Method for efficiently separating aromatic hydrocarbon from cycloalkane

Abstract

The invention discloses a method for efficiently separating aromatic hydrocarbon in cycloalkane. The aromatic hydrocarbon in the cycloalkane is adsorbed and separated by adopting a bipyridine monocation salt crystal material; the chemical structure of the bipyridine monocation salt crystal material is shown as a formula T1, a formula OH-T3, a formula Me-SA3, a formula Et-SA3 or a formula SA6. The specific crystal material is used for selectively adsorbing the aromatic hydrocarbon in the cycloalkane, the adsorption process is simple in technology, high in selectivity, good in adsorption effect, free of complex equipment, low in cost and suitable for large-scale industrial production.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of separation and purification technology, and in particular to a method for efficiently separating aromatic hydrocarbons from naphthenes with low energy consumption and simple process. BACKGROUND

[0002] Cyclohexane is an important chemical raw material and solvent, which can be used as a raw material for the preparation of nylon 66 from caprolactam and adipic acid. Methylcyclohexane is widely used in food soft packaging printing ink and environmentally friendly correction fluid, adhesive, cleaning agent production. In the chemical industry, cyclohexane and methylcyclohexane are obtained by catalytic hydrogenation of benzene and toluene, respectively. There are often residual raw materials in the crude product of the hydrogenation of the two. It is essential to remove the unreacted benzene / toluene from the effluent of the reactor for high purity cyclohexane / methylcyclohexane. However, due to the similar physical properties of benzene / cyclohexane and toluene / methylcyclohexane, it is extremely difficult to separate trace amounts of aromatic hydrocarbons from naphthenes. Currently, the industrial method for obtaining high purity naphthenes is to use multi-stage reactors to extend the reaction time to ensure high conversion rate of aromatic hydrocarbons to naphthenes (-99%), and then use multi-stage separators to further purify naphthenes. However, the above method requires high energy, and the separation process is complex and has high operating costs. Therefore, it is necessary to develop an easy-to-operate and more energy-efficient method to remove trace amounts of aromatic hydrocarbons from naphthenes. SUMMARY

[0003] The present application provides a method for efficiently separating aromatic hydrocarbons from naphthenes to solve the technical problems of high energy consumption, complex process and high cost of the existing naphthenes purification method mentioned in the background.

[0004] To solve the above technical problems, the technical solution provided by the present application is as follows: A method for efficiently separating aromatic hydrocarbons from naphthenes, which uses a bipyridine monocation salt crystal material to adsorb and separate aromatic hydrocarbons from naphthenes. The chemical structure of the bipyridine monocation salt crystal material is shown in formula T1, formula OH-T3, formula Me-SA, formula Et-SA3 or formula SA6: .

[0005] The above crystal material can form a host-guest complex with benzene / toluene due to multiple non-covalent interactions during the adsorption process, thereby selectively adsorbing benzene / toluene from naphthenes. The self-adapting flexible skeleton and unique three-dimensional structure in its structure can avoid the influence of its own aromatic group on the electron-deficient skeleton. The process is simple, the energy consumption is low, and no complex equipment is needed. The separation and purification effect is good, and the cost is low. At the same time, the above crystal material has high stability at low temperature, and can be desorbed at low temperature. After the desorption process is completed, it can be reused, and the selectivity will not decrease.

[0006] As a further preferred embodiment of the above technical solution, the method for efficiently separating aromatic hydrocarbons from naphthenes comprises the following operations: vaporizing the naphthenes containing aromatic hydrocarbons to form a mixed vapor, placing the dipyridyl monocation salt crystal material in the mixed vapor, and performing adsorption at 80°C; after the adsorption is completed, the aromatic hydrocarbons are fixed in the dipyridyl monocation salt crystal material. The adsorption time can be controlled to be 24h.

[0007] As a further preferred embodiment of the above technical solution, after the adsorption is completed, the dipyridyl monocation salt crystal material is soaked in dichloromethane for more than 6h, the solid is collected by filtration, the solid is ground into powder, and vacuum drying is performed at 80-120°C for more than 8h, so that the regeneration of the dipyridyl monocation salt crystal material is completed.

[0008] As a further preferred embodiment of the above technical solution, the method for efficiently separating aromatic hydrocarbons from naphthenes comprises the following operations: mixing and grinding the dipyridyl monocation salt crystal material with chromatographic silica gel to obtain a chromatographic material, filling the chromatographic material into a chromatographic device, pouring a mixed liquid containing aromatic hydrocarbons into the chromatographic device to perform chromatography, and collecting the filtrate at the bottom of the chromatographic device to obtain purified naphthenes.

[0009] As a further preferred embodiment of the above technical solution, after the chromatography is completed, the chromatographic material is soaked in dichloromethane for more than 6h, the solid is collected by filtration, the solid is ground, and vacuum drying is performed at 80°C for more than 8h, so that the regeneration of the chromatographic material is completed.

[0010] As a further preferred embodiment of the above technical solution, before the dipyridyl monocation salt crystal material is used to adsorb and separate aromatic hydrocarbons from naphthenes, the dipyridyl monocation salt crystal material is activated, and the activation operation is as follows: recrystallizing the dipyridyl monocation salt crystal material in a poor solvent, soaking the obtained solid in dichloromethane, collecting the solid by filtration, and heating the solid to remove residual solvent, so that the activation of the dipyridyl monocation salt crystal material is realized.

[0011] As a further preferred embodiment of the above technical solution, the poor solvent comprises at least one of isopropyl ether and ethyl acetate.

[0012] The present application has the following advantages: The present application utilizes a specific crystal material to selectively adsorb aromatic hydrocarbons from naphthenes, and the adsorption process is simple, selective, and effective, does not require complex equipment, and is low in cost, so that it is suitable for large-scale industrial production. BRIEF DESCRIPTION OF DRAWINGS

[0013] Figure 1 A nuclear magnetic resonance hydrogen spectrum of a dipyridyl monocation salt crystal material (T1) of the present application in deuterated acetonitrile.

[0014] Figure 2 The nuclear magnetic resonance hydrogen spectrum of the bipyridinium monocation salt crystal material (OH-T3) of the present application in deuterated acetonitrile.

[0015] Figure 3 The nuclear magnetic resonance hydrogen spectrum of the bipyridinium monocation salt crystal material (SA6) of the present application in deuterated acetonitrile.

[0016] Figure 4 The nuclear magnetic resonance hydrogen spectrum of the bipyridinium monocation salt crystal material (Me-SA3) of the present application in deuterated acetonitrile.

[0017] Figure 5 The nuclear magnetic resonance hydrogen spectrum of the bipyridinium monocation salt crystal material (Et-SA3) of the present application in deuterated acetonitrile.

[0018] Figure 6 The nuclear magnetic resonance hydrogen spectrum of the crystal material of Example 1 in deuterated acetonitrile before and after adsorptive separation of benzene and cyclohexane mixed vapors.

[0019] Figure 7 The nuclear magnetic resonance hydrogen spectrum of the crystal material of Example 2 in deuterated acetonitrile before and after adsorptive separation of toluene and methylcyclohexane mixed vapors.

[0020] Figure 8 The nuclear magnetic resonance hydrogen spectrum of the crystal material OH-T3 of Example 1 in deuterated acetonitrile before and after adsorptive separation of benzene and cyclohexane mixed vapors.

[0021] Figure 9 The nuclear magnetic resonance hydrogen spectrum of the crystal material OH-T3 of Example 2 in deuterated acetonitrile before and after adsorptive separation of toluene and methylcyclohexane mixed vapors.

[0022] Figure 10 The nuclear magnetic resonance hydrogen spectrum of the crystal material Me-SA3 of Example 1 in deuterated acetonitrile before and after adsorptive separation of benzene and cyclohexane mixed vapors.

[0023] Figure 11 The nuclear magnetic resonance hydrogen spectrum of the crystal material Me-SA3 of Example 2 in deuterated acetonitrile before and after adsorptive separation of toluene and methylcyclohexane mixed vapors.

[0024] Figure 12 The nuclear magnetic resonance hydrogen spectrum of the crystal material Et-SA3 of Example 1 in deuterated acetonitrile before and after adsorptive separation of benzene and cyclohexane mixed vapors.

[0025] Figure 13 The nuclear magnetic resonance hydrogen spectrum of the crystal material Et-SA3 of Example 2 in deuterated acetonitrile before and after adsorptive separation of toluene and methylcyclohexane mixed vapors.

[0026] Figure 14 The image shows the 1H NMR spectra of the crystalline material SA6 in Example 1 before and after adsorption and separation of benzene and cyclohexane mixed vapor in deuterated acetonitrile.

[0027] Figure 15 The image shows the 1H NMR spectra of the crystalline material SA6 in Example 2 before and after adsorption and separation of toluene and methylcyclohexane mixed vapor in deuterated acetonitrile.

[0028] Figure 16 The figure shows the gas chromatography characterization results of the silica gel supporting the crystal material in Example 3 for the separation and purification of a mixed solution of cyclohexane and benzene (the horizontal axis represents the retention time in min; the vertical axis represents the detector signal).

[0029] Figure 17 The image shows the gas chromatography characterization results of the silica gel supporting the crystal material in Example 4 for the separation and purification of a mixed solution of methylcyclohexane and toluene (the horizontal axis represents the retention time in minutes, and the vertical axis represents the detector signal).

[0030] Figure 18 The graph shows the effect of separating and purifying a mixed solution of cyclohexane and benzene when the silica gel loaded with crystal material in Example 3 is recycled.

[0031] Figure 19 The image shows the effect of separating and purifying methylcyclohexane and toluene solutions when the silica gel loaded with crystals in Example 4 is recycled. Detailed Implementation

[0032] The following detailed description is based on embodiments of the present invention, but the present invention can be implemented in many different ways as defined and covered by the claims.

[0033] Of the raw materials used in this invention, compound A can be prepared by conventional Zincke salt preparation methods, while the remaining raw materials are obtained through commercial purchases.

[0034] The chemical structures of the bipyridine monocation salt crystal materials of the present invention are shown in formulas T1, OH-T3, Me-SA, Et-SA3, or SA6: .

[0035] The non-crystalline powder of the bipyridine monocation salt crystal material (defined as compound T1) of this invention is an existing material, and its preparation method has been disclosed in *Chemistry-a European Journal*, Vol. 20, 2014, pp. 7054-7060. The prepared compound T1 was characterized by nuclear magnetic resonance, such as... Figure 1The results are as follows: ¹H NMR (500MHz, CD3CN, 298K) δ = 9.05 (d, J = 6.5 Hz, 8H), 8.92 (d, J = 6.0 Hz, 8H), 8.53 (d, J = 7.0 Hz, 8H), 7.96 (d, J = 6.0 Hz, 8H), 7.82 (d, J = 8.5 Hz, 8H), 7.73 (d, J = 9.0 Hz, 8H) ppm.

[0036] The method for preparing the uncrystallized powder of the bipyridine monocation salt crystal material (defined as compound OH-T3) of the present invention includes the following steps: Compound OH-T3 was prepared by reacting tris(4-aminophenyl)methanol with compound A.

[0037] The reaction formula is shown below:

[0038] The prepared compound OH-T3 was characterized by nuclear magnetic resonance, such as... Figure 2 The results are as follows: ¹H NMR (500 MHz, CD3CN, 298 K) δ = 9.10 (t, J = 7.5 Hz, 6H), 8.94 (d, J = 6.0 Hz, 6H), 8.56 (d, J = 5.5 Hz, 6H), 8.00 (d, J = 5.0 Hz, 6H), 7.93 (d, J = 9.0 Hz, 3H), 7.86 (dd, J = 8.5, 7.0 Hz, 6H), 7.78 (d, J = 9.0 Hz, 3H) ppm.

[0039] The amorphous powder of bipyridine monocation salt crystal material (defined as compound SA6) is an existing material, and its preparation method has been disclosed in *Chem*, Vol. 5, 2019, pp. 2353-2364. The prepared compound SA6 was characterized by nuclear magnetic resonance, such as... Figure 3 The results are as follows: ¹H NMR (500 MHz, CD3CN, 298K) δ = 8.83 (d, J = 6.0 Hz, 12H), 8.67 (d, J = 6.5 Hz, 12H), 8.37 (d, J = 6.5 Hz, 12H), 7.71 (d, J = 6.0 Hz, 12H), 6.09 (s, 12H) ppm.

[0040] The method for preparing the uncrystallized powder of the bipyridine monocation salt crystal material (defined as compound Me-SA3) of the present invention includes the following steps: The compound Me-SA3 was prepared by reacting 1,3,5-tris(bromomethyl)-2,4,6-trimethylbenzene with 4,4'-bipyridine.

[0041] The reaction formula is shown below:

[0042] The prepared compound Me-SA3 was characterized by nuclear magnetic resonance, such as... Figure 4 The results are as follows: ¹H NMR (500 MHz, CD3CN, 298K) δ = 8.92 (d, J = 6.5 Hz, 6H), 8.74 (d, J = 6.5 Hz, 6H), 8.39 (d, J = 6.5 Hz, 6H), 8.08 (d, J = 6.5 Hz, 6H), 6.05 (s, 6H), 2.35 (s, 9H) ppm.

[0043] The method for preparing the uncrystallized powder of the bipyridine monocation salt crystal material (defined as compound Et-SA3) of the present invention includes the following steps: The compound Et-SA3 was prepared by reacting 1,3,5-tris(bromomethyl)-2,4,6-triethylbenzene with 4,4'-bipyridine.

[0044] The reaction formula is shown below:

[0045] The prepared compound Et-SA3 was characterized by nuclear magnetic resonance, such as... Figure 5 The results are as follows: ¹H NMR (500 MHz, CD3CN, 298K) δ = 8.90 (d, J = 6.0 Hz, 6H), 8.73 (d, J = 6.5 Hz, 6H), 8.39 (d, J = 6.5 Hz, 6H), 7.89 (d, J = 6.0 Hz, 6H), 5.98 (s, 6H), 2.66 (q, J = 7.0 Hz, 6H), 1.09 (t, J = 7.5 Hz, 9H) ppm.

[0046] Example 1: The method for efficiently separating aromatic hydrocarbons from cycloalkanes in this embodiment includes the following steps: S1. Activation of the uncrystallized powder of the prepared bipyridine monocationic salt crystal material: Taking compound T1 as an example, weigh 500 mg of compound T1 and place it in 10 mL of acetonitrile. Dissolve it completely by ultrasonic vibration. Add the unsuitable solvent isopropyl ether to precipitate the product. Let it stand for more than 1 hour to allow the solid to crystallize. Filter and collect the precipitated crystals. Soak the obtained crystals in dichloromethane for more than 6 hours. Filter and collect the solid. Grind the solid into powder and dry it under vacuum at 80 °C for 8 hours. The yellow powder obtained is the activated crystal material. The activation methods of compounds Et-SA3 and SA6 are exactly the same as those of compound T1. The activation methods of compounds OH-T3 and Me-SA3 are basically the same as those of compound T1. The difference is that the unsuitable solvent used is ethyl acetate.

[0047] S2. Selective adsorption of a mixture of aromatic and cycloalkanes using activated crystalline material: Taking T1 as an example, take a 20mL culture bottle, add 1mL benzene and 1mL cyclohexane, and place 20mg of the activated crystalline material (T1) prepared in S1 into a 3mL open culture bottle. Place the 3mL culture bottle into the 20mL culture bottle, seal the 20mL culture bottle, and place it in a 35℃ environment for 24 hours to complete the selective adsorption. Dissolve the crystalline material after adsorption in deuterated acetonitrile, and detect the adsorption effect by proton nuclear magnetic resonance spectroscopy (e.g., Figure 6 (As shown). Only benzene was observed in the 1H NMR spectrum; cyclohexane was not observed, demonstrating the high selectivity of the crystalline material for benzene adsorption. The operation method for other crystalline materials is the same as for T1. When using other bipyridine monocation salt crystalline materials for adsorption, the 1H NMR spectra of the benzene and cyclohexane mixed vapors before and after adsorption in deuterated acetonitrile are shown below. Figure 8 (Corresponding to OH-T3) Figure 10 (Corresponding to Me-SA3) Figure 12 (Corresponding to Et-SA3) Figure 14 (As shown in SA6).

[0048] S3. Regeneration of crystal materials: Taking T1 as an example, the adsorbed crystal material is soaked in dichloromethane for 6 hours, the solid is collected by filtration, the solid is ground into powder, and vacuum dried at 80 ℃ for 8 hours to obtain the regenerated crystal material. The operation method for other crystal materials is the same as T1.

[0049] Example 2: The process was largely the same as in Example 1, except that in S2, 1 mL of toluene and methylcyclohexane were used instead of 1 mL of benzene and cyclohexane. The T1 crystal material after adsorption was dissolved in deuterated acetonitrile, and the adsorption effect was detected by 1H NMR spectroscopy (e.g., ...). Figure 7(As shown). Only toluene was observed in the 1H NMR spectrum; methylcyclohexane was not observed, demonstrating the high selectivity of the crystalline material for toluene adsorption. The operation method for other crystalline materials is the same as for T1. When using other bipyridine monocation salt crystalline materials for adsorption, the 1H NMR spectra of the benzene and cyclohexane mixed vapors before and after adsorption in deuterated acetonitrile are shown below. Figure 9 (Corresponding to OH-T3) Figure 11 (Corresponding to Me-SA3) Figure 13 (Corresponding to Et-SA3) Figure 15 (As shown in SA6).

[0050] Example 3: The method for efficiently separating aromatic hydrocarbons from cycloalkanes in this embodiment includes the following steps: S1. Activate the obtained bipyridine monocationic salt crystal material powder: The activation method is the same as in Example 1.

[0051] S2. Loading of Crystalline Material: Taking T1 as an example, weigh 500 mg of activated crystalline material and 2500 mg of commercial column chromatography silica gel (100-200 mesh, but not limited to this mesh size), mix them in a mortar, and grind them to obtain column chromatography silica gel loaded with crystalline material, denoted as T1-SG. Fill the glass chromatography column with the loaded silica gel to complete the construction of the separation device. The loading method for other crystalline materials is the same as that for T1 crystalline material.

[0052] S3. Separation and purification of aromatic hydrocarbons and cyclic aliphatic hydrocarbons: Taking T1-SG as an example, 10 mL of 99% pure cyclohexane (benzene to cyclohexane mass fraction ratio of 1:99) was poured into a glass chromatography column. The filtrate at the bottom of the column was collected. Gas chromatography results showed that T1-SG could separate and purify benzene and cyclohexane. The purity of the purified cyclohexane (e.g., ...) was... Figure 16 >99.999%.

[0053] S4. Reuse of Column Chromatography Silica Gel Loaded with Crystalline Materials: Taking T1-SG as an example, the purified T1-SG is soaked in dichloromethane for at least 6 hours, the solid is collected by filtration, ground, and vacuum dried at 80 °C for at least 8 hours to obtain regenerated T1-SG. The regeneration method for column chromatography silica gel loaded with other crystalline materials is the same as that for T1-SG. The regenerated T1-SG (3000 mg) is reused in the separation and purification step of S3. The filtrate at the bottom of the chromatography column is analyzed by gas chromatography, and the results are as follows. Figure 18 As shown, T1-SG can selectively adsorb benzene to purify cyclohexane and methylcyclohexane, with a cyclohexane purity >99.999%, and its selectivity does not decrease after being reused 5 times.

[0054] Example 4: The method for efficiently separating aromatic hydrocarbons from cycloalkanes in this embodiment is basically the same as that in Example 3, except that in S3, the substance to be separated and purified is replaced by 10 mL of 99% pure cyclohexane (the mass fraction ratio of benzene to cyclohexane is 1:99) instead of 10 mL of 99% pure methylcyclohexane (the mass fraction ratio of toluene to methylcyclohexane is 1:99).

[0055] Gas chromatography analysis of the filtrate at the bottom of the chromatography column showed that T1-SG could separate and purify toluene and methylcyclohexane. The purified methylcyclohexane had a purity (e.g., Figure 17 >99.999%.

[0056] The regenerated T1-SG (500 mg) from this embodiment was reused in the separation and purification step S3. The filtrate at the bottom of the chromatography column was analyzed by gas chromatography, and the results are as follows. Figure 19 As shown, T1-SG can selectively adsorb toluene to purify methylcyclohexane, achieving a purity of >99.999%, and its selectivity does not decrease after being reused 5 times.

[0057] The above are merely preferred embodiments of the present invention, and the scope of protection of the present invention is not limited to the above embodiments. For those skilled in the art, improvements and modifications obtained without departing from the inventive concept should also be considered within the scope of protection of the present invention.

[0058] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for efficiently separating aromatic hydrocarbons from cycloalkanes, characterized in that, Aromatic hydrocarbons in cycloalkanes are adsorbed and separated using bipyridine monocationic salt crystal materials; the chemical structures of the bipyridine monocationic salt crystal materials are shown as formulas T1, OH-T3, Me-SA, Et-SA3, or SA6. 。 2. The method for efficiently separating aromatic hydrocarbons from cycloalkanes according to claim 1, characterized in that, The process includes the following steps: vaporizing the cycloalkanes containing aromatic hydrocarbons to form a mixed steam, placing the bipyridine monocation salt crystal material in the mixed steam, and adsorbing it at 80°C. After adsorption, the aromatic hydrocarbons are fixed in the bipyridine monocation salt crystal material.

3. The method for efficiently separating aromatic hydrocarbons from cycloalkanes according to claim 2, characterized in that, After adsorption is complete, the bipyridine monocation salt crystal material is soaked in dichloromethane for more than 6 hours, the solid is collected by filtration, the solid is ground into powder, and vacuum dried at 80~120℃ for more than 8 hours to complete the regeneration of the bipyridine monocation salt crystal material.

4. The method for efficiently separating aromatic hydrocarbons from cycloalkanes according to claim 1, characterized in that, The process includes the following steps: mixing and grinding the bipyridine monocation salt crystal material with chromatographic silica gel to obtain a chromatographic material; filling the chromatographic material into a chromatography apparatus; pouring a cycloalkanes mixture containing aromatic hydrocarbons into the chromatography apparatus for chromatography; and collecting the filtrate at the bottom of the chromatography apparatus to obtain the purified cycloalkanes.

5. The method for efficiently separating aromatic hydrocarbons from cycloalkanes according to claim 4, characterized in that, After chromatography, the chromatographic material is soaked in dichloromethane for more than 6 hours, the solid is collected by filtration, the solid is ground and then vacuum dried at 80°C for more than 8 hours to complete the regeneration of the chromatographic material.

6. The method for efficiently separating aromatic hydrocarbons from cycloalkanes according to any one of claims 1-5, characterized in that, Before using the bipyridine monocationic salt crystal material to adsorb and separate aromatic hydrocarbons from cycloalkanes, the bipyridine monocationic salt crystal material is activated. The activation process is as follows: the bipyridine monocationic salt crystal material is recrystallized in a poor solvent, the solid obtained from recrystallization is soaked in dichloromethane, the solid is collected by filtration, and the solid is heated to remove the remaining solvent, thereby realizing the activation of the bipyridine monocationic salt crystal material.

7. The method for efficiently separating aromatic hydrocarbons from cycloalkanes according to claim 6, characterized in that, The undesirable solvents include at least one of isopropyl ether and ethyl acetate.

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