CN115160188A - Method for preparing nitroguanidine in micro-channel - Google Patents
Method for preparing nitroguanidine in micro-channel Download PDFInfo
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- CN115160188A CN115160188A CN202210787780.3A CN202210787780A CN115160188A CN 115160188 A CN115160188 A CN 115160188A CN 202210787780 A CN202210787780 A CN 202210787780A CN 115160188 A CN115160188 A CN 115160188A
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- sulfuric acid
- nitroguanidine
- guanidine nitrate
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- IDCPFAYURAQKDZ-UHFFFAOYSA-N 1-nitroguanidine Chemical compound NC(=N)N[N+]([O-])=O IDCPFAYURAQKDZ-UHFFFAOYSA-N 0.000 title claims abstract description 86
- 238000000034 method Methods 0.000 title claims abstract description 63
- QAOWNCQODCNURD-UHFFFAOYSA-N sulfuric acid Substances OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims abstract description 156
- 239000000463 material Substances 0.000 claims abstract description 102
- NDEMNVPZDAFUKN-UHFFFAOYSA-N guanidine;nitric acid Chemical compound NC(N)=N.O[N+]([O-])=O.O[N+]([O-])=O NDEMNVPZDAFUKN-UHFFFAOYSA-N 0.000 claims abstract description 74
- 239000007788 liquid Substances 0.000 claims abstract description 55
- 239000002253 acid Substances 0.000 claims abstract description 49
- 238000004519 manufacturing process Methods 0.000 claims abstract description 14
- 238000000926 separation method Methods 0.000 claims abstract description 9
- 238000001914 filtration Methods 0.000 claims abstract description 8
- 238000006243 chemical reaction Methods 0.000 claims description 22
- 238000002425 crystallisation Methods 0.000 claims description 11
- 230000008025 crystallization Effects 0.000 claims description 11
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 10
- 238000004090 dissolution Methods 0.000 claims description 5
- 230000035484 reaction time Effects 0.000 claims description 2
- 238000007599 discharging Methods 0.000 description 12
- 239000000243 solution Substances 0.000 description 12
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 8
- 229910017604 nitric acid Inorganic materials 0.000 description 8
- 239000002904 solvent Substances 0.000 description 8
- 238000002360 preparation method Methods 0.000 description 6
- 238000003756 stirring Methods 0.000 description 6
- 238000004064 recycling Methods 0.000 description 4
- 238000005119 centrifugation Methods 0.000 description 3
- 239000002360 explosive Substances 0.000 description 3
- 239000002994 raw material Substances 0.000 description 3
- 230000002194 synthesizing effect Effects 0.000 description 3
- 239000007864 aqueous solution Substances 0.000 description 2
- 238000010009 beating Methods 0.000 description 2
- 239000013078 crystal Substances 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 238000004321 preservation Methods 0.000 description 2
- 238000004886 process control Methods 0.000 description 2
- 239000003380 propellant Substances 0.000 description 2
- 230000035945 sensitivity Effects 0.000 description 2
- 238000009210 therapy by ultrasound Methods 0.000 description 2
- WCXDHFDTOYPNIE-RIYZIHGNSA-N (E)-acetamiprid Chemical compound N#C/N=C(\C)N(C)CC1=CC=C(Cl)N=C1 WCXDHFDTOYPNIE-RIYZIHGNSA-N 0.000 description 1
- 239000005875 Acetamiprid Substances 0.000 description 1
- 235000015842 Hesperis Nutrition 0.000 description 1
- 235000012633 Iberis amara Nutrition 0.000 description 1
- 239000005906 Imidacloprid Substances 0.000 description 1
- 238000010306 acid treatment Methods 0.000 description 1
- 239000000654 additive Substances 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 238000005474 detonation Methods 0.000 description 1
- 239000003344 environmental pollutant Substances 0.000 description 1
- 238000003912 environmental pollution Methods 0.000 description 1
- 238000004880 explosion Methods 0.000 description 1
- YWTYJOPNNQFBPC-UHFFFAOYSA-N imidacloprid Chemical compound [O-][N+](=O)\N=C1/NCCN1CC1=CC=C(Cl)N=C1 YWTYJOPNNQFBPC-UHFFFAOYSA-N 0.000 description 1
- 229940056881 imidacloprid Drugs 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000006396 nitration reaction Methods 0.000 description 1
- 231100000719 pollutant Toxicity 0.000 description 1
- 239000002002 slurry Substances 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 238000003860 storage Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 238000003786 synthesis reaction Methods 0.000 description 1
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C277/00—Preparation of guanidine or its derivatives, i.e. compounds containing the group, the singly-bound nitrogen atoms not being part of nitro or nitroso groups
- C07C277/08—Preparation of guanidine or its derivatives, i.e. compounds containing the group, the singly-bound nitrogen atoms not being part of nitro or nitroso groups of substituted guanidines
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
Abstract
The invention discloses a method for preparing nitroguanidine in a microchannel. The method comprises the following steps: s1, adding concentrated sulfuric acid and guanidine nitrate into a feeding kettle to obtain a mixed material, wherein the weight ratio of the concentrated sulfuric acid to the guanidine nitrate is as follows: 1.5-3:1; s2, feeding the mixed material into a dissolving kettle to obtain a dissolved material; s3, filtering the dissolved material to obtain guanidine nitrate acid solution, and feeding 20-25% of guanidine nitrate acid solution into the feeding kettle; s4, feeding the guanidine nitrate acid solution left in the step S3 into a microchannel reactor to obtain a reacted material; s5, after the reacted materials are continuously crystallized, carrying out centrifugal separation treatment on the obtained feed liquid to obtain nitroguanidine and dilute sulfuric acid, and concentrating the dilute sulfuric acid and then feeding the concentrated dilute sulfuric acid into the feeding kettle. The method can reduce the input of concentrated sulfuric acid, reduce the production cost and solve the problem of treatment of dilute sulfuric acid.
Description
Technical Field
The invention belongs to the technical field of chemical industry, and particularly relates to a method for preparing nitroguanidine in a microchannel.
Background
Nitroguanidine is an important industrial raw material, is an intermediate for synthesizing imidacloprid and acetamiprid, and is also a raw material for synthesizing an intermediate N-nitroiminoimidazolidine in the next step. Nitroguanidine has low detonation temperature and low sensitivity, and can be used as a propellant and a bullet charging component of rockets, missiles, explosives and the like. Therefore, the nitroguanidine has excellent comprehensive performance, not only can be used as explosive and other explosive products, but also can be used as energetic additives such as low-characteristic signal propellant based on the characteristics of moderate energy, low sensitivity and the like.
At present, two methods for producing nitroguanidine at home and abroad mainly comprise a sulfuric acid method and a nitric acid method. The sulfuric acid method is characterized in that guanidine nitrate is added into concentrated sulfuric acid, and a product is obtained through heat preservation, elutriation, crystallization and centrifugation, wherein the method for producing nitroguanidine has the advantages of long cycle, long storage time of nitroguanidine slurry in a reaction kettle, certain explosion risk, low production continuity degree, capability of generating a large amount of dilute sulfuric acid, difficulty in recycling and high treatment cost; the nitric acid method is to add guanidine nitrate into concentrated nitric acid, and obtain a nitroguanidine product through heat preservation, elutriation, crystallization and centrifugation, and the method can generate a large amount of acid gas in the production process, thereby causing serious harm to the environment and workers in a workshop, and dilute nitric acid generated by the nitric acid method is more difficult to treat.
CN103193682B discloses a method for preparing nitroguanidine by acidifying and dehydrating guanidine nitrate in a continuous flow microchannel reactor, which belongs to the technical field of organic synthesis application and is a new process for synthesizing nitroguanidine in a reaction time of dozens of seconds to several minutes by taking guanidine nitrate aqueous solution and concentrated sulfuric acid as raw materials in the continuous flow microchannel reactor. The method has the advantages of simple and safe operation, capability of continuously producing the nitroguanidine with high yield and small environmental pollution. The product yield of the invention is 80-85%, and the melting point is 230-232 ℃. Although the method increases the continuity of production, the guanidine nitrate aqueous solution and the concentrated sulfuric acid used in the method are reacted in a micro-channel, and the production efficiency is not high.
CN110204461A discloses a nitroguanidine crystal and a nitroguanidine microchannel crystallization process and device, wherein water, concentrated nitric acid and guanidine nitrate are reacted to obtain nitroguanidine acid solution, the nitroguanidine acid solution is respectively continuously input into a microchannel crystallizer for crystallization, ultrasonic treatment is carried out in the crystallization process, and a crystallized product is separated, cleaned and dried to obtain a high-purity spherical nitroguanidine crystal; wherein, the mass fraction of nitroguanidine in the nitroguanidine acid solution is 25-50%, the input flow rate of the nitroguanidine acid solution is 100-300 mL/min, the input flow rate of water is 150-400 mL/min, and the ultrasonic power of ultrasonic treatment is 1000-1800W. The method has the characteristics of continuous operation, simple and controllable reaction conditions, high reaction safety and the like, and can be directly applied to actual production. However, the dilute nitric acid generated by the method is difficult to treat, and the production cost is higher than that of a sulfuric acid method.
So far, no technical scheme for reducing the consumption of sulfuric acid by combining microchannel reaction and dilute acid concentration is found.
Disclosure of Invention
In view of the above problems in the prior art, the present invention aims to provide a method for continuously producing nitroguanidine by using a microchannel reactor, which can effectively reduce the consumption of sulfuric acid and solve the problem of dilute sulfuric acid treatment by controlling the specific feeding ratio of materials, the conditions of different reaction processes and the recycling of materials.
In order to solve the technical problems, the invention provides the following technical scheme:
in one aspect, the invention provides a method for preparing nitroguanidine in a microchannel, comprising the following steps:
s1, adding concentrated sulfuric acid and guanidine nitrate into a feeding kettle to obtain a mixed material, wherein the concentrated sulfuric acid and the guanidine nitrate are in the following weight ratio: 1.5-3:1;
s2, feeding the mixed material into a dissolving kettle to obtain a dissolved material;
s3, filtering the dissolved material to obtain guanidine nitrate acid solution, and feeding 20-25% of guanidine nitrate acid solution into the feeding kettle;
s4, feeding the guanidine nitrate acid solution left in the step S3 into a microchannel reactor to obtain a reacted material;
s5, after the reacted materials are continuously crystallized, carrying out centrifugal separation treatment on the obtained feed liquid to obtain nitroguanidine and dilute sulfuric acid, and concentrating the dilute sulfuric acid and then feeding the concentrated dilute sulfuric acid into the feeding kettle.
The method for preparing nitroguanidine in the microchannel has the advantages of high degree of continuity and accurate process control in the treatment process from feeding to centrifuging, partial unreacted sulfuric acid is continuously refluxed into the reaction kettle before guanidine nitrate acid solution enters the microchannel, and the refluxed sulfuric acid has the function of keeping the amount of the solvent while providing heat, so that the guanidine nitrate can be promoted to be dissolved and dehydrated. Further, the dilute sulfuric acid after centrifugation is concentrated and then continuously recycled to the feeding kettle. The method of the invention only has little loss of a part of sulfuric acid, and the amount of the sulfuric acid supplemented to the feeding kettle can be greatly reduced, thereby reducing the consumption of the sulfuric acid and solving the problem of difficult treatment of dilute sulfuric acid.
In some embodiments, the weight ratio of the concentrated sulfuric acid to the guanidine nitrate is: 2-2.5. In some preferred embodiments, the weight ratio of the concentrated sulfuric acid to the guanidine nitrate is: 2:1.
In some embodiments, in step S1, the concentrated sulfuric acid has a concentration of 88% to 92%, and the concentrated sulfuric acid in this concentration range can dissolve guanidine nitrate but does not undergo a nitration reaction with guanidine nitrate. In some preferred embodiments, the concentrated sulfuric acid has a concentration of 90%.
In some embodiments, in step S1, the temperature of the feeding kettle is controlled to be 20 to 25 ℃.
In some embodiments, in step S1, the feeding speed of the concentrated sulfuric acid and guanidine nitrate and the material-beating speed of the material-beating pump are controlled, so that the liquid level of the concentrated sulfuric acid and guanidine nitrate added into the feeding kettle is controlled to be 30% to 70% of the volume of the reaction kettle.
In some embodiments, in step S2, the dissolution temperature in the dissolution kettle is controlled to be 25 to 40 ℃, which can promote rapid dissolution of guanidine nitrate and ensure safety of the production process. Meanwhile, through the dissolving process in the dissolving kettle, the concentration of concentrated sulfuric acid in the dissolved material can reach 98 percent, and the concentrated sulfuric acid is further used for reacting with guanidine nitrate in a microchannel reactor to generate nitroguanidine.
In some embodiments, in step S3, the process of filtering the dissolved material is performed in a clarifying kettle, and a filter screen is disposed in the clarifying kettle and is used for filtering the dissolved material to prevent solid guanidine nitrate which is not completely dissolved from entering the microchannel reactor to cause blockage.
In some embodiments, in step S4, the reaction temperature in the microchannel reactor is controlled to be constant at any temperature value between 55 ℃ and 60 ℃, so as to ensure that the guanidine nitrate acid solution can completely react. Moreover, the reaction materials in the reactor can be heated uniformly by adopting the microchannel reactor, and the reaction process is more thorough.
In some embodiments, in step S5, the reaction conditions for continuously crystallizing the reacted material comprise: the temperature is 13-15 ℃, and the crystallization time is 3-10 h.
In some embodiments, the concentration of the dilute sulfuric acid obtained in step S5 is 20% to 25%.
In another aspect, the present invention provides a system for preparing nitroguanidine, the system being used for carrying out the above method for preparing nitroguanidine, the system comprising a feeding kettle, a dissolving kettle, a clarifying kettle, a microchannel reactor, a continuous crystallizer, a centrifuge, a concentration device;
the feeding kettle is used for receiving concentrated sulfuric acid and guanidine nitrate to obtain a mixed material;
the dissolving kettle is used for receiving the mixed material fed by the feeding kettle to obtain a dissolved material;
the clarifying kettle is used for filtering the dissolved material fed from the dissolving kettle to obtain guanidine nitrate acid liquid, and the clarifying kettle is connected with the feeding kettle and is used for feeding the guanidine nitrate acid liquid into the feeding kettle;
the microchannel reactor is used for receiving guanidine nitrate acid solution fed from the clarifying kettle to obtain a reacted material;
the continuous crystallizer is used for receiving the reacted material fed by the microchannel reactor to obtain a crystallization feed liquid;
the centrifugal machine is used for receiving the crystallization feed liquid fed by the continuous crystallizer to obtain nitroguanidine and dilute sulfuric acid;
the concentration device is used for receiving dilute sulfuric acid fed by the centrifuge and feeding concentrated sulfuric acid obtained after concentration into the feeding kettle.
In still another aspect, the present invention provides nitroguanidine obtained by the above method for preparing nitroguanidine, wherein the purity of the nitroguanidine is more than 99%, and the weight ratio of water in the nitroguanidine is 20-25% based on the total weight of the nitroguanidine.
The technical scheme provided by the invention at least has the following beneficial effects:
the method for preparing nitroguanidine in the microchannel has the advantages of high degree of continuity and accurate process control in the treatment process from feeding to centrifuging, part of unreacted sulfuric acid is continuously refluxed into the reaction kettle before guanidine nitrate acid solution enters the microchannel, the refluxed sulfuric acid plays a role in keeping the amount of a solvent while providing heat, and the centrifuged dilute sulfuric acid is concentrated and then continuously recycled into the feeding kettle.
The nitroguanidine obtained by the method for preparing nitroguanidine in the microchannel has high yield, the product purity can reach more than 90 percent, even more than 97 percent, and the product quality meets the industrial standard of industrial nitroguanidine. And each batch of feeding can reduce the feeding of more than 90 percent of new concentrated sulfuric acid, thereby greatly reducing the treatment pressure of the dilute acid while reducing the production cost.
Drawings
FIG. 1 is a schematic diagram of a system for preparing nitroguanidine according to an embodiment of the present invention.
FIG. 2 is a schematic flow chart of a method for preparing nitroguanidine according to an embodiment of the present invention.
Detailed Description
In order to make the technical problems, technical solutions and advantages to be solved by the present invention clearer, the following detailed description is given with reference to specific embodiments. It is to be understood that the embodiments described below are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The reagents and conventional laboratory equipment used in the present examples are commercially available unless otherwise specified.
Example 1
As shown in fig. 1, a schematic diagram of a system for preparing nitroguanidine provided in this embodiment, and fig. 2 is a schematic flow chart of a process for preparing nitroguanidine performed in the system shown in fig. 1, comprising the following steps:
s1, adding concentrated sulfuric acid and guanidine nitrate into a feeding kettle and stirring, wherein the temperature in the feeding kettle is 25 ℃, and the weight ratio of the concentrated sulfuric acid to the guanidine nitrate is 2: and 1, controlling the feeding speed, and opening a material transferring pump of the feeding kettle when the liquid level in the reaction kettle reaches 50% of the volume of the feeding kettle, so as to transfer the mixed material in the feeding kettle to the dissolving kettle.
S2, controlling the temperature in the dissolving kettle to be constant at 30 ℃, dissolving the mixed material, and opening a material transferring pump of the dissolving kettle when the liquid level of the mixed material reaches 50% of the volume of the dissolving kettle, and transferring the dissolved material to a clarifying kettle.
And S3, when the liquid level of the feed liquid in the clarifying kettle reaches 50%, opening a circulating pump and a discharging valve of the clarifying kettle for circulating and discharging, circulating 25% of guanidine nitrate acid liquid in the clarifying kettle to the feeding kettle, and transferring the rest guanidine nitrate acid liquid to the microchannel reactor through a material transferring pump.
S3, controlling the temperature in the microchannel reactor to be 55 ℃ constant, reacting the materials at the temperature for 60S, sending the reacted materials into a continuous crystallizer, adding process water, crystallizing at the temperature of 14 ℃ for 8h, sending crystallized feed liquid into a centrifugal machine for centrifugal separation to obtain a wet nitroguanidine product and dilute sulfuric acid, transferring the dilute sulfuric acid to a dilute acid concentration workshop for concentration through a material transfer pump, and continuously using concentrated sulfuric acid after concentration as a solvent of guanidine nitrate.
The yield of the nitroguanidine product obtained in the embodiment is 90.2%, and the product quality meets the industrial standard of industrial nitroguanidine.
Example 2
The preparation process of nitroguanidine in this example includes the following steps:
s1, adding concentrated sulfuric acid and guanidine nitrate into a feeding kettle and stirring, wherein the temperature in the feeding kettle is 25 ℃, and the weight ratio of the concentrated sulfuric acid to the guanidine nitrate is 2:1, concentrated sulfuric acid in the process is concentrated acid obtained in the subsequent process, only concentrated sulfuric acid with the weight ratio of 6% is supplemented new sulfuric acid, the feeding speed is controlled, when the liquid level in the reaction kettle reaches 50% of the volume of the feeding kettle, a material transferring pump of the feeding kettle is opened, and mixed materials in the feeding kettle are transferred to the dissolving kettle.
S2, controlling the temperature in the dissolving kettle to be constant at 30 ℃, dissolving the mixed material, and opening a material transferring pump of the dissolving kettle when the liquid level of the mixed material reaches 50% of the volume of the dissolving kettle, and transferring the dissolved material to a clarifying kettle.
And S3, when the liquid level of the feed liquid in the clarifying kettle reaches 50%, opening a circulating pump and a discharging valve of the clarifying kettle for circulating and discharging, circulating 25% of guanidine nitrate acid liquid in the clarifying kettle to the feeding kettle, and transferring the rest guanidine nitrate acid liquid to the microchannel reactor through a material transferring pump.
S3, controlling the temperature in the microchannel reactor to be 55 ℃ and keeping constant temperature, after materials react for 60S at the temperature, sending the reacted materials into a continuous crystallizer, adding process water, crystallizing for 8h at the temperature of 14 ℃, sending crystallized material liquid into a centrifugal machine for centrifugal separation to obtain wet nitroguanidine and dilute sulfuric acid, transferring the dilute sulfuric acid to a dilute acid concentration workshop through a material transfer pump for concentration, and circularly recycling 95% concentrated sulfuric acid into a feeding kettle to be used as a solvent of guanidine nitrate.
The yield of the nitroguanidine product obtained in the embodiment is 96.7%, and the product quality meets the industrial standard of industrial nitroguanidine.
Example 3
The preparation process of nitroguanidine in this example includes the following steps:
s1, adding concentrated sulfuric acid and guanidine nitrate into a feeding kettle and stirring, wherein the temperature in the feeding kettle is 25 ℃, and the weight ratio of the concentrated sulfuric acid to the guanidine nitrate is 2:1, concentrated sulfuric acid in the process is concentrated acid obtained in the subsequent process, only concentrated sulfuric acid with the weight ratio of 6% is supplemented new sulfuric acid, the feeding speed is controlled, when the liquid level in the reaction kettle reaches 50% of the volume of the feeding kettle, a material transferring pump of the feeding kettle is opened, and mixed materials in the feeding kettle are transferred to the dissolving kettle.
S2, controlling the temperature in the dissolving kettle to be constant at 25 ℃, dissolving the mixed material, and opening a material transferring pump of the dissolving kettle when the liquid level of the mixed material reaches 50% of the volume of the dissolving kettle, and transferring the dissolved material to a clarifying kettle.
And S3, when the liquid level of the feed liquid in the clarifying kettle reaches 50%, opening a circulating pump and a discharging valve of the clarifying kettle for circulating and discharging, circulating 25% of guanidine nitrate acid liquid in the clarifying kettle to the feeding kettle, and transferring the rest guanidine nitrate acid liquid to the microchannel reactor through a material transferring pump.
S3, controlling the temperature in the microchannel reactor to be 57 ℃ constant, after materials react for 60S at the temperature, sending the reacted materials into a continuous crystallizer, adding process water, crystallizing for 8h at the temperature of 14 ℃, sending the crystallized material liquid into a centrifugal machine for centrifugal separation to obtain wet nitroguanidine and dilute sulfuric acid, transferring the dilute sulfuric acid to a dilute acid concentration workshop through a material transfer pump for concentration, recycling 95% concentrated sulfuric acid obtained by concentration into a feeding kettle to be used as a solvent of guanidine nitrate
The yield of the nitroguanidine product obtained in the embodiment is 95.3%, and the product quality meets the industrial standard of industrial nitroguanidine.
Example 4
The preparation process of nitroguanidine in this example includes the following steps:
s1, adding concentrated sulfuric acid and guanidine nitrate into a feeding kettle and stirring, wherein the temperature in the feeding kettle is 25 ℃, and the weight ratio of the concentrated sulfuric acid to the guanidine nitrate is 2:1, concentrated sulfuric acid in the process is concentrated acid obtained in the subsequent process, only concentrated sulfuric acid with the weight ratio of 6% is supplemented new sulfuric acid, the feeding speed is controlled, when the liquid level in the reaction kettle reaches 50% of the volume of the feeding kettle, a material transferring pump of the feeding kettle is opened, and mixed materials in the feeding kettle are transferred to the dissolving kettle.
S2, controlling the temperature in the dissolving kettle to be constant at 40 ℃, dissolving the mixed material, and opening a material transferring pump of the dissolving kettle when the liquid level of the mixed material reaches 50% of the volume of the dissolving kettle, and transferring the dissolved material to a clarifying kettle.
And S3, when the liquid level of the feed liquid in the clarifying kettle reaches 50%, opening a circulating pump and a discharging valve of the clarifying kettle for circulation and discharging, circulating 25% of guanidine nitrate acid liquid in the clarifying kettle to the feeding kettle, and transferring the rest guanidine nitrate acid liquid to the microchannel reactor through a material transferring pump.
S3, controlling the temperature in the microchannel reactor to be constant at 60 ℃, reacting the materials at the temperature for 60S, feeding the reacted materials into a continuous crystallizer, adding process water, crystallizing at the temperature of 14 ℃ for 8h, feeding crystallized feed liquid into a centrifugal machine for centrifugal separation to obtain a wet nitroguanidine product and dilute sulfuric acid, transferring the dilute sulfuric acid to a dilute acid concentration workshop for concentration through a material transfer pump, and concentrating to obtain 95% concentrated sulfuric acid which is recycled to a feeding kettle and used as a solvent of guanidine nitrate.
The yield of the nitroguanidine product obtained in the embodiment is 97.3%, and the product quality meets the industrial standard of industrial nitroguanidine.
Example 5
The preparation process of nitroguanidine in this example includes the following steps:
s1, adding concentrated sulfuric acid and guanidine nitrate into a feeding kettle, and stirring, wherein the temperature in the feeding kettle is 25 ℃, and the weight ratio of the concentrated sulfuric acid to the guanidine nitrate is 2.2: and 1, concentrated sulfuric acid in the process is concentrated acid obtained in subsequent procedures, only concentrated sulfuric acid with the weight ratio of 5% is supplemented new sulfuric acid, the feeding speed is controlled, when the liquid level in the reaction kettle reaches 50% of the volume of the feeding kettle, a material transferring pump of the feeding kettle is opened, and mixed materials in the feeding kettle are transferred into the dissolving kettle.
S2, controlling the temperature in the dissolving kettle to be constant at 30 ℃, dissolving the mixed material, and opening a material transferring pump of the dissolving kettle when the liquid level of the mixed material reaches 50% of the volume of the dissolving kettle, and transferring the dissolved material to a clarifying kettle.
And S3, when the liquid level of the feed liquid in the clarifying kettle reaches 50%, opening a circulating pump and a discharging valve of the clarifying kettle for circulating and discharging, circulating 24% of guanidine nitrate acid liquid in the clarifying kettle to the feeding kettle, and transferring the rest guanidine nitrate acid liquid to the microchannel reactor through a material transferring pump.
S3, controlling the temperature in the microchannel reactor to be at a constant temperature of 58 ℃, after materials react for 40S at the temperature, sending the reacted materials into a continuous crystallizer, adding process water, crystallizing for 8h at the temperature of 14 ℃, sending crystallized feed liquid into a centrifugal machine for centrifugal separation to obtain a wet nitroguanidine product and dilute sulfuric acid, transferring the dilute sulfuric acid to a dilute acid concentration workshop for concentration through a material transfer pump, and concentrating to obtain 95% concentrated sulfuric acid which is recycled to a feeding kettle to be used as a solvent of guanidine nitrate.
The yield of the nitroguanidine product obtained in the embodiment is 95.4%, and the product quality meets the industrial standard of industrial nitroguanidine.
Example 6
The preparation process of nitroguanidine in this example includes the following steps:
s1, adding concentrated sulfuric acid and guanidine nitrate into a feeding kettle, and stirring, wherein the temperature in the feeding kettle is 25 ℃, and the weight ratio of the concentrated sulfuric acid to the guanidine nitrate is 1.8:1, concentrated sulfuric acid in the process is concentrated acid obtained in the subsequent process, only 8% of concentrated sulfuric acid in weight ratio is supplemented new sulfuric acid, the feeding speed is controlled, when the liquid level in the reaction kettle reaches 50% of the volume of the feeding kettle, a material transferring pump of the feeding kettle is opened, and mixed materials in the feeding kettle are transferred to the dissolving kettle.
S2, controlling the temperature in the dissolving kettle to be constant at 35 ℃, dissolving the mixed material, opening a material transferring pump of the dissolving kettle when the liquid level of the mixed material reaches 50% of the volume of the dissolving kettle, and transferring the dissolved material to a clarifying kettle.
And S3, when the liquid level of the feed liquid in the clarifying kettle reaches 50%, opening a circulating pump and a discharging valve of the clarifying kettle for circulating and discharging, circulating 23% of guanidine nitrate acid liquid in the clarifying kettle to the feeding kettle, and transferring the rest guanidine nitrate acid liquid to the microchannel reactor through a material transferring pump.
S3, controlling the temperature in the microchannel reactor to be constant at 60 ℃, reacting the materials at the temperature for 120S, feeding the reacted materials into a continuous crystallizer, adding process water, crystallizing at the temperature of 14 ℃ for 8h, feeding crystallized feed liquid into a centrifugal machine for centrifugal separation to obtain a wet nitroguanidine product and dilute sulfuric acid, transferring the dilute sulfuric acid to a dilute acid concentration workshop for concentration through a material transfer pump, and concentrating to obtain 95% concentrated sulfuric acid which is recycled to a feeding kettle and used as a solvent of guanidine nitrate.
The yield of the nitroguanidine product obtained in the embodiment is 95.6%, and the product quality meets the industrial standard of industrial nitroguanidine.
The embodiments show that the preparation method of nitroguanidine can improve the yield of nitroguanidine by more than 96%, the input of new concentrated sulfuric acid can be reduced by more than 90% for each batch of materials, the production cost is reduced, the treatment pressure of dilute acid is greatly reduced, and compared with a nitric acid method production process in the prior art, the method provided by the invention does not generate secondary pollutants after concentration treatment of sulfuric acid.
While the foregoing is directed to the preferred embodiment of the present invention, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the appended claims.
Claims (10)
1. A method for preparing nitroguanidine in a microchannel is characterized by comprising the following steps:
s1, adding concentrated sulfuric acid and guanidine nitrate into a feeding kettle to obtain a mixed material, wherein the concentrated sulfuric acid and the guanidine nitrate are in the following weight ratio: 1.5-3:1;
s2, feeding the mixed material into a dissolving kettle to obtain a dissolved material;
s3, filtering the dissolved material to obtain guanidine nitrate acid solution, and feeding 20-25% of guanidine nitrate acid solution into the feeding kettle;
s4, feeding the guanidine nitrate acid solution left in the step S3 into a microchannel reactor to obtain a reacted material;
s5, after the reacted materials are continuously crystallized, carrying out centrifugal separation treatment on the obtained feed liquid to obtain nitroguanidine and dilute sulfuric acid, and concentrating the dilute sulfuric acid and then feeding the concentrated dilute sulfuric acid into the feeding kettle.
2. The method for preparing nitroguanidine according to claim 1, wherein in step S1, the weight ratio of the concentrated sulfuric acid to the guanidine nitrate is: 2-2.5, and/or the concentrated sulfuric acid has a concentration of 88% -92%.
3. The method for preparing nitroguanidine according to claim 1 or 2, wherein in step S1, the temperature of the feeding kettle is controlled to be 20-25 ℃.
4. The method for preparing nitroguanidine according to any one of claims 1 to 3, wherein the liquid level of the concentrated sulfuric acid and the guanidine nitrate added into the feeding kettle is controlled to be 30 to 70 percent of the volume of the reaction kettle.
5. The method for producing nitroguanidine according to any one of claims 1 to 4, wherein in step S2, the dissolution temperature in the dissolution tank is controlled to be 25 to 40 ℃.
6. The method for preparing nitroguanidine according to any one of claims 1 to 5, wherein the step S3 is performed in a clarifying tank, and a filter screen is arranged in the clarifying tank for filtering the dissolved material.
7. The method for preparing nitroguanidine according to any one of claims 1 to 6, wherein in step S4, the reaction temperature in the microchannel reactor is controlled to be constant at any temperature value between 55 and 60 ℃, and/or the reaction time in the microchannel reactor is controlled to be between 40S and 160S.
8. The method for preparing nitroguanidine according to any one of claims 1 to 7, wherein the reaction conditions for continuously crystallizing the reaction material in step S5 comprise: the temperature is 13-15 ℃, and the crystallization time is 3-10 h.
9. A system for preparing nitroguanidine, wherein the system is used for carrying out the method for preparing nitroguanidine according to any one of claims 6 to 8, and the system comprises a feeding kettle, a dissolving kettle, a clarifying kettle, a microchannel reactor, a continuous crystallizer, a centrifuge and a concentration device;
the feeding kettle is used for receiving concentrated sulfuric acid and guanidine nitrate to obtain a mixed material;
the dissolving kettle is used for receiving the mixed material fed by the feeding kettle to obtain a dissolved material;
the clarifying kettle is used for filtering the dissolved material fed from the dissolving kettle to obtain guanidine nitrate acid liquid, and the clarifying kettle is connected with the feeding kettle and is used for feeding the guanidine nitrate acid liquid into the feeding kettle;
the microchannel reactor is used for receiving guanidine nitrate acid solution fed from the clarifying kettle to obtain a reacted material;
the continuous crystallizer is used for receiving the reacted material fed by the microchannel reactor to obtain a crystallization feed liquid;
the centrifugal machine is used for receiving the crystallization feed liquid fed by the continuous crystallizer to obtain nitroguanidine and dilute sulfuric acid;
the concentration device is used for receiving dilute sulfuric acid fed by the centrifuge and feeding concentrated sulfuric acid obtained after concentration into the feeding kettle.
10. Nitroguanidine obtained by the method for preparing nitroguanidine according to any one of claims 1 to 8, wherein the purity of the nitroguanidine is more than 99%, and the weight ratio of water in the nitroguanidine is 20 to 25% based on the total weight of the nitroguanidine.
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