Azeotropic distillation method of 2-chlorobutane

Abstract

The invention relates to the technical field of chemical rectification, and discloses a 2-chlorobutane azeotropic rectification method, which comprises: mixing a 2-chlorobutane crude product with water, and carrying out azeotropic rectification in a rectification tower to obtain a 2-chlorobutane product with a purity of more than or equal to 99.0%, the 2-chlorobutane crude product contains the following components in percentage by weight: 82 to 88 percent of 2-chlorobutane, 0.5 to 2.0 percent of sec-butyl ether and 11 to 17 percent of 2-butene; in the initial mixing system formed by the azeotropic distillation, the content of water is 5.0-10.0 wt%; the tower kettle temperature of azeotropic distillation is 8-12 DEG C higher than the azeotropic point temperature. According to the method, water is selected as the entrainer, so that the process can be simplified, the entrainer can be conveniently separated and recycled, the method has the advantages of low cost, no toxicity, good thermal stability and no corrosion, the number of tower plates for separation of the rectifying tower can be effectively reduced, the use amount of heating steam and the use amount of tower top cooling water can be remarkably reduced, and energy consumption is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of chemical distillation, and in particular to an azeotropic distillation method for 2-chlorobutane. Background Art

[0002] Azeotropic phenomenon refers to the phenomenon that when a solution boils under a certain pressure, the solution temperature, liquid phase composition and vapor phase composition remain unchanged. When mixing, the azeotropic point of the mixture is higher or lower than the boiling point of any component in the mixture, which is called the highest azeotrope or the lowest azeotrope respectively. When the azeotropic phenomenon occurs, the purpose of separation cannot be achieved by ordinary distillation methods. At this time, special distillation methods such as azeotropic distillation, extractive distillation or pressure swing distillation are used. Azeotropic distillation is to add a new component (entrainer) to the system to be separated. The entrainer can form a new azeotrope with one or more components in the original system, and the volatility of this new azeotrope is significantly higher or lower than the volatility of the original components. In addition, the content of each component in the new azeotrope is different from the composition of the raw liquid, and it can be separated by ordinary distillation methods.

[0003] Under a certain pressure, based on the different boiling points of different components in the mixed material, the mixture is heated to make it boil, and then the steam is condensed back into liquid to separate the different components. In the chemical industry, most distillation devices adopt a continuous operation mode. The reflux liquid at the top of the tower and the rising steam gas at the bottom of the tower are necessary conditions for maintaining continuous distillation. The specific operation process of distillation is as follows: first, the raw materials are continuously added to the distillation tower, part of the liquid is vaporized, and rising steam is generated, which passes through each layer of the distillation tower at one time. The steam rising to the top of the tower enters the condenser and is completely condensed. Part of the condensed liquid is sent back to the top of the tower by gravity as the reflux liquid, and the rest of the condensed liquid is extracted as the top output product.

[0004] In the traditional 2-chlorobutane distillation process, it is necessary to maintain a high tower bottom temperature and tower top temperature, as well as a larger reflux production ratio, in order to separate 2-chlorobutane. Most of the energy consumed is not used for component separation, but is taken away by the cooling water at the top of the distillation tower. The actual heat energy used for component separation is only about 5%. Therefore, the rational use of heat energy in the distillation process and the reduction of energy waste are of great significance to promoting the sustainable development of national energy. Summary of the invention

[0005] The purpose of the present invention is to provide a more energy-saving and environmentally friendly azeotropic distillation method for 2-chlorobutane.

[0006] In order to achieve the above object, the present invention provides an azeotropic distillation method for 2-chlorobutane, which comprises: mixing a crude 2-chlorobutane product with water and performing azeotropic distillation in a distillation tower to obtain a 2-chlorobutane product with a purity of ≥99.0wt%;

[0007] The crude 2-chlorobutane product contains 82-88 wt% of 2-chlorobutane, 0.5-2.0 wt% of sec-butyl ether, and 11-17 wt% of 2-butene;

[0008] In the initial mixed system formed by the azeotropic distillation, the water content is 5.0-10.0wt%;

[0009] The bottom temperature of the azeotropic distillation tower is 8-12° C. higher than the azeotropic point temperature, and the azeotropic point is the azeotropic point of the azeotrope formed by the 2-chlorobutane and the water.

[0010] Compared with the prior art, the technical solution provided by the present invention has at least the following advantages:

[0011] (1) The technical solution provided by the present invention uses water as an azeotrope to form an azeotrope with 2-chlorobutane in the system to be separated, which can significantly affect the gas-liquid equilibrium relationship of the key components in the system to be separated. The azeotrope is more than 10°C lower than the original azeotropic point of the components in the system to be separated. In addition, the present invention strictly controls the amount of the azeotrope water so that it can form an azeotrope with 2-chlorobutane, further reducing the energy consumption in the azeotropic distillation process.

[0012] (2) The technical solution provided by the present invention can effectively reduce the number of plates for separation in a distillation tower, and the separation purpose can be achieved by using a smaller number of plates, thus saving energy consumption.

[0013] (3) The technical solution provided by the present invention can significantly reduce the amount of heating steam and the amount of cooling water at the top of the tower, saving energy consumption.

[0014] (4) The technical solution provided by the present invention can effectively reduce the reflux production ratio of the distillation tower. Even when the reflux production ratio is 1:1, the separation purpose can still be achieved, which not only saves energy consumption in the distillation process, but also improves production efficiency.

[0015] (5) The technical solution provided by the present invention uses water that forms a heterogeneous azeotrope as an azeotropic agent. On the one hand, it can simplify the process and facilitate the separation and recovery of the azeotropic agent; on the other hand, water has the advantages of being cheap, non-toxic, thermally stable and non-corrosive. DETAILED DESCRIPTION

[0016] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range 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 considered as specifically disclosed in this article.

[0017] As mentioned above, the present invention provides an azeotropic distillation method for 2-chlorobutane, which comprises: mixing a crude 2-chlorobutane product with water and performing azeotropic distillation in a distillation tower to obtain a 2-chlorobutane product with a purity of ≥99.0wt%;

[0018] The crude 2-chlorobutane product contains 82-88 wt% of 2-chlorobutane, 0.5-2.0 wt% of sec-butyl ether, and 11-17 wt% of 2-butene;

[0019] In the initial mixed system formed by the azeotropic distillation, the water content is 5.0-10.0wt%;

[0020] The bottom temperature of the azeotropic distillation tower is 8-12° C. higher than the azeotropic point temperature, and the azeotropic point is the azeotropic point of the azeotrope formed by the 2-chlorobutane and the water.

[0021] The crude 2-chlorobutane product of the present invention may also contain other impurities, such as 1-chlorobutane, etc., which will not be described in detail herein, and those skilled in the art should not interpret this as limiting the present invention.

[0022] When performing the azeotropic distillation of the present invention, the amount of entrainer water has an important influence on obtaining a higher purity 2-chlorobutane product under a lower energy consumption. If the amount of water is too much, most of the mixed system is water, and the 2-chlorobutane content is small, which leads to a small 2-chlorobutane content in the evaporated product, and the heat required for distillation is higher; if the amount of water is too little, water and 2-chlorobutane cannot form an azeotrope, and the purpose of azeotropic distillation cannot be achieved. The inventor of the present invention has found in research that when the water content in the initial mixed system formed by azeotropic distillation is kept at 5.0-10.0wt%, preferably 6.0-8.0wt%, water and 2-chlorobutane can successfully form an azeotrope to obtain a high-purity 2-chlorobutane product, and the entire distillation process is more energy-saving and environmentally friendly.

[0023] Preferably, the bottom temperature of the distillation tower is 8-10° C. higher than the azeotropic point temperature.

[0024] Preferably, the bottom temperature of the distillation tower is 63-67°C, and the top temperature is 60-65°C.

[0025] In a particularly preferred case, the present invention controls the conditions so that the azeotropic point of the material in the distillation tower is 55° C., and controls the bottom temperature of the distillation tower to be 63-65° C., and the top temperature of the tower to be 60-63° C. The inventors of the present invention have found in their research that under this preferred condition, the technical solution provided by the present invention is more in line with the requirements of energy conservation and environmental protection, and can significantly reduce the amount of heating steam at the bottom of the tower and the amount of cooling water at the top of the tower compared to the traditional distillation method that does not use water as an azeotropic agent, and the number of tower plates required is less.

[0026] Preferably, the top pressure of the distillation tower is 0-0.5 KPa.

[0027] The tower top pressure described in the present invention refers to the gauge pressure.

[0028] Preferably, the distillation tower has a theoretical plate number of 8-15, preferably 10-13.

[0029] Preferably, the reflux-to-production ratio of the azeotropic distillation is 1-3:1, more preferably 2:1. In the distillation operation, the size of the reflux-to-production ratio has an important influence on the separation effect and economy of the distillation process. Although increasing the reflux-to-production ratio of the azeotropic distillation can improve the purity of the product, it will reduce the production capacity of the tower and increase the consumption of water, electricity and gas. The technical solution provided by the present invention can still produce high-purity 2-chlorobutane products under the condition of a reflux-to-production ratio of 2:1, which greatly reduces production energy consumption and improves production efficiency.

[0030] According to a preferred specific implementation, the distillation tower is heated by indirect steam heating, and the temperature of the steam is 100-120° C., and the amount used is 30-50 kg / h.

[0031] Preferably, the temperature of the cooling water at the top of the distillation tower is 20-25°C, and the amount is 10-15m 3 / h.

[0032] According to a preferred specific embodiment, the method further comprises: mixing the crude 2-chlorobutane product with water and performing azeotropic distillation in a distillation tower to obtain a tower top distillate and a tower bottom distillate, respectively, and performing static stratification on the tower top distillate to obtain a 2-chlorobutane product as an upper oil phase.

[0033] Preferably, when the content of the sec-butyl ether in the bottom distillate reaches 90 wt % or more, the azeotropic distillation is stopped.

[0034] Preferably, the conditions of the azeotropic distillation of the present invention are controlled so that the content of sec-butyl ether in the obtained 2-chlorobutane product is below 0.1 wt %, more preferably below 0.05 wt %.

[0035] The present invention will be described in detail below by way of examples. In the following examples, unless otherwise specified, the raw materials are all commercially available.

[0036] In the following examples, the crude 2-chlorobutane product used contained: 85 wt% 2-chlorobutane, 1.2 wt% sec-butyl ether, and 13.2 wt% 2-butene;

[0037] Example 1

[0038] The distillation tower is heated by indirect steam heating, and the crude 2-chlorobutane product is mixed with water and then subjected to azeotropic distillation in the distillation tower to obtain a tower top distillate and a tower bottom distillate respectively, until the content of sec-butyl ether in the tower bottom distillate reaches more than 90wt%, the azeotropic distillation is stopped, and the tower top distillate is allowed to stand for stratification to obtain a 2-chlorobutane product as an upper oil phase.

[0039] The water content in the initial mixed system formed by azeotropic distillation, the condition parameters of azeotropic distillation and the purity of 2-chlorobutane product are listed in Table 1.

[0040] Embodiment 2-4

[0041] The process is similar to that of Example 1, except that the parameters of the conditions used are different, see Table 1 for details.

[0042] The 2-chlorobutane product is prepared.

[0043] Comparative Example 1

[0044] The crude 2-chlorobutane product is distilled by conventional distillation method;

[0045] The distillation tower is heated by indirect steam heating, and the crude 2-chlorobutane product is introduced into the distillation tower for distillation treatment without using water as an azeotropic agent. The other condition parameters are shown in Table 1.

[0046] The 2-chlorobutane product is prepared.

[0047] Comparative Examples 2-4

[0048] The process is similar to that of Example 1, except that the parameters of the conditions used are different, see Table 1 for details.

[0049] The 2-chlorobutane product is prepared.

[0050] Table 1

[0051]

[0052] It can be seen from the data in the above table that the technical solution provided by the present invention can reduce the amount of heating steam and cooling water used, and significantly reduce the production energy consumption of 2-chlorobutane products.

[0053] Compared with Comparative Example 1, Example 1 using the technical solution claimed in the present invention reduces the bottom temperature and the top temperature during the distillation process, which can reduce the amount of steam used, reduce the reflux production ratio from the original 3:1 to 1:1, and reduce the number of required plates from 16 to 13. Under the premise of ensuring the high purity of the 2-chlorobutane product, not only the production efficiency of the product is improved, but also the production energy consumption is greatly reduced.

[0054] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. An azeotropic distillation method for 2-chlorobutane, characterized in that: The method comprises: mixing a crude 2-chlorobutane product with water and performing azeotropic distillation in a distillation tower to obtain a 2-chlorobutane product with a purity of ≥99.0%; The crude 2-chlorobutane product contains 82-88 wt% of 2-chlorobutane, 0.5-2.0 wt% of sec-butyl ether, and 11-17 wt% of 2-butene; In the initial mixed system formed by the azeotropic distillation, the water content is 5.0-10.0wt%; The bottom temperature of the azeotropic distillation tower is 8-12° C. higher than the azeotropic point temperature, and the azeotropic point is the azeotropic point of the azeotrope formed by the 2-chlorobutane and the water.

2. The method according to claim 1, characterized in that The bottom temperature of the distillation tower is 8-10° C. higher than the azeotropic point temperature.

3. The method according to claim 2, characterized in that The bottom temperature of the distillation tower is 63-67°C, and the top temperature is 60-65°C.

4. The method according to any one of claims 1 to 3, characterized in that: The top pressure of the distillation tower is 0-0.5 KPa.

5. The method according to any one of claims 1 to 4, characterized in that: The number of theoretical plates of the distillation tower is 8-15, preferably 10-13.

6. The method according to any one of claims 1 to 5, characterized in that: The reflux-to-production ratio of the azeotropic distillation is 1-3:

1.

7. The method according to any one of claims 1 to 6, characterized in that: The distillation tower is heated by indirect steam heating, and the temperature of the steam is 100-120° C. and the amount is 30-50 kg / h.

8. The method according to any one of claims 1 to 7, characterized in that: The temperature of the cooling water at the top of the distillation tower is 20-25°C, and the amount is 10-15m 3 / h.

9. The method according to any one of claims 1 to 8, characterized in that: The method further comprises: mixing the crude 2-chlorobutane product with water and performing azeotropic distillation in a distillation tower to obtain a tower top distillate and a tower bottom distillate respectively, and performing static stratification on the tower top distillate to obtain a 2-chlorobutane product as an upper oil phase.

10. The method according to claim 9, characterized in that When the content of the sec-butyl ether in the distillate at the bottom of the tower reaches more than 90 wt %, the azeotropic distillation is stopped.

Images