Preparation process of 8-hydroxyquinoline

Abstract

The invention relates to the technical field of chemical synthesis, and discloses a preparation process of 8-hydroxyquinoline, which comprises the following steps: 1, adding o-nitrophenol and o-aminophenol into a reaction container; step 2, adding concentrated sulfuric acid and glycerol, and heating; step 3, after cooling, adding an organic phase enrichment solvent and an alkaline solution; and 4, blending and converting 8-hydroxyquinoline in the organic phase and the water phase, adjusting the pH value, and separating out the product. The problem of viscous tar is avoided, so that filtering and separation become convenient.

Description

Technical Field

[0001] The present invention relates to the technical field of chemical synthesis, and particularly relates to a preparation process of 8-hydroxyquinoline. Background Art

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

[0003] Currently, 8-hydroxyquinoline is mainly synthesized by the Skraup method. The operation process is as follows: Mix o-aminophenol, glycerol, and concentrated sulfuric acid, and slowly heat to 120 - 130 °C with stirring. Add nitrobenzene, and control the temperature not to exceed 150 °C to avoid violent exotherm. Reflux for 4 - 6 hours until the reaction solution turns dark brown. After cooling, neutralize with sodium hydroxide solution to pH≈7, and precipitate the crude product.

[0004] Reaction mechanism: Glycerol dehydrates under concentrated sulfuric acid and high temperature to form α,β-unsaturated aldehyde (acrolein). The amino group (-NH2) of o-aminophenol undergoes Michael addition with acrolein to form an intermediate imine. Subsequently, dehydration cyclization occurs under acidic conditions to form a dihydroquinoline skeleton. Nitrobenzene (or arsenic acid) acts as an oxidant to oxidize dihydroquinoline to an aromatic quinoline ring, and at the same time, the hydroxyl group is located at the 8th position of the benzene ring.

[0005] Chinese patent document CN102140078B discloses an improved Skraup method for preparing quinoline or quinoline derivatives. Add 18 Kg of glycerol, 11 Kg of o-aminophenol, and 10 Kg of o-nitrophenol to 100 L of ethyl acetate; slowly add 9.0 Kg of concentrated sulfuric acid with a volume concentration fraction of 98% while stirring; heat the reaction kettle with steam to maintain a reflux state at a temperature of 90 - 100 °C, and use thin-layer chromatography to detect and track the reaction progress until the o-aminophenol spot disappears; add 100 L of water to the reaction solution, cool to 20 - 40 °C, let it stand for stratification, take the aqueous phase, extract the separated organic phase with 30 L of water, and take the aqueous phase; combine the aqueous phases, dropwise add sodium hydroxide with a mass fraction of 30% to the combined aqueous phases, adjust the pH value to 7.0 (6.5 - 7.2 can all be achieved), a large amount of oil-like substances will precipitate. Remove the aqueous phase solvent, dry the oil-like substances with flake caustic soda to obtain crude quinoline, and perform reduced-pressure distillation at 3 mmHg to obtain 13 Kg of 8-hydroxyquinoline.

[0006] Although existing patent documents have improved the traditional Skraup method, after the discharging is completed, the substrate will remain tar-like residues like asphalt. After the system cools, the tar hardens and increases the total viscosity of the system, making it difficult to separate and extract 8-hydroxyquinoline. Summary of the Invention

[0007] In order to solve the technical problem that 8-hydroxyquinoline is difficult to extract due to tar hardening during discharging, the present invention provides a preparation process of 8-hydroxyquinoline, which is characterized by including the following steps: Step 1: Add o-nitrophenol and o-aminophenol into a reaction vessel; Step 2: Add concentrated sulfuric acid and glycerol and heat; Step 3: After cooling, add an organic phase enrichment solvent and an alkaline solution; Step 4: After 8-hydroxyquinoline is adjusted and converted between the organic phase and the aqueous phase, adjust the pH value of the aqueous phase to precipitate the product.

[0008] Preferably, in Step 4, the adjustment and conversion of 8-hydroxyquinoline between the organic phase and the aqueous phase are specifically as follows: Extract and separate to obtain the organic phase, add an acidic solution to the organic phase and then separate to obtain the aqueous phase.

[0009] Preferably, the organic phase enrichment solvent uses a carboxylic acid ester-based hydrophobic compound.

[0010] Further, the carboxylic acid ester-based hydrophobic compound uses one or more of ethyl acetate, propyl formate, isopropyl formate, methyl acetate, propyl acetate, isopropyl acetate, and isobutyl formate.

[0011] In order to ensure the smoothness and safety of the reaction, in Step 1, add a hydrophobic compound with a boiling point higher than the reaction system temperature and a density lower than the reaction solution density as a buffer solvent.

[0012] Preferably, the buffer solvent uses an alkylbenzene and / or an ester compound.

[0013] Further, the alkylbenzene uses one or more of mixed xylene, o-xylene, p-xylene, m-xylene, and trimethylbenzene.

[0014] Further, the ester compound uses one or more of diethyl carbonate, dipropyl carbonate, methyl oleate, isopentyl formate, and benzyl formate.

[0015] In order to reduce pollution and save costs, it further includes Step 5: Add an alkaline solution and an adsorbent to the organic phase finally separated in Step 4, separate the system by liquid separation, add an acidic solution to the aqueous phase to adjust the pH and then cool to recover o-nitrophenol, and concentrate the organic phase at low temperature and high temperature to respectively recover the organic phase enrichment solvent and the buffer solvent.

[0016] Further, the adsorbent uses one or more of diatomite, kaolin, activated carbon, and perlite.

[0017] The present invention has the following beneficial effects: 1. In the present invention, by adding an organic-phase enrichment solvent, the organic-phase enrichment solvent first enriches 8-hydroxyquinoline in the organic phase, then transfers it to the aqueous phase and then adjusts and precipitates 8-hydroxyquinoline. Utilizing the amphoteric compound characteristics of 8-hydroxyquinoline, an alkaline solution is added during extraction to adjust the pH value, reducing the water solubility of 8-hydroxyquinoline and increasing its solubility in the organic phase. Subsequently, through liquid separation operation, 8-hydroxyquinoline, o-nitrophenol and most organic impurities are enriched in the organic phase, while the aqueous phase is a saturated sulfate solution and a small amount of organic matter. Finally, through steps such as mixing extraction with an acidic aqueous solution and extraction with an alkaline solution, and adjusting and precipitating, high-purity products can be obtained, achieving efficient separation of 8-hydroxyquinoline with high consistency, avoiding the sticky tar problem that occurs in the prior art when directly extracting from the aqueous phase, and making the filtration and separation convenient.

[0018] 2. Significantly simplifies the requirements for reaction equipment. During the process, by adding an organic-phase enrichment solvent and a buffer solvent, layer control of the reaction system and product separation are achieved. For 8-hydroxyquinoline and o-nitrophenol, only through acid-base adjustment, the transfer between the aqueous phase and the organic phase is realized, and finally they are precipitated in water respectively. This design does not require special steam distillation equipment, reducing the equipment investment cost and the difficulty of production line design. Except for the reaction section which requires a stainless steel reaction kettle, other sections can use plastic equipment made of PP or PPH materials, further reducing the construction cost and the complexity of equipment maintenance.

[0019] 3. The present invention adopts a unique solvent layering technology. When starting the reaction by heating, the density of the high-boiling buffer solvent is low, and the buffer solvent is layered with the reaction system, forming a buffer solvent layer. The buffer solvent and the reaction zone are in a liquid separation state with an obvious boundary, showing that the auxiliary agent in the whole reaction system, because of its high boiling point, can absorb most of the heat during reaction excitation, ensuring the smooth and safe reaction. By gasification endotherm, the sharp rise in reaction temperature is effectively controlled, avoiding the risk of system boiling over and flushing materials. At the same time, during the reflux process, the buffer solvent takes away the rising moisture, realizing continuous and gentle water drainage, promoting the forward reaction of the reaction system, and further optimizing the reaction kinetics. This design not only improves the safety of the reaction, but also makes the reaction process more controllable and reasonable. Detailed implementation mode

[0020] The following is further detailed through specific implementation modes: Those skilled in the art are aware that o-nitrophenol, also known as 2-nitrophenol, is an important nitroaromatic compound with the chemical formula C6H5NO3. It is a pale yellow crystalline powder, soluble in hot water, easily soluble in ethanol, ether, and benzene, and has both acidity and reactivity. It is mainly used as a dye, medicine, and organic synthesis intermediate.

[0021] Those skilled in the art are aware that o-aminophenol, also known as 2-aminophenol, is an organic compound with the chemical formula C6H7NO.

[0022] Those skilled in the art are aware that glycerol, also known as glycerin, is an organic compound with the chemical formula C3H8O3 and is a simple polyol compound. It is a colorless, odorless, sweet, viscous liquid and is non-toxic. The glycerol backbone is present in lipids called glycerides.

[0023] Those skilled in the art are aware that an aqueous phase is a liquid phase system with water as the main solvent and usually contains polar substances (such as inorganic salts, acids, bases, ionic compounds, or hydrophilic organic compounds); An organic phase is a liquid phase system mainly composed of organic solvents and usually dissolves non-polar or weakly polar substances (such as hydrocarbons, esters, neutral organic compounds).

[0024] Those skilled in the art are aware that the general formula of carboxylic esters is RCOOR', where R is the hydrocarbon group from carboxylic acid (RCOOH) and R' is the hydrocarbon group from alcohol (R'OH). For example, ethyl acetate: CH3COOCH2CH3 (formed by the reaction of acetic acid and ethanol); methyl oleate: CH3(CH2)7CH=CH(CH2)7COOCH3 (formed by the reaction of oleic acid and methanol).

[0025] Those skilled in the art are aware that the boiling point of ethyl acetate is 76.6 - 77.5 °C, the boiling point of propyl formate is 80 - 81 °C, the boiling point of isopropyl formate is 68 °C, the boiling point of methyl acetate is 56.8 °C, the boiling point of propyl acetate is 102 °C, the boiling point of isopropyl acetate is 88.8 °C, and the boiling point of isobutyl formate is 98.4 °C.

[0026] Those skilled in the art are aware that the boiling point of xylenes is 137 - 140 °C, the boiling point of trimethylbenzenes is 163 - 166 °C, the boiling point of diethyl carbonate is 126 - 128 °C, the boiling point of dipropyl carbonate is 167 - 186 °C, the boiling point of methyl oleate is 168 - 170 °C, the boiling point of isoamyl formate is 123 - 124 °C, and the boiling point of benzyl formate is 195 - 210 °C.

[0027] A preparation process for 8-hydroxyquinoline includes the following steps: Step 1: Add a buffer solvent, o-nitrophenol, and o-aminophenol into a reaction vessel; Step 2: After the temperature stabilizes, slowly add concentrated sulfuric acid at a dropping rate controlled between 1.8 g / s and 4.3 g / s. After the addition of sulfuric acid is completed, slowly add glycerol at a dropping rate controlled between 2.1 g / s and 5.3 g / s. After all the materials are added, start heating to maintain the temperature of the reaction system at 120 - 155 °C. Starting from the time when boiling bubbles begin to appear on the surface of the system as the timing point, the reaction time is 90 min - 450 min; Step 3: After the reaction ends, cool to 50 - 60 °C, add an organic phase enrichment solvent to the system, and then slowly add an alkaline solution dropwise. After the addition is completed, stir and cool down. When the temperature drops to 10 - 25 °C, it can be regarded as the end; Step 4: After the system is filtered, the filtrate is stored separately. Add an organic phase enrichment solvent to the solid and stir for washing. After the washing is completed, perform another round of solid-liquid separation, filter as dry as possible, collect and summarize the filtrate, and collect and dry the solid. Stir and wash the filtrate, and after the washing is completed, separate the liquid. The aqueous phase is extracted with an organic phase enrichment solvent again, and then separated. The aqueous phase is collected centrally, and the organic phases are summarized. Add water and phosphoric acid to the organic phase, stir and then separate the liquid. The organic phase is transferred to the raw material recovery step, and the aqueous phase is transferred to the discharging step; Step 5: Add an adsorbent to the aqueous phase. First, add dilute alkali solution during stirring. After adding, let it stand still to allow the adsorbent to fully precipitate. Separate the solid and liquid to remove the precipitate impurities. Add dilute alkali solution to the filtrate while stirring. After adding, let it stand for minutes, separate the solid and liquid, wash the solid with additional water, and filter to obtain the product. Dry 8-hydroxyquinoline in a rake dryer to obtain the dry material.

[0028] Step 6: For the treated organic phase, add an alkaline solution and an adsorbent, adjust the pH value and then perform solid-liquid separation, and conduct low-temperature and high-temperature concentration to recover the organic phase enrichment solvent and buffer solvent respectively.

[0029] Example 1: Step 1: Add 37.19 L of dipropyl carbonate to a 150 L reaction kettle. During stirring, put 18.17 kg of o-nitrophenol and 11 kg of o-aminophenol into it; Step 2: After the temperature stabilizes, slowly add 13.32 kg of concentrated sulfuric acid and finish the dropping within 80 min. After the addition of sulfuric acid is completed, slowly add 25.84 kg of glycerol, which should be added within 200 min. After all the materials are added, start heating to maintain the system temperature at 125 ± 2 °C. Starting from the time when boiling bubbles begin to appear on the surface of the system as the timing point, the reaction time is 180 min; Step 3: After the reaction ends, cool to 59 °C, add 42.04 L of isopropyl formate to the system, and then slowly add 35% potassium hydroxide solution dropwise. After the addition is completed, stir and cool down. When the temperature drops to 10 °C, it can be regarded as the end; Step 4: After the system is filtered, the filtrate is stored separately. 77.12 L of isopropyl formate is added to the solid and stirred for washing for 15 min. After washing, solid-liquid separation is carried out again to filter as dry as possible. The filtrates are aggregated, and the solid is collected and dried. The filtrate is stirred and washed for 85 min. After washing, liquid separation is carried out. 23.37 L of isopropyl formate is added to the aqueous phase for extraction for 30 min, and then liquid separation is carried out again. The aqueous phase is centrally collected into the potassium sulfate storage tank, and the organic phases are aggregated. 103.10 kg of water and 17.83 kg of 85% phosphoric acid are added to the organic phase, stirred for 40 min and then liquid separation is carried out. The organic phase is transferred to the raw material recovery step. The aqueous phase is transferred to the discharging step; Step 5: 1.46 kg of kaolin is added to the aqueous phase as an adsorbent. 21.58 kg of 16% dilute alkali solution is first added during stirring. After adding, it is left standing for 2 h to allow the kaolin to precipitate fully. The precipitate impurities are removed by solid-liquid separation. 78.16 kg of 16% dilute alkali solution is added to the filtrate during stirring. After adding, it is left standing for 10 minutes, followed by solid-liquid separation. The solid is washed with an additional 57.44 kg of water for 45 min, and the product is obtained by filtration. 8-Hydroxyquinoline is dried in a rake dryer at 65 °C for 8 h to obtain 11.24 kg of dry material, with a yield of 76.86% and a content of 96.20%.

[0030] Step 6: 200.00 kg of water and 26.00 kg of solid potassium hydroxide are added to the treated organic phase. 1.52 kg of calcined diatomaceous earth is added during stirring. After stirring for 30 min, filtration is carried out. The system is separated by liquid. Dilute phosphoric acid solution (10%) is added to the aqueous phase for adjustment until the pH equals 6.3. It is cooled at 8 °C for 10 h to obtain 4.15 kg of o-nitrophenol particles, with a recovery rate of 22.83%. Solid-liquid separation is carried out, and the solid is air-dried. The organic phase is concentrated under reduced pressure at 40 °C and 97 °C, -0.092 MPa according to the selected solvent to obtain 80.71 kg of isopropyl formate, with a recovery rate of 75.19%, and 21.39 kg of dipropyl carbonate, with a recovery rate of 57.85%.

[0031] Example 2 Step 1: 32.88 L of mesitylene is added to a 150 L reaction kettle. During stirring, 15.1 kg of o-nitrophenol and 10 kg of o-aminophenol are put into it; Step 2: After the temperature is stabilized, 14.19 kg of concentrated sulfuric acid is slowly added dropwise and completed within 120 min. After the addition of sulfuric acid is completed, 25.63 kg of glycerol is slowly added and should be added within 90 min. After all the materials are added, the temperature is raised to maintain the system temperature at 150 ± 2 °C. Starting from the time when boiling bubbles begin to appear on the surface of the system, the reaction time is 430 min.

[0032] Step 3: After the reaction is completed, cool to 49°C, add 33.82 L of methyl acetate to the system, and then dropwise add 35% potassium hydroxide solution. After the addition is complete, stir and cool down. When the temperature drops to 20°C, it can be regarded as the end; Step 4: After the system is filtered, the filtrate is stored separately. Add 62.12 L of methyl acetate to the solid and stir for washing for 15 min. After washing, perform another solid-liquid separation, filter as dry as possible, collect and summarize the filtrate, and collect and dry the solid. Stir and wash the filtrate for 85 min. After washing, separate the liquid. Add 18.87 L of methyl acetate to the aqueous phase for extraction for 30 min, then separate the liquid again. Collect the aqueous phase centrally into the potassium sulfate storage tank, summarize the organic phase, add 120.05 kg of 12% sulfuric acid to the organic phase, stir for 40 min and then separate the liquid. Transfer the organic phase to the raw material recovery step. Transfer the aqueous phase to the discharging step.

[0033] Step 5: Add 1.26 kg of kaolin as an adsorbent to the aqueous phase. First, add 16.78 kg of 16% dilute alkali solution during stirring. After adding, let it stand for 2 h to allow the kaolin to precipitate fully. Separate the solid and liquid to remove the precipitate impurities. Add 77.17 kg of 16% dilute alkali solution to the filtrate under stirring. After adding, let it stand for 10 minutes, separate the solid and liquid, wash the solid with an additional 57.44 kg of water for 45 min, and filter to obtain the product. Dry 8-hydroxyquinoline at 65°C in a rake dryer for 8 hours to obtain 10.54 kg of dry material, with a yield of 79.26% and a content of 93.71%; Step 6: Add 200.00 kg of water and 23.64 kg of solid potassium hydroxide to the treated organic phase. Add 1.33 kg of calcined diatomaceous earth during stirring. After stirring for 30 minutes, filter. Separate the liquid in the system. Add dilute sulfuric acid solution (12%) to the aqueous phase for adjustment until the pH equals 6.8 to end. Cool at 8°C for 10 h to obtain 3.84 kg of o-nitrophenol particles, with a recovery rate of 25.43%. Separate the solid and liquid, and air-dry the solid. Concentrate the organic phase under reduced pressure at 32°C and 95°C, -0.092 MPa according to the selected solvent to obtain 77.27 kg of methyl acetate, with a recovery rate of 72.21%, and 19.36 kg of mesitylene, with a recovery rate of 67.90%.

[0034] Example 3 Step 1: Add 37.19 L of mixed xylene to a 150 L reaction kettle. During stirring, add 15.93 kg of o-nitrophenol and 11.22 kg of o-aminophenol into it, and simultaneously raise the temperature to make the system temperature reach 63 ± 2°C appropriately; Step 2: After the temperature stabilizes, slowly add 33.32 kg of concentrated sulfuric acid and finish the addition within 130 minutes. After the addition of sulfuric acid is completed, slowly add 28.84 kg of glycerol and finish the addition within 90 minutes. After all the materials are added, start heating to maintain the system temperature at 132 ± 2 °C. Starting from the time when boiling begins on the surface of the system or condensate appears, the reaction time is 370 minutes. Step 3: After the reaction ends, cool to 61 °C, add 42.04 L of ethyl acetate to the system, and then slowly add 96.11 kg of 35% potassium hydroxide solution. When the internal temperature reaches 68 - 70 °C, start circulating water to cool the system. After the addition is completed, stir and cool. When the temperature drops to 20 - 25 °C, it can be regarded as the end. Step 4: After the system is filtered, the filtrate is stored separately. Add 77.12 L of ethyl acetate to the solid and stir for washing for 40 minutes. After the washing is completed, perform another solid-liquid separation and filter as dry as possible. The filtrates are aggregated, and the solid is collected and dried. The filtrate is stirred and washed for 30 minutes. After the washing is completed, separate the liquid. The aqueous phase is added with 23.37 L of ethyl acetate for extraction for 30 minutes, and then separated again. The aqueous phase is centrally collected into the potassium sulfate storage tank, and the organic phases are aggregated. 102.90 kg of water and 17.95 kg of 85% phosphoric acid are added to the organic phase, stirred for 40 minutes and then separated. The organic phase is transferred to the raw material recovery step. The aqueous phase is transferred to the discharging step. Step 5: Add 1.46 kg of calcined diatomaceous earth as an adsorbent to the aqueous phase. First, add 22.52 kg of 16% dilute alkali solution while stirring. After the addition is completed, let it stand for 2 hours to allow the diatomaceous earth and the precipitated impurities to fully precipitate, and separate the solid and liquid to remove the precipitated impurities. While stirring, add 68.56 kg of 16% dilute alkali solution to the filtrate to adjust the pH to 7.3. After the addition is completed, let it stand for 10 minutes. Separate the solid and liquid. The solid is washed with an additional 57.44 kg of water for 45 minutes, and the product is obtained by filtration. 8-Hydroxyquinoline is dried at 55 °C in a rake dryer for 10 hours to obtain 12.29 kg of dry material, with a yield of 82.35% and a content of 97.10%. Step 6: Add 200.00 kg of water and 26.30 kg of solid potassium hydroxide to the treated organic phase. Add 1.52 kg of calcined diatomaceous earth while stirring, stir for 30 minutes, then filter. Separate the liquid in the system. The aqueous phase is added with a dilute phosphoric acid solution for adjustment and the adjustment ends when the pH equals 6.5. Cool at 8 °C for 6 hours to obtain 6.29 kg of o-nitrophenol particles, with a recovery rate of 39.48%. Separate the solid and liquid, and air-dry the solid. The organic phase is concentrated under reduced pressure at 42 °C and 80 °C, -0.092 MPa according to the selected solvent to obtain 107.30 kg of ethyl acetate, with a recovery rate of 83.43%, and 20.32 kg of mixed xylene, with a recovery rate of 63.50%.

[0035] In Examples 1 - 3, different buffer solvents (dipropyl carbonate, isopropyl formate, mesitylene, and mixed xylene respectively) and organic phase enrichment solvents (isopropyl formate, methyl acetate, and ethyl acetate respectively) were used, and no sticky tar problem occurred. Filtration and separation became convenient. Through steps such as extraction with acidic aqueous solution, extraction with alkali solution, and precipitation by mixing, high-purity products could be obtained, achieving efficient separation and recovery of 8-hydroxyquinoline and the catalyst with high consistency. The dry yield of 8-hydroxyquinoline could reach up to 82%, with a content of 97.10%. The recovery rate of the organic phase enrichment solvent could reach 83.43%, and the recovery rate of the buffer solvent could reach 67.90%.

[0036] The buffer solutions all have a relatively high carbon content and large molecular weight. The solubility of these solvents in 8-hydroxyquinoline is general. If only relying on limited buffer solvents, it is difficult to completely adsorb the produced 8-hydroxyquinoline during extraction and mixing. Therefore, low-boiling organic phase enrichment solvents need to be added during cooling and mixing. Moreover, because of their low boiling points, they are also more convenient to recover during recycling, thus saving energy consumption.

[0037] The main components of the produced waste solids are potassium sulfate compounds and organic matter. There are two types of produced wastewater. One contains potassium, sulfur, and a relatively high amount of organic matter, and the other contains potassium and phosphorus but a relatively low amount of organic matter. These substances can be used as raw materials for fertilizer production, realizing the resource utilization of waste. The used organic solvents can also be recovered by centralized vacuum distillation and reused after drying. In addition, since the use and emission of harmful chemical substances are reduced during the process, the overall emission level is relatively low, meeting the requirements of green environmental protection.

[0038] The above are only examples of the present invention. Specific structures and common knowledge such as characteristics that are well-known in the art are not described in detail here. Those of ordinary skill in the art know all the common general technical knowledge in the technical field to which the invention belongs before the application date or the priority date, can know all the existing technologies in this field, and have the ability to apply conventional experimental means before this date. Those of ordinary skill in the art can, under the inspiration given in this application, improve and implement this solution in combination with their own abilities. Some typical well-known structures or well-known methods should not become obstacles for those of ordinary skill in the art to implement this application. It should be noted that for those skilled in the art, without departing from the structure of the present invention, several deformations and improvements can be made, which should also be regarded as the protection scope of the present invention, and these will not affect the implementation effect of the present invention and the practicality of the patent. The protection scope required by this application should be based on the content of its claims, and the specific implementation manners described in the specification can be used to interpret the content of the claims.

Claims

1. A preparation process of 8-hydroxyquinoline, characterized in that, It includes the following steps: Step 1: Add o-nitrophenol and o-aminophenol into a reaction vessel; Step 2: Add concentrated sulfuric acid and glycerol and heat; Step 3: After cooling, add an organic phase enrichment solvent and an alkaline solution; Step 4: After 8-hydroxyquinoline is adjusted and converted between the organic phase and the aqueous phase, adjust the pH value to precipitate the product.

2. The preparation process of 8-hydroxyquinoline according to claim 1, characterized in that: In Step 4, the specific adjustment and conversion of 8-hydroxyquinoline between the organic phase and the aqueous phase are as follows: Extract and separate to obtain the organic phase, add an acidic solution to the organic phase and then separate to obtain the aqueous phase.

3. The preparation process of 8-hydroxyquinoline according to claim 2, characterized in that: The organic phase enrichment solvent uses a carboxylic acid ester-based hydrophobic compound.

4. The preparation process of 8-hydroxyquinoline according to claim 3, characterized in that: The carboxylic acid ester-based hydrophobic compound uses one or more of ethyl acetate, propyl formate, isopropyl formate, methyl acetate, propyl acetate, isopropyl acetate, and isobutyl formate.

5. The preparation process of 8-hydroxyquinoline according to claim 4, characterized in that: In Step 1, add a hydrophobic compound with a boiling point higher than the reaction system temperature and a density lower than that of the reaction solution as a buffer solvent.

6. The preparation process of 8-hydroxyquinoline according to claim 5, characterized in that: The buffer solvent uses an alkylbenzene and / or an ester compound.

7. The preparation process of 8-hydroxyquinoline according to claim 6, characterized in that: The alkylbenzene uses one or more of mixed xylene, o-xylene, p-xylene, m-xylene, and trimethylbenzene.

8. The preparation process of 8-hydroxyquinoline according to claim 6, characterized in that: The ester compound uses one or more of diethyl carbonate, dipropyl carbonate, methyl oleate, isoamyl formate, and benzyl formate.

9. The preparation process of 8-hydroxyquinoline according to any one of claims 5-8, characterized in that: It also includes Step 5: Add an alkaline solution and an adsorbent to the organic phase finally separated in Step 4, separate the system by liquid separation, add an acidic solution to the aqueous phase to adjust the pH and then cool to recover o-nitrophenol, and concentrate the organic phase at low temperature and high temperature respectively to recover the organic phase enrichment solvent and the buffer solvent.

10. The preparation process of 8-hydroxyquinoline according to claim 9, characterized in that: The adsorbent uses one or more of diatomite, kaolin, activated carbon, and perlite.