CN114634417B - Preparation method of nitrophthalic acid - Google Patents
Preparation method of nitrophthalic acid Download PDFInfo
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- CN114634417B CN114634417B CN202210223161.1A CN202210223161A CN114634417B CN 114634417 B CN114634417 B CN 114634417B CN 202210223161 A CN202210223161 A CN 202210223161A CN 114634417 B CN114634417 B CN 114634417B
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
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- 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
- C07C201/12—Preparation of nitro compounds by reactions not involving the formation of nitro groups
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- C07C201/00—Preparation of esters of nitric or nitrous acid or of compounds containing nitro or nitroso groups bound to a carbon skeleton
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- C07D—HETEROCYCLIC COMPOUNDS
- C07D307/00—Heterocyclic compounds containing five-membered rings having one oxygen atom as the only ring hetero atom
- C07D307/77—Heterocyclic compounds containing five-membered rings having one oxygen atom as the only ring hetero atom ortho- or peri-condensed with carbocyclic rings or ring systems
- C07D307/87—Benzo [c] furans; Hydrogenated benzo [c] furans
- C07D307/89—Benzo [c] furans; Hydrogenated benzo [c] furans with two oxygen atoms directly attached in positions 1 and 3
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- B01J2219/00781—Aspects relating to microreactors
- B01J2219/00788—Three-dimensional assemblies, i.e. the reactor comprising a form other than a stack of plates
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- B01J2219/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
- B01J2219/00781—Aspects relating to microreactors
- B01J2219/00873—Heat exchange
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Abstract
The invention provides a preparation method of nitrophthalic acid, and relates to the technical field of organic synthesis. According to the invention, phthalic anhydride-concentrated sulfuric acid mixed solution and concentrated nitric acid-salt (nitrate and/or nitrite) mixed solution are introduced into a microchannel reactor to sequentially perform pre-nitration and nitration, and isomer separation is performed after hydrolysis, so that nitrophthalic acid is obtained. The invention utilizes the efficient mass transfer and heat transfer efficiency of the microchannel reactor, effectively strengthens the mass transfer rate between two-phase materials and obviously reduces the reaction time; the reaction temperature is stabilized by two steps of reaction, the safety and the operability are greatly improved, and 3-nitrophthalic acid and 4-nitrophthalic acid can be efficiently and continuously produced. According to the invention, the interaction of nitrate and/or nitrite, carboxyl on benzene ring and nitro ion in a reaction system is introduced, so that the selectivity of 4-nitrophthalic acid is improved. Moreover, the preparation method provided by the invention is simple to operate and suitable for industrial production.
Description
Technical Field
The invention relates to the technical field of organic synthesis, in particular to a preparation method of nitrophthalic acid.
Background
4-nitrophthalic acid and 3-nitrophthalic acid are important organic synthesis intermediates, 4-nitrophthalic acid can be used for preparing 4-chlorophthalic anhydride, and 4-chlorophthalic anhydride is a main raw material of 3,3', 4' -biphenyl dianhydride; the 3-nitrophthalic acid can be used for synthesizing photosensitive materials, medicaments (candesartan cilexetil), dyes, crop protection agents and the like.
At present, the synthesis method of 4-nitrophthalic acid and 3-nitrophthalic acid mainly uses phthalic anhydride to make nitration. For example, chinese patent CN1405143a discloses a process for preparing 3-nitrophthalic acid: a. using phthalic anhydride as raw material, using nitrating agent (concentrated sulfuric acid and concentrated nitric acid, potassium nitrate and sulfuric acid, nitric acid and glacial acetic acid) to produce nitrobenzene anhydride; b. hydrolyzing the nitrophthalic anhydride to produce nitrophthalic acid; c. separating isomer 4-nitrophthalic acid to obtain 3-nitrophthalic acid. However, the method adopts a traditional reaction kettle to carry out the reaction, concentrated nitric acid needs to be added into a reaction system in a dropwise manner, the total reaction time is 11 hours, and the reaction time is long.
Disclosure of Invention
In view of the above, the present invention aims to provide a method for preparing nitrophthalic acid, which prepares nitrophthalic acid in a microchannel reactor with short reaction time.
In order to achieve the above object, the present invention provides the following technical solutions:
the invention provides a preparation method of nitrophthalic acid, which comprises the following steps:
mixing phthalic anhydride and concentrated sulfuric acid to obtain phthalic anhydride-concentrated sulfuric acid mixed solution;
mixing the water-soluble salt with concentrated nitric acid to obtain concentrated nitric acid-salt mixed solution; the water soluble salt comprises nitrate and/or nitrite;
introducing the phthalic anhydride-concentrated sulfuric acid mixed solution and the concentrated nitric acid-salt mixed solution into a microchannel reactor to sequentially perform pre-nitration reaction and nitration reaction to obtain a mixed nitration product; the total time of the pre-nitration reaction and the nitration reaction is 17-26 min;
hydrolyzing the mixed nitration product to obtain mixed acid;
and (3) carrying out isomer separation on the mixed acid to obtain 3-nitrophthalic acid and 4-nitrophthalic acid respectively.
Preferably, the mass ratio of the phthalic anhydride to the concentrated sulfuric acid is 1:3 to 5;
the concentration of the concentrated sulfuric acid is 95-98wt%.
Preferably, the mass ratio of the concentrated nitric acid to the water soluble salt is 0.8-3: 0.05 to 0.2;
the concentration of the concentrated nitric acid is 65-68 wt%.
Preferably, the feed flow ratio of the phthalic anhydride-concentrated sulfuric acid mixed solution to the concentrated nitric acid-salt mixed solution is 3-5: 1.
preferably, the temperature of the pre-nitration reaction is 50-60 ℃, the pressure is 0-0.3 MPa, and the time is 9-13 min.
Preferably, the temperature of the nitration reaction is 90-100 ℃, the pressure is 0-0.3 MPa, and the time is 8-13 min.
Preferably, the isomer separation comprises:
adding water into the mixed acid, mixing, and then carrying out solid-liquid separation to obtain a first solid component and a liquid component;
recrystallizing the first solid component to obtain 3-nitrophthalic acid;
and cooling the liquid component, performing solid-liquid separation, and recrystallizing the obtained second solid component to obtain the 4-nitrophthalic acid.
The invention provides a device for preparing nitrophthalic acid, which comprises a first material conveying pump 1-1 and a second material conveying pump 1-2 which are connected in parallel;
the micro-channel reactor 2 is communicated with the first material conveying pump 1-1 and the second material conveying pump 1-2, the micro-channel reactor 2 is sequentially provided with a low-temperature area 2-1 and a high-temperature area 2-2 according to the flow direction of materials, the micro-channel reactor 2 is provided with a low-temperature area jacket 2-3 and a high-temperature area jacket 2-4, and heat exchange mediums are filled in the low-temperature area jacket 2-3 and the high-temperature area jacket 2-4;
and the double temperature control high-low temperature integrated machine 3 is communicated with the low temperature region jacket 2-3 and the high temperature region jacket 2-4.
Preferably, the microchannel reactor 2 has a microchannel with an inner diameter of 0.5-2 mm.
Preferably, the number of the reaction pieces of the micro-channel in the low temperature area 2-1 is 4-6; the number of the reaction pieces in the high temperature zone 2-1 is 4-8; the liquid holdup of the single-piece reaction piece is independently 8-20 mL.
The invention provides a preparation method of nitrophthalic acid, which comprises the following steps: mixing phthalic anhydride and concentrated sulfuric acid to obtain phthalic anhydride-concentrated sulfuric acid mixed solution; mixing the water-soluble salt with concentrated nitric acid to obtain concentrated nitric acid-salt mixed solution; the water soluble salt comprises nitrate and/or nitrite; introducing the phthalic anhydride-concentrated sulfuric acid mixed solution and the concentrated nitric acid-salt mixed solution into a microchannel reactor to sequentially perform pre-nitration reaction and nitration reaction to obtain a mixed nitration product; the total time of the pre-nitration reaction and the nitration reaction is 17-26 min; hydrolyzing the mixed nitration product to obtain mixed acid; and (3) carrying out isomer separation on the mixed acid to obtain 3-nitrophthalic acid and 4-nitrophthalic acid respectively. The invention utilizes the high-efficiency mass transfer and heat transfer efficiency of the microchannel reactor, effectively strengthens the mass transfer rate between two phase materials of phthalic anhydride-concentrated sulfuric acid mixed solution and concentrated nitric acid-salt mixed solution, and obviously reduces the reaction time; the reaction temperature is stabilized by two steps of reaction, the safety and operability of nitrophthalic acid preparation are greatly improved, and 3-nitrophthalic acid and 4-nitrophthalic acid can be produced efficiently and continuously. The phthalic anhydride conversion rate of the preparation method provided by the invention reaches 100%; in addition, nitrate and/or nitrite are introduced in the reaction process, and metal ions in the nitrate and/or nitrite are utilized to interact with carboxyl on a benzene ring and nitro ions in a reaction system, so that the selectivity of 4-nitrophthalic acid is improved, and the selectivity of 4-nitrophthalic acid is 74-81%. Moreover, the preparation method provided by the invention is simple to operate, good in safety and suitable for industrial production.
Drawings
FIG. 1 is a diagram of an apparatus for producing nitrophthalic acid, wherein 1-1 is a first feed pump, 1-2 is a second feed pump, 2 is a microchannel reactor, 2-1 is a low temperature zone, 2-2 is a high temperature zone, 2-3 is a low temperature zone jacket, 2-4 is a high temperature zone jacket, 3 is a dual temperature control high and low temperature integrated machine, 4-1 is a first raw material storage tank, 4-2 is a second raw material storage tank, and 5 is a product storage tank;
FIG. 2 is a schematic of a microchannel reactor;
fig. 3 is a schematic diagram of a heart-shaped microchannel.
Detailed Description
The invention provides a preparation method of nitrophthalic acid, which comprises the following steps:
mixing phthalic anhydride and concentrated sulfuric acid to obtain phthalic anhydride-concentrated sulfuric acid mixed solution;
mixing the water-soluble salt with concentrated nitric acid to obtain concentrated nitric acid-salt mixed solution; the water soluble salt comprises nitrate and/or nitrite;
introducing the phthalic anhydride-concentrated sulfuric acid mixed solution and the concentrated nitric acid-salt mixed solution into a microchannel reactor to sequentially perform pre-nitration reaction and nitration reaction to obtain a mixed nitration product; the total time of the pre-nitration reaction and the nitration reaction is 17-26 min;
hydrolyzing the mixed nitration product to obtain mixed acid;
and (3) carrying out isomer separation on the mixed acid to obtain 3-nitrophthalic acid and 4-nitrophthalic acid respectively.
In the present invention, all raw material components are commercially available products well known to those skilled in the art unless specified otherwise.
The invention mixes phthalic anhydride and concentrated sulfuric acid to obtain phthalic anhydride-concentrated sulfuric acid mixed solution. In the present invention, the concentration of the concentrated sulfuric acid is preferably 95 to 98wt%, more preferably 96 to 97wt%; the concentrated sulfuric acid is used as a solvent, a catalyst and a dehydrating agent. In the invention, the mass ratio of the phthalic anhydride to the concentrated sulfuric acid is preferably 1:3 to 5, more preferably 1:3 to 4. In the present invention, the mixing means is preferably stirring mixing, the temperature of the mixing is preferably 20 to 40 ℃, more preferably 30 ℃, the speed and time of the mixing are not particularly limited, and phthalic anhydride may be dissolved, for example, 0.5h.
The invention mixes water-soluble salt and concentrated nitric acid to obtain concentrated nitric acid-salt mixed solution. In the present invention, the concentrated nitric acid concentration is preferably 65 to 68wt%, more preferably 66 to 67wt%; the concentrated nitric acid acts as a nitrifying agent. In the present invention, the water-soluble salt includes nitrate and/or nitrite, and the nitrate preferably includes one or more of potassium nitrate, sodium nitrate and magnesium nitrate; the nitrite preferably comprises one or more of sodium nitrite, potassium nitrite and magnesium nitrite, and more preferably sodium nitrite. In the invention, the mass ratio of the water-soluble salt to the concentrated nitric acid is preferably 0.8-3: 0.05 to 0.2, more preferably 1 to 2.5:0.05 to 0.15, more preferably 1.5 to 2:0.1 to 0.12. In the present invention, the mode of the mixing is preferably ultrasonic mixing, the temperature of the mixing is preferably 20 to 40 ℃, more preferably 30 ℃, the ultrasonic power and time of the ultrasonic mixing are not particularly limited, and water-soluble salts can be dissolved, and the water-soluble salts can be dissolved for 0.5h.
After phthalic anhydride-concentrated sulfuric acid mixed solution and concentrated nitric acid-salt mixed solution are obtained, the phthalic anhydride-concentrated sulfuric acid mixed solution and the concentrated nitric acid-salt mixed solution are introduced into a micro-channel reactor to sequentially perform pre-nitration reaction and nitration reaction, so that a mixed nitration product is obtained; the total time of the pre-nitration reaction and the nitration reaction is 17-26 min.
In the invention, the feeding flow ratio of the phthalic anhydride-concentrated sulfuric acid mixed solution to the concentrated nitric acid-salt mixed solution is preferably 3-5: 1, more preferably 3.5 to 4.5:1, further preferably 4:1.
in the present invention, the temperature of the pre-nitration reaction is preferably 50 to 60 ℃, more preferably 55 ℃; the pressure of the pre-nitration reaction is preferably 0-0.3 MPa, more preferably 0.1-0.2 MPa; the time of the pre-nitration reaction is preferably 9 to 13 minutes, more preferably 10 to 12 minutes, and even more preferably 11 minutes. The invention carries out the pre-nitration reaction in the microchannel reactor at low temperature (50-60 ℃), has slower reaction, can avoid uncontrollable temperature and occurrence danger of high-temperature severe reaction, and has high safety.
In the present invention, the temperature of the nitration reaction is preferably 90 to 100 ℃, more preferably 95 ℃; the pressure of the nitration reaction is preferably 0 to 0.3MPa, more preferably 0.1 to 0.2MPa; the time of the nitration reaction is preferably 8 to 13 minutes, more preferably 9 to 12 minutes, and still more preferably 10 to 11 minutes. The invention carries out nitration reaction under the high temperature condition (90-100 ℃) in the microchannel reactor, and the reaction speed is high; the microchannel reactor adopts a sectional reaction mode, and can ensure that the temperature of the nitration reaction is controllable and the safety is high under the condition of obviously shortening the reaction time.
After the mixed nitration product is obtained, the mixed nitration product is hydrolyzed to obtain mixed acid.
Adding water into a product liquid obtained by the nitration reaction, mixing, and carrying out first solid-liquid separation to obtain a mixed nitration product. In the present invention, the hydrolysis is performed using water, and the mass of the water is preferably 3 to 5 times, more preferably 4 times, the mass of phthalic anhydride. In the present invention, the hydrolysis is preferably performed under stirring conditions, and the speed and time of the stirring are not particularly limited, and the stirring and mixing are only required until the solid product is not increased.
After the hydrolysis, the invention preferably further comprises solid-liquid separation of the hydrolysis system obtained by the hydrolysis to obtain mixed acid. The solid-liquid separation method is not particularly limited, and may be any solid-liquid separation method known to those skilled in the art, such as filtration or suction filtration.
After mixed acid is obtained, the mixed acid is subjected to isomer separation to obtain 3-nitrophthalic acid and 4-nitrophthalic acid respectively.
In the present invention, the isomer separation preferably includes:
adding water into the mixed acid, mixing, and then carrying out solid-liquid separation to obtain a first solid component and a liquid component;
recrystallizing the first solid component to obtain 3-nitrophthalic acid;
and cooling the liquid component, performing solid-liquid separation, and recrystallizing the obtained second solid component to obtain the 4-nitrophthalic acid.
According to the invention, water is added into the mixed acid for mixing, and then solid-liquid separation is carried out, so that a first solid component and a liquid component are obtained. In the present invention, the amount of water to be used is 3 to 5 times, more preferably 4 times, the mass of the mixed acid. In the present invention, the temperature is preferably increased by adding water, and then the second solid-liquid separation is performed, wherein the temperature of the second solid-liquid separation is preferably 60 to 90 ℃, more preferably 70 to 80 ℃. The mode of the second solid-liquid separation is not particularly limited, and a solid-liquid separation mode known to those skilled in the art may be adopted, and specifically filtration or suction filtration may be adopted.
After the first solid component is obtained, the first solid component is recrystallized to obtain the 3-nitrophthalic acid. In the present invention, the solvent for recrystallization is preferably water, and the mass of the water is preferably 2 to 5 times, more preferably 3 to 4 times that of the first solid component. In the present invention, the temperature of the recrystallization is preferably 85 to 95 ℃, more preferably 90 ℃; the recrystallization is preferably carried out under stirring, and the speed and time of the stirring are not particularly limited in the present invention, and the stirring is carried out until crystals are not increased. The recrystallization preferably further comprises cooling the recrystallized system, performing solid-liquid separation, and drying the obtained solid product to obtain 3-nitrophthalic acid; the temperature after the temperature reduction is preferably 20-30 ℃, more preferably 25 ℃; the solid-liquid separation mode is not particularly limited, and can be a solid-liquid separation mode well known to those skilled in the art, such as filtration or suction filtration; the drying temperature is preferably 100 to 120 ℃, more preferably 110 ℃, and the drying time is preferably 8 to 12 hours, more preferably 10 hours.
After obtaining the liquid component, the invention carries out solid-liquid separation after cooling the liquid component, and recrystallizes the obtained second solid component to obtain the 4-nitrophthalic acid. In the present invention, the temperature after the temperature reduction is preferably 0 to 10 ℃, more preferably 5 ℃. The solid-liquid separation method is not particularly limited, and may be any solid-liquid separation method known to those skilled in the art, such as filtration or suction filtration. In the present invention, the solvent for recrystallization is preferably water, and the mass of the water is preferably 2 to 5 times, more preferably 3 to 4 times that of the second solid component. In the present invention, the temperature of the recrystallization is preferably 50 to 80 ℃, more preferably 60 ℃; the recrystallization is preferably carried out under stirring, and the speed and time of the stirring are not particularly limited in the present invention, and the stirring is carried out until crystals are not increased. The recrystallization preferably further comprises cooling the recrystallized system, performing solid-liquid separation, and drying the obtained solid product to obtain 4-nitrophthalic acid; the temperature after the temperature reduction is preferably 0-10 ℃, more preferably 5 ℃; the solid-liquid separation mode is not particularly limited, and can be a solid-liquid separation mode well known to those skilled in the art, such as filtration or suction filtration; the drying temperature is preferably 100 to 120 ℃, more preferably 110 ℃, and the drying time is preferably 8 to 12 hours, more preferably 10 hours.
The invention provides a device for preparing nitrophthalic acid, which comprises a first material conveying pump 1-1 and a second material conveying pump 1-2 which are connected in parallel;
the micro-channel reactor 2 is communicated with the first material conveying pump 1-1 and the second material conveying pump 1-2, the micro-channel reactor 2 is sequentially provided with a low-temperature area 2-1 and a high-temperature area 2-2 according to the flow direction of materials, the micro-channel reactor 2 is provided with a low-temperature area jacket 2-3 and a high-temperature area jacket 2-4, and heat exchange mediums are filled in the low-temperature area jacket 2-3 and the high-temperature area jacket 2-4;
and the double temperature control high-low temperature integrated machine 3 is communicated with the low temperature region jacket 2-3 and the high temperature region jacket 2-4.
The device for preparing nitrophthalic acid provided by the invention comprises a first material conveying pump 1-1 and a second material conveying pump 1-2 which are connected in parallel; the first material conveying pump 1-1 is provided with an inlet and an outlet; the second feed pump 1-2 is provided with an inlet and an outlet. In the invention, the first material conveying pump 1-1 and the second material conveying pump 1-2 are used for controlling the flow rate of the phthalic anhydride-concentrated sulfuric acid mixed solution and the flow rate of the concentrated nitric acid-salt mixed solution.
The device for preparing nitrophthalic acid provided by the invention comprises a microchannel reactor 2 which is communicated with the first material conveying pump 1-1 and the second material conveying pump 1-2. In the present invention, the microchannel reactor 2 is preferably a silicon carbide microchannel reactor. In the present invention, the microchannel reactor 2 has a microchannel having an inner diameter of preferably 0.5 to 2mm, more preferably 1 to 1.5mm; the shape of the micro-channel preferably includes a heart shape (as shown in fig. 3), a corrugated shape, or a diamond shape, and more preferably a heart shape. In the present invention, the microchannel reactor 2 is provided with a first feed port and a second feed port; the first feeding port is communicated with the outlet of the first material conveying pump 1-1, and the second feeding port is communicated with the outlet of the second material conveying pump 1-2.
In the invention, the micro-channel reactor 2 (shown in fig. 2) is provided with a low temperature zone 2-1 and a high temperature zone 2-2 in sequence according to the flow direction of materials. In the present invention, the number of the micro-channel reaction sheets in the low temperature zone 2-1 is preferably 4 to 6 sheets, more preferably 5 sheets; the liquid holding amount of the single-piece reaction sheet is preferably 8 to 20mL, more preferably 10 to 15mL. In the invention, the low temperature zone 2-1 is provided with a low temperature zone jacket 2-3; the low-temperature area jacket 2-3 is provided with a heat exchange medium inlet and a heat exchange medium outlet; the jacket 2-3 in the low temperature area is filled with heat exchange medium; the type of the heat exchange medium is not particularly limited, and the heat exchange medium known to those skilled in the art, such as simethicone, may be used.
In the present invention, the number of the micro-channel reaction plates in the high temperature zone 2-2 is preferably 4 to 8, more preferably 5 to 6; the liquid holdup of each microchannel reaction plate is independently preferably 8 to 20mL, more preferably 10 to 15mL. In the invention, the high temperature zone 2-2 is provided with a high temperature zone jacket 2-4; the high-temperature area jacket 2-4 is provided with a heat exchange medium inlet and a heat exchange medium outlet; the high-temperature region jacket 2-4 is internally provided with a heat exchange medium; the type of the heat exchange medium is not particularly limited, and the heat exchange medium known to those skilled in the art, such as simethicone, may be used.
In the present invention, the microchannel reactor 2 is preferably further provided with a discharge port.
The device for preparing nitrophthalic acid provided by the invention comprises a double temperature control high-low temperature integrated machine 3 communicated with the low temperature region jacket 2-3 and the high temperature region jacket 2-4. In the invention, the double temperature control high-low temperature integrated machine 3 is preferably provided with a low temperature area heat exchange medium inlet, a low temperature area heat exchange medium outlet, a high temperature area heat exchange medium inlet and a high temperature area heat exchange medium outlet; the low-temperature area heat exchange medium inlet is communicated with the heat exchange medium outlet of the low-temperature area jacket 2-3; the low-temperature area heat exchange medium outlet is communicated with the heat exchange medium inlet of the low-temperature area jacket 2-3; the high-temperature area heat exchange medium inlet is communicated with the heat exchange medium outlet of the high-temperature area jacket 2-4; the high-temperature area heat exchange medium outlet is communicated with the heat exchange medium inlet of the high-temperature area jacket 2-4; the double temperature control high-low temperature integrated machine 3 realizes the control of the temperature of the low temperature region 2-1 and the high temperature region 2-2 of the micro-channel reactor 2 through a heat exchange medium.
In the present invention, the apparatus for producing nitrophthalic acid preferably further comprises a first raw material storage tank 4-1, a second raw material storage tank 4-2, and a product storage tank 5; the first raw material storage box 4-1 is communicated with the first material conveying pump 1-1, the second raw material storage box 4-2 is communicated with the second material conveying pump 1-2, and the product storage box 5 is communicated with a discharge port of the microchannel reactor 2.
The following describes a specific method for preparing nitrophthalic acid by using the apparatus for preparing nitrophthalic acid provided by the present invention with reference to fig. 1, comprising the following steps:
mixing phthalic anhydride and concentrated sulfuric acid to obtain phthalic anhydride-concentrated sulfuric acid mixed solution, and placing the phthalic anhydride-concentrated sulfuric acid mixed solution into a first raw material storage box 4-1;
mixing a water-soluble salt with concentrated nitric acid to obtain concentrated nitric acid-salt mixed solution, and placing the concentrated nitric acid-salt mixed solution in a second raw material storage tank 4-2; the water soluble salt comprises nitrate and/or nitrite;
conveying the phthalic anhydride-concentrated sulfuric acid mixed solution into a microchannel reactor 2 through a first conveying pump 1-1, conveying the concentrated nitric acid-salt mixed solution into the microchannel reactor 2 through a second conveying pump 1-2, performing a pre-nitration reaction in a low temperature zone 2-1, performing a nitration reaction in a high temperature zone 2-2, and outputting the mixture into a product storage box 5 through a discharge hole to obtain nitrophthalic acid; the nitrophthalic acid comprises 3-nitrophthalic acid and 4-nitrophthalic acid; the temperature of the low temperature region 2-1 and the temperature of the high temperature region 2-2 are controlled by the double temperature control high and low temperature integrated machine 3.
The technical solutions of the present invention will be clearly and completely described in the following in connection with the embodiments of the present invention. It will be apparent that the described embodiments are only some, but not all, embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Example 1
4-Nitrophthalic acid and 3-Nitrophthalic acid were prepared using the apparatus shown in FIG. 1.
(1) 50g of phthalic anhydride and 150g of 98wt% concentrated sulfuric acid are mixed for 0.5h at 40 ℃ to obtain a phthalic anhydride-concentrated sulfuric acid mixed solution, and the phthalic anhydride-concentrated sulfuric acid mixed solution is placed in a first raw material storage box 4-1.
(2) 5g of sodium nitrite and 75g of concentrated nitric acid with the concentration of 68wt% are ultrasonically mixed for 0.5h at the temperature of 30 ℃ to obtain a concentrated nitric acid-salt mixed solution, and the concentrated nitric acid-salt mixed solution is placed in a second raw material storage tank 4-2.
(3) The temperature of the low temperature area 2-1 of the micro-channel reactor 2 is controlled to be 55 ℃ by the double temperature control high-low temperature integrated machine 3, and the temperature of the high temperature area 2-2 is controlled to be 95 ℃; controlling the pressure of the low temperature area and the high temperature area to be 0.2MPa through a back pressure valve; the diameter of the central microchannel of the microchannel reactor 2 is 2mm, the number of the microchannel reaction pieces of the low temperature region 2-1 and the high temperature region 2-2 is 5, and the liquid holdup of each microchannel reaction piece is 10mL.
(4) The phthalic anhydride-concentrated sulfuric acid mixed solution is conveyed into a micro-channel reactor 2 through a first conveying pump 1-1 at a flow rate of 3.5mL/min, and meanwhile, the concentrated nitric acid-salt mixed solution is conveyed into the micro-channel reactor 2 through a second conveying pump 1-2 at a flow rate of 1mL/min, the nitration reaction is carried out in a high temperature area 2-2 after the pre-nitration reaction is carried out in a low temperature area 2-1, the total reaction time is 22min, and a mixed nitration product obtained by the nitration reaction is output into a product storage box 5 through a discharge hole. The selectivity of 4-nitrophthalic acid in the detected product liquid is 80%, the selectivity of 3-nitrophthalic acid is 20%, and the conversion rate of phthalic anhydride is 100%.
(5) 150g of pure water is added into the mixed nitration product, and after hydrolysis under stirring, suction filtration is carried out to obtain 60g of mixed acid; adding 240g of water into the mixed acid, heating to 70 ℃, and filtering while the mixed acid is hot to obtain a first solid component and a liquid component;
(6) Adding water which is 3 times that of the first solid component (3-nitrophthalic acid crude product and the content of which is 98%) into the first solid component, heating to 90 ℃ for recrystallization, cooling to 25 ℃, carrying out suction filtration, and drying the obtained second solid product for 10 hours at 110 ℃ to obtain the 3-nitrophthalic acid (10 g, the molar yield is 14.03%, and the purity is 99.5%).
(7) Cooling the liquid component obtained in the step (5) to 5 ℃ for crystallization, carrying out suction filtration, adding water which is 3 times that of the solid component into the obtained solid component (4-nitrophthalic acid crude product, the content of which is 97 percent), heating to 60 ℃ for recrystallization, cooling to 5 ℃ for suction filtration, and drying the obtained solid product at 110 ℃ for 10 hours to obtain the 4-nitrophthalic acid (40 g, the molar yield is 56.11 percent, and the purity is 99.3 percent).
Example 2
3-nitrophthalic acid and 4-nitrophthalic acid were prepared according to the method of example 1, differing from example 1 in that:
in the step (2), sodium nitrite is replaced by sodium nitrate;
the selectivity of 4-nitrophthalic acid in the step (4) is 78%, the selectivity of 3-nitrophthalic acid is 22%, and the conversion rate of phthalic anhydride is 100%;
3-nitrophthalic acid (11 g, molar yield 15.43%, purity 99.4%) was obtained in step (6);
in the step (7), 4-nitrophthalic acid (39 g, molar yield 54.71%, purity 99.2%) was obtained.
Example 3
3-nitrophthalic acid and 4-nitrophthalic acid were prepared according to the method of example 1, differing from example 1 in that:
in the step (2), sodium nitrite is replaced by potassium nitrate;
the selectivity of 4-nitrophthalic acid in the step (4) is 75 percent, the selectivity of 3-nitrophthalic acid is 25 percent, and the conversion rate of phthalic anhydride is 100 percent;
3-nitrophthalic acid (12.5 g, molar yield 17.54%, purity 99.4%) was obtained in step (6);
in the step (7), 4-nitrophthalic acid (37.5 g, molar yield 52.61%, purity 99.3%) was obtained.
Example 4
3-nitrophthalic acid and 4-nitrophthalic acid were prepared according to the method of example 1, differing from example 1 in that:
the mass of the concentrated sulfuric acid in the step (1) is 200g;
the mass of the concentrated nitric acid in the step (2) is 100g;
the temperature of the low temperature area 2-1 in the step (3) is 60 ℃, and the temperature of the high temperature area 2-2 is 100 ℃;
in the step (4), the flow rate of the phthalic anhydride-concentrated sulfuric acid mixed solution is 4mL/min; the selectivity of 4-nitrophthalic acid is 79%, the selectivity of 3-nitrophthalic acid is 21%, and the conversion rate of phthalic anhydride is 100%;
3-nitrophthalic acid (10.5 g, molar yield 14.73%, purity 99.4%) was obtained in step (6);
in the step (7), 4-nitrophthalic acid (39.5 g, molar yield 55.41%, purity 99.5%) was obtained.
Example 5
3-Nitrophthalic acid and 4-Nitrophthalic acid were prepared according to the procedure of example 4, differing from example 1 in that:
in the step (2), sodium nitrite is replaced by potassium nitrate;
the selectivity of 4-nitrophthalic acid in the step (4) is 74 percent, the selectivity of 3-nitrophthalic acid is 26 percent, and the conversion rate of phthalic anhydride is 100 percent;
3-nitrophthalic acid (13 g, 18.24% molar yield, 99.3% purity) was obtained in step (6);
in the step (7), 4-nitrophthalic acid (37 g, molar yield 51.9%, purity 99.3%) was obtained.
Example 6
3-nitrophthalic acid and 4-nitrophthalic acid were prepared according to the method of example 1, differing from example 1 in that:
the mass of sodium nitrite in the step (2) is 4g;
in the step (4), the flow rate of the phthalic anhydride-concentrated sulfuric acid mixed solution is 4mL/min; the selectivity of 4-nitrophthalic acid is 78%, the selectivity of 3-nitrophthalic acid is 22%, and the conversion rate of phthalic anhydride is 100%;
3-nitrophthalic acid (11 g, molar yield 15.43%, purity 99.4%) was obtained in step (6);
in the step (7), 4-nitrophthalic acid (39 g, molar yield 54.71%, purity 99.3%) was obtained.
The foregoing is merely a preferred embodiment of the present invention and it should be noted that modifications and adaptations to those skilled in the art may be made without departing from the principles of the present invention, which are intended to be comprehended within the scope of the present invention.
Claims (7)
1. A method for preparing nitrophthalic acid, which is characterized by comprising the following steps:
mixing phthalic anhydride and concentrated sulfuric acid to obtain phthalic anhydride-concentrated sulfuric acid mixed solution;
mixing the water-soluble salt with concentrated nitric acid to obtain concentrated nitric acid-salt mixed solution; the water soluble salt comprises nitrate and/or nitrite;
introducing the phthalic anhydride-concentrated sulfuric acid mixed solution and the concentrated nitric acid-salt mixed solution into a microchannel reactor to sequentially perform pre-nitration reaction and nitration reaction, wherein the total time of the pre-nitration reaction and the nitration reaction is 17-26 min; the temperature of the pre-nitration reaction is 50-60 ℃, the pressure is 0-0.3 MPa, and the time is 9-13 min; the temperature of the nitration reaction is 90-100 ℃, the pressure is 0-0.3 MPa, and the time is 8-13 min;
hydrolyzing the mixed nitration product to obtain mixed acid;
separating isomers of the mixed acid to obtain 3-nitrophthalic acid and 4-nitrophthalic acid respectively;
the isomer separation includes:
adding water into the mixed acid, mixing, and then carrying out solid-liquid separation to obtain a first solid component and a liquid component;
recrystallizing the first solid component to obtain 3-nitrophthalic acid;
cooling the liquid component, performing solid-liquid separation, and recrystallizing the obtained second solid component to obtain 4-nitrophthalic acid; the temperature after cooling is 0-10 ℃, the solvent for recrystallization is water, and the temperature for recrystallization is 50-80 ℃.
2. The preparation method according to claim 1, wherein the mass ratio of phthalic anhydride to concentrated sulfuric acid is 1:3 to 5;
the concentration of the concentrated sulfuric acid is 95-98wt%.
3. The preparation method according to claim 1, wherein the mass ratio of the concentrated nitric acid to the water-soluble salt is 0.8-3: 0.05 to 0.2;
the concentration of the concentrated nitric acid is 65-68 wt%.
4. The method according to any one of claims 1 to 3, wherein the phthalic anhydride-concentrated sulfuric acid mixture and the concentrated nitric acid-salt mixture are fed at a flow rate ratio of 3 to 5:1.
5. an apparatus for preparing nitrophthalic acid, characterized by comprising a first feed pump (1-1) and a second feed pump (1-2) connected in parallel;
the micro-channel reactor (2) is communicated with the first material conveying pump (1-1) and the second material conveying pump (1-2), and the micro-channel reactor (2) is sequentially provided with a low-temperature area (2-1) and a high-temperature area (2-2) according to the flow direction of materials; the microchannel reactor (2) is provided with a low-temperature region jacket (2-3) and a high-temperature region jacket (2-4), and heat exchange media are arranged in the low-temperature region jacket (2-3) and the high-temperature region jacket (2-4);
and the double temperature control high-low temperature integrated machine (3) is communicated with the low temperature region jacket (2-3) and the high temperature region jacket (2-4).
6. The apparatus according to claim 5, characterized in that the microchannel reactor (2) has microchannels with an inner diameter of 0.5-2 mm.
7. The device according to claim 5, characterized in that the number of reaction plates of the micro-channels of the low temperature zone (2-1) is 4-6; the number of the reaction pieces in the high temperature area (2-1) is 4-8; the liquid holdup of the single-piece reaction piece is independently 8-20 mL.
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| CN1405143A (en) * | 2002-11-04 | 2003-03-26 | 卢宪春 | Method for preparing 3-nitro phthalic acid |
| CN1321972C (en) * | 2005-06-27 | 2007-06-20 | 潘健 | Process of preparing 4-nitro phthalic acid from the reaction mother liquor of nitrating phthalic anhydride to prepare 3-nitro phthalic acid |
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| CN112851516A (en) * | 2019-11-27 | 2021-05-28 | 西华大学 | Method for nitrifying o-xylene by using microchannel reactor |
| CN111153803A (en) * | 2020-02-11 | 2020-05-15 | 浙江聚贤医药科技有限公司 | Method for synthesizing 5-nitroisophthalic acid |
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