A process for the separation of o-ethyltoluene and m-ethyltoluene

Abstract

This invention discloses a method for separating o-toluene and m-toluene, using a bis(dibromoethoxy) column[6] aromatic crystalline material as an adsorbent. A mixture containing o-toluene and m-toluene is contacted with the adsorbent for adsorption, thereby achieving the separation of o-toluene and m-toluene. The chemical structural formula of the bis(dibromoethoxy) column[6] aromatic crystalline material is as follows: This invention also discloses the application of the bis(dibromoethoxy) column[6] aromatic crystalline material in selectively adsorbing and complexing o-toluene in a mixture containing o-toluene and m-toluene to achieve the separation of o-toluene and m-toluene. The separation process of this invention is simple to operate and requires low-level equipment; the separation process does not require distillation, resulting in low energy consumption, energy saving, and reduced production costs of o-toluene; the crystalline material used has high stability, can be recycled, and the separation effect will not decrease.

Description

Technical Field

[0001] This invention relates to the field of adsorption separation technology, specifically to a method for separating o-toluene and m-toluene. Background Technology

[0002] The petroleum catalytic reforming process generates a large number of byproducts, such as C9 and C8 aromatics. C9 aromatics are mainly composed of aromatic compounds containing nine carbon atoms, such as o-toluene and m-toluene.

[0003] o-Ethylbenzene is an important chemical raw material. Dehydrogenation can produce methylstyrene, which can then be polymerized to obtain novel polymer materials with wide applications in engineering plastics, flame-retardant specialty resins, and reinforced polyester fibers. Because many of the physical properties of this new material are significantly superior to polystyrene, it has great development and application value in industry. However, o- and m-ethylbenzene need to be extracted from the mixture before industrial production. Therefore, obtaining high-purity o-ethylbenzene from methylbenzene mixtures is of great significance for reducing o-ethylbenzene production costs and improving the utilization rate of petroleum waste.

[0004] The separation of o-ethylbenzene and m-ethylbenzene is an extremely challenging step. This is because the boiling points of o-ethylbenzene (164℃) and m-ethylbenzene (159℃) differ by only 5℃, and they form an azeotrope, making them difficult to separate using traditional distillation processes. Existing technologies have reported the separation of o-ethylbenzene using distillation (e.g., "Separation and Utilization of Ethylbenzene from Reformed C9 Aromatics," *Chemical Industry Times*, 2001, No. 2, pp. 25-26), but distillation methods often involve significant energy consumption, are costly, and rarely yield high-purity o-ethylbenzene. Furthermore, leveraging the differences in molecular size and geometry between o-ethylbenzene and m-ethylbenzene, molecular sieves can achieve separation through adsorption. However, this process requires high-purity desorbents, which can easily cause environmental pollution.

[0005] Therefore, there is an urgent need to develop new, stable, and recyclable adsorbent materials to effectively separate o-toluene and m-toluene.

[0006] In the inventors' prior research, patent specification CN111517911A disclosed a method for separating a mixture of m-toluene and p-toluene by selectively adsorbing p-toluene using a bis(ethoxy) column[6] aromatic crystalline material. However, the inventors found that the aforementioned bis(ethoxy) column[6] aromatic crystalline material did not achieve good separation results when dealing with a separation system of ortho-toluene and m-toluene. Summary of the Invention

[0007] In view of the above-mentioned technical problems and the shortcomings in the field, the present invention provides a method for separating o-toluene and m-toluene, which uses bis(dibromoethoxy) column[6] aromatic crystal material to adsorb and separate a mixture containing m-toluene and o-toluene. The method has low energy consumption and simple process, and overcomes the defects of high energy consumption and complicated process in the separation technology of o-toluene and m-toluene.

[0008] The specific technical solution is as follows:

[0009] A method for separating o-toluene and m-toluene uses bis(dibromoethoxy) column[6] aromatic crystal material as adsorbent, and contacts the mixture containing o-toluene and m-toluene with the adsorbent to achieve separation of o-toluene and m-toluene;

[0010] The chemical structural formula of the bis(dibromoethoxy) columnar[6] aromatic crystalline material is as follows:

[0011]

[0012] This invention has found that, due to the difference in molecular structure between o-toluene and m-toluene, the bis(dibromoethoxy)-column[6]arene crystal material can form a host-guest complex with o-toluene in a stoichiometric ratio of 1:2. This host-guest complex gradually de-complexes upon heating, releasing the adsorbed o-toluene. The bis(dibromoethoxy)-column[6]arene crystal material is chemically stable at the desorption temperature, can be reused, and its selectivity does not decrease.

[0013] Dibromoethoxy[6] aromatics can be prepared using existing techniques, such as the patent specification with publication number CN110372580A.

[0014] Preferably, the bis(dibromoethoxy)[6] aromatic crystal material is first recrystallized in a poor solvent and then activated before use. Commonly used poor solvents are tetrahydrofuran or acetone, but are not limited to these. The recrystallized bis(dibromoethoxy)[6] aromatic crystal material can be activated by removing solvent molecules through heating. The activation temperature is preferably 130-150°C, and the activation time is preferably not less than 2 hours. The activated bis(dibromoethoxy)[6] aromatic crystal material can be directly used for the adsorption and separation of mixtures containing o-toluene and m-toluene.

[0015] Preferably, the temperature of the contact adsorption is less than 50°C.

[0016] In a preferred embodiment, the separation method specifically involves placing the bis(dibromoethoxy) column[6] aromatic crystal material in a mixed vapor atmosphere containing o-toluene and m-toluene, and performing adsorption separation at a temperature below 50°C. During the adsorption process, the bis(dibromoethoxy) column[6] aromatic crystal material forms a host-guest complex with o-toluene in the mixed vapor, and the stoichiometric ratio of the host-guest complex is 1:2.

[0017] Preferably, the separation method further includes removing the mixture containing o-toluene and m-toluene adsorbed on the surface of the bis(dibromoethoxy) column[6] aromatic crystal material by vacuum heating or reduced pressure heating. More preferably, the temperature of the vacuum heating or reduced pressure heating is less than 60°C.

[0018] After contact adsorption is complete, the bis(dibromoethoxy) column[6] aromatic crystal material is vacuum heated or reduced pressure heated to no more than 60°C to remove the mixture containing o-toluene and m-toluene adsorbed on the surface. The host-guest complex remains stable at temperatures below 60°C, while the mixture containing o-toluene and m-toluene adsorbed on the surface can be removed.

[0019] Preferably, the separation method further includes heating to desorb the adsorbed and complexed o-ethylbenzene from the bis(dibromoethoxy) column[6) aromatic crystal material containing the mixture of o-ethylbenzene and m-ethylbenzene that has been removed from its surface, thereby obtaining high-purity o-ethylbenzene while simultaneously regenerating and activating the bis(dibromoethoxy) column[6] aromatic crystal material. The adsorbed and complexed o-ethylbenzene molecules in the bis(dibromoethoxy) column[6] aromatic crystal material can be desorbed by heating, preferably at a temperature of 130-150°C, and the desorption time can be adjusted according to the sample amount. At this temperature, the host-guest complex is unstable, and the adsorbed o-ethylbenzene molecules will be gradually released, while the bis(dibromoethoxy) column[6] aromatic crystal material is stable, and only a change in crystal form occurs during the desorption process. After desorption, the regenerated bis(dibromoethoxy) column[6] aromatic crystal material is obtained, which can be used again to adsorb and separate the mixture of o-ethylbenzene and m-ethylbenzene for the next cycle. In a preferred embodiment, the temperature for the heating desorption is 130-150°C, and the time is not less than 2 hours.

[0020] As a general inventive concept, this invention also provides an application of the bis(dibromoethoxy) column[6] aromatic crystalline material in selectively adsorbing and complexing o-ethylbenzene in a mixture containing o-ethylbenzene and m-ethylbenzene to achieve the separation of o-ethylbenzene and m-ethylbenzene. The preferred technical solutions and features in the application can be referred to the separation method described above.

[0021] Compared with the prior art, the present invention has the following advantages: the separation process is simple to operate and has low equipment requirements; the separation process does not require distillation, resulting in low energy consumption, energy saving, and reduced production costs of o-toluene; the crystal material used has high stability, can be recycled, and the separation effect will not be reduced. Attached Figure Description

[0022] Figure 1 The gas chromatographic characterization results of the adsorption and separation of o-toluene and m-toluene by the bis(dipropoxy) column[6] aromatic crystalline material are shown in the figure. The horizontal axis represents the retention time in min and the vertical axis represents the detector signal current intensity in pA.

[0023] Figure 2 The powder X-ray diffraction (PXRD) patterns of the bis(dibromoethoxy) columnar aromatic crystal materials of Examples 5-9 [6] are shown.

[0024] Figure 3 The gas chromatographic characterization results of the adsorption and separation of o-toluene and m-toluene by the bis(dibromoethoxy) column[6] aromatic crystalline material are shown in the figure. The horizontal axis represents the retention time in min and the vertical axis represents the detector signal current intensity in pA.

[0025] Figure 4 The image shows the adsorption separation effect of the bis(dibromoethoxy) column[6] aromatic crystal material used in Example 5 for separating o-toluene and m-toluene through a cyclic adsorption-regeneration process. Detailed Implementation

[0026] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Operating methods not specifically specified in the following embodiments are generally performed under conventional conditions or as recommended by the manufacturer.

[0027] Example 1

[0028] Preparation of bis(diethoxy)[6]arene crystal material: Weigh 1g of bis(diethoxy)[6]arene and place it in 10mL of acetone. Heat to boiling and add acetone dropwise until completely dissolved. Store the solution at 0℃ overnight. Filter and collect the precipitated crystals. Dry the obtained crystals under vacuum at 50℃ and activate at 150℃ for 2 hours to obtain a white powder, denoted as EtP6.

[0029] The characterization data of the product prepared in this embodiment are as follows:

[0030] EtP6, 1 H NMR (400MHz, CDCl3, 298K, ppm) δ6.69 (s, 12H), 3.81 (t, 24H), 3.79 (s, 12H), 1.28 (t, 36H).

[0031] Example 2

[0032] Adsorption of a 1:1 mixture of o-toluene and m-toluene by bis(ethoxy) column[6] aromatic crystalline material: Take a 20 mL culture bottle, add 0.50 mL of o-toluene and 0.50 mL of m-toluene, named EtP6-OMET, take 20 mg of the bis(ethoxy) column[6] aromatic crystalline material from Example 1 and place it in a 5 mL culture bottle, place the open 5 mL culture bottle in the above 20 mL culture bottle, seal the 20 mL culture bottle, place it in a 25 °C water bath for 40 hours, and place the obtained powder in a 50 °C vacuum oven for 30 minutes.

[0033] The characterization data of the product prepared in this embodiment are as follows:

[0034] EtP6-OMET, 1 H NMR (400MHz, CDCl3, 298K, ppm) δ6.69 (s, 12H), 3.81 (t, 24H), 3.79 (s, 12H), 1.28 (t, 36H).

[0035] exist 1 No signals of hydrogen atoms corresponding to o-ethylbenzene and m-ethylbenzene were found in the H NMR spectrum, which indicates that the bis(ethoxy) column[6] aromatic crystal material cannot selectively adsorb o-ethylbenzene and m-ethylbenzene.

[0036] Example 3

[0037] Preparation of bis(dipropoxy)[6]arene crystal material: Weigh 1g of bis(dipropoxy)[6]arene and place it in 10mL of acetone. Heat to boiling and add acetone dropwise until completely dissolved. Store the solution at 0℃ overnight. Filter and collect the precipitated crystals. Dry the obtained crystals under vacuum at 50℃ and activate at 130℃ for 2 hours to obtain a white powder, denoted as PrP6.

[0038] The characterization data of the product prepared in this embodiment are as follows:

[0039] PrP6, 1 H NMR (400MHz, CDCl3, 298K, ppm) δ6.69 (s, 12H), 3.80 (s, 12H), 3.70 (t, 24H), 1.69 (q, 24H), 0.93 (t, 36H).

[0040] Example 4

[0041] Adsorption of a 1:1 mixture of o-toluene and m-toluene by bis(dipropoxy)[6] aromatic crystalline material: Take a 20mL culture bottle, add 0.50mL of o-toluene and 0.50mL of m-toluene, named PrP6-OMET, take 20mg of the bis(dipropoxy)[6] aromatic crystalline material from Example 3 and place it in a 5mL culture bottle, place the open 5mL culture bottle in the above 20mL culture bottle, seal the 20mL culture bottle, place it in a 25℃ water bath for 40 hours, and place the obtained powder in a 50℃ vacuum oven for 30 minutes.

[0042] The adsorption separation effect of the product prepared in this embodiment was verified by headspace gas chromatography. The results showed that, as Figure 1 The dipropoxy column[6] aromatic crystal material can selectively adsorb o-ethylbenzene, but the purity of o-ethylbenzene adsorbed in the dipropoxy column[6] aromatic crystal material is only 75.46%, which cannot be used as the adsorption and separation subject of o-ethylbenzene and m-ethylbenzene.

[0043] Example 5

[0044] Preparation of bis(dibromoethoxy)[6]arene crystal material: Weigh 1g of bis(dibromoethoxy)[6]arene and place it in 10mL of acetone. Heat to boiling and add acetone dropwise until completely dissolved. Store the solution at 0℃ overnight. Filter and collect the precipitated crystals. Dry the obtained crystals under vacuum at 50℃ and activate at 150℃ for 2 hours to obtain a white powder, denoted as BrP6.

[0045] The characterization data of the product prepared in this embodiment are as follows:

[0046] BrP6, 1 H NMR (400MHz, CDCl3, 298K, ppm) δ6.78 (s, 12H), 4.16 (t, 24H), 3.87 (s, 12H), 3.55 (t, 24H).

[0047] PXRD test results are as follows Figure 2 As shown by line a, the obtained bis(dibromoethoxy) columnar aromatic crystalline material [6] has good crystallinity.

[0048] Example 6

[0049] Adsorption of o- or m-ethylbenzene by bis(dibromoethoxy) column[6] aromatic crystal material: Take two 20mL culture bottles and add 1mL of o- or m-ethylbenzene to each, naming them BrP6-OET and BrP6-MET respectively. Take 50mg of the activated bis(dibromoethoxy) column[6] aromatic crystal material from Example 5 and place it in two 5mL culture bottles respectively. Place the two open 5mL culture bottles in two 20mL culture bottles, seal the 20mL culture bottles, and place them in a 25℃ water bath for 30 hours.

[0050] The characterization data of the product prepared in this embodiment are as follows:

[0051] BrP6-OET, 1 H NMR (400MHz, CDCl3, 298K, ppm) δ7.15 (m, 6H), 7.10 (m, 2H) 6.78 (s, 12H), 4.16 (t,24H),3.87(s,12H),3.55(t,24H),2.62(q,4H),2.31(s,6H),1.21(t,6H).

[0052] BrP6-MET, 1 H NMR (400MHz, CDCl3, 298K, ppm) δ7.17 (s, 0.78H), 7.00 (m, 2.39H), 6.78 (s, 12H), 4.16 ( t, 24H), 3.87 (s, 12H), 3.55 (t, 24H), 2.62 (m, 1.56H), 2.33 (s, 2.34H), 1.23 (t, 2.34H).

[0053] 1 1H NMR results showed that the bis(dibromoethoxy) column[6] aromatic crystal material adsorbed o-ethylbenzene in a stoichiometric ratio of 1:2 and m-ethylbenzene in a stoichiometric ratio of 1:0.78. That is, the adsorption capacity of the bis(dibromoethoxy) column[6] aromatic crystal material for o-ethylbenzene was significantly stronger than that for m-ethylbenzene.

[0054] PXRD test results are as follows Figure 2 As shown by line c, compared to the PXRD spectrum of the initially activated bis(dibromoethoxy)[6]arene crystal material, the PXRD spectrum of the bis(dibromoethoxy)[6]arene crystal material placed in an o-toluene vapor atmosphere for a period of time shows a huge change. This indicates that its cell parameters have changed, meaning that o-toluene has been adsorbed into the bis(dibromoethoxy)[6]arene crystal material; Figure 2As shown by line b, compared with the original PXRD spectrum of the bis(dibromoethoxy) columnar[6] aromatic crystal material, the PXRD spectrum of the bis(dibromoethoxy) columnar[6] aromatic crystal material placed in the atmosphere of m-toluene vapor for a period of time has changed to a certain extent, indicating that its cell parameters have also changed, which means that the bis(dibromoethoxy) columnar[6] aromatic crystal material has a certain adsorption capacity for m-toluene.

[0055] Example 7

[0056] Adsorption of a 1:1 mixture of o-toluene and m-toluene by bis(dibromoethoxy)[6] aromatic crystal material: Take a 20mL culture bottle, add 0.50mL of o-toluene and 0.50mL of m-toluene, named BrP6-OMET, take 20mg of the bis(dibromoethoxy)[6] aromatic crystal material from Example 5 and place it in a 5mL culture bottle, place the open 5mL culture bottle in the above 20mL culture bottle, seal the 20mL culture bottle, place it in a 25℃ water bath for 40 hours, and place the obtained powder in a 50℃ vacuum oven for 30 minutes.

[0057] The characterization data of the product prepared in this embodiment are as follows:

[0058] BrP6-OMET, 1 H NMR (400MHz, CDCl3, 298K, ppm) δ7.14 (m, 6H) 7.10 (m, 2H) 6.78 (s, 12H), 4.16 ( t,24H),3.87(s,12H),3.55(t,24H),2.62(d,4H),2.31(s,6H),1.12(t,6H).

[0059] exist 1 The H NMR spectrum only showed the signal of the hydrogen atom corresponding to o-ethylbenzene, which indicates that in the mixed system of o-ethylbenzene and m-ethylbenzene, the bis(dibromoethoxy) column[6] aromatic crystal material can selectively adsorb o-ethylbenzene.

[0060] PXRD test results are as follows Figure 2 As shown by the middle d-line, the PXRD spectrum of the bis(dibromoethoxy) column[6] aromatic crystal material changed after being placed in a mixed vapor of o-toluene and m-toluene for a period of time, compared to the PXRD spectrum of the initially activated bis(dibromoethoxy) column[6] aromatic crystal material. The spectrum change was the same as that of BrP6-OET, which indicates that the bis(dibromoethoxy) column[6] aromatic crystal material can selectively adsorb o-toluene.

[0061] The results of headspace gas chromatography are as follows Figure 3The results showed that the bis(dibromoethoxy) column[6] aromatic crystal material could selectively adsorb o-ethylbenzene, and the purity of o-ethylbenzene adsorbed in the bis(dibromoethoxy) column[6] aromatic crystal material was 94.00%.

[0062] Example 8

[0063] Regeneration of bis(dibromoethoxy) column[6] aromatic crystal material: 200 mg of BrP6-OMET from Example 7 was heated in a vacuum oven at 130-150°C for 2 hours and recorded as BrP6-D.

[0064] The characterization data of the product prepared in this embodiment are as follows:

[0065] BrP6-D, 1 H NMR (400MHz, CDCl3, 298K, ppm) δ6.78(s,12H), 4.16(t,24H), 3.87(s,12H), 3.55(t,24H).

[0066] exist 1 The H NMR spectrum showed that the signal of the hydrogen atom corresponding to o-toluene had disappeared, which indicates that the bis(dibromoethoxy) column[6] aromatic crystal material has completed desorption and regeneration, and all o-toluene molecules have been released.

[0067] PXRD test results are as follows Figure 2 As shown by line e, the PXRD spectrum of the desorbed bis(dibromoethoxy)[6]arene crystal material did not change compared to the PXRD spectrum of the initially activated bis(dibromoethoxy)[6]arene crystal material. This indicates that the cell parameters of the desorbed bis(dibromoethoxy)[6]arene crystal material have been restored to the initially activated state, and the desorption process of the bis(dibromoethoxy)[6]arene crystal material has been completed.

[0068] Example 9

[0069] Reuse of bis(dibromoethoxy) column[6) aromatic crystal material: 50 mg of the bis(dibromoethoxy) column[6] aromatic crystal material regenerated in Example 8 was repeated in Examples 7 and 8.

[0070] Headspace gas chromatography results show that, Figure 4 The bis(dibromoethoxy) column[6) aromatic crystal material can selectively adsorb o-ethylbenzene. The purity of o-ethylbenzene adsorbed in the bis(dibromoethoxy) column[6) aromatic crystal material can reach 94.00%, and its adsorption selectivity does not decrease after being reused 5 times. The PXRD test results of the reused and regenerated bis(dibromoethoxy) column[6) aromatic crystal material are shown as line f in 2, which are consistent with the newly prepared bis(dibromoethoxy) column[6] crystal material, which fully demonstrates the excellent structural stability of the bis(dibromoethoxy) column[6] crystal material.

[0071] Furthermore, it should be understood that after reading the above description of the present invention, those skilled in the art can make various alterations or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims.

Claims

1. A method for separating o-toluene and m-toluene, characterized in that, Using bis(dibromoethoxy) column[6] aromatic crystal material as adsorbent, a mixture containing o-toluene and m-toluene in a volume ratio of 1:1 is contacted with the adsorbent for adsorption, thereby achieving the separation of o-toluene and m-toluene; The chemical structural formula of the bis(dibromoethoxy) columnar[6] aromatic crystalline material is as follows: ； The bis(dibromoethoxy) columnar[6] aromatic crystal material is first recrystallized in a poor solvent and then activated before use; The specific operation of the separation method is as follows: the bis(dibromoethoxy) column[6] aromatic crystal material is placed in a mixed vapor atmosphere containing o-toluene and m-toluene, and adsorption separation is carried out at a temperature of less than 50°C. The separation method further includes removing the mixture containing o-toluene and m-toluene adsorbed on the surface of the bis(dibromoethoxy) column[6] aromatic crystal material by vacuum heating or reduced pressure heating; the temperature of the vacuum heating or reduced pressure heating is less than 60°C; The separation method further includes heating to desorb the adsorbed and complexed o-ethylbenzene from the bis(dibromoethoxy) column[6] aromatic crystal material containing a mixture of o-ethylbenzene and m-ethylbenzene that has been removed from the surface, thereby obtaining high-purity o-ethylbenzene and simultaneously regenerating and activating the bis(dibromoethoxy) column[6] aromatic crystal material; the heating desorption temperature is 130-150℃ and the time is not less than 2 hours.

2. The separation method according to claim 1, characterized in that, The unsuitable solvent is tetrahydrofuran or acetone.

3. The separation method according to claim 1, characterized in that, The activation temperature is 130-150℃, and the time is not less than 2 hours.

4. The application of bis(dibromoethoxy) column[6] aromatic crystalline material in selectively adsorbing and complexing o-toluene into a mixture containing o-toluene and m-toluene to achieve the separation of o-toluene and m-toluene, characterized in that, Using bis(dibromoethoxy) column[6] aromatic crystal material as adsorbent, a mixture containing o-toluene and m-toluene in a volume ratio of 1:1 is contacted with the adsorbent for adsorption, thereby achieving the separation of o-toluene and m-toluene; The chemical structural formula of the bis(dibromoethoxy) columnar[6] aromatic crystalline material is as follows: ； The bis(dibromoethoxy) columnar[6] aromatic crystal material is first recrystallized in a poor solvent and then activated before use; The specific operation of the application is as follows: the bis(dibromoethoxy) column[6] aromatic crystal material is placed in a mixed vapor atmosphere containing o-toluene and m-toluene, and adsorption separation is carried out at a temperature of less than 50°C. The application also includes removing the mixture containing o-toluene and m-toluene adsorbed on the surface of the bis(dibromoethoxy) columnar aromatic crystal material by vacuum heating or reduced pressure heating; the temperature of the vacuum heating or reduced pressure heating is less than 60°C; The application also includes heating to desorb the adsorbed and complexed o-ethylbenzene from the bis(dibromoethoxy) column[6] aromatic crystal material containing a mixture of o-ethylbenzene and m-ethylbenzene that has been removed from the surface, thereby obtaining high-purity o-ethylbenzene and simultaneously regenerating and activating the bis(dibromoethoxy) column[6] aromatic crystal material; the heating desorption temperature is 130-150℃ and the time is not less than 2 hours.

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