A high-yield o-chlorobenzonitrile and its production process

Abstract

The present application discloses a high-yield o-chlorobenzonitrile and its production process, and belongs to the technical field of o-chlorobenzonitrile production. The production process includes the following steps: (1) using a series of double reactors to alternately switch as the main reactor and the side reactor, o-chlorotoluene is placed in the main reactor and the side reactor, chlorine is passed into the main reactor for chlorination to obtain chlorinated liquid, the side reactor absorbs the chlorine overflowed by the main reactor, and when the content of o-chlorobenzyl dichloride in the chlorinated liquid is 4%-9%, chlorine is stopped, and the former side reactor is used as the main reactor until the content of o-chlorobenzyl dichloride in the chlorinated liquid is 4%-9%; (2) chlorinated liquid is continuously rectified, and o-chlorobenzyl chloride is continuously obtained at the bottom of the rectifying tower; (3) o-chlorobenzyl chloride and ammonium chloride are subjected to nitrilation to obtain nitrilation liquid, and nitrilation liquid is alkali-washed, washed with water, and distilled to obtain o-chlorobenzonitrile. The production process can improve the utilization rate of chlorine in the chlorination process, reduce the solid waste in the chlorination time and system, and is more suitable for industrial production.

Description

Technical Field

[0001] The present application relates to a high-yield o-chlorobenzonitrile and a production process thereof, and belongs to the technical field of o-chlorobenzonitrile production. Background Art

[0002] o-Chlorobenzonitrile is an important chemical and organic synthesis intermediate. It can be used to prepare different products through reactions and is widely used in industries such as medicine, dyes, agriculture and spices. There are many methods for synthesizing o-chlorobenzonitrile. One of them is to use o-chlorotoluene and chlorine to chlorinate to obtain o-chlorobenzyl trichloride, and then o-chlorobenzyl trichloride is subjected to nitrilation reaction to obtain it.

[0003] At present, the reaction of ortho-chlorotoluene and chlorine chlorination to obtain ortho-chlorobenzyl chloride has begun to change from intermittent to continuous reaction. Publication No. CN113072418A discloses a production method of double kettle switching continuous chlorination, by continuously switching the main reactor and the secondary reactor, to achieve the continuous chlorination of ortho-chlorotoluene. However, in this production process, it is necessary to switch the double kettle only when the content of ortho-chlorobenzyl dichloride is less than 0.2% in sampling and analysis to obtain the crude ortho-chlorobenzyl chloride. The researchers of this application found that in the later stage of chlorination, with the decrease of the content of ortho-chlorobenzyl dichloride, the more time and chlorine are spent to increase the output of ortho-chlorobenzyl chloride, the more impurities there are in the chlorinated liquid, so this production method has the disadvantages of low chlorine utilization, long chlorination time, and more solid waste. Summary of the invention

[0004] In order to solve the above problems, a high-yield o-chlorobenzonitrile production process is provided, which can solve the above technical problems. In the production process, when the content of o-chlorobenzyl dichloride in the chlorinated liquid is 4%-9%, double kettle switching is performed, at this time, the impurity content in the system is below 1%, the content of o-chlorobenzyl trichloride is in the range of 90%-95%, and the o-chlorobenzyl trichloride is purified by distillation, which can improve the utilization rate of chlorine in the chlorination process, reduce the chlorination time and the solid waste in the system, save production costs and improve the final yield of o-chlorobenzonitrile, and is more suitable for industrial production.

[0005] According to one aspect of the present application, a high-yield production process of o-chlorobenzonitrile is provided, comprising the following steps:

[0006] (1) using a dual reactor connected in series and switching alternately as a main reactor and a sub-reactor, placing o-chlorotoluene in the main reactor and the sub-reactor, introducing chlorine gas into the main reactor for chlorination to obtain a chlorinated liquid, and the sub-reactor absorbing the chlorine gas overflowing from the main reactor. When the content of o-chlorobenzyl chloride in the chlorinated liquid is 4%-9%, the introduction of chlorine gas is stopped, the chlorinated liquid in the main reactor is discharged, o-chlorotoluene is added again, and the main reactor and the sub-reactor are switched, and the original sub-reactor is used as the main reactor until the content of o-chlorobenzyl chloride in the chlorinated liquid is 4%-9%, then the chlorinated liquid is discharged, and o-chlorotoluene is added again, and the main reactor repeats the previous operation;

[0007] (2) continuously rectifying the chlorinated liquid to continuously obtain o-chlorobenzyl trichloride at the bottom of the rectifying tower;

[0008] (3) subjecting the o-chlorobenzyl trichloride and ammonium chloride to a nitrilation reaction to obtain a nitrilation liquid, and subjecting the nitrilation liquid to alkali washing, water washing, and distillation to obtain o-chlorobenzonitrile.

[0009] The present application also adopts a double-kettle switching method to chlorinate ortho-chlorotoluene to produce ortho-chlorobenzyl trichloride. It is found that stopping the reaction when the content of ortho-chlorobenzyl dichloride is 4%-9% can significantly improve the utilization rate of chlorine, reduce the time for chlorine to be introduced, and reduce the generation of impurities in the system, thereby reducing the amount of solid waste, compared with stopping the reaction when the content of ortho-chlorobenzyl dichloride is less than 0.2% in the original process.

[0010] The new process of the present application reduces the chlorine consumption for producing one ton of product by more than 10% compared with the original process, and shortens the reaction time by more than 15%. In addition, the impurity content in the new process is below 1%, which can reduce the generation of by-products and the difficulty of treating production solid waste, and is in line with the concept of green and environmentally friendly production.

[0011] Optionally, in step (1), the reaction temperature of the main reactor is 130-140°C, and the reaction temperature of the secondary reactor is 100-110°C.

[0012] The reaction temperature of the main reactor is higher than that of the secondary reactor, so the raw materials in the main reactor can fully react and improve the product yield. If the reaction temperature of the secondary reactor is raised to the same temperature as that of the main reactor, due to the low boiling point of o-chlorotoluene, part of o-chlorotoluene will volatilize into the tail gas, which will cause the consumption of raw materials and reduce the yield of o-chlorotrichlorobenzyl chloride.

[0013] Optionally, in the main reactor, the weight ratio of the o-chlorotoluene to the introduced chlorine gas is 1:(1.6-1.8).

[0014] Optionally, in step (2), the vacuum is evacuated to above -0.09 MP during the distillation, the distillation temperature in the distillation kettle is 185-190° C., and the distillation is performed until the content of o-chlorobenzyl dichloride is below 0.2%.

[0015] Optionally, the chlorinated liquid enters the distillation kettle through an elevated tank and a flow meter, and after distillation, the solid waste content in the distillation kettle is below 1%, that is, the impurity content in the chlorinated liquid is below 1%.

[0016] Optionally, in step (2), the o-chlorobenzyl dichloride separated from the top of the distillation tower during the distillation is used as a chlorination raw material to continue to pass chlorine to prepare o-chlorobenzyl trichloride.

[0017] The chlorinated liquid is distilled to obtain pure o-chlorobenzyltrichloride. The o-chlorobenzyldichloride obtained in this step can be reused without causing waste, thereby improving the utilization rate of raw materials, the yield of the main product and the utilization rate of chlorine gas.

[0018] In the original process, o-chlorobenzyl chloride is reacted with ammonium chloride to obtain o-chlorobenzonitrile, which is then distilled to obtain o-chlorobenzonitrile with higher purity. The distillation in this process is complicated due to the large amount of impurities carried by o-chlorobenzyl chloride. It is not only time-consuming, but also has large differences in the purity of products produced in batches, which is not conducive to mass production.

[0019] The present application is to remove ortho-chlorobenzyl dichloride and a small amount of impurities by the step of rectification before the reaction of ortho-chlorobenzyl trichloride, due to the small number of impurities, ortho-chlorobenzyl dichloride is easier to be rectified and removed, the rectification step of the present application is much shorter than the rectification step of the old process, and the ortho-chlorobenzyl trichloride purity difference obtained by batch production is small, suitable for batch production. In view of the fact that ortho-chlorobenzyl trichloride is obtained by rectification, the number of impurities in ortho-chlorobenzyl trichloride is very small, so the ortho-chlorobenzonitrile obtained after the nitrilation of ortho-chlorobenzyl trichloride and ammonium chloride can be obtained by simple distillation after washing, and the energy consumption increased by the distillation step is very small. Therefore, it can be seen from the above analysis that the distillation step of ortho-chlorobenzyl trichloride rectification plus ortho-chlorobenzonitrile used in the present application is still reduced compared to the old process for rectifying ortho-chlorobenzonitrile with a large amount of impurities, and it can also effectively improve the utilization rate of chlorine, reduce the content of chlorination time and solid waste, reduce the production cost of ortho-chlorobenzyl trichloride, and improve the yield of ortho-chlorobenzonitrile.

[0020] Optionally, in step (3), the weight ratio of o-chlorobenzyl chloride to ammonium chloride is 3.5:1, the reaction temperature is 185-200° C., and the reaction is carried out until the o-chlorobenzyl chloride is below 0.2% to obtain a nitrilation solution.

[0021] The reaction conditions can improve the reaction yield of o-chlorobenzyl trichloride and ammonium chloride and the purity of the product, and are convenient for industrial raw tea processing.

[0022] Optionally, the distillation in step (3) is vacuumed to above -0.09 MPa, and the distillation temperature is 150-220°C.

[0023] Optionally, step (3) further comprises adding a catalyst, wherein the catalyst is selected from copper oxide.

[0024] Catalysts can shorten reaction time, further improve product purity and yield, reduce production costs, and significantly increase production volume in the same amount of time.

[0025] Optionally, the nitrilized liquid is alkaline washed with an alkaline solution having a pH of 8, wherein the alkaline solution is selected from a pure ash solution.

[0026] Selecting an alkaline solution with a pH of 8 for alkaline washing can neutralize and remove the unreacted ammonium chloride, which is convenient for the purification of o-chlorobenzonitrile and will not produce side reactions to o-chlorobenzonitrile itself and subsequent distillation, making it easy for operators to operate.

[0027] Optionally, the weight ratio of the alkaline solution to the nitrilation solution is 1.20:1.18.

[0028] Optionally, in the water washing, the weight ratio of water to nitrilation liquid is 1.10:1.18.

[0029] Optionally, the purity of o-chlorobenzonitrile is greater than 99%.

[0030] Optionally, the yield of o-chlorobenzonitrile is above 95%. The yield of o-chlorobenzonitrile in the original process is 85-90%. The present application can not only reduce the amount of raw materials used, shorten the production time, reduce the generation of solid waste, but also significantly improve the yield of o-chlorobenzonitrile.

[0031] According to another aspect of the present application, provided is o-chlorobenzonitrile prepared by the production process of o-chlorobenzonitrile with high yield described in any one of the above items.

[0032] The beneficial effects of this application include but are not limited to:

[0033] 1. The high-yield o-chlorobenzonitrile production process of the present application can effectively improve the utilization rate of chlorine, reduce the chlorination time and the content of solid waste, reduce the production cost of o-chlorotrichlorobenzyl chloride, and improve the yield of o-chlorobenzonitrile by controlling the double-kettle switching node and switching when the o-chlorobenzyl dichloride content of the main reactor is 4%-9%.

[0034] 2. The high-yield o-chlorobenzonitrile production process of the present application is easier to operate than the original process, breaks through the inherent technical bias in the original process, and innovatively switches between double kettles at a new node, thereby reducing chlorine consumption by more than 10% and shortening the reaction time by more than 15%, making it suitable for industrial mass production. DETAILED DESCRIPTION

[0035] The present application is described in detail below with reference to embodiments, but the present application is not limited to these embodiments.

[0036] Unless otherwise specified, the raw materials in the examples of this application were purchased through commercial channels.

[0037] Example 1

[0038] The present embodiment relates to a production process of o-chlorobenzonitrile with high yield, comprising the following steps:

[0039] (1) A dual reactor connected in series is used to alternately switch as a main reactor and a sub-reactor, the reaction temperature of the main reactor is 140° C., and the reaction temperature of the sub-reactor is 110° C., o-chlorotoluene is placed in the main reactor and the sub-reactor, chlorine gas is introduced into the main reactor for chlorination to obtain a chlorinated liquid, and the sub-reactor absorbs the chlorine gas overflowing from the main reactor. When the content of o-chlorobenzyl chloride in the chlorinated liquid is 4%, the introduction of chlorine gas is stopped, and at this time, the weight ratio of o-chlorotoluene to the introduced chlorine gas is 1:1.8, the chlorinated liquid in the main reactor is discharged, o-chlorotoluene is added again, and the main reactor and the sub-reactor are switched, and the original sub-reactor is used as the main reactor until the content of o-chlorobenzyl chloride in the chlorinated liquid is 4%, then the chlorinated liquid is discharged, and o-chlorotoluene is added again, and the main reactor is repeated. The previous operation is repeated in the main reactor;

[0040] (2) distilling the chlorinated liquid to obtain o-chlorobenzyl trichloride, evacuating the solution to a vacuum level of -0.09 MPa or higher, and setting the distillation temperature in the distillation kettle at 185° C. until the content of o-chlorobenzyl dichloride is less than 0.2%;

[0041] (3) o-chlorobenzyl chloride and ammonium chloride in a weight ratio of 3.5:1 are subjected to cyanidation reaction at 185° C., and the o-chlorobenzyl chloride is reacted until the o-chlorobenzyl chloride is below 0.2% to obtain a cyanidation liquid, the cyanidation liquid is cooled to 100° C., added to a water washing kettle, stirred, and alkaline washed with a pure alkali solution of pH 8, and then a certain amount of water is added for water washing, and stirring is turned off after 1 hour. The mixture is precipitated for 1 hour, and the lower layer is taken to obtain a crude o-chlorobenzonitrile. The crude o-chlorobenzonitrile is added to a distillation kettle, and the mixture is evacuated to above -0.09 MPa, and distilled at 150° C. to obtain o-chlorobenzonitrile.

[0042] Example 2

[0043] The present embodiment relates to a production process of o-chlorobenzonitrile with high yield, comprising the following steps:

[0044] (1) A dual reactor connected in series is used to alternately switch as a main reactor and a sub-reactor, the reaction temperature of the main reactor is 130° C., and the reaction temperature of the sub-reactor is 100° C., o-chlorotoluene is placed in the main reactor and the sub-reactor, chlorine is introduced into the main reactor for chlorination to obtain a chlorinated liquid, and the sub-reactor absorbs the chlorine overflowing from the main reactor. When the content of o-chlorobenzyl chloride in the chlorinated liquid is 9%, the introduction of chlorine is stopped, and at this time, the weight ratio of o-chlorotoluene to the introduced chlorine is 1:1.6, the chlorinated liquid in the main reactor is discharged, o-chlorotoluene is added again, and the main reactor and the sub-reactor are switched, and the original sub-reactor is used as the main reactor until the content of o-chlorobenzyl chloride in the chlorinated liquid is 9%, then the chlorinated liquid is discharged, and o-chlorotoluene is added again, and the main reactor is repeated. The previous operation of the main reactor is repeated;

[0045] (2) distilling the chlorinated liquid to obtain o-chlorobenzyl trichloride, evacuating the solution to a vacuum level of -0.09 MPa or higher, and setting the distillation temperature in the distillation kettle at 190° C. until the content of o-chlorobenzyl dichloride is less than 0.2%;

[0046] (3) o-chlorobenzyl chloride and ammonium chloride in a weight ratio of 3.5:1 are subjected to cyanidation reaction at 200° C., copper oxide accounting for 0.02 wt % of o-chlorobenzyl chloride is added, and the reaction is carried out until the o-chlorobenzyl chloride is below 0.2% to obtain a cyanidation liquid, the cyanidation liquid is cooled to 100° C., added to a water washing kettle, stirred, and alkaline washed with a pure alkali solution with a pH of 8, and then a certain amount of water is added for water washing, and stirring is turned off after 1 hour. The lower layer is taken to obtain a crude o-chlorobenzonitrile, and the crude o-chlorobenzonitrile is added to a distillation kettle, and the vacuum is evacuated to above -0.09 MPa, and o-chlorobenzonitrile is obtained by distillation at 220° C.

[0047] Example 3

[0048] The difference between this embodiment and embodiment 1 is that the reaction temperatures of the main reaction kettle and the auxiliary reaction kettle are the same, both of which are 140° C., and the rest are the same as in embodiment 1 to obtain o-chlorobenzonitrile.

[0049] Example 4

[0050] The difference between this embodiment and embodiment 1 is that no vacuum is applied during the distillation in step (2), and the rest is the same as in embodiment 1 to obtain o-chlorobenzonitrile.

[0051] Comparative Example 1

[0052] The difference between this comparative example and Example 1 is that when the content of o-chlorobenzyl dichloride in the chlorinated liquid is 0.3%, the introduction of chlorine gas is stopped, and at this time, the weight ratio of o-chlorotoluene to the introduced chlorine gas is 1:2, and the rest is the same as Example 1 to obtain o-chlorobenzonitrile.

[0053] Comparative Example 2

[0054] The difference between this comparative example and Example 1 is that step (2) is not performed, and the chlorinated liquid and ammonium chloride are directly subjected to nitrilation reaction. The rest is the same as Example 1 to obtain o-chlorobenzonitrile.

[0055] Test Example 1

[0056] The purity and yield of o-chlorobenzyl trichloride and o-chlorobenzonitrile prepared in the above examples and comparative examples were tested and calculated. The results are shown in Table 1 below.

[0057] Table 1

[0058]

[0059] Test Example 2

[0060] The method of the above embodiment and comparative example was used to produce o-chlorobenzonitrile, and the chlorine consumption and the chlorination time of each reactor when one ton of o-chlorobenzonitrile was prepared were calculated, and the amount of solid waste generated was calculated. The results are shown in Table 2.

[0061] Table 2

[0062] Test No. Chlorine consumption (tons) Chlorination time (h / kettle) Solid waste amount (Kg) Example 1 1.80 35 99 Example 2 1.75 33 95 Example 3 1.80 35 124 Example 4 1.80 35 113 Comparative Example 1 2.04 50 258 Comparative Example 2 2.31 35 247

[0063] According to the contents of Tables 1 and 2, compared with the old process in Comparative Example 1, the purity and yield of o-chlorobenzyl trichloride and o-chlorobenzonitrile prepared by the preparation method of the present application are higher, and less solid waste is generated.

[0064] According to the comparison between Example 1 and Example 3, the increase in the temperature of the secondary still will result in a decrease in the yield of the intermediate product and an increase in the final solid waste, thereby increasing the production cost and post-processing cost of o-chlorobenzonitrile; according to the comparison between Example 1, Example 4 and Comparative Example 2, it can be seen that not evacuating in step (2) does not affect the purity and yield of the intermediate product, but only affects the energy consumption of step (2). Vacuuming can speed up the distillation, thereby reducing energy consumption. If the distillation of step (2) is not performed in the new process, the o-chlorobenzyl dichloride in the chlorinated solution will continue to remain in the system with the reaction of step (3), and finally exist in the form of solid waste. Therefore, more solid waste is generated in Comparative Example 2.

[0065] The above is only the embodiment of the present application, and the protection scope of the present application is not limited by these specific embodiments, but is determined by the claims of the present application. For those skilled in the art, the present application can have various changes and variations. Any modification, equivalent replacement, improvement, etc. made within the technical ideas and principles of the present application should be included in the protection scope of the present application.

Claims

1. A production process for high-yield o-chlorobenzonitrile, characterized in that: The steps include: (1) using a dual reactor connected in series and switching alternately as a main reactor and a sub-reactor, placing o-chlorotoluene in the main reactor and the sub-reactor, introducing chlorine gas into the main reactor for chlorination to obtain a chlorinated liquid, and the sub-reactor absorbing the chlorine gas overflowing from the main reactor. When the content of o-chlorobenzyl chloride in the chlorinated liquid is 4%-9%, the introduction of chlorine gas is stopped, the chlorinated liquid in the main reactor is discharged, o-chlorotoluene is added again, and the main reactor and the sub-reactor are switched, and the original sub-reactor is used as the main reactor until the content of o-chlorobenzyl chloride in the chlorinated liquid is 4%-9%, then the chlorinated liquid is discharged, and o-chlorotoluene is added again, and the main reactor repeats the previous operation; (2) continuously rectifying the chlorinated liquid to continuously obtain o-chlorobenzyl trichloride at the bottom of the rectifying tower; (3) subjecting the o-chlorobenzyl trichloride and ammonium chloride to a nitrilation reaction to obtain a nitrilation liquid, and subjecting the nitrilation liquid to alkali washing, water washing, and distillation to obtain o-chlorobenzonitrile; In the step (2), the vacuum is drawn to above -0.09 MP during the distillation, the distillation temperature in the distillation kettle is 185-190° C., and the distillation is performed until the content of o-chlorobenzyl dichloride is below 0.2%; In step (2), the o-chlorobenzyl dichloride separated from the top of the distillation tower during the distillation is used as a chlorination raw material to continue to pass chlorine to prepare o-chlorobenzyl trichloride; The reaction temperature of the main reactor is 130-140°C, and the reaction temperature of the secondary reactor is 100-110°C.

2. The production process according to claim 1, characterized in that: In the main reaction kettle, the weight ratio of the o-chlorotoluene to the introduced chlorine gas is 1:(1.6-1.8).

3. The production process according to claim 1, characterized in that: In step (3), the weight ratio of o-chlorobenzyl trichloride to ammonium chloride is 3.5:1, the reaction temperature is 185-200° C., and the reaction is carried out until the o-chlorobenzyl trichloride is below 0.2% to obtain a nitrilation solution.

4. The production process according to claim 1, characterized in that: In the distillation of step (3), the vacuum is drawn to above -0.09 MPa, and the distillation temperature is 150-220°C.

5. The production process according to claim 1, characterized in that: Step (3) also includes adding a catalyst, and the catalyst is selected from copper oxide.

6. The production process according to claim 1, characterized in that: The purity of the o-chlorobenzonitrile is greater than 99%.

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