Preparation method and system of quinclorac

Abstract

The present application relates to a preparation method and a preparation system of quinclorac, and belongs to the technical field of herbicide preparation. AuPd alloy nanoparticles are loaded on a lanthanum-doped CsPMo composite carrier to construct a "Lewis acid site + electron-rich metal active center" synergistic system. Lanthanum ions are embedded in the Keggin structure gap of CsPMo through ionic bonds or coordination bonds. This not only significantly improves the specific surface area of the composite carrier, but also strengthens the number of Lewis acid sites. The electronic metal-composite carrier interaction between AuPd alloy and the composite carrier induces the transfer of electrons from the carrier to the alloy, forming an electron-rich active center. This reduces the activation energy barrier of oxygen and efficiently generates oxygen ion active oxygen species. At the same time, it accelerates the dissociation of hydrogen into active hydrogen species, providing sufficient active species for oxidation and reduction reactions, respectively, and ensuring the efficient promotion of the methylation of 1-chloro-2-methyl-3-nitrobenzene, the reduction of the nitro group, and the subsequent ring-closing reaction.

Description

Technical Field

[0001] This invention belongs to the field of pesticide synthesis technology, and relates to a method and system for preparing dichloroquinoline acid. Background Technology

[0002] In agricultural production, quinclorac acid, as a highly effective selective herbicide for rice paddies, plays a crucial role in ensuring rice yield due to its high efficiency in controlling barnyard grass and its safety in rice. It achieves its weed-control effect by interfering with the metabolism of weed growth hormones, and is suitable for different growth stages of rice and is easy to use. Traditional preparation methods typically use 3-chloro-2-methylaniline and glycerol as raw materials, synthesized through three steps: condensation, chlorination, and oxidation. The condensation stage requires specific temperatures and catalysts to construct intermediates, the chlorination step introduces the target chlorine atom, and the oxidation step often uses mixed acids to achieve functional group transformation.

[0003] Chinese invention patent application CN115385855B discloses a two-step oxidation method for preparing dichloroquinoline acid, comprising the following steps: cyclizing 3-chloro-2-methylaniline with glycerol to obtain 7-chloro-8-methylquinoline; chlorinating 7-chloro-8-methylquinoline to obtain 3,7-dichloro-8-chloromethylquinoline, which is then mixed with sulfuric acid to form an oxide preparation solution; catalytic oxidation and hydrolysis of the oxide preparation solution, followed by solid-liquid separation, dissolving the solid phase in a solvent, and adding an oxidant to oxidize and obtain dichloroquinoline acid. This method avoids the generation of large amounts of waste acid and wastewater in the oxidation synthesis process and allows for solvent recovery and reuse.

[0004] The oxidation step in the above scheme uses a mixture of sulfuric acid and oxides to prepare a solution and add an oxidant dropwise. After the reaction, it needs to be neutralized with alkali, which will produce a large amount of sodium sulfate wastewater. In addition, hydrogen peroxide and sulfuric acid are easily mixed to generate peroxysulfuric acid, which poses an explosion risk. Furthermore, the oxidation process can easily lead to the opening of the quinoline ring, resulting in high reaction risk and a high proportion of byproducts. Summary of the Invention

[0005] The purpose of this invention is to provide a method and system for preparing dichloroquinoline acid. By loading gold alloy nanoparticles onto a supported catalyst and having them participate in methyl oxidation and nitro reduction reactions as catalysts, the invention achieves the beneficial effects of improving product purity and catalyst reusability.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] A method for preparing dichloroquinoline acid includes the following steps:

[0008] Step 1: A lanthanum-doped precursor was synthesized using phosphomolybdic acid, lanthanum nitrate hexahydrate, and cesium carbonate as raw materials. After calcination, a composite support was obtained. Then, a supported catalyst loaded with palladium alloy nanoparticles was prepared by coprecipitation-gas phase reduction method.

[0009] Step 2: 1-Chloro-2-methyl-3-nitrobenzene undergoes a free radical oxidation reaction in the presence of oxygen, N-hydroxyphthalimide, azobisisobutyronitrile, and a supported catalyst, followed by a reduction reaction and a cyclization reaction to obtain 7-chloro-8-quinoline carboxylic acid, which is then chlorinated to obtain dichloroquinoline acid.

[0010] Furthermore, the preparation process of the composite carrier is as follows:

[0011] Yellow phosphomolybdic acid powder, lanthanum nitrate hexahydrate, and deionized water were added to a carrier preparation reactor and mixed evenly. A cesium carbonate solution with a concentration of 19.0-19.5 g / L was then added dropwise to the carrier preparation reactor. After the addition was complete, the mixture was stirred for 2-3 hours, aged for 2-3 hours, centrifuged, washed, and the precipitate was collected, dried, and placed in a calcination apparatus. The temperature was raised to 300-320℃ and calcined for 1-2 hours to obtain the composite carrier.

[0012] Furthermore, the ratio of yellow phosphomolybdic acid powder, lanthanum nitrate hexahydrate, deionized water, and cesium carbonate solution is 934-1000g: 10-15g: 8.5-10.5L: 12.8-15.8L.

[0013] Furthermore, the preparation process of the supported catalyst is as follows:

[0014] The composite support and deionized water were added to the catalyst preparation reactor, followed by the addition of urea. The mixture was refluxed at 90-100℃ for 20-30 min, and then a noble metal salt solution was added. The mixture was stirred at 90-100℃ and 500-700 r / min for 1-2 h. After cooling to room temperature, the catalyst was centrifuged, washed, and dried at 60-65℃ for 12-14 h. Finally, the catalyst was reduced in a mixed atmosphere of hydrogen and argon at 120-150℃ for 2-3 h to obtain the supported catalyst.

[0015] Furthermore, the ratio of the amount of composite carrier, deionized water, urea and precious metal salt solution is 50-70g: 5-6L: 11.34-17.34g: 30.95-40.95mL.

[0016] Furthermore, the precious metal salt solution includes one or a mixture of sodium chloropalladium solution and tetrachloroauric acid solution.

[0017] Furthermore, the preparation process of 7-chloro-8-quinoline carboxylic acid is as follows:

[0018] 1-Chloro-2-methyl-3-nitrobenzene, N-hydroxyphthalimide, a mixed solvent of acetic acid and methanol, azobisisobutyronitrile, and a supported catalyst were sequentially added to an integrated reactor. After replacing the air with nitrogen, oxygen was introduced until the pressure inside the reactor reached 1.8 MPa, and the temperature was raised to 140-150℃. The reaction was carried out for 5-6 hours. After the reaction was completed, the temperature was lowered to 80-85℃, and nitrogen was introduced to replace the oxygen. Then, hydrogen was introduced until the pressure inside the reactor reached 2.2 MPa, and the reaction was carried out at 80-100℃ for 3-4 hours. After cooling to room temperature, the supported catalyst and solvent were recovered. Toluene and trifluoroacetic acid were then added, and the temperature was raised to 80-85℃. Acrolein was added dropwise, and the reaction was maintained at 90-100℃ for 4-5 hours. After the reaction was completed, the solution was neutralized to pH 6.8 with 5 wt% sodium bicarbonate. The solution was filtered, purified, and dried to obtain 7-chloro-8-quinoline carboxylic acid.

[0019] Furthermore, the ratio of 1-chloro-2-methyl-3-nitrobenzene, N-hydroxyphthalimide, a mixture of acetic acid and methanol, azobisisobutyronitrile, supported catalyst, toluene, trifluoroacetic acid, and acrolein is 1-1.5 kg: 53-63 g: 5-6 L: 5-6 g: 20-30 g: 5.25-6.25 L: 53-63 g: 345-365 g.

[0020] A preparation system used in a method for preparing dichloroquinoline acid includes a support preparation reactor, a catalyst preparation reactor, an integrated reactor, and a chlorination reactor.

[0021] A calcination device is connected between the carrier preparation reactor and the catalyst preparation reactor.

[0022] The catalyst preparation reactor is connected to the integrated reactor by a reduction device.

[0023] A filter, a multi-component distillation column, a recrystallization column one, a chlorination reactor, and a crystallization column two are connected sequentially between the integrated reactor and the chlorination reactor.

[0024] Furthermore, a catalyst recovery pipeline is connected between the filter and the integrated reactor.

[0025] Furthermore, a solvent recovery pipeline connects the multi-component distillation column and the integrated reactor.

[0026] The beneficial effects of this invention are:

[0027] 1. This invention involves loading AuPd alloy nanoparticles onto a lanthanum-doped CsPMo composite support to construct a synergistic system of "Lewis acid sites + electron-rich metal active centers." Lanthanum ions are embedded in the Keggin structure gaps of CsPMo through ionic or coordinate bonds, which not only significantly increases the specific surface area of ​​the composite support but also enhances the number of Lewis acid sites. The electron-metal-composite-support interaction between the AuPd alloy and the composite support induces electron transfer from the support to the alloy, forming electron-rich active centers. This lowers the oxygen activation energy barrier, efficiently generating oxygen ion active oxygen species, and simultaneously accelerates the dissociation of hydrogen into active hydrogen species. This provides sufficient active species for both oxidation and reduction reactions, ensuring the efficient advancement of methyl oxidation, nitro reduction, and subsequent ring-closing reactions of 1-chloro-2-methyl-3-nitrobenzene. It also suppresses the generation of side reactions such as polychlorination, improves the conversion rate and purity of dichloroquinoline acid, and reduces reaction time costs.

[0028] 2. The abundant bridging oxygen and terminal oxygen sites on the surface of the composite carrier of this invention form stable coordination bonds with the AuPd alloy, effectively preventing the migration and aggregation of metal particles. This not only increases the contact area between the supported catalyst and oxygen and hydrogen, but also maintains a high conversion rate after multiple cycles, improving the utilization rate of precious metals and reducing catalyst replacement costs. In addition, the methyl oxidation, nitro reduction, and condensation ring closure are integrated into an integrated reactor. By precisely controlling the reaction conditions, the reaction proceeds efficiently, eliminating losses during material transfer at the source. The preparation system is equipped with a catalyst recovery pipeline and a multi-component distillation column. The supported catalyst retained by the filter can be directly returned to the integrated reactor for reuse. The multi-component distillation column can achieve efficient separation and recovery of solvents such as acetic acid and methanol, reducing solvent consumption costs and shortening the production cycle.

[0029] 3. This invention optimizes the reaction system from the source by replacing the mixed acid and heavy metal oxidants in the traditional process with clean oxidant oxygen and reducing agent hydrogen. This completely solves the problem of huge waste acid and wastewater discharge in the traditional process. The chlorination reaction strictly controls the chlorine gas introduction rate and precisely matches the electrophilic substitution reaction requirements at the 3-position of the quinoline ring. Combined with the alkaline absorption tower for efficient treatment of tail gas, the process does not use any highly toxic reagents, reducing the environmental impact and making it more environmentally friendly. Attached Figure Description

[0030] Figure 1 This is a process flow diagram of the preparation system for dichloroquinoline acid according to the present invention;

[0031] Reference numerals in the attached diagram: 1. Feed inlet; 2. Carrier preparation reactor; 3. Calcination device; 4. Catalyst preparation reactor; 5. Reduction device; 6. Hydrogen feed pipe; 7. Nitrogen feed pipe; 8. Oxygen feed pipe; 9. Integrated reactor; 10. Filter; 11. Multi-component distillation column; 12. Chlorine feed pipe; 13. Recrystallization column one; 14. Chlorination reactor; 15. Recrystallization column two; 16. Flow meter; 17. Solvent recovery pipe; 18. Catalyst recovery pipe; 19. Product storage tank; 20. Tail gas treatment pipe; 21. Alkali absorption tower. Detailed Implementation

[0032] To further illustrate the technical means and effects of the present invention in achieving the intended purpose, the following detailed description of the specific implementation methods, features and effects of the present invention, in conjunction with preferred embodiments, is provided below.

[0033] Example 1: This example provides a preparation system for dichloroquinoline acid. Please refer to [link / reference]. Figure 1 As shown, it includes a carrier preparation reactor 2, a catalyst preparation reactor 4, an integrated reactor 9, and a chlorination reactor 14.

[0034] A calcination device 3 is connected between the support preparation reactor 2 and the catalyst preparation reactor 4. The calcination device 3 is used for the calcination preparation of the composite support. A reduction device 5 is connected between the catalyst preparation reactor 4 and the integrated reactor 9. The reduction device 5 is used to reduce palladium and gold ions in the supported catalyst to metallic palladium and gold. The integrated reactor 9 is connected to a hydrogen feed pipe 6, a nitrogen feed pipe 7, and an oxygen feed pipe 8, each equipped with a flow meter 16. The hydrogen feed pipe 6 is also connected to the reduction device 5 to provide the hydrogen required for reduction. A filter 10, a multi-component distillation column 11, and a recrystallization column 13 are connected sequentially between the integrated reactor 9 and the chlorination reactor 14. The filter 10 filters out the supported catalyst and passes it through a catalyst recovery pipe. The solvent components are distilled out by the multi-component distillation column 11 and returned to the integrated reactor 9 through the solvent recovery pipeline 17 to recover the catalyst and solvent. The product is then recrystallized in the recrystallization column 13, where it is purified by recrystallization with acetic acid. The product is then fed into the chlorination reactor 14, where chlorine gas is introduced into the chlorination reactor 14 at a rate of 0.175 mol / h through the chlorine gas feed pipeline 12 for chlorination. At the same time, the tail gas is fed into the alkaline absorption tower 21 through the tail gas treatment pipeline 20 for treatment. After the reaction, the product is recrystallized in the recrystallization column 25, where it is recrystallized with ethyl acetate. The product is then transported to the product storage tank 19 for storage.

[0035] In use, yellow phosphomolybdic acid powder, lanthanum nitrate hexahydrate, and deionized water are first added to the carrier preparation reactor 2 through feed port 1 and mixed evenly. Then, cesium carbonate and deionized water are prepared into a cesium carbonate solution and added dropwise to the carrier preparation reactor 2. After the reaction is completed, the precipitate is collected after post-treatment and placed in calcination device 3 for calcination to obtain the composite carrier.

[0036] The composite support and deionized water are added to the catalyst preparation reactor 4, then urea is added, and the mixture is refluxed for a period of time. Then, sodium chloropalladium solution, tetrachloroauric acid solution and other noble metal salt solutions are added. After the reaction is completed, the precipitate is collected after post-treatment and then reduced in the gas phase in the reduction device 5 under a mixed atmosphere of hydrogen and argon to reduce the metal ions into metal nanoparticles and load them onto the composite support. Hydrogen can be supplied to the reduction device 5 through the hydrogen feed pipe 6. After the reaction is completed, the supported catalyst is obtained.

[0037] 1-Chloro-2-methyl-3-nitrobenzene, N-hydroxyphthalimide, a mixed solvent of acetic acid and methanol, azobisisobutyronitrile, and a supported catalyst are sequentially added to an integrated reactor 9. Nitrogen is introduced through nitrogen inlet pipe 7 to displace the air in the integrated reactor 9. Then, oxygen is introduced through oxygen inlet pipe 8 to raise the internal pressure to a suitable range and increase the internal temperature. After the reaction is complete, the internal temperature of the integrated reactor 9 is lowered, and nitrogen is introduced through nitrogen inlet pipe 7 to displace the oxygen in the integrated reactor 9. Then, hydrogen is introduced through hydrogen inlet pipe 6 to raise the internal pressure to a suitable range. After the reaction is complete, the reactor is cooled to room temperature and filtered. The supported catalyst is filtered out by the reactor 10 and returned to the integrated reactor 9 via the catalyst recovery pipeline 18 for the production of the next batch of products. The filtrate is distilled by the multi-component distillation column 11, and the distilled solvent is collected and returned to the integrated reactor 9 via the solvent recovery pipeline 17. The desolventized product is returned to the integrated reactor 9, and toluene, trifluoroacetic acid and acrolein are added. The reaction is carried out at a certain temperature. After the reaction is completed, the pH of the solution is neutralized with sodium bicarbonate, filtered, and the filter cake and acetic acid are added to the recrystallization column 13 for recrystallization. After post-processing, 7-chloro-8-quinoline carboxylic acid is obtained.

[0038] 7-Chloro-8-quinoline carboxylic acid, 1,2-dichlorobenzene, and azobisisobutyronitrile are added to a chlorination reactor 14. Chlorine gas is introduced into the chlorination reactor 14 at a certain rate through a chlorine gas feed pipe 12, and the temperature is increased to carry out the reaction. After the reaction is completed, the temperature is lowered, and the tail gas in the reactor is passed through a tail gas treatment pipe 20 into an alkaline absorption tower 21 for absorption treatment. After filtration, the solid and ethyl acetate are added to a recrystallization tower 25 for recrystallization to obtain dichloroquinoline acid.

[0039] Example 2: This example provides a method for preparing dichloroquinoline acid using the preparation system described in Example 1, comprising the following steps:

[0040] S1: 967g of yellow phosphomolybdic acid powder, 12.5g of lanthanum nitrate hexahydrate, and 9.5L of deionized water were added to the carrier preparation reactor and mixed evenly. 275g of cesium carbonate and 14.3L of deionized water were mixed evenly to obtain a cesium carbonate solution with a concentration of 19.2g / L. This solution was then added dropwise to the carrier preparation reactor. After the addition was complete, the mixture was stirred at 550r / min for 2.5h, aged for 2.5h, centrifuged, and the precipitate was washed three times with deionized water. The precipitate was collected, dried at 125℃ for 13h, ground, and placed in a calcination apparatus. The temperature was increased to 310℃ at a rate of 5℃ / min, and calcined for 1.5h to obtain the composite carrier.

[0041] Phosphomolybdic acid and cesium carbonate undergo an ion exchange reaction in aqueous solution to form a cesium salt precipitate. Simultaneously, lanthanum ions from lanthanum nitrate hexahydrate are embedded in the Keggin interstitial structure of CsPMo through ionic or coordinate bonds, forming a lanthanum-doped composite precursor. After calcination at a high temperature of 300-320℃, the lanthanum ions are stably present in the crystal structure, ultimately forming a lanthanum-doped CsPMo composite support with high specific surface area, strong Lewis acidity, and electron transport capability.

[0042] S2: 60g of composite support and 5.5L of deionized water were added to the catalyst preparation reactor, followed by 14.34g of urea. The mixture was refluxed at 95℃ for 25min, then 17.75mL of 0.032mol / L sodium chloropalladium solution and 18.2mL of 0.03mol / L tetrachloroauric acid solution were added. The mixture was stirred at 95℃ and 600r / min for 1.5h, cooled to room temperature, centrifuged, and the precipitate was washed with deionized water until the pH value reached 7. The precipitate was dried at 62℃ for 13h, and then reduced in a mixed atmosphere of hydrogen and argon (hydrogen and argon volume ratio of 1:1) at 135℃ and a flow rate of 50mL / min for 2.5h to obtain the supported catalyst.

[0043] Bimetallic supported catalysts were prepared by a coprecipitation-gas phase reduction method. Urea was hydrolyzed at 90-100℃ to generate hydroxide ions, which increased the pH of the solution. Palladium and gold ions in sodium chloropalladate and tetrachloroauric acid coordinated with the bridging oxygen and terminal oxygen on the surface of the lanthanum-doped CsPMo composite support to form hydroxides, which were uniformly anchored on the surface of the composite support. Then, in a hydrogen-argon mixed atmosphere at 120-150℃, hydrogen acted as a reducing agent to reduce palladium and gold ions to metallic palladium and gold, forming alloy nanoparticles that were supported on the composite support to form a supported catalyst. Electron-rich regions were formed on the alloy surface, enhancing its activation ability for oxygen and hydrogen.

[0044] S3: 1.25 kg of 1-chloro-2-methyl-3-nitrobenzene, 58 g of N-hydroxyphthalimide, 5.5 L of a mixed solvent of acetic acid and methanol (volume ratio of acetic acid to methanol is 1:1), 5.5 g of azobisisobutyronitrile, and 25 g of supported catalyst were sequentially added to an integrated reactor. After purging the air with nitrogen, oxygen was introduced until the pressure inside the reactor reached 1.8 MPa, and the temperature was raised to 145 °C. The reaction was carried out for 5.5 h. After the reaction was completed, the temperature was lowered to 82 °C, and nitrogen was introduced to purge the oxygen. Then, hydrogen was introduced until the pressure inside the reactor reached 2.2 MPa, and the reaction was carried out at 90 °C for 3 hours. After 0.5 h, the mixture was cooled to room temperature, and the supported catalyst was recovered. The filtrate was then distilled in a multi-component distillation column to recover methanol and acetic acid. 5.75 L of toluene and 58 g of trifluoroacetic acid were added to the desolventized reaction vessel, the temperature was raised to 82 °C, and 355 g of acrolein was added dropwise. The reaction was maintained at 95 °C for 4.5 h. After the reaction was completed, the solution was neutralized to pH 6.8 with 5 wt% sodium bicarbonate, filtered, and the filter cake was recrystallized with 3 times its volume of acetic acid. After filtration and drying, 7-chloro-8-quinoline carboxylic acid was obtained.

[0045] 1-Chloro-2-methyl-3-nitrobenzene undergoes a free radical oxidation reaction in the presence of oxygen, N-hydroxyphthalimide, azobisisobutyronitrile, and a supported catalyst. The decomposition of azobisisobutyronitrile generates free radicals that initiate the formation of reactive oxygen species from N-hydroxyphthalimide, oxidizing the methyl group to a carboxyl group to generate 2-nitro-6-chlorobenzoic acid. Upon the introduction of hydrogen gas, the reactive hydrogen species on the surface of AuPd alloy nanoparticles in the supported catalyst reduce the nitro group in 2-nitro-6-chlorobenzoic acid to an amino group, generating 2-amino-6-chlorobenzoic acid. This 2-aminobenzoic acid then undergoes a Friedländer condensation reaction with acrolein under the catalysis of trifluoroacetic acid. The amino group and the aldehyde group of acrolein first form an imine intermediate, which then undergoes intramolecular electrophilic cyclization and dehydration to finally construct a quinoline ring skeleton, generating 7-chloro-8-quinoline carboxylic acid.

[0046] S4: 0.9 kg of 7-chloro-8-quinoline carboxylic acid, 4.5 L of 1,2-dichlorobenzene and 9 g of azobisisobutyronitrile were added to a chlorination reactor. 5.25 mol of chlorine gas was passed through the reactor at 105 °C at a rate of 0.175 mol / h. The reaction was carried out for 2.5 h, cooled, filtered, and the solid was diluted with 4 times its volume of ethyl acetate to obtain dichloroquinoline acid.

[0047] The 3-position of the quinoline ring in 7-chloro-8-quinoline carboxylic acid is an active site with a high electron cloud density. Chlorine radicals preferentially undergo electrophilic substitution reactions at this position, replacing hydrogen atoms with chlorine atoms to generate 3,7-dichloro-8-quinoline carboxylic acid (i.e., dichloroquinoline acid).

[0048] Example 3: This example provides a method for preparing dichloroquinoline acid using the preparation system described in Example 1, comprising the following steps:

[0049] S1: 934g of yellow phosphomolybdic acid powder, 10g of lanthanum nitrate hexahydrate, and 8.5L of deionized water were added to the carrier preparation reactor and mixed evenly. 250g of cesium carbonate and 12.8L of deionized water were mixed evenly to obtain a cesium carbonate solution with a concentration of 19.5g / L. This solution was then added dropwise to the carrier preparation reactor. After the addition was complete, the mixture was stirred at 500r / min for 2h, aged for 2h, centrifuged, and the precipitate was washed twice with deionized water. The precipitate was collected, dried at 120℃ for 12h, ground, and placed in a calcination apparatus. The temperature was increased to 300℃ at a rate of 5℃ / min, and calcined for 1h to obtain the composite carrier.

[0050] S2: 50g of composite support and 5L of deionized water were added to the catalyst preparation reactor, followed by 11.34g of urea. The mixture was refluxed at 90℃ for 20min. Then, 14.75mL of 0.032mol / L sodium chloropalladium solution and 16.2mL of 0.03mol / L tetrachloroauric acid solution were added. The mixture was stirred at 90℃ and 500r / min for 1h. After cooling to room temperature, the mixture was centrifuged. The precipitate was washed with deionized water until the pH value reached 7. The precipitate was dried at 60℃ for 12h and then reduced in a mixed atmosphere of hydrogen and argon (volume ratio of hydrogen to argon 1:1) at 120℃ and a flow rate of 50mL / min for 2h to obtain the supported catalyst.

[0051] S3: 1 kg of 1-chloro-2-methyl-3-nitrobenzene, 53 g of N-hydroxyphthalimide, 5 L of a mixed solvent of acetic acid and methanol (volume ratio of acetic acid to methanol is 1:1), 5 g of azobisisobutyronitrile, and 20 g of supported catalyst were sequentially added to an integrated reactor. After purging the air with nitrogen, oxygen was introduced until the pressure inside the reactor reached 1.8 MPa, and the temperature was raised to 140 °C. The reaction was carried out for 5 h. After the reaction was completed, the temperature was lowered to 80 °C, and nitrogen was introduced to purge the oxygen. Then, hydrogen was introduced until the pressure inside the reactor reached 2.2 MPa, and the reaction was carried out at 80 °C for 3 h. The mixture was cooled to room temperature, and the supported catalyst was recovered. The filtrate was distilled in a multi-component distillation column to recover methanol and acetic acid. 5.25 L of toluene and 53 g of trifluoroacetic acid were added to the desolventized reaction vessel, the temperature was raised to 80 °C, and 345 g of acrolein was added dropwise. The reaction was maintained at 90 °C for 4 h. After the reaction was completed, the pH was neutralized to 6.8 with 5 wt% sodium bicarbonate. The mixture was filtered, and the filter cake was recrystallized with 3 times its volume of acetic acid. After filtration and drying, 7-chloro-8-quinoline carboxylic acid was obtained.

[0052] S4: 0.8 kg of 7-chloro-8-quinoline carboxylic acid, 4 L of 1,2-dichlorobenzene and 8 g of azobisisobutyronitrile were added to a chlorination reactor. 5.25 mol of chlorine gas was passed through the reactor at 100 °C at a rate of 0.175 mol / h. The reaction was carried out for 2 h, cooled, filtered, and the solid was recrystallized with 4 times its volume of ethyl acetate to obtain dichloroquinoline acid.

[0053] Example 4: This example provides a method for preparing dichloroquinoline acid using the preparation system described in Example 1, comprising the following steps:

[0054] S1: 1000g of yellow phosphomolybdic acid powder, 15g of lanthanum nitrate hexahydrate, and 10.5L of deionized water were added to the carrier preparation reactor and mixed evenly. 300g of cesium carbonate and 15.8L of deionized water were mixed evenly to obtain a cesium carbonate solution with a concentration of 19.0g / L. This solution was then added dropwise to the carrier preparation reactor. After the addition was complete, the mixture was stirred at 600r / min for 3h, aged for 3h, centrifuged, and the precipitate was washed 4 times with deionized water. The precipitate was collected, dried at 130℃ for 14h, ground, and placed in a calcination apparatus. The temperature was increased to 320℃ at a rate of 5℃ / min and calcined for 2h to obtain the composite carrier.

[0055] S2: 70g of composite support and 6L of deionized water were added to the catalyst preparation reactor, followed by 17.34g of urea. The mixture was refluxed at 100℃ for 30min. Then, 20.75mL of sodium chloropalladium solution (0.032mol / L) and 20.2mL of tetrachloroauric acid solution (0.03mol / L) were added. The mixture was stirred at 100℃ and 700r / min for 2h. After cooling to room temperature, the mixture was centrifuged. The precipitate was washed with deionized water until the pH value reached 7. The precipitate was dried at 65℃ for 14h and then reduced in a mixed atmosphere of hydrogen and argon (hydrogen and argon volume ratio 1:1) at 150℃ and a flow rate of 50mL / min for 3h to obtain the supported catalyst.

[0056] S3: 1.5 kg of 1-chloro-2-methyl-3-nitrobenzene, 63 g of N-hydroxyphthalimide, 6 L of a mixed solvent of acetic acid and methanol (volume ratio of acetic acid to methanol is 1:1), 6 g of azobisisobutyronitrile, and 30 g of supported catalyst were sequentially added to an integrated reactor. After purging the air with nitrogen, oxygen was introduced until the pressure inside the reactor reached 1.8 MPa, and the temperature was raised to 150 °C. The reaction was carried out for 6 hours. After the reaction was completed, the temperature was lowered to 85 °C, and nitrogen was introduced to purge the oxygen. Then, hydrogen was introduced until the pressure inside the reactor reached 2.2 MPa, and the reaction was carried out at 100 °C for 4 hours. The mixture was cooled to room temperature, and the supported catalyst was recovered. The filtrate was then distilled in a multi-component distillation column to recover methanol and acetic acid. 6.25 L of toluene and 63 g of trifluoroacetic acid were added to the desolventized reaction vessel, the temperature was raised to 85 °C, and 365 g of acrolein was added dropwise. The reaction was maintained at 100 °C for 5 h. After the reaction was completed, the pH was neutralized to 6.8 with 5 wt% sodium bicarbonate. The mixture was filtered, and the filter cake was recrystallized with 3 times its volume of acetic acid. After filtration and drying, 7-chloro-8-quinoline carboxylic acid was obtained.

[0057] S4: 1.0 kg of 7-chloro-8-quinoline carboxylic acid, 5 L of 1,2-dichlorobenzene and 10 g of azobisisobutyronitrile were added to a chlorination reactor. 5.25 mol of chlorine gas was passed through the reactor at 110 °C at a rate of 0.175 mol / h. The reaction was carried out for 3 h, cooled, filtered, and the solid was recrystallized with 4 times its volume of ethyl acetate to obtain dichloroquinoline acid.

[0058] Example 5: This example provides a method for preparing dichloroquinoline acid, which differs from Example 2 in that the sodium chloropalladate solution is removed in step S2.

[0059] Example 6: This example provides a method for preparing dichloroquinoline acid, which differs from Example 2 in that the tetrachloroauric acid solution is removed in step S2.

[0060] Example 7: This example provides a method for preparing dichloroquinoline acid. The difference from Example 2 is that in step S2, the volume ratio of hydrogen and argon in the mixed atmosphere is 2:1.

[0061] Comparative Example 1: This comparative example provides a method for preparing dichloroquinoline acid, which differs from Example 2 in that the supported catalyst is removed in step S3.

[0062] Comparative Example 2: This comparative example provides a method for preparing dichloroquinoline acid. The difference from Example 2 is that in step S3, 0.017g of nano-gold and 0.011g of nano-palladium particles are used instead of the supported catalyst.

[0063] The supported catalysts prepared in Examples 2-7 were subjected to catalytic cycle stability tests:

[0064] The solventless oxidation of benzyl alcohol was carried out in a stainless steel magnetically stirred autoclave lined with polytetrafluoroethylene. 46 mmol of benzyl alcohol was added to the autoclave, along with a supported catalyst (Pd / alcohol molar ratio = 3.85 × 10⁻⁶). –5 After sealing, connect the reactor to high-purity oxygen (99.999%) and circulate the oxygen 3-5 times to replace the air inside the reactor. Then maintain the oxygen pressure at 0.4 MPa and start the reaction after the reactor reaches the predetermined temperature. After the reaction is complete, cool the reactor in an ice-water bath. Add n-tetradecane as an internal standard to the reaction product and analyze the reaction product using a gas chromatograph (Shimadzu GC-2014C) equipped with an Innowax column (30m × 0.25mm × 0.25μm). Each reaction is repeated three times to ensure the reproducibility of the results.

[0065] The reaction conversion rate was calculated using the following formula: Reaction conversion rate = (n0-n1) / n0 × 100%. The reaction conversion rate was tested after the catalyst was used five times.

[0066] The purity and yield of dichloroquinoline acid prepared in Examples 2-7 and Comparative Examples 1-2 were compared, and the results are shown in the table below:

[0067] Table 1. Summary of Product Purity and Yield

[0068] project Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Comparative Example 1 Comparative Example 2 Conversion rate (%) after 5 catalyst cycles 92.4 91.5 91.3 90.2 90.8 91.2 / / purity(%) 98.7 98.5 98.2 97.8 97.5 97.9 91.5 92.2 Yield (%) 93.2 92.9 92.5 92.1 93.1 92.2 60.8 78.5

[0069] As shown in Table 1, the purity and yield of Examples 2-7 are greater than those of Comparative Examples 1-2. This may be because the palladium-gold alloy on the supported catalyst and the support form a synergistic system of "Lewis acid sites + electron-rich metal active centers", which not only enhances substrate adsorption but also improves the activation efficiency of oxygen and hydrogen, thereby increasing the yield. The palladium-gold alloy inhibits polychlorination and improves the purity of the product. Moreover, the preparation process is a one-time oxidation-hydrogenation-ring-closure reaction, which eliminates cumbersome steps such as intermediate separation and drying, thereby eliminating material transfer loss from the reaction mechanism and further improving the conversion rate.

[0070] In Examples 2-7, the catalyst was cycled 5 times and the conversion rate remained above 90%, indicating that the catalyst has high cycle stability and can be used multiple times to ensure the utilization rate of the catalyst.

[0071] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for preparing dichloroquinoline acid, characterized in that, Includes the following steps: Step 1: A lanthanum-doped precursor was synthesized using phosphomolybdic acid, lanthanum nitrate hexahydrate, and cesium carbonate as raw materials. After calcination, a composite support was obtained. Then, a supported catalyst loaded with palladium alloy nanoparticles was prepared by coprecipitation-gas phase reduction method. The preparation process of the composite carrier is as follows: Yellow phosphomolybdic acid powder, lanthanum nitrate hexahydrate, and deionized water were added to a carrier preparation reactor and mixed evenly. A cesium carbonate solution with a concentration of 19.0-19.5 g / L was added dropwise to the carrier preparation reactor. After the addition was complete, the mixture was stirred for 2-3 hours, aged for 2-3 hours, centrifuged, washed, and the precipitate was collected, dried, and placed in a calcination apparatus. The precipitate was calcined at 300-320℃ for 1-2 hours to obtain the composite carrier. The preparation process of the supported catalyst is as follows: The composite support and deionized water were added to the catalyst preparation reactor, then urea was added, and the mixture was refluxed at 90-100℃ for 20-30 min. A noble metal salt solution was added, and the mixture was stirred at 90-100℃ and 500-700 r / min for 1-2 h. The mixture was cooled to room temperature, centrifuged, washed, and dried at 60-65℃ for 12-14 h. Then, the mixture was reduced in a mixed atmosphere of hydrogen and argon at 120-150℃ for 2-3 h to obtain the supported catalyst. Step 2: 1-Chloro-2-methyl-3-nitrobenzene undergoes a free radical oxidation reaction in the presence of oxygen, N-hydroxyphthalimide, azobisisobutyronitrile, and a supported catalyst, followed by a reduction reaction and a cyclization reaction to obtain 7-chloro-8-quinoline carboxylic acid, which is then chlorinated to obtain dichloroquinoline acid. The preparation process of 7-chloro-8-quinoline carboxylic acid in step two is as follows: 1-Chloro-2-methyl-3-nitrobenzene, N-hydroxyphthalimide, a mixed solvent of acetic acid and methanol, azobisisobutyronitrile, and a supported catalyst were sequentially added to an integrated reactor. After replacing the air with nitrogen, oxygen was introduced until the pressure inside the reactor reached 1.8 MPa, and the temperature was raised to 140-150℃. The reaction was carried out for 5-6 hours. After the reaction was completed, the temperature was lowered to 80-85℃, and nitrogen was introduced to replace the oxygen. Then, hydrogen was introduced until the pressure inside the reactor reached 2.2 MPa, and the reaction was carried out at 80-100℃ for 3-4 hours. After cooling to room temperature, the supported catalyst and solvent were recovered. Toluene and trifluoroacetic acid were then added, and the temperature was raised to 80-85℃. Acrolein was added dropwise, and the reaction was maintained at 90-100℃ for 4-5 hours. After the reaction was completed, the solution was neutralized to pH 6.8 with 5 wt% sodium bicarbonate. The solution was filtered, purified, and dried to obtain 7-chloro-8-quinoline carboxylic acid.

2. The method for preparing dichloroquinoline acid according to claim 1, characterized in that, The ratio of the yellow phosphomolybdic acid powder, lanthanum nitrate hexahydrate, deionized water, and cesium carbonate solution is 934-1000g: 10-15g: 8.5-10.5L: 12.8-15.8L.

3. The method for preparing dichloroquinoline acid according to claim 1, characterized in that, The ratio of the composite carrier, deionized water, urea, and precious metal salt solution is 50-70g: 5-6L: 11.34-17.34g: 30.95-40.95mL.

4. The method for preparing dichloroquinoline acid according to claim 3, characterized in that, The noble metal salt solution is one or a mixture of sodium chloropalladium solution and tetrachloroauric acid solution.

5. The method for preparing dichloroquinoline acid according to claim 1, characterized in that, The ratio of 1-chloro-2-methyl-3-nitrobenzene, N-hydroxyphthalimide, a mixture of acetic acid and methanol, azobisisobutyronitrile, supported catalyst, toluene, trifluoroacetic acid, and acrolein is 1-1.5 kg: 53-63 g: 5-6 L: 5-6 g: 20-30 g: 5.25-6.25 L: 53-63 g: 345-365 g.

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