Method for continuously preparing 2, 6-dimethylaniline

Abstract

The invention discloses a method for continuously preparing 2, 6-dimethylaniline, which comprises the following steps: S1, adding 2, 6-dimethyl nitrobenzene or an alcoholic solution of 2, 6-dimethyl nitrobenzene into a dissolving kettle for dissolving to form a material solution; s2, adding a catalyst required by reaction into the reactor, and introducing hydrogen for hydrogen activation; s3, pumping the material solution formed in the step S1 into the reactor in the step S2 through a metering pump, and simultaneously introducing hydrogen to perform hydrogenation reaction; and S4, distilling the reaction liquid flowing out of the reactor to obtain a 2, 6-dimethylaniline product. A continuous hydrogenation technology is utilized, and iron powder reduction is replaced by catalytic hydrogenation. The 2, 6-dimethylaniline product produced by the method disclosed by the invention is stable in quality and relatively high in purity and molar yield, the 2, 6-dimethylaniline product is industrially and continuously prepared, the obtained product is relatively high in purity, the generation of byproducts is reduced, and the reaction is safe and environment-friendly.

Description

Technical Field

[0001] The invention relates to the technical field of preparation of 2,6-dimethylaniline, in particular to a method for continuously preparing 2,6-dimethylaniline. Background Art

[0002] 2,6-Dimethylaniline is a light yellow liquid, insoluble in water, soluble in ethanol and ether, with a boiling point of 216-217℃, a melting point of 10-12℃, and a density of 0.973g / cm3. 2,6-Dimethylaniline is an intermediate for pesticides, medicines, and veterinary drugs. In the pesticide industry, it is used to produce high-efficiency fungicides such as metalaxyl, furalaxyl, furamide, furamide, bensulfuron, and chloranthate, and high-efficiency and low-toxic selective herbicides such as butachlor, teredo (dimethochlor), and imidazole; in the pharmaceutical industry, it is used to produce anesthetic drugs such as lidocaine hydrochloride, bupivacaine hydrochloride, trocaine hydrochloride, and dujuansu. In addition, it is also the raw material for the production of veterinary drugs such as jingsongling.

[0003] Existing technology adopts 2,6-dimethylnitrobenzene to reduce, and iron powder and hydrochloric acid are used to reduce step by step in the past, iron powder is gradually added to 2,6-dimethylnitrobenzene and dilute hydrochloric acid solution, refluxes for 30min after adding, cools, then adds sodium carbonate to neutralize, adds water to distill to obtain oily solution, separates, and the oil layer is dried to obtain product. And the o-toluidine alkylation method is adopted abroad to produce 2,6-xylidine, namely, o-toluidine and methanol are used as raw materials, reacts under certain pressure in the presence of catalyst. In this reaction, in addition to the main product 2,6-xylidine, there are also many by-products, wherein 2,3-xylidine is similar to 2,6-xylidine in structure, similar in physical properties, and has a smaller boiling point difference, and separation is more difficult. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a method for continuously preparing 2,6-dimethylaniline, so as to realize industrial continuous preparation of 2,6-dimethylaniline products with high purity.

[0005] The technical solution adopted by the present invention to solve the above technical problem is: a method for continuously preparing 2,6-dimethylaniline, comprising the following steps: S1, adding 2,6-dimethylnitrobenzene or an alcohol solution of 2,6-dimethylnitrobenzene into a dissolving kettle for dissolution to form a material solution; S2, adding the catalyst required for the reaction into the reactor and introducing hydrogen for hydrogen activation; S3, pumping the material solution formed in step S1 into the reactor of step S2 through a metering pump, and introducing hydrogen gas at the same time to carry out a hydrogenation reaction; S4. The reaction liquid flowing out of the reactor is distilled to obtain 2,6-dimethylaniline product.

[0006] Preferably, in step S1, the alcohol solution of 2,6-dimethylnitrobenzene is a mixed solution of 2,6-dimethylnitrobenzene and methanol, and the material ratio (volume ratio) in the material solution is: 2,6-dimethylnitrobenzene: methanol = 1:0-10.

[0007] Preferably, in step S2, the catalyst is Raney nickel; and the temperature during hydrogen activation in the reactor is 180-250°C.

[0008] Preferably, the reactor includes but is not limited to a spiral plate reactor or a fixed bed reactor.

[0009] Preferably, in step S3, the flow rate of the gas entering the reactor is 50 to 800 times the flow rate of the liquid entering the reactor.

[0010] Preferably, in step S3, during the hydrogenation reaction, the reaction temperature of the reactor is 70-150° C., and the pressure of the reactor is 0.5-5 MPa.

[0011] Preferably, a gas-liquid mixer is arranged on the top of the reactor, the hydrogen in the hydrogen storage tank enters the gas inlet of the gas-liquid mixer after passing through the gas flowmeter, the material solution in the dissolving kettle enters the preheating module after passing through the metering pump and the liquid flowmeter, the preheating module outputs the heated material solution to the liquid inlet of the gas-liquid mixer, the outlet of the gas-liquid mixer is connected to the inner cavity of the reactor, the reaction liquid flowing out of the reactor enters the cooling device through the back pressure valve, the cooling device outputs the cooled reaction liquid after cooling, the cooled reaction liquid enters the gas-liquid separation tank, the gas separated by the gas-liquid separation tank is sent to the gas collecting tank through the condenser, and the liquid separated by the gas-liquid separation tank enters the product receiving tank.

[0012] Preferably, the temperature of the preheating module is controlled by a first temperature control device, and the temperature of the reactor is controlled by a second temperature control device.

[0013] The beneficial effects of the present invention are as follows: the present invention utilizes continuous hydrogenation technology and utilizes catalytic hydrogenation to replace iron powder reduction, and 2,6-dimethylnitrobenzene is catalytically hydrogenated in a reactor in the presence of a catalyst.

[0014] The 2,6-dimethylaniline product produced by the method of the invention has stable quality, high product purity and high molar yield, and can realize industrial continuous preparation of 2,6-dimethylaniline products with high product purity, reduce the generation of by-products, and ensure safe and environmentally friendly reactions. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1It is a schematic diagram of the connection between the reactor and other equipment used in the method for continuously preparing 2,6-dimethylaniline of the present invention; Among them: 1. dissolving kettle; 2. metering pump; 3. liquid flow meter; 4. preheating module; 5. gas-liquid mixer; 6. reactor; 7. hydrogen storage tank; 8. gas flow meter; 9. back pressure valve; 10. cooling device; 11. gas-liquid separation tank; 12. condenser; 13. product receiving kettle; 14. first temperature control device; 15. second temperature control device. DETAILED DESCRIPTION

[0016] The present invention will now be described in further detail in conjunction with the accompanying drawings and preferred embodiments. These drawings are simplified schematic diagrams, which only illustrate the basic structure of the present invention in a schematic manner, and therefore only show the components related to the present invention.

[0017] like Figure 1 As shown, a method for continuously preparing 2,6-dimethylaniline comprises the following steps: S1, adding 2,6-dimethylnitrobenzene or an alcohol solution of 2,6-dimethylnitrobenzene into a dissolving kettle 1 to dissolve and form a material solution; S2, adding the catalyst required for the reaction into the reactor 6 and introducing hydrogen for hydrogen activation; S3, pumping the material solution formed in step S1 into the reactor 6 of step S2 through the metering pump 2, and introducing hydrogen gas at the same time to carry out a hydrogenation reaction; S4. The reaction liquid flowing out of the reactor 6 is distilled to obtain a 2,6-dimethylaniline product.

[0018] Specifically, in an optional implementation, in step S1, the alcohol solution of 2,6-dimethylnitrobenzene is a mixed solution of 2,6-dimethylnitrobenzene and methanol, and the material ratio (volume ratio) in the material solution is: 2,6-dimethylnitrobenzene: methanol = 1:0-10.

[0019] Specifically, in an optional embodiment, in step S2, the catalyst is Raney nickel; and the temperature during hydrogen activation in reactor 6 is 180-250°C.

[0020] Specifically, in an optional embodiment, the reactor 6 includes but is not limited to a spiral plate reactor or a fixed bed reactor.

[0021] Specifically, in an optional embodiment, in step S3 , the flow rate of the gas entering the reactor 6 is 50 to 800 times the flow rate of the liquid entering the reactor 6 .

[0022] Specifically, in an optional embodiment, in the step S3, during the hydrogenation reaction, the reaction temperature of the reactor 6 is 70-150° C., and the pressure of the reactor 6 is 0.5-5 MPa.

[0023] like Figure 1 As shown, a gas-liquid mixer 5 is arranged on the top of the reactor 6, and the hydrogen in the hydrogen storage tank 7 enters the gas inlet of the gas-liquid mixer 5 after passing through the gas flow meter 8, and the material solution in the dissolving kettle 1 enters the preheating module 4 after passing through the metering pump 2 and the liquid flow meter 3, and the preheating module 4 outputs the heated material solution to the liquid inlet of the gas-liquid mixer 5, and the outlet of the gas-liquid mixer 5 is connected to the inner cavity of the reactor 6, and the reaction liquid flowing out of the reactor 6 enters the cooling device 10 through the back pressure valve 9, and the cooling device 10 outputs the cooled reaction liquid after cooling, and the cooled reaction liquid enters the gas-liquid separation tank 11, and the gas separated from the gas-liquid separation tank 11 passes through the condenser 12 to the gas collection tank, and the liquid separated from the gas-liquid separation tank 11 enters the product receiving tank 13. The temperature of the preheating module 4 is controlled by the first temperature control device 14, and the temperature of the reactor 6 is controlled by the second temperature control device 15.

[0024] In the method for continuously preparing 2,6-dimethylaniline of the present invention, step S1 and step S2 can be performed in any order and can be performed simultaneously, or step S1 or step S2 can be performed first, and after both step S1 and step S2 are completed, step S3 can be performed. Specific embodiment 1:

[0026] S1. Add 1L of 2,6-dimethylnitrobenzene and 5L of methanol to the dissolving vessel 1 and stir to dissolve to form a material solution; S2. 500 g of Raney nickel was added to the reactor 6, the temperature was raised to 200 ° C, and hydrogen was introduced for activation for 8 h; S3. The material solution was introduced into the reactor 6 at a flow rate of 120 ml / min, and hydrogen was introduced at a flow rate of 72 L / min into the reactor 6, and the hydrogen pressure was 0.9 MPa; the reactor 6 temperature was 100 ° C, and the reactor 6 pressure was 0.9 MPa; S4. The reaction liquid flowing out of the reactor 6 was subjected to gas-liquid separation at 120 ml / min; S5. The separated solution is distilled to obtain 2,6-dimethylaniline product. The purity of the 2,6-dimethylaniline product is 99.1% and the molar yield is 99%. Specific embodiment 2:

[0028] S1. Add 1L of 2,6-dimethylnitrobenzene and 10L of methanol to the dissolving vessel 1 and stir to dissolve to form a material solution; S2. 500 g of Raney nickel was added to the reactor 6, the temperature was raised to 250 ° C, and hydrogen was introduced for activation for 8 h; S3. The material solution was injected into the reactor 6 at a flow rate of 240 ml / min, and hydrogen was introduced at a flow rate of 192 L / min into the reactor 6, and the hydrogen pressure was 2 MPa; the reactor 6 temperature was 130 ° C, and the reactor 6 pressure was 5 MPa; S4. The reaction liquid flowing out of the reactor 6 was subjected to gas-liquid separation at 120 ml / min; S5. The separated solution is distilled to obtain 2,6-dimethylaniline product. The purity of the 2,6-dimethylaniline product is 98.1% and the molar yield is 98%. Specific embodiment 3:

[0030] S1. Add 1L of 2,6-dimethylnitrobenzene and 1L of methanol to the dissolving vessel 1 and stir to dissolve to form a material solution; S2. 500 g of Raney nickel was added to the reactor 6, the temperature was raised to 220 ° C, and hydrogen was introduced for activation for 8 h; S3. The material solution was injected into the reactor 6 at a flow rate of 50 ml / min, and hydrogen was introduced at a flow rate of 7.5 L / min into the reactor 6, and the hydrogen pressure was 5 MPa; the reactor 6 temperature was 130 ° C, and the reactor 6 pressure was 5 MPa; S4. The reaction liquid flowing out of the reactor 6 was subjected to gas-liquid separation at 120 ml / min; S5. The separated solution is distilled to obtain 2,6-dimethylaniline product. The purity of 2,6-dimethylaniline product is 98.5%, and the molar yield is 98.2%. Specific embodiment 4:

[0032] S1. Add 100L of 2,6-dimethylnitrobenzene to the dissolving tank 1 and set aside; S2. 50 kg of Raney nickel was added to the reactor 6, the temperature was raised to 200 ° C, and hydrogen was introduced for activation for 8 h; S3. The material solution was injected into the reactor 6 at a flow rate of 30 ml / min, and hydrogen was introduced at the same time. The hydrogen flow rate was injected into the reactor 6 at a flow rate of 18 L / min, and the hydrogen pressure was 0.7 MPa; the reactor 6 was reacted at a temperature of 100 ° C, and the reactor 6 pressure was 0.7 MPa; S4. The reaction liquid flowing out of the reactor 6 was subjected to gas-liquid separation at 30 ml / min; S5. The separated solution is distilled to obtain 2,6-dimethylaniline product. The purity of the 2,6-dimethylaniline product is 99.3%, and the molar yield is 99.1%.

[0033] Specific embodiments 1-3 use a P2 model reactor, the capacity of which matches the capacity of the materials used in specific embodiments 1-3. Specific embodiment 4 uses a P4 model reactor, the capacity of which matches the capacity of the materials used in specific embodiment 4.

[0034] The present invention utilizes continuous hydrogenation technology and utilizes catalytic hydrogenation instead of iron powder reduction, and 2,6-dimethylnitrobenzene is catalytically hydrogenated in the presence of a catalyst in a reactor 6. The 2,6-dimethylaniline product produced by the method of the present invention has stable quality, high product purity and molar yield, and realizes industrial continuous preparation of 2,6-dimethylaniline products with high product purity, reduces the generation of by-products, and has safe and environmentally friendly reactions.

[0035] The above description only describes the specific implementation mode of the present invention. Various examples do not limit the essential content of the present invention. After reading the description, ordinary technicians in the relevant technical field can modify or deform the specific implementation mode described above without departing from the essence and scope of the invention.

Claims

1. A method for continuously preparing 2,6-dimethylaniline, characterized in that: The steps include: S1, adding 2,6-dimethylnitrobenzene or an alcohol solution of 2,6-dimethylnitrobenzene into a dissolving kettle (1) to dissolve and form a material solution; S2, adding the catalyst required for the reaction into the reactor (6) and introducing hydrogen for hydrogen activation; S3, pumping the material solution formed in step S1 into the reactor (6) in step S2 through a metering pump (2), while introducing hydrogen gas to carry out a hydrogenation reaction; S4. The reaction liquid flowing out of the reactor (6) is distilled to obtain 2,6-dimethylaniline product.

2. A method for continuously preparing 2,6-dimethylaniline according to claim 1, characterized in that: In the step S1, the alcohol solution of 2,6-dimethylnitrobenzene is a mixed solution of 2,6-dimethylnitrobenzene and methanol, and the material ratio (volume ratio) in the material solution is: 2,6-dimethylnitrobenzene: methanol = 1:0-10.

3. A method for continuously preparing 2,6-dimethylaniline according to claim 1, characterized in that: In step S2, the catalyst is Raney nickel; and the temperature during hydrogen activation in the reactor (6) is 180-250°C.

4. A method for continuously preparing 2,6-dimethylaniline according to claim 1, characterized in that: The reactor (6) includes but is not limited to a spiral plate reactor or a fixed bed reactor.

5. A method for continuously preparing 2,6-dimethylaniline according to claim 1, characterized in that: In step S3, the flow rate of the gas entering the reactor (6) is 50 to 800 times the flow rate of the liquid entering the reactor (6).

6. A method for continuously preparing 2,6-dimethylaniline according to claim 1, characterized in that: In the step S3, during the hydrogenation reaction, the reaction temperature of the reactor (6) is 70 to 150° C., and the pressure of the reactor (6) is 0.5 to 5 MPa.

7. A method for continuously preparing 2,6-dimethylaniline according to claim 1, characterized in that: A gas-liquid mixer (5) is arranged on the top of the reactor (6); the hydrogen in the hydrogen storage tank (7) enters the gas inlet of the gas-liquid mixer (5) after passing through a gas flow meter (8); the material solution in the dissolving kettle (1) enters the preheating module (4) after passing through a metering pump (2) and a liquid flow meter (3); the preheating module (4) outputs the heated material solution to the liquid inlet of the gas-liquid mixer (5); the outlet of the gas-liquid mixer (5) is connected to the inner cavity of the reactor (6); the reaction liquid flowing out of the reactor (6) enters the cooling device (10) through a back pressure valve (9); the cooling device (10) outputs the cooled reaction liquid after cooling; the cooled reaction liquid enters the gas-liquid separation tank (11); the gas separated by the gas-liquid separation tank (11) passes through a condenser (12) to a gas collecting tank; the liquid separated by the gas-liquid separation tank (11) enters the product receiving tank (13).

8. A method for continuously preparing 2,6-dimethylaniline according to claim 7, characterized in that: The temperature of the preheating module (4) is controlled by a first temperature control device (14), and the temperature of the reactor (6) is controlled by a second temperature control device (15).

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