Method for preparing N-cyanoethylaniline by continuous method

Abstract

The invention relates to the technical field of N-cyanoethylaniline, and particularly discloses a method for preparing N-cyanoethylaniline by a continuous method, which comprises the following steps: regulating aniline and acrylonitrile in a raw material intermediate tank by a regulating valve, continuously pumping into a tubular premixing device in front of a tower, mixing, feeding into a heat exchanger for preheating, and feeding into a tubular reactor; the reaction liquid is sprayed into a catalyst packing layer alternately at a first flow rate and a second flow rate through a redistributor above the tubular reactor, the reaction liquid is in full contact with the catalyst packing layer for a condensation reaction, the reaction temperature is 84-86 DEG C, the retention time is 4-8 h, and the reaction liquid flows out from the bottom of the tubular reactor and enters a product receiving tank; wherein the first flow velocity is 0.6-0.8 time of the second flow velocity. According to the invention, continuous production is realized, the production efficiency is high, the catalyst is alternately sprayed and flows into the catalyst packing layer at the first flow speed and the second flow speed through the redistributor above the pipe, the spraying is more uniform, the operation does not need to be paused, the operation is simpler, and the product purity is higher.

Description

Technical Field

[0001] The present invention relates to the field of methods for preparing N-cyanoethylaniline by a continuous process, and in particular to a method for preparing N-cyanoethylaniline by a continuous process. Background Art

[0002] Currently, N-cyanoethylaniline is an important chemical intermediate used in the synthesis of dye intermediates N-cyanoethyl-N-benzylaniline and N-cyanoethyl-N-acetoxyethylaniline.

[0003] Patent CN105037204 discloses a batch-process method for preparing N-cyanoethylaniline. Using hydrochloric acid as a catalyst, the reaction time is 20 hours at a temperature of 110°C. This method produces 1.2%-1.5% of the byproduct N,N-dicyanoethylaniline.

[0004] Li Jiaojuan et al. used water as solvent and aluminum chloride as catalyst. Although the reaction temperature was reduced (70-80°C), the reaction time of this method was as long as 24 hours, the production efficiency was low, and the catalyst could not be applied, making it unsuitable for industrial production.

[0005] Acrylonitrile has a low boiling point (77.3°C). Under existing processes, production requires multiple condensation stages to minimize losses. Furthermore, as the reaction time increases, aniline and acrylonitrile undergo oxidative side reactions, impacting product quality. At high temperatures, the resulting N-cyanoethylaniline further condenses with acrylonitrile to form N,N-dicyanoethylaniline. The aforementioned preparation method, using water as the solvent and ferric chloride, zinc chloride, aluminum chloride, and acetic acid or hydrochloric acid as catalysts, suffers from the production of large amounts of acidic metal salt-containing mother liquor, which is difficult to handle. Furthermore, the batch operation is complex, resulting in long production cycles, low production efficiency, poor reaction selectivity, and low product purity. Currently, the purity of commercially available products ranges from 93-94%. Summary of the Invention

[0006] In view of the above problems, the present invention proposes a continuous method for preparing N-cyanoethylaniline, which solves the defects of the existing batch operation, complicated reaction operation, long production cycle, low production efficiency, poor reaction selectivity and low product purity.

[0007] The technical solution adopted by the present invention is as follows:

[0008] A method for preparing N-cyanoethylaniline by continuous process, comprising: aniline and acrylonitrile in a raw material intermediate tank are continuously pumped into a tubular premixing device before a tower through a regulating valve, mixed, and then enter a heat exchanger for preheating, and then enter a tubular reactor;

[0009] Above the tube bundle, the redistributor alternately sprays into the catalyst packing layer at the first flow rate and the second flow rate. The reaction liquid fully contacts in the catalyst packing layer to undergo a condensation reaction. The reaction temperature is 84-86°C, and the residence time is 4-8 h. It flows out from the bottom of the tubular reactor and enters the product receiving tank. Among them, the first flow rate is 0.6-0.8 times that of the second flow rate.

[0010] The present invention realizes continuous production with high production efficiency. Above the tube bundle, the redistributor alternately sprays into the catalyst packing layer at the first flow rate and the second flow rate. Its spraying is more uniform, there is no need to pause for operation, its operation is simpler, and the product purity is higher.

[0011] Optionally, the catalyst is a supported composite catalyst, including an alumina-supported zinc and copper catalyst.

[0012] Optionally, its heat exchanger is preheated to 55-60°C.

[0013] Optionally, aniline enters the tubular mixer for mixing at a flow rate of 2.0-2.4 kg / h, and acrylonitrile enters at a flow rate of 1.26-1.30 kg / h.

[0014] Optionally, the tubular reactor includes a vertical tubular structure. A support plate is arranged at the lower part of the vertical tubular structure, and the supported composite catalyst is stacked on the support plate. A redistributor is arranged at the inlet above the vertical tubular structure.

[0015] Optionally, the top of the tubular reactor is provided with a first feed port. The redistributor includes a liquid inlet pipe communicating with the first feed port, and a plurality of liquid spraying pipes are uniformly installed on the outer periphery of the liquid inlet pipe.

[0016] Optionally, the liquid spraying pipe includes an inner pipe and an outer pipe. One end of the outer pipe close to the liquid inlet pipe is in a closed state. A plurality of first spraying holes are arranged on the inner pipe, and a plurality of second spraying holes are arranged on the outer pipe. The number of the second spraying holes is more than that of the first spraying holes, and at least part of the first spraying holes are directly opposite to the second spraying holes.

[0017] Optionally, a plurality of rotating shafts are rotatably installed on the inner pipe, a plurality of rotating blades are installed on the rotating shafts, a spraying hole is arranged at the end of the inner pipe, and a reflection cavity is arranged at the end of the outer pipe.

[0018] Optionally, the inner diameter of the first spraying hole gradually expands from the inside to the outside.

[0019] Optionally, an elastic arc-shaped guiding piece is arranged inside the second spraying hole, and the arc-shaped guiding piece extends obliquely upward from one side of the reflection cavity.

[0020] Beneficial effects

[0021] 1. The present invention realizes continuous production with high production efficiency. The redistributors above the tube bundle spray into the catalyst packing layer alternately at the first flow rate and the second flow rate. The spraying is more uniform, without the need to pause for operation, the operation is simpler, and the product purity is higher.

[0022] 2. In the present invention, the redistributors enter the tubular mixer and mix alternately at the first flow rate and the second flow rate, then enter the liquid inlet pipe through the first feed port, and then enter the inner pipe. A part of the liquid with a larger amount enters the area of the first spraying hole opposite to the outer pipe through the first spraying hole. During this process, it will impact the rotating blades on the rotating shaft. The rotation of the rotating blades causes the flow direction of the liquid to deflect, so that the flow direction and flow rate of the liquid flowing out of the first spraying hole and the second spraying hole both change. Another part of the liquid with a smaller amount enters the spraying hole and impacts the reflection cavity. The reflected liquid flows along the area between the inner pipe and the outer pipe, and is reflected by the arc-shaped guiding piece to impact and mix with the liquid sprayed out through the first spraying hole. With the continuous swinging of the arc-shaped guiding piece, the flow direction and flow rate of the liquid finally flowing out through the second spraying hole further change, making the spraying range of the liquid larger and reducing the spraying dead angle. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is the process flow diagram of the continuous method for preparing N-cyanoethylaniline in Example 1 of the present invention;

[0024] Figure 2 is the partial sectional view of the tubular reactor of the continuous method for preparing N-cyanoethylaniline in Example 3 of the present invention;

[0025] Figure 3 is the internal view of the redistributor of the continuous method for preparing N-cyanoethylaniline in Example 3 of the present invention;

[0026] Figure 4 is the sectional view of the redistributor of the continuous method for preparing N-cyanoethylaniline in Example 3 of the present invention.

[0027] Each reference numeral in the figure is as follows:

[0028] 1. Vertical tubular structure, 2. Support plate, 3. Redistributor, 4. First feed port, 5. Liquid inlet pipe, 6. Liquid spraying pipe, 7. Inner pipe, 8. Outer pipe, 9. First spraying hole, 10. Second spraying hole, 11. Rotating shaft, 12. Rotating blade, 13. Spraying hole, 14. Reflection cavity, 15. Arc-shaped guiding piece. DETAILED DESCRIPTION OF THE INVENTION

[0029] The following combines the drawings and embodiments to further describe in detail the specific embodiments of the present invention. The following examples are used to illustrate the present invention, but are not used to limit the scope of the present invention.

[0030] In the description of the present invention, unless otherwise specified, "a plurality of" means two or more; the orientation or positional relationship indicated by terms such as "upper", "lower", "left", "right", "inner", "outer", "front end", "rear end", "head", "tail", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be construed as a limitation to the present invention. In addition, terms such as "first", "second", "third", etc. are only used for descriptive purposes and cannot be construed as indicating or implying relative importance. In the description of the present invention, it should be noted that unless otherwise clearly specified and defined, the terms "connected" and "coupled" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, a direct connection, or an indirect connection through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0031] Example 1

[0032] The technical solution adopted by the present invention is as follows:

[0033] As Figure 1 shown, the present invention discloses a method for continuously preparing N-cyanoethyl aniline, which includes: continuously pumping aniline and acrylonitrile from the raw material intermediate tank into the tubular premixing device in front of the tower through a regulating valve for mixing, then entering a heat exchanger for preheating, and then entering a tubular reactor;

[0034] They are respectively sprayed into the catalyst packing layer at a first flow rate and a second flow rate alternately through a redistributor above the tube, and the reaction liquid fully contacts in the catalyst packing layer to undergo a condensation reaction. The reaction temperature is 84 °C, the residence time is 4 h, and it flows out from the bottom of the tubular reactor and enters the product receiving tank; wherein, the first flow rate is 0.6 times that of the second flow rate. The catalyst is a supported composite catalyst, specifically an alumina-supported zinc and copper catalyst.

[0035] Its heat exchanger is preheated to 55 °C. Among them, aniline enters the tubular mixer for mixing at a flow rate of 2.0 kg / h, and acrylonitrile enters at 1.26 kg / h.

[0036] Example 2

[0037] The technical solution adopted by the present invention is as follows:

[0038] The present invention discloses a method for continuously preparing N-cyanoethyl aniline, which includes: continuously pumping aniline and acrylonitrile from the raw material intermediate tank into the tubular premixing device in front of the tower through a regulating valve for mixing, then entering a heat exchanger for preheating, and then entering a tubular reactor;

[0039] The redistributor above alternately sprays into the catalyst packing layer at the first flow rate and the second flow rate. The reaction liquid fully contacts in the catalyst packing layer to undergo a condensation reaction. The reaction temperature is 86°C, and the residence time is 8 h. It flows out from the bottom of the tubular reactor and enters the product receiving tank. Among them, the first flow rate is 0.8 times that of the second flow rate. The catalyst is a supported composite catalyst, specifically an alumina-supported zinc and copper catalyst.

[0040] Its heat exchanger is preheated to 60°C. Among them, aniline enters the tubular mixer at a flow rate of 2.4 kg / h, and acrylonitrile enters at a flow rate of 1.30 kg / h for mixing.

[0041] The reactants of Example 1 and Example 2 are sampled and detected at regular intervals. The specific detection method: detected by a high-performance liquid chromatograph. Detection method: mobile phase, water: acetonitrile = 60:40, flow rate 0.8 mL / min, detection wavelength 254 nm, column temperature 30°C, and the chromatographic column is a C18 chromatographic column. The reactants of Example 1 and Example 2 are shown in Table 1.

[0042] Table 1 Detection data of the reactants of Example 1 and Example 2

[0043] Serial number Aniline N-Cyanoethyl aniline Dicyanoethyl aniline 1 0.35 97.5 0.52 2 0.41 97.1 0.46

[0044] The purity of the product obtained is 97.1 - 97.5%.

[0045] Comparative Example

[0046] Put 4 kg of water into a 10 L reaction kettle, start stirring, add 0.2 kg of hydrochloric acid, 2 kg of aniline, and 1.6 kg of acrylonitrile. Start heating, and heat up to 80 - 85°C in about 3 hours, keep warm for about 8 hours, then heat up to 105 - 110°C, keep warm for 12 hours. After the insulation time is up, turn on the negative pressure device, and maintain the temperature at about 50 - 75°C until no distillate is distilled out, then the product is obtained.

[0047] Detection data of the reactants of the comparative example

[0048] Serial number Aniline N-Cyanoethyl aniline Dicyanoethyl aniline 1 2.65 93.8 1.52

[0049] Example 3

[0050] As Figure 2 、 Figure 3 and Figure 4 shown, the present invention also discloses a tubular reactor, which includes a vertical tubular structure 1, a support plate 2 is arranged at the lower part of the vertical tubular structure, the supported composite catalyst is stacked on the support plate, and a redistributor 3 is arranged at the inlet above the vertical tubular structure.

[0051] The top of the tubular reactor is provided with a first feed inlet 4. The redistributor includes a liquid inlet pipe 5 communicating with the first feed inlet, and a plurality of liquid spray pipes 6 are evenly installed on the outer periphery of the liquid inlet pipe.

[0052] The liquid spray pipe includes an inner pipe 7 and an outer pipe 8. One end of the outer pipe close to the liquid inlet pipe is in a closed state. A plurality of first spraying holes 9 are provided on the inner pipe, and a plurality of second spraying holes 10 are provided on the outer pipe. The number of the second spraying holes is more than that of the first spraying holes, and at least part of the first spraying holes are opposite to the second spraying holes.

[0053] A plurality of rotating shafts 11 are rotatably installed on the inner pipe, a plurality of rotating blades 12 are installed on the rotating shafts, a spray hole 13 is provided at the end of the inner pipe, and a reflection cavity 14 is provided at the end of the outer pipe. The inner diameter of the first spraying holes gradually expands from inside to outside. An elastic arc-shaped guiding piece 15 is provided inside the second spraying holes, and the arc-shaped guiding piece extends obliquely upward from one side of the reflection cavity.

[0054] During the implementation of this embodiment, the redistributor alternately enters the tubular mixer for mixing at a first flow rate and a second flow rate, then enters the liquid inlet pipe through the first feed inlet, and then enters the inner pipe. A part of the more liquid enters the area of the first spraying holes opposite to the outer pipe through the first spraying holes. During this period, it will impact the rotating blades on the rotating shafts, and the rotation of the rotating blades causes the flow direction of the liquid to deflect, so that the flow direction and flow rate of the liquid flowing out of the first spraying holes and the second spraying holes both change. Another part of the less liquid enters the spray holes and impacts the reflection cavity, and the reflected liquid flows along the area between the inner pipe and the outer pipe, and is mixed with the liquid sprayed through the first spraying holes by the reflection of the arc-shaped guiding piece. With the continuous swing of the arc-shaped guiding piece, the flow direction and flow rate of the liquid finally passing through the second spraying holes further change, making the spraying range of the sprayed liquid larger and reducing the spraying dead angle.

[0055] The above are only the preferred embodiments of the present invention, and thus do not limit the patent protection scope of the present invention. Any equivalent structural transformation made by using the content of the specification and drawings of the present invention, directly or indirectly applied to other related technical fields, shall be equally included in the protection scope of the present invention.

Claims

1. A method for continuously preparing N-cyanoethyl aniline, characterized in that, Including: Aniline and acrylonitrile in the raw material intermediate tank are continuously pumped into the tubular premixing device in front of the tower through a regulating valve for mixing, then enter a heat exchanger for preheating, and then enter a tubular reactor. They are alternately sprayed into the catalyst packing layer at a first flow rate and a second flow rate through a redistributor above the tube, and the reaction liquid fully contacts in the catalyst packing layer to undergo a condensation reaction. The reaction temperature is 84 - 86 °C, and the residence time is 4 - 8 h. It flows out from the bottom of the tubular reactor and enters the product receiving tank. Among them, the first flow rate is 0.6 - 0.8 times that of the second flow rate.

2. The method for continuously preparing N-cyanoethyl aniline according to claim 1, characterized in that, The catalyst is a supported composite catalyst, including an alumina-supported zinc and copper catalyst.

3. The method for continuously preparing N-cyanoethyl aniline according to claim 1, characterized in that, Its heat exchanger is preheated to 55 - 60 °C.

4. The method for continuously preparing N-cyanoethyl aniline according to claim 1, characterized in that, Among them, aniline enters the tubular mixer for mixing at a flow rate of 2.0 - 2.4 kg / h, and acrylonitrile enters at a flow rate of 1.26 - 1.30 kg / h.

5. A method for continuously preparing N-cyanoethyl aniline according to claim 1 or 2 or 3 or 4, characterized in that, The tubular reactor includes a vertical tubular structure. A support plate is arranged at the lower part of the vertical tubular structure, and the supported composite catalyst is stacked on the support plate. A redistributor is arranged at the inlet above the vertical tubular structure.

6. The method for continuously preparing N-cyanoethylaniline according to claim 5, characterized in that, The top of the tubular reactor is provided with a first feed port; the redistributor includes a liquid inlet pipe communicating with the first feed port, and a plurality of liquid spraying pipes are uniformly installed on the outer periphery of the liquid inlet pipe.

7. The method for continuously preparing N-cyanoethyl aniline according to claim 6, characterized in that, The liquid spraying pipe includes an inner pipe and an outer pipe. One end of the outer pipe close to the liquid inlet pipe is in a closed state. A plurality of first spraying holes are arranged on the inner pipe, and a plurality of second spraying holes are arranged on the outer pipe. The number of second spraying holes is more than that of the first spraying holes, and at least part of the first spraying holes are directly opposite to the second spraying holes.

8. The method for continuously preparing N-cyanoethyl aniline according to claim 7, wherein A plurality of rotating shafts are rotatably installed on the inner pipe, a plurality of rotating blades are installed on the rotating shafts, a spraying hole is arranged at the end of the inner pipe, and a reflection cavity is arranged at the end of the outer pipe.

9. The method for continuously preparing N-cyanoethyl aniline according to claim 7, characterized in that, The inner diameter of the first spraying hole gradually expands from the inside to the outside.

10. The method for continuously preparing N-cyanoethyl aniline according to claim 8, characterized in that, An elastic arc-shaped guiding piece is arranged inside the second spraying hole, and the arc-shaped guiding piece extends obliquely upward from one side of the reflection cavity.

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