Crystallization process of o-chloro-p-nitroaniline

Abstract

The invention discloses a crystallization process of o-chloro-p-nitroaniline, which comprises the following steps: feeding a material into a crystallization kettle to crystallize the o-chloro-p-nitroaniline, regulating and controlling the temperature in the kettle body in the crystallization process, cooling to a metastable region of the o-chloro-p-nitroaniline, preserving the heat in the metastable region for a first preset time length, and then cooling to a second preset time length; continuously cooling to a first temperature lower than the melting point of the o-chloro-p-nitroaniline, keeping the temperature at the first temperature for a second preset duration, continuously cooling to a second temperature, and outputting the material out of the crystallization kettle for filtration and separation; in the cooling process, the cooling speed in the kettle body is controlled to be 0.1-0.2 DEG C / min. According to the invention, the interior of the kettle body can be slowly cooled, and the cooling speed of each part in the kettle body can be more uniform, so that the crystallization purity and the product quality of o-chloro-p-nitroaniline are finally improved.

Description

Technical Field

[0001] The present invention relates to a crystallization process for o-chloro-p-nitroaniline. Background Art

[0002] The Chinese name of o-chloro-p-nitroaniline is 2-chloro-4-nitroaniline, and its chemical formula is C6H5ClN2O2; o-chloro-p-nitroaniline is an important intermediate for dyes and pigments.

[0003] During the preparation of o-chloro-p-nitroaniline, it is necessary to put the material into a crystallization kettle to implement the crystallization process of o-chloro-p-nitroaniline; however, the control of the existing o-chloro-p-nitroaniline crystallization process needs to be improved. For example, the cooling rate during the crystallization process is too fast, and the cooling rates at various parts inside the crystallization kettle are not uniform enough during the crystallization process, which will ultimately affect the crystallization purity and product quality of o-chloro-p-nitroaniline. Summary of the Invention

[0004] To solve the defects of the prior art, the present invention provides a crystallization process for o-chloro-p-nitroaniline, including: putting the material into a crystallization kettle to implement the crystallization of o-chloro-p-nitroaniline (the temperature of the material put into the crystallization kettle is 115-120 °C), regulating the temperature inside the kettle body during the crystallization process, first cooling the temperature inside the kettle body to the metastable zone of o-chloro-p-nitroaniline (109-110 °C) and keeping it warm in the metastable zone for a first preset time (1 hour), then continuing to cool the temperature inside the kettle body to a first temperature (90 °C) lower than the melting point of o-chloro-p-nitroaniline (108 °C) and keeping it warm at the first temperature for a second preset time (1 hour), then continuing to cool the temperature inside the kettle body to a second temperature (40 °C) and outputting the material from the crystallization kettle for filtration and separation; and during the cooling process, controlling the cooling rate inside the kettle body at 0.1-0.2 °C / min.

[0005] Preferably, the crystallization kettle includes: a kettle body, a rotating shaft vertically penetrating the kettle body, and a plurality of horizontally arranged stirring frames vertically distributed on the rotating shaft inside the kettle body; during the crystallization process, heat exchange medium is input into each stirring frame through the side wall of the kettle body to control the cooling rate of each stirring frame at 0.1-0.2 °C / min.

[0006] For the more specific structure and usage method of the crystallization kettle of the present invention, please refer to the specific implementation manner.

[0007] The advantages and beneficial effects of the present invention are as follows: providing a crystallization process for o-chloro-p-nitroaniline, putting the material into a crystallization kettle to implement the crystallization of o-chloro-p-nitroaniline, which can slowly cool the inside of the kettle body and make the cooling rates at various parts inside the kettle body more uniform, thereby ultimately improving the crystallization purity and product quality of o-chloro-p-nitroaniline.

[0008] The present invention also has the following characteristics: The present invention realizes the input of a heat exchange medium (the heat exchange medium is a gas or a liquid) into the stirring frame through the side wall of the kettle body by effectively docking the output port of the docking unit on the side wall of the kettle body with the input port of the corresponding stirring frame; The present invention increases the cooling rate (detected by the temperature sensor) of a certain stirring frame by increasing the effective docking frequency of the stirring frame (while the rotation speed of the rotating shaft remains unchanged); The present invention reduces the cooling rate (detected by the temperature sensor) of a certain stirring frame by reducing the effective docking frequency of the stirring frame (while the rotation speed of the rotating shaft remains unchanged); The present invention adjusts the effective docking frequency of a certain stirring frame (while the rotation speed of the rotating shaft remains unchanged) to make the cooling rate (detected by the temperature sensor) of the stirring frame fluctuate between a preset lower limit and a preset upper limit; The present invention makes the cooling rates (detected by the temperature sensors) of each stirring frame fluctuate between a preset lower limit and a preset upper limit, so as to make the cooling rates at various parts inside the kettle body more uniform. Description of the Drawings

[0009] Figure 1 is a side view schematic diagram of the crystallization kettle; Figure 2 is a top view schematic diagram of the stirring frame; Figure 3 is a top view schematic diagram of the docking unit. Detailed Embodiments

[0010] The following combines the drawings and embodiments to further describe the specific embodiments of the present invention. The following embodiments are only used to more clearly illustrate the technical solutions of the present invention and cannot be used to limit the protection scope of the present invention.

[0011] The technical solutions specifically implemented by the present invention are as follows: The present invention provides a crystallization process for o-chloro-p-nitroaniline, and the material is put into a crystallization kettle to carry out the crystallization of o-chloro-p-nitroaniline; Such as Figures 1 to 3As shown in the figure, the crystallization kettle includes: a kettle body 1 with a cylindrical side wall, a feed pipe 2 externally connected to the top wall of the kettle body 1 and used for inputting materials, a feed valve 21 provided on the feed pipe 2, a discharge pipe 3 externally connected to the bottom wall of the kettle body 1 and used for outputting materials, a discharge valve 31 provided on the discharge pipe 3, a rotating shaft 4 vertically penetrating the kettle body 1 and coaxial with the side wall of the kettle body 1, a motor 5 provided on the top wall of the kettle body 1 and connected to the top end of the rotating shaft 4, a central channel 41 opened in the rotating shaft 4, vertically extending from the top of the rotating shaft 4 to the bottom end of the rotating shaft 4 and coaxial with the rotating shaft 4, a rotary joint 6 provided at the bottom end of the rotating shaft 4, a vertically arranged cylindrical ring channel 11 opened in the side wall of the kettle body 1 and coaxial with the side wall of the kettle body 1, a circulation pipe 7 with one end communicated with the central channel 41 through the rotary joint 6 and the other end communicated with the bottom end of the ring channel 11, a circulation pump 71 and a heat exchanger 72 provided on the circulation pipe 7, a plurality of horizontally arranged stirring frames 8 (more specifically, the plurality of stirring frames 8 are vertically evenly distributed inside the kettle body 1) vertically and equally spaced on the rotating shaft 4 inside the kettle body 1, and a plurality of docking units 9 vertically and equally spaced on the side wall of the kettle body 1 and corresponding to the stirring frames 8 one by one; The stirring frame 8 includes: an inner ring 81 sleeved and fixed on the rotating shaft 4 and coaxial with the rotating shaft 4, an outer ring 82 with an outer circle slidably fitted (more specifically, rotationally sealed) with the inner surface of the side wall of the kettle body 1 and coaxial with the rotating shaft 4, a plurality of input ports 83 opened on the outer circle of the outer ring 82 and evenly distributed along the circumferential direction of the outer ring 82, a plurality of connecting arms 84 corresponding to each input port 83 one by one, all arranged along the radial direction of the rotating shaft 4, with the outer end connected to the inner circle of the outer ring 82 and facing the corresponding input port 83, and the inner end connected to the outer circle of the inner ring 81, a plurality of branch channels 85 corresponding to each input port 83 one by one, penetrating the corresponding connecting arm 84 and communicating the corresponding input port 83 with the central channel 41, and temperature sensors 86 embedded on the surface of one or several connecting arms 84; the stirring frame 8 (inner ring 81, connecting arm 84, outer ring 82) is made of heat-conducting material; The docking unit 9 includes: a plurality of output ports 91 opened on the inner surface of the side wall of the kettle body 1, evenly distributed along the circumferential direction of the side wall of the kettle body 1 and capable of being docked with the input ports 83 on the corresponding stirring frame 8 one by one, a plurality of output channels 92 corresponding to each output port 91 one by one, all arranged along the radial direction of the side wall of the kettle body 1 and communicating the corresponding output port 91 with the ring channel 11, and one-way valves 93 respectively provided on each output channel 92 (the one-way valve 93 only allows the heat exchange medium to flow from the ring channel 11 along the output channel 92 to the output port 91); the number of output ports 91 of the docking unit 9 is more than the number of input ports 83 on the corresponding stirring frame 8; The temperature of the material put into the crystallization kettle is 115-120°C; during the crystallization process, the motor 5 drives the stirring frame 8 to rotate at a constant speed through the rotating shaft 4 to stir the material in the kettle body 1; and during the crystallization process, the temperature inside the kettle body 1 is regulated, first the temperature inside the kettle body 1 is cooled to the metastable zone of o-chloro-p-nitroaniline (metastable zone is 109-110°C) and kept warm in the metastable zone for a first preset time (the first preset time is 1 hour), then the temperature inside the kettle body 1 is further cooled to a first temperature (the first temperature is 90°C) lower than the melting point of o-chloro-p-nitroaniline (melting point is 108°C) and kept warm at the first temperature for a second preset time (the second preset time is 1 hour), then the temperature inside the kettle body 1 is further cooled to the second temperature (the second temperature is 40°C) and the material is output from the kettle body 1 for filtration and separation; During the cooling process, the cooling rate inside the kettle body 1 is controlled at 0.1-0.2°C / min. The control of the cooling rate inside the kettle body 1 includes: During the rotation of the stirring frame 8, the output port 91 of the docking unit 9 is docked with the input port 83 of the corresponding stirring frame 8 one by one, and when the one-way valve 93 corresponding to the output port 91 is opened, the output port 91 and the docked input port 83 form an effective docking; and when effectively docked, the ring channel 11, the output channel 92 corresponding to the output port 91, the output port 91, the input port 83 docked with the output port 91, the branch channel 85 corresponding to the input port 83, the central channel 41, the circulation pipe 7, and the ring channel 11 are connected in sequence to form a loop, and the circulation pump 71 drives the heat exchange medium to circulate in the loop, and the heat exchange medium circulating in the loop performs heat exchange and cooling on the inside of the kettle body 1; and the heat exchanger 72 performs heat exchange and cooling on the heat exchange medium flowing through the circulation pipe 7; the heat exchange medium is gas or liquid; If the cooling speed detected by the temperature sensor 86 of a certain stirring frame 8 decreases to a preset lower limit, the number of openings of the one-way valve 93 of the docking unit 9 corresponding to the stirring frame 8 is increased, that is, the frequency of effective docking of the stirring frame 8 is increased (the rotation speed of the shaft 4 remains unchanged); If the cooling speed detected by the temperature sensor 86 of a certain stirring frame 8 increases to a preset upper limit, the number of openings of the one-way valve 93 of the docking unit 9 corresponding to the stirring frame 8 is reduced, that is, the frequency of effective docking of the stirring frame 8 is reduced (the rotation speed of the shaft 4 remains unchanged); By controlling the number of one-way valves 93 of the docking unit 9 corresponding to the stirring frame 8 being opened, the frequency of effective docking of the stirring frame 8 is adjusted (the rotation speed of the rotating shaft 4 remains unchanged), so that the cooling speed detected by the temperature sensor 86 of the stirring frame 8 fluctuates between a preset lower limit and a preset upper limit; By making the cooling rate detected by the temperature sensor 86 of each stirring frame 8 float between a preset lower limit and a preset upper limit, the cooling rate at various locations inside the kettle body 1 is made more uniform; By setting the preset lower limit of the cooling rate to 0.1 °C / min and the preset upper limit to 0.2 °C / min, that is, controlling the cooling rate inside the kettle body 1 within 0.1 - 0.2 °C / min, the inside of the kettle body 1 is slowly cooled; Furthermore, the crystallization purity of o-chloro-p-nitroaniline and the product quality are ultimately improved.

[0012] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the technical principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A crystallization process for o-chloro-p-nitroaniline, characterized in that: include: The material is put into a crystallization kettle to implement the crystallization of o-chloro-p-nitroaniline. During the crystallization process, the temperature inside the kettle is regulated, firstly the temperature is lowered to the metastable zone of o-chloro-p-nitroaniline and kept in the metastable zone for a first preset time, then the temperature is further lowered to a first temperature lower than the melting point of o-chloro-p-nitroaniline and kept at the first temperature for a second preset time, then the temperature is further lowered to the second temperature and the material is output from the crystallization kettle for filtration and separation; and during the cooling process, the cooling rate inside the kettle is controlled at 0.1-0.2°C / min.

2. The crystallization process of o-chloro-p-nitroaniline according to claim 1, characterized in that: The melting point of o-chloro-p-nitroaniline is 108°C; the temperature of the material put into the crystallization kettle is 115-120°C; the metastable zone of o-chloro-p-nitroaniline is 109-110°C; the first temperature is 90°C; the second temperature is 40°C; the first preset time and the second preset time are both 1 hour.

3. The crystallization process of o-chloro-p-nitroaniline according to claim 1 or 2, characterized in that: The crystallization kettle comprises: a kettle body, a rotating shaft vertically penetrating the kettle body, and a plurality of horizontal stirring frames arranged inside the kettle body and vertically distributed on the rotating shaft; during the crystallization process, a heat exchange medium is input into each stirring frame through the side wall of the kettle body to control the cooling rate of each stirring frame at 0.1-0.2°C / min.

4. The crystallization process of o-chloro-p-nitroaniline according to claim 3, characterized in that: The multiple stirring frames are vertically evenly distributed on the rotating shaft.

5. The crystallization process of o-chloro-p-nitroaniline according to claim 4, characterized in that: The crystallization kettle also includes: a motor arranged on the top wall of the kettle body and connected to the top of the rotating shaft; during the crystallization process, the motor drives the stirring frame to rotate through the rotating shaft to stir the material in the kettle body.

6. The crystallization process of o-chloro-p-nitroaniline according to claim 5, characterized in that: The crystallization kettle further comprises: a central channel opened in the rotating shaft and extending vertically to the bottom end of the rotating shaft, a rotating joint arranged at the bottom end of the rotating shaft, a vertical cylindrical annular channel opened in the side wall of the kettle body, a circulation pipe having one end connected to the central channel through the rotating joint and the other end connected to the bottom end of the annular channel, a circulation pump and a heat exchanger arranged on the circulation pipe, and a plurality of docking units vertically distributed on the side wall of the kettle body and corresponding to the stirring frames one by one; The stirring frame comprises: an inner ring whose inner ring is sleeved on the rotating shaft, an outer ring whose outer ring is slidably matched with the inner surface of the side wall of the kettle body, a plurality of input ports which are arranged on the outer ring of the outer ring and are evenly distributed along the circumference of the outer ring, a plurality of connecting arms whose outer ends are connected to the inner ring of the outer ring and whose outer ends are directly opposite to the corresponding input ports and whose inner ends are connected to the outer ring of the inner ring, and a branch channel which penetrates the corresponding connecting arm and connects the corresponding input port with the central channel, and a temperature sensor which is embedded on the surface of one or several connecting arms; The docking unit includes: a plurality of output ports opened on the inner surface of the side wall of the kettle body, evenly distributed along the circumference of the side wall of the kettle body and capable of docking one by one with the corresponding input ports on the stirring frame, a plurality of output channels connecting the corresponding output ports with the ring channel, and a one-way valve respectively arranged on each output channel.

7. The crystallization process of o-chloro-p-nitroaniline according to claim 6, characterized in that: The preset lower limit of the cooling rate is 0.1℃ / min, and the preset upper limit of the cooling rate is 0.2℃ / min; During the rotation of the stirring frame, the output port of the docking unit is docked with the input port of the corresponding stirring frame one by one, and when the one-way valve corresponding to the output port is opened, the output port and the docked input port form an effective docking; and when effectively docked, the ring channel, the output channel corresponding to the output port, the output port, the input port docked with the output port, the branch channel corresponding to the input port, the central channel, the circulation pipe, and the ring channel are connected in sequence to form a loop, and the circulation pump drives the heat exchange medium to flow in the loop, and the heat exchange medium flowing in the loop exchanges heat and cools the inside of the kettle; and the heat exchanger exchanges heat and cools the heat exchange medium flowing through the circulation pipe; If the cooling speed detected by the temperature sensor of a certain stirring frame decreases to a preset lower limit, the number of openings of the one-way valve of the docking unit corresponding to the stirring frame is increased; If the cooling speed detected by the temperature sensor of a certain stirring frame increases to a preset upper limit, the number of openings of the one-way valve of the docking unit corresponding to the stirring frame is reduced; By controlling the opening number of the one-way valve of the docking unit corresponding to the stirring frame, the cooling speed detected by the temperature sensor of the stirring frame fluctuates between a preset lower limit and a preset upper limit; By making the cooling speed detected by the temperature sensor of each stirring frame float between a preset lower limit and a preset upper limit, the cooling speed at various places inside the kettle body can be made more uniform.

8. The crystallization process of o-chloro-p-nitroaniline according to claim 7, characterized in that: The side wall of the kettle body is cylindrical; the rotating shaft and the annular channel are coaxial with the side wall of the kettle body; the central channel, the inner ring and the outer ring are coaxial with the rotating shaft.

9. The crystallization process of o-chloro-p-nitroaniline according to claim 7, characterized in that: The multiple connecting arms are all arranged radially along the rotating shaft; the multiple output channels are all arranged radially along the side wall of the kettle body.

10. The crystallization process of o-chloro-p-nitroaniline according to claim 7, characterized in that: The number of the output ports of the docking unit is greater than the number of the input ports on the corresponding stirring frame.

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