A method for separating cis / trans-1,2-dichloroethylene

Abstract

The present invention discloses a method for separating cis- and trans-1,2-dichloroethylene. A hetero[4]arene crystal material having a structure shown in the following formula is used as an adsorbent to selectively adsorb trans-1,2-dichloroethylene, thereby separating a cis- and trans-1,2-dichloroethylene mixture. The separation process of the present invention is simple to operate, has excellent separation performance, and requires low equipment. It does not require a distillation operation, has low energy consumption, saves energy, and reduces production costs. The crystal material used is highly stable and recyclable, and the separation effect does not significantly decrease after repeated recycling.

Description

Technical Field

[0001] The present invention relates to the technical field of adsorption separation, and in particular to a method for separating cis / trans-1,2-dichloroethylene. Background Art

[0002] Olefins are high-value chemical raw materials used in industrial production. They are widely used as basic organic chemical raw materials for the synthesis of a wide variety of intermediates and products, and have a significant impact on all aspects of human production and life.

[0003] Halogenated alkenes are typically prepared through the halogenation of alkenes, which often results in the simultaneous production of geometric isomers. Since each isomer exhibits specific properties and uses in specific applications, the separation of cis- and trans-isomerized halogenated alkenes has attracted increasing attention in both the scientific and industrial communities in recent years.

[0004] The two cis and trans isomers of dichloroethylene, cis-1,2-dichloroethylene (cis-DCE) and trans-1,2-dichloroethylene (trans-DCE), are both chemical raw materials with high industrial value and can be used as basic units to synthesize copolymer materials. On the other hand, their applications in human life are completely different.

[0005] Cis-1,2-dichloroethylene is commonly used to prepare various enediynes for Bergman cyclization and as a foaming additive. Compared to cis-1,2-dichloroethylene, trans-1,2-dichloroethylene is less toxic and more chemically active, primarily used as an extractant for heat-sensitive substances or as a solvent for certain polymers.

[0006] Therefore, separating and obtaining high-purity cis / trans-1,2-dichloroethylene compounds has high practical scientific research and industrial application value.

[0007] Traditional separation technologies used in the modern chemical industry, such as fractional distillation, extractive distillation, and azeotropic distillation, all have drawbacks such as high energy consumption, low cost-effectiveness, and environmental unfriendliness. This is especially true when separating cis- and trans-1,2-dichloroethylene isomers with similar boiling points and molecular sizes. This may require a higher number of separation plates, which in turn requires more energy.

[0008] Currently, the separation of 1,2-dichloroethylene isomers is difficult and energy-intensive in industrial applications. Porous materials such as metal-organic frameworks (MOFs), covalent organic frameworks (COFs), and porous coordination polymers (PCs) offer a more economical solution for hydrocarbon separation.

[0009] However, their relatively low chemical / thermal stability and moisture sensitivity inevitably limit their practical applications. Moreover, there are relatively few examples of physical separations based on cis- and trans-olefin isomers, which may be due to the challenges caused by their small geometric size differences.

[0010] Therefore, there is an urgent need to design and develop new stable synthetic materials that can exhibit efficient separation performance for cis / trans-1,2-dichloroethylene isomers with subtle structural differences and similar physical properties, thereby obtaining high-purity single isomer compounds. Summary of the Invention

[0011] In view of the shortcomings in the art and the defects in the cis / trans-1,2-dichloroethylene separation technology such as high energy consumption, complicated process and environmental unfriendliness, the present invention provides a method for separating cis / trans-1,2-dichloroethylene.

[0012] The method for separating cis / trans-1,2-dichloroethylene provided by the present invention utilizes the property of hetero[4]arene crystal materials that can selectively adsorb and separate trans-1,2-dichloroethylene from a cis / trans-1,2-dichloroethylene mixture, thereby obtaining a high-purity single isomer compound.

[0013] The technical solutions of the present invention are as follows:

[0014] A method for separating cis / trans-1,2-dichloroethylene, using hetero[4]arene crystal material as an adsorbent to selectively adsorb trans-1,2-dichloroethylene and achieve separation of a cis / trans-1,2-dichloroethylene mixture;

[0015] The chemical structural formula of the hetero[4]arene crystalline material is as follows:

[0016]

[0017] The hetero[4]arene crystalline material described in the present invention is an existing material, as disclosed by Agnieszka Szumna et al. in The Journal of Organic Chemistry, Vol. 80, 2015, pp. 3488-3495.

[0018] The inventive concept of the present invention is:

[0019] In the method for separating cis / trans-1,2-dichloroethylene provided by the present invention, the hetero[4]arene crystalline material can selectively adsorb trans-1,2-dichloroethylene in the cis / trans-1,2-dichloroethylene mixture.

[0020] Due to the slight difference in the molecular structure of trans-1,2-dichloroethylene and cis-1,2-dichloroethylene, the hetero[4]arene crystalline material can form a host-guest complex with trans-1,2-dichloroethylene in a stoichiometric ratio of 2:1. In the host-guest complex, the hetero[4]arene crystalline material is the host and trans-1,2-dichloroethylene is the guest. However, the hetero[4]arene crystalline material has difficulty forming a host-guest complex with cis-1,2-dichloroethylene. Therefore, in the cis / trans-1,2-dichloroethylene separation method, the hetero[4]arene crystalline material can selectively adsorb trans-1,2-dichloroethylene in the cis / trans-1,2-dichloroethylene mixture and exhibit excellent separation performance.

[0021] Preferably, in the method for separating cis / trans-1,2-dichloroethylene, the hetero[4]arene crystalline material is obtained by activation after recrystallization in a poor solvent.

[0022] Further preferably, in the method for separating cis / trans-1,2-dichloroethylene, the poor solvent is acetonitrile or acetone. More preferably, the poor solvent is acetonitrile.

[0023] Further preferably, in the method for separating cis / trans-1,2-dichloroethylene, the activation temperature of the hetero[4]arene crystalline material is not less than 130° C., and the activation time is not less than 2 hours.

[0024] The activated hetero[4]arene crystal material can be directly used for the adsorption separation of cis / trans-1,2-dichloroethylene mixture.

[0025] Preferably, the method for separating cis / trans-1,2-dichloroethylene is specifically as follows: placing the hetero[4]arene crystalline material in a mixed vapor atmosphere of cis / trans-1,2-dichloroethylene at a temperature less than 45°C.

[0026] The adsorption time can be changed with the changes of factors such as sample amount, adsorption temperature and the proportion of trans-1,2-dichloroethylene in the mixture.

[0027] During the adsorption process, the hetero[4]arene crystalline material undergoes a change in crystalline form. Due to multiple CH-π non-covalent bond interactions, trans-1,2-dichloroethylene in the mixed vapor forms a host-guest complex with the hetero[4]arene, with a stoichiometric ratio of 2:1.

[0028] Preferably, the method for separating cis / trans-1,2-dichloroethylene further comprises removing the cis / trans-1,2-dichloroethylene mixture on the surface of the adsorbent after the adsorption separation is completed.

[0029] Further preferably, the adsorbent is heated to remove the cis / trans-1,2-dichloroethylene mixture adsorbed on the surface, and the heating temperature is less than 40°C.

[0030] In a preferred embodiment, after the hetero[4]arene crystalline material is completely adsorbed in the mixed vapor atmosphere of cis / trans-1,2-dichloroethylene, the hetero[4]arene crystalline material is taken out, and then the cis / trans-1,2-dichloroethylene mixture adsorbed on the surface of the hetero[4]arene crystalline material is removed by heating.

[0031] The heating time can be adjusted according to the sample amount. By removing the mixed vapor adsorbed on the surface, the purity of trans-1,2-dichloroethylene separated by adsorption is improved.

[0032] Preferably, the method for separating cis / trans-1,2-dichloroethylene further comprises regenerating the adsorbent after the adsorption separation is completed.

[0033] Further preferably, the regeneration method of the adsorbent is: heating the hetero[4]arene crystalline material to 100-130° C. to achieve desorption of trans-1,2-dichloroethylene.

[0034] The desorption time can be adjusted according to the sample amount.

[0035] At this temperature, the host-guest complex is unstable, and the adsorbed trans-1,2-dichloroethylene molecules are gradually released. However, the hetero[4]arene crystalline material is stable, and only undergoes a change in crystalline form during the desorption process. After desorption, the regenerated hetero[4]arene crystalline material can be used to adsorb and separate cis / trans-1,2-dichloroethylene in the next cycle without a significant decrease in selectivity.

[0036] The present invention also provides the use of hetero[4]arene crystal materials as adsorbents in the separation of cis / trans-1,2-dichloroethylene.

[0037] The invention discloses an application of hetero[4]aromatic crystalline materials as adsorbents in the separation of cis / trans-1,2-dichloroethylene. The hetero[4]aromatic crystalline materials are used as adsorbents to selectively adsorb trans-1,2-dichloroethylene to achieve the separation of cis / trans-1,2-dichloroethylene mixtures. The chemical structure of the hetero[4]aromatic crystalline materials is as follows:

[0038]

[0039] Compared with the prior art, the present invention has at least the following advantages:

[0040] 1. The separation method provided by the present invention is simple to operate and has low equipment requirements. The adsorbent hetero[4]arene crystal material used can selectively adsorb and separate trans-1,2-dichloroethylene from a cis / trans-1,2-dichloroethylene mixture and exhibits excellent separation performance with a selectivity of up to 98.8%;

[0041] 2. The separation method provided by the present invention does not require distillation operation, has low energy consumption, saves energy, and reduces production costs;

[0042] 3. The crystal material used in the separation method provided by the present invention is highly stable and can be recycled. The separation effect will not be significantly reduced after multiple recycling. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 The powder X-ray diffraction (PXRD) patterns of the crystalline materials measured in Examples 1 to 4;

[0044] Figure 2 This is a gas chromatography characterization result diagram of the adsorption separation of trans-1,2-dichloroethylene and cis-1,2-dichloroethylene by the hetero[4]arene crystalline material of Example 3;

[0045] Figure 3 This is a diagram showing the adsorption and separation effect of trans-1,2-dichloroethylene and cis-1,2-dichloroethylene when the hetero[4]arene crystal material of Example 5 is recycled. DETAILED DESCRIPTION

[0046] The present invention will be further described below in conjunction with the accompanying drawings and specific examples. It should be understood that these examples are intended to illustrate the present invention and are not intended to limit the scope of the invention. The operating methods in the following examples where no specific conditions are specified are generally performed under conventional conditions or as recommended by the manufacturer.

[0047] Example 1

[0048] Preparation of hetero[4]arene crystalline materials:

[0049] Weigh 2 g of hetero[4]arene and place it in 20 mL of acetonitrile. Heat to boiling, add acetonitrile dropwise until it is completely dissolved, store the solution at 0°C overnight, collect the precipitated crystals by filtration, dry the obtained crystals in vacuo at 50°C, and activate at 130°C for not less than 2 hours to obtain a white powder, which is recorded as H.

[0050] The product characterization data prepared in this example are as follows:

[0051] H, 1H NMR (400MHz, CDCl3, 298K) δ (ppm): 6.57 (s, 4H), 5.99 (s, 2H), 5.34 (s, 2H), 3.78 (s, 12H), 3.73 (s, 12H).

[0052] The PXRD test results are as follows Figure 1 As shown, the obtained hetero[4]arene crystalline material has good crystallinity.

[0053] Example 2

[0054] Adsorption of trans-1,2-dichloroethylene or cis-1,2-dichloroethylene by hetero[4]arene crystalline materials:

[0055] Take two 8mL culture bottles, add 0.5mL trans-1,2-dichloroethylene and 0.5mL cis-1,2-dichloroethylene respectively, and the materials after adsorption are named HE and HZ. Take 10mg of the hetero[4]arene crystalline material prepared in Example 1 and place it in two 1.5mL open culture bottles respectively. Place the two open 1.5mL culture bottles in two 8mL culture bottles respectively, seal the 8mL culture bottles, and place them at room temperature for 26 hours.

[0056] The product characterization data prepared in this example are as follows:

[0057] HE, 1 H NMR (400MHz, CDCl3, 298K) δ (ppm): 6.57 (s, 4H), 6.36 (s, 1H), 5.99 (s, 2H), 5.34 (s, 2H), 3.78 (s, 12H), 3.73 (s, 12H).

[0058] HZ, 1 H NMR (400MHz, CDCl3, 298K) δ (ppm): 6.57 (s, 4H), 5.99 (s, 2H), 5.34 (s, 2H), 3.78 (s, 12H), 3.73 (s, 12H).

[0059] 1 H NMR results showed that the hetero[4]arene crystalline material adsorbed trans-1,2-dichloroethylene in a stoichiometric ratio of 2:1, but did not adsorb cis-1,2-dichloroethylene.

[0060] The PXRD test results are as follows Figure 1As shown in the figure, compared with the PXRD spectrum of the initially activated hetero[4]arene crystal material, the PXRD spectrum of the hetero[4]arene crystal material after being placed in trans-1,2-dichloroethylene vapor for a period of time changes, which indicates that its unit cell parameters have changed, meaning that trans-1,2-dichloroethylene has been adsorbed into the hetero[4]arene crystal material; the spectrum of the hetero[4]arene crystal material after being placed in cis-1,2-dichloroethylene vapor for a period of time changes very little, indicating that its unit cell parameters have almost no change, meaning that the hetero[4]arene crystal material has no adsorption capacity for cis-1,2-dichloroethylene.

[0061] Example 3

[0062] Adsorption of a 1:1 mixture of trans-1,2-dichloroethylene and cis-1,2-dichloroethylene by hetero[4]arene crystalline materials:

[0063] Take an 8mL culture bottle, add 0.5mL trans-1,2-dichloroethylene and 0.5mL cis-1,2-dichloroethylene, and the adsorbed material is named HEZ. Take 10mg of the hetero[4]arene crystalline material prepared in Example 1 and place it in a 1.5mL open culture bottle. Place the open 1.5mL culture bottle in the above 8mL culture bottle, seal the 8mL culture bottle, and place it at room temperature for 26 hours. Dry the obtained powder in a vacuum oven at 40℃.

[0064] The product characterization data prepared in this example are as follows:

[0065] HEZ, 1 H NMR (400MHz, CDCl3, 298K) δ (ppm): 6.57 (s, 4H), 6.36 (s, 1H), 5.99 (s, 2H), 5.34 (s, 2H), 3.78 (s, 12H), 3.73 (s, 12H).

[0066] exist 1 Only the hydrogen atom signal corresponding to trans-1,2-dichloroethylene was found in the H NMR spectrum, which indicates that the hetero[4]arene crystal material can selectively adsorb trans-1,2-dichloroethylene.

[0067] The PXRD test results are as follows Figure 1 As shown, compared with the PXRD spectrum of the initially activated hetero[4]arene crystal material, the PXRD spectrum of the hetero[4]arene crystal material after being placed in the mixed vapor of trans-1,2-dichloroethylene and cis-1,2-dichloroethylene for a period of time changes, and the spectrum change is the same as that of HE, which indicates that the hetero[4]arene crystal material can selectively adsorb trans-1,2-dichloroethylene.

[0068] The results of headspace gas chromatography are as follows Figure 2 As shown, the results indicate that hetero[4]arene crystalline materials can selectively adsorb trans-1,2-dichloroethylene with a selectivity of 98.8%.

[0069] Example 4

[0070] Regeneration of hetero[4]arene crystalline materials:

[0071] 10 mg of hetero[4]arene crystalline material saturated with trans-1,2-dichloroethylene was heated in a vacuum oven at 130°C for not less than 2 hours, and the sample was recorded as HD.

[0072] The product characterization data prepared in this example are as follows:

[0073] HD, 1 H NMR (400MHz, CDCl3, 298K) δ (ppm): 6.57 (s, 4H), 5.99 (s, 2H), 5.34 (s, 2H), 3.78 (s, 12H), 3.73 (s, 12H). exist 1 It was found in the H NMR spectrum that the signal of the hydrogen atom corresponding to trans-1,2-dichloroethylene had disappeared, which indicated that the hetero[4]arene crystal material had completed desorption and regeneration, and the trans-1,2-dichloroethylene molecules had been completely released.

[0074] The PXRD test results are as follows Figure 1 As shown in FIG, compared with the PXRD spectrum of the initially activated hetero[4]arene crystal material, the PXRD spectrum of the hetero[4]arene crystal material after complete desorption has hardly changed, which indicates that the hetero[4]arene crystal material has completed the desorption process and can be used for the next adsorption separation of trans-1,2-dichloroethylene and cis-1,2-dichloroethylene.

[0075] Example 5

[0076] Recycling of hetero[4]arene crystal materials:

[0077] Examples 3 and 4 were repeated using 10 mg of the hetero[4]arene crystalline material regenerated from Example 4.

[0078] The results of headspace gas chromatography are as follows Figure 3 As shown, it is shown that hetero[4]arene crystal materials can selectively adsorb trans-1,2-dichloroethylene with a selectivity of up to 98.8%, and the selectivity does not decrease significantly after being reused 5 times.

[0079] In addition, it should be understood that after reading the above description of the present invention, those skilled in the art may make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the claims attached to this application.

Claims

1. A method for separating cis / trans-1,2-dichloroethylene, characterized in that: Using hetero[4]arene crystal material as adsorbent, trans-1,2-dichloroethylene is selectively adsorbed to achieve separation of cis / trans-1,2-dichloroethylene mixture; the chemical structure of the hetero[4]arene crystal material is as follows: The hetero[4]arene crystalline material is obtained by recrystallization in a poor solvent and then activation; The poor solvent is acetonitrile or acetone; The activation temperature of the hetero[4]arene crystalline material is not less than 130° C. and the activation time is not less than 2 hours; The separation method is specifically as follows: placing the hetero[4]arene crystalline material in a mixed vapor atmosphere of cis / trans-1,2-dichloroethylene at a temperature less than 45°C.

2. The method for separating cis / trans-1,2-dichloroethylene according to claim 1, characterized in that: The separation method further comprises removing the cis / trans-1,2-dichloroethylene mixture on the surface of the adsorbent after the adsorption separation is completed.

3. The method for separating cis / trans-1,2-dichloroethylene according to claim 2, characterized in that: The adsorbent is heated to remove the cis / trans-1,2-dichloroethylene mixture adsorbed on the surface, and the heating temperature is less than 40°C.

4. The method for separating cis / trans-1,2-dichloroethylene according to claim 1, characterized in that: The separation method further includes regenerating the adsorbent after the adsorptive separation is completed.

5. The method for separating cis / trans-1,2-dichloroethylene according to claim 4, characterized in that: The regeneration method of the adsorbent is: heating the hetero[4]arene crystalline material to 100-130°C.

6. Use of hetero[4]arene crystalline materials as adsorbents in the separation of cis / trans-1,2-dichloroethylene, characterized in that: The hetero[4]arene crystalline material is placed in a mixed vapor atmosphere of cis / trans-1,2-dichloroethylene at a temperature of less than 45° C. The hetero[4]arene crystalline material is used as an adsorbent to selectively adsorb trans-1,2-dichloroethylene to achieve separation of the cis / trans-1,2-dichloroethylene mixture. The chemical structure of the hetero[4]arene crystalline material is as follows: The hetero[4]arene crystalline material is obtained by recrystallization in a poor solvent and then activation; The poor solvent is acetonitrile or acetone; The activation temperature of the hetero[4]arene crystalline material is not less than 130° C. and the activation time is not less than 2 hours.

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