CN116283745A - Method for preparing 2,3, 6-trichloropyridine and co-producing trichloroacetyl chloride from 3-chloropyridine - Google Patents
Method for preparing 2,3, 6-trichloropyridine and co-producing trichloroacetyl chloride from 3-chloropyridine Download PDFInfo
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- CN116283745A CN116283745A CN202211740160.0A CN202211740160A CN116283745A CN 116283745 A CN116283745 A CN 116283745A CN 202211740160 A CN202211740160 A CN 202211740160A CN 116283745 A CN116283745 A CN 116283745A
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- trichloroacetyl chloride
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- GPAKJVMKNDXBHH-UHFFFAOYSA-N 2,3,6-trichloropyridine Chemical compound ClC1=CC=C(Cl)C(Cl)=N1 GPAKJVMKNDXBHH-UHFFFAOYSA-N 0.000 title claims abstract description 65
- PVFOMCVHYWHZJE-UHFFFAOYSA-N trichloroacetyl chloride Chemical compound ClC(=O)C(Cl)(Cl)Cl PVFOMCVHYWHZJE-UHFFFAOYSA-N 0.000 title claims abstract description 61
- PWRBCZZQRRPXAB-UHFFFAOYSA-N 3-chloropyridine Chemical compound ClC1=CC=CN=C1 PWRBCZZQRRPXAB-UHFFFAOYSA-N 0.000 title claims abstract description 38
- 238000000034 method Methods 0.000 title claims abstract description 22
- 238000005660 chlorination reaction Methods 0.000 claims abstract description 46
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 42
- 239000002994 raw material Substances 0.000 claims abstract description 34
- 238000006243 chemical reaction Methods 0.000 claims abstract description 33
- 239000012071 phase Substances 0.000 claims abstract description 28
- 239000012074 organic phase Substances 0.000 claims abstract description 21
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 claims abstract description 17
- 239000000460 chlorine Substances 0.000 claims abstract description 17
- 229910052801 chlorine Inorganic materials 0.000 claims abstract description 17
- 230000002194 synthesizing effect Effects 0.000 claims abstract description 14
- 239000000203 mixture Substances 0.000 claims abstract description 4
- QTBSBXVTEAMEQO-UHFFFAOYSA-N Acetic acid Chemical compound CC(O)=O QTBSBXVTEAMEQO-UHFFFAOYSA-N 0.000 claims description 52
- 229960000583 acetic acid Drugs 0.000 claims description 26
- 239000012362 glacial acetic acid Substances 0.000 claims description 26
- 238000004821 distillation Methods 0.000 claims description 22
- JXTHNDFMNIQAHM-UHFFFAOYSA-N dichloroacetic acid Chemical compound OC(=O)C(Cl)Cl JXTHNDFMNIQAHM-UHFFFAOYSA-N 0.000 claims description 16
- 230000018044 dehydration Effects 0.000 claims description 11
- 238000006297 dehydration reaction Methods 0.000 claims description 11
- FOCAUTSVDIKZOP-UHFFFAOYSA-N chloroacetic acid Chemical compound OC(=O)CCl FOCAUTSVDIKZOP-UHFFFAOYSA-N 0.000 claims description 10
- 229940106681 chloroacetic acid Drugs 0.000 claims description 10
- 229960005215 dichloroacetic acid Drugs 0.000 claims description 8
- 230000008016 vaporization Effects 0.000 claims description 8
- 238000009834 vaporization Methods 0.000 claims description 7
- 239000000047 product Substances 0.000 abstract description 53
- 238000004519 manufacturing process Methods 0.000 abstract description 25
- 239000006227 byproduct Substances 0.000 abstract description 16
- 238000002474 experimental method Methods 0.000 abstract description 15
- 239000002699 waste material Substances 0.000 abstract description 7
- 239000002351 wastewater Substances 0.000 abstract description 6
- 230000008901 benefit Effects 0.000 abstract description 5
- 238000003786 synthesis reaction Methods 0.000 abstract description 5
- 238000004065 wastewater treatment Methods 0.000 abstract description 4
- 238000002156 mixing Methods 0.000 abstract description 3
- 230000000052 comparative effect Effects 0.000 description 17
- 239000000463 material Substances 0.000 description 13
- 230000009286 beneficial effect Effects 0.000 description 9
- 230000000694 effects Effects 0.000 description 9
- KZBUYRJDOAKODT-UHFFFAOYSA-N Chlorine Chemical compound ClCl KZBUYRJDOAKODT-UHFFFAOYSA-N 0.000 description 6
- DLOOKZXVYJHDIY-UHFFFAOYSA-N 2,3,4,5-tetrachloropyridine Chemical compound ClC1=CN=C(Cl)C(Cl)=C1Cl DLOOKZXVYJHDIY-UHFFFAOYSA-N 0.000 description 5
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 4
- 239000007788 liquid Substances 0.000 description 4
- 238000005406 washing Methods 0.000 description 4
- 230000015572 biosynthetic process Effects 0.000 description 3
- 239000003054 catalyst Substances 0.000 description 3
- 238000010924 continuous production Methods 0.000 description 3
- 238000010438 heat treatment Methods 0.000 description 3
- 230000001105 regulatory effect Effects 0.000 description 3
- 238000000926 separation method Methods 0.000 description 3
- 239000000758 substrate Substances 0.000 description 3
- 230000003247 decreasing effect Effects 0.000 description 2
- 238000007599 discharging Methods 0.000 description 2
- 229940079593 drug Drugs 0.000 description 2
- 239000003814 drug Substances 0.000 description 2
- 238000005265 energy consumption Methods 0.000 description 2
- 239000012847 fine chemical Substances 0.000 description 2
- 238000010574 gas phase reaction Methods 0.000 description 2
- 239000012535 impurity Substances 0.000 description 2
- 238000002360 preparation method Methods 0.000 description 2
- 230000002035 prolonged effect Effects 0.000 description 2
- 230000036632 reaction speed Effects 0.000 description 2
- 230000035484 reaction time Effects 0.000 description 2
- DNDPLEAVNVOOQZ-UHFFFAOYSA-N 2,3,4,5,6-pentachloropyridine Chemical compound ClC1=NC(Cl)=C(Cl)C(Cl)=C1Cl DNDPLEAVNVOOQZ-UHFFFAOYSA-N 0.000 description 1
- MAKFMOSBBNKPMS-UHFFFAOYSA-N 2,3-dichloropyridine Chemical compound ClC1=CC=CN=C1Cl MAKFMOSBBNKPMS-UHFFFAOYSA-N 0.000 description 1
- FILKGCRCWDMBKA-UHFFFAOYSA-N 2,6-dichloropyridine Chemical compound ClC1=CC=CC(Cl)=N1 FILKGCRCWDMBKA-UHFFFAOYSA-N 0.000 description 1
- WPGHPGAUFIJVJF-UHFFFAOYSA-N 3,5-dichloropyridine Chemical compound ClC1=CN=CC(Cl)=C1 WPGHPGAUFIJVJF-UHFFFAOYSA-N 0.000 description 1
- XJFIKRXIJXAJGH-UHFFFAOYSA-N 5-chloro-1,3-dihydroimidazo[4,5-b]pyridin-2-one Chemical group ClC1=CC=C2NC(=O)NC2=N1 XJFIKRXIJXAJGH-UHFFFAOYSA-N 0.000 description 1
- 239000005886 Chlorantraniliprole Substances 0.000 description 1
- 239000005944 Chlorpyrifos Substances 0.000 description 1
- 239000005945 Chlorpyrifos-methyl Substances 0.000 description 1
- 239000003513 alkali Substances 0.000 description 1
- 239000008346 aqueous phase Substances 0.000 description 1
- 239000012295 chemical reaction liquid Substances 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- PSOVNZZNOMJUBI-UHFFFAOYSA-N chlorantraniliprole Chemical compound CNC(=O)C1=CC(Cl)=CC(C)=C1NC(=O)C1=CC(Br)=NN1C1=NC=CC=C1Cl PSOVNZZNOMJUBI-UHFFFAOYSA-N 0.000 description 1
- SBPBAQFWLVIOKP-UHFFFAOYSA-N chlorpyrifos Chemical compound CCOP(=S)(OCC)OC1=NC(Cl)=C(Cl)C=C1Cl SBPBAQFWLVIOKP-UHFFFAOYSA-N 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 230000002708 enhancing effect Effects 0.000 description 1
- 239000004009 herbicide Substances 0.000 description 1
- 239000000543 intermediate Substances 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000003472 neutralizing effect Effects 0.000 description 1
- 238000010979 pH adjustment Methods 0.000 description 1
- 239000000575 pesticide Substances 0.000 description 1
- 230000001699 photocatalysis Effects 0.000 description 1
- 238000007146 photocatalysis Methods 0.000 description 1
- 238000005086 pumping Methods 0.000 description 1
- 230000009257 reactivity Effects 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 238000003756 stirring Methods 0.000 description 1
- 238000012546 transfer Methods 0.000 description 1
- YNJBWRMUSHSURL-UHFFFAOYSA-N trichloroacetic acid Chemical compound OC(=O)C(Cl)(Cl)Cl YNJBWRMUSHSURL-UHFFFAOYSA-N 0.000 description 1
- 229960004319 trichloroacetic acid Drugs 0.000 description 1
- 239000006200 vaporizer Substances 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07D—HETEROCYCLIC COMPOUNDS
- C07D213/00—Heterocyclic compounds containing six-membered rings, not condensed with other rings, with one nitrogen atom as the only ring hetero atom and three or more double bonds between ring members or between ring members and non-ring members
- C07D213/02—Heterocyclic compounds containing six-membered rings, not condensed with other rings, with one nitrogen atom as the only ring hetero atom and three or more double bonds between ring members or between ring members and non-ring members having three double bonds between ring members or between ring members and non-ring members
- C07D213/04—Heterocyclic compounds containing six-membered rings, not condensed with other rings, with one nitrogen atom as the only ring hetero atom and three or more double bonds between ring members or between ring members and non-ring members having three double bonds between ring members or between ring members and non-ring members having no bond between the ring nitrogen atom and a non-ring member or having only hydrogen or carbon atoms directly attached to the ring nitrogen atom
- C07D213/60—Heterocyclic compounds containing six-membered rings, not condensed with other rings, with one nitrogen atom as the only ring hetero atom and three or more double bonds between ring members or between ring members and non-ring members having three double bonds between ring members or between ring members and non-ring members having no bond between the ring nitrogen atom and a non-ring member or having only hydrogen or carbon atoms directly attached to the ring nitrogen atom with hetero atoms or with carbon atoms having three bonds to hetero atoms with at the most one bond to halogen, e.g. ester or nitrile radicals, directly attached to ring carbon atoms
- C07D213/61—Halogen atoms or nitro radicals
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C51/00—Preparation of carboxylic acids or their salts, halides or anhydrides
- C07C51/58—Preparation of carboxylic acid halides
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Engineering & Computer Science (AREA)
- Oil, Petroleum & Natural Gas (AREA)
- Pyridine Compounds (AREA)
Abstract
The invention relates to the technical field of fine chemistry organic synthesis, and discloses a method for preparing 2,3, 6-trichloropyridine and co-producing trichloroacetyl chloride by using 3-chloropyridine, which comprises the steps of (one) chlorination reaction, mixing raw materials of 3-chloropyridine and chlorine, carrying out chlorination reaction, and adding water into the mixture after the reaction is completed to obtain an upper water phase and a lower organic phase; (II) separating 2,3, 6-trichloropyridine, and distilling the lower organic phase to obtain 2,3, 6-trichloropyridine; and thirdly, synthesizing trichloroacetyl chloride, dehydrating an upper water phase, then carrying out chlorination reaction for a plurality of times, and rectifying to obtain the trichloroacetyl chloride. The scheme uses the upper water phase containing byproducts generated during the production of the 2,3, 6-trichloropyridine for synthesizing trichloroacetyl chloride, effectively avoids the waste of raw materials due to the discharge of the byproducts along with the wastewater, and can also effectively reduce the wastewater treatment cost, thereby improving the production benefit. The applicant experiment shows that the yield of the 2,3, 6-trichloropyridine produced by the scheme is higher than 93.8%, and the product purity is higher than 98.1%; the yield of the trichloroacetyl chloride product is 93.8%, and the purity of the trichloroacetyl chloride product is higher than 99%.
Description
Technical Field
The invention relates to the technical field of fine chemical organic synthesis, in particular to a method for preparing 2,3, 6-trichloropyridine and co-producing trichloroacetyl chloride by using 3-chloropyridine.
Background
2,3, 6-trichloropyridine and trichloroacetyl chloride are used as important fine chemical intermediates, and are mainly used for synthesizing medicines such as medicines and pesticides; wherein, 2,3, 6-trichloropyridine is often used as a raw material to produce 2, 3-dichloropyridine, 3, 5-dichloropyridine, chlorantraniliprole and the like; trichloroacetyl chloride is commonly used for synthesizing chlorpyrifos, chlorpyrifos methyl, herbicides and the like. With the continuous development of society, the demand of 2,3, 6-trichloropyridine and trichloroacetyl chloride is gradually increased year by year.
In order to solve the problems, the prior art CN109529891A discloses a supported catalyst, a preparation method thereof and a preparation method of 2,3, 6-trichloropyridine, wherein the supported Fe/Cu/Al/C catalyst is adopted to catalyze 2, 6-dichloropyridine to react with chlorine to synthesize 2,3, 6-trichloropyridine; however, the reaction not only needs a special catalyst, but also has long reaction time (100 h of reaction), high substrate conversion rate (about 98%), low product yield (more than 90%), more byproducts and more waste water discharge, so that raw materials are wasted, and the production cost is obviously increased. In the synthesis of the trichloroacetyl chloride commonly used at present, chloroacetic acid, dichloroacetic acid and trichloroacetic acid are commonly used to obtain trichloroacetyl chloride through a chloridechlorination reaction, however, the yield of the product after the reaction is lower.
In summary, the existing production processes of 2,3, 6-trichloropyridine and trichloroacetyl chloride are all independent production, so that the production equipment and the management cost are increased, the product yield is low, more byproducts are discharged along with wastewater, more raw materials are wasted, and the production benefit is low. Therefore, the scheme develops a method for preparing 2,3, 6-trichloropyridine and co-producing trichloroacetyl chloride by using 3-chloropyridine, which not only effectively makes up the defect of independent production of the existing 2,3, 6-trichloropyridine and trichloroacetyl chloride, but also effectively improves the utilization rate of byproducts and reduces the waste of substrates and the wastewater treatment cost; has important significance for the production of 2,3, 6-trichloropyridine and trichloroacetyl chloride and subsequent products.
Disclosure of Invention
The invention aims to provide a method for preparing 2,3, 6-trichloropyridine and co-producing trichloroacetyl chloride by using 3-chloropyridine, so as to solve the technical problem that byproducts waste raw materials along with wastewater discharge in the existing method for synthesizing 2,3, 6-trichloropyridine.
In order to achieve the above purpose, the invention adopts the following technical scheme: a method for preparing 2,3, 6-trichloropyridine and co-producing trichloroacetyl chloride by using 3-chloropyridine comprises the following steps:
firstly, a chlorination reaction is carried out, after 3-chloropyridine and chlorine serving as raw materials are mixed, the chlorination reaction is carried out, and water is added into the mixture after the reaction is finished to obtain an upper water phase and a lower organic phase;
(II) separating 2,3, 6-trichloropyridine, and distilling the lower organic phase to obtain 2,3, 6-trichloropyridine;
and (III) synthesizing trichloroacetyl chloride, dehydrating an upper water phase, performing primary chlorination, secondary chlorination and tertiary chlorination reaction, and rectifying to obtain trichloroacetyl chloride.
The principle and the advantages of the scheme are as follows:
1. compared with the prior art that the by-products produced in the production of 2,3, 6-trichloropyridine waste raw materials along with the discharge of wastewater, the scheme uses the upper water phase containing the by-products produced in the production of 2,3, 6-trichloropyridine for synthesizing trichloroacetyl chloride, effectively avoids the waste of the raw materials along with the discharge of wastewater, and can also effectively reduce the wastewater treatment cost, thereby improving the production benefit. The applicant experiment shows that the yield of the 2,3, 6-trichloropyridine produced by the scheme is higher than 93.8%, and the product purity is higher than 98.1%; the yield of the trichloroacetyl chloride product is 93.8%, and the purity of the trichloroacetyl chloride product is higher than 99%; remarkably improves the yield and purity of the product.
2. Compared with the prior art that the equipment cost is higher when two products are produced independently, the scheme adopts a continuous production mode to co-produce 2,3, 6-trichloropyridine and trichloroacetyl chloride, so that the production process is simple, the product yield is high, other byproducts are avoided, and the product production efficiency is effectively improved. The applicant experiment shows that 50KG of 3-chloropyridine is put into production in each batch, and 502KG of the product (wherein 76KG of 2,3, 6-trichloropyridine and 426KG of trichloroacetyl chloride) can be produced. In addition, the reaction residence time in the continuous production of the scheme is short, the tar is less generated, the efficiency is high, and the cost is low.
Preferably, in the (mono) chlorination reaction, the raw materials further comprise glacial acetic acid, the raw materials 3-chloropyridine and the glacial acetic acid are fed in a vaporization state to form a mixed gas phase, and chlorine is introduced into the mixed gas phase to complete the chlorination reaction.
The beneficial effects are that: the scheme adopts the vaporized raw materials for feeding and mixing reaction, has high raw material mass transfer efficiency, effectively shortens the reaction process and improves the product synthesis efficiency. The applicant experiment shows that the reaction time of the vaporization raw material is far less than that of the liquid raw material, and the vaporization raw material is more uniformly mixed and has strong activity, so that the gas phase photocatalysis efficiency is higher.
Preferably, the mass ratio of the 3-chloropyridine, the chlorine and the glacial acetic acid in the raw materials is 1:6-7:3.
The beneficial effects are that: the applicant experiment shows that the reaction effect is best, the conversion rate of 3-chloropyridine is more than 97%, and the conversion rate of glacial acetic acid is more than 93%. The applicant experiment finds that when glacial acetic acid is less, the chlorination reaction can generate more tar and waste raw materials; when more glacial acetic acid and chlorine are used, the heating energy consumption is increased, and the energy-saving production is not facilitated; and the selectivity of the byproduct tetrachloropyridine is increased when the chlorine is more, so that the product yield is reduced.
Preferably: the feeding pressure of the raw materials 3-chloropyridine and glacial acetic acid is 120-150 kPa.
The beneficial effects are that: applicants have found that feeding at this pressure, the materials can be thoroughly mixed in the tubular reactor, thereby enhancing the vaporization reactivity.
Preferably, the chlorination reaction conditions are 230-250 ℃.
The beneficial effects are that: the applicant experiment shows that the reaction speed is the fastest when the chlorination reaction temperature is 230-250 ℃, and the conversion rate of 3-chloropyridine and glacial acetic acid is the highest; when the reaction temperature is too low, the reaction speed is low, so that the reaction is not thorough; and when the reaction temperature is too high, by-products tetrachloropyridine and pentachloropyridine are generated, and meanwhile, more tar is produced, so that the product yield is reduced.
Preferably, the water is required to be condensed to 90-100 ℃ before layering; the water consumption of the water adding layering is 1.5 times.
The beneficial effects are that: the applicant experiment finds that the layering effect is best when the temperature is reduced to 90-100 ℃ before the layering is performed. If the temperature is too low, the 2,3, 6-trichloropyridine is easy to crystallize, so that the layering effect is poor; if the temperature is too high, the vaporization is serious when water is added, and the material is easily taken away by steam, so that the material loss is large. In addition, the applicant experiment finds that the washing effect is best by 1.5 times, if the water is too much, the wastewater treatment cost is increased, if the water is too little, chloroacetic acid cannot be thoroughly washed, and the purity of 2,3,6 trichloropyridine is reduced due to the residual chloroacetic acid in an organic phase, so that the product quality is affected.
Preferably, the lower organic phase is further subjected to pH adjustment to 7-8 before distillation; the distillation temperature of the lower organic phase is 210-220 ℃, and the distillation steam obtained by distillation is the 2,3, 6-trichloropyridine.
The beneficial effects are that: the applicant experiment finds that when the pH value of the lower organic phase is regulated to 7-8, the material is neutralized from a salified state with hydrochloric acid to a free state, so that the distillation separation is facilitated, and the distillation effect is effectively improved; and at pH 7-8, the corrosion of the organic relative equipment is minimal. In addition, the applicant experiment finds that 2,3, 6-trichloropyridine with purity higher than 98.5% can be obtained by distillation at the distillation temperature; and when the temperature is too high (such as the temperature is over 230 ℃), the materials in the organic phase are easy to produce tar at high temperature, so that the yield of products is reduced, and the production benefit is reduced.
Preferably, the components after the upper water phase dehydration comprise 88-92% chloroacetic acid, 5-8% dichloroacetic acid and 2-5% glacial acetic acid; the upper water phase dehydration is distillation dehydration under the condition of 95-102 ℃.
The beneficial effects are that: in the scheme, the conversion rate of glacial acetic acid is higher than 93%, and most (more than 99%) of the residual glacial acetic acid and byproducts (chloroacetic acid and dichloroacetic acid) generated by the reaction are in an upper water phase after being subjected to water washing and layering, so that the subsequent production of trichloroacetyl chloride is facilitated. In addition, the applicant experiment finds that the dehydration speed is the fastest at 95-102 ℃, and meanwhile, fewer products are carried out, so that the loss of the products can be effectively avoided; however, when the temperature of the distillation dehydration exceeds 105 ℃, the material carried along with the water vapor is obviously increased.
Preferably, the primary chlorination and the secondary chlorination are reacted for 15-20 hours at the temperature of 120-140 ℃, and the tertiary chlorination is reacted for 15-20 hours at the temperature of 105-110 ℃.
The beneficial effects are that: the applicant experiment finds that the primary chlorination reaction and the secondary chlorination reaction are carried out under the conditions, so that trichloroacetyl chloride can be obtained through effective reaction, and the yield of the product can be improved.
Preferably, the rectification temperature is 110-115 ℃.
The beneficial effects are that: the applicant experiment shows that the rectification effect is best at 110-115 ℃, and the content of the extracted finished product is more than 99%. The rectification speed is low when the temperature is too low; when the temperature is too high, the impurity content of the produced finished product is high, and more tar is produced, so that the product yield is reduced.
Detailed Description
The following is a detailed description of embodiments, but embodiments of the invention are not limited thereto. The technical means used in the following examples are conventional means well known to those skilled in the art unless otherwise indicated; the experimental methods used are all conventional methods; the materials, reagents, and the like used are all commercially available. A method for preparing 2,3, 6-trichloropyridine and co-producing trichloroacetyl chloride by using 3-chloropyridine is shown in a specific embodiment.
Example 1
A method for preparing 2,3, 6-trichloropyridine and co-producing trichloroacetyl chloride by using 3-chloropyridine comprises the following steps: firstly, a chlorination reaction is carried out, namely, raw materials 3-chloropyridine and chlorine are mixed for carrying out the chlorination reaction, and water is added into the mixture to obtain an upper water phase and a lower organic phase; (II) separating 2,3, 6-trichloropyridine, and distilling the lower organic phase to obtain 2,3, 6-trichloropyridine; and (III) synthesizing trichloroacetyl chloride, dehydrating an upper water phase, performing primary chlorination, secondary chlorination and tertiary chlorination reaction, and rectifying to obtain the trichloroacetyl chloride.
The method specifically comprises the following steps:
(mono) chlorination reaction
S1, vaporizing and mixing raw materials of 3-chloropyridine and glacial acetic acid, preheating a tubular reactor with the diameter of 0.3 meter and the diameter of 25-30 meters to 180 ℃, pumping the raw materials into a vaporizer by using a pump respectively with 50KG 3-chloropyridine per hour and 150KG glacial acetic acid per hour (the mass ratio of the 3-chloropyridine to the glacial acetic acid is 1:3 in the scheme), and simultaneously introducing the vaporized 3-chloropyridine and the glacial acetic acid into the tubular reactor in a positive pressure state (120-150 kPa in the scheme, 130kPa in the embodiment) to form a mixed gas phase; the positive pressure feeding is convenient for the materials to be fully mixed in the tubular reactor, thereby improving the vaporization reaction activity.
S2: introducing chlorine gas and carrying out chlorination reaction, regulating a chlorine gas regulating valve to ensure that the chlorine gas is continuously introduced into a tubular reactor at a flow rate of 300-350 kg (in the scheme) per hour, and carrying out continuous and stable gas phase reaction (specifically chlorination reaction) at 230-250 ℃ after the chlorine gas is mixed with mixed gas phase; in this stage, only part of chlorine is consumed in the chlorine reaction, and the residual chlorine can be recycled.
In the scheme, the chlorination reaction is carried out in the tubular reactor, and continuous positive pressure feeding and continuous micro negative pressure (15 kPa) discharging are carried out simultaneously, and the residence time of materials in the tubular reactor is only a few seconds. If the reaction temperature is increased or the feed rate is decreased (the residence time of the materials in the tubular reactor is prolonged), the reaction produces by-products such as tetrachloropyridine or tar, which results in a decrease in the yield of the product.
S3: condensing, adding water for layering, continuously discharging after the gas phase reaction is finished, cooling the gas phase to 90-100 ℃ through a condenser, continuously adding water which is 1.5 times of the volume of condensate liquid under the stirring state, and continuously washing and separating liquid to obtain an upper water phase and a lower organic phase. Wherein the upper layer water phase comprises 88% -92% chloroacetic acid, 5% -8% dichloroacetic acid and 2% -5% glacial acetic acid; the lower organic phase is mainly 2,3, 6-trichloropyridine.
(II) separation of 2,3, 6-trichloropyridine
S4: washing the lower organic phase twice, neutralizing the pH of the organic phase to 7-8 by using liquid alkali, and distilling at the temperature of 210-220 ℃ to obtain the 2,3,6 trichloropyridine finished product with the purity higher than 98.5%.
Examples 2 to 8, comparative examples 1 to 4 differ from the examples in that different combination parameter conditions are used to produce 2,3, 6-trichloropyridine; specifically, examples 2 to 8 show the production of 2,3, 6-trichloropyridine using parameter combinations within the scope of the present solution; comparative examples 1 to 4 show the production of 2,3, 6-trichloropyridine using parameter combinations outside the scope of the present protocol; the parameters and the differences between the production of 2,3, 6-trichloropyridine in examples 1 to 8 and comparative examples 1 to 4 are shown in Table 1.
TABLE 1 variation in parameters and results for the production of 2,3, 6-trichloropyridine in examples 1 to 8 and comparative examples 1 to 4
Experimental data show that the raw materials are vaporized, so that the raw material conversion rate and the product yield are effectively improved, the yield of the obtained 2,3, 6-trichloropyridine product is higher than 93.8%, and the purity is higher than 98.1%.
In addition, the scheme effectively improves the product yield by optimizing the raw material ratio. Specifically, when glacial acetic acid is small, more tar is generated in the chlorination reaction, and raw materials are wasted, for example, the yield is 82.1% and the purity is 97% in comparative example 3; when more glacial acetic acid and chlorine are used, the heating energy consumption is increased, and the energy-saving production is not facilitated; and the selectivity of the by-product tetrachloropyridine is increased when the chlorine is more, so that the product yield is reduced, such as 87.3% in comparative example 2, and the purity is 94.1%. And when chlorine is less, the conversion of 3-chloropyridine is reduced, resulting in a reduction in the yield of the product, such as 96.5% for comparative example 3, and less than 97.8% for example 1.
Second, if the chlorination reaction temperature is increased or the feed rate is decreased (the residence time of the material in the tubular reactor is prolonged), the reaction may produce by-products such as tetrachloropyridine or tar, resulting in a decrease in the yield of the product. As in comparative example 1, the substrate conversion was 99.2% at a higher reaction temperature (260 ℃ C.) was selected, however, the yield of 2,3, 6-trichloropyridine obtained by the reaction was only 85.6%, resulting in a large waste of raw materials as by-products.
Then, the scheme remarkably improves the purity of the 2,3, 6-trichloropyridine product by optimizing the distillation temperature. Specifically, the purity of 2,3, 6-trichloropyridine in comparative example 6 is significantly lower than that of examples and other comparative examples, and is mainly characterized in that more water is distilled out along with the product at the distillation temperature, thereby reducing the purity of the product.
Finally, the pH value of the lower organic phase is adjusted before distillation, so that the product 2,3, 6-trichloropyridine is separated from water for distillation separation, and the purity of the product 2,3, 6-trichloropyridine is obviously improved. Specifically, the product 2,3, 6-trichloropyridine was obtained in a significantly reduced yield (82.5%) by distillation at too low a solution pH as in comparative example 4, because the 2,3, 6-trichloropyridine moiety was salified with hydrochloric acid and was not easily separated from the solution by distillation, thereby reducing the product yield.
Example 9
(III) synthesizing trichloroacetyl chloride
S5: heating an upper water phase (comprising 88% -92% of chloroacetic acid, 5% -8% of dichloroacetic acid and 2% -5% of glacial acetic acid, wherein the content of chloroacetic acid is 88%, 8% of dichloroacetic acid, 2% of glacial acetic acid and 2% of water) to 95-102 ℃ for distillation dehydration, introducing chlorine gas to react for 15-20 h at 120-140 ℃ (specifically primary chlorination and secondary chlorination), continuously introducing chlorine gas to react for 15-20 h at 105-110 ℃ (specifically tertiary chlorination), and rectifying the obtained reaction liquid at 110-115 ℃ to obtain a 99% trichloroacetyl chloride finished product.
The upper aqueous phase obtained in the above-described different example 1 was used for the synthesis of trichloroacetyl chloride in examples 10 to 14, comparative examples 5 to 6 and example 9, except that: examples 10 to 14 and comparative examples 5 to 6 show different conditions for synthesizing trichloroacetyl chloride. The differences in conditions for synthesizing trichloroacetyl chloride in examples 9 to 14 and comparative examples 5 to 6 and the results of the product yields and purities are shown in Table 2.
TABLE 2 conditions for synthesizing trichloroacetyl chloride in examples 9 to 14 and comparative examples 5 to 6 differ and results of yield and purity of the product
Experimental data show that the method for synthesizing trichloroacetyl chloride in the scheme is applicable to upper water phases with different component concentrations, and the yield of the obtained trichloroacetyl chloride is higher than 93.8%, and the purity is higher than 99%.
According to the scheme, the purity of the trichloroacetyl chloride product is obviously improved by optimizing the dehydration conditions. Specifically, the purity of trichloroacetyl chloride in comparative example 5 is obviously lower than that of examples 9-14, and the main characteristic is that under the dehydration condition, the materials carried along with water vapor are obviously increased, the content of the materials in the water phase after dehydration is reduced, and the product yield is reduced.
According to the scheme, the trichloroacetyl chloride is synthesized by optimizing the reaction conditions of primary chlorination, secondary chlorination and tertiary chlorination, so that the raw material components chloroacetic acid, dichloroacetic acid and glacial acetic acid are facilitated, and the yield of the trichloroacetyl chloride product is obviously improved. The yields of the products obtained in the production of trichloroacetyl chloride in the embodiment 9 to 14 are all higher than 93.8 percent.
According to the scheme, the purity of the trichloroacetyl chloride product is obviously improved by optimizing the rectification temperature. Specifically, the purity of trichloroacetyl chloride in comparative example 6 is significantly lower than that of examples 9-14, mainly because at this rectification temperature, more impurities will distill with the product, and at this temperature, part of the product is easily converted into tar, thereby reducing the product yield.
In the scheme, the production raw material 3-chloropyridine 50KG is put into each batch, and 502KG products (2, 3, 6-trichloropyridine 76KG and trichloroacetyl chloride 426 KG) can be produced. In addition, the reaction residence time in the continuous production of the scheme is short, the tar is less generated, the efficiency is high, and the cost is low.
The foregoing is merely exemplary of the present invention, and specific technical solutions and/or features that are well known in the art have not been described in detail herein. It should be noted that, for those skilled in the art, several variations and modifications can be made without departing from the technical solution of the present invention, and these should also be regarded as the protection scope of the present invention, which does not affect the effect of the implementation of the present invention and the practical applicability of the patent. The protection scope of the present application shall be subject to the content of the claims, and the description of the specific embodiments and the like in the specification can be used for explaining the content of the claims.
Claims (10)
1. A method for preparing 2,3, 6-trichloropyridine and co-producing trichloroacetyl chloride by using 3-chloropyridine is characterized by comprising the following steps: comprising
Firstly, a chlorination reaction is carried out, after 3-chloropyridine and chlorine serving as raw materials are mixed, the chlorination reaction is carried out, and water is added into the mixture after the reaction is finished to obtain an upper water phase and a lower organic phase;
(II) separating 2,3, 6-trichloropyridine, and distilling the lower organic phase to obtain 2,3, 6-trichloropyridine;
and (III) synthesizing trichloroacetyl chloride, dehydrating an upper water phase, performing primary chlorination, secondary chlorination and tertiary chlorination reaction, and rectifying to obtain trichloroacetyl chloride.
2. The method for preparing 2,3, 6-trichloropyridine and co-producing trichloroacetyl chloride from 3-chloropyridine according to claim 1, which is characterized in that: in the chlorination reaction, the raw materials further comprise glacial acetic acid, the raw materials 3-chloropyridine and the glacial acetic acid are fed in a vaporization state to form a mixed gas phase, and chlorine is introduced into the mixed gas phase to complete the chlorination reaction.
3. The method for preparing 2,3, 6-trichloropyridine and co-producing trichloroacetyl chloride from 3-chloropyridine according to claim 2, which is characterized in that: the mass ratio of the 3-chloropyridine, the chlorine and the glacial acetic acid in the raw materials is 1:6-7:3.
4. A method for preparing 2,3, 6-trichloropyridine and co-producing trichloroacetyl chloride by using 3-chloropyridine according to claim 3, which is characterized in that: the feeding pressure of the raw materials 3-chloropyridine and glacial acetic acid is 120-150 kPa.
5. The method for preparing 2,3, 6-trichloropyridine and co-producing trichloroacetyl chloride by using 3-chloropyridine according to claim 4, which is characterized in that: the chlorination reaction condition is 230-250 ℃.
6. The method for preparing 2,3, 6-trichloropyridine and co-producing trichloroacetyl chloride by using 3-chloropyridine according to claim 5, which is characterized in that: before the water is added and layered, the water is required to be condensed to 90-100 ℃; the water consumption of the water adding layering is 1.5 times.
7. The method for preparing 2,3, 6-trichloropyridine and co-producing trichloroacetyl chloride from 3-chloropyridine according to claim 6, which is characterized in that: the pH of the lower organic phase is adjusted to 7-8 before the distillation of the lower organic phase; the distillation temperature of the lower organic phase is 210-220 ℃, and the distillation steam obtained by distillation is the 2,3, 6-trichloropyridine.
8. The method for preparing 2,3, 6-trichloropyridine and co-producing trichloroacetyl chloride from 3-chloropyridine according to claim 7, which is characterized in that: the upper water phase comprises 88% -92% of chloroacetic acid, 5% -8% of dichloroacetic acid and 2% -5% of glacial acetic acid; the upper water phase dehydration is distillation dehydration under the condition of 95-102 ℃.
9. The method for preparing 2,3, 6-trichloropyridine and co-producing trichloroacetyl chloride from 3-chloropyridine according to claim 8, which is characterized in that: the primary chlorination and the secondary chlorination are reacted for 15-20 hours at the temperature of 120-140 ℃, and the tertiary chlorination is reacted for 15-20 hours at the temperature of 105-110 ℃.
10. The method for preparing 2,3, 6-trichloropyridine and co-producing trichloroacetyl chloride by using 3-chloropyridine according to claim 9, which is characterized in that: the rectification temperature is 110-115 ℃.
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