Method for synthesizing p-nitro trifluoromethoxybenzene through tubular reaction in super-subcritical fluid

Abstract

The invention discloses a method for synthesizing p-nitro trifluoromethoxybenzene by tubular reaction in super-subcritical fluid, which comprises the following steps: continuously performing nitration reaction on raw materials trifluoromethoxybenzene and a nitrating agent in a super / subcritical fluid environment through a tubular reactor to generate a trifluoromethoxynitrobenzene product. According to the method disclosed by the invention, the nitrification process is enhanced by utilizing the supercritical / subcritical fluid, so that the mass transfer and heat transfer efficiency is high, the raw material trifluoromethoxybenzene is nearly completely converted, the selectivity of the product trifluoromethoxynitrobenzene is high, meanwhile, the acid consumption in the nitrification process is greatly reduced, and the technological process is greener and more efficient.

Description

Technical Field

[0001] This invention belongs to the field of fine chemical synthesis and relates to a method for the continuous synthesis of p-nitrotrifluoromethoxybenzene via tubular reaction in a supercritical / subcritical fluid. Background Technology

[0002] p-Nitrotrifluoromethoxybenzene is an important fine chemical intermediate. Through hydrogenation, it can synthesize p-trifluoromethoxyaniline. As a fluorinated organic intermediate, p-trifluoromethoxyaniline plays a special role in the pharmaceutical and dye industries, and can be used to prepare pesticides and pharmaceutical products such as fipronil, fluorocyanuric acid polyester, flufenoxuron, carbendazim, and thiamethoxam. With the continuous development of downstream products such as pesticides, pharmaceuticals, and liquid crystal materials, the demand for p-nitrotrifluoromethoxybenzene is increasing year by year, indicating a very broad prospect and development space.

[0003] Currently, the industrial synthesis of p-nitrotrifluoromethoxybenzene mainly uses trifluoromethoxybenzene as a raw material and employs an intermittent process of adding mixed acid under low-temperature conditions. This process generates a large amount of waste acid, is time-consuming, and has low production efficiency. Patents CN107266321B and CN119680488A disclose a method for nitrating trifluoromethoxybenzene using mixed acid as a nitrating agent by utilizing the efficient mass and heat transfer characteristics of a microchannel reactor. This method achieves a raw material conversion rate of over 99%, but the nitration process still uses mixed acid as the nitrating agent, resulting in excessive acid consumption and a large amount of waste acid and wastewater generated.

[0004] Based on the above analysis, it can be seen that the existing nitration process for trifluoromethoxybenzene has disadvantages such as large acid consumption and large wastewater generation. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a method for synthesizing p-nitrotrifluoromethoxybenzene via tubular reaction in a supersubcritical fluid, thereby solving problems such as the large amount of waste acid generated during the synthesis process of p-nitrotrifluoromethoxybenzene in existing technologies.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: A method for synthesizing p-nitrotrifluoromethoxybenzene via tubular reaction in a supercritical / subcritical fluid involves using a tubular reactor to mix trifluoromethoxybenzene and a nitrating agent in a supercritical / subcritical fluid environment to produce the trifluoromethoxynitrobenzene product.

[0007] The present invention also includes the following technical features: Specifically, the method includes the following steps: Supercritical / subcritical fluid is fed into a tubular reactor via a metering pump. Trifluoromethoxybenzene and the nitrifying agent are fed separately via metering pumps, mixed in a micro-mixer, and then preheated and continuously fed into the tubular reactor for nitration. The reacted material enters a receiving tank. After the reaction is complete, the pumps are stopped, the nitration reaction liquid is collected, and the nitration products are separated by phase separation. The products are further extracted from the waste acid, and the nitration products are combined, washed with water until neutral, to obtain the final product.

[0008] Specifically, in the tubular reactor, the nitration reaction temperature is controlled between 0 and 50°C, and the temperature is controlled by a constant temperature oil bath.

[0009] Specifically, in the nitration reaction, the tubular reactor is back-pressurized by a back pressure valve to bring the system pressure to supercritical pressure.

[0010] Specifically, the supercritical / subcritical fluid includes one or two of carbon dioxide fluid, sulfur hexafluoride, and carbon tetrafluoride.

[0011] Specifically, the nitrifying agent is nitric acid, dinitrogen pentoxide, or a mixture of dinitrogen pentoxide and nitric acid, and the molar amount of the nitrifying agent is 1.0-1.5 times that of the raw material trifluoromethoxybenzene.

[0012] Specifically, the nitration reaction pressure is 3.0-10.0 MPa.

[0013] Specifically, the tubular reactor has an inner diameter of 1.0-6.0 mm and a length of 1-10 m.

[0014] Specifically, when the nitrating agent is nitric acid, sulfur trioxide can be used as an auxiliary agent in the reaction system, and the amount of sulfur trioxide added is 5%-35% of the mass of the raw material trifluoromethoxybenzene.

[0015] Compared with the prior art, the present invention has the following technical effects: (I) This invention uses tubular reaction to continuously synthesize p-nitrotrifluoromethoxybenzene in supercritical / subcritical fluid, which enhances the mass and heat transfer effect of the trifluoromethoxybenzene nitration process, significantly improves the reaction efficiency, and achieves a conversion rate of 99.9% for the raw material trifluoromethoxybenzene and a selectivity of up to 93.5% for the main product p-nitrotrifluoromethoxybenzene.

[0016] (II) The supercritical / subcritical fluid-enhanced nitration method constructed in this invention is applied to the nitration of trifluoromethoxybenzene. Compared with the traditional mixed acid nitration process, the amount of acid used is significantly reduced, and the amount of waste acid and wastewater generated is low.

[0017] As can be seen from the above analysis, the method for continuous synthesis of p-nitrotrifluoromethoxybenzene by tubular reaction in supercritical / subcritical fluid of the present invention reduces the amount of nitrating agent used, improves the preparation efficiency of p-nitrotrifluoromethoxybenzene, and the process is more green and efficient. Detailed Implementation

[0018] This invention provides a method for synthesizing p-nitrotrifluoromethoxybenzene via a tubular reaction in a supercritical / subcritical fluid environment. The method employs a tubular reactor to mix trifluoromethoxybenzene and a nitrating agent in a supercritical / subcritical fluid environment to undergo a nitration reaction, thereby generating the trifluoromethoxynitrobenzene product.

[0019] The method includes the following steps: Supercritical / subcritical fluid is fed into a tubular reactor via a metering pump. Trifluoromethoxybenzene and the nitrifying agent are fed separately via metering pumps, mixed in a micro-mixer, and then preheated and continuously fed into the tubular reactor for nitration. The reacted material enters a receiving tank. After the reaction is complete, the pumps are stopped, the nitration reaction liquid is collected, and the nitration products are separated by phase separation. The products are further extracted from the waste acid, and the nitration products are combined, washed with water until neutral, to obtain the final product.

[0020] In the tubular reactor, the nitration reaction temperature is controlled at 0~50℃, and the temperature is controlled by a constant temperature oil bath.

[0021] In the nitration reaction, the tubular reactor is back-pressurized by a back pressure valve to bring the system pressure to supercritical pressure.

[0022] Supercritical / subcritical fluids include one or two of the following: carbon dioxide fluid, sulfur hexafluoride, and carbon tetrafluoride.

[0023] The nitrifying agent is a mixture of nitric acid, dinitrogen pentoxide, or dinitrogen pentoxide-nitric acid, and the molar amount of the nitrifying agent is 1.0-1.5 times that of the raw material trifluoromethoxybenzene.

[0024] The nitration reaction pressure is 3.0-10.0 MPa.

[0025] The tubular reactor has an inner diameter of 1.0-6.0 mm and a length of 1-10 m.

[0026] When the nitrating agent is nitric acid, sulfur trioxide can be used as an auxiliary agent in the reaction system. The amount of sulfur trioxide added is 5%-35% of the mass of the raw material trifluoromethoxybenzene.

[0027] It should be noted that, unless otherwise specified, all raw materials used in this invention are those known in the prior art.

[0028] The nitration reaction of trifluoromethoxybenzene was carried out in a supercritical / subcritical nitration tubular reactor, which was designed and constructed in-house.

[0029] The following are specific embodiments of the present invention. It should be noted that the present invention is not limited to the following specific embodiments. All equivalent modifications made based on the technical solutions of this application fall within the protection scope of the present invention.

[0030] Example 1: The tubular reactor used had an inner diameter of 3 mm and a length of 1.5 m. Nitrogen gas was introduced into the tubular reactor system for an airtightness test. After passing the airtightness test, the tubular reactor was evacuated, and the reactor temperature was raised to 32°C. Carbon dioxide fluid was introduced through a metering pump. After the system pressure reached 7.5 MPa, the carbon dioxide fluid metering pump flow rate was reduced to 0.2 ml / min. Then, the following feeds were continuously introduced through metering pumps: sulfur trioxide flow rate at 0.03 ml / min, fuming nitric acid flow rate at 0.07 ml / min, and trifluoromethoxybenzene flow rate at 0.16 ml / min. After 2 h, the nitration reaction liquid was collected from the receiving tank, and the nitration products were separated by phase separation. The nitration products were washed with water until neutral, and samples were analyzed by gas chromatography. The results are shown in Table 1.

[0031] Example 2: The tubular reactor used had an inner diameter of 3 mm and a length of 1.5 m. Nitrogen gas was introduced into the tubular reactor system for an airtightness test. After passing the airtightness test, the tubular reactor was evacuated, and the reactor temperature was raised to 32°C. Carbon dioxide fluid was introduced through a metering pump. After the system pressure reached 7.5 MPa, the carbon dioxide fluid metering pump flow rate was reduced to 0.2 ml / min. Then, the feed was continuously introduced through metering pumps. The flow rates of dinitrogen pentoxide-nitric acid (molar ratio 1:1) were 0.08 ml / min and trifluoromethoxybenzene were 0.16 ml / min. After 2 h, the nitration reaction liquid was collected from the receiving tank, and the nitration product was separated by phase separation. The nitration product was washed with water until neutral, and samples were analyzed by gas chromatography. The results are shown in Table 1.

[0032] Example 3: The tubular reactor used had an inner diameter of 3 mm and a length of 1.5 m. Nitrogen gas was introduced into the tubular reactor system, and an airtightness test was conducted. After passing the airtightness test, the tubular reactor was evacuated, and the reactor temperature was raised to 20°C. Carbon tetrafluoride fluid was introduced through a metering pump. After the system pressure reached 4.0 MPa, the metering pump flow rate of carbon tetrafluoride fluid was reduced to 0.2 ml / min. Then, the feed was continuously introduced through metering pumps. The flow rates of dinitrogen pentoxide-nitric acid (molar ratio 1:1) were 0.08 ml / min, and the flow rates of trifluoromethoxybenzene were 0.16 ml / min. After 2 h, the nitration reaction liquid was collected from the receiving tank, and the nitration product was separated by phase separation. The nitration product was washed with water until neutral, and samples were analyzed by gas chromatography. The results are shown in Table 1.

[0033] Example 4: The tubular reactor used had an inner diameter of 1.5 mm and a length of 6 m. Nitrogen gas was introduced into the tubular reactor system, and an airtightness test was conducted. After passing the airtightness test, the tubular reactor was evacuated, and the reactor temperature was raised to 20°C. Carbon dioxide fluid was introduced through a metering pump. After the system pressure reached 4.0 MPa, the carbon dioxide fluid metering pump flow rate was reduced to 0.2 ml / min, and then the feed was continuously introduced through metering pumps. The flow rates of dinitrogen pentoxide-nitric acid (molar ratio 1:1) were 0.08 ml / min, and the flow rate of trifluoromethoxybenzene was 0.16 ml / min. After 2 h, the nitration reaction liquid was collected from the receiving tank, and the nitration product was separated by phase separation. The nitration product was washed with water until neutral, and samples were analyzed by gas chromatography. The results are shown in Table 1.

[0034] Example 5: The tubular reactor used had an inner diameter of 3 mm and a length of 1.5 m. Nitrogen gas was introduced into the tubular reactor system for an airtightness test. After passing the airtightness test, the tubular reactor was evacuated, and the reactor temperature was raised to 46℃. Sulfur hexafluoride fluid was introduced through a metering pump. After the system pressure reached 4.0 MPa, the sulfur hexafluoride fluid metering pump flow rate was reduced to 0.2 ml / min. Then, the feed was continuously introduced through metering pumps at flow rates of 0.01 ml / min for sulfur trioxide, 0.07 ml / min for fuming nitric acid, and 0.16 ml / min for trifluoromethoxybenzene. After 2 h, the nitration reaction liquid was collected from the receiving tank, and the nitration products were separated by phase separation. The nitration products were washed with water until neutral, and samples were analyzed by gas chromatography. The results are shown in Table 1.

[0035] Example 6: The tubular reactor used had an inner diameter of 3 mm and a length of 1.5 m. Nitrogen gas was introduced into the tubular reactor system for an airtightness test. After passing the airtightness test, the tubular reactor was evacuated, and the reactor temperature was raised to 46℃. Sulfur hexafluoride fluid was introduced through a metering pump. After the system pressure reached 4.0 MPa, the sulfur hexafluoride fluid metering pump flow rate was reduced to 0.2 ml / min. Then, the following feeds were continuously introduced through metering pumps: sulfur trioxide flow rate at 0.03 ml / min, nitrogen pentoxide-nitric acid (molar ratio 1:1) flow rate at 0.08 ml / min, and trifluoromethoxybenzene flow rate at 0.16 ml / min. After 2 h, the nitration reaction liquid was collected from the receiving tank, and the nitration products were separated by phase separation. The nitration products were washed with water until neutral, and samples were analyzed by gas chromatography. The results are shown in Table 1.

[0036] Example 7: The nitration method in this embodiment is basically the same as that in Example 1, except that sulfur trioxide is not introduced into the system.

[0037] The nitration products of the above embodiments were washed with water until neutral, and samples were analyzed by gas chromatography. The results are shown in Table 1.

[0038] Table 1. Conversion and selectivity results of nitration reactions in Examples 1-7

Claims

1. A method for synthesizing p-nitrotrifluoromethoxybenzene via tubular reaction in a supercritical fluid, characterized in that, A tubular reactor is used to mix trifluoromethoxybenzene and a nitrating agent in a supercritical / subcritical fluid environment to produce trifluoromethoxynitrobenzene product.

2. The method for synthesizing p-nitrotrifluoromethoxybenzene via tubular reaction in a supercritical fluid as described in claim 1, characterized in that, The method includes the following steps: Supercritical / subcritical fluid is fed into a tubular reactor via a metering pump. Trifluoromethoxybenzene and the nitrifying agent are fed separately via metering pumps, mixed in a micro-mixer, and then preheated and continuously fed into the tubular reactor for nitration. The reacted material enters a receiving tank. After the reaction is complete, the pumps are stopped, the nitration reaction liquid is collected, and the nitration products are separated by phase separation. The products are further extracted from the waste acid, and the nitration products are combined, washed with water until neutral, to obtain the final product.

3. The method for synthesizing p-nitrotrifluoromethoxybenzene via tubular reaction in a supercritical fluid as described in claim 2, characterized in that, In the tubular reactor, the nitration reaction temperature is controlled at 0~50℃, and the temperature is controlled by a constant temperature oil bath.

4. The method for synthesizing p-nitrotrifluoromethoxybenzene via tubular reaction in a supercritical fluid as described in claim 2, characterized in that, In the nitration reaction, the tubular reactor is back-pressurized by a back pressure valve to bring the system pressure to supercritical pressure.

5. The method for synthesizing p-nitrotrifluoromethoxybenzene via tubular reaction in a supercritical fluid as described in claim 2, characterized in that, The supercritical / subcritical fluid includes one or two of carbon dioxide fluid, sulfur hexafluoride, and carbon tetrafluoride.

6. The method for synthesizing p-nitrotrifluoromethoxybenzene via a tubular reaction in a supercritical fluid as described in claim 2, characterized in that, The nitrifying agent is nitric acid, dinitrogen pentoxide, or a mixture of dinitrogen pentoxide and nitric acid, and the molar amount of the nitrifying agent is 1.0-1.5 times that of the raw material trifluoromethoxybenzene.

7. The method for synthesizing p-nitrotrifluoromethoxybenzene via tubular reaction in a supercritical fluid as described in claim 2, characterized in that, The nitration reaction pressure is 3.0-10.0 MPa.

8. The method for synthesizing p-nitrotrifluoromethoxybenzene via tubular reaction in a supercritical fluid as described in claim 2, characterized in that, The tubular reactor has an inner diameter of 1.0-6.0 mm and a length of 1-10 m.

9. The method for synthesizing p-nitrotrifluoromethoxybenzene via a tubular reaction in a supercritical fluid as described in claim 6, characterized in that, When the nitrating agent used is nitric acid, sulfur trioxide can be used as an auxiliary agent in the reaction system. The amount of sulfur trioxide added is 5%-35% of the mass of the raw material trifluoromethoxybenzene.

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