A method for separating a mixture of binary substituted benzene isomers by liquid phase adsorption

Abstract

The invention discloses a method for separating a mixture of binary substituted benzene isomers by liquid phase adsorption, and one or more of the binary substituted benzene isomers can be separated according to the different mixing ratios of two aluminum-based metal organic framework materials CAU-23 (Al) and MIL-160 (Al), wherein the organic ligands of the aluminum-based metal organic framework materials are 2,5-thiophene dicarboxylic acid and 2,5-furan dicarboxylic acid. The method of the invention can effectively separate the binary substituted benzene isomers in the liquid phase, and the organic ligands and metal salts required for the preparation of the aluminum-based metal organic framework materials used in the invention are cheap and readily available, the synthesis conditions are green and mild, the purification steps are simple, no organic solvent is required, and it is easy to operate and scale up. Therefore, the method of the invention has good industrial application prospects.

Description

Technical Field

[0001] The invention relates to the technical field of adsorption separation, in particular to a method for separating a binary substituted benzene isomer mixture by liquid phase adsorption. Background Art

[0002] The rapid development of industry is inseparable from the delivery of high-purity raw materials, so the separation and purification of products has become an indispensable and important link in industrial production.

[0003] Disubstituted benzene isomers (such as xylene, chlorotoluene, dichlorobenzene, dibromobenzene, bromotoluene and nitrotoluene, etc.) play an important role in the petrochemical industry. For example, p-xylene among xylene isomers is an important raw material for the synthesis of terephthalic acid; the synthesis of dye intermediates is inseparable from cresol and nitrotoluene isomers; chlorotoluene isomers are important basic chemical raw materials for high value-added chemical products such as pesticides and synthetic resins. However, the physical properties of disubstituted benzene isomers are very similar, making it very difficult to separate the mixture of disubstituted benzene isomers to obtain a single component of disubstituted benzene isomers. Taking the separation of xylene isomers as an example, since the boiling points and kinetic diameters of the three xylene molecules are extremely similar, their separation is very difficult. Although distillation, membrane separation and crystallization can separate xylene isomers, there are problems such as low separation efficiency and high energy consumption. The adsorption separation principle is relatively flexible, and has the advantages of high efficiency, mildness, low energy consumption and wide applicability. The industrial-grade separation technology based on this method is simulated moving bed technology. The adsorbent used is generally cation exchange X molecular sieve or Y molecular sieve. This type of adsorbent preferentially adsorbs p-xylene and cannot separate o-xylene and m-xylene. In addition, the separation efficiency of the simulated moving bed is limited by the limited specific surface area of ​​the molecular sieve, the saturated adsorption capacity is small, and the adsorption selectivity is also low, which makes the xylene selective adsorption separation efficiency of the simulated moving bed not high. Therefore, there is an urgent need for an adsorbent material that can separate the three components of o-, m-, and p-xylene and has both high adsorption capacity and high selectivity.

[0004] Metal Organic Frameworks (MOFs) are a new type of porous material composed of metal ions or clusters and organic ligands connected by coordination bonds. Compared with traditional adsorption materials such as molecular sieves and activated carbon, MOFs have the advantages of strong design, high specific surface area, adjustable pore size, surface functionalization and diverse structures. They have been widely used in the field of adsorption separation in recent years. They also show good potential in the field of adsorption separation of xylene, but their industrial application prospects are limited by the expensive organic ligands and harsh synthesis conditions. Moreover, when MOFs are used as fixed bed adsorbents to separate liquid phase xylene isomers, solvent elution is required to obtain pure components of xylene isomers. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a method for separating a mixture of binary substituted benzene isomers (xylene, chlorotoluene, dichlorobenzene, dibromobenzene, bromotoluene and nitrotoluene) in a liquid phase by mixing two aluminum-based metal organic framework materials as an adsorption stationary phase, so as to solve the problems raised in the above-mentioned background technology.

[0006] In order to solve the above technical problems, the technical solution provided by the present invention is: a method for separating a mixture of binary substituted benzene isomers by liquid phase adsorption, wherein an aluminum-based metal organic framework material is used as an adsorbent and a mixed liquid of binary substituted benzene isomers is used as a substrate to be separated, wherein the adsorbent is composed of a powder mixture of two aluminum-based metal organic framework materials, CAU-23 (Al) and MIL-160 (Al), and the adsorbent is used to separate the binary substituted benzene isomers in the liquid phase.

[0007] As an improvement, the aluminum-based metal-organic framework material includes metal ions and organic ligands, the metal ions are selected from at least one of the metal salts aluminum chloride, sodium aluminate, basic aluminum acetate, aluminum chloride hexahydrate, aluminum sulfate 18hydrate, and aluminum nitrate nonahydrate; the organic ligands are 2,5-thiophene dicarboxylic acid and 2,5-furan dicarboxylic acid.

[0008] As an improvement, the disubstituted benzene isomers include xylene, chlorotoluene, dichlorobenzene, dibromobenzene, bromotoluene, and nitrotoluene isomers.

[0009] As an improvement, the xylene isomers include any combination of o-xylene, m-xylene and p-xylene; the chlorotoluene isomers include any combination of o-chlorotoluene, m-chlorotoluene and p-chlorotoluene; the dichlorobenzene isomers include any combination of o-dichlorobenzene, m-dichlorobenzene and p-dichlorobenzene; the dibromobenzene isomers include any combination of o-dibromobenzene, m-dibromobenzene and p-dibromobenzene; the bromotoluene isomers include any combination of o-bromotoluene, m-bromotoluene and p-bromotoluene; the nitrotoluene isomers include any combination of o-nitrotoluene, m-nitrotoluene and p-nitrotoluene.

[0010] As an improvement, the aluminum-based metal organic framework material can be prepared into cylindrical particles by tabletting.

[0011] In the present application, the adsorption separation is carried out using a fixed bed, and an adsorbent or a mixed adsorbent is loaded into the fixed bed packing column, comprising the following steps:

[0012] Step 1: There are two filling methods for the mixed adsorbent to be filled into the fixed bed column. The filling method is any of the following methods:

[0013] Method 1: physically mix at least two adsorbents in a certain ratio and then load them into a fixed bed column;

[0014] Method 2: at least two adsorbents are filled in series in a certain ratio into a fixed bed column.

[0015] Step 2: Passing the mixed solution of binary substituted benzene isomers into the fixed bed packed column, and separating different binary substituted benzene isomers by adjusting the ratio of the mixed aluminum-based metal organic framework material and controlling the time of the effluent.

[0016] Step 3: The disubstituted benzene isomers with strong adsorption capacity in the mixed solution of disubstituted benzene isomers are adsorbed on the adsorbent, and the disubstituted benzene isomers with weak adsorption capacity in the mixed solution of disubstituted benzene isomers are preferentially discharged from the adsorption column to obtain disubstituted benzene isomers with weak adsorption capacity;

[0017] Step 4: Desorb the disubstituted benzene isomer with strong adsorption capacity using a weakly polar solvent to obtain the disubstituted benzene isomer with strong adsorption capacity.

[0018] Optionally, the mass ratio of the hybrid aluminum-based metal-organic framework material is 1:1 to 1:9.

[0019] Optionally, the concentration of the mixed solution containing disubstituted benzene isomers is 0.01-0.3 mol / L; the flow rate of the mixed solution passing into the packed column is 0.5-2 mL / min;

[0020] Preferably, the mixed liquid contains a solvent; the solvent is selected from at least one of n-hexane, n-heptane, isooctane and mesitylene.

[0021] Optionally, the adsorbent in the packed column can be regenerated;

[0022] The regeneration method is any of the following methods:

[0023] Method 1: Use any solvent among ethanol, n-hexane and n-heptane to directly pass into the packed column for flushing to obtain the regenerated adsorbent;

[0024] Method 2: The adsorbent after adsorption and separation of binary substituted benzene isomers is placed in ethanol, n-hexane and n-heptane for soaking and desorption to obtain a regenerated adsorbent;

[0025] Method 3: After the adsorbent for separation of the binary substituted benzene isomers is adsorbed, any one of ethanol, n-hexane and n-heptane is used as an extraction solvent, and extraction is performed using a Soxhlet extractor to obtain a regenerated adsorbent.

[0026] The advantages of the present invention compared with the prior art are:

[0027] 1) In the present invention, the aluminum-based metal organic framework materials CAU-23 (Al) and MIL-160 (Al) are prepared by reacting organic ligands with metal salts in pure water, without the need to use volatile organic solvents that pollute the environment, and the only reaction by-product is sodium chloride. The required raw materials are low in price, the synthesis conditions are mild, the post-treatment is convenient, the material synthesis cost is low, and it is easy to scale up production.

[0028] 2) In the present invention, the aluminum-based metal organic framework material used has stable performance and good water stability. After multiple adsorption-regeneration, the adsorption performance still maintains the original level.

[0029] 3) The present invention can purify a mixture of binary substituted benzene isomers of different components by regulating the ratio of physical mixing or series connection of aluminum-based metal organic framework materials, and shows great application potential in the field of adsorption separation of binary substituted benzene isomers. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 : is the XRD pattern of CAU-23(Al) prepared in the example of the present invention.

[0031] Figure 2 (a) N2 adsorption-desorption isotherm and (b) pore size distribution diagram of CAU-23(Al) at 77K in an embodiment of the present invention.

[0032] Figure 3 The adsorption isotherm of single-component xylene by CAU-23 (Al) in the embodiment of the present invention (a) and the three-component competitive adsorption of xylene for adsorption separation (b).

[0033] Figure 4 (a) is the breakthrough curve (a) of three-component xylene with equal molar concentrations of CAU-23(Al) at 25°C (single-component solution concentration is 0.05 mol / L) and desorption curve (b) in an embodiment of the present invention.

[0034] Figure 5 It is the XRD pattern of MIL-160(Al) prepared in the embodiment of the present invention.

[0035] Figure 6 (a) N2 adsorption-desorption isotherm and (b) pore size distribution diagram of MIL-160(Al) at 77K in an embodiment of the present invention.

[0036] Figure 7 It is the adsorption isotherm of single-component xylene adsorbed by MIL-160 (Al) in the embodiment of the present invention (a) and the three-component competitive experiment of xylene adsorption separation (b).

[0037] Figure 8It is the breakthrough curve (a) of three-component xylene with equal molar concentration of MIL-160 (Al) at 25°C (the concentration of the single-component solution is 0.1 mol / L) and the desorption curve (b) in the embodiment of the present invention.

[0038] Fig. 9 These are the penetration curves of three-component xylene with equimolar concentrations of the mixed adsorbent of CAU-23(Al) and MIL-160(Al) at 25°C in the embodiment of the present invention (the concentration of the single-component solution is 0.1 mol / L). The mixing ratio of CAU-23(Al):MIL-160(Al) is 3:7 (a) The mixing ratio of CAU-23(Al):MIL-160(Al) is 4:6 (b) The mixing ratio of CAU-23(Al):MIL-160(Al) is 5:5 (c) The mixing ratio of CAU-23(Al):MIL-160(Al) is 6:4 (d) The mixing ratio of CAU-23(Al):MIL-160(Al) is 7:3 (e). DETAILED DESCRIPTION

[0039] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention, but the present invention is not limited to these embodiments.

[0040] Unless otherwise specified, the raw materials in the examples of the present invention were purchased from commercial sources.

[0041] The synthesis of the aluminum-based metal organic framework material in the present invention refers to the literature (Lenzen.D, Zhao.J, Ernst.SJ, Wahiduzzaman.M, Ken Inge.A, Frohlich.D, Xu.H, Bart.HJ, Janiak.C, Henninger.S, Maurin.G, Zou.X, Stock.N, A metal-organic framework for efficient water-based ultra-low-temperature-driven cooling[J]. Nat Commun, 2019, 10(1): 3025.) and (Schlusener.C, Jordan.DN, Xhinovci.M, Matemb Ma Ntep.TJ, Schmitz.A, Giesen.B, Janiak.C, Probing the limits of linker substitution in aluminum MOFs throughwater vapor sorption studies: mixed-MOFs instead of mixed-linker CAU-23andMIL-160materials[J]. Dalton Trans,2020,49(22):7373-7383.).

[0042] In the examples of the present invention, the X-ray powder diffraction phase analysis (XRD) of the product adopts Ultima IV X-ray powder diffractometer of Rigaku Company of Japan, Cu target, Kα radiation source (λ=0.154nm), voltage 40kV, current 30mA.

[0043] In the embodiments of the present invention, the physical adsorption and pore distribution of the product were analyzed using ASAP 2460 specific surface area and porosity analyzer from Micromeritics.

[0044] In the embodiments of the present invention, the adsorption performance is evaluated using a Shimadzu GC-2030 gas chromatograph, and the detection conditions are as follows: capillary column: a polar polyethylene glycol stationary phase capillary chromatographic column, such as FFAP; front inlet vaporization chamber temperature: 200-250°C; column temperature is programmed; detector temperature: 200-250°C, carrier gas flow rate 0.5-2mL / min; hydrogen flow rate is 30-40mL / min, and air flow rate is 200-300mL / min.

[0045] Please refer to the attached Figure 1-9 ;

[0046] Before the dynamic penetration experiment in the present application, the adsorbent powder was firstly pressed into cylindrical particles and then loaded into a stainless steel column.

[0047] Preparation of CAU-23(Al)

[0048] 18.75mmol aluminum chloride hexahydrate, 6.25mmol sodium aluminate, 25mmol 2,5-thiophenedicarboxylic acid, 50mmol sodium hydroxide, and 130mL deionized water were mixed and stirred under reflux at 100°C for 6 hours. After the reaction was completed, the solid obtained by the reaction was dispersed in 200mL deionized water and washed three times, filtered and vacuum dried at 120°C for 1 day to obtain the purified aluminum-based metal organic framework material CAU-23(Al).

[0049] The CAU-23 (Al) prepared in this example was characterized, and the results were as follows:

[0050] Figure 1 This is the XRD spectrum of CAU-23(Al) obtained in this example. It can be seen that the synthesized CAU-23(Al) has good crystallinity.

[0051] Figure 2 (a) is the N2 adsorption-desorption isotherm of CAU-23(Al) prepared in this example at 77K. It can be seen that the CAU-23(Al) material has a microporous structure with a specific surface area of ​​1252 m 2 / g.

[0052] Figure 2 (b) is the pore size distribution diagram of CAU-23(Al) obtained in this example. It can be seen that the average pore size distribution of CAU-23(Al) is

[0053] CAU-23(Al) single component xylene static adsorption performance test

[0054] In order to test the adsorption performance of the synthesized CAU-23(Al) on xylene isomers (o-xylene, m-xylene, p-xylene), a single-component xylene static adsorption experiment was carried out using the CAU-23(Al) adsorbent in this example.

[0055] Using n-heptane as solvent, a series of single-component o-xylene / m-xylene / p-xylene adsorption solutions with concentration gradients (0.01 mol / L, 0.03 mol / L, 0.05 mol / L, 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, 0.6 mol / L) were prepared. 100 mg of CAU-23 (Al) was weighed and added to the above adsorption solution. A blank control group was set up at the same time. After shaking at 100 rpm in a constant temperature 20°C shaker for 4 hours, the concentrations of each component in the blank control group and the concentrations of each component after adsorption were detected by gas chromatography, and the adsorption amount of xylene isomers of each component was calculated. The single-component xylene adsorption isotherm is shown in Figure 2. Figure 3 (a). Figure 3 (a) It can be seen that when n-heptane is used as the solvent, CAU-23(Al) preferentially adsorbs o-xylene, followed by m-xylene, and finally p-xylene. The maximum adsorption amounts of o-xylene, m-xylene, and p-xylene are 1.90 mmol / g, 0.97 mmol / g, and 0.95 mmol / g, respectively.

[0056] CAU-23(Al) three-component xylene static adsorption performance test

[0057] In order to test the separation performance of the above-synthesized CAU-23(Al) for xylene isomers (o-xylene, m-xylene, p-xylene), a three-component xylene static adsorption experiment was carried out using the CAU-23(Al) adsorbent in this example.

[0058] Using n-heptane as solvent, a series of three-component xylene mixed solutions with equal molar ratios were prepared (the concentration of each component was 0.01 mol / L, 0.03 mol / L, 0.05 mol / L, 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, and 0.6 mol / L), 100 mg of CAU-23 (Al) was weighed and added to the above adsorption solution, and a blank control group was set up at the same time. After shaking at 100 rpm in a constant temperature shaker at 20 ° C for 4 hours, the concentration of each component in the blank control group and the concentration of each component after adsorption were detected by gas chromatography, and the adsorption amount of xylene isomers of each component was calculated. Figure 3(b) is the three-component xylene competitive adsorption diagram of CAU-23 (Al). It can be seen from the figure that the three xylene isomers are in a co-adsorbed state. For the o-xylene isomer, the adsorption amount increases continuously with the increase of solution concentration, and reaches 1.3mmol / g when the initial concentration is 0.6mol / L; while the adsorption amount of m-xylene and p-xylene shows an increasing trend when the concentration is less than 0.3mol / L, and first shows a decreasing trend and then basically remains constant when the concentration is greater than 0.3mol / L; the maximum adsorption amount of m-xylene is 0.26mmol / g, and the maximum adsorption amount of p-xylene is 0.19mmol / g; and the adsorption order of the three-component xylene competitive adsorption experiment is also o-xylene>m-xylene>p-xylene, which is consistent with the adsorption order of the single-component xylene adsorption experiment in the CAU-23 (Al) single-component xylene static adsorption performance test. The difference is that the three-component competitive adsorption test reflects competitive adsorption. Under the interference of m-xylene and p-xylene, CAU-23 (Al) still preferentially adsorbs o-xylene while adsorbing very little m-xylene and p-xylene. This shows that CAU-23 (Al) can well separate o-xylene from the xylene mixed solution.

[0059] Dynamic penetration test of three-component xylene in CAU-23(Al)

[0060] The above CAU-23 (Al) adsorbent was activated in a vacuum drying oven at 120°C, and then the adsorbent was loaded into a 200mm×10mm stainless steel column. Before the penetration experiment, the column was flushed with pure n-heptane solution at a flow rate of 1mL / min for 1h. In the experiment, the n-heptane solution was replaced with a three-component mixed solution of xylene (the concentration of each component was 0.05mol / L), with a flow rate of 1mL / min. From the first drop of liquid dripping into the sampling bottle, a sample was taken every minute until the effluent concentration reached the initial injection concentration. After the experiment was completed, the column was flushed with pure n-heptane solution at a speed of 1mL / min for 2h, and the concentration of each component of the effluent was detected by gas chromatograph, and a curve of the effluent concentration changing with time was drawn.

[0061] Figure 4 (a) is the penetration curve of three components of xylene with equal molar concentrations of CAU-23 (Al) at 25°C. It can be seen in the figure that p-xylene begins to penetrate at 12 minutes, followed by m-xylene at 14 minutes, indicating that the adsorption of p-xylene and m-xylene by CAU-23 (Al) material is weak, while o-xylene begins to penetrate and precipitate after being retained in the packed column for 34 minutes, indicating that the adsorption amount of o-xylene by CAU-23 (Al) material is high and the adsorption effect is strong. This is consistent with the conclusion of the above static adsorption experiment results. The difference in retention time shows that xylene has been effectively separated.

[0062] Figure 4 (b) is the desorption curve of the packed column after washing with n-heptane solution. It can be seen from the figure that p-xylene and m-xylene are completely eluted from the packed column at 30min and 40min respectively, while o-xylene is completely eluted at 120min. From the desorption experiment, we can obtain an n-heptane solution rich in o-xylene.

[0063] Preparation of MIL-160(Al)

[0064] 4.69mmol aluminum chloride hexahydrate, 1.56mmol sodium aluminate, 6.26mmol 2,5-furandicarboxylic acid, 12.5mmol sodium hydroxide, and 32.5mL deionized water were mixed and stirred under reflux at 100°C for 24 hours. After the reaction was completed, the solid obtained by the reaction was dispersed in 50mL deionized water and washed three times, filtered and vacuum dried at 120°C for 1 day to obtain the purified aluminum-based metal organic framework material MIL-160 (Al).

[0065] The MIL-160 (Al) prepared in this example was characterized, and the results were as follows:

[0066] Figure 5 This is the XRD spectrum of the obtained MIL-160(Al), from which we can see that the MIL-160(Al) material has good crystallinity.

[0067] Figure 6 (a) is the N2 adsorption-desorption isotherm of MIL-160(Al) at 77K. It can be seen that the MIL-160(Al) material has a microporous structure with a specific surface area of ​​1082 m 2 / g.

[0068] Figure 6 (b) is the pore size distribution diagram of MIL-160(Al) obtained. It can be seen that the average pore size distribution of MIL-160(Al) is

[0069] MIL-160(Al) single component xylene static adsorption performance test

[0070] In order to test the adsorption performance of the above-synthesized MIL-160(Al) on xylene isomers (o-xylene, m-xylene, p-xylene), a single-component xylene static adsorption experiment was carried out using the above-synthesized MIL-160(Al) adsorbent.

[0071] Using n-heptane as solvent, a series of single-component o-xylene / m-xylene / p-xylene adsorption solutions with a concentration gradient (0.01mol / L, 0.03mol / L, 0.05mol / L, 0.1mol / L, 0.2mol / L, 0.3mol / L, 0.4mol / L, 0.5mol / L, 0.6mol / L) were prepared, 100mg of MIL-160 (Al) was weighed and added to the above adsorption solution, and a blank control group was set up at the same time. After shaking at 100rpm in a constant temperature 20℃ shaker for 4 hours, the concentration of each component in the blank control group and the concentration of each component after adsorption were detected by gas chromatography, and the adsorption amount of xylene isomers of each component was calculated. The single-component xylene adsorption isotherm is shown in Figure 2. Figure 7 (a). Figure 7 (a) It can be seen that when n-heptane is used as the solvent, MIL-160(Al) preferentially adsorbs m-xylene in xylene, followed by p-xylene, and finally o-xylene. The maximum adsorption amounts of m-xylene, p-xylene, and o-xylene are 1.30 mmol / g, 1.11 mmol / g, and 0.65 mmol / g, respectively.

[0072] MIL-160(Al) three-component xylene static adsorption performance test

[0073] In order to test the separation performance of the above-synthesized MIL-160(Al) for xylene isomers (o-xylene, m-xylene, p-xylene), a three-component xylene static adsorption experiment was carried out using the above-synthesized MIL-160(Al) adsorbent.

[0074] Using n-heptane as solvent, a series of three-component xylene mixed solutions with equal molar ratios were prepared (the concentration of each component was 0.01 mol / L, 0.03 mol / L, 0.05 mol / L, 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, and 0.6 mol / L), 100 mg of MIL-160 (Al) was weighed and added to the above adsorption solution, and a blank control group was set up at the same time. After shaking at 100 rpm in a constant temperature shaker at 20 ° C for 4 hours, the concentration of each component in the blank control group and the concentration of each component after adsorption were detected by gas chromatography, and the adsorption amount of xylene isomers of each component was calculated. Figure 7(b) is the competitive adsorption diagram of three components of xylene by MIL-160 (Al). It can be seen from the figure that the three xylene isomers are in a co-adsorption state. For the m-xylene isomer, the adsorption amount increases continuously with the increase of solution concentration, and reaches 0.95mmol / g when the initial concentration is 0.6mol / L; while the adsorption amount of p-xylene and o-xylene increases when the concentration is less than 0.1mol / L, and first decreases when the concentration is greater than 0.1mol / L and then remains basically constant; the maximum adsorption amount of p-xylene is 0.17mmol / g, and the maximum adsorption amount of o-xylene is 0.16mmol / g; and the adsorption order of the three-component xylene competitive adsorption experiment is also m-xylene>p-xylene>o-xylene, which is consistent with the adsorption order of the single-component xylene adsorption experiment in the static adsorption performance test of single-component xylene by MIL-160 (Al). The difference is that the three-component competitive adsorption test reflects competitive adsorption. Under the interference of o-xylene and p-xylene, MIL-160 (Al) still preferentially adsorbs m-xylene while adsorbing very little o-xylene and p-xylene. This shows that MIL-160 (Al) can well separate m-xylene from the xylene mixed solution.

[0075] Dynamic penetration test of three components of MIL-160(Al) into xylene

[0076] The synthesized MIL-160 (Al) adsorbent was activated in a vacuum drying oven at 120°C, and then loaded into a 200mm×10mm stainless steel column. Before the penetration experiment, the column was flushed with pure n-heptane solution at a flow rate of 1mL / min for 1h. In the experiment, the n-heptane solution was replaced with a three-component mixed solution of xylene (the concentration of each component was 0.1mol / L), with a flow rate of 1mL / min. From the first drop of liquid dripping into the sampling bottle, a sample was taken every minute until the effluent concentration reached the initial injection concentration. After the experiment was completed, the column was flushed with pure n-heptane solution at a speed of 1mL / min for 5h, and the concentration of each component of the effluent was detected by gas chromatograph, and a curve of the effluent concentration changing with time was drawn.

[0077] Figure 8(a) is the penetration curve of three components of xylene with equal molar concentrations of MIL-160 (Al) at 25°C. It can be seen in the figure that p-xylene begins to penetrate at 14 minutes, followed by o-xylene at 20 minutes, indicating that MIL-160 (Al) has weak adsorption effects on p-xylene and m-xylene, while o-xylene begins to penetrate and precipitate after being retained in the packed column for 38 minutes, indicating that MIL-160 (Al) has a high adsorption amount and strong adsorption effect on o-xylene. Different from the above static adsorption experiment, the adsorption order of the penetration experiment is m-xylene > o-xylene > p-xylene, which may be caused by kinetic factors. In addition, MIL-160 (Al) can simultaneously separate the three isomers through the penetration experiment, which is quite rare in MOF materials.

[0078] Figure 8 (b) is the desorption curve of the packed column after washing with n-heptane solution. It can be seen in the figure that p-xylene and o-xylene are eluted very quickly, and 90% can be eluted in 50 minutes, while m-xylene is eluted slowly due to its large adsorption capacity. From the desorption experiment, we can obtain an n-heptane solution rich in m-xylene.

[0079] Dynamic penetration experiment of three-component xylene on CAU-23(Al) and MIL-160(Al) mixed adsorbent

[0080] The activated CAU-23 (Al) and MIL-160 (Al) were physically mixed in a certain ratio (mixing ratio of 3:7 to 7:3) and then loaded into a 200mm×10mm stainless steel column. Before the penetration experiment, the column was flushed with pure n-heptane solution at a flow rate of 1mL / min for 1h. In the experiment, the n-heptane solution was replaced with a three-component mixed solution of xylene (the concentration of each component was 0.1mol / L), the flow rate was 1mL / min, and from the first drop of liquid dripping into the sampling bottle, a sample was taken every minute until the effluent concentration reached the initial injection concentration. After the experiment was completed, the column was flushed with pure n-heptane solution at a speed of 1mL / min for 2h, and the concentration of each component of the effluent was detected by gas chromatograph, and a curve of the effluent concentration changing with time was drawn.

[0081] Fig. 9 The figure is the penetration curve of three components of xylene with equal molar concentration at 25°C when the mixing ratio of CAU-23(Al):MIL-160(Al) is 3:7 to 7:3. Fig. 9It can be seen that as the proportion of CAU-23 (Al) increases and the proportion of MIL-160 (Al) decreases, the penetration time of o-xylene is delayed, the penetration time of m-xylene is advanced, and the penetration time of p-xylene remains basically unchanged. When the mixing ratio is 3:7, 4:6 and 5:5, the penetration order is p-xylene > o-xylene > m-xylene. When the mixing ratio is 6:4 and 7:3, the penetration order is p-xylene > m-xylene > o-xylene. When the mixing ratio of CAU-23 (Al): MIL-160 (Al) is 6:4, m-xylene and o-xylene penetrate almost at the same time, and the penetration interval with p-xylene reaches the maximum.

[0082] Static adsorption performance test of three-component dichlorobenzene on CAU-23(Al), MIL-160(Al) and their mixed adsorbents

[0083] In order to test the separation performance of the above-mentioned CAU-23(Al) and MIL-160(Al) and their mixed adsorbents for dichlorobenzenes (o-dichlorobenzene, m-dichlorobenzene and p-dichlorobenzene), a three-component dichlorobenzene static adsorption experiment was carried out using CAU-23(Al) and MIL-160(Al) and their mixed adsorbents.

[0084] Using n-heptane as solvent, a three-component mixed solution of dichlorobenzene (the concentration of each component is 0.5 mol / L) is prepared, 100 mg of CAU-23 (Al) or MIL-160 (Al) or a mixed adsorbent of the two (mixing ratio is 2:8 to 8:2) is weighed and added to the above adsorption solution, and a blank control group is set up at the same time. After shaking at 100 rpm in a constant temperature shaker at 20°C for 4 hours, the concentration of each component in the blank control group and the concentration of each component after adsorption are detected by gas chromatography, and the adsorption amount of dichlorobenzene isomers of each component is calculated.

[0085] As can be seen from Table 1, the adsorption order of CAU-23 (Al) is o-dichlorobenzene > m-dichlorobenzene > p-dichlorobenzene, which maintains the same isomer position selectivity as the three-component xylene static adsorption experimental results in the three-component xylene static adsorption performance test of CAU-23 (Al), and still preferentially adsorbs the ortho-dichlorobenzene isomer; the adsorption order of MIL-160 (Al) is m-dichlorobenzene > o-dichlorobenzene > p-dichlorobenzene, which is slightly different from the three-component xylene static adsorption experimental results in the three-component xylene static adsorption performance test of MIL-160 (Al), but still preferentially adsorbs the meta-dichlorobenzene isomer. CAU-23 (Al) and MIL-160 (Al) maintain preferential adsorption of ortho- and meta-dichlorobenzene isomers, and the adsorption amount is significantly different from that of other isomers, which can achieve effective separation of p-dichlorobenzene isomers.

[0086] Table 1 Specific adsorption amount of three dichlorobenzene isomers by CAU-23 (Al), MIL-160 (Al) and their mixed adsorbents

[0087]

[0088] Static adsorption performance test of three-component dibromobenzene on CAU-23(Al), MIL-160(Al) and their mixed adsorbents

[0089] In order to test the separation performance of the above-mentioned CAU-23(Al) and MIL-160(Al) and their mixed adsorbents for dibromobenzenes (o-dibromobenzene, m-dibromobenzene and p-dibromobenzene), a three-component dibromobenzene static adsorption experiment was carried out using CAU-23(Al) and MIL-160(Al) and their mixed adsorbents.

[0090] Using n-heptane as solvent, a three-component mixed solution of dibromobenzene (the concentration of each component is 0.5 mol / L) is prepared, 100 mg of CAU-23 (Al) or MIL-160 (Al) or a mixed adsorbent of the two (mixing ratio is 2:8 to 8:2) is weighed and added to the above adsorption solution, and a blank control group is set up at the same time. After shaking at 100 rpm in a constant temperature 20°C shaker for 4 hours, the concentration of each component in the blank control group and the concentration of each component after adsorption are detected by gas chromatography, and the adsorption amount of dibromobenzene isomers of each component is calculated.

[0091] As can be seen from Table 2, the adsorption order of CAU-23 (Al) is o-dibromobenzene > m-dibromobenzene > p-dibromobenzene, which maintains the same isomer position selectivity as the three-component xylene static adsorption experimental results in the three-component xylene static adsorption performance test of CAU-23 (Al), and still preferentially adsorbs the ortho-dibromobenzene isomer; the adsorption order of MIL-160 (Al) is m-dibromobenzene > o-dibromobenzene > p-dibromobenzene, which is slightly different from the three-component xylene static adsorption experimental results in the three-component xylene static adsorption performance test of MIL-160 (Al), but still preferentially adsorbs the meta-dibromobenzene isomer. CAU-23 (Al) and MIL-160 (Al) maintain preferential adsorption of ortho- and meta-dibromobenzene isomers, and the adsorption amount is significantly different from that of other isomers, which can achieve effective separation of p-dibromobenzene isomers.

[0092] Table 2 Specific adsorption amounts of three dibromobenzene isomers by CAU-23 (Al), MIL-160 (Al) and their mixed adsorbents

[0093]

[0094] Static adsorption performance test of three-component nitrotoluene on CAU-23(Al), MIL-160(Al) and their mixed adsorbents

[0095] In order to test the separation performance of the above-mentioned CAU-23(Al) and MIL-160(Al) and their mixed adsorbents for p-nitrotoluene (o-nitrotoluene, m-nitrotoluene and p-nitrotoluene), a three-component nitrotoluene static adsorption experiment was carried out using CAU-23(Al) and MIL-160(Al) and their mixed adsorbents.

[0096] Using n-heptane as solvent, a three-component mixed solution of nitrotoluene (the concentration of each component is 0.5 mol / L) is prepared, 100 mg of CAU-23 (Al) or MIL-160 (Al) or a mixed adsorbent of the two (mixing ratio is 2:8 to 8:2) is weighed and added to the above adsorption solution, and a blank control group is set up at the same time. After shaking at 100 rpm in a constant temperature shaker at 20°C for 4 hours, the concentration of each component in the blank control group and the concentration of each component after adsorption are detected by gas chromatography, and the adsorption amount of nitrotoluene isomers of each component is calculated.

[0097] As can be seen from Table 3, the adsorption order of CAU-23 (Al) is o-nitrotoluene > p-nitrotoluene > m-nitrotoluene, which is slightly different from the three-component xylene static adsorption experimental results in the three-component xylene static adsorption performance test of CAU-23 (Al), but it still preferentially adsorbs the ortho-nitrotoluene isomer; the adsorption order of MIL-160 (Al) is m-nitrotoluene > o-nitrotoluene > p-nitrotoluene, which is slightly different from the three-component xylene static adsorption experimental results in the three-component xylene static adsorption performance test of MIL-160 (Al), but it still preferentially adsorbs the meta-nitrotoluene isomer. CAU-23 (Al) and MIL-160 (Al) maintain preferential adsorption of ortho- and meta-nitrotoluene isomers, and the adsorption amount is significantly different from that of other isomers, which can achieve effective separation of p-nitrotoluene isomers.

[0098] Table 3 Specific adsorption amount of three nitrotoluene isomers by CAU-23 (Al), MIL-160 (Al) and their mixed adsorbents

[0099]

[0100] The present invention and its embodiments are described above, and such description is not restrictive. The drawings show only one embodiment of the present invention, and the actual structure is not limited thereto. In short, if ordinary technicians in the field are inspired by it, without departing from the purpose of the invention, they can design a structure and embodiment similar to the technical solution without creativity, which should belong to the protection scope of the present invention.

Claims

1. A method for separating a mixture of binary substituted benzene isomers by liquid phase adsorption, characterized in that: An aluminum-based metal organic framework material is used as an adsorbent, and a binary substituted benzene isomer mixture is used as a substrate to be separated. The adsorbent is composed of a powder mixture of two aluminum-based metal organic framework materials, CAU-23 (Al) and MIL-160 (Al). The adsorbent is used to separate the binary substituted benzene isomers in the liquid phase; the binary substituted benzene isomer mixture is selected from the following: A combination of o-xylene, m-xylene and p-xylene; A combination of o-dichlorobenzene, m-dichlorobenzene, and p-dichlorobenzene; A combination of o-dibromobenzene, m-dibromobenzene, and p-dibromobenzene; A combination of o-nitrotoluene, m-nitrotoluene and p-nitrotoluene; The aluminum-based metal organic framework material CAU-23(Al) is composed of metal ions and organic ligands, the organic ligands are 2,5-thiophene dicarboxylic acid, and the metal ions are aluminum ions; The aluminum-based metal-organic framework material MIL-160(Al) is composed of metal ions and organic ligands, the organic ligands are 2,5-furandicarboxylic acid, and the metal ions are aluminum ions.

2. The method for separating a mixture of binary substituted benzene isomers by liquid phase adsorption according to claim 1, characterized in that: The aluminum-based metal organic framework material is prepared into cylindrical particles by tabletting.

3. The method for separating a mixture of binary substituted benzene isomers by liquid phase adsorption according to claim 1, characterized in that: The following steps are involved: Step 1: There are two filling methods for the adsorbent to be filled into the fixed bed column. The filling method is any of the following methods: Method 1: Physically mix the two adsorbents in a certain ratio and then load them into a fixed bed column; Method 2: Two adsorbents are packed in series in a certain ratio into a fixed bed column; Step 2: passing the mixed solution of the disubstituted benzene isomers into the fixed bed packed column, and by adjusting the ratio of the mixed aluminum-based metal organic framework material and controlling the time of the effluent, the different disubstituted benzene isomers can be separated; Step 3: The disubstituted benzene isomers with strong adsorption capacity in the mixed solution of disubstituted benzene isomers are adsorbed on the adsorbent, and the disubstituted benzene isomers with weak adsorption capacity in the mixed solution of disubstituted benzene isomers are preferentially discharged from the adsorption column to obtain disubstituted benzene isomers with weak adsorption capacity; Step 4: Desorb the disubstituted benzene isomer with strong adsorption capacity using a weakly polar solvent to obtain the disubstituted benzene isomer with strong adsorption capacity.

4. The method for separating a mixture of binary substituted benzene isomers by liquid phase adsorption according to claim 3, characterized in that: The mass ratio of the mixed aluminum-based metal organic framework materials in step 2 is 1:1 to 1:

9.

5. The method for separating a mixture of binary substituted benzene isomers by liquid phase adsorption according to claim 3, characterized in that: The concentration of the mixed solution containing disubstituted benzene isomers is 0.01-0.3 mol / L, the flow rate of the mixed solution passing into the filling column is 0.5-2 mL / min, and the mixed solution contains a solvent, which is selected from at least one of n-hexane, n-heptane, isooctane and mesitylene.

6. The method for separating a mixture of binary substituted benzene isomers by liquid phase adsorption according to claim 3, characterized in that: The adsorbent in the packed column can be regenerated.

7. The method for separating a mixture of binary substituted benzene isomers by liquid phase adsorption according to claim 6, characterized in that: The adsorbent regeneration method is any one of the following methods: Method 1: Use any solvent among ethanol, n-hexane and n-heptane to directly pass into the packed column for flushing to obtain the regenerated adsorbent; Method 2: The adsorbent after adsorption and separation of the disubstituted benzene isomers is placed in ethanol, n-hexane and n-heptane for soaking and desorption to obtain the regenerated adsorbent; Method 3: The adsorbent after adsorption and separation of the binary substituted benzene isomers is extracted using any one of ethanol, n-hexane and n-heptane as an extraction solvent using a Soxhlet extractor to obtain a regenerated adsorbent.

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