CN115611745A - Method for continuously producing 3, 4-dichloronitrobenzene - Google Patents
Method for continuously producing 3, 4-dichloronitrobenzene Download PDFInfo
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- 238000000034 method Methods 0.000 title claims abstract description 54
- NTBYINQTYWZXLH-UHFFFAOYSA-N 1,2-dichloro-4-nitrobenzene Chemical compound [O-][N+](=O)C1=CC=C(Cl)C(Cl)=C1 NTBYINQTYWZXLH-UHFFFAOYSA-N 0.000 title claims abstract description 46
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims abstract description 114
- 239000002253 acid Substances 0.000 claims abstract description 105
- RFFLAFLAYFXFSW-UHFFFAOYSA-N 1,2-dichlorobenzene Chemical compound ClC1=CC=CC=C1Cl RFFLAFLAYFXFSW-UHFFFAOYSA-N 0.000 claims abstract description 102
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 claims abstract description 49
- 229910017604 nitric acid Inorganic materials 0.000 claims abstract description 49
- 238000000605 extraction Methods 0.000 claims abstract description 40
- 239000000047 product Substances 0.000 claims abstract description 37
- 239000002699 waste material Substances 0.000 claims abstract description 35
- 239000000463 material Substances 0.000 claims abstract description 34
- 238000002425 crystallisation Methods 0.000 claims abstract description 20
- 230000008025 crystallization Effects 0.000 claims abstract description 20
- 238000000746 purification Methods 0.000 claims abstract description 11
- 239000007795 chemical reaction product Substances 0.000 claims abstract description 10
- 239000002904 solvent Substances 0.000 claims abstract description 5
- 238000006243 chemical reaction Methods 0.000 claims description 27
- 238000010438 heat treatment Methods 0.000 claims description 19
- 238000002844 melting Methods 0.000 claims description 16
- 230000008018 melting Effects 0.000 claims description 16
- 230000018044 dehydration Effects 0.000 claims description 11
- 238000006297 dehydration reaction Methods 0.000 claims description 11
- 238000007599 discharging Methods 0.000 claims description 9
- 239000007788 liquid Substances 0.000 claims description 8
- 239000000155 melt Substances 0.000 claims description 4
- 230000035484 reaction time Effects 0.000 claims description 4
- 238000001816 cooling Methods 0.000 claims description 3
- 238000010924 continuous production Methods 0.000 abstract description 11
- 238000006396 nitration reaction Methods 0.000 description 18
- 239000000243 solution Substances 0.000 description 16
- 238000003756 stirring Methods 0.000 description 12
- 239000002994 raw material Substances 0.000 description 10
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 10
- 238000002360 preparation method Methods 0.000 description 8
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- 238000004519 manufacturing process Methods 0.000 description 5
- 239000010413 mother solution Substances 0.000 description 4
- CMVQZRLQEOAYSW-UHFFFAOYSA-N 1,2-dichloro-3-nitrobenzene Chemical compound [O-][N+](=O)C1=CC=CC(Cl)=C1Cl CMVQZRLQEOAYSW-UHFFFAOYSA-N 0.000 description 3
- 239000002585 base Substances 0.000 description 3
- 239000012295 chemical reaction liquid Substances 0.000 description 3
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- CCNCITSJXCSXJY-UHFFFAOYSA-N (3,4-dichlorophenyl)thiourea Chemical compound NC(=S)NC1=CC=C(Cl)C(Cl)=C1 CCNCITSJXCSXJY-UHFFFAOYSA-N 0.000 description 1
- PZBPKYOVPCNPJY-UHFFFAOYSA-N 1-[2-(allyloxy)-2-(2,4-dichlorophenyl)ethyl]imidazole Chemical compound ClC1=CC(Cl)=CC=C1C(OCC=C)CN1C=NC=C1 PZBPKYOVPCNPJY-UHFFFAOYSA-N 0.000 description 1
- FECNOIODIVNEKI-UHFFFAOYSA-N 2-[(2-aminobenzoyl)amino]benzoic acid Chemical class NC1=CC=CC=C1C(=O)NC1=CC=CC=C1C(O)=O FECNOIODIVNEKI-UHFFFAOYSA-N 0.000 description 1
- SDYWXFYBZPNOFX-UHFFFAOYSA-N 3,4-dichloroaniline Chemical compound NC1=CC=C(Cl)C(Cl)=C1 SDYWXFYBZPNOFX-UHFFFAOYSA-N 0.000 description 1
- XMTQQYYKAHVGBJ-UHFFFAOYSA-N 3-(3,4-DICHLOROPHENYL)-1,1-DIMETHYLUREA Chemical compound CN(C)C(=O)NC1=CC=C(Cl)C(Cl)=C1 XMTQQYYKAHVGBJ-UHFFFAOYSA-N 0.000 description 1
- QPFHNWRKKQLCMG-UHFFFAOYSA-N 3-[4-[(5,6-dichloro-1,3-benzothiazol-2-yl)diazenyl]-n-ethyl-3-methylanilino]propanenitrile Chemical compound CC1=CC(N(CCC#N)CC)=CC=C1N=NC1=NC2=CC(Cl)=C(Cl)C=C2S1 QPFHNWRKKQLCMG-UHFFFAOYSA-N 0.000 description 1
- XKJMBINCVNINCA-UHFFFAOYSA-N Alfalone Chemical compound CON(C)C(=O)NC1=CC=C(Cl)C(Cl)=C1 XKJMBINCVNINCA-UHFFFAOYSA-N 0.000 description 1
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- 229910002651 NO3 Inorganic materials 0.000 description 1
- NHNBFGGVMKEFGY-UHFFFAOYSA-N Nitrate Chemical compound [O-][N+]([O-])=O NHNBFGGVMKEFGY-UHFFFAOYSA-N 0.000 description 1
- 238000002479 acid--base titration Methods 0.000 description 1
- 230000032683 aging Effects 0.000 description 1
- 239000003513 alkali Substances 0.000 description 1
- SOIFLUNRINLCBN-UHFFFAOYSA-N ammonium thiocyanate Chemical compound [NH4+].[S-]C#N SOIFLUNRINLCBN-UHFFFAOYSA-N 0.000 description 1
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- TUXJTJITXCHUEL-UHFFFAOYSA-N disperse red 11 Chemical compound C1=CC=C2C(=O)C3=C(N)C(OC)=CC(N)=C3C(=O)C2=C1 TUXJTJITXCHUEL-UHFFFAOYSA-N 0.000 description 1
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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
-
- 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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- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
Abstract
The invention provides a method for continuously producing 3, 4-dichloronitrobenzene. The method comprises the following steps: step 1) preparing mixed acid by using a solvent, sulfuric acid and nitric acid; step 2) putting the mixed acid and o-dichlorobenzene into a continuous reactor to obtain a reaction product; step 3) standing and layering the reaction product to obtain a nitrated material layer and a nitrated waste acid layer; step 4) carrying out melt crystallization purification on the nitrified material layer to obtain 3, 4-dichloronitrobenzene; adding o-dichlorobenzene into the nitrified waste acid layer for extraction treatment to obtain an extraction product; step 5) standing and layering the extraction product to obtain an o-dichlorobenzene extraction layer and an acid layer; and 6) concentrating the acid layer to obtain a concentrated product. The continuous production process has the advantages of simple flow, high yield, low risk level and the like compared with an intermittent process, and meanwhile, the whole flow can realize remote control, so that the number of operators and the labor intensity are reduced.
Description
Technical Field
The invention relates to a method for continuously producing 3, 4-dichloronitrobenzene, in particular to a method for continuously producing 3, 4-dichloronitrobenzene by recycling acid, belonging to the field of synthesis of dye intermediates.
Background
3, 4-dichloronitrobenzene is a main raw material for producing 3, 4-dichloroaniline, and the latter is an important intermediate, is mainly used as azo dye on the dye, and can synthesize C.I. disperse red 152 and C.I. disperse red 153; in the aspect of medicine, the compound is used as a synthetic bactericide TCC and the like, and can be mixed with ammonium thiocyanate to prepare 3, 4-dichlorophenyl thiourea; in the pesticide industry, the method is mainly used for synthesizing herbicides such as linuron, diuron, imazalil and the like.
In the prior art, the production method of 3, 4-dichloronitrobenzene mainly uses o-dichlorobenzene as a raw material to carry out nitration reaction with a mixed acid solution consisting of sulfuric acid, nitric acid and water to synthesize the 3, 4-dichloronitrobenzene. Citation 1 provides a device for producing 3, 4-dichloronitrobenzene by continuous tank reaction, which can realize continuous production of 3, 4-dichloronitrobenzene, but does not mention a treatment method of waste acid.
According to the conventional process, after the nitration reaction is finished, 70-80% of sulfuric acid, 1% -3% of nitric acid and organic matters with COD of 5000-8000 ppm are contained in the waste acid. If the waste acid needs to be treated, other waste alkali liquor is generally adopted for neutralization, and salt is recovered after COD is removed through oxidation. The method has high treatment cost and low economic value of the recovered salt.
Therefore, the research on a method for recycling and reusing the waste acid to achieve the purpose of environment-friendly and continuous production of 3, 4-dichloronitrobenzene becomes a technical problem to be solved urgently.
Cited documents:
citation 1: CN105418433A
Disclosure of Invention
Problems to be solved by the invention
In view of the technical problems in the prior art, such as large reaction risk of producing 3, 4-dichloronitrobenzene in a batch mode, quality difference among batches, incapability of recycling waste acid and the like, the invention provides the method for continuously producing 3, 4-dichloronitrobenzene, which can recycle waste acid and meet the requirements of environmental protection and continuous production.
Means for solving the problems
The invention provides a method for continuously producing 3, 4-dichloronitrobenzene, which comprises the following steps:
step 1) preparing mixed acid by using a solvent, sulfuric acid and nitric acid;
step 2) putting the mixed acid and o-dichlorobenzene into a continuous reactor to obtain a reaction product;
step 3) standing and layering the reaction product to obtain a nitrated material layer and a nitrated waste acid layer;
step 4) carrying out melt crystallization purification on the nitrified material layer to obtain 3, 4-dichloronitrobenzene; adding o-dichlorobenzene into the nitrified waste acid layer for extraction treatment to obtain an extraction product;
step 5) standing and layering the extraction product to obtain an o-dichlorobenzene extraction layer and an acid layer;
and 6) concentrating the acid layer to obtain a concentrated product.
The method provided by the invention is characterized in that in the step 1), the molar ratio of sulfuric acid to nitric acid is 0.5-4.
The method of the invention, wherein in the step 1), the dehydration value of the mixed acid is 3.0-4.5.
The method provided by the invention is characterized in that in the step 2), the molar ratio of the nitric acid to the o-dichlorobenzene is 0.8-1.80; and/or the reaction temperature of the step 2) is 50-70 ℃, and the reaction time is 1-2 hours.
According to the method of the present invention, the COD of the nitrification waste acid layer in the step 3) is 7000ppm or less, the sulfuric acid content is 70% or more, and the nitric acid content is 6% or less.
The method of the invention, wherein in the step 4), the melt crystallization purification comprises: and heating and melting the nitrified material layer, cooling and crystallizing, heating to 33-38 ℃, and discharging molten liquid to obtain the 3, 4-dichloronitrobenzene.
The method of the invention is characterized in that the temperature of the extraction treatment is 50-70 ℃, and the time of the extraction treatment is 0.5-1.5 hours.
According to the method of the present invention, the COD of the acid layer is 2800ppm or less, the sulfuric acid content is 70% or more, and the nitric acid content is 1% or less.
The method of the invention, wherein the temperature of the concentration is 180 ℃ to 190 ℃.
According to the method of the present invention, the concentrated product has a COD of 3000ppm or less and a sulfuric acid content of 85% or more.
ADVANTAGEOUS EFFECTS OF INVENTION
1. The continuous production process has the advantages of simple flow, high yield, low risk level and the like compared with an intermittent process, and can realize remote control of the whole flow and reduce the number of operators and labor intensity.
2. The continuous production process realizes the recovery and reuse of the nitrified waste acid. The invention achieves the aim of reducing the dosage of nitric acid while ensuring the purity of the 3, 4-dichloronitrobenzene by adjusting the dehydration value, namely the DVS value. The extraction concentration of the sulfuric acid can also be realized by mechanically applying the sulfuric acid and preparing the mixed acid, so that the utilization rate of the raw materials is improved, and the production cost is reduced.
3. The 3, 4-dichloronitrobenzene produced by the continuous production process solves the problems of large difference between batch of intermittent processes and unstable product performance. The 3, 4-dichloronitrobenzene produced by the continuous production process has stable product quality.
Drawings
FIG. 1 shows a process flow diagram of the continuous production method of 3, 4-dichloronitrobenzene of the invention.
Detailed Description
The present invention will be described in detail below. The technical features described below are explained based on typical embodiments and specific examples of the present invention, but the present invention is not limited to these embodiments and specific examples.
Furthermore, in the following detailed description, numerous specific details are set forth in order to provide a better understanding of the present invention. It will be understood by those skilled in the art that the present invention may be practiced without some of these specific details. In other instances, methods, means, devices and steps which are well known to those skilled in the art have not been described in detail so as not to obscure the invention.
It should be noted that:
in the present specification, the numerical range represented by "numerical value a to numerical value B" means a range including the end points of numerical values a and B. All units used in the invention are international standard units unless otherwise stated, and numerical values and numerical ranges appearing in the invention should be understood to include errors allowed in industrial production.
In the present specification, "%" represents mass% unless otherwise specified.
Reference in the specification to "some specific/preferred embodiments," "other specific/preferred embodiments," "embodiments," and so forth, means that a particular element (e.g., feature, property, and/or characteristic) described in connection with the embodiment is included in at least one embodiment described herein, and may or may not be present in other embodiments. In addition, it is to be understood that the described elements may be combined in any suitable manner in the various embodiments.
The invention provides a method for continuously producing 3, 4-dichloronitrobenzene, which comprises the following steps:
step 1) preparing mixed acid by using a solvent, sulfuric acid and nitric acid;
step 2) putting the mixed acid and o-dichlorobenzene into a continuous reactor to obtain a reaction product;
step 3) standing and layering the reaction product to obtain a nitrated material layer and a nitrated waste acid layer;
step 4) carrying out melting crystallization purification on the nitrified material layer to obtain 3, 4-dichloronitrobenzene; adding o-dichlorobenzene into the nitrified waste acid layer for extraction treatment to obtain an extraction product;
step 5) standing and layering the extraction product to obtain an o-dichlorobenzene extraction layer and an acid layer;
and 6) concentrating the acid layer to obtain a concentrated product.
The continuous production process has the advantages of simple flow, high yield, low risk level and the like compared with an intermittent process, and can realize remote control of the whole flow and reduce the number of operators and labor intensity.
The step 1) of the invention prepares the mixed acid by using solvent, sulfuric acid and nitric acid. In some specific embodiments, in step 1), the molar ratio of sulfuric acid to nitric acid is from 0.5 to 4: 0.5. When the molar ratio of the sulfuric acid to the nitric acid is 0.5 to 4.
In some specific embodiments, in the step 1), the dehydration value of the mixed acid is 3.0 to 4.5, for example: 3.2, 3.5, 3.8, 4, 4.2, etc. The invention achieves the purpose of reducing the dosage of nitric acid while ensuring the purity of the 3, 4-dichloronitrobenzene by adjusting the dehydration value, namely the DVS value. The extraction concentration of the sulfuric acid can also be realized by mechanically applying the sulfuric acid and preparing the mixed acid, so that the utilization rate of the raw materials is improved, and the production cost is reduced.
The invention realizes the continuous production of 3, 4-dichloronitrobenzene by using a continuous reactor. Specifically, the mixed acid and the o-dichlorobenzene can be put into a continuous reactor to obtain a reaction product. The reaction materials can enter an aging kettle after coming out of the reactor, and further react to ensure that the reaction is finished.
The present invention is not particularly limited to a continuous reactor, and may be a continuous reactor commonly used in the art, for example: microchannel reactors, loop reactors, multistage tank reactors, and the like.
In some specific embodiments, in step 2), the molar ratio of nitric acid to ortho-dichlorobenzene is 0.8 to 1.80, for example: 1, 1.2; when the molar ratio of the nitric acid to the o-dichlorobenzene is 0.8-1.80, the reaction is facilitated to be carried out.
Specifically, the reaction temperature of the step 2) is 50 to 70 ℃, for example: 52 ℃, 55 ℃, 58 ℃, 60 ℃, 62 ℃, 65 ℃, 68 ℃ and the like; the reaction time is 1 to 2 hours, 1.2 hours, 1.4 hours, 1.6 hours, 1.8 hours, etc. When the reaction temperature of the step 2) is 50-70 ℃ and the reaction time is 1-2 hours, the reaction is complete.
The step 3) of the invention is to obtain a nitrated material layer and a nitrated waste acid layer by layering the reaction product after standing. The method of layering after standing is not particularly limited, and may be a layering method commonly used in the art. For example: the layering may be performed after standing by a layering column.
Further, the COD of the nitrification waste acid layer in the step 3) is 7000ppm or less, the content of sulfuric acid is 70% or more, and the content of nitric acid is 6% or less. Therefore, the COD value in the nitrified waste acid is greatly reduced, and the nitrified waste acid can be used for subsequent treatment.
Step 4) of the invention is to carry out melting crystallization purification on the nitrified material layer to obtain 3, 4-dichloronitrobenzene; adding o-dichlorobenzene into the nitrified waste acid layer for extraction treatment to obtain an extraction product; after the acid layer is extracted, the nitric acid in the acid layer reacts with o-dichlorobenzene to generate 3, 4-dichloronitrobenzene.
In some specific embodiments, in step 4), the melt crystallization purification comprises: and heating and melting the nitrified material layer, cooling and crystallizing, heating to 33-38 ℃, and discharging molten liquid to obtain the 3, 4-dichloronitrobenzene.
Specifically, the melt crystallization purification is based on the difference between the melting points of 3, 4-dichloronitrobenzene (melting point 43 ℃) and 2, 3-dichloronitrobenzene (melting point 63 ℃), the nitrate material layers of the two materials are heated and melted in advance, and then the obtained molten product is placed in a crystallization separation tube, so that the temperature of the molten product is reduced until the molten product is crystallized and solidified to obtain a crystallized product; and then slowly heating the crystallized product to 33-38 ℃, wherein part of solid is melted and flows out, and the content of the 2, 3-dichloronitrobenzene in the flowing-out solution is higher than that of the 2, 3-dichloronitrobenzene in the original solution, so that the purity of the 3, 4-dichloronitrobenzene in the residual crystals is improved, and the aim of purification is fulfilled. The inventor finds that the 3, 4-dichloronitrobenzene with high purity can be obtained after the nitration material layer is subjected to melt crystallization and purification.
Further, in the present invention, the nitrating material layer may be raised to a temperature above 55 ℃, for example: melting the nitride material layer at 57 deg.C, 59 deg.C, 61 deg.C, 63 deg.C, etc. to obtain molten product; the molten product is then cooled to below 32 ℃, for example: crystallizing and solidifying the molten product at 31 deg.C, 30 deg.C, 29 deg.C, 28 deg.C, 27 deg.C, 26 deg.C, etc. to obtain crystallized product; finally, the temperature of the crystallized product is raised to 33 ℃ to 38 ℃, for example: melting and flowing out part of the solid at 34 ℃, 35 ℃, 36 ℃, 37 ℃ and the like, and obtaining the residual crystal, namely the 3, 4-dichloronitrobenzene with higher purity.
Specifically, the temperature of the extraction treatment is 50 to 70 ℃, for example: 52 ℃, 55 ℃, 58 ℃, 60 ℃, 62 ℃, 65 ℃, 68 ℃ and the like; the time of the extraction treatment is 0.5 to 1.5 hours, 0.7 hours, 0.9 hours, 1.1 hours, 1.3 hours and the like. When the temperature of the extraction treatment is 50-70 ℃, and the time of the extraction treatment is 0.5-1.5 hours, the extraction can be completed.
Step 5) standing and layering the extraction product to obtain an o-dichlorobenzene extraction layer and an acid layer; the mode of layering after standing is not particularly limited in the present invention, and may be a layering mode commonly used in the art. The acid layer has a COD of 2800ppm or less, a sulfuric acid content of 70% or more, and a nitric acid content of 1% or less. Therefore, after the acid layer is frequently extracted, the COD value of the acid layer is greatly reduced, and the COD value does not influence the recycling of the acid layer even after the acid layer is concentrated.
Step 6) of the present invention is to obtain a concentrated product by concentrating the acid layer. The invention can obtain the sulfuric acid with the required concentration by concentration, and can be used for preparing the mixed acid in the step 1).
In some specific embodiments, the temperature of the concentration is from 180 ℃ to 190 ℃, for example: 182 ℃, 185 ℃, 188 ℃ and the like.
Further, the concentrated product has a COD of 3000ppm or less and a sulfuric acid content of 85% or more, for example: 85-95%, etc. And the COD value of the concentrated product does not influence the recycling of the concentrated product. When the content of the sulfuric acid is more than 85%, the preparation of mixed acid is facilitated. Further, when the COD of the concentrated product is 3000ppm or less, the preparation of the mixed acid is not affected.
Examples
Embodiments of the present invention will be described in detail below with reference to examples, but those skilled in the art will appreciate that the following examples are only illustrative of the present invention and should not be construed as limiting the scope of the present invention. The examples, in which specific conditions are not specified, were carried out according to conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are conventional products which are commercially available or prepared conventionally, and manufacturers are not indicated.
In the embodiment, the purity is detected by HPLC;
detecting the content of sulfuric acid and the content of nitric acid by an acid-base titration method;
COD was detected according to HJ 828-2107.
Example 1
To a 10L reactor, 1056g of water was added. Stirring was turned on, and 8000g of 98% sulfuric acid and 3428g of 98% nitric acid (molar ratio of sulfuric acid to nitric acid was about 1.5. The temperature in the whole preparation process does not exceed 40 ℃, and the dehydration value of the mixed acid solution is 3.5. If mixed acid solution is needed to be supplemented in the continuous reaction process, the mixed acid solution can be prepared according to the proportion.
The continuous nitration device is a loop reactor, the effective volume is 1000ml, and a jacket can provide cold and heat sources. 800ml of crude 3, 4-dichloronitrobenzene is added in advance in a loop reactor as a base material, and then stirring and a jacket heat source are started, and the temperature is controlled to be 55-60 ℃.
After the temperature is stabilized, a raw material feeding pump is started, the feeding speed of the o-dichlorobenzene is 400ml/h, and the feeding speed of the mixed acid is 600ml/h. At this feed rate, the molar ratio of nitric acid to o-dichlorobenzene was 1.2. The residence time of the reaction mass in the loop reactor was 1 hour. And (3) overflowing the reaction liquid into a layering column through an outlet, standing and layering at 60 ℃ to obtain a nitrated material layer and a nitrated waste acid layer. The overflow was sampled every 1 hour for detection. The results are shown in Table 1.
After the reaction is finished, heating the nitrated material layer collected by the layering column to 60 ℃ until the nitrated material layer is completely melted, putting the nitrated material layer into a melting crystallization separation column, carrying out heat preservation crystallization for 3 hours at 28 ℃, then starting heating at the heating speed of 2 ℃/h to 33 ℃, discharging the melted liquid from the bottom of the column, heating the residual mother liquid in the crystallization separation column to 60 ℃ to melt, and discharging the melted mother liquid to obtain the purified 3, 4-dichloronitrobenzene. The purity of the purified 3, 4-dichloronitrobenzene is 98.25 percent.
Analyzing the nitration waste acid layer, wherein the content of sulfuric acid is 76.34%; the content of nitric acid is 1.56%; the COD was 5460ppm. Transferring the nitrified waste acid layer into a 15L reaction kettle, adding orthodichlorobenzene with the same volume, and stirring for 1 hour at the temperature of 55-60 ℃. After the reaction is finished, the mixture is kept warm and kept stand for layering, the upper layer is an o-dichlorobenzene extraction layer, and the lower layer is an acid layer. And (3) separating the o-dichlorobenzene extraction layer from the acid layer, and directly using the o-dichlorobenzene extraction layer as a raw material for the nitration reaction of the next batch.
Analyzing an acid layer, wherein the content of sulfuric acid is 75.30%; the content of nitric acid is 0.33%; the COD was 1984ppm. Vacuum concentrating the acid layer at 187 deg.C under-0.095-0.1 Mpa until no condensed water flows out to obtain concentrated product. Analyzing the concentrated acid liquor to obtain 92.35 percent of sulfuric acid; nitric acid was not detected; COD was 2381ppm.
TABLE 1
Note: "- -" indicates "not detected".
As can be seen from table 1, the 3, 4-dichloronitrobenzene obtained by the method has higher purity and low COD value of the wastewater, and the finally obtained acid layer can be recycled for production.
Example 2
Example 2 is a test in which the recovered sulfuric acid and o-dichlorobenzene obtained in example 1 were mechanically used.
In a 10L reactor, 727g of water was added, stirring was turned on, and then 4000g of recovered sulfuric acid and 4243g of sulfuric acid having a content of 98% and 3428g of nitric acid having a content of 98% were slowly poured (molar ratio of sulfuric acid to nitric acid was about 1.5. The temperature in the whole preparation process does not exceed 40 ℃, and the dehydration value of the mixed acid solution is 3.5.
The conditions for continuous nitration were the same as in example 1, with o-dichlorobenzene recovered in example 1 being used and with additional fresh o-dichlorobenzene if the amount was insufficient. The results of the nitration sampling and the waste acid concentration data are shown in Table 2.
TABLE 2
Note: "- -" indicates "not detected".
As can be seen from Table 2, the results of example 1 were reproduced by the nitration reaction of recovered sulfuric acid and o-dichlorobenzene, which demonstrates that the process has good reproducibility and long-term recycling.
Example 3
In a 10L reactor, 770g of water was added. Stirring was turned on, and 8000g of 98% sulfuric acid and 3428g of 98% nitric acid (molar ratio of sulfuric acid to nitric acid was about 1.5. The temperature in the whole preparation process does not exceed 40 ℃, and the dehydration value of the mixed acid solution is 4.0. If the mixed acid solution is needed to be supplemented in the continuous reaction process, the mixed acid solution can be prepared according to the proportion.
The continuous nitrification device is a loop reactor, the effective volume is 1000ml, and the continuous nitrification device is provided with a jacket to provide a cold and heat source. 800ml of crude 3, 4-dichloronitrobenzene is added in advance in a loop reactor as a base material, and then stirring and a jacket heat source are started, and the temperature is controlled to be 55-60 ℃.
After the temperature is stabilized, the raw material feeding pump is started, the feeding speed of the o-dichlorobenzene is 440ml/h, and the feeding speed of the mixed acid is 560ml/h. At this feed rate, the molar ratio of nitric acid to ortho-dichlorobenzene was 1.05. The residence time of the reaction mass in the loop reactor was 1 hour. And (3) overflowing the reaction liquid into a layering column through an outlet, standing and layering at 60 ℃ to obtain a nitrated material layer and a nitrated waste acid layer. The overflow was sampled every 1 hour for detection. The results are shown in Table 3.
After the reaction is finished, heating a nitrated material layer collected by a layering column to 60 ℃ until the nitrated material layer is completely melted, putting the nitrated material layer into a melting crystallization separation column, carrying out heat preservation crystallization for 3 hours at 28 ℃, then starting heating at the heating speed of 2 ℃/h to 33 ℃, discharging melted liquid from the bottom of the column, heating the residual mother solution in the crystallization separation column to 60 ℃ for melting, and discharging the melted mother solution to obtain the purified 3, 4-dichloronitrobenzene. The purity of the purified 3, 4-dichloronitrobenzene is 98.12 percent.
Analyzing the nitrified waste acid layer, wherein the content of sulfuric acid is 78.1%; the content of nitric acid is 0.82%; COD was 6430ppm. Transferring the nitrified waste acid layer into a 15L reaction kettle, adding orthodichlorobenzene with the same volume, and stirring for 1 hour at the temperature of 55-60 ℃. After the reaction is finished, the mixture is kept warm and kept stand for layering, the upper layer is an o-dichlorobenzene extraction layer, and the lower layer is an acid layer. And (3) separating the o-dichlorobenzene extraction layer from the acid layer, and directly using the o-dichlorobenzene extraction layer as a raw material for the nitration reaction of the next batch.
The acid layer is analyzed, and the content of sulfuric acid is 77.30 percent; the content of nitric acid is 0.39%; COD was 2354ppm. Vacuum-pumping and concentrating the acid layer at 187 deg.C to-0.095-0.1 Mpa until no condensed water flows out to obtain concentrated product. Analyzing the concentrated acid liquor to reach sulfuric acid content of 91.35%; nitric acid was not detected; the COD was 2543ppm.
TABLE 3
Note: "- -" indicates "not detected".
As can be seen from Table 3, the 3, 4-dichloronitrobenzene obtained by the method has higher purity and low COD value of the wastewater, and the finally obtained acid layer can be recycled for production.
Example 4
Example 4 is an experiment for mechanically applying the recovered sulfuric acid and o-dichlorobenzene obtained in example 3.
In a 10L reactor, 400g of water was added, stirring was turned on, and then 4000g of recovered sulfuric acid and 4300g of 98% sulfuric acid and 3428g of 98% nitric acid were slowly poured (molar ratio of sulfuric acid to nitric acid was about 1.5. The temperature in the whole preparation process does not exceed 40 ℃, and the dehydration value of the mixed acid solution is 4.0.
The conditions for the continuous nitration reaction were the same as in example 3, and the o-dichlorobenzene used in the reaction was recovered from example 3. If the amount is insufficient, adding fresh o-dichlorobenzene. The results of the nitration sampling and the waste acid concentration data are shown in Table 4.
TABLE 4
Note: "- -" indicates "not detected".
As can be seen from Table 4, the results of example 3 were reproduced by conducting the nitration reaction on the recovered sulfuric acid and o-dichlorobenzene, and it was confirmed that the process had good reproducibility and could be recycled for a long period of time.
Example 5
To a 10L reactor, 1056g of water was added. Stirring was turned on, and 8000g of 98% sulfuric acid and 3428g of 98% nitric acid (molar ratio of sulfuric acid to nitric acid was about 1.5. The temperature in the whole preparation process does not exceed 40 ℃, and the dehydration value of the mixed acid solution is 3.5. If the mixed acid solution is needed to be supplemented in the continuous reaction process, the mixed acid solution can be prepared according to the proportion.
The continuous nitration device is a loop reactor, the effective volume is 1000ml, and a jacket can provide cold and heat sources. 800ml of crude 3, 4-dichloronitrobenzene is added in advance in a loop reactor as a base material, and then stirring and a jacket heat source are started, and the temperature is controlled to be 55-60 ℃.
After the temperature is stabilized, the raw material feeding pump is started, the feeding speed of the o-dichlorobenzene is 380ml/h, and the feeding speed of the mixed acid is 620ml/h. At this feed rate, the molar ratio of nitric acid to ortho-dichlorobenzene was 1.3. The residence time of the reaction mass in the loop reactor was 1 hour. And (3) overflowing the reaction liquid into a layering column through an outlet, standing and layering at 60 ℃ to obtain a nitrated material layer and a nitrated waste acid layer. The overflow was sampled every 1 hour for detection. The results are shown in Table 5.
After the reaction is finished, heating a nitrated material layer collected by a layering column to 60 ℃ until the nitrated material layer is completely melted, putting the nitrated material layer into a melting crystallization separation column, carrying out heat preservation crystallization for 3 hours at 28 ℃, then starting heating at the heating speed of 2 ℃/h to 33 ℃, discharging melted liquid from the bottom of the column, heating the residual mother solution in the crystallization separation column to 60 ℃ for melting, and discharging the melted mother solution to obtain the purified 3, 4-dichloronitrobenzene. The purity of the purified 3, 4-dichloronitrobenzene is 98.48 percent.
Analyzing the nitrified waste acid layer, wherein the content of sulfuric acid is 78.88%; the content of nitric acid is 3.56%; the COD was 5493ppm. Transferring the nitrified waste acid layer into a 15L reaction kettle, adding orthodichlorobenzene with the same volume, and stirring for 1 hour at the temperature of 55-60 ℃. After the reaction is finished, the mixture is kept at the temperature and is kept stand for layering, the upper layer is an o-dichlorobenzene extraction layer, and the lower layer is an acid layer. And (3) separating the o-dichlorobenzene extraction layer from the acid layer, and directly using the o-dichlorobenzene extraction layer as a raw material for the nitration reaction of the next batch.
Analyzing an acid layer, wherein the content of sulfuric acid is 75.30%; the content of nitric acid is 0.33%; the COD was 1984ppm. Vacuum concentrating the acid layer at 187 deg.C under-0.095-0.1 Mpa until no condensed water flows out to obtain concentrated product. Analyzing the concentrated acid liquor to obtain 92.73 percent of sulfuric acid; nitric acid was not detected; COD was 2389ppm.
TABLE 5
Note: "- -" indicates "not detected".
Example 6
Example 6 is a test in which the recovered sulfuric acid and o-dichlorobenzene obtained in example 5 were mechanically used.
In a 10L reactor 765g water was added, stirring was turned on, then 4000g recovered sulfuric acid and 4215g sulfuric acid with a 98% content and 3428g nitric acid with a 98% content were slowly poured in (the molar ratio of sulfuric acid to nitric acid was about 1.5. The temperature in the whole preparation process does not exceed 40 ℃, and the dehydration value of the mixed acid solution is 3.5.
The conditions for the continuous nitration reaction were the same as in example 5, and the o-dichlorobenzene used in the reaction was recovered in example 5. If the amount is insufficient, adding fresh o-dichlorobenzene. The results of the nitration sampling and the waste acid concentration data are shown in Table 6.
TABLE 6
Note: "- -" indicates "not detected".
As can be seen from Table 6, the results of example 5 were reproduced by the nitration reaction of recovered sulfuric acid and o-dichlorobenzene, which demonstrates that the process has good reproducibility and long-term recycling.
It should be noted that, although the technical solutions of the present invention are described by specific examples, those skilled in the art can understand that the present invention should not be limited thereto.
Having described embodiments of the present invention, the foregoing description is intended to be exemplary, not exhaustive, and not limited to the embodiments disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments.
Claims (10)
1. A method for continuously producing 3, 4-dichloronitrobenzene is characterized by comprising the following steps:
step 1) preparing mixed acid by using a solvent, sulfuric acid and nitric acid;
step 2) putting the mixed acid and o-dichlorobenzene into a continuous reactor to obtain a reaction product;
step 3) standing and layering the reaction product to obtain a nitrated material layer and a nitrated waste acid layer;
step 4) carrying out melting crystallization purification on the nitrified material layer to obtain 3, 4-dichloronitrobenzene; adding o-dichlorobenzene into the nitrified waste acid layer for extraction treatment to obtain an extraction product;
step 5) standing and layering the extraction product to obtain an o-dichlorobenzene extraction layer and an acid layer;
and 6) concentrating the acid layer to obtain a concentrated product.
2. The method according to claim 1, wherein in the step 1), the molar ratio of sulfuric acid to nitric acid is 0.5-4.
3. The method according to claim 1 or 2, wherein the dehydration number of the mixed acid in the step 1) is 3.0 to 4.5.
4. The method according to any one of claims 1 to 3, wherein in step 2), the molar ratio of nitric acid to ortho-dichlorobenzene is 0.8-1.80; and/or the reaction temperature of the step 2) is 50-70 ℃, and the reaction time is 1-2 hours.
5. The method according to any one of claims 1 to 4, wherein the COD of the nitrification waste acid layer in the step 3) is 7000ppm or less, the content of sulfuric acid is 70% or more, and the content of nitric acid is 6% or less.
6. The method according to any one of claims 1 to 5, wherein in the step 4), the melt crystallization purification comprises: and heating and melting the nitrified material layer, cooling and crystallizing, heating to 33-38 ℃, and discharging molten liquid to obtain the 3, 4-dichloronitrobenzene.
7. The method according to any one of claims 1 to 6, wherein the temperature of the extraction treatment is 50 to 70 ℃ and the time of the extraction treatment is 0.5 to 1.5 hours.
8. The method according to any one of claims 1 to 7, wherein the COD of the acid layer is 2800ppm or less, the sulfuric acid content is 70% or more, and the nitric acid content is 1% or less.
9. The method according to any one of claims 1 to 8, wherein the temperature of the concentration is 180 ℃ to 190 ℃.
10. The method according to any one of claims 1 to 9, wherein the concentrated product has a COD of 3000ppm or less and a sulfuric acid content of 85% or more.
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| CN117945916A (en) * | 2024-01-26 | 2024-04-30 | 乐平市景顺实业有限公司 | Process for preparing 3, 4-dichloronitrobenzene by sulfur trioxide nitration |
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