Continuous preparation method of 2-hydroxy-benzonitrile
A continuous method using a tower overflow reactor with controlled photochemical reactions and hydrolysis effectively produces high-purity salicylonitrile, addressing inefficiencies in existing methods by reducing by-products and costs, and enhancing safety and scalability.
Patent Information
- Application Number
- CN202311762378.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-12-20
- Publication Date
- 2024-12-06
AI Technical Summary
Existing methods for producing salicylonitrile suffer from issues such as poor mass transfer and heat transfer effects, leading to inefficiencies in the production of by-products and high production costs, and the lack of suitable industrial scale production of high-quality, high-purity, high-purity, high-purity, and the lack of suitable methods for producing salicylonitrile, which is a key intermediate for the synthesis of azoxystrobin, a highly effective broad-spectrum methoxyacrylate fungicide.
A continuous preparation method using a tower overflow reactor with a jacket, spherical and tubular portions, and a light pipe for phosgene introduction, allowing for controlled photochemical reactions at 120-150°C, followed by hydrolysis and crystallization to produce salicylonitrile with high purity and yield, eliminating the need for fillers and reducing wastewater and costs.
The method achieves high product yield and purity, reduces production costs, minimizes by-product formation, and enhances safety through controlled heat and mass transfer, making it suitable for industrial production.
Smart Images
Figure CN119080639A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of chemical industry and relates to a continuous preparation method of salicylic nitrile, in particular to a method for continuously preparing salicylic nitrile by a phosgene process tower overflow. Background Art
[0002] Salicylonitrile, also known as o-hydroxybenzonitrile, is an important intermediate for pesticides, fragrances, liquid crystal materials, etc., especially a key intermediate for the synthesis of azoxystrobin, a new type of highly effective broad-spectrum methoxyacrylate fungicide. Azoxystrobin is priced at 250,000 yuan / ton, with sales reaching $500 million in 2020, and the patent expired in 2010. The domestic production scale of the intermediate o-hydroxybenzonitrile is small, the quality is not high, the cost is high, and various synthetic routes generate a large number of by-products. Therefore, high-quality, low-cost, and large-scale production of salicylonitrile is a problem that needs to be solved in response to market requirements.
[0003] At present, the mainstream route of industrial production is the o-hydroxybenzamide dehydration method for synthesizing salicylic nitrile, with o-hydroxybenzamide as raw material, using phosgene, triphosgene or thionyl chloride as dehydrating agent, but these dehydrating agents have the problems of strong toxicity, strong corrosiveness, large environmental pollution, and large production safety risk. Chinese patent literature CN11264584A discloses a method for preparing salicylic nitrile by a continuous method of o-hydroxybenzamide, wherein the organic solution of o-hydroxybenzamide is preheated and enters a reaction tower filled with filler, and after reacting under heating conditions, the outflowing steam is collected after cooling to obtain a solution of salicylic nitrile product. A large amount of fillers are installed in the tower of this method, and the filler needs to be regularly processed and recycled, and impurities are high, and phosgene consumption is high. The reaction solution needs nitrogen stripping, and the amount of wastewater generated is large, and solvent consumption is high, which does not meet the requirements of clean production, and the product yield is low. Chinese patent document CN110041229A discloses a method for continuously preparing salicylonitrile by the o-hydroxybenzamide phosgene method. The method is to synthesize salicylonitrile products in a continuous flow manner in a microchannel reactor, and has the characteristics of precise controllable reaction conditions, high safety and short reaction time. However, the method has the defects of high impurities, low yield, high production cost and high equipment requirements, and is not suitable for industrial production.
[0004] Compared with the batch synthesis method of salicylic nitrile and other continuous processes, the mass transfer and heat transfer effects of the tower overflow continuous process are improved to the greatest extent, effectively inhibiting the formation of two major by-products. The formation mechanism of the two by-products is shown in the following formula: Influence of mass transfer and heat transfer effects: Formula (1)
[0005] Impurity 1: Formation mechanism of casalan Excess phosgene: Formula (2)
[0006] Impurity 2: Carbonate formation mechanism There are two main defects in the existing synthesis method: S1. Poor mass transfer and heat transfer directly affect the production of salicylon, the main impurity of salicylon. After formation, salicylon is not easy to break and will remain in the product, affecting product quality; S2. Excessive phosgene is produced during the reaction, impurity carbonate is easily formed, and a large amount of alkaline water is required for destruction treatment. In addition, salicylon is easily hydrolyzed under alkaline conditions, resulting in a large amount of wastewater in the production process and a low product yield. Summary of the invention
[0007] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a continuous preparation method of salicylic nitrile with high product yield and content, excellent mass transfer and heat transfer effects, high production efficiency, high degree of automation, high safety, no filler, little wastewater and low cost. The method is suitable for industrial production and has industrial value.
[0008] In order to solve the above technical problems, the present invention adopts the following technical solutions.
[0009] A continuous preparation method of salicylic nitrile comprises the following steps: S1, mixing the raw material o-hydroxybenzamide with an organic solvent and heating to dissolve, to obtain an organic solution of o-hydroxybenzamide, and storing at a constant temperature; S2, preparing a tower overflow reactor, the tower overflow reactor comprising a jacket, the jacket comprising an upper spherical portion and a lower tubular portion, the spherical portion being provided with an inner wall, an outer wall, and a material inlet and a phosgene inlet penetrating the inner wall and the outer wall, the tubular portion being provided with a reaction tube, the upper end of the reaction tube extending into the spherical portion to form an overflow trough, the phosgene inlet being provided with a light pipe, the light pipe passing through the phosgene inlet and extending to the reaction tube; the organic solution of o-hydroxybenzamide is continuously introduced into the overflow trough through the material inlet to overflow into the reaction tube, the phosgene is continuously introduced into the reaction tube through the light pipe, and a photochemical reaction is carried out at a temperature of 120° C. to 150° C., wherein the molar ratio of o-hydroxybenzamide to phosgene is 1:1 to 1.01, and the residence time of the photochemical reaction liquid in the tower overflow reactor is controlled to be 0.5 h to 3.5 h; S3, continuously delivering the photochemical reaction liquid obtained in step S2 from the bottom of the tower overflow reactor to the hydrolysis kettle, and continuously introducing water into the hydrolysis kettle for continuous hydrolysis, cooling and crystallizing the obtained organic phase after overflowing the hydrolysis kettle, filtering and drying the obtained crystal slurry to obtain a salicylic nitrile product.
[0010] In the above-mentioned continuous preparation method of salicylonitrile, preferably, in step S2, the flow rate of the organic solution of o-hydroxybenzamide is controlled at 1 g / min to 200 g / min, and the flow rate of the phosgene is controlled at 1 g / min to 150 g / min.
[0011] In the above-mentioned continuous preparation method of salicylonitrile, preferably, in step S2, the flow rate of the organic solution of o-hydroxybenzamide is controlled at 1 g / min to 50 g / min, and the flow rate of the phosgene is controlled at 1 g / min to 30 g / min.
[0012] In the above-mentioned continuous preparation method of salicylonitrile, preferably, in step S1, the mass ratio of o-hydroxybenzamide to organic solvent is 1:1-5, and the temperature of heating and dissolving is 120° C.-150° C. More preferably, the temperature of heating and dissolving is the same as the temperature of the photochemical reaction in step S2.
[0013] In the above-mentioned continuous preparation method of salicylonitrile, preferably, in step S1, the organic solvent includes one or more of chlorobenzene, dichlorobenzene, trichlorobenzene, xylene, mesitylene and sulfolane.
[0014] In the above-mentioned continuous preparation method of salicylonitrile, preferably, in step S3, the mass of the water entering the hydrolysis kettle is 10% to 20% of the mass of the photochemical reaction liquid in the hydrolysis kettle, the temperature of the cooling crystallization is 5°C to 10°C, and the drying is reduced pressure drying.
[0015] In the above-mentioned continuous preparation method of salicylonitrile, preferably, the material of the jacket is ceramic, the material of the reaction tube is Hastelloy alloy, the material of the light tube is glass, the diameter of the spherical part is 800mm~1200mm, the diameter of the tubular part is 650mm~1000mm, the diameter of the spherical part is larger than the diameter of the tubular part, and the height of the tubular part is 1.6m~3.5m.
[0016] In the above-mentioned continuous preparation method of salicylonitrile, preferably, the lower end of the reaction tube is connected to the hydrolysis kettle; the upper end of the reaction tube is trumpet-shaped, the upper end diameter is in the range of 50mm to 200mm, and the height from the upper end of the reaction tube to the spherical part is 10mm to 30mm; the diameter of the light-through tube is 10mm to 30mm, and the length of the light-through tube is 850mm to 1300mm.
[0017] In the above-mentioned continuous preparation method of salicylonitrile, preferably, a heat transfer oil inlet is provided on the bottom side of the tubular portion, and a heat transfer oil outlet is provided on the outer wall of the spherical portion; the spherical portion is also provided with a spare feed port penetrating the inner wall and the outer wall.
[0018] In the above-mentioned continuous preparation method of salicylonitrile, preferably, the content of the salicylonitrile product is ≥99.5%, and the yield is ≥98%.
[0019] Compared with the prior art, the advantages of the present invention are: (1) The method of the present invention adopts a tower overflow reactor and a matching process to overcome the problems of uneven heat dissipation distribution and large mass transfer fluctuations in the system, large temperature fluctuations in the photochemical reaction, and the addition of fillers, and the process is simple and easy to operate. In the method of the present invention, the reaction liquid can completely form a thin film in the tower overflow reactor without the need to add fillers. The photochemical reaction is carried out in a continuous manner in the reactor. The reactor's unique strong heat dissipation effect can make the o-hydroxybenzamide solution heated evenly, so that the temperature of the photochemical reaction can be well controlled at 120-150°C, and the photochemical reaction can be completed quickly without generating by-products, which has no effect on product quality, and effectively solves the problem of the easy formation of two impurities in the prior art. At the same time, the mixture is effectively mixed and forms a liquid film on the inner surface of the reactor. The formation of the film makes the system have a good mass transfer effect, the photochemical reaction is sufficient, and the formation of impurities is suppressed. Since the photochemical reaction is carried out completely, the product content and yield are maintained within a stable range, with a content of ≥99.5% (HPLC) and a yield of ≥98%.
[0020] (2) In the method for preparing salicylonitrile of the present invention, there is no filler in the tower overflow reactor, and no filler recovery treatment is required. At the same time, the back-mixing phenomenon of materials in the tower is eliminated, so that the excess phosgene is small, the impurity carbonate is not easy to form, the use of alkaline water in the post-treatment process is reduced, the production wastewater and production costs are reduced, and the clean production of the product is achieved.
[0021] (3) In the method for preparing salicylic nitrile of the present invention, a tower overflow reactor is used to reduce the online liquid holding amount of the photochemical reaction materials and improve production safety.
[0022] (4) In the method for preparing salicylic nitrile of the present invention, the residence time of the reactants in the tower overflow reactor is 0.5-3.5 h, the photochemical reaction time is short, and the continuous reaction operation is convenient.
[0023] (5) In the method for preparing salicylic nitrile of the present invention, the reaction solvent adopts one or more organic solvents, thereby avoiding the influence of water in the raw materials, making the feeding more convenient and the material ratio more accurate. BRIEF DESCRIPTION OF THE DRAWINGS
[0024] Figure 1 It is a schematic diagram of the structure of the tower overflow reactor and the hydrolysis kettle in Examples 1-6 of the present invention.
[0025] Figure 2 It is a schematic diagram of the partially enlarged structure of the tower overflow reactor in Examples 1-6 of the present invention.
[0026] Legend: 1. Jacket; 2. Spherical part; 3. Tubular part; 4. Material inlet; 5. Phosgene inlet; 6. Reaction tube; 7. Overflow tank; 8. Light pipe; 9. Hydrolysis kettle; 10. Heat transfer oil inlet; 11. Heat transfer oil outlet; 12. Alternate feed port. DETAILED DESCRIPTION
[0027] The present invention is further described below in conjunction with the accompanying drawings and specific preferred embodiments of the specification, but the protection scope of the present invention is not limited thereby. The materials and instruments used in the following examples are all commercially available. In each example, the purity of the product is detected by high performance liquid chromatography (HPLC), and the yield of the product is calculated after HPLC measures the external standard content of salicylamide in the solution.
[0028] In the following embodiments, the structures of the tower overflow reactor and the hydrolysis kettle are shown as follows: Figure 1 , 2 As shown, the tower overflow reactor includes a jacket 1, and the jacket 1 includes an upper spherical portion 2 and a lower tubular portion 3. The spherical portion 2 is provided with an inner wall, an outer wall, a material inlet 4 penetrating the inner wall and the outer wall, and a phosgene inlet 5 penetrating the inner wall and the outer wall. A reaction tube 6 is provided in the tubular portion 3, and the upper end of the reaction tube 6 extends into the spherical portion 2 to form an overflow trough 7. A light pipe 8 is provided in the phosgene inlet 5, and the light pipe 8 extends through the phosgene inlet 5 to the reaction tube 6. The material enters through the material inlet 4, flows along the inner wall of the spherical portion 2 to the overflow trough 7, and then overflows into the reaction tube 6, flows downward along the tube wall of the reaction tube 6, and reacts with the phosgene in the reaction tube 6. The lower end of the reaction tube 6 extends through the tubular portion 3 to the hydrolysis kettle 9, and is connected to the hydrolysis kettle 9, and is used to send the photochemical reaction liquid to the hydrolysis kettle 9. The hydrolysis kettle 9 is provided with a water inlet for continuous water inlet (the water inlet pipeline is at Figure 1 The hydrolysis kettle 9 can also be connected to a crystallization kettle to allow the organic phase obtained by hydrolysis to overflow into the crystallization kettle for cooling and crystallization (the crystallization kettle is in Figure 1 (not shown in the figure, which is a conventional design).
[0029] In the tower overflow reactor, the material of the jacket 1 is ceramic, the material of the reaction tube 6 is Hastelloy alloy, the material of the light pipe 8 is glass, the diameter of the spherical part 2 is 1000 mm, the diameter of the tubular part 3 is 800 mm, and the height of the tubular part 3 is 2.5 m. The upper end of the reaction tube 6 is in a bell-mouth shape, the upper end diameter is in the range of 80 mm to 120 mm, and the height from the upper end of the reaction tube 6 to the spherical part 2 is 15 mm; the diameter of the light pipe 8 is 15 mm, and the length of the light pipe 8 is 1100 mm. Preferably, the outer diameter of the phosgene inlet 5 is equivalent to the diameter of the light pipe 8.
[0030] In the tower overflow reactor, a heat transfer oil inlet 10 is provided on the bottom side of the tubular part 3, and a heat transfer oil outlet 11 is provided on the outer wall of the spherical part 2, so that the heat transfer oil can flow in the jacket 1 for heating the reaction. The spherical part 2 is also provided with a spare feed port 12 that penetrates the inner wall and the outer wall.
[0031] Example 1 A continuous preparation method of salicylic nitrile of the present invention comprises the following steps: S1. In a reactor equipped with a stirrer, dissolve 100 g (0.72 mol, 99%) of o-hydroxybenzamide in 500 g of dry chlorobenzene, heat to 130°C, stir and dissolve to obtain a chlorobenzene solution of o-hydroxybenzamide, and store at a constant temperature.
[0032] S2, heat transfer oil is introduced into the jacket 1 of the tower overflow reactor, and after the temperature is raised to 130° C., 600 g of the prepared chlorobenzene solution of o-hydroxybenzamide enters through the material inlet 4, is continuously introduced into the overflow groove 7 along the inner wall of the spherical portion 2, and overflows from the overflow groove 7 into the reaction tube 6, and phosgene is continuously introduced into the reaction tube 6 through the light pipe 8, the molar ratio of o-hydroxybenzamide to phosgene is 1:1, the reaction temperature is maintained at 130° C., the flow rate of the chlorobenzene solution of o-hydroxybenzamide is 10 g / min, the flow rate of phosgene is 1.19 g / min, and the residence time of the photochemical reaction solution is controlled to be 0.5 h.
[0033] S3, the photochemical reaction liquid obtained in step S2 is continuously sent to the hydrolysis kettle 9 from the bottom of the tower overflow reactor, and water is added to the hydrolysis kettle 9 at the same time, and the mass of the water is 10% of the mass of the photochemical reaction liquid. The obtained organic phase overflows from the hydrolysis kettle 9 to the crystallization kettle, and is cooled to 5-10°C for crystallization, and the crystal slurry is filtered and dried under reduced pressure at 55°C to obtain an off-white solid salicylonitrile product with a content of 99.5%, a yield of 98.1%, and an impurity of 0.
[0034] Example 2 A continuous preparation method of salicylic nitrile of the present invention comprises the following steps: S1. In a reactor equipped with a stirrer, dissolve 100 g (0.72 mol, 99%) of o-hydroxybenzamide in 500 g of dry chlorobenzene, heat to 130°C, stir and dissolve to obtain a chlorobenzene solution of o-hydroxybenzamide, and store at a constant temperature.
[0035] S2, heat transfer oil is introduced into the jacket 1 of the tower overflow reactor, and after the temperature is raised to 140°C, 600g of the prepared chlorobenzene solution of o-hydroxybenzamide is continuously introduced into the overflow groove 7 along the inner wall of the spherical portion 2 through the material inlet 4, and overflows from the overflow groove 7 to the reaction tube 6, and phosgene is continuously introduced into the reaction tube 6 through the light pipe 8, the molar ratio of o-hydroxybenzamide to phosgene is 1:1, the reaction temperature is maintained at 140°C, the flow rate of the chlorobenzene solution of o-hydroxybenzamide is 50g / min, the flow rate of phosgene is 5.95g / min, and the residence time of the photochemical reaction solution is controlled to be 3.5h.
[0036] S3, the photochemical reaction liquid obtained in step S2 is continuously sent to the hydrolysis kettle 9 from the bottom of the tower overflow reactor, and water is added to the hydrolysis kettle 9 at the same time, and the mass of the water is 10% of the mass of the photochemical reaction liquid. The obtained organic phase overflows from the hydrolysis kettle 9 to the crystallization kettle, and is cooled to 5-10°C for crystallization, and the crystal slurry is filtered and dried under reduced pressure at 55°C to obtain an off-white solid salicylonitrile product with a content of 99.7%, a yield of 98.9%, and an impurity of 0.
[0037] Example 3 A continuous preparation method of salicylic nitrile of the present invention comprises the following steps: S1. In a reactor equipped with a stirrer, dissolve 100 g (0.72 mol, 99%) of o-hydroxybenzamide in 500 g of dry dichlorobenzene, heat to 150°C, stir and dissolve to obtain a dichlorobenzene solution of o-hydroxybenzamide, and store at a constant temperature.
[0038] S2, heat transfer oil is introduced into the jacket 1 of the tower overflow reactor, and after the temperature is raised to 150° C., 600 g of the prepared dichlorobenzene solution of o-hydroxybenzamide and phosgene are continuously introduced into the tower overflow reactor from the top material inlet 4 and the light pipe 8, respectively, the molar ratio of o-hydroxybenzamide to phosgene is 1:1, the reaction temperature is maintained at 150° C., the flow rate of the dichlorobenzene solution of o-hydroxybenzamide is 40 g / min, the flow rate of phosgene is 4.76 g / min, and the residence time of the photochemical reaction solution is controlled to be 2.0 h.
[0039] S3, the photochemical reaction liquid obtained in step S2 is continuously sent to the hydrolysis kettle 9 from the bottom of the tower overflow reactor, and water is continuously fed into the hydrolysis kettle 9, and the mass of the water fed is 10% of the mass of the photochemical reaction liquid. The obtained organic phase overflows from the hydrolysis kettle 9 to the crystallization kettle, and is cooled to 5-10°C for crystallization, and the crystal slurry is filtered and dried under reduced pressure at 55°C to obtain an off-white solid salicylonitrile product with a content of 99.9%, a yield of 98.9%, and 0 impurity of casalan.
[0040] Example 4 A continuous preparation method of salicylic nitrile of the present invention comprises the following steps: S1. In a reactor equipped with a stirrer, dissolve 100 g (0.72 mol, 99%) of o-hydroxybenzamide in 500 g of dry mesitylene, heat to 138°C, stir and dissolve to obtain a mesitylene solution of o-hydroxybenzamide, and store at a constant temperature.
[0041] S2. Heat transfer oil is introduced into the jacket 1 of the tower overflow reactor. After the temperature is raised to 138° C., 600 g of the prepared mesitylene solution of o-hydroxybenzamide and phosgene are continuously introduced into the tower overflow reactor from the top material inlet 4 and the light pipe 8, respectively. The molar ratio of o-hydroxybenzamide to phosgene is 1:1. The reaction temperature is maintained at 138° C., the flow rate of the mesitylene solution of o-hydroxybenzamide is 30 g / min, and the flow rate of the phosgene is 3.57 g / min. The residence time of the photochemical reaction solution is controlled to be 1.5 h.
[0042] S3, the photochemical reaction liquid obtained in step S2 is continuously sent to the hydrolysis kettle 9 from the bottom of the tower overflow reactor, and water is fed into the hydrolysis kettle 9 at the same time, and the mass of the water fed is 10% of the mass of the photochemical reaction liquid. The obtained organic phase overflows from the hydrolysis kettle 9 to the crystallization kettle, and is cooled to 5-10°C for crystallization, and the crystal slurry is filtered and dried under reduced pressure at 55°C to obtain an off-white solid salicylonitrile product with a content of 99.9%, a yield of 99.1%, and an impurity of 0.
[0043] Example 5 A continuous preparation method of salicylic nitrile of the present invention comprises the following steps: S1. In a reactor equipped with a stirrer, dissolve 100 g (0.72 mol, 99%) of o-hydroxybenzamide in 500 g of dry xylene, heat to 120°C, stir and dissolve to obtain a xylene solution of o-hydroxybenzamide, and store at a constant temperature.
[0044] S2, heat transfer oil is introduced into the jacket 1 of the tower overflow reactor, and after the temperature is raised to 120° C., 600 g of the prepared xylene solution of o-hydroxybenzamide and phosgene are continuously introduced into the tower overflow reactor from the material inlet 4 and the light pipe 8, respectively, the molar ratio of o-hydroxybenzamide to phosgene is 1:1, the reaction temperature is maintained at 120° C., the flow rate of the xylene solution of o-hydroxybenzamide is 25 g / min, the flow rate of phosgene is 2.97 g / min, and the residence time of the photochemical reaction solution is controlled to be 1.0 h.
[0045] S3, the photochemical reaction liquid obtained in step S2 is continuously sent to the hydrolysis kettle 9 from the bottom of the tower overflow reactor, and water is added to the hydrolysis kettle 9 at the same time, and the mass of the water is 10% of the mass of the photochemical reaction liquid. The obtained organic phase overflows from the hydrolysis kettle 9 to the crystallization kettle, and is cooled to 5-10°C for crystallization, and the crystal slurry is filtered and dried under reduced pressure at 55°C to obtain an off-white solid salicylonitrile product with a content of 99.8%, a yield of 99.2%, and an impurity of 0.
[0046] Example 6 A continuous preparation method of salicylic nitrile of the present invention comprises the following steps: S1. In a reactor equipped with a stirrer, dissolve 100 g (0.72 mol, 99%) of o-hydroxybenzamide in 500 g of dry sulfolane, heat to 135°C and stir to dissolve to obtain a sulfolane solution of o-hydroxybenzamide, which is then stored at a constant temperature.
[0047] S2, heat transfer oil is introduced into the jacket 1 of the tower overflow reactor, and after the temperature is raised to 135° C., 600 g of the prepared sulfolane solution of o-hydroxybenzamide and phosgene are continuously introduced into the tower overflow reactor from the material inlet 4 and the light pipe 8, respectively, the molar ratio of o-hydroxybenzamide to phosgene is 1: 1.01, the reaction temperature is maintained at 135° C., the flow rate of the sulfolane solution of o-hydroxybenzamide is 45 g / min, and the flow rate of phosgene is 5.4 g / min, and the residence time of the photochemical reaction solution is controlled to be 2.5 h.
[0048] S3, the photochemical reaction liquid obtained in step S2 is continuously sent to the hydrolysis kettle 9 from the bottom of the tower overflow reactor, and water is added to the hydrolysis kettle 9 at the same time, and the mass of the water is 10% of the mass of the photochemical reaction liquid. The obtained organic phase overflows from the hydrolysis kettle 9 to the crystallization kettle, and is cooled to 5-10°C for crystallization, and the crystal slurry is filtered and dried under reduced pressure at 55°C to obtain an off-white solid salicylonitrile product with a content of 99.8%, a yield of 99.3%, and an impurity of 0.
[0049] The above is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as above in the preferred embodiment, it is not used to limit the present invention. Any technician familiar with the art can make many possible changes and modifications to the technical solution of the present invention by using the methods and technical contents disclosed above without departing from the spirit and technical solution of the present invention, or modify it into an equivalent embodiment of equivalent changes. Therefore, any simple modification, equivalent replacement, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention, still fall within the scope of protection of the technical solution of the present invention.
Claims
1. A continuous preparation method of salicylic nitrile, characterized in that: The following steps are involved: S1, mixing the raw material o-hydroxybenzamide with an organic solvent and heating to dissolve, to obtain an organic solution of o-hydroxybenzamide, and storing at a constant temperature; S2. Prepare a tower overflow reactor, the tower overflow reactor comprising a jacket (1), the jacket (1) comprising an upper spherical portion (2) and a lower tubular portion (3), the spherical portion (2) being provided with an inner wall, an outer wall, and a material inlet (4) and a phosgene inlet (5) penetrating the inner wall and the outer wall, the tubular portion (3) being provided with a reaction tube (6), the upper end of the reaction tube (6) extending into the spherical portion (2) to form an overflow trough (7), the phosgene inlet (5) being provided with a light pipe (8), the light pipe (8) passing through The phosgene inlet (5) extends to the reaction tube (6); the organic solution of o-hydroxybenzamide is continuously introduced into the overflow tank (7) through the material inlet (4) to overflow into the reaction tube (6); phosgene is continuously introduced into the reaction tube (6) through the light pipe (8); and a photochemical reaction is carried out at a temperature of 120° C. to 150° C., wherein the molar ratio of o-hydroxybenzamide to phosgene is 1:1 to 1.01, and the residence time of the photochemical reaction liquid in the tower overflow reactor is controlled to be 0.5 h to 3.5 h; S3, the photochemical reaction liquid obtained in step S2 is continuously sent from the bottom of the tower overflow reactor to the hydrolysis kettle (9), and water is continuously introduced into the hydrolysis kettle (9) for continuous hydrolysis. The obtained organic phase overflows the hydrolysis kettle (9) and is then cooled and crystallized. The obtained crystal slurry is filtered and dried to obtain a salicylonitrile product.
2. The continuous preparation method of salicylic nitrile according to claim 1, characterized in that: In step S2, the flow rate of the organic solution of o-hydroxybenzamide is controlled at 1 g / min to 200 g / min, and the flow rate of the phosgene is controlled at 1 g / min to 150 g / min.
3. The continuous preparation method of salicylic nitrile according to claim 2, characterized in that: In step S2, the flow rate of the organic solution of o-hydroxybenzamide is controlled at 1 g / min to 50 g / min, and the flow rate of the phosgene is controlled at 1 g / min to 30 g / min.
4. The continuous preparation method of salicylic nitrile according to claim 1, characterized in that: In step S1, the mass ratio of o-hydroxybenzamide to the organic solvent is 1:1-5, and the temperature for heating and dissolving is 120°C-150°C.
5. The continuous preparation method of salicylic nitrile according to claim 1, characterized in that: In step S1, the organic solvent includes one or more of chlorobenzene, dichlorobenzene, trichlorobenzene, xylene, mesitylene and sulfolane.
6. The continuous preparation method of salicylic nitrile according to any one of claims 1 to 5, characterized in that: In step S3, the mass of the water entering the hydrolysis kettle (9) is 10% to 20% of the mass of the photochemical reaction liquid in the hydrolysis kettle (9), the temperature of the cooling crystallization is 5° C. to 10° C., and the drying is reduced pressure drying.
7. The continuous preparation method of salicylic nitrile according to any one of claims 1 to 5, characterized in that: The material of the jacket (1) is ceramic, the material of the reaction tube (6) is Hastelloy alloy, the material of the light tube (8) is glass, the diameter of the spherical part (2) is 800 mm to 1200 mm, the diameter of the tubular part (3) is 650 mm to 1000 mm, the diameter of the spherical part (2) is greater than the diameter of the tubular part (3), and the height of the tubular part (3) is 1.6 m to 3.5 m.
8. The continuous preparation method of salicylic nitrile according to claim 7, characterized in that: The lower end of the reaction tube (6) is connected to the hydrolysis kettle (9); the upper end of the reaction tube (6) is in a trumpet shape, the diameter of the upper end is in the range of 50 mm to 200 mm, and the height from the upper end of the reaction tube (6) to the spherical part (2) is 10 mm to 30 mm; the diameter of the light pipe (8) is 10 mm to 30 mm, and the length of the light pipe (8) is 850 mm to 1300 mm.
9. The continuous preparation method of salicylic nitrile according to claim 8, characterized in that: A heat transfer oil inlet (10) is provided on the bottom side of the tubular portion (3), and a heat transfer oil outlet (11) is provided on the outer wall of the spherical portion (2); the spherical portion (2) is also provided with a spare feed port (12) that penetrates the inner wall and the outer wall.
10. The continuous preparation method of salicylic nitrile according to any one of claims 1 to 5, characterized in that: The content of the salicylonitrile product is ≥99.5%, and the yield is ≥98%.