A method for capturing and separating 1,2-dibromoethane by chain length selection

Abstract

The present invention discloses a method for capturing and separating 1,2-dibromoethane by chain length selection. Using a hetero[4]arene crystal material as an adsorbent, it is contacted with a mixture containing 1,2-dibromoethane, and the mixture further contains at least one of 1,3-dibromopropane and 1,4-dibromobutane. After contacting with the mixture, the adsorbent selectively captures and adsorbs 1,2-dibromoethane to achieve the separation of 1,2-dibromoethane from the mixture; the hetero[4]arene crystal material has the structure shown in Formula I as follows: Formula I. The separation process of the present invention is simple in operation, excellent in separation performance, and has low equipment requirements; it does not require rectification operation, has low energy consumption, saves energy, and reduces production costs; the crystal material used has high thermal stability and water stability.

Description

Technical Field

[0001] The present invention relates to the technical field of adsorption separation, and particularly relates to a method for capturing and separating 1,2-dibromoethane by chain length selection. Background Art

[0002] Halogenated organic compounds have important chemical raw material value in various fields such as cooling technology, pharmaceuticals, agriculture, and plastic manufacturing. On the one hand, specific halogenated organic compounds (such as certain commonly used halogenated solvents) are closely related to biological health. Long-term inhalation, ingestion, or skin contact with these compounds can cause serious respiratory problems, liver damage, kidney problems, and even cancer in some cases. On the other hand, some halogenated organic compounds are mainly obtained in the form of mixtures by direct halogenation of hydrocarbons, so it is necessary to effectively separate them to obtain high-purity compounds.

[0003] Currently used industrial separation technologies, such as fractional distillation, extractive distillation, and azeotropic distillation, are often accompanied by process complexity and high operating costs, which are not conducive to sustainable development. Although traditional porous adsorbents based on metal-organic frameworks, covalent organic frameworks, and porous coordination polymers provide more economical and effective solutions for adsorption separation in the solid-gas phase, their relatively low chemical stability and thermal stability inevitably limit their practicality. In addition, such porous materials rely heavily on their specific pore sizes, which further restricts their application as adaptable multifunctional materials in the field of adsorption separation.

[0004] 1,2-Dibromoethane, with the chemical formula C 2 H 4 Br 2 , as a typical halogenated organic compound, is an organic chemical raw material of important value. In chemical synthesis, 1,2-dibromoethane is mainly used as an ethylating agent and a solvent, and can be used as a raw material for organic synthesis; in agriculture, it can be used to manufacture pesticides and synthesize plant growth regulators; in medicine, it is used as an intermediate for synthesizing diethyl bromobenzyl cyanide, and as a flame retardant for vinyl bromide and vinylidene dibromobenzene; in addition, it can also be used as an eliminator for lead in gasoline anti-knock fluids, a metal surface treatment agent, etc. Therefore, separating high-purity 1,2-dibromoethane has very important practical application and industrial production value.

[0005] Common homologues of 1,2-dibromoethane include 1,3-dibromopropane and 1,4-dibromobutane, etc. The difference between these homologues is mainly due to the difference caused by different chain lengths in molecular size. Generally speaking, it is very difficult to achieve the capture and selective separation of 1,2-dibromoethane in such mixtures, and it is still very challenging at present. Because of the low-polarity bonds of such compounds, it leads to a lack of effective affinity to form stable complexes with adsorption materials, thus greatly reducing the identification and separation ability of the adsorbent.

[0006] Therefore, based on the above technical problems and the deficiencies of the prior art, it is very necessary and important to develop a molecular adsorbent with strong molecular recognition ability to selectively capture halogenated organic compounds of a specific size (such as 1,2-dibromoethane) through size compatibility. Summary of the Invention

[0007] The present invention provides a method for capturing and separating 1,2-dibromoethane by chain length selection, which can solve the problems of high energy consumption, cumbersome process, environmental unfriendliness, etc. existing in the 1,2-dibromoethane separation technology.

[0008] The present invention utilizes the chain length compatibility property of hetero[4]arene crystal materials to selectively adsorb and separate 1,2-dibromoethane from a mixture of dibromoalkylidene compounds, so as to obtain a 1,2-dibromoethane compound with high purity.

[0009] The specific technical solution is as follows:

[0010] A method for capturing and separating 1,2-dibromoethane by chain length selection, using a hetero[4]arene crystal material as an adsorbent, contacting it with a mixture containing 1,2-dibromoethane, and at least one of 1,3-dibromopropane and 1,4-dibromobutane is also contained in the mixture. After the adsorbent contacts the mixture, it selectively captures and adsorbs 1,2-dibromoethane to achieve the separation of 1,2-dibromoethane from the mixture;

[0011] The hetero[4]arene crystal material has the structure shown in the following formula I:

[0012]

[0013] In one embodiment, the hetero[4]arene crystal material can be obtained through the following process: recrystallize the hetero[4]arene having the structure shown in formula I in a poor solvent, dissolve the recrystallized crystal in an inducing solvent after vacuum drying, remove the insoluble matter, and then activate it after rotary evaporation of the solvent to obtain the hetero[4]arene crystal material.

[0014] The hetero[4]arene having the structure of formula I in the present invention is an existing material, as disclosed by Agnieszka Szumna et al. in "The Journal of Organic Chemistry", Vol. 80, pp. 3488-3495, 2015.

[0015] After the hetero[4]arene having the structure of formula I obtains the hetero[4]arene crystal material through the above process, it can be better used for selectively adsorbing 1,2-dibromoethane.

[0016] Due to the difference in the alkyl chain length of the molecular structures of 1,2-dibromoethane, 1,3-dibromopropane, and 1,4-dibromobutane, the hetero[4]aromatic crystal material can form a stable host-guest complex with a stoichiometric ratio of 2:1 with 1,2-dibromoethane. In this host-guest complex, the hetero[4]aromatic crystal material is the host and 1,2-dibromoethane is the guest. However, due to the incompatibility of the compound sizes, it is difficult for the hetero[4]aromatic crystal material to form host-guest complexes with 1,3-dibromopropane and 1,4-dibromobutane. Therefore, in the method of the present invention, the hetero[4]aromatic crystal material can selectively adsorb 1,2-dibromoethane in the mixture of dibromoalkylidene compounds and exhibit excellent separation performance.

[0017] The poor solvent can be acetonitrile or acetone, preferably acetonitrile.

[0018] The temperature of the vacuum drying can be 45-55 °C.

[0019] The inducing solvent is preferably chloroform. The inducing solvent can induce and adjust the crystal form structure and size of the hetero[4]aromatic crystal material so that it can be better used for the selective adsorption and separation of 1,2-dibromoethane.

[0020] The temperature of the rotary evaporation can be 40-50 °C. The rotary evaporation can be carried out under negative pressure.

[0021] The temperature of the activation can be 110-130 °C. The activation time can be not less than 2 h.

[0022] The activated hetero[4]aromatic crystal material can be directly used for the adsorption and separation of the mixture of dibromoalkylidene compounds.

[0023] In one embodiment, the method for selectively capturing and separating 1,2-dibromoethane by chain length selection is specifically as follows: placing the adsorbent in a vapor atmosphere of a mixture containing 1,2-dibromoethane, and the adsorption temperature is less than 80 °C. The adsorption time can vary with factors such as the sample amount, adsorption temperature, and the proportion of 1,2-dibromoethane in the mixture. During the adsorption process, the crystal form of the hetero[4]aromatic crystal material will change. Due to multiple CH-π non-covalent bond interactions, 1,2-dibromoethane in the mixed vapor will form a stable host-guest complex with the hetero[4]aromatic crystal material, and the stoichiometric ratio of this host-guest complex is 2:1.

[0024] In one embodiment, the method for capturing and separating 1,2-dibromoethane by chain length selection further includes removing the mixture attached to the surface of the adsorbent after the selective capture and adsorption of 1,2-dibromoethane is completed. Specifically, the mixture attached to the surface of the adsorbent can be removed by heating the adsorbent. The temperature of the heating is preferably less than 85 °C. The heating time can be adjusted according to the sample amount. By removing the mixture adsorbed on the surface, the purity of the adsorbed and separated 1,2-dibromoethane is improved.

[0025] In one embodiment, the method for capturing and separating 1,2-dibromoethane by chain length selection further includes desorbing 1,2-dibromoethane and regenerating the adsorbent after removing the mixture attached to the surface of the adsorbent. Specifically, the desorption of 1,2-dibromoethane and the regeneration of the adsorbent can be achieved by heating the adsorbent to 120-130 °C. At this temperature, the host-guest complex is unstable, and the adsorbed 1,2-dibromoethane molecules will gradually be released, while the hetero[4]aromatic crystal material is stable and only undergoes a change in crystal form during the desorption process. After the desorption is completed, the regenerated hetero[4]aromatic crystal material can be obtained and can be used continuously for the adsorption and separation of dibromoalkylidene compound mixtures for the next cycle. The desorption time can be adjusted according to the sample amount.

[0026] The present invention also provides an application of the hetero[4]aromatic crystal material in the capture and separation of 1,2-dibromoethane by chain length selection. The hetero[4]aromatic crystal material is used as an adsorbent to contact a mixture containing 1,2-dibromoethane, and the mixture further contains at least one of 1,3-dibromopropane and 1,4-dibromobutane. The adsorbent selectively captures and adsorbs 1,2-dibromoethane after contacting with the mixture, realizing the separation of 1,2-dibromoethane from the mixture. The optional and preferred technical solutions in the above application can refer to the optional and preferred technical solutions in the method for capturing and separating 1,2-dibromoethane by chain length selection described above.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0028] 1. The separation method provided by the present invention is simple to operate and has low equipment requirements; the used adsorbent, hetero[4]aromatic crystal material, can selectively adsorb and separate 1,2-dibromoethane in the dibromoalkylidene compound mixture and exhibits excellent separation performance, with a selectivity of up to 95.4%;

[0029] 2. The separation method provided by the present invention does not require rectification operation, has low energy consumption, saves energy, and reduces production costs;

[0030] 3. The crystal material used in the separation method provided by the present invention has high thermal stability and water stability. Description of the Drawings

[0031] Figure 1 Powder X-ray diffraction (PXRD) patterns of the crystalline materials measured for Examples 1 to 4;

[0032] Figure 2 Gas chromatography characterization result diagram of the adsorption and separation of dibromoalkylidene compound mixtures by the hetero[4]arene crystalline material of Example 3. Detailed implementation manners

[0033] 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 only used to illustrate the present invention and not to limit the scope of the present invention.

[0034] Example 1

[0035] Preparation of hetero[4]arene crystalline material:

[0036] Weigh 2 g of hetero[4]arene and place it in 20 mL of acetonitrile. Heat to boiling, add acetonitrile dropwise until completely dissolved, store the solution at 0 °C overnight, filter to collect the precipitated crystals, vacuum dry the obtained crystals at 50 °C, then add them to chloroform (the dosage of chloroform is calculated as 10 mL of chloroform dissolving 50 mg of crystals) and dissolve them by ultrasonic treatment. Filter off the insoluble part, spin-dry at 45 °C to complete induction, and finally activate at 110 °C for not less than 2 hours to obtain a white powder, denoted as H.

[0037] The characterization data of the product prepared in this example are as follows:

[0038] H, 1 H NMR (400 MHz, CDCl 3 , 298 K) δ (ppm): 6.57 (s, 4H), 5.99 (s, 2H), 5.34 (s, 2H), 3.78 (s, 12H), 3.73 (s, 12H).

[0039] The PXRD test results are as Figure 1 shown, and the obtained hetero[4]arene crystalline material has good crystallinity.

[0040] Example 2

[0041] Adsorption of 1,2-dibromoethane, 1,3-dibromopropane, and 1,4-dibromobutane separately by the hetero[4]arene crystalline material:

[0042] Take three 20 mL culture flasks, and add 1 mL of 1,2-dibromoethane (DBE), 1 mL of 1,3-dibromopropane (DBP), and 1 mL of 1,4-dibromobutane (DBB) respectively. The adsorbed materials are named H-DBE, H-DBP, and H-DBB respectively. Take 10 mg of the hetero[4]arene crystal material prepared in Example 1 and place it in three 5 mL open culture flasks. Place the three 5 mL open culture flasks into the above three 20 mL culture flasks respectively, seal the 20 mL culture flasks, and place them at room temperature for 24 hours.

[0043] The characterization data of the products prepared in this example are as follows:

[0044] H-DBE, 1 H NMR (400 MHz, CDCl 3 , 298K) δ (ppm): 6.57 (s, 4H), 5.99 (s, 2H), 5.34 (s, 2H), 3.78 (s, 12H), 3.73 (s, 12H), 3.66 (s, 2H).

[0045] H-DBP, 1 H NMR (400 MHz, CDCl 3 , 298K) δ (ppm): 6.57 (s, 4H), 5.99 (s, 2H), 5.34 (s, 2H), 3.78 (s, 12H), 3.73 (s, 12H).

[0046] H-DBB, 1 H NMR (400 MHz, CDCl 3 , 298K) δ (ppm): 6.57 (s, 4H), 5.99 (s, 2H), 5.34 (s, 2H), 3.78 (s, 12H), 3.73 (s, 12H).

[0047] 1 The H NMR results show that the hetero[4]arene crystal material adsorbed 1,2-dibromoethane in a stoichiometric ratio of 2:1, and did not adsorb 1,3-dibromopropane and 1,4-dibromobutane.

[0048] The PXRD test results are as Figure 1As shown, compared with the PXRD pattern of the initially activated hetero[4]aromatic crystal material, the PXRD pattern of the hetero[4]aromatic crystal material after being placed in 1,2-dibromoethane vapor for a period of time shows obvious changes, indicating that its unit cell parameters have changed, meaning that 1,2-dibromoethane has been adsorbed into the hetero[4]aromatic crystal material; the patterns of the hetero[4]aromatic crystal material after being placed in 1,3-dibromopropane and 1,4-dibromobutane vapors for a period of time have not changed significantly, indicating that its unit cell parameters have hardly changed, meaning that the hetero[4]aromatic crystal material has little adsorption capacity for 1,3-dibromopropane and 1,4-dibromobutane.

[0049] Example 3

[0050] Adsorption of a 1:1:1 mixture of 1,2-dibromoethane, 1,3-dibromopropane and 1,4-dibromobutane by the hetero[4]aromatic crystal material:

[0051] Take a 20 mL culture flask, add 0.5 mL of 1,2-dibromoethane, 0.5 mL of 1,3-dibromopropane and 0.5 mL of 1,4-dibromobutane. Take 10 mg of the hetero[4]aromatic crystal material prepared in Example 1 and place it in a 5 mL open culture flask. Place the open 5 mL culture flask in the above 20 mL culture flask, seal the 20 mL culture flask, place it at room temperature for 24 hours, dry the obtained powder in an 80 °C oven, and denote the obtained product as H-MIX.

[0052] The characterization data of the product prepared in this example are as follows:

[0053] H-MIX, 1 H NMR (400 MHz, CDCl 3 , 298 K) δ (ppm): 6.57 (s, 4H), 5.99 (s, 2H), 5.34 (s, 2H), 3.78 (s, 12H), 3.73 (s, 12H), 3.66 (s, 2H).

[0054] In 1 the H NMR spectrum, only the signals of the hydrogen atoms corresponding to 1,2-dibromoethane and extremely low contents of 1,3-dibromopropane and 1,4-dibromobutane were found, indicating that the hetero[4]aromatic crystal material can selectively adsorb 1,2-dibromoethane.

[0055] The PXRD test results are as Figure 1As shown, relative to the PXRD pattern of the initially activated hetero[4]aromatic crystal material, the PXRD pattern of the hetero[4]aromatic crystal material after being placed in the mixed vapor of 1,2-dibromoethane, 1,3-dibromopropane, and 1,4-dibromobutane for a period of time changes, and the pattern change is almost the same as that of H-DBE, indicating that the hetero[4]aromatic crystal material can selectively adsorb 1,2-dibromoethane.

[0056] The results of headspace gas chromatography are as Figure 2 shown, and the results indicate that the hetero[4]aromatic crystal material can selectively adsorb 1,2-dibromoethane with a selectivity of 95.4%.

[0057] Example 4

[0058] Regeneration of hetero[4]aromatic crystal material:

[0059] 10 mg of H-MIX from Example 3 was heated in a vacuum oven at 130 °C for not less than 2 hours, and the resulting sample was denoted as H-D.

[0060] The product characterization data prepared in this example are as follows:

[0061] H-D, 1 H NMR (400 MHz, CDCl 3 , 298 K) δ (ppm): 6.57 (s, 4H), 5.99 (s, 2H), 5.34 (s, 2H), 3.78 (s, 12H), 3.73 (s, 12H). In 1 the H NMR spectrum, the signal of the hydrogen atoms corresponding to 1,2-dibromoethane has disappeared, indicating that the hetero[4]aromatic crystal material has completed desorption regeneration and all 1,2-dibromoethane molecules have been released.

[0062] The PXRD test results are as Figure 1 shown. Relative to the PXRD pattern of the initially activated hetero[4]aromatic crystal material, the PXRD pattern of the hetero[4]aromatic crystal material after complete desorption has hardly changed, indicating that the hetero[4]aromatic crystal material has completed the desorption process and can be used for the next adsorption and separation of dibromoalkylidene compound mixtures.

[0063] In addition, it should be understood that after reading the above description of the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of this application.

Claims

1. A method for capturing and separating 1,2 - dibromoethane by chain length selection, characterized in that, using a hetero[4]aromatic crystal material as an adsorbent, contacting it with a mixture containing 1,2 - dibromoethane, wherein the mixture further contains at least one of 1,3 - dibromopropane and 1,4 - dibromobutane, and the adsorbent selectively captures and adsorbs 1,2 - dibromoethane after contacting with the mixture, realizing the separation of 1,2 - dibromoethane from the mixture; the hetero[4]aromatic crystal material has the structure shown in Formula I as follows: The hetero[4]aromatic crystal material is obtained through the following process: recrystallizing the hetero[4]aromatic having the structure shown in Formula I in a poor solvent, dissolving the recrystallized crystal in an inducing solvent after vacuum drying, removing insoluble substances, and then activating it after rotary evaporation of the solvent to dryness; the inducing solvent is chloroform; the activation temperature is 110 - 130 °C; the activation time is not less than 2 h; The method for capturing and separating 1,2 - dibromoethane by chain length selection is specifically: placing the adsorbent in a vapor atmosphere of a mixture containing 1,2 - dibromoethane, and the adsorption temperature is less than 80 °C.

2. The method according to claim 1, characterized in that, the poor solvent is acetonitrile or acetone; the temperature of the vacuum drying is 45 - 55 °C; the temperature of the rotary evaporation is 40 - 50 °C; the rotary evaporation is carried out under negative pressure.

3. The method according to claim 1, characterized in that, the method for capturing and separating 1,2 - dibromoethane by chain length selection further includes removing the mixture adhering to the surface of the adsorbent after completing the selective capture and adsorption of 1,2 - dibromoethane.

4. The method according to claim 3, characterized in that, heating the adsorbent to remove the mixture adhering to the surface of the adsorbent, and the heating temperature is less than 85 °C.

5. The method according to claim 3 or 4, characterized in that, the method for capturing and separating 1,2 - dibromoethane by chain length selection further includes desorbing 1,2 - dibromoethane and regenerating the adsorbent after completing the removal of the mixture adhering to the surface of the adsorbent.

6. The method according to claim 5, characterized in that, desorbing 1,2 - dibromoethane and regenerating the adsorbent by heating the adsorbent to 120 - 130 °C.

7. Use of the hetero[4]aromatic crystal material in capturing and separating 1,2 - dibromoethane by chain length selection, characterized in that, the hetero[4]aromatic crystal material is used as an adsorbent to contact with a mixture containing 1,2 - dibromoethane, wherein the mixture further contains at least one of 1,3 - dibromopropane and 1,4 - dibromobutane, and the adsorbent selectively captures and adsorbs 1,2 - dibromoethane after contacting with the mixture, realizing the separation of 1,2 - dibromoethane from the mixture; the hetero[4]aromatic crystal material has the structure shown in Formula I as follows:

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