CN112979472B - Method for continuously producing dinitrobenzene - Google Patents
Method for continuously producing dinitrobenzene Download PDFInfo
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- CN112979472B CN112979472B CN201911294391.1A CN201911294391A CN112979472B CN 112979472 B CN112979472 B CN 112979472B CN 201911294391 A CN201911294391 A CN 201911294391A CN 112979472 B CN112979472 B CN 112979472B
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C201/00—Preparation of esters of nitric or nitrous acid or of compounds containing nitro or nitroso groups bound to a carbon skeleton
- C07C201/06—Preparation of nitro compounds
- C07C201/08—Preparation of nitro compounds by substitution of hydrogen atoms by nitro groups
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J19/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
- B01J19/0093—Microreactors, e.g. miniaturised or microfabricated reactors
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C201/00—Preparation of esters of nitric or nitrous acid or of compounds containing nitro or nitroso groups bound to a carbon skeleton
- C07C201/06—Preparation of nitro compounds
- C07C201/16—Separation; Purification; Stabilisation; Use of additives
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J2219/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
- B01J2219/00781—Aspects relating to microreactors
- B01J2219/00851—Additional features
- B01J2219/00867—Microreactors placed in series, on the same or on different supports
Abstract
A method for continuously producing dinitrobenzene adopts a multistage series reaction device as shown in the figure, which specifically comprises the following steps: continuously feeding raw material benzene or nitrobenzene into a first-stage nitrator, carrying out nitration reaction with mixed acid from a first-stage mixed acid mixer, continuously feeding a first-stage nitrator into a first-stage separator for separation, continuously feeding separated organic matters into a second-stage nitrator, carrying out nitration reaction with mixed acid from the second-stage mixed acid mixer, continuously feeding the second-stage nitrator into a second-stage separator for separation, continuously feeding separated organic matters into a next-stage nitrator for nitration reaction, and continuously feeding separated acid phases into a first-stage mixed acid mixer for mixing with added concentrated nitric acid in a countercurrent manner for the nitration reaction; and carrying out step-by-step reaction until dinitrobenzene products are obtained by separation in a final-stage separator. The method can strengthen the reaction mass transfer effect, improve the reaction efficiency, reduce the sulfuric acid consumption and improve the process safety performance.
Description
Field of the art
The invention relates to the technical field of chemical industry, in particular to a method for preparing dinitrobenzene by continuous nitration.
(II) background art
Dinitrobenzene is a generic name for m-dinitrobenzene, p-dinitrobenzene and o-dinitrobenzene, and is generally used as an important intermediate raw material for the production of dyes, pigments, agricultural chemicals, and the like. The synthesis of dinitrobenzene basically adopts a benzene two-stage nitration process: benzene and mixed acid are subjected to primary nitrification to obtain nitrobenzene, and nitrobenzene and mixed acid are subjected to secondary nitrification to obtain mixed dinitrobenzene containing three isomers; directly using nitrobenzene as raw material, and nitrifying with mixed acid to obtain dinitrobenzene. The traditional intermittent kettle type nitration process has the problems of large temperature difference, easy explosion, large acid wastewater amount, difficult treatment and the like in the production process, and has low production efficiency and intrinsic safety. The transition from batch to continuous flow reactions is one of the current trends in the fine chemical industry. CN108586256a discloses countercurrent continuous nitration technology based on multi-tank series connection: nitrobenzene is used as a raw material, and 4-level continuous countercurrent nitration is carried out to obtain dinitrobenzene. The patent is kettle type nitration reaction, the reaction process is highly exothermic, the kettle type nitration reactor is limited by structural characteristics, the overall mass transfer and heat transfer effects are poor, the liquid holdup of the nitration process reactor mainly comprising kettle type nitration is large, and certain safety risks still exist in the production process. CN103044261B adopts a centrifugal extractor as a nitration reactor and also serves as a separator, and carries out continuous countercurrent benzene nitration to prepare nitrobenzene. Firstly, a centrifugal extractor is an extraction device which utilizes centrifugal force to enable two phases to be rapidly mixed and separated, the device is mainly used as separation equipment, the liquid residence time is extremely short, the device is used as a nitration reactor, and how to effectively realize continuous reaction and continuous separation of materials and obtain better reaction effect is critical, so that the device is not described in detail in the patent; second, benzene in this patent: nitric acid: sulfuric acid = 1.1:1:10.6 (molar ratio), the sulfuric acid is used in too large an amount; meanwhile, the process is used for a system for preparing nitrobenzene by benzene nitration, the reaction and separation difficulty is relatively small, and if the equipment is applied to the reaction for preparing dinitrobenzene by benzene/nitrobenzene nitration, whether the better reaction and separation effect are achieved is unknown.
The micro-reaction system is also reported in the application research of the nitration technology of dinitrobenzene. Patent CN104844462a discloses a synthesis process of diaminobenzene compounds, which uses benzene as a raw material, and carries out continuous nitration on a microreactor platform to obtain mixed dinitrobenzene compounds. In the patent, raw materials of benzene, nitric acid and sulfuric acid are simultaneously added into a reactor for nitration reaction, dinitrobenzene is directly prepared through primary nitration reaction, the preparation ratio of the concentrated sulfuric acid is relatively high, and the yield of dinitrobenzene is low. Patent CN102432410B discloses a continuous production process of tubular nitrification and tubular washing, which adopts two or more sections of tubular reactors in series, raw material nitric acid is added at one time at the inlet of the tubular nitrification reactor or is added at the inlet and other parts of the tubular nitrification reactor respectively, an acid phase and organic phase separator is additionally arranged between the sections, the concentration of the separated acid phase is changed by adding nitric acid, and then the separated acid phase and the separated organic phase are combined and enter the tubular nitrification reactor of the next section, and the patent generally adopts a parallel flow nitrification process of co-current flowing mixed acid and materials to be nitrified. The parallel flow nitration reaction is characterized in that as the reaction proceeds, the acidity of sulfuric acid in the system is lower and lower, and the method requires the addition of sufficient sulfuric acid or additional supplemental acid to ensure the acidity of sulfuric acid in the nitration process system during the initial reaction. The methods disclosed in the two patents have the problem of large sulfuric acid consumption, and increase the raw material consumption and the waste acid treatment cost.
The mixed acid nitrifies to prepare dinitrobenzene and reacts in heterogeneous phase, the nitrifies speed is controlled by mass transfer between phases and chemical kinetics, sulfuric acid concentration, reaction temperature, stirring speed and the like have important influence on reaction speed and even yield, the kettle type nitrifies the stirring strength to improve and is helpful for strengthening mass transfer, but the diameter of liquid drops is relatively reduced, so that the separation time is longer.
(III) summary of the invention
The invention aims to provide a method for continuously producing dinitrobenzene by utilizing multistage microreactors which are connected in series, which strengthens the mass transfer effect of the reaction, improves the reaction efficiency, reduces the use amount of sulfuric acid and improves the process safety performance.
In order to achieve the above purpose, the invention adopts the following technical scheme:
a method for continuously producing dinitrobenzene adopts a multi-stage reaction device in series, wherein each stage of reaction device comprises a mixed acid mixer, a nitrator and a separator which are sequentially connected, the nitrator adopts a microreactor, the separator of each stage is connected with the nitrator of the next stage, and the mixed acid mixer of each stage is connected with the separator of the next stage; the method comprises the following steps: raw material benzene or nitrobenzene continuously enters from a first-stage nitrator, concentrated sulfuric acid is continuously added into a final-stage mixed acid mixer, concentrated nitric acid is continuously added into each stage of mixed acid mixer, and the method comprises the following steps:
continuously feeding raw material benzene or nitrobenzene into a first-stage nitrator, carrying out nitration reaction with mixed acid from a first-stage mixed acid mixer, continuously feeding the obtained first-stage nitrator into a first-stage separator for separation, continuously feeding the separated organic phase into a second-stage nitrator, carrying out nitration reaction with mixed acid from a second-stage mixed acid mixer, continuously feeding the obtained second-stage nitrator into a second-stage separator for separation, continuously feeding the separated organic phase into a next-stage nitrator for nitration reaction until the obtained final-stage nitrator continuously feeds into a final-stage separator for separation after the final-stage nitrator reaction, and obtaining a dinitrobenzene product; the raw materials of concentrated sulfuric acid and concentrated nitric acid are mixed by a final-stage mixed acid mixer and then enter a final-stage nitrifier, the acid phase is separated by a final-stage separator after reaction, the acid phase reversely flows into a last-stage mixed acid mixer, enters the last-stage nitrifier together with the added concentrated nitric acid, and the acid phase separated by the last-stage separator after reaction continues to enter the last stage until the acid phase separated by the first-stage separator is discharged as waste acid after reaction from the first-stage nitrifier.
The nitrifier mentioned in the reaction device adopts a micro-reactor, namely micro-chemical equipment with the inner diameter of a reaction channel in the reactor between a few micrometers to hundreds or even thousands of micrometers (preferably 50-1500 micrometers), and the micro-chemical equipment has extremely large specific surface area due to the miniaturization of the system size, so that the nitrifier has excellent mass transfer and heat exchange capacity, and the commercially available plate-type, coil-type or tubular micro-reactor belongs to the micro-reaction system and can be used in the invention. Wherein, the plate type microreactor can be a corning reactor, an SZ type reactor, a mixed TG type reactor, a Venturi type reactor and a sickle type reactor. The coiled-tube microreactor may comprise a star or an inter-digitated mixing system. The tubular microreactors may include T-type or Y-type mixing systems, and the like.
In the nitration reaction, when benzene is used as a raw material to synthesize dinitrobenzene, the total molar ratio of the raw materials is benzene: nitric acid: sulfuric acid = 1: (2-2.3): (1-2), preferably the molar ratio is benzene: nitric acid: sulfuric acid = 1: (2-2.3): (1-1.5). When nitrobenzene is used as a raw material to synthesize dinitrobenzene, the total molar ratio of the raw materials is nitrobenzene: nitric acid: sulfuric acid = 1: (1-1.2): (1-2), preferably the molar ratio is nitrobenzene: nitric acid: sulfuric acid = 1: (1-1.2): (1-1.5). The nitric acid content in the above proportion is calculated by the total amount of the added nitric acid, and the concentrated nitric acid added into each stage of the mixed acid mixer can be distributed in equal quantity according to the number of stages, and the adding proportion of each stage can be set according to the specific engineering design requirement. However, the total amount of nitric acid added is unchanged regardless of the amount of each stage added.
In the above-mentioned nitration reaction, when dinitrobenzene is synthesized from benzene, the reaction apparatus is preferably connected in series at 3 or more stages, more preferably 3 to 5 stages.
In the above-mentioned nitration reaction, when dinitrobenzene is synthesized from nitrobenzene as a raw material, the reaction apparatus is preferably connected in series at 2 or more stages, more preferably 2 to 4 stages.
In the above-mentioned nitration reaction, the reaction temperature of the first stage nitrator is preferably 30-50 ℃, the reaction temperature of the final stage nitrator is preferably 70-100 ℃, and the reaction temperature of the next stage nitrator is preferably 10-20 ℃ higher than the reaction temperature of the previous stage nitrator; the residence time in a single-stage nitrator is less than or equal to 30s (preferably 10-30 s), and the total residence time in each stage of nitrator is less than or equal to 200s (preferably 30-150 s); the operating temperature of each stage separator is consistent with the reaction temperature of the same-stage nitrator.
The separation of the organic phase and the inorganic acid phase of the nitrites is carried out in each stage of the separator, and one or a combination of at least two of gravity sedimentation separation, centrifugal separation, magnetic separation and coalescence separation can be adopted.
The gravity sedimentation realizes separation by utilizing the specific gravity difference of the materials to be separated. Still further, the gravity settling separator may be a static settling separator with only empty drums, or may be a separator containing internals such as plates or inclined tubes or packing.
The centrifugal separation is to utilize the materials to be separated to rotate in a separator to generate different centrifugal forces so as to separate an organic phase from an acid phase, and the centrifugal separator can be a tube type centrifuge, a disc type separator and the like which can provide liquid-liquid separation, and is preferably a separator which can be continuously separated.
The magnetic separation technology refers to that materials to be separated vertically flow through a magnetic field, magnetic force lines are cut to generate Lorentmagnetic force, the Lorentmagnetic force enables acid phase liquid drops to be separated from an emulsion film, and the Lorentmagnetic force is combined with adjacent liquid drops to form large liquid drops which are settled and separated from the emulsion, so that separation of organic matters and water phases is realized. The magnetic separator may be a permanent magnet of various shapes, such as a cylinder, cone or cone-like permanent magnet.
The coalescence and separation are realized by a coalescence separator with a built-in filter element, and the absorption force of the coalescence material of the filter element on the organic phase and the acid phase in the nitrified material is different, and tiny acid phase liquid drops serving as the disperse phase are coalesced into larger liquid drops, and are separated from the nitrified substances under the action of gravity and a flow field after the liquid drop size reaches a certain degree, so that the separation of the organic phase and the acid phase is realized.
Preferably, the process condition of preparing dinitrobenzene based on nitration of a reaction device adopts dinitration of benzene as a raw material, the separation of the first-stage nitrifier adopts a gravity sedimentation separation technology as a base selection, the separation of nitrifiers with more than two stages is needed to be enhanced, and the separation process adopts a centrifugal separation and/or magnetic separation and/or coalescence separation technology or the combination of the centrifugal separation and/or magnetic separation and/or coalescence separation technology and the gravity sedimentation separation technology, so that the deep separation of an organic phase and an acid phase is realized, and the continuous reaction is ensured.
Preferably, the separation process of each stage of nitrites taking nitrobenzene as a raw material needs to be enhanced, and the deep separation of an organic phase and an acid phase is realized by adopting a centrifugal separation and/or magnetic separation and/or coalescence separation technology or a combination of the centrifugal separation and/or magnetic separation and/or coalescence separation technology and a gravity sedimentation separation technology, so that the continuous reaction is ensured.
The gravity settling separator, centrifugal separator, magnetic separator and coalescing separator used in the present invention may be commercially available conventional ones.
Compared with the prior art, the invention has the following substantial characteristics and advantages:
(1) The micro-reactor is adopted for nitration reaction, heat transfer and mass transfer are enhanced, and meanwhile, the reaction rate is further improved, so that the improvement of the product yield is facilitated; compared with a kettle type reactor, the liquid holdup is greatly reduced, the instant reaction materials are fewer, and the safety risk is reduced; the method has no amplification effect, shortens the reaction period and has more competitive power; meanwhile, the operation of workers is convenient, the safety production is facilitated, and the accurate and automatic control is easy to realize.
(2) Multistage countercurrent nitration is carried out, and each stage of waste acid is used as the preceding stage of nitration acid, so that the yield of reaction waste acid is greatly reduced;
(3) By adopting a proper separation mode combination, the problem of deep separation of an organic phase and an acid phase is effectively solved, and the efficient continuous nitration of benzene/nitrobenzene is facilitated to produce dinitrobenzene.
(IV) description of the drawings
FIG. 1 is a schematic illustration of the process flow of the present invention.
(fifth) detailed description of the invention
The invention will be further described with reference to the following specific examples, but the scope of the invention is not limited thereto:
the gravity sedimentation separator adopted by the embodiment of the invention is an inclined plate gravity separator; the adopted magnetic separator is a cylindrical permanent magnet; the coalescing separator used was a corrugated coalescing plate separator from Fram company, uk; the centrifugal separator is a butterfly type centrifugal separator of Liaoning huge minister pharmaceutical machinery Co.
Example 1
Continuously adding metered raw material benzene into a first-stage nitrator, continuously adding concentrated sulfuric acid into a third-stage mixed acid mixer, continuously adding concentrated nitric acid into each stage of mixed acid mixer, mixing mixed acid through the third-stage mixed acid mixer, introducing the mixed acid into the third-stage nitrator, carrying out nitration reaction with the nitrating substance from the second-stage separator in the third-stage nitrator, introducing the nitrating substance into the third-stage separator, separating an organic nitrating substance from the third-stage separator into a product, introducing an acid phase into the second-stage mixed acid mixer, mixing the organic nitrating substance with added fresh concentrated nitric acid, introducing the mixed acid with the nitrating substance from the first-stage separator into the second-stage nitrator for nitration reaction, introducing the separated nitrating substance from the second-stage separator into the third-stage nitrator, introducing the separated acid phase into the first-stage mixed acid mixer, and mixing the separated organic nitrating substance with the added fresh concentrated nitric acid. Raw material benzene reacts with mixed acid from a first-stage mixed acid mixer and then enters a first-stage separator, an organic phase obtained by separation enters a second-stage nitrifier to continue reaction, and waste acid obtained by separation is treated. In the embodiment, the nitrator is a corning G1 microreactor, the nitrator and mixed acid in the whole system are in countercurrent reaction, and the total adding amount ratio (molar ratio) of the raw materials of the reaction system is benzene: concentrated nitric acid: concentrated sulfuric acid=1: 2.3:1.5, adding concentrated nitric acid in equal number according to the number of stages. Wherein the reaction temperature of the first-stage nitrator material is 40 ℃ and the residence time is 20s; the reaction temperature of the second-stage nitrator material is 60 ℃ and the residence time is 20s; the reaction temperature of the materials of the third-stage nitrator is 80 ℃ and the retention time is 20s; the operating temperature of each stage separator is consistent with the reaction temperature of the same-stage nitrator. The first-stage separator adopts a gravity sedimentation mode, the second-stage separator and the third-stage separator adopt a magnetic separation mode, and the third-stage separator adopts a coalescence separation mode. After three-stage continuous countercurrent nitration reaction, the yield of mixed dinitrate is 99.1 percent.
Example two
According to the process described in the first embodiment, 4-stage countercurrent mode is adopted for continuous nitration reaction, namely, metered raw material benzene is continuously added into a first-stage nitrator, concentrated sulfuric acid is continuously added into a fourth-stage mixed acid mixer, and concentrated nitric acid is continuously added into each stage of mixed acid mixer; mixed acid enters a fourth-stage nitrator after being mixed by a fourth-stage mixed acid mixer, and then flows into each-stage nitrator by the fourth-stage nitrator one by one until being separated and discharged through a first-stage separator after being reacted from the first-stage nitrator; the nitrifiers flow into each stage of nitrifiers from the first stage nitrifiers one by one until the nitrifiers react with the fourth stage nitrifiers and are separated by the fourth stage separators to obtain the product. In the embodiment, the nitrator is a Venturi microreactor of Lonza company, and the total addition amount ratio (molar ratio) of the raw materials of the whole reaction system is benzene: concentrated nitric acid: concentrated sulfuric acid=1: 2.3:1.4, adding concentrated nitric acid in equal number according to the number of stages. Wherein the material reaction temperature of the first-stage nitrator is 35 ℃, the material reaction temperature of the second-stage nitrator is 50 ℃, the material reaction temperature of the third-stage nitrator is 65 ℃, the material reaction temperature of the fourth-stage nitrator is 75 ℃, and the retention time of each stage is 25s; the operating temperature of each stage separator is consistent with the reaction temperature of the same-stage nitrator. The first-stage separator adopts a gravity sedimentation mode, the second-stage separator adopts a centrifugal separation mode, the third-stage separator adopts a magnetic separation mode, and the fourth-stage separator adopts a coalescence separation mode. After four-stage continuous countercurrent nitration reaction, the yield of mixed dinitrate is 99.3 percent.
Example III
According to the process described in the first embodiment, a 5-stage countercurrent mode is adopted for continuous nitration reaction, namely, metered raw material benzene is continuously added into a first-stage nitrator, concentrated sulfuric acid is continuously added into a fifth-stage mixed acid mixer, and concentrated nitric acid is continuously added into each stage of mixed acid mixer; mixed acid enters a fifth-stage nitrator after being mixed by a fifth-stage mixed acid mixer, and then flows into each-stage nitrator by the fifth-stage nitrator one by one until being separated and discharged by a first-stage separator after being reacted by a first-stage nitrator; the nitrifiers flow into each stage of nitrifiers from the first stage nitrifiers one by one until the nitrifiers react from the fifth stage nitrifiers and are separated by the fifth stage separators to obtain the product. In the embodiment, the nitrator is a star-shaped coil type microreactor (micromixer of DayiKai company+1/8 inch inner diameter hastelloy coil), and the total addition amount ratio (molar ratio) of raw materials of the whole reaction system is benzene: concentrated nitric acid: concentrated sulfuric acid=1: 2.3:1.3, adding concentrated nitric acid in equal number according to the number of stages. Wherein the reaction temperature of the first-stage nitrator material is 35 ℃, the reaction temperature of the second-stage nitrator material is 45 ℃, the reaction temperature of the third-stage nitrator material is 60 ℃, the reaction temperature of the fourth-stage nitrator material is 70 ℃, and the reaction temperature of the fifth-stage nitrator material is 80 ℃, and the retention time of each stage is 30s; the operating temperature of each stage separator is consistent with the reaction temperature of the same-stage nitrator. The first and second separators adopt a centrifugal mode, the third and fourth separators adopt a magnetic separation mode, and the fifth separator adopts a coalescence separation mode. After five-stage continuous countercurrent nitration reaction, the yield of mixed dinitrate is 99.4 percent.
Example IV
According to the process described in the first embodiment, a 3-stage countercurrent mode is adopted for continuous nitration reaction, namely, the metered raw material nitrobenzene is continuously added into a first-stage nitrator, the concentrated sulfuric acid is continuously added into a third-stage mixed acid mixer, and the concentrated nitric acid is continuously added into each stage of mixed acid mixer; mixed acid enters a third-stage nitrator after being mixed by a third-stage mixed acid mixer, and then flows into each-stage nitrator by the third-stage nitrator one by one until being separated and discharged by a first-stage separator after being reacted by a first-stage nitrator; the nitrifiers flow into each stage of nitrifiers from the first stage nitrifiers one by one until the nitrifiers react from the third stage nitrifiers and are separated by the third stage separators to obtain the product. In the embodiment, the nitrator is an SZ-shaped type microreactor of Lonza company, and the total addition amount ratio (molar ratio) of raw materials of the whole reaction system is nitrobenzene: concentrated nitric acid: concentrated sulfuric acid=1: 1.1:1.8, wherein concentrated nitric acid is added in a series equal amount distribution manner. Wherein the reaction temperature of the first-stage nitrifier material is 50 ℃, the reaction temperature of the second-stage nitrifier material is 70 ℃, the reaction temperature of the third-stage nitrifier material is 80 ℃, and the retention time of each stage is 15s; the operating temperature of each stage separator is consistent with the reaction temperature of the same-stage nitrator. The first-stage separator adopts a centrifugal mode, the second-stage separator adopts a magnetic separation mode, and the third-stage separator adopts a coalescence separation mode. After three-stage continuous countercurrent nitration reaction, the yield of mixed dinitrate is 99.2 percent.
Example five
According to the process in the first embodiment, 4-stage countercurrent mode is adopted for continuous nitration reaction, namely, metered raw material nitrobenzene is continuously added into a first-stage nitrator, concentrated sulfuric acid is continuously added into a fourth-stage mixed acid mixer, and concentrated nitric acid is continuously added into each stage of mixed acid mixer; mixed acid enters a fourth-stage nitrator after being mixed by a fourth-stage mixed acid mixer, and then flows into each-stage nitrator by the fourth-stage nitrator one by one until being separated and discharged through a first-stage separator after being reacted from the first-stage nitrator; the nitrifiers flow into each stage of nitrifiers from the first stage nitrifiers one by one until the nitrifiers react with the fourth stage nitrifiers and are separated by the fourth stage separators to obtain the product. In the embodiment, the nitrifier is a tubular microreactor (T-shaped mixer with 1/16 inch inner diameter and hastelloy coil with 1/16 inch inner diameter), and the total addition amount ratio (molar ratio) of raw materials of the whole reaction system is nitrobenzene: concentrated nitric acid: concentrated sulfuric acid=1: 1.1:1.4, adding concentrated nitric acid in an equivalent way. Wherein the reaction temperature of the first-stage nitrifier material is 30 ℃, the reaction temperature of the second-stage nitrifier material is 45 ℃, the reaction temperature of the third-stage nitrifier material is 60 ℃, the reaction temperature of the fourth-stage nitrifier material is 75 ℃, and the retention time of each stage is 25s; the operating temperature of each stage separator is consistent with the reaction temperature of the same-stage nitrator. The first and second separators adopt a magnetic separation mode, and the third and fourth separators adopt a coalescence separation mode. After four-stage continuous countercurrent nitration reaction, the yield of mixed dinitrate is 99.4 percent.
Claims (11)
1. A method for continuously producing dinitrobenzene, which is characterized in that: the method adopts a multistage reaction device connected in series, each stage of reaction device comprises a mixed acid mixer, a nitrifier and a separator which are sequentially connected, the nitrifier adopts a micro-reactor, the separator of each stage is connected with the nitrifier of the next stage, and the mixed acid mixer of each stage is connected with the separator of the next stage; the method comprises the following steps: raw material benzene or nitrobenzene continuously enters from a first-stage nitrator, concentrated sulfuric acid is continuously added into a final-stage mixed acid mixer, concentrated nitric acid is continuously added into each stage of mixed acid mixer, and the method comprises the following steps:
continuously feeding raw material benzene or nitrobenzene into a first-stage nitrator, carrying out nitration reaction with mixed acid from a first-stage mixed acid mixer, continuously feeding the obtained first-stage nitrator into a first-stage separator for separation, continuously feeding the separated organic phase into a second-stage nitrator, carrying out nitration reaction with mixed acid from a second-stage mixed acid mixer, continuously feeding the obtained second-stage nitrator into a second-stage separator for separation, continuously feeding the separated organic phase into a next-stage nitrator for nitration reaction until the obtained final-stage nitrator continuously feeds into a final-stage separator for separation after the final-stage nitrator reaction, and obtaining a dinitrobenzene product; the raw materials of concentrated sulfuric acid and concentrated nitric acid are mixed by a final-stage mixed acid mixer and then enter a final-stage nitrifier, an acid phase is separated by a final-stage separator after reaction, and flows into a last-stage mixed acid mixer reversely, and enters the last-stage nitrifier together with the added concentrated nitric acid, and the acid phase separated by the last-stage separator after reaction continues to enter the last stage until the acid phase separated by the first-stage separator is discharged as waste acid after reaction from the first-stage nitrifier;
when benzene is used as a raw material to synthesize dinitrobenzene, a gravity sedimentation separation technology is adopted in a first-stage separator, and centrifugal separation and/or magnetic separation and/or coalescence separation technology or a combination of the centrifugal separation and/or magnetic separation and/or coalescence separation technology and the gravity sedimentation separation technology is adopted in a separator with more than two stages;
when nitrobenzene is used as raw material to synthesize dinitrobenzene, each stage of separator adopts centrifugal separation and/or magnetic separation and/or coalescence separation technology, or the combination of centrifugal separation and/or magnetic separation and/or coalescence separation technology and gravity sedimentation separation technology.
2. The method of claim 1, wherein: when benzene is used as a raw material to synthesize dinitrobenzene, the total molar ratio of the raw materials is benzene: nitric acid: sulfuric acid = 1: (2-2.3): (1-2); when nitrobenzene is used as a raw material to synthesize dinitrobenzene, the total molar ratio of the raw materials is nitrobenzene: nitric acid: sulfuric acid = 1: (1-1.2): (1-2).
3. The method of claim 2, wherein: when benzene is used as a raw material to synthesize dinitrobenzene, the total molar ratio of the raw materials is benzene: nitric acid: sulfuric acid = 1: (2-2.3): (1-1.5).
4. The method of claim 2, wherein: when nitrobenzene is used as a raw material to synthesize dinitrobenzene, the total molar ratio of the raw materials is nitrobenzene: nitric acid: sulfuric acid = 1: (1-1.2): (1-1.5).
5. The method of claim 1, wherein: concentrated nitric acid added into each stage of mixed acid mixer is distributed in equal number according to the number of stages.
6. The method of any one of claims 1-5, wherein: when benzene is used as a raw material to synthesize dinitrobenzene, the reaction device is connected in series with more than 3 stages; when nitrobenzene is used as raw material to synthesize dinitrobenzene, the reaction device is connected in series with more than 2 stages.
7. The method of claim 6, wherein: when benzene is used as raw material to synthesize dinitrobenzene, the reaction devices are connected in series in 3-5 stages.
8. The method of claim 6, wherein: when nitrobenzene is used as raw material to synthesize dinitrobenzene, the reaction devices are connected in series in 2-4 stages.
9. The method of any one of claims 1-5 and 7-8, wherein: the reaction temperature of the first-stage nitrator is 30-50 ℃, the reaction temperature of the final-stage nitrator is 70-100 ℃, and the reaction temperature of the next-stage nitrator is 10-20 ℃ higher than the reaction temperature of the last-stage nitrator; the residence time in the single-stage nitrifier is less than or equal to 30s, and the total residence time in each stage nitrifier is less than or equal to 200s; the operating temperature of each stage separator is consistent with the reaction temperature of the same-stage nitrator.
10. The method of claim 6, wherein: the reaction temperature of the first-stage nitrator is 30-50 ℃, the reaction temperature of the final-stage nitrator is 70-100 ℃, and the reaction temperature of the next-stage nitrator is 10-20 ℃ higher than the reaction temperature of the last-stage nitrator; the residence time in the single-stage nitrifier is less than or equal to 30s, and the total residence time in each stage nitrifier is less than or equal to 200s; the operating temperature of each stage separator is consistent with the reaction temperature of the same-stage nitrator.
11. The method of claim 9, wherein: the residence time in the single-stage nitrator is 10-30s, and the total residence time in each stage of nitrator is 30-150s.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
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| CN104487413A (en) * | 2012-07-27 | 2015-04-01 | 拜耳材料科技股份有限公司 | Method for producing nitrobenzene by adiabatic nitriding |
| CN109232272A (en) * | 2018-11-13 | 2019-01-18 | 淮安绿源化工科技有限公司 | A kind of production system and technique of the aromatic amine of safety and environmental protection |
| CN109970566A (en) * | 2019-04-19 | 2019-07-05 | 山东豪迈化工技术有限公司 | A kind of synthetic method of 1,3- dinitro halobenzene compound |
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| CN104487413A (en) * | 2012-07-27 | 2015-04-01 | 拜耳材料科技股份有限公司 | Method for producing nitrobenzene by adiabatic nitriding |
| CN109232272A (en) * | 2018-11-13 | 2019-01-18 | 淮安绿源化工科技有限公司 | A kind of production system and technique of the aromatic amine of safety and environmental protection |
| CN109970566A (en) * | 2019-04-19 | 2019-07-05 | 山东豪迈化工技术有限公司 | A kind of synthetic method of 1,3- dinitro halobenzene compound |
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