, starting the mixture B steady flow conveying metering pump 2, setting the flow rate to be 8070g/min, injecting the mixture A and the mixture B into the mixer I3 through the mixture A steady flow conveying metering pump 1 and the mixture B steady flow conveying pump 2 respectively, and then sequentially entering the multistage microtube reactor for reaction.

Step four, terminating the reaction

And the reaction finished liquid flowing out of the four-section reactor 7 enters a second mixer 8, meanwhile, a water injection pump 9 is used for continuously injecting water to dilute the reaction finished liquid until the reaction is finished, the mixture after the reaction is finished flows into a neutralization kettle for neutralization, a centrifugal machine is used for solid-liquid separation after the neutralization is finished, the solid phase is washed and dried after the separation to obtain a finished product, the yield is 87%, and the purity is more than 99%.

Example 2: a2-methyl-5 nitroimidazole continuous nitration process is carried out according to the following steps:

step 1, preparation of mixture A

Starting the mixture A stirring kettle, adding 1000Kg of fuming nitric acid, opening a cooling water switch of the mixture A stirring kettle, slowly adding 250Kg of ammonium sulfate, controlling the temperature not to exceed 50 ℃ in the preparation process, and cooling the material to 25 ℃ by normal temperature water after the preparation is finished.

Step 2, preparing mixture B

And starting the stirring kettle of the mixture B, adding 1500Kg of 98% concentrated sulfuric acid, opening a cooling water switch of the stirring kettle of the mixture B, slowly adding 1000Kg of 2-methylimidazole, controlling the temperature to be not more than 100 ℃, and adding 1500Kg of acetic anhydride after the 2-methylimidazole is added. Stirring uniformly, and cooling to 25 ℃.

Step three, the mixture A and the mixture B enter a micro-tube reactor for reaction

Starting warm water circulation to preheat a four-section micro-tube reactor (a first reactor 4, a second reactor 5, a third reactor 6 and a fourth reactor 7) at 40 ℃, starting a reaction stopping water injection pump 9 in advance to set the flow at 12000g/min, and stabilizing; starting the mixture A steady flow conveying metering pump 1, setting the flow rate to be 2070g/min, and after the pump A runs stably; and finally, starting the mixture B steady flow conveying metering pump 2, setting the flow rate to be 8070g/min, injecting the mixture A and the mixture B into the mixer I3 through the mixture A steady flow conveying metering pump 1 and the mixture B steady flow conveying pump 2 respectively, and then sequentially entering the multistage microtube reactor for reaction.

Step four, terminating the reaction

And the reaction finished liquid flowing out of the four-section reactor 7 enters a second mixer 8, meanwhile, a water injection pump 9 is used for continuously injecting water to dilute the reaction finished liquid until the reaction is finished, the mixture after the reaction is finished flows into a neutralization kettle for neutralization, a centrifugal machine is used for solid-liquid separation after the neutralization is finished, the solid phase is washed and dried after the separation to obtain a finished product, the yield is 87%, and the purity is more than 99%.

Example 3: a2-methyl-5 nitroimidazole continuous nitration process is carried out according to the following steps:

step 1, preparation of mixture A

Starting the A mixture stirring kettle, adding 1050Kg of fuming nitric acid, opening a cooling water switch of the A mixture stirring kettle, slowly adding 300Kg of ammonium sulfate, controlling the temperature not to exceed 50 ℃ in the preparation process, and cooling the material to 35 ℃ by normal temperature water after the preparation is finished.

Step 2, preparing mixture B

And opening the stirring kettle of the mixture B, adding 2500Kg of 98% concentrated sulfuric acid, opening a cooling water switch of the stirring kettle of the mixture B, slowly adding 1000Kg of 2-methylimidazole, controlling the temperature to be less than 100 ℃, and adding 3000Kg of acetic anhydride after the 2-methylimidazole is added. Stirring uniformly, and cooling to 45 ℃.

Step three, the mixture A and the mixture B enter a micro-tube reactor for reaction

Starting warm water circulation to preheat a four-section micro-tube reactor (a first reactor 4, a second reactor 5, a third reactor 6 and a fourth reactor 7) at 60 ℃, starting a reaction stopping water injection pump 9 in advance to set the flow at 12000g/min, and stabilizing; starting the mixture A steady flow conveying metering pump 1, setting the flow rate to be 2070g/min, and after the pump A runs stably; and finally, starting the mixture B steady flow conveying metering pump 2, setting the flow rate to be 8070g/min, injecting the mixture A and the mixture B into the mixer I3 through the mixture A steady flow conveying metering pump 1 and the mixture B steady flow conveying pump 2 respectively, and then sequentially entering the multistage microtube reactor for reaction.

Step four, terminating the reaction

And the reaction finished liquid flowing out of the four-section reactor 7 enters a second mixer 8, meanwhile, a water injection pump 9 is used for continuously injecting water to dilute the reaction finished liquid until the reaction is finished, the mixture after the reaction is finished flows into a neutralization kettle for neutralization, a centrifugal machine is used for solid-liquid separation after the neutralization is finished, the solid phase is washed and dried after the separation to obtain a finished product, the yield is 87%, and the purity is more than 99%.

Although the invention has been described and illustrated in some detail, it should be understood that various modifications may be made to the described embodiments or equivalents may be substituted, as will be apparent to those skilled in the art, without departing from the spirit of the invention.