Multi-cycle energy-saving environment-friendly difluorobenzonitrile preparation system and method

Abstract

The invention relates to a multi-cycle energy-saving environment-friendly difluorobenzonitrile preparation system and method. The system comprises a substitution reaction subsystem, a cycle sampling analysis control subsystem, a multi-stage separation and recovery subsystem and a material recycling subsystem, wherein the substitution reaction subsystem comprises a substitution reaction kettle, a vacuum control device, a heat conduction oil temperature control device and a stirring device; the circulating sampling analysis control subsystem comprises an automatic sampling device, an intelligent analyzer and a controller; the multi-stage separation and recovery subsystem comprises a suction filtration device, a first distillation device, a drying device and a rectification device; and the material recycling subsystem comprises a solvent recycling pipeline and a rear fraction circulating pipeline. The reaction process is monitored in real time through the circulating sampling analysis control subsystem, and the precision and stability of reaction control are remarkably improved. And the recovery rate of the solvent DMI is improved through the multi-stage separation and recovery subsystem and the cyclic utilization system, and 100% cyclic utilization of the post-fraction is realized.

Description

Technical Field

[0001] The present application relates to the field of energy-saving and environmentally friendly precision chemical intelligent control technology, and specifically discloses a multi-cycle energy-saving and environmentally friendly difluorobenzonitrile preparation system and method. Background Art

[0002] 3,4-Difluorobenzonitrile, a high-performance fluorinated pharmaceutical intermediate, is a key building block for the synthesis of quinolone antibiotics, antidepressants, and new pesticides. With the rapid expansion of the global fluorinated pharmaceutical market, demand is surging.

[0003] In the prior art, 3,4-difluorobenzonitrile is often produced using a fluorination reaction route. Specifically, 3,4-dichlorobenzonitrile is used as the starting material, and a substitution reaction with potassium fluoride occurs at high temperature. This route produces 3,4-difluorobenzonitrile in a single step, generating virtually no wastewater throughout the entire production process, with a short reaction time and a relatively high product yield. However, controlling the reaction temperature during the substitution reaction relies entirely on the operator's experience. The endpoint is also determined by the operator, who first makes a preliminary assessment by observing the reaction time and temperature changes, and then takes samples for final confirmation. This method lacks real-time monitoring, and the operator is often forced to infer the reaction progress based on indirect indicators, making it difficult to accurately grasp the true state of the reaction. This can easily lead to two extreme situations: insufficient reaction, resulting in low conversion, or excessive reaction time, leading to unnecessary side reactions. Secondly, to ensure complete conversion, the reaction time is often extended as a "safety check" during production. However, this approach increases energy consumption and creates conditions for the occurrence of side reactions. Furthermore, the recovery rate of the solvent DMI (1,3-dimethyl-2-imidazolidinone) in this route is typically only 60-70%, requiring a significant amount of the high-value solvent to be disposed of as waste, resulting in a waste of resources and increased waste disposal costs. The byproduct potassium chloride produced during the reaction is difficult to effectively utilize due to its suboptimal purity, and is often treated as a low-value product.

[0004] Therefore, it is necessary to develop a multi-cycle energy-saving and environmentally friendly difluorobenzonitrile preparation system to effectively solve the problems existing in the existing technology and meet the needs of industrial production. Summary of the Invention

[0005] The present application provides a multi-cycle energy-saving and environmentally friendly difluorobenzonitrile preparation system and method to solve the problems raised in the above background technology.

[0006] The present invention is implemented through the following technical solutions:

[0007] A multi-cycle energy-saving and environmentally friendly difluorobenzonitrile preparation system, comprising a substitution reaction subsystem, a cyclic sampling analysis control subsystem, a multi-stage separation and recovery subsystem, and a material recycling subsystem;

[0008] Among them, the substitution reaction subsystem includes a substitution reaction kettle, a vacuum control device, a thermal oil temperature control device and a stirring device;

[0009] Circulating sampling and analysis control subsystem, including automatic sampling device, intelligent analyzer and controller;

[0010] Multi-stage separation and recovery subsystem, including a suction filtration device, a first distillation device, a drying device and a rectification device;

[0011] The material recycling subsystem includes a solvent recovery pipeline and a post-fraction recycling pipeline.

[0012] Furthermore, the automatic sampling device is provided on the substitution reactor and is used to collect samples in real time during the reaction process;

[0013] An intelligent analyzer, connected to an automatic sampling device, is used to detect and analyze sample composition and content;

[0014] The controller is electrically connected to the intelligent analyzer and various process equipment to automatically adjust the temperature, pressure and reaction time according to the detection results.

[0015] Furthermore, the automatic sampling device comprises:

[0016] The sample sampling port, an annular wall sampler, a sampling port flow guide tube, a flow guide tube sampling valve, an automatic sampling timer, a sampling signal trigger, a collection sampling pump and a sampling drive control module; the sample sampling port is arranged on the side wall of the sampling position of the substitution reactor; the annular wall sampler includes an annular opening hollow tube, an end-connected three-way tube and a three-way tube solenoid valve; the annular opening hollow tube is attached to the inner wall of the substitution reactor; the two ends of the annular opening hollow tube are respectively connected to the first port of the end-connected three-way tube and the second port of the end-connected three-way tube; the third port of the end-connected three-way tube is connected to the sample sampling port; the three-way tube solenoid valve controls the three ports of the end-connected three-way tube respectively; the three-way When the tube solenoid valve is opened and connected to the first port of the tee tube, a semi-ring sample from the first port is sampled through the hollow tube with an annular opening; when the tee tube solenoid valve is opened and connected to the second port of the tee tube, a semi-ring sample from the second port is sampled through the hollow tube with an annular opening; the sampling port guide tube guides the sample out for detection; the guide tube sampling valve controls the switch of the sampling port guide tube; the automatic sampling timer counts according to the set sampling cycle; when the timing reaches the set sampling cycle, a signal is sent to the sampling signal trigger to trigger the sampling signal; the sampling drive control module controls the drive collection sampling pump according to the triggered sampling signal to automatically sample and collect samples.

[0017] Furthermore, the suction filtration device is used to separate the solid potassium chloride and liquid product after the reaction;

[0018] A first distillation unit for recovering the solvent DMI;

[0019] A drying device for processing potassium chloride to recover the solid portion and recover the residual solvent;

[0020] Distillation unit for purifying 3,4-difluorobenzonitrile product.

[0021] Furthermore, the solvent recovery pipeline transports the recovered DMI solvent back to the substitution reactor;

[0022] The rear fraction circulation pipeline transports the rear fraction back to the substitution reactor to participate in the reaction.

[0023] The present invention also discloses a multi-cycle energy-saving and environmentally friendly difluorobenzonitrile preparation method of the system, comprising the following steps:

[0024] S1. Substitution reaction stage:

[0025] The solvent DMI and catalyst are vacuum-sucked into the substitution reaction kettle, and potassium fluoride is added. The controller controls the thermal oil temperature control device and the vacuum control device, raises the temperature to 130°C, maintains the pressure at -0.09 MPa for dehydration, and automatically sucks in 3,4-dichlorobenzonitrile after dehydration is completed. The controller turns on the stirring device, continues to raise the temperature to 220-226°C for reflux reaction, and collects the crude product. The cyclic sampling and analysis control subsystem monitors the reaction progress, detects the content of the intermediate monofluorobenzonitrile, and determines the reaction endpoint;

[0026] S2. Multi-stage separation and recovery stage:

[0027] After the reaction is completed, the controller controls the thermal oil temperature control device to cool down to 100°C, and the material in the kettle enters the filtration device. The filter cake after filtration is put into the drying equipment for drying, and the residual solvent is recovered at 140°C-230°C and pressure -0.09MPa, and potassium chloride is obtained as a by-product; the liquid part enters the first distillation device, and the solvent DMI is recovered at 140°C-220°C and pressure -0.09MPa.

[0028] S3. Product Refining Stage:

[0029] The crude 3,4-difluorobenzonitrile enters the distillation unit and is distilled at 185°C-225°C; the front fraction is the finished distillation material, and the back fraction is automatically recycled back to the replacement reactor;

[0030] S4. Recycling stage:

[0031] The recovered DMI solvent and subsequent fractions are automatically recycled according to a preset program.

[0032] Furthermore, in step S1 , the frequency of cyclic sampling and analysis of the cyclic sampling and analysis control subsystem is 15 minutes per time, and the controller automatically adjusts the process according to the detection results.

[0033] Furthermore, when the content of the intermediate monofluorobenzonitrile in the kettle is ≤5%, it is determined that the reaction has reached the end point, and the controller automatically adjusts to enter the next step.

[0034] Furthermore, S3. The product refining stage also includes: performing intelligent control of distillation by circulating reflux detection through a distillation device; controlling the feed valve to open through the distillation control unit of the distillation device, and the crude 3,4-difluorobenzonitrile enters the distillation kettle to perform distillation of the crude 3,4-difluorobenzonitrile; weighing the crude 3,4-difluorobenzonitrile feed amount of the distillation kettle, obtaining the crude feed amount weighing data; transmitting the crude feed amount weighing data to the distillation control unit; pre-setting the crude 3,4-difluorobenzonitrile feed amount; and analyzing the crude feed amount by the distillation control unit. Determine the crude product feed weighing data. When the crude product feed weighing data reaches the crude product preset feed amount, the distillation control unit controls the feed valve to close and stop feeding; the distillation control unit controls the thermal oil regulating valve to open and the thermal oil flows into the heating distillation kettle to start heating; the kettle temperature is monitored by the kettle temperature monitor; the reflux opening temperature is preset; the distillation control unit analyzes and determines that when the kettle temperature reaches the preset reflux opening temperature, it controls the condensation reflux pipe to open and start condensation reflux, and the condensation reflux volume gradually increases. The condensation reflux stability and the condensation reflux sample content are monitored by the reflux monitoring unit; the condensation reflux stability fluctuation range is preset. When the condensation reflux stability is within the preset condensation reflux stability fluctuation range and the set stable reflux time is reached, the distillation control unit controls the opening of the discharge valve to start collecting the product; the reflux sampling cycle is preset; the high-temperature reflux kettle temperature is preset; when the kettle temperature rises to the preset high-temperature reflux kettle temperature, according to the preset reflux sampling cycle, the reflux monitoring unit monitors the condensation reflux sample content data and transmits it to the distillation control unit for reflux sampling analysis, and analyzes the condensation reflux sample content percentage; the preset sample content parameter According to the percentage; when the content percentage of the condensed reflux sample is less than the reference percentage of the sample content, the distillation control unit controls the closure of the discharge valve to stop discharging and obtain the finished distillation material; the distillation control unit controls the closure of the thermal oil regulating valve, opens the cold oil inlet and outlet valves, starts the cold oil pump, and uses the cold oil to cool the distillation kettle to the preset post-fraction receiving temperature; and releases the post-fraction material in the reflux pipe to the post-fraction receiving tank; the post-fraction receiving tank is vacuumed, and the distillation kettle bottom control valve is opened to transfer the post-fraction to the post-fraction receiving tank; the post-fraction is used for fluorination reaction.

[0035] Furthermore, the multi-cycle energy-saving and environmentally friendly difluorobenzonitrile preparation method further includes: S5. Finished product sampling, analysis, packaging and storage stage:

[0036] The finished product of the distillation material is input into the finished product receiving tank; the stirring and mixing temperature is preset; the stirring time is preset; the temperature is adjusted to the preset stirring and mixing temperature through the steam regulating valve of the finished product receiving tank; after the stirring is turned on and the preset stirring time is reached, the stirred and mixed finished product of the distillation material is sampled and analyzed; it is determined whether the content of the mixed distillation material finished product is qualified; when the content of the mixed distillation material finished product is unqualified, an unqualified finished product content alarm is issued; and according to the unqualified content information of the mixed distillation material finished product, the missing content material is adjusted and supplemented or re-distillation is carried out at the preset stirring and mixing temperature; after the content of the mixed distillation material finished product is qualified, it is packaged into distillation material finished product barrels and sealed, and transported to the warehouse for storage.

[0037] The multi-cycle energy-saving and environmentally friendly difluorobenzonitrile preparation system and method proposed in this application has the following beneficial effects:

[0038] 1. Through the cyclic sampling analysis control subsystem, the reaction process is monitored in real time, and the reaction endpoint is determined based on the content of the intermediate monofluorobenzonitrile in the kettle. This eliminates the uncertainty of traditional processes that rely on manual experience, avoids the problems of insufficient or overreaction, and significantly improves the accuracy and stability of reaction control.

[0039] 2. The present invention improves the solvent DMI recovery rate from the traditional 60-70% to over 95% through a multi-stage separation and recovery subsystem and a recycling system, and achieves 100% recycling of the subsequent fraction. The by-product potassium chloride reaches industrial-grade purity after an optimized separation process and can be sold as a high-value product, thereby increasing the comprehensive resource utilization rate by over 25%.

[0040] 3. It can intelligently control the distillation process and condense and reflux the distillation materials, recover and recycle the materials; the rear fraction is transferred to the rear fraction receiving tank; the rear fraction is used for fluorination reaction, and the utilization rate is significantly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 This is a diagram showing an embodiment of a multi-cycle energy-saving and environmentally friendly difluorobenzonitrile preparation system of the present invention.

[0042] Figure 2 This is a partially enlarged embodiment diagram of an automatic sampling device for a multi-cycle energy-saving and environmentally friendly difluorobenzonitrile preparation system of the present invention. DETAILED DESCRIPTION

[0043] The following describes the embodiments of the present application through specific examples. Those skilled in the art will readily understand the other advantages and benefits of the present application from the disclosure herein. The present application may also be implemented or applied through various other specific embodiments, and the details in this specification may be modified or altered based on different viewpoints and applications without departing from the spirit of the present application.

[0044] Unless otherwise specified, the examples and comparative examples are parallel experiments with the same components, component contents, preparation steps, and preparation parameters. The experimental methods in the following examples are conventional methods unless otherwise specified. The experimental materials used in the following examples are purchased from commercial channels unless otherwise specified.

[0045] Unless otherwise stated, all reagents were used as received without further purification.

[0046] Example 1

[0047] A multi-cycle energy-saving and environmentally friendly difluorobenzonitrile preparation system, comprising a substitution reaction subsystem, a cyclic sampling analysis control subsystem, a multi-stage separation and recovery subsystem, and a material recycling subsystem;

[0048] The substitution reaction subsystem 10 includes a substitution reaction kettle, a vacuum control device, a thermal oil temperature control device and a stirring device;

[0049] The cyclic sampling and analysis control subsystem 20 includes an automatic sampling device, an intelligent analyzer and a controller; the automatic sampling device is set on the substitution reactor and is used to collect samples in real time during the reaction process; the intelligent analyzer is connected to the automatic sampling device and is used to detect and analyze the composition and content of the samples; the controller is electrically connected to the intelligent analyzer and various process equipment to automatically adjust the temperature, pressure and reaction time according to the detection results.

[0050] The multi-stage separation and recovery subsystem 30 includes a suction filtration device, a first distillation device, a drying device and a distillation device; the suction filtration device is used to separate the solid potassium chloride and liquid products after the reaction; the first distillation device is used to recover the solvent DMI; the multi-stage arrangement also includes a second distillation device for parallel or series recovery with the first distillation device; when connected in parallel with the first distillation device for recovery, the first distillation device and the second distillation device are connected in parallel for coordinated recovery to speed up the recovery speed; when connected in series with the first distillation device for recovery, the first distillation device and the second distillation device are connected in series for coordinated recovery to perform multi-stage distillation; the drying device is used to process the recovered solid potassium chloride and recover the residual solvent; the distillation device is used to purify the 3,4-difluorobenzonitrile product.

[0051] The material recycling subsystem 40 includes a solvent recovery pipeline and a post-fraction circulation pipeline; the solvent recovery pipeline transports the recovered DMI solvent back to the substitution reactor; and the post-fraction circulation pipeline transports the post-fraction back to the substitution reactor to participate in the reaction.

[0052] Example 2

[0053] A multi-cycle energy-saving and environmentally friendly method for preparing difluorobenzonitrile using the system of Example 1 comprises the following steps:

[0054] S1. Substitution reaction stage:

[0055] The solvent DMI and catalyst are vacuum-sucked into the substitution reaction kettle, and potassium fluoride is added. The controller controls the thermal oil temperature control device and the vacuum control device, raises the temperature to 130°C, maintains the pressure at -0.09 MPa for dehydration, and automatically sucks in 3,4-dichlorobenzonitrile after dehydration is completed. The controller turns on the stirring device, continues to raise the temperature to 220-226°C for reflux reaction, and collects the crude product. The cyclic sampling and analysis control subsystem monitors the reaction progress, and the content of the generated intermediate monofluorobenzonitrile is tested every 15 minutes. When the content of the intermediate monofluorobenzonitrile in the material in the kettle is ≤5%, it is judged that the reaction has reached the end point, and the controller automatically adjusts to the next step;

[0056] S2. Multi-stage separation and recovery stage:

[0057] After the reaction is completed, the controller controls the thermal oil temperature control device to cool down to 100°C, and the material in the kettle enters the filtration device. The filter cake after filtration is put into the drying equipment for drying, and the residual solvent is recovered at 140°C-230°C and pressure -0.09MPa, and potassium chloride is obtained as a by-product; the liquid part enters the first distillation device, and the solvent DMI is recovered at 140°C-220°C and pressure -0.09MPa.

[0058] S3. Product Refining Stage:

[0059] The crude 3,4-difluorobenzonitrile enters the distillation unit and is distilled at 188°C; the front fraction is the finished distillation material, and the back fraction is automatically recycled back to the replacement reactor;

[0060] S4. Recycling stage:

[0061] The recovered DMI solvent and subsequent fractions are automatically recycled according to a preset program.

[0062] In the above embodiment, the product conversion rate is 98%, the yield is 95% (calculated as 3,4-dichlorobenzonitrile); the comprehensive recovery rate of DMI is 98.0%, the recycling rate of the rear fraction is 100%, and the recovery rate of potassium chloride is 92%.

[0063] Example 3, the automatic sampling device includes: a sample sampling port 201, an annular wall sampler 202, a sampling port guide tube 203, a guide tube sampling valve 204, an automatic sampling timer 205, a sampling signal trigger 206, a collection sampling pump 207 and a sampling drive control module 208; the sample sampling port is arranged on the side wall of the sampling position of the substitution reactor; the annular wall sampler includes an annular opening hollow tube, a terminal tee and a tee solenoid valve; the annular opening hollow tube is attached to the inner wall of the substitution reactor; the two ends of the annular opening hollow tube are respectively connected to the first port of the terminal tee and the second port of the terminal tee; the third port of the terminal tee is connected to the sample sampling port; the tee The tube solenoid valve controls the three ports of the tee pipe respectively; when the tee pipe solenoid valve is opened to connect to the first port of the tee pipe, a semi-ring sample of the first port is sampled through the hollow tube with an annular opening; when the tee pipe solenoid valve is opened to connect to the second port of the tee pipe, a semi-ring sample of the second port is sampled through the hollow tube with an annular opening; the sampling port guide pipe guides the sample out for detection; the guide pipe sampling valve controls the switch of the sampling port guide pipe; the automatic sampling timer counts according to the set sampling cycle; when the timing reaches the set sampling cycle, a signal is sent to the sampling signal trigger to trigger the sampling signal; the sampling drive control module controls the drive collection sampling pump according to the triggered sampling signal to automatically sample and collect samples.

[0064] Example 4, S3. The product refining stage further includes: performing intelligent control distillation by circulating reflux detection through a distillation device; the distillation device includes: a distillation kettle, a feed valve, a kettle temperature monitor, a thermal oil regulating valve, a cold oil inlet and outlet valve, a cold oil pump, a condensate reflux pipe, a discharge valve, a reflux monitoring unit, a distillation control unit, and a post-fraction receiving tank; the distillation control unit of the distillation device controls the feed valve to open, and the crude 3,4-difluorobenzonitrile enters the distillation kettle to perform distillation of the crude 3,4-difluorobenzonitrile; weighing the crude 3,4-difluorobenzonitrile feed amount of the distillation kettle, obtaining the crude feed amount weighing data; transmitting the crude feed amount weighing data to the distillation control unit; pre-setting 3,4- The feed amount of crude difluorobenzonitrile is preset; the distillation control unit analyzes and determines the weighing data of the crude feed amount. When the weighing data of the crude feed amount reaches the preset feed amount of the crude product, the distillation control unit controls the feed valve to close and stop feeding; the distillation control unit controls the thermal oil regulating valve to open and the thermal oil flows into the heating distillation kettle to start heating; the kettle temperature is monitored by the kettle temperature monitor; the reflux opening temperature is preset; the distillation control unit analyzes and determines that the kettle temperature reaches the preset reflux opening temperature, controls the condensation reflux pipe to open and start condensation reflux, and the condensation reflux amount gradually increases. The condensation reflux stability and the condensation reflux sample content are monitored by the reflux monitoring unit; the condensation reflux stability fluctuation range is preset. When the condensation reflux stability is at When the temperature of the distillation kettle reaches the preset high-temperature reflux kettle temperature, the reflux monitoring unit monitors the content of the condensation reflux sample and transmits the data to the distillation control unit for reflux sampling analysis, and analyzes the percentage of the condensation reflux sample content; the preset sample content reference percentage; when the condensation reflux sample content percentage is less than the sample content reference percentage, the distillation control unit controls the closing of the discharge valve to stop discharging and obtain the finished distillation material; the distillation control unit controls the closing of the thermal oil regulating valve, and opens the distillation control unit. Open the cold oil inlet and outlet valves, start the cold oil pump, and use the cold oil to cool the distillation kettle to the preset post-fraction receiving temperature; and release the post-fraction material in the reflux pipe to the post-fraction receiving tank; the post-fraction receiving tank is vacuumed, open the control valve at the bottom of the distillation kettle, and transfer the post-fraction to the post-fraction receiving tank; the post-fraction is used for fluorination reaction; the preset feed amount of crude product includes: 5 tons, 7 tons, 9 tons or 10 tons; the preset reflux opening temperature includes: 185℃, 188℃ or 190℃; the preset high-temperature reflux kettle temperature includes: 225℃, 228℃ or 230℃; the preset post-fraction receiving temperature includes: 50℃, 52℃ or 55℃; the amount used for fluorination reaction includes: 60Kg, 70Kg or 80Kg.

[0065] Principle and effect: Product refining is very critical; the product refining stage also includes: intelligent control of distillation through circulation reflux detection through the distillation device; the distillation control unit of the distillation device controls the feed valve to open, and the crude 3,4-difluorobenzonitrile enters the distillation kettle for distillation of the crude 3,4-difluorobenzonitrile; weighing is carried out using the pressure sensor detection principle; the feed amount of the crude 3,4-difluorobenzonitrile in the distillation kettle is weighed to obtain the weighing data of the crude feed amount; the weighing data of the crude feed amount is transmitted to the distillation control unit; the preset feed amount of the crude 3,4-difluorobenzonitrile is pre-set; distillation control The unit analyzes and determines the crude product feed weighing data. When the crude product feed weighing data reaches the crude product preset feed amount, the distillation control unit controls the feed valve to close and stop feeding; the heat transfer oil is introduced after external heating; the distillation control unit controls the heat transfer oil regulating valve to open and the heat transfer oil flows into the heating distillation kettle to start heating; the kettle temperature is monitored by the kettle temperature monitor; the reflux opening temperature is preset; when the distillation control unit analyzes and determines that the kettle temperature reaches the preset reflux opening temperature, it controls the condensation reflux pipe to open and start condensation reflux, and the condensation reflux amount gradually increases, and the condensation reflux stability and condensation reflux are monitored by the reflux monitoring unit. Sample content; the effective component content of the condensation reflux sample content; preset condensation reflux stability fluctuation range, when the condensation reflux stability is within the preset condensation reflux stability fluctuation range and reaches the set stable reflux time, the distillation control unit controls the opening of the discharge valve to start collecting the product; preset reflux sampling cycle; preset high-temperature reflux kettle temperature; when the kettle temperature rises to the preset high-temperature reflux kettle temperature, according to the preset reflux sampling cycle, the reflux monitoring unit monitors the condensation reflux sample content data and transmits it to the distillation control unit for reflux sampling analysis, and analyzes the condensation reflux sample content percentage; preset sample Content reference percentage; when the content percentage of the condensed reflux sample is less than the sample content reference percentage, the distillation control unit controls the closure of the discharge valve to stop discharging and obtain the finished distillation material; the distillation control unit controls the closure of the thermal oil regulating valve, opens the cold oil inlet and outlet valves, starts the cold oil pump, and uses the cold oil to cool the distillation kettle to the preset post-fraction receiving temperature; and releases the post-fraction material in the reflux pipe to the post-fraction receiving tank; the post-fraction receiving tank is vacuumed, and the distillation kettle bottom control valve is opened to transfer the post-fraction to the post-fraction receiving tank; the post-fraction is used for fluorination reaction; it can significantly improve material utilization.

[0066] Example 5, the multi-cycle energy-saving and environmentally friendly preparation method of difluorobenzonitrile of the present invention further includes: S5. Finished product sampling and analysis, packaging and storage stage: the distillation material finished product is input into the finished product receiving tank; the stirring and mixing temperature is preset; the stirring time is preset; the temperature is adjusted to the preset stirring and mixing temperature by the steam regulating valve of the finished product receiving tank; the stirring is started and after the preset stirring time is reached, the stirring and mixing finished product of the distillation material is sampled and analyzed; whether the content of the mixed distillation material finished product is qualified; if the content of the mixed distillation material finished product is unqualified, an unqualified finished product content alarm is issued; and according to the mixed distillation material If the content of the finished material is unqualified, the missing material will be adjusted and supplemented, or the material will be distilled again at the preset stirring and mixing temperature; after the mixed distillation material content is qualified, it will be packaged into distillation material finished product barrels and sealed, and transported to the warehouse for storage; the preset stirring and mixing temperature includes: 65℃, 66℃ or 68℃; the preset stirring time includes: 15 minutes, 18 minutes or 20 minutes; it can perform intelligent control of the distillation process and condensation reflux of the distillation material, and recycle the material; the rear fraction is transferred to the rear fraction receiving tank; the rear fraction is used for fluorination reaction, and the utilization rate is significantly improved.

[0067] Principle and effect: Material recycling and energy conservation and environmental protection are very important technologies for the preparation of difluorobenzonitrile; the multiple-cycle energy-saving and environmentally friendly difluorobenzonitrile preparation method also includes: finished product sampling analysis, packaging and storage stage: the finished product of the distillation material is input into the finished product receiving tank; the preset stirring and mixing temperature; the preset stirring time; the temperature is adjusted to the preset stirring and mixing temperature through the steam regulating valve of the finished product receiving tank; after the stirring is turned on and the preset stirring time is reached, the stirring and mixing of the finished distillation material is sampled and analyzed; it is determined whether the content of the finished mixed distillation material is qualified; when the content of the finished mixed distillation material is unqualified, an unqualified finished product content alarm is issued; and according to the unqualified content information of the finished mixed distillation material, the missing content material is adjusted to be supplemented or the distillation treatment is carried out again at the preset stirring and mixing temperature; after the content of the finished mixed distillation material is qualified, it is packaged into the finished distillation material barrel and sealed, and transported to the warehouse for storage; it can significantly improve the mixing effect of the finished distillation material; and significantly improve the qualified rate of the finished distillation material.

[0068] The specific embodiments of the present application have been described in detail above, but these are merely examples, and the present application is not limited to the specific embodiments described above. For those skilled in the art, any equivalent modifications and substitutions made to the present application are also within the scope of the present application. Therefore, equivalent changes and modifications made without departing from the spirit and scope of the present application should be included within the scope of the present application.

Claims

1. A multi-cycle energy-saving and environmentally friendly difluorobenzonitrile preparation system, characterized in that: It includes substitution reaction subsystem, circulation sampling analysis control subsystem, multi-stage separation and recovery subsystem and material recycling subsystem; Among them, the substitution reaction subsystem includes a substitution reaction kettle, a vacuum control device, a thermal oil temperature control device and a stirring device; Circulating sampling and analysis control subsystem, including automatic sampling device, intelligent analyzer and controller; Multi-stage separation and recovery subsystem, including a suction filtration device, a first distillation device, a drying device and a rectification device; The material recycling subsystem includes a solvent recovery pipeline and a post-fraction recycling pipeline.

2. The multi-cycle energy-saving and environmentally friendly difluorobenzonitrile preparation system according to claim 1, characterized in that: The automatic sampling device is arranged on the substitution reactor and is used to collect samples in real time during the reaction process; the intelligent analyzer is connected to the automatic sampling device and is used to detect and analyze the composition and content of the samples; The controller is electrically connected to the intelligent analyzer and various process equipment to automatically adjust the temperature, pressure and reaction time according to the detection results.

3. The multi-cycle energy-saving and environmentally friendly difluorobenzonitrile preparation system according to claim 1, characterized in that: The automatic sampling device includes: The sample sampling port, an annular wall sampler, a sampling port flow guide tube, a flow guide tube sampling valve, an automatic sampling timer, a sampling signal trigger, a collection sampling pump and a sampling drive control module; the sample sampling port is arranged on the side wall of the sampling position of the substitution reactor; the annular wall sampler includes an annular opening hollow tube, an end-connected three-way tube and a three-way tube solenoid valve; the annular opening hollow tube is attached to the inner wall of the substitution reactor; the two ends of the annular opening hollow tube are respectively connected to the first port of the end-connected three-way tube and the second port of the end-connected three-way tube; the third port of the end-connected three-way tube is connected to the sample sampling port; the three-way tube solenoid valve controls the three ports of the end-connected three-way tube respectively; the three-way When the tube solenoid valve is opened and connected to the first port of the tee tube, a semi-ring sample from the first port is sampled through the hollow tube with an annular opening; when the tee tube solenoid valve is opened and connected to the second port of the tee tube, a semi-ring sample from the second port is sampled through the hollow tube with an annular opening; the sampling port guide tube guides the sample out for detection; the guide tube sampling valve controls the switch of the sampling port guide tube; the automatic sampling timer counts according to the set sampling cycle; when the timing reaches the set sampling cycle, a signal is sent to the sampling signal trigger to trigger the sampling signal; the sampling drive control module controls the drive collection sampling pump according to the triggered sampling signal to automatically sample and collect samples.

4. The multi-cycle energy-saving and environmentally friendly difluorobenzonitrile preparation system according to claim 1, characterized in that: The suction filtration device is used to separate the solid potassium chloride and liquid product after the reaction; A first distillation unit for recovering the solvent DMI; A drying device for processing potassium chloride to recover the solid portion and recover the residual solvent; Distillation unit for purifying 3,4-difluorobenzonitrile product.

5. The multi-cycle energy-saving and environmentally friendly difluorobenzonitrile preparation system according to claim 1, characterized in that: The solvent recovery pipeline transports the recovered DMI solvent back to the substitution reactor; The rear fraction circulation pipeline transports the rear fraction back to the substitution reactor to participate in the reaction.

6. A multi-cycle energy-saving and environmentally friendly method for preparing difluorobenzonitrile based on the system according to any one of claims 1 to 5, characterized in that: The following steps are involved: S1. Substitution reaction stage: The solvent DMI and catalyst are vacuum-sucked into the substitution reactor, and potassium fluoride is added. The controller controls the thermal oil temperature control device and the vacuum control device, raises the temperature to 130°C, maintains the pressure at -0.09 MPa for dehydration, and automatically sucks in 3,4-dichlorobenzonitrile after dehydration is completed. The controller turns on the stirring device, continues to raise the temperature to 220°C-226°C for reflux reaction, and collects the crude product. The cyclic sampling and analysis control subsystem monitors the reaction progress, detects the content of the intermediate monofluorobenzonitrile, and determines the reaction endpoint; S2. Multi-stage separation and recovery stage: After the reaction is completed, the controller controls the thermal oil temperature control device to cool down to 100°C, and the material in the kettle enters the filtration device. The filter cake after filtration is put into the drying equipment for drying, and the residual solvent is recovered at 140°C-230°C and pressure -0.09MPa, and potassium chloride is obtained as a by-product; the liquid part enters the first distillation device, and the solvent DMI is recovered at 140°C-220°C and pressure -0.09MPa. S3. Product Refining Stage: The crude 3,4-difluorobenzonitrile enters the distillation unit and is distilled at 185°C-225°C; the front fraction is the finished distillation material, and the back fraction is automatically recycled back to the replacement reactor; S4. Recycling stage: The recovered DMI solvent and subsequent fractions are automatically recycled according to a preset program.

7. The preparation method according to claim 6, characterized in that In step S1, the frequency of cyclic sampling and analysis of the cyclic sampling and analysis control subsystem is 15 minutes per time, and the controller automatically adjusts the process according to the detection results.

8. The preparation method according to claim 7, characterized in that When the content of the intermediate monofluorobenzonitrile in the kettle is ≤5%, it is judged that the reaction has reached the end point, and the controller automatically adjusts to enter the next step.

9. The multi-cycle energy-saving and environmentally friendly method for preparing difluorobenzonitrile according to claim 6, characterized in that: S3. The product refining stage also includes: performing intelligent control of distillation by circulating reflux detection through the distillation device; controlling the feed valve to open through the distillation control unit of the distillation device, and the crude 3,4-difluorobenzonitrile enters the distillation kettle to perform distillation of the crude 3,4-difluorobenzonitrile; weighing the crude 3,4-difluorobenzonitrile feed amount of the distillation kettle, obtaining the crude feed amount weighing data; transmitting the crude feed amount weighing data to the distillation control unit; pre-setting the crude 3,4-difluorobenzonitrile feed amount; the distillation control unit analyzes and determines the crude The feed quantity weighing data, when the crude product feed quantity weighing data reaches the crude product preset feed quantity, the distillation control unit controls the feed valve to close and stop feeding; the distillation control unit controls the thermal oil regulating valve to open the thermal oil to flow into the heating distillation kettle to start heating; the kettle temperature is monitored by the kettle temperature monitor; the preset reflux opening temperature; the distillation control unit analyzes and determines that the kettle temperature has reached the preset reflux opening temperature, controls the condensation reflux pipe to open and start condensation reflux, and the condensation reflux volume gradually increases, and the condensation reflux stability and the condensation reflux sample content are monitored by the reflux monitoring unit; the preset condensation reflux stability fluctuation range, when the condensation reflux stability is within the preset condensation reflux stability fluctuation range and reaches the set stable reflux time, the distillation control unit controls the opening of the discharge valve to start collecting the product; the preset reflux sampling cycle; the preset high-temperature reflux kettle temperature; when the kettle temperature rises to the preset high-temperature reflux kettle temperature, according to the preset reflux sampling cycle, the reflux monitoring unit monitors the condensation reflux sample content data and transmits it to the distillation control unit for reflux sampling analysis, and analyzes the condensation reflux sample content percentage; the preset sample content reference percentage; when the content percentage of the condensed reflux sample is less than the reference percentage of the sample content, the distillation control unit controls the closure of the discharge valve to stop discharging and obtain the finished distillation material; the distillation control unit controls the closure of the thermal oil regulating valve, opens the cold oil inlet and outlet valves, starts the cold oil pump, and uses the cold oil to cool the distillation kettle to the preset rear fraction receiving temperature; and releases the rear fraction material in the reflux pipe to the rear fraction receiving tank; the rear fraction receiving tank is vacuumed, and the control valve at the bottom of the distillation kettle is opened to transfer the rear fraction to the rear fraction receiving tank; the rear fraction is used for fluorination reaction.

10. The multi-cycle energy-saving and environmentally friendly method for preparing difluorobenzonitrile according to claim 6, characterized in that: Also includes: S5. Finished product sampling, analysis, packaging and storage stage: The finished product of distillation material is input into the finished product receiving tank; Preset stirring and mixing temperature; preset stirring time; adjust the temperature to the preset stirring and mixing temperature through the steam regulating valve of the finished product receiving tank; start stirring and after reaching the preset stirring time, carry out sampling and analysis of the finished product of the stirred and mixed distillation material; determine whether the content of the finished mixed distillation material is qualified; when the content of the finished mixed distillation material is unqualified, issue an unqualified finished product content alarm; and according to the unqualified content information of the finished mixed distillation material, adjust and supplement the missing content material or carry out re-distillation at the preset stirring and mixing temperature; after the content of the finished mixed distillation material is qualified, it is packaged into distillation material finished product barrels and sealed, and transported to the warehouse for storage.

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