Process method for separating impurity-containing dichlorotoluene isomeride
By using tributylmethylammonium bistrifluoroformolimide as extraction agent, combined with the design of separation towers C1 and C2, the high energy consumption and high energy consumption caused by the close boiling point during the separation of dichlorotoluene isomers is solved. Investment issues have achieved efficient separation of light and heavy components and recycling of extractants.
Patent Information
- Application Number
- CN202411225203.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-03
- Publication Date
- 2024-12-13
AI Technical Summary
It is difficult to efficiently separate impurity-containing dichlorotoluene isomers, especially due to their close boiling points, which leads to large investment in the separation process and high energy consumption.
Using tributylmethylammonium bistrifluoroformolimide as the extraction agent, the separation of the separation column C1 and C2 are combined to achieve the separation of the dichlorotoluene isomer and the extraction agent cycle use.
It reduces the difficulty of separation, improves the separation efficiency, and achieves high-purity dichlorotoluene isomer separation, which requires lower theoretical level and reflux ratio than conventional methods, significantly reducing investment and energy consumption.
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Abstract
Description
Technical Field
[0001] The invention relates to the technical field of separation of chloride isomers, in particular to a process for separating dichlorotoluene isomers containing impurities. Background Art
[0002] Dichlorotoluene is an important raw material or solvent for fine chemical or pharmaceutical production. In the production process of dichlorotoluene, the logistics obtained after the catalytic reaction often contains a variety of dichlorotoluene isomers, such as 2,3-dichlorotoluene, 2,4-dichlorotoluene, 2,5-dichlorotoluene, 2,6-dichlorotoluene, 3,4-dichlorotoluene and 3,5-dichlorotoluene. Due to the extremely similar structures between isomers, the difference in their boiling points is extremely small, as shown in Table 1. Among them, 2,4-dichlorotoluene, 2,5-dichlorotoluene and 2,6-dichlorotoluene are the main components in the mixture, and their boiling points are very close; while 2,3-dichlorotoluene, 3,4-dichlorotoluene and 3,5-dichlorotoluene are less in content and have similar boiling points; at the same time, the boiling point of 3,5-dichlorotoluene is between the product and the impurity, and is closer to the main component. Therefore, the complex isomer mixture system needs to be purified and removed by special methods to obtain the target dichlorotoluene product with high purity.
[0003] Table 1 Basic physical properties of dichlorotoluene isomers
[0004] Substance name CAS Number <![CDATA[Density (20 °C), g / cm 3 > Boiling point,℃ Melting point,℃ 2,3-Dichlorotoluene 32768-54-0 1.2280 207.5 6.0 2,4-Dichlorotoluene 95-73-8 1.2476 201.1 -13.5 2,5-Dichlorotoluene 19398-61-9 1.2420 200.0 4.5 2,6-Dichlorotoluene 118-69-4 1.2686 198.0 -1.2 3,4-Dichlorotoluene 95-75-0 1.2510 208.9 -15.2 3,5-Dichlorotoluene 25186-47-4 1.2420 203.4 26.0
[0005] According to the boiling points of the dichlorotoluene isomers shown in Table 1, their relative volatility characteristics can be known. The relative volatility between the main components 2,4-dichlorotoluene, 2,5-dichlorotoluene and 2,6-dichlorotoluene and the remaining components is relatively large. 2,3-dichlorotoluene, 3,4-dichlorotoluene and 3,5-dichlorotoluene can be first separated from the main components by ordinary distillation methods. However, due to the close boiling points, more theoretical stages are still required for separation, which makes the process investment large and the energy consumption high.
[0006] In view of the above-mentioned defects, the present invention aims to create a solvent and a process for separating isomers of dichlorotoluene containing impurities, so as to make it more valuable for industrial utilization. Summary of the invention
[0007] In order to solve the above technical problems, the purpose of the present invention is to provide a solvent and a process for separating dichlorotoluene isomers containing impurities. The dichlorotoluene isomers treated in this application are a mixture of 2,3-dichlorotoluene, 2,4-dichlorotoluene, 2,5-dichlorotoluene, 2,6-dichlorotoluene, 3,4-dichlorotoluene and 3,5-dichlorotoluene. Among them, 2,4-dichlorotoluene, 2,5-dichlorotoluene and 2,6-dichlorotoluene are the main product components, with a total mass composition of 90%, and each substance composition is 30% respectively. The mixture mainly containing these three isomers will be referred to as a light component in the following text; 2,3-dichlorotoluene, 3,4-dichlorotoluene and 3,5-dichlorotoluene are impurity components, with a total mass composition of 10%, and each substance composition is 6%, 2% and 2% respectively. The mixture mainly containing these three isomers will be referred to as a heavy component in the following text. In order to improve the impurity removal and separation efficiency of dichlorotoluene isomers, the present application provides a process for separating dichlorotoluene isomers containing impurities.
[0008] The invention discloses a process for separating isomers of dichlorotoluene containing impurities. The separation method is based on extractive distillation using tributylmethylammonium bis(trifluoromethylxanthimide) as an extractant.
[0009] A process for separating isomers of dichlorotoluene containing impurities comprises the following separation steps:
[0010] (1) injecting a dichlorotoluene isomer mixture of 2,3-dichlorotoluene, 2,4-dichlorotoluene, 2,5-dichlorotoluene, 2,6-dichlorotoluene, 3,4-dichlorotoluene and 3,5-dichlorotoluene with mass contents of 6%, 30%, 30%, 30%, 2% and 2% respectively and an extractant into a separation tower C1;
[0011] (2) After extractive distillation through a separation tower C1, a high-purity light component mixture of 2,4-dichlorotoluene, 2,5-dichlorotoluene and 2,6-dichlorotoluene is obtained at the top of the tower;
[0012] (3) injecting the bottom stream of separation tower C1 into separation tower C2, and obtaining a high-purity heavy component mixture of 2,3-dichlorotoluene, 3,4-dichlorotoluene and 3,5-dichlorotoluene at the top of the tower after distillation and separation;
[0013] (4) The extractant coming out of the kettle of separation tower C2 is refluxed into separation tower C1 to recycle the extractant.
[0014] Furthermore, the extractant in step (1) is tributylmethylammonium bis(trifluoromethylxanthine).
[0015] Furthermore, in step (1), the mass flow rate ratio of the extractant to the dichlorotoluene isomer mixture is 2 to 6.
[0016] Furthermore, in step (1), the mass flow rate ratio of the extractant to the dichlorotoluene isomer mixture is 3 to 5.
[0017] Furthermore, in the steps (1) to (3), the theoretical stage of the separation tower C1 is 40 to 60; the operating pressure at the top of the tower is 1 to 10 kPa; the temperature of the tower bottom is not higher than 150° C.; the mass reflux ratio at the top of the tower is 3 to 6; the extractant enters from the 2nd to 10th theoretical stage at the top of the C1 tower, and the dichlorotoluene mixture enters from the 30th to 55th theoretical stage at the middle and lower part of the C1 tower.
[0018] Furthermore, in steps (1) to (3), the operating pressure at the top of the separation tower C1 is 5 to 8 kPa; and the temperature at the bottom of the tower is 130 to 145°C.
[0019] Furthermore, in the steps (4) and (5), the theoretical stage of the separation tower C2 is 8 to 16; the operating pressure at the top of the tower is 1 to 5 kPa; the temperature of the bottom of the tower is not higher than 180°C; the mass reflux ratio at the top of the tower is 0.1 to 2; and logistics 4 enters from the 8th to 14th theoretical stage in the middle of the separation tower C2.
[0020] Furthermore, in the steps (4) and (5), the operating pressure at the top of the separation tower C2 is 2-3 kPa; and the temperature at the bottom of the tower is 165-175°C.
[0021] By means of the above scheme, the present invention has at least the following advantages:
[0022] The use of the extractant of the present invention in combination with the separation tower can efficiently achieve the separation of the light and heavy components of dichlorotoluene isomers. Compared with the conventional separation scheme, if the same separation effect is to be achieved, the conventional separation scheme requires more than 100 theoretical levels and a high reflux ratio, while the present invention achieves a lower theoretical level and a low reflux ratio through the combination of the extractant, which means low investment and low energy consumption. The extractive distillation method of the present invention can greatly reduce the difficulty of separating dichlorotoluene isomers and improve the separation efficiency of the process.
[0023] The endpoints and any values of the scope disclosed in the present invention are not limited to the precise scope or value, and these scopes or values should be understood to include values close to these scopes or values. For numerical ranges, the endpoint values of each scope, the endpoint values of each scope and the individual point values, and the individual point values can be combined with each other to obtain one or more new numerical ranges, which should be regarded as specifically disclosed in this article. Hereinafter, in principle, each technical solution can be combined with each other to obtain a new technical solution, which should also be regarded as specifically disclosed in this article.
[0024] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention and implement it according to the contents of the specification, the following is a detailed description of the preferred embodiments of the present invention in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS
[0025] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show a certain embodiment of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.
[0026] Figure 1 It is a schematic flow diagram of a process for separating isomers of dichlorotoluene containing impurities according to the present invention; DETAILED DESCRIPTION
[0027] The present invention is described in detail below in conjunction with specific drawings and embodiments. It is necessary to point out that the following embodiments are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made to the present invention by those skilled in the art based on the content of the present invention still fall within the scope of protection of the present invention.
[0028] It should also be noted that the various specific technical features described in the following specific embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the present invention will not further describe various possible combinations.
[0029] In addition, the various embodiments of the present invention may be arbitrarily combined as long as they do not violate the concept of the present invention. The technical solutions thus formed belong to part of the original disclosure of this specification and also fall within the protection scope of the present invention.
[0030] The raw materials used in the examples and comparative examples, unless otherwise specified, are disclosed in the prior art, for example, they can be directly purchased or prepared according to the preparation methods disclosed in the prior art.
[0031] Unless otherwise specified, all percentages, ratios, etc. mentioned in this specification are based on weight, unless the weight basis does not conform to the common understanding of those skilled in the art.
[0032] Unless otherwise specified, all pressures mentioned in this specification are absolute pressures.
[0033] The present invention will be further described below through specific implementation modes.
[0034] The separation process of the present invention is as follows Figure 1, the extractant is supplied into the tower from the top of the C1 tower through logistics 1; at the same time, the mixed flow 2 composed of 2,3-dichlorotoluene, 2,4-dichlorotoluene, 2,5-dichlorotoluene, 2,6-dichlorotoluene, 3,4-dichlorotoluene and 3,5-dichlorotoluene enters C1 from the middle and lower part of the C1 tower. After extractive distillation, the light component mixture (logistics 3) 2,4-dichlorotoluene, 2,5-dichlorotoluene and 2,6-dichlorotoluene is obtained at the top of the extractive distillation tower C1, which is discharged out of the system for further separation and purification, and the remaining material 4 at the bottom of the tower is then sent to the C2 tower for separation. The heavy component mixture (logistics 5) 2,3-dichlorotoluene, 3,4-dichlorotoluene and 3,5-dichlorotoluene is obtained from the top of the C2 tower and discharged out of the system for further use; the pure extractant obtained at the bottom of the C2 tower is circulated to the mixer M1, mixed with the fresh supplementary extractant logistics 7 and then enters the C1 tower to achieve recycling.
[0035] Example 1
[0036] The dichlorotoluene isomer feed components include 2,3-dichlorotoluene, 2,4-dichlorotoluene, 2,5-dichlorotoluene, 2,6-dichlorotoluene, 3,4-dichlorotoluene and 3,5-dichlorotoluene, and their mass contents in the mixture are 6%, 30%, 30%, 30%, 2% and 2%, respectively. Among them, the mixture of 2,4-dichlorotoluene, 2,5-dichlorotoluene and 2,6-dichlorotoluene is called light component; 2,3-dichlorotoluene, 3,4-dichlorotoluene and 3,5-dichlorotoluene are defined as impurities, and their mixture is called heavy component.
[0037] Tributyl methylammonium bis(trifluoromethylsulfonimide) was used as the extractant, the mass ratio of the feed flow rate of the extractant stream 1 to the flow rate of the dichlorotoluene mixture stream 2 was 5, the operating pressure of the tower C1 was 7 kPa, according to Figure 1 The process separates dichlorotoluene isomers, and the implementation steps are as follows:
[0038] (a) a mixed stream 2 of six dichlorotoluene isomers, namely 2,3-dichlorotoluene, 2,4-dichlorotoluene, 2,5-dichlorotoluene, 2,6-dichlorotoluene, 3,4-dichlorotoluene and 3,5-dichlorotoluene, formed according to the above mass composition, enters the tower from the 40th theoretical stage of tower C1;
[0039] (b) at the same time, the extractant tributyl methyl ammonium bis trifluoromethyl xanthamide stream 1 enters the tower from the fifth theoretical stage of tower C1;
[0040] (c) The pressure at the top of tower C1 is 7 kPa, the temperatures at the top and bottom of the tower are 115° C. and 140° C. respectively, and the total theoretical stage of the tower is 50. Under these conditions, the light component at the top of the tower is separated and obtained, and the purity is 99.97%, of which the heavy component impurity is 0.013%. The mixed flow 4 of the heavy component and the extractant in the bottom of the tower enters the C2 tower at the entry position 6;
[0041] (d) The top pressure of tower C2 is 3 kPa, the top and bottom temperatures are 91° C. and 168° C. respectively, and the total theoretical stage of the tower is 12. Under these conditions, the top heavy component stream 5 separated and obtained has a purity of 99.58%, of which the light component content is 0.269%;
[0042] (e) The extractant 6 at the bottom of tower C2 is circulated to mixer M1, mixed with fresh supplementary extractant 7 and then enters tower C1 to achieve recycling, with an extractant recovery rate of 99.99%. The amount of fresh supplementary extractant is represented by the supplement rate, that is, the ratio of the supplementary extractant flow rate to the circulating extractant flow rate, which is 0.0055%.
[0043] The detailed information of this embodiment is shown in Table 2. Based on the process conditions, the purity of the light component is 99.97%, and the purity of the heavy component is 99.58%.
[0044] Example 2
[0045] The feed, extractant and composition are the same as in Example 1. Figure 1 The process is to separate the light and heavy components in the dichlorotoluene isomer mixture, and the implementation steps are basically the same as the method in Example 1, except that the theoretical stage of the tower C1 is 60. The detailed conditions and results of this example are listed in Table 2.
[0046] Based on this condition, a light component with a purity of 99.98% and a heavy component with a purity of 99.68% can be obtained, the impurity content of the heavy component in the light component is 0.009%, and the content of the light component in the heavy component is 0.180%.
[0047] Example 3
[0048] The feed, extractant and composition are the same as in Example 1. Figure 1 The process is to separate the light and heavy components in the dichlorotoluene isomer mixture, and the implementation steps are basically the same as the method of Example 1, except that the top operating pressure of the tower C1 and the tower C2 is 5 kPa. The detailed conditions and results of this example are listed in Table 2.
[0049] Based on this condition, a light component with a purity of 99.97% and a heavy component with a purity of 99.55% can be obtained, the impurity content of the heavy component in the light component is 0.018%, and the content of the light component in the heavy component is 0.179%.
[0050] Example 4
[0051] The feed, extractant and composition are the same as in Example 1. Figure 1The process is to separate the light and heavy components in the dichlorotoluene isomer mixture, and the implementation steps are basically the same as the method in Example 1, except that the reflux ratios of tower C1 and tower C2 are 10 and 1.8 respectively. The detailed conditions and results of this example are listed in Table 2.
[0052] Based on this condition, a light component with a purity of 99.98% and a heavy component with a purity of 99.80% can be obtained, the impurity content of the heavy component in the light component is 0.010%, and the content of the light component in the heavy component is 0.090%.
[0053] Comparative Example 1
[0054] The feed and composition are the same as in Example 1, no extractant is added, and the dichlorotoluene isomers are directly separated by the C1 tower, and the operating conditions and implementation steps of the C1 tower are consistent with those of Example 1. The detailed conditions and results of this example are listed in Table 2.
[0055] Based on this condition, a light component with a purity of 93.52% and a heavy component with a purity of 16.76% can be obtained, the impurity content of the heavy component in the light component is 6.48%, and the light component content in the heavy component is 83.24%.
[0056] Comparative Example 2
[0057] The feed and composition are the same as those in Example 1, but no extractant is added, and the dichlorotoluene isomers are directly separated by the C1 column. The detailed conditions and results of this example are listed in Table 2.
[0058] Based on this condition, a light component with a purity of 99.98% and a heavy component with a purity of 98.58% can be obtained, the impurity content of the heavy component in the light component is 0.020%, and the light component content in the heavy component is 1.42%.
[0059] Comparative Example 3
[0060] The feed, extractant and composition are the same as in Example 1. Figure 1 The process is to separate the light and heavy components in the dichlorotoluene isomer mixture, and the implementation steps are basically the same as the method of Example 1, except that the extractant is injected into the C1 column at a ratio of 1:1 between the extractant and the oil. The detailed conditions and results of this example are listed in Table 2.
[0061] Based on this condition, a light component with a purity of 99.80% and a heavy component with a purity of 78.67% can be obtained, the impurity content of the heavy component in the light component is 0.19%, and the light component content in the heavy component is 21.31%.
[0062] Table 2
[0063]
[0064]
[0065] From the results of the embodiments and comparative examples, it can be seen that when the extractant is not used, the separation of the light and heavy components of the dichlorotoluene isomers cannot be achieved by using the same separation conditions as those using the extractant, see Comparative Example 1; if the same separation effect is to be achieved, the conventional separation scheme requires more than 100 theoretical levels and a high reflux ratio, see Comparative Example 2, which means high investment and high energy consumption, and the method of extractive distillation can greatly reduce the difficulty of separating the dichlorotoluene isomers and improve the separation efficiency of the process.
[0066] The present invention has been described in detail above in conjunction with specific implementations and exemplary examples, but these descriptions cannot be understood as limiting the present invention. Those skilled in the art understand that, without departing from the spirit and scope of the present invention, a variety of equivalent substitutions, modifications or improvements may be made to the technical solution of the present invention and its implementation methods, all of which fall within the scope of the present invention. The scope of protection of the present invention shall be subject to the attached claims.
[0067] All publications, patent applications, patents and other references mentioned in this specification are incorporated herein by reference. Unless otherwise defined, all technical and scientific terms used in this specification have the meanings conventionally understood by those skilled in the art. In the event of a conflict, the definition in this specification shall prevail.
[0068] When this specification uses the prefix "well-known to those skilled in the art", "prior art" or similar terms to introduce materials, substances, methods, steps, devices or components, etc., the objects introduced by the prefix cover those commonly used in the art when this application is filed, but also include those that are not commonly used at present but will become recognized in the art as being suitable for similar purposes.
[0069] In the context of the present specification, any matters or items not mentioned are directly applicable to those known in the art without any changes except those explicitly stated.
Claims
1. A process for separating isomers of dichlorotoluene containing impurities, characterized in that: The separation method is an extractive distillation based on tributylmethylammonium bis(trifluoromethylxanthamide) extractant.
2. A process for separating isomers of dichlorotoluene containing impurities as claimed in claim 1, characterized in that: The method comprises the following separation steps: (1) injecting a dichlorotoluene isomer mixture of 2,3-dichlorotoluene, 2,4-dichlorotoluene, 2,5-dichlorotoluene, 2,6-dichlorotoluene, 3,4-dichlorotoluene and 3,5-dichlorotoluene with mass contents of 6%, 30%, 30%, 30%, 2% and 2% respectively and an extractant into a separation tower C1; (2) After extractive distillation through a separation tower C1, a high-purity light component mixture of 2,4-dichlorotoluene, 2,5-dichlorotoluene and 2,6-dichlorotoluene is obtained at the top of the tower; (3) injecting the bottom stream of separation tower C1 into separation tower C2, and obtaining a high-purity heavy component mixture of 2,3-dichlorotoluene, 3,4-dichlorotoluene and 3,5-dichlorotoluene at the top of the tower after distillation and separation; (4) The extractant coming out of the kettle of separation tower C2 is refluxed into separation tower C1 to recycle the extractant.
3. A process for separating isomers of dichlorotoluene containing impurities according to claim 2, characterized in that: The extractant in step (1) is tributylmethylammonium bis(trifluoromethylxanthine).
4. A process for separating isomers of dichlorotoluene containing impurities according to claim 2, characterized in that: The mass flow rate ratio of the extractant to the dichlorotoluene isomer mixture in step (1) is 2 to 6.
5. A process for separating isomers of dichlorotoluene containing impurities according to claim 2, characterized in that: The mass flow rate ratio of the extractant to the dichlorotoluene isomer mixture in step (1) is 3 to 5.
6. A process for separating isomers of dichlorotoluene containing impurities according to claim 2, characterized in that: In the steps (1) to (3), the separation tower C1 has 40 to 60 theoretical stages; the tower top operating pressure is 1 to 10 kPa; the tower bottom temperature is not higher than 150° C.; the tower top mass reflux ratio is 3 to 6; the extractant enters from the 2nd to 10th theoretical stage of the upper part of the C1 tower, and the dichlorotoluene mixture enters from the 30th to 55th theoretical stage of the lower part of the C1 tower.
7. A process for separating isomers of dichlorotoluene containing impurities according to claim 2, characterized in that: In steps (1) to (3), the operating pressure at the top of separation tower C1 is 5-8 kPa; and the temperature at the bottom of the tower is 130-145°C.
8. A process for separating isomers of dichlorotoluene containing impurities according to claim 2, characterized in that: In the steps (4) and (5), the separation tower C2 has 8 to 16 theoretical stages; the tower top operating pressure is 1 to 5 kPa; the tower bottom temperature is not higher than 180°C; the tower top mass reflux ratio is 0.1 to 2; and logistics 4 enters from the 8th to 14th theoretical stages in the middle of the separation tower C2.
9. A process for separating isomers of dichlorotoluene containing impurities according to claim 2, characterized in that: In the steps (4) and (5), the operating pressure at the top of the separation tower C2 is 2-3 kPa; and the temperature at the bottom of the tower is 165-175°C.