A method, reactor, and system for synthesizing salicylonitrile

Abstract

This invention belongs to the field of continuous multiphase catalytic synthesis of fine chemical products, specifically disclosing a two-stage fixed-bed continuous catalytic synthesis method for salicylnitrile (o-hydroxybenzonitrile). Using methyl salicylate and ammonia as reactants, the first stage fixed-bed reactor is loaded with a metal oxide catalyst, and the second stage fixed-bed reactor is loaded with a zeolite molecular sieve catalyst. Salicylicnitrile is synthesized continuously via gas-solid multiphase catalysis, resulting in high catalyst space-time yield, high production efficiency, and low waste.

Description

Technical Field

[0001] This invention belongs to the field of fine chemicals, specifically relating to a continuous multiphase catalytic synthesis method, reactor, and system for salicylates. Background Technology

[0002] Salicylic nitrile is an important intermediate, mainly used in the synthesis of methoxyacrylate fungicides such as pyraclostrobin and injectable drugs for hypertension and angina pectoris such as bunirol. It also has wide applications in the pharmaceutical, pesticide, dye, and liquid crystal material synthesis industries. Currently, the industrial synthesis of salicylic nitrile uses salicylamide as a reactant and phosgene or phosgene as a dehydrating agent to remove a mole of water from the salicylamide molecule, converting it into salicylic nitrile. This process generates a large amount of waste acid, waste gas, and wastewater. In recent years, the preparation of salicylonitrile using methyl salicylate, ammonia, or urea as raw materials via solid acid heterogeneous catalysis has been reported. This mainly employs atmospheric pressure gas-solid or pressurized liquid-solid two-phase fixed-bed reactors. Reported solid catalysts include supported boron phosphate (ZJ Kong, et al., Efficient preparation of salicylonitrile from methylsalicylate over supported boron phosphate catalyst in a continuous fixed bedreactor [J], Chemical Papers, 2021, 76, 1365-1375), aluminum phosphate solid acid (Chen Guanhu et al., Study on the preparation of salicylonitrile from methyl salicylate catalyzed by aluminum phosphate solid acid [J], Modern Chemical Industry, 2020, 40, 3: 143-151; CN 104549378A), and SYR-05 (Chen Erzhong et al., Green process for one-step synthesis of o-hydroxybenzonitrile from methyl salicylate [J], Pesticides, 2018, 57, 27: 870-872). However, these systems have relatively large catalyst loadings (~10 mL) and relatively low liquid hourly space velocities (0.18~0.3 h⁻¹). -1 The space-time yield of the catalyst was low (0.162~0.27 g). nitrile ·g cat -1 ·h -1 In addition, due to the large catalyst loading in the fixed-bed reactor, the particle gaps are small, and the products or carbon deposits can easily cause a large bed pressure drop, leading to bed blockage. Summary of the Invention

[0003] The purpose of this invention is to provide a novel continuous solid-phase catalytic synthesis method for salicylnitrile. This method uses methyl salicylate and ammonia as raw materials, and prepares salicylnitrile through ammonolysis and dehydration reactions in a two-stage fixed-bed reactor with two catalysts. This method has the advantages of readily available raw materials, safety, simple process, low waste, and high production efficiency.

[0004] Specifically, the present invention provides a method for the continuous catalytic synthesis of salicylnitrile, which includes using methyl salicylate and ammonia as reactants and synthesizing them through a two-stage gas-solid multiphase catalytic reaction.

[0005] Preferably, after the methyl salicylate is vaporized in the vaporization chamber, it is preheated together with nitrogen as the carrier gas and ammonia before the two-stage continuous gas-solid multiphase catalytic reaction is carried out.

[0006] Preferably, the first stage of the two-stage continuous gas-solid multiphase catalytic reaction is the ammonolysis of the ester to generate salicylamide; the second stage of the two-stage continuous gas-solid multiphase catalytic reaction is the dehydration of the salicylamide to generate salicylate.

[0007] Preferably, the temperature of the first stage reaction is 200-350 ºC; the temperature of the second stage reaction is 350-500ºC.

[0008] Preferably, the catalyst for the first stage reaction is a metal oxide catalyst; the catalyst for the second stage reaction is a zeolite molecular sieve catalyst.

[0009] Preferably, the metal oxide catalyst includes ZnO, CeO2, MgO, CuO, Fe2O3, TiO2 or ZrO2; the zeolite molecular sieve catalyst includes ZSM-5, USY, Beta, AIPO-5 or MCM-22.

[0010] Preferably, the method for continuous catalytic synthesis of salicylnitrile satisfiber ... (1) The pressure of the two-stage continuous gas-solid multiphase catalytic reaction is 1.013*10 -5 Pa; (2) The liquid flow rate of the methyl salicylate is 0.01-0.08 mL / min, the nitrogen flow rate is 15-80 mL / min, and the ammonia flow rate is 15-80 mL / min; (3) The molar ratio of ammonia to methyl salicylate is (2~8):1; (4) The liquid hourly space velocity of the methyl salicylate is 2.362-18.896 g·g. -1 ·h -1 ; (5) The total space velocity of the ammonia, vaporized methyl salicylate, and nitrogen is 6000-32000 mL·g. -1 ·h -1 .

[0011] Another aspect of the present invention provides a fixed-bed reactor for synthesizing salicylates, wherein the fixed-bed reactor is a two-stage fixed-bed reactor, comprising a reaction tube, which is divided into an upper reaction tube and a lower reaction tube; The upper reaction tube is filled with a metal oxide catalyst for the ammonolysis reaction of esters to produce salicylamide; The lower reaction tube is filled with a zeolite molecular sieve catalyst for the dehydration of salicylamide to produce salicylnitrile.

[0012] Preferably, the reactor outlet adopts a vapor-liquid-solid staged condensation separation, and the tail gas is treated by acidic solution absorption. The vapor-liquid-solid stepped condensation separation comprises three units: the first unit is protected by a heating jacket and the temperature is controlled at 250-350 ºC; the second unit is insulated with circulating water and the temperature is controlled at 50-80 ºC; and the third unit is low-temperature condensation and the temperature is controlled at 0-10 ºC. The exhaust gas includes ammonia and nitrogen.

[0013] A third aspect of this application provides a reaction system for synthesizing salicylnitrile, including the reactor described above, the reaction system further comprising: A pump, connected to the vaporization chamber, is used to deliver methyl salicylate into the vaporization chamber; The vaporization chamber, connected to the preheating furnace, is used for the vaporization of methyl salicylate. The vaporized methyl salicylate is carried into the preheating furnace by nitrogen as the carrier gas. The preheating furnace, connected to the fixed-bed reactor, is used to preheat ammonia, carrier gas nitrogen, and vaporized methyl salicylate, and then introduces them into the fixed-bed reactor.

[0014] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention provides a method for synthesizing salicylic acid via a continuous gas-solid multiphase catalytic reaction. This method is simple, operates under mild conditions, can be carried out at atmospheric pressure, and has high production efficiency, produces less waste, is environmentally friendly, and is safe to operate.

[0015] The catalyst used in the process provided by this invention is commercially available, has a high space-time yield, and is regenerable. Attached Figure Description

[0016] The following figures are for illustrative purposes only and are not intended to limit the scope of the invention, wherein: Figure 1The reaction system diagram for synthesizing salicylonite in this invention is shown, wherein 1-ammonia cylinder, 2-nitrogen cylinder, 3-methyl salicylate raw material tank, 4-pump, 5, 6-mass flow meters, 7-vaporization chamber, 8-preheating furnace, 9-two-stage fixed bed reactor, 10-first-stage unit, 11-second-stage unit, 12-tertiary unit. Figure 2 This invention relates to a two-stage fixed-bed reactor for the synthesis of salicylates; Figure 3 : Results of reaction performance in Example 1; Figure 4 Example 2: Reaction performance results; Figure 5 Example 3: Reaction performance results; Figure 6 Example 4: Reaction performance results; Figure 7 Example 5: Reaction performance results; Figure 8 Example 6: Reaction performance results; Figure 9 Example 7: Reaction performance results; Figure 10 Results of regeneration performance of ZnO and Beta catalysts; Figure 11 Space-time yield of salicylate over ZnO and Beta catalysts; Implementation

[0017] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, a detailed description of specific embodiments of this application is provided below. Many specific details are set forth in the following description to provide a thorough understanding of this application. However, this application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.

[0018] In this application, the technical features described in an open-ended manner include both closed technical solutions consisting of the listed features and open technical solutions that include the listed features.

[0019] The present invention provides a method for the continuous catalytic synthesis of salicylnitrile, which includes using methyl salicylate and ammonia as reactants and synthesizing them through a two-stage gas-solid multiphase catalytic reaction.

[0020] In some embodiments, after the methyl salicylate is vaporized, it is preheated together with nitrogen and ammonia using nitrogen as a carrier gas before undergoing the two-stage continuous gas-solid multiphase catalytic reaction. It can be understood that the vaporization temperature of the methyl salicylate is 220℃-250℃, slightly above its boiling point, and the vaporization takes place in the vaporization chamber 7. The methyl salicylate is pumped from the methyl salicylate raw material tank 3 to the vaporization chamber 7 via pump 4.

[0021] The methyl salicylate is carried by nitrogen as a carrier gas and preheated together with ammonia before undergoing the two-stage gas-solid multiphase catalytic reaction. The preheating temperature is 200℃-250℃, which keeps the ammonia, nitrogen, and vaporized methyl salicylate in a gaseous state and close to the reactor temperature to reduce the thermal effect of the bed. It can be understood that the preheating is carried out in preheating furnace 8.

[0022] In some embodiments, the first stage of the two-stage continuous gas-solid multiphase catalytic reaction is the ammonolysis of the ester to generate salicylamide; the second stage of the two-stage continuous gas-solid multiphase catalytic reaction is the dehydration of the salicylamide to generate salicylate.

[0023] In some embodiments, the liquid hourly space velocity (LHSV) of methyl salicylate is 2.362–18.896 g·g⁻¹. -1 ·h -1 The ammonia flow rate was 15-80 mL / min, the nitrogen flow rate was 15-80 mL / min, the liquid flow rate of salicylate was 0.01-0.08 mL / min, and the total space velocity (GHSV) of ammonia, vaporized methyl salicylate, and nitrogen was 6000-32000 mL·g. -1 ·h -1 ; In some embodiments, the molar ratio of ammonia to salicylate is 2:1 to 8:1. It is understood that the molar ratio of ammonia to salicylate can be 2:1, 3:1, 5:1, 7:1, or 8:1. In some embodiments, a mixture of methyl salicylate, ammonia, and nitrogen undergoes a first-stage gas-solid heterogeneous catalytic reaction and a second-stage gas-solid heterogeneous catalytic reaction sequentially, with the pressure of the first and second stages of the reaction being 1.013 × 10⁻⁶. -5 Pa; In some embodiments, the first stage of the two-stage gas-solid heterogeneous catalytic reaction is the ammonolysis of methyl salicylate to generate salicylamide, and the temperature of the first stage reaction is 200-350 ºC; the second stage of the two-stage gas-solid heterogeneous catalytic reaction is the dehydration of salicylamide to generate salicylate nitrile, and the temperature of the second stage reaction is 350-500 ºC.

[0024] In some embodiments, the catalyst for the first stage reaction is a metal oxide catalyst. The first stage involves ammonolysis, where the metal oxide activates ammonia molecules, promoting the S-reaction of ammonia with the carbonyl group of the ester. N2. Nucleophilic attack to generate amide. Optionally, the metal catalyst includes ZnO, MgO, CuO, Fe2O3, TiO2 or ZrO2, and methyl salicylate and ammonia are reacted to generate salicylamide under the action of a metal oxide catalyst; optionally, the metal catalyst is ZnO.

[0025] In some embodiments, the catalyst for the second stage reaction is a zeolite molecular sieve catalyst, and the second stage utilizes the acidity of the zeolite molecular sieve catalyst to dehydrate the amide. Optionally, the zeolite molecular sieve catalyst includes ZSM-5, USY, Beta, AIPO-5, or MCM-22, and salicylamide is converted into salicylic nitrile under the action of the zeolite molecular sieve catalyst; optionally, the zeolite molecular sieve catalyst is Beta.

[0026] Another aspect of the present invention provides a fixed-bed reactor for the continuous catalytic synthesis of salicylnitrile. The fixed-bed reactor is a two-stage fixed-bed reactor 9, which includes a reaction tube divided into an upper reaction tube and a lower reaction tube. The upper reaction tube is filled with a metal oxide catalyst for the ammonolysis reaction of the ester to generate salicylamide. The lower reaction tube is filled with a zeolite molecular sieve catalyst for the dehydration of salicylamide to generate salicylnitrile.

[0027] In some embodiments, the reactor outlet employs a vapor-liquid-solid stepped condensation separation, which includes three stages. The first stage, 10, is protected by a heating jacket, with the temperature controlled at 250-350 ºC, allowing the product to melt and flow out of the reaction tube, preventing reactor blockage. The second stage, 11, uses circulating water for insulation, with the temperature controlled at 50-80ºC, allowing solid products to precipitate and collecting the crude salicylates. The third stage, 12, is a low-temperature condensation stage, with the temperature controlled at 0-10 ºC, enabling vapor-liquid separation, with the gaseous component entering the tail gas absorption bottle. The tail gas is treated with an acidic solution; it is understood that the tail gas mainly includes ammonia, with nitrogen carrying a small amount of organic components. The acidic solution is understood to include dilute hydrochloric acid or dilute sulfuric acid.

[0028] A third aspect of the present invention provides a reaction system for the continuous synthesis of salicylnitrile, the reaction system further comprising a pump 4, a vaporization chamber 7, and a preheating furnace 8; In this invention, pump 4 is connected to vaporization chamber 7 via a pipeline, and pump 4 pressurizes methyl salicylate in methyl salicylate raw material tank 3 into vaporization chamber 7. The vaporization chamber 7 is connected to the preheating furnace. The temperature of the vaporization chamber 7 is 220℃-250℃, which is used for the vaporization of methyl salicylate. The vaporized methyl salicylate is carried into the preheating furnace 8 by nitrogen as the carrier gas. Preheater 8, connected to the fixed-bed reactor, is used to preheat ammonia, nitrogen, and vaporized methyl salicylate. Preheating keeps the ammonia, nitrogen, and methyl salicylate in a gaseous state, while simultaneously bringing them close to the reactor temperature, reducing the thermal effect on the bed. The temperature of preheater 8 is 200℃-250℃. The preheated mixed gas is then introduced into the reactor, with a total space velocity (HSV) of 6000-32000 mL·g. -1 ·h -1 . Example

[0029] A method for synthesizing salicylnitrile is provided, employing a continuous gas-solid multiphase catalytic process. Methyl salicylate and ammonia are used as raw materials. The liquid flow rate of methyl salicylate is 2.4 mL / h, the flow rate of ammonia is 3600 mL / h, the flow rate of nitrogen is 1800 mL / h, and 0.3 g of ZnO catalyst and 0.3 g of ZSM-5 catalyst are used. Under normal pressure, the temperature of the first stage reaction is controlled at 300 ºC, and the temperature of the second stage reaction is controlled at 450 ºC, with a reaction time of 8 h. The catalytic performance results are as follows: Figure 3 As shown. Example

[0030] The catalyst in the first stage reaction was replaced with TiO2, and the catalyst in the second stage reaction was replaced with USY catalyst. All other conditions were the same as in Example 1. The catalytic performance results are as follows: Figure 4 As shown. Example

[0031] The catalyst in the first stage reaction was replaced with CuO, and the catalyst in the second stage reaction was replaced with MCM-22 catalyst. All other conditions were the same as in Example 1. The catalytic performance results are as follows: Figure 5 As shown. Example

[0032] The catalyst for the first stage reaction was replaced with Fe2O3, and the catalyst for the second stage reaction was replaced with Beta. All other conditions remained the same as in Example 1. The catalytic performance results are as follows: Figure 6 As shown. Example

[0033] The catalyst in the first stage reaction was replaced with MgO, and the catalyst in the second stage reaction was replaced with AIPO-5. The catalytic performance results are as follows: Figure 7 As shown. Example

[0034] The first stage reaction temperature was adjusted to 320 °C, and the second stage reaction temperature was adjusted to 480 °C. Other conditions were the same as in Example 4. The catalytic performance results are as follows: Figure 8 As shown. Example

[0035] The catalyst in the first stage reaction was replaced with a ZnO catalyst, and the catalyst in the second stage reaction was replaced with a Beta catalyst. All other conditions were the same as in Example 6. The catalytic performance results are as follows: Figure 9 As shown. Example

[0036] The catalyst from Example 7 was removed after 30 h of reaction and calcined in air for 4 h. Then, the reactants were continuously introduced, and the catalytic performance after regeneration was as follows: Figure 10 As shown.

[0037] As shown in the attached figures, the combination of ZnO and Beta molecular sieve catalysts yielded the highest salicylnitrile yield, with the first-stage reactor temperature at 320 ºC and the second-stage reaction temperature at 480 ºC. Based on this catalyst combination and optimal reaction conditions, the space-time yield of salicylnitrile was calculated as follows: Figure 11 As shown (6.66 gg) cat h -1 The yield was significantly higher than the space-time yield reported in the literature for single-stage reaction processes (ZJ Kong, et al., Efficient preparation of salicylonitrile from methyl salicylate over supported boron phosphate catalyst in acontinuous fixed bed reactor [J], Chemical Papers, 2021, 76, 1365-1375; Chen Guanhu et al., Study on preparation of salicylonitrile from methyl salicylate by solid aluminum phosphate catalyst [J], Modern Chemical Industry, 2020, 40, 3: 143-151; CN104549378 A; Chen Erzhong et al., Green process for one-step synthesis of o-hydroxybenzonitrile from methyl salicylate [J], Pesticides, 2018, 57, 27: 870-872; The space-time yield reported in these literatures was lower, approximately 0.162~0.27 g). nitrile ·g cat -1 ·h -1 ).

Claims

1. A method for synthesizing salicylnitrile, characterized in that, It is synthesized by gas-solid multiphase catalytic reaction using methyl salicylate and ammonia as reactants in a two-stage continuous fixed-bed reactor. The first stage of the gas-solid multiphase catalytic reaction in the two-stage continuous fixed-bed reactor is the ammonolysis of the ester to generate salicylamide, and the second stage is the dehydration of the salicylamide to generate salicylic nitrile. The fixed-bed reactor includes a reaction tube, which is divided into an upper reaction tube and a lower reaction tube. The upper reaction tube is filled with a metal oxide catalyst, wherein the metal oxide is ZnO, MgO, CuO, Fe2O3 or TiO2, for the ammonolysis reaction of esters to generate salicylamide; The lower reaction tube is filled with a zeolite molecular sieve catalyst, which is ZSM-5, USY, Beta, AIPO-5 or MCM-22, for the dehydration of salicylamide to produce salicylonitrile.

2. The method for synthesizing salicylnitrile according to claim 1, characterized in that: After being vaporized, the methyl salicylate is preheated with nitrogen and ammonia before undergoing a gas-solid multiphase catalytic reaction in a two-stage continuous fixed-bed reactor.

3. The method for synthesizing salicylnitrile according to claim 1, characterized in that: The temperature of the first stage reaction is 200-350 ºC; The temperature of the second stage reaction is 350-500 ºC.

4. The method for synthesizing salicylnitrile according to claim 1, characterized in that, At least one of the following conditions must be met: (1) The pressure of the gas-solid multiphase catalytic reaction in the two-stage continuous fixed-bed reactor is 1.013 × 10⁻⁶. 5 Pa; (2) The liquid flow rate of the methyl salicylate is 0.01-0.08 mL / min, the nitrogen flow rate is 15-80 mL / min, and the ammonia flow rate is 15-80 mL / min; (3) The molar ratio of ammonia to methyl salicylate is (2-8):1; (4) The liquid hourly space velocity of the methyl salicylate is 2.362-18.896 g·g. -1 ·h -1 ; (5) The total space velocity of the ammonia, vaporized methyl salicylate, and nitrogen is 6000-32000 mL·g. -1 ·h -1 .

5. The method for synthesizing salicylnitrile according to claim 1, characterized in that, The reactor outlet employs a vapor-liquid-solid staged condensation separation, and the tail gas is treated by acidic solution absorption. The vapor-liquid-solid stepped condensation separation comprises three units: the first unit is protected by a heating jacket and the temperature is controlled at 250-350 ºC; the second unit is insulated with circulating water and the temperature is controlled at 50-80 ºC; and the third unit is low-temperature condensation and the temperature is controlled at 0-10 ºC. The exhaust gas includes ammonia.

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