A process and reaction system for producing 8-hydroxyquinoline

Abstract

This invention discloses a process and reaction system for producing 8-hydroxyquinoline, belonging to the field of chemical equipment and process technology. The invention uses o-aminophenol, o-nitrophenol, and acrolein as raw materials, p-toluenesulfonic acid as a catalyst, and a benzene solvent system to prepare 8-hydroxyquinoline. This solves the problems of high waste salt content, acrolein polymerization, large footprint, and unstable product indicators in current 8-hydroxyquinoline production processes. The process for producing 8-hydroxyquinoline in this invention has the advantages of simple equipment operation, stable operation, high production efficiency, high product purity, and environmental friendliness.

Description

Technical Field

[0001] This invention belongs to the field of chemical equipment and process technology, specifically a process and reaction system for producing 8-hydroxyquinoline. Background Technology

[0002] 8-Hydroxyquinoline is an organic compound with the chemical formula C9H7NO. It is a white or pale yellow crystalline powder, insoluble in water and ether, but soluble in ethanol, acetone, chloroform, benzene, and inorganic acids. It is mainly used as an intermediate in pharmaceuticals, dyes, and pesticides, and can also be used as a complexing agent and extractant for precipitating and separating metal ions.

[0003] Currently, there are four methods for synthesizing 8-hydroxyquinoline: sulfonation alkali dissolution, 8-chloroquinoline hydrolysis, 8-aminoquinoline hydrolysis, and the Skraup method. The mainstream production process is the Skraup method. Patent CN105777630A details the production of 8-hydroxyquinoline using the Skraup method. Compared to the other three methods, this process has the advantages of readily available raw materials and a simple synthesis route. However, this process has the following technical challenges: 1. The reaction process uses large amounts of hydrochloric acid or sulfuric acid as catalysts in an aqueous system. After the reaction, a large amount of alkali is required for neutralization. This results in low atom utilization, increased costs, and the generation of large amounts of hazardous waste, causing significant environmental pollution. With increasingly stringent environmental regulations, it faces the risk of being phased out. 2. Because acrolein is prone to polymerization at high temperatures, the heat and mass transfer in a batch reactor is poor, easily leading to localized overheating and excessively high concentrations in the reaction liquid, causing acrolein polymerization. Although some patents describe using zeolites and molecular sieves to increase dispersion, the effects are limited. Summary of the Invention

[0004] To address the problems of low atom utilization, excessive waste acid and salt, and acrolein polymerization in existing technologies, the present invention aims to provide a process and reaction system for producing 8-hydroxyquinoline.

[0005] To achieve the above objectives, the present invention employs the following technical solution:

[0006] A process for producing 8-hydroxyquinoline involves using o-aminophenol, o-nitrophenol, and acrolein as raw materials and p-toluenesulfonic acid as a catalyst in a benzene solvent system to prepare 8-hydroxyquinoline.

[0007] The process for producing 8-hydroxyquinoline includes the following steps:

[0008] 1) A benzene solution of o-aminophenol (30-50% by mass), a benzene solution of o-nitrophenol (20-48% by mass), and a benzene solution of p-toluenesulfonic acid (40-60% by mass) are respectively introduced into a falling film reactor. After a liquid film forms in the falling film reactor, the reactor is heated to 100-110°C, and then liquid acrolein is introduced into it. The liquid acrolein is rapidly vaporized, and a gas-liquid reaction takes place in the falling film reactor. After 6-8 hours of reaction, a reaction solution is obtained. The reaction temperature in the falling film reactor is controlled at 100-110°C, and the pressure is 0.18-0.23 MPa.

[0009] 2) Pass the reaction solution obtained in step 1) into the solvent removal vessel to remove the solvent benzene at 78~81℃. Pass the remaining mixture into a centrifuge for centrifugation. The resulting filter cake is washed and dried to obtain 8-hydroxyquinoline.

[0010] In step 1), the molar ratio of o-aminophenol to o-nitrophenol is 1.9~2.1:1; the molar ratio of p-toluenesulfonic acid, o-aminophenol and acrolein is 3.9~4.1:1:3.18~3.22.

[0011] In step 2), the mass of benzene removed as solvent is 20-40% of the total mass of the reaction solution.

[0012] The process for producing 8-hydroxyquinoline is achieved through the following reaction system:

[0013] The bottoms of the first, second, and third storage tanks are connected to the upper part of the falling film reactor via pipes a, b, and c, respectively; the fifth storage tank is connected to the bottom of the falling film reactor via a transfer pump and pipe g; the bottom of the falling film reactor is connected to the top of the stirred tank via pipe h; the stirred tank is connected to the plate and frame filter press via pipe i, a transfer pump, and pipe j; the plate and frame filter press is connected to the top of the desolventizing vessel via pipe k; the bottom outlet of the desolventizing vessel is connected to the top of the centrifuge via pipe o; the bottom solid outlet of the centrifuge is connected to the top of the dryer via pipe p.

[0014] The bottom side of the falling film reactor is connected to the bottom of the fourth storage tank via pipe f, a gas compressor, and pipe e; the top gas phase outlet of the falling film reactor is connected to the upper side of the fourth storage tank via pipe d.

[0015] The plate and frame filter press is connected to the top of the falling film reactor via pipe I.

[0016] The centrifuge side filtrate outlet is connected to the top of the desolvation vessel via a transfer pump and pipe n; the top gas phase outlet of the desolvation vessel is connected to the condenser via pipe m; the bottom condensate outlet of the condenser is connected to the top of the condensate storage tank via pipe q; and the lower side discharge port of the storage tank is connected to the first storage tank, the second storage tank, and the third storage tank via a transfer pump and pipe r.

[0017] The falling film reactor is equipped with a scraper to allow the reaction liquid to flow downwards in a thin film.

[0018] The pipes a, b, c, d, f and g are equipped with volumetric flow meters and controllers; the pipe o is equipped with an upward-expanding discharge valve to control the slurry discharge rate; and each pipe is equipped with a valve and a pump.

[0019] The process for producing 8-hydroxyquinoline according to the present invention has the following reaction formula:

[0020]

[0021] The present invention has the following advantages over the prior art:

[0022] The process for producing 8-hydroxyquinoline of this invention uses p-toluenesulfonic acid as a catalyst and a benzene solvent system for reaction. The acid catalyst p-toluenesulfonic acid forms a hydrate with the water generated in the reaction system, which on the one hand plays a role in dehydration and ring closure, promotes the main reaction, and improves reaction efficiency and yield. On the other hand, after p-toluenesulfonic acid combines with water, it precipitates out of the benzene system, which can be reused after high-temperature dehydration after filtration. This solves the problem of generating a large amount of solid waste and salt waste in the traditional process using hydrochloric acid / sulfuric acid-water system, reduces costs by 30-50%, and has a beneficial effect on environmental protection.

[0023] In this invention, the 8-hydroxyquinoline reaction system employs a falling film reactor. ① Benefiting from the characteristics of the falling film reactor, the reaction stage is a plug flow mode, resulting in a short contact time between the feed liquid and the heat medium, thus solving the problem of prolonged high-temperature polymerization of acrolein. ② Also benefiting from the characteristics of the falling film reactor, the feed liquid forms a 2-5 mm film, allowing for sufficient contact with the gaseous acrolein, improving mass transfer. ③ Furthermore, thanks to the characteristics of the falling film reactor, the gaseous acrolein flows through the reactor at a certain flow rate, providing a certain degree of disturbance, thus solving the problem of localized over-concentration. Overall, the falling film reactor fundamentally solves the problems of excessively high local temperatures and excessively high local concentrations of acrolein during the reaction process, thereby reducing acrolein polymerization, improving raw material utilization, and reducing the generation of tar-like impurities. Attached Figure Description

[0024] Figure 1 This is a connection diagram of the reaction system for producing 8-hydroxyquinoline according to the present invention;

[0025] In the diagram, 1-first storage tank; 2-second storage tank; 3-third storage tank; 4-fourth storage tank; 5-falling film reactor; 6-gas compressor; 7-fifth storage tank; 8-transfer pump; 9-stirred vessel; 10-transfer pump; 11-plate and frame filter press; 12-solvent removal vessel; 13-condenser; 14-centrifuge; 15-dryer; 16-condensate storage tank; 17-transfer pump; 18-transfer pump. Detailed Implementation

[0026] To better understand the technical solution of the present invention, the following detailed embodiments further illustrate the above-mentioned content of the present invention. However, this should not be construed as limiting the scope of the above-mentioned subject matter of the present invention to the following examples. All technologies implemented based on the above-mentioned content of the present invention fall within the scope of the present invention.

[0027] like Figure 1 As shown, the bottoms of the first storage tank 1, the second storage tank 2, and the third storage tank 3 are connected to the upper part of the falling film reactor 5 via pipes a, b, and c, respectively. The fourth storage tank 4 is connected to the bottom of the falling film reactor 5 via pipe e, gas compressor 6, and f. The fifth storage tank 7 is connected to the bottom of the falling film reactor 5 via a transfer pump 8 and a pipe g. The bottom of the falling film reactor 5 is connected to the top of the stirred tank 9 via pipe h. The stirred tank 9 is connected to the plate and frame filter press 11 via pipe i, transfer pump 10, and pipe j. The plate and frame filter press 11 is connected to the top of the desolventizing tank 12 via pipe k. The bottom outlet of the desolventizing tank 12 is connected to the top of the centrifuge 14 via pipe o. The bottom solid outlet of the centrifuge 14 is connected to the top of the dryer 15 via pipe p.

[0028] The bottom side of the falling film reactor 5 is connected to the bottom of the fourth storage tank 4 via pipe f, gas compressor 6 and pipe e; the top gas phase outlet of the falling film reactor 5 is connected to the upper side of the fourth storage tank 4 via pipe d.

[0029] The plate and frame filter press 11 is connected to the top side of the falling film reactor 5 via pipe I.

[0030] The filtrate outlet on the side of the centrifuge 14 is connected to the top of the desolvation vessel 12 via a transfer pump 18 and a pipe n; the gas phase outlet at the top of the desolvation vessel 12 is connected to the condenser 13 via a pipe m; the condensate outlet at the bottom of the condenser 13 is connected to the top of the condensate storage tank 16 via a pipe q; and the discharge port at the lower side of the storage tank 16 is connected to the first storage tank 1, the second storage tank 2, and the third storage tank 3 via a transfer pump 17 and a pipe r.

[0031] The falling film reactor 5 is equipped with a scraper to allow the reaction liquid to flow downwards in a thin film.

[0032] The pipes a, b, c, d, f and g are equipped with volumetric flow meters and controllers; the pipe o is equipped with an upward-expanding discharge valve to control the slurry discharge rate; and each pipe is equipped with a valve and a pump.

[0033] The first storage tank 1 stores a benzene solution of o-aminophenol, the second storage tank 2 stores a benzene solution of o-nitrophenol, the third storage tank 3 stores a benzene solution of p-toluenesulfonic acid, the fourth storage tank 4 stores unreacted acrolein in the gas phase, and the fifth storage tank 7 stores liquid acrolein. The first, second, and third storage tanks are at ambient temperature and pressure, while the pressure in the fourth storage tank 4 is 0.1~0.2 MPa. The discharge valves at the bottom of the first, second, and third storage tanks are opened, and the flow meters are interlocked with the valves to allow the raw materials to enter the falling film reactor 5. After a liquid film forms in the falling film reactor 5, the steam inlet and outlet valves of the jacket of the falling film reactor 5 are opened, and the equipment is heated. The temperature of the falling film reactor 5 is controlled at 100~110℃. Open the fifth storage tank 7 and use the transfer pump 8 to transport liquid acrolein to the falling film reactor 5. The acrolein is rapidly vaporized in the falling film reactor 5 and reacts with the raw materials in the falling film reactor 5 in a gas-liquid reaction. Control the reaction temperature at 100~110℃ and the pressure at 0.18~0.23Mpa. Unreacted acrolein gas enters the fourth storage tank 4, is pressurized by compressor 6, and then returns to the falling film reactor 5 to participate in the reaction. The unreacted reaction liquid enters the stirred tank 9, is filtered by the transfer pump 10 and plate and frame filter press 11 to remove p-toluenesulfonic acid monohydrate, and then returns to the falling film reactor 5. The reaction is carried out in a circulating and heat-preserving manner for 6-8 hours. After the reaction is complete, the reaction liquid enters the solvent removal tank 12. The temperature of the solvent removal tank 12 is controlled at 78-81℃. The mass fraction of benzene removed accounts for 20-40% of the total mass of the reaction liquid. The removed benzene is condensed by condenser 13 and enters the condensate storage tank 16, which is then returned to the first storage tank 1, the second storage tank 2, and the third storage tank 3 for reuse. The product precipitated from the solvent removal enters the centrifuge 14 for centrifugation. The resulting filter cake is washed and then dried in the dryer 15 to obtain the product 8-hydroxyquinoline.

[0034] Example 1: The first storage tank stores 2.75 kg of a benzene solution containing 40% o-aminophenol; the second storage tank stores 2.34 kg of a benzene solution containing 30% o-nitrophenol; the third storage tank stores 13.76 kg of a benzene solution containing 50% p-toluenesulfonic acid; the fourth storage tank stores unreacted acrolein in the gas phase; and the fifth storage tank stores 1.79 kg of liquid acrolein. The first, second, and third storage tanks are at ambient temperature and pressure, while the fourth storage tank has a pressure of 0.15 MPa. The discharge valves at the bottom of the first, second, and third storage tanks are opened, and the flow meters are interlocked with the valves to allow the raw materials to enter the falling film reactor. After a liquid film forms in the falling film reactor, the steam inlet and outlet valves of the falling film reactor jacket are opened, and the equipment is heated. The temperature of the falling film reactor is controlled at 105°C. The fifth storage tank is opened, and liquid acrolein is pumped to the falling film reactor using a transfer pump. The acrolein rapidly vaporizes in the falling film reactor and reacts with the raw materials within the reactor, maintaining a reaction temperature of 105℃ and a pressure of 0.2 MPa. Unreacted gaseous acrolein enters the fourth storage tank, is pressurized by a compressor, and then returns to the falling film reactor to participate in the reaction. The unreacted reaction liquid enters a stirred tank, is filtered by a transfer pump and a plate and frame filter press to remove p-toluenesulfonic acid monohydrate, and then re-enters the falling film reactor. The reaction is circulated and kept at a constant temperature for 7 hours. After complete reaction, the reaction liquid enters a solvent removal vessel, with the temperature controlled at 80℃. The removal of benzene by mass fraction accounts for 30% of the total reaction liquid mass. The removed benzene is condensed by a condenser and enters a condensate storage tank, then returned to the first, second, and third storage tanks for reuse. The product precipitated from the solvent removal process is centrifuged, and the resulting filter cake is washed and dried in a dryer to obtain the product 8-hydroxyquinoline. The product was tested and found to have a purity of 99.7%, a residue on ignition of 0.1%, chloride (Cl) of 10 ppm, sulfate of 80 ppm, iron limit of 12 ppm, and heavy metals of 13 ppm.

[0035] Example 2: The first storage tank stores 3.63 kg of a 30% o-aminophenol benzene solution; the second storage tank stores 3.66 kg of a 20% o-nitrophenol benzene solution; the third storage tank stores 16.77 kg of a 40% p-toluenesulfonic acid benzene solution; the fourth storage tank stores unreacted acrolein in the gas phase; and the fifth storage tank stores 1.78 kg of liquid acrolein. The first, second, and third storage tanks are at ambient temperature and pressure, while the fourth storage tank has a pressure of 0.1 MPa. The discharge valves at the bottom of the first, second, and third storage tanks are opened, and the flow meters are interlocked with the valves to allow the raw materials to enter the falling film reactor. After a liquid film forms in the falling film reactor, the steam inlet and outlet valves of the falling film reactor jacket are opened, and the equipment is heated. The temperature of the falling film reactor is controlled at 100°C. The fifth storage tank is opened, and liquid acrolein is pumped to the falling film reactor using a transfer pump. The acrolein rapidly vaporizes in the falling film reactor and reacts with the raw materials within the reactor, maintaining a reaction temperature of 100℃ and a pressure of 0.23 MPa. Unreacted gaseous acrolein enters the fourth storage tank, is pressurized by a compressor, and then returns to the falling film reactor to participate in the reaction. The unreacted reaction liquid enters a stirred tank, is filtered by a transfer pump and a plate and frame filter press to remove p-toluenesulfonic acid monohydrate, and then re-enters the falling film reactor. The reaction is circulated and kept at a constant temperature for 8 hours. After complete reaction, the reaction liquid enters a solvent removal vessel, with the temperature controlled at 78℃. The removal of benzene by mass fraction accounts for 20% of the total reaction liquid mass. The removed benzene is condensed by a condenser and enters a condensate storage tank, then returned to the first, second, and third storage tanks for reuse. The product precipitated from the solvent removal process is centrifuged, and the resulting filter cake is washed and dried in a dryer to obtain the product 8-hydroxyquinoline. The product was tested and found to have a purity of 99.5%, a residue on ignition of 0.13%, chloride (Cl) of 12 ppm, sulfate of 83 ppm, iron limit of 14 ppm, and heavy metals of 14 ppm.

[0036] Example 3: The first storage tank stores 2.18 kg of a benzene solution containing 50% o-aminophenol; the second storage tank stores 1.38 kg of a benzene solution containing 48% o-nitrophenol; the third storage tank stores 11.77 kg of a benzene solution containing 60% p-toluenesulfonic acid; the fourth storage tank stores unreacted acrolein in the gas phase; and the fifth storage tank stores 1.8 kg of liquid acrolein. The first, second, and third storage tanks are at ambient temperature and pressure, while the fourth storage tank has a pressure of 0.2 MPa. The discharge valves at the bottom of the first, second, and third storage tanks are opened, and the flow meters are interlocked with the valves to allow the raw materials to enter the falling film reactor. After a liquid film forms in the falling film reactor, the steam inlet and outlet valves of the falling film reactor jacket are opened, and the equipment is heated. The temperature of the falling film reactor is controlled at 110°C. The fifth storage tank is opened, and liquid acrolein is pumped to the falling film reactor using a transfer pump. The acrolein rapidly vaporizes in the falling film reactor and reacts with the raw materials within the reactor, maintaining a reaction temperature of 110℃ and a pressure of 0.18 MPa. Unreacted gaseous acrolein enters the fourth storage tank, is pressurized by a compressor, and then returns to the falling film reactor to participate in the reaction. The unreacted reaction liquid enters a stirred tank, is filtered by a transfer pump and a plate and frame filter press to remove p-toluenesulfonic acid monohydrate, and then re-enters the falling film reactor. The reaction is circulated and kept at a constant temperature for 6 hours. After the reaction is complete, the reaction liquid enters a solvent removal vessel, maintaining a temperature of 81℃. The removal of benzene by mass fraction accounts for 40% of the total reaction liquid mass. The removed benzene is condensed by a condenser and enters a condensate storage tank, then returned to the first, second, and third storage tanks for reuse. The product precipitated from the solvent removal process is centrifuged, and the resulting filter cake is washed and dried in a dryer to obtain the product 8-hydroxyquinoline. The product was tested and found to have a purity of 99.5%, a residue on ignition of 0.11%, chloride (Cl) of 11 ppm, sulfate of 81 ppm, iron limit of 13 ppm, and heavy metals of 13 ppm.

[0037] Example 4: The first storage tank stores 3.11 kg of a 35% o-aminophenol benzene solution; the second storage tank stores 2.85 kg of a 25% o-nitrophenol benzene solution; the third storage tank stores 15.11 kg of a 45% p-toluenesulfonic acid benzene solution; the fourth storage tank stores unreacted acrolein in the gas phase; and the fifth storage tank stores 1.78 kg of liquid acrolein. The first, second, and third storage tanks are at ambient temperature and pressure, while the fourth storage tank has a pressure of 0.12 MPa. The discharge valves at the bottom of the first, second, and third storage tanks are opened, and the flow meters are interlocked with the valves to allow the raw materials to enter the falling film reactor. After a liquid film forms in the falling film reactor, the steam inlet and outlet valves of the falling film reactor jacket are opened, and the equipment is heated. The temperature of the falling film reactor is controlled at 104°C. The fifth storage tank is opened, and liquid acrolein is pumped to the falling film reactor using a transfer pump. The acrolein rapidly vaporizes in the falling film reactor and reacts with the raw materials within the reactor, maintaining a reaction temperature of 104℃ and a pressure of 0.19 MPa. Unreacted gaseous acrolein enters the fourth storage tank, is pressurized by a compressor, and then returns to the falling film reactor to participate in the reaction. The unreacted reaction liquid enters a stirred tank, is filtered by a transfer pump and a plate and frame filter press to remove p-toluenesulfonic acid monohydrate, and then re-enters the falling film reactor. The reaction is circulated and kept at a constant temperature for 6.5 hours. After complete reaction, the reaction liquid enters a solvent removal vessel, maintaining a temperature of 79℃. The removal of benzene by mass fraction accounts for 25% of the total reaction liquid mass. The removed benzene is condensed by a condenser and enters a condensate storage tank, then returned to the first, second, and third storage tanks for reuse. The product precipitated from the solvent removal process is centrifuged, and the resulting filter cake is washed and dried in a dryer to obtain the product 8-hydroxyquinoline. The product was tested and found to have a purity of 99.6%, a residue on ignition of 0.12%, chloride (Cl) of 11 ppm, sulfate of 80 ppm, iron limit of 12 ppm, and heavy metals of 14 ppm.

[0038] Example 5: The first storage tank stores 2.42 kg of a benzene solution containing 45% o-aminophenol; the second storage tank stores 1.70 kg of a benzene solution containing 40% o-nitrophenol; the third storage tank stores 12.73 kg of a benzene solution containing 55% p-toluenesulfonic acid; the fourth storage tank stores unreacted acrolein in the gas phase; and the fifth storage tank stores 1.79 kg of liquid acrolein. The first, second, and third storage tanks are at ambient temperature and pressure, while the fourth storage tank has a pressure of 0.18 MPa. The discharge valves at the bottom of the first, second, and third storage tanks are opened, and the flow meters are interlocked with the valves to allow the raw materials to enter the falling film reactor. After a liquid film forms in the falling film reactor, the steam inlet and outlet valves of the falling film reactor jacket are opened, and the equipment is heated. The temperature of the falling film reactor is controlled at 108°C. The fifth storage tank is opened, and liquid acrolein is pumped to the falling film reactor using a transfer pump. The acrolein rapidly vaporizes in the falling film reactor and reacts with the raw materials within the reactor, maintaining a reaction temperature of 108℃ and a pressure of 0.22 MPa. Unreacted gaseous acrolein enters the fourth storage tank, is pressurized by a compressor, and then returns to the falling film reactor to participate in the reaction. The unreacted reaction liquid enters a stirred tank, is filtered by a transfer pump and a plate and frame filter press to remove p-toluenesulfonic acid monohydrate, and then re-enters the falling film reactor. The reaction is circulated and kept at a constant temperature for 7.8 hours. After complete reaction, the reaction liquid enters a solvent removal vessel, maintaining a temperature of 80℃. The removal of benzene by mass fraction accounts for 35% of the total reaction liquid mass. The removed benzene is condensed by a condenser and enters a condensate storage tank, then returned to the first, second, and third storage tanks for reuse. The product precipitated from the solvent removal process is centrifuged, and the resulting filter cake is washed and dried in a dryer to obtain the product 8-hydroxyquinoline. The product was tested and found to have a purity of 99.6%, a residue on ignition of 0.10%, chloride (Cl) of 10 ppm, sulfate of 81 ppm, iron limit of 13 ppm, and heavy metals of 13 ppm.

[0039] While the specific embodiments of the present invention have been described above, they are not intended to limit the scope of protection of the present invention. Based on the technical solutions of the present invention, various modifications or variations that can be made by those skilled in the art without creative effort are still within the scope of protection of the present invention.

Claims

1. A process for producing 8-hydroxyquinoline, characterized in that: 1) A benzene solution of o-aminophenol (30-50% by mass), a benzene solution of o-nitrophenol (20-48% by mass), and a benzene solution of p-toluenesulfonic acid (40-60% by mass) are respectively introduced into a falling film reactor. After a liquid film forms in the falling film reactor, the reactor is heated to 100-110°C, and then liquid acrolein is introduced into it. The liquid acrolein is rapidly vaporized, and a gas-liquid reaction takes place in the falling film reactor. After 6-8 hours of reaction, a reaction solution is obtained. The reaction temperature in the falling film reactor is controlled at 100-110°C, and the pressure is 0.18-0.23 MPa. 2) Pass the reaction solution obtained in step 1) into a solvent removal vessel to remove the solvent benzene at 78~81℃. Pass the remaining mixture into a centrifuge for centrifugation. The resulting filter cake is washed and dried to obtain 8-hydroxyquinoline.

2. The process for producing 8-hydroxyquinoline according to claim 1, characterized by: In step 1), the molar ratio of o-aminophenol to o-nitrophenol is 1.9~2.1:1; the molar ratio of p-toluenesulfonic acid, o-aminophenol and acrolein is 3.9~4.1:1:3.18~3.

22.

3. The process for producing 8-hydroxyquinoline according to claim 1, characterized by: In step 2), the mass of benzene removed as solvent is 20-40% of the total mass of the reaction solution.

4. The process for producing 8-hydroxyquinoline according to claim 1, characterized by: The process for producing 8-hydroxyquinoline is achieved through the following reaction system: the bottoms of the first tank (1), the second tank (2), and the third tank (3) are connected to the upper part of the falling film reactor (5) via pipes a, b, and c, respectively; the fifth tank (7) is connected to the bottom of the falling film reactor (5) via a transfer pump (8) and pipe g; the bottom of the falling film reactor (5) is connected to the top of the stirred tank (9) via pipe h; the stirred tank (9) is connected to the plate and frame filter press (11) via pipe i, a transfer pump (10), and pipe j; the plate and frame filter press (11) is connected to the top of the desolventizing tank (12) via pipe k; the bottom outlet of the desolventizing tank (12) is connected to the top of the centrifuge (14) via pipe o; the bottom solid outlet of the centrifuge (14) is connected to the top of the dryer (15) via pipe p.

5. The process for producing 8-hydroxyquinoline according to claim 4, characterized by: The bottom side of the falling film reactor (5) is connected to the bottom of the fourth storage tank (4) via pipe f, gas compressor (6) and pipe e; the top gas phase outlet of the falling film reactor (5) is connected to the upper side of the fourth storage tank (4) via pipe d.

6. The process for producing 8-hydroxyquinoline according to claim 4, wherein: The plate and frame filter press (11) is connected to the top side of the falling film reactor (5) via pipe I.

7. The process for producing 8-hydroxyquinoline according to claim 4, wherein: The filtrate outlet on the side of the centrifuge (14) is connected to the top of the desolvation vessel (12) via a transfer pump (18) and pipe n; the gas phase outlet at the top of the desolvation vessel (12) is connected to the condenser (13) via pipe m; the condensate outlet at the bottom of the condenser (13) is connected to the top of the condensate storage tank (16) via pipe q; the discharge port at the lower side of the condensate storage tank (16) is connected to the first storage tank (1), the second storage tank (2), and the third storage tank (3) via a transfer pump (17) and pipe r.

8. The process for producing 8-hydroxyquinoline according to claim 4, characterized by: The falling film reactor (5) is equipped with a scraper so that the reaction liquid flows downward in a thin film.

9. The process for producing 8-hydroxyquinoline according to claim 5, wherein: The pipes a, b, c, d, f and g are equipped with volumetric flow meters and controllers; the pipe o is equipped with an upward-expanding discharge valve to control the slurry discharge rate; and each pipe is equipped with a valve and a pump.

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