Zr-based membrane for benzene / cyclohexane separation and its preparation method

Abstract

This invention proposes a Zr-based membrane for separating benzene / cyclohexane and its preparation method. The Zr-based membrane includes Zr-BDC membranes, Zr-BDC-PAA, or Zr-BDC-PVA. A polymer is introduced into the Zr-BDC framework via a secondary growth method to improve the membrane's selectivity for separating benzene / cyclohexane. The Zr-based membrane is directly synthesized using an in-situ growth method, which is simple in process. By adjusting the membrane growth time, good benzene / cyclohexane separation performance is achieved. Zr-BDC-PAA or Zr-BDC-PVA membranes are organic-inorganic hybrid membranes. The addition of polymers can adjust the membrane's pore structure, enhance its polarity, improve the size selectivity for separating benzene / cyclohexane, promote the intercalation of the Zr-BDC membrane, and influence the membrane thickness to some extent. The Zr-BDC membrane, by adjusting the growth time, grows more densely and continuously, thus exhibiting good benzene / cyclohexane separation performance.

Description

Technical Field

[0001] This invention belongs to the field of organic-inorganic hybrid membrane preparation technology. It designs a Zr-based membrane for separating benzene / cyclohexane and its preparation method, which is suitable for the separation of benzene / cyclohexane at different temperatures (30-100℃). Background Technology

[0002] In industrial production, cyclohexane is primarily produced by the hydrogenation of benzene. Inevitably, benzene residue remains in the product. Therefore, the separation of benzene and cyclohexane is crucial to meeting industrial demands for pure cyclohexane. However, benzene and cyclohexane have similar molecular dynamics (differences are only...). These compounds have similar boiling points (difference of only 0.6 K) and form an azeotrope in a 55% benzene / 45% cyclohexane (v / v) mixture. Traditional separation techniques, such as distillation and extraction, struggle to separate them. Vapor permeation, driven by the partial pressure difference between the components on both sides of the membrane, achieves separation by relying on the membrane's selective permeation of components in the mixture. It offers advantages such as simple process, easy operation control, and low equipment cost. Furthermore, it eliminates the need for a third component, resulting in stable product quality and an environmentally friendly process. Pervaporation, as an emerging membrane separation technology with phase change, boasts simple operating conditions, high separation efficiency, and environmental friendliness, and possesses unique advantages in separating near-boiling and azeotropic compounds.

[0003] Currently, common membranes used in the separation research of benzene / cyclohexane include polymer membranes, inorganic zeolite membranes, and organic-inorganic hybrid membranes. Among these, polymer membranes are prone to swelling in organic solvents; some polymer membranes, such as polyvinyl chloride (PVC) membranes, have poor photothermal stability; polyimide membranes have good organic durability, but their permeability to organic liquids is too low. Acrylic acid-methyl acrylate copolymer membranes, ethylene-vinyl alcohol copolymer membranes, and polyvinyl chloride@ethylene-vinyl acetate copolymer membranes are synthesized through copolymerization, but due to their large molecular size and similar aromatic / aliphatic molecular structures, it is difficult to achieve high permeability (flux) and selectivity (separation factor). Inorganic zeolite membranes are expensive to manufacture, require a directing agent for synthesis, and are prone to intergranular defects such as cracks and pinholes during the removal of the directing agent. Among organic-inorganic hybrid membranes, mixed matrix membranes are relatively common, where the filler acts to promote component transport, which can greatly promote the diffusion of benzene within the membrane. However, because fillers (such as CNTs, MOFs, etc.) have a large specific surface area and high surface energy, they are prone to agglomeration in polymer matrices, which can reduce the separation performance of the membrane. Summary of the Invention

[0004] The objective of this invention is to design and develop a Zr-based membrane for the separation of benzene and cyclohexane. This involves introducing a polymer into the Zr-BDC framework via a secondary growth method to improve the membrane's selectivity for benzene / cyclohexane separation. The Zr-based membrane is directly synthesized using an in-situ growth method, which is simple in process. By adjusting the membrane's growth time, excellent benzene / cyclohexane separation performance is achieved. Since temperature significantly affects the benzene / cyclohexane separation performance, the membrane's separation performance at different temperatures (30–100 °C) was tested to optimize the optimal separation temperature.

[0005] The technical solution adopted in this invention is as follows:

[0006] Zr-based membranes for benzene / cyclohexane separation include Zr-BDC membranes, Zr-BDC-PAA or Zr-BDC-PVA; BDC refers to 1,4-phthalic acid ligands.

[0007] The present invention discloses a method for preparing a Zr-based membrane for benzene / cyclohexane separation. The Zr-BDC membrane preparation method includes the following steps:

[0008] 1) The α-alumina support was placed in a reaction vessel containing a mixed solution of zirconium chloride, terephthalic acid, deionized water and N,N-dimethylformamide. The reaction vessel was then placed in a high-temperature drying oven at 120°C for more than 12 hours to obtain a Zr-BDC membrane.

[0009] 2) The Zr-BDC membrane was cleaned with anhydrous ethanol until there was no powder accumulation on the membrane surface. Then the membrane was immersed in anhydrous ethanol to remove the residual solvent in the membrane pores. Finally, it was taken out and dried in a vacuum drying oven at 50-80°C to obtain the Zr-BDC membrane.

[0010] The method for preparing a Zr-based membrane for benzene / cyclohexane separation according to the present invention, the Zr-BDC-PAA or Zr-BDC-PVA preparation method includes the following steps:

[0011] 1) The α-alumina support was placed in a reaction vessel containing a mixed solution of zirconium chloride, terephthalic acid, deionized water and N,N-dimethylformamide. The reaction vessel was then placed in a high-temperature drying oven at 120°C for more than 12 hours to obtain a Zr-BDC membrane.

[0012] 2) Place the obtained Zr-BDC membrane in a reaction vessel containing zirconium chloride, terephthalic acid, deionized water, N,N-dimethylformamide and polyacrylic acid or polyvinyl alcohol, and then place the reaction vessel in a forced-air drying oven at 120°C for 24-72 h to obtain Zr-BDC-PAA or Zr-BDC-PVA membrane.

[0013] 3) The prepared Zr-BDC-PAA or Zr-BDC-PVA membrane is cleaned with anhydrous ethanol until there is no powder accumulation on the membrane surface. Then the membrane is immersed in anhydrous ethanol to remove the residual solvent in the membrane pores. Then it is taken out and placed in a vacuum drying oven at 50-80℃ to dry to obtain Zr-BDC-PAA or Zr-BDC-PVA membrane.

[0014] The molar ratio of zirconium chloride, terephthalic acid, deionized water, and N,N-dimethylformamide is 1:1:1:500.

[0015] In step 2) of the Zr-BDC-PAA or Zr-BDC-PVA preparation method, the molar ratio of zirconium chloride, terephthalic acid, deionized water, N,N-dimethylformamide and polyacrylic acid or polyvinyl alcohol is 1:x:1:500:2(1-x), where 2(1-x) is the molar amount of the polymer monomer, and x = 0.7 to 0.9.

[0016] In step 1) of the Zr-BDC membrane preparation method, the reaction is carried out in a high-temperature drying oven at 120°C for 12–48 hours.

[0017] Preparation method of Zr-BDC-PAA or Zr-BDC-PVA: Step 1) React in a high-temperature drying oven at 120℃ for 12 to 24 hours.

[0018] The Zr-based membrane prepared by this invention has an innovative structure. Specifically, the Zr-BDC-PAA or Zr-BDC-PVA membrane is an organic-inorganic hybrid membrane. The addition of the polymer can adjust the membrane's pore structure, enhance its polarity, improve the size selectivity of the membrane for benzene / cyclohexane separation, promote the intercalation of the Zr-BDC-based membrane, and influence the membrane thickness to a certain extent. By adjusting the membrane growth time, the Zr-BDC membrane grows more densely and continuously, thus exhibiting excellent benzene / cyclohexane separation performance.

[0019] The Zr-based membrane synthesized in this invention can be applied to the separation of benzene / cyclohexane at different temperatures (30–100 °C). Benzene has a slightly smaller molecular dynamics size than cyclohexane, and because the benzene molecule contains π electrons, benzene has a stronger adsorption affinity for polar Zr-BDC-PAA, Zr-BDC-PVA, and Zr-BDC membranes than for cyclohexane. Therefore, benzene preferentially adsorbs and diffuses within the membrane, thereby achieving the separation of benzene / cyclohexane.

[0020] Compared with the prior art, the present invention has the following advantages:

[0021] Zr-BDC-PAA or Zr-BDC-PVA membranes were synthesized using a secondary growth method, increasing the crystal nucleation density on the support. After 12–24 hours of in-situ growth, a uniform Zr-BDC seed layer with high coverage could be formed on the α-alumina support. During the secondary growth process, a polymer was introduced to partially replace the BDC ligands in the reaction with the Zr source, thereby adjusting the pore structure of the Zr-BDC membrane. The introduction of flexible polymer chains made it easier to grow the rigid Zr-BDC membrane denser, thus improving the separation performance of benzene / cyclohexane and the membrane's operational stability. The Zr-BDC membrane synthesized by the in-situ growth method is simple to synthesize, and by adjusting the membrane growth time, good separation of benzene / cyclohexane can be achieved.

[0022] The advantages of this invention are as follows: the secondary growth method increases the nucleation density of Zr-BDC crystals on the support and improves the bonding strength between the Zr-BDC seed layer and the support. The two in-situ growth cycles are relatively short, thus preventing excessive membrane thickness. By introducing long-chain polymers during the secondary growth process to adjust the pore structure of Zr-BDC, the size selectivity of the membrane for benzene is improved, promoting the intergrowth of the Zr-based membrane and enabling the membrane to exhibit both good benzene / cyclohexane separation selectivity and good operational stability. The in-situ growth method is simple to operate, and as the growth time increases to 48 hours, the synthesized Zr-based membrane becomes increasingly dense and continuous, with a gradual increase in benzene selectivity. The effect of temperature on benzene / cyclohexane separation performance was also investigated. At a test temperature of 50°C, the membrane can operate stably for ≥132 hours. The Zr-based membrane prepared using the method described in this invention exhibits good benzene / cyclohexane separation performance at 50°C. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the Zr-BDC-PAA membrane structure of the present invention.

[0024] Figure 2 The images show the FT-IR spectra of Zr-BDC-PVA and Zr-BDC films in Examples 8 and 13 of this invention.

[0025] Figure 3 The benzene / cyclohexane separation performance of the Zr-BDC-PVA membrane in Example 8 of this invention is tested at a temperature of 50°C.

[0026] Figure 4 This is a cross-sectional SEM image of the Zr-BDC-PVA membrane in Example 8 of the present invention.

[0027] Figure 5 The pore size distribution diagrams are shown for Zr-BDC-PVA powder (average pore size 0.61 nm) in Example 9 and Zr-BDC powder (average pore size 0.65 nm) in Example 13 of this invention.

[0028] Figure 6 The image shows the pore size distribution of Zr-BDC powder (left, average pore size 0.62 nm) in Example 11 and Zr-BDC powder (right, average pore size 0.61 nm) in Example 12 of this invention.

[0029] Figure 7 The left figure shows the benzene / cyclohexane vapor permeation performance of the Zr-BDC-PAA membrane in Example 2 of this invention at different temperatures, and the right figure shows the benzene / cyclohexane pervaporation performance of the Zr-BDC-PAA membrane in Example 4 at different temperatures. Detailed Implementation

[0030] The following specific embodiments illustrate the invention in detail. These embodiments primarily involve adjusting the growth time of the Zr-BDC membrane and the ligand concentration of the Zr-BDC-PAA or Zr-BDC-PVA membrane. These embodiments are merely preferred embodiments of the invention, and the claims of this invention are not limited to these limited embodiments.

[0031] Example 1

[0032] Step 1) Weigh 0.0360g of deionized water, 73.09g of N,N-dimethylformamide, 0.3323g of terephthalic acid, and 0.4661g of zirconium chloride into a 100ml beaker using an electronic balance at room temperature. Sonicate the solution until completely dissolved to obtain a clear solution. Fix the α-alumina support wrapped with PTFE tape onto a PTFE support, then place it in a PTFE liner. Pour the sonicated solution into the liner. Place the reactor in a 120℃ high-temperature drying oven for 12 hours. After the reaction, allow the reactor to cool to room temperature. Remove the membrane (at this point, it is a Zr-BDC seed membrane). Clean the membrane surface with anhydrous ethanol to remove any powder buildup, then immerse it in anhydrous ethanol to remove any residual solvent from the membrane pores. Remove the membrane and dry it in a high-temperature drying oven.

[0033] Step 2) Weigh 0.0360g of deionized water, 73.09g of N,N-dimethylformamide, 0.2326g of terephthalic acid (corresponding to x = 0.7), and 0.4661g of zirconium chloride into a 100ml beaker using an electronic balance at room temperature. Sonicate the mixture until completely dissolved to obtain a clear solution 1. Then weigh 0.0865g of polyacrylic acid (molecular weight ~2000), pour the clear solution into a polytetrafluoroethylene (PTFE) liner, and disperse the weighed polyacrylic acid powder in the clear solution using magnetic stirring to obtain solution 2. Place the Zr-BDC seed film (dried and naturally cooled to room temperature in Step 1) wrapped with PTFE tape into the PTFE liner of the reaction vessel, and then place the reaction vessel in a 120℃ high-temperature forced-air drying oven for 24 hours.

[0034] Step 3) After the reaction in Step 2) is complete and the reactor has cooled to room temperature, remove the membrane and wash it with anhydrous ethanol until no powder accumulates on the membrane surface. Then, immerse it in anhydrous ethanol to remove any residual solvent from the membrane pores. Remove the membrane and dry it in a vacuum drying oven at 50–80°C.

[0035] The prepared Zr-BDC-PAA film has a thickness of approximately 0.3–0.5 μm. A schematic diagram of the Zr-BDC-PAA film structure is shown below. Figure 1 As shown, partially replacing the BDC ligand with a macromolecular chain ligand can adjust the membrane's pore structure, thereby improving the membrane's diffusion selectivity for benzene / cyclohexane. The vapor permeation performance of the Zr-BDC-PAA membrane for benzene / cyclohexane was tested at different temperatures and 0 bar (all pressures in this patent are absolute pressures): at 50°C, P... Bz =57.7 GPUs, P Chx =2.94 GPUs, S Bz / Chx =19.6(P) Bz P represents benzene permeability. Chx S represents the permeability of cyclohexane. Bz / Chx (Indicates the selectivity of benzene / cyclohexane); at 75℃, P Bz =73.7 GPUs, P Chx =4.51 GPUs, S Bz / Chx =16.4; at 100℃, P Bz =99.6 GPUs, P Chx =6.74 GPUs, S Bz / Chx =14.8. The pervaporation separation performance of the Zr-BDC-PAA membrane for 5 / 5 / 90 wt.% benzene / cyclohexane / anhydrous ethanol was tested at different temperatures. At 30℃, the total flux J = 0.897 kg·m³. -2 ·h -1 The benzene / cyclohexane separation factor α = 2.19; at 40℃, the total flux J = 0.909 kg·m³. -2 ·h -1 The benzene / cyclohexane separation factor α = 6.74; at 50℃, the total flux J = 1.52 kg·m³. -2 ·h -1 The benzene / cyclohexane separation factor α = 7.61.

[0036] Example 2

[0037] Step 1) Weigh 0.0360g of deionized water, 73.09g of N,N-dimethylformamide, 0.3323g of terephthalic acid, and 0.4661g of zirconium chloride into a 100ml beaker using an electronic balance at room temperature. Sonicate the solution until completely dissolved to obtain a clear solution. Fix the α-alumina support wrapped with PTFE tape onto a PTFE support, then place it in the PTFE liner of the reactor. Pour the sonicated solution into the liner. Place the reactor in a 120℃ high-temperature drying oven for 12 hours. After the reaction, allow the reactor to cool to room temperature. Remove the membrane (at this point, it is a Zr-BDC seed membrane). Clean the membrane surface with anhydrous ethanol to remove any powder buildup, then immerse it in anhydrous ethanol to remove any residual solvent from the membrane pores. Remove the membrane and dry it in a high-temperature drying oven.

[0038] Step 2) Weigh 0.0360g of deionized water, 73.09g of N,N-dimethylformamide, 0.2658g of terephthalic acid (corresponding to x = 0.8), and 0.4661g of zirconium chloride into a 100ml beaker using an electronic balance at room temperature. Sonicate the mixture until completely dissolved to obtain a clear solution 1. Then weigh 0.0576g of polyacrylic acid (molecular weight ~2000), transfer the clear solution to a polytetrafluoroethylene (PTFE) liner, and dissolve and disperse the weighed polyacrylic acid powder in the clear solution using magnetic stirring to obtain solution 2. Wrap the Zr-BDC seed film, which was dried and naturally cooled to room temperature in Step 1), with PTFE tape, and then place it in the PTFE liner of the reactor. Place the reactor in a 120℃ high-temperature drying oven for 24 hours.

[0039] Step 3) After the reaction in Step 2) is complete and the reactor has cooled to room temperature, remove the membrane and wash it with anhydrous ethanol until no powder accumulates on the membrane surface. Then, immerse it in anhydrous ethanol to remove any residual solvent from the membrane pores. Remove the membrane and dry it in a vacuum drying oven at 50–80°C.

[0040] The prepared Zr-BDC-PAA membrane has a thickness of approximately 0.5–0.9 μm. The vapor permeation performance of the Zr-BDC-PAA membrane against benzene / cyclohexane was tested at different temperatures and 0 bar (all pressures in this patent refer to absolute pressure). Figure 7 (As shown in the left figure): At 50℃, P Bz =96.9 GPUs, P Chx =3.21 GPUs, S Bz / Chx =30.2; at 75℃, P Bz =124 GPUs, P Chx =4.61 GPUs, S Bz / Chx =26.9; at 100℃, P Bz =135 GPU, P Chx =8.82 GPUs, SBz / Chx =15.3. With increasing temperature, the permeability of benzene and cyclohexane in the membrane increases, while the benzene / cyclohexane selectivity decreases. The pervaporation separation performance of the Zr-BDC-PAA membrane for 5 / 5 / 90 wt.% benzene / cyclohexane / anhydrous ethanol was tested at different temperatures. At 30℃, the total flux J = 1.44 kg·m³. -2 ·h -1 The benzene / cyclohexane separation factor α = 5.63; at 40℃, the total flux J = 3.41 kg·m³. -2 ·h -1 The benzene / cyclohexane separation factor α = 10.8; at 50℃, the total flux J = 2.02 kg·m³. -2 ·h -1 The benzene / cyclohexane separation factor α = 4.82.

[0041] Example 3

[0042] Step 1) Weigh 0.0360g of deionized water, 73.09g of N,N-dimethylformamide, 0.3323g of terephthalic acid, and 0.4661g of zirconium chloride into a 100ml beaker using an electronic balance at room temperature. Sonicate the solution until completely dissolved to obtain a clear solution. Fix the α-alumina support wrapped with PTFE tape onto a PTFE support, then place it in the PTFE liner of the reactor. Pour the sonicated solution into the liner. Place the reactor in a 120℃ high-temperature drying oven for 12 hours. After the reaction, allow the reactor to cool to room temperature. Remove the membrane (at this point, it is a Zr-BDC seed membrane). Clean the membrane surface with anhydrous ethanol to remove any powder buildup, then immerse it in anhydrous ethanol to remove any residual solvent from the membrane pores. Remove the membrane and dry it in a high-temperature drying oven.

[0043] Step 2) Weigh 0.0360g of deionized water, 73.09g of N,N-dimethylformamide, 0.2991g of terephthalic acid (corresponding to x = 0.9), and 0.4661g of zirconium chloride into a 100ml beaker using an electronic balance at room temperature. Sonicate the mixture until completely dissolved to obtain a clear solution 1. Then weigh 0.0288g of polyacrylic acid (molecular weight ~2000), transfer the clear solution to a polytetrafluoroethylene (PTFE) liner, and disperse the weighed polyacrylic acid powder in the clear solution using magnetic stirring to obtain solution 2. Wrap the Zr-BDC seed film, which was dried and naturally cooled to room temperature in Step 1), with PTFE tape, then place it in the PTFE liner of the reactor, and then place the reactor in a 120℃ high-temperature forced-air drying oven for 24 hours.

[0044] Step 3) After the reaction in Step 2) is complete and the reactor has cooled to room temperature, remove the membrane and wash it with anhydrous ethanol until no powder accumulates on the membrane surface. Then, immerse it in anhydrous ethanol to remove any residual solvent from the membrane pores. Remove the membrane and dry it in a vacuum drying oven at 50–80°C.

[0045] The prepared Zr-BDC-PAA membrane has a thickness of approximately 0.7–1.4 μm. The vapor permeation performance of the Zr-BDC-PAA membrane for benzene / cyclohexane was tested at different temperatures and 0 bar (all pressures in this patent are absolute pressures): at 50°C, P... Bz =63.3 GPUs, P Chx =2.87 GPUs, S Bz / Chx =22.0; at 75℃, P Bz =127 GPUs, P Chx =6.17 GPUs, S Bz / Chx =20.6; at 100℃, P Bz =143 GPUs, P Chx =8.81 GPUs, S Bz / Chx =16.3. The pervaporation separation performance of the Zr-BDC-PAA membrane for 5 / 5 / 90 wt.% benzene / cyclohexane / anhydrous ethanol was tested at different temperatures. At 30℃, the total flux J = 1.24 kg·m³. -2 ·h -1 The benzene / cyclohexane separation factor α = 11.4; at 40℃, the total flux J = 1.47 kg·m³. -2 ·h -1 The benzene / cyclohexane separation factor α = 16.4; at 50℃, the total flux J = 3.91 kg·m³. -2 ·h -1 The benzene / cyclohexane separation factor α = 7.29.

[0046] Example 4

[0047] Step 1) Weigh 0.0360g of deionized water, 73.09g of N,N-dimethylformamide, 0.3323g of terephthalic acid, and 0.4661g of zirconium chloride into a 100ml beaker using an electronic balance at room temperature. Sonicate the solution until completely dissolved to obtain a clear solution. Fix the α-alumina support wrapped with PTFE tape onto a PTFE support, then place it in a PTFE liner. Pour the sonicated solution into the liner. Place the reactor in a 120℃ high-temperature drying oven for 24 hours. After the reaction, allow the reactor to cool to room temperature. Remove the membrane (at this point, it is a Zr-BDC seed membrane). Clean the membrane surface with anhydrous ethanol to remove any accumulated powder, then immerse it in anhydrous ethanol to remove any residual solvent from the membrane pores. Remove the membrane and dry it in a high-temperature drying oven.

[0048] Step 2) Weigh 0.0360g of deionized water, 73.09g of N,N-dimethylformamide, 0.2326g of terephthalic acid (corresponding to x = 0.7), and 0.4661g of zirconium chloride into a 100ml beaker using an electronic balance at room temperature. Sonicate the mixture until completely dissolved to obtain a clear solution 1. Then weigh 0.0865g of polyacrylic acid (molecular weight ~2000), pour the clear solution into a polytetrafluoroethylene (PTFE) liner, and disperse the weighed polyacrylic acid powder in the clear solution using magnetic stirring to obtain solution 2. Place the Zr-BDC seed film (dried and naturally cooled to room temperature in Step 1) wrapped with PTFE tape into the PTFE liner of the reaction vessel, and then place the reaction vessel in a 120℃ high-temperature forced-air drying oven for 72 hours.

[0049] Step 3) After the reaction in Step 2) is complete and the reactor has cooled to room temperature, remove the membrane and wash it with anhydrous ethanol until no powder accumulates on the membrane surface. Then, immerse it in anhydrous ethanol to remove any residual solvent from the membrane pores. Remove the membrane and dry it in a vacuum drying oven at 50–80°C.

[0050] The prepared Zr-BDC-PAA membrane has a thickness of approximately 0.6–1.5 μm. The vapor permeation performance of the Zr-BDC-PAA membrane for benzene / cyclohexane was tested at different temperatures and 1.0 bar (all pressures in this patent are absolute pressures): at 50°C, P... Bz =107 GPUs, P Chx =30.9 GPUs, S Bz / Chx =3.48(P) Bz P represents benzene permeability. Chx S represents the permeability of cyclohexane. Bz / Chx (Indicates the selectivity of benzene / cyclohexane); at 75℃, P Bz =134 GPUs, P Chx =29.9 GPUs, S Bz / Chx =4.5; at 100℃, P Bz =162 GPUs, P Chx =38.4 GPUs, S Bz / Chx =4.23. The pervaporation separation performance of the Zr-BDC-PAA membrane for 5 / 5 / 90 wt.% benzene / cyclohexane / anhydrous ethanol was tested at different temperatures (e.g., Figure 7 (As shown in the right figure), at 30℃, the total flux J = 1.26 kg·m -2 ·h -1 The benzene / cyclohexane separation factor α = 3.24; at 40℃, the total flux J = 1.66 kg·m³. -2 ·h -1 The benzene / cyclohexane separation factor α = 5.00; at 50℃, the total flux J = 2.11 kg·m³. -2 ·h -1The benzene / cyclohexane separation factor α = 12.1. As the temperature gradually increases to 50℃, both the membrane flux and the separation factor increase. Within the tested temperature range, 50℃ is the optimal test temperature.

[0051] Example 5

[0052] Step 1) Weigh 0.0360g of deionized water, 73.09g of N,N-dimethylformamide, 0.3323g of terephthalic acid, and 0.4661g of zirconium chloride into a 100ml beaker using an electronic balance at room temperature. Sonicate the solution until completely dissolved to obtain a clear solution. Fix the α-alumina support wrapped with PTFE tape onto a PTFE support, then place it in the PTFE liner of the reactor. Pour the sonicated solution into the liner. Place the reactor in a 120℃ high-temperature drying oven for 18 hours. After the reaction, allow the reactor to cool to room temperature. Remove the membrane (at this point, it is a Zr-BDC seed membrane). Clean the membrane surface with anhydrous ethanol to remove any powder buildup, then immerse it in anhydrous ethanol to remove any residual solvent from the membrane pores. Remove the membrane and dry it in a high-temperature drying oven.

[0053] Step 2) Weigh 0.0360g of deionized water, 73.09g of N,N-dimethylformamide, 0.2658g of terephthalic acid (corresponding to x = 0.8), and 0.4661g of zirconium chloride into a 100ml beaker using an electronic balance at room temperature. Sonicate the mixture until completely dissolved to obtain a clear solution 1. Then weigh 0.0576g of polyacrylic acid (molecular weight ~2000), transfer the clear solution to a polytetrafluoroethylene (PTFE) liner, and dissolve and disperse the weighed polyacrylic acid powder in the clear solution using magnetic stirring to obtain solution 2. Wrap the Zr-BDC seed film, which was dried and naturally cooled to room temperature in Step 1), with PTFE tape, and then place it in the PTFE liner of the reactor. Place the reactor in a 120℃ high-temperature drying oven for 48 hours.

[0054] Step 3) After the reaction in Step 2) is complete and the reactor has cooled to room temperature, remove the membrane and clean it with anhydrous ethanol until no powder accumulates on the surface. Then, immerse it in anhydrous ethanol to remove any residual solvent from the membrane pores. Remove the membrane and dry it in a vacuum drying oven at 50–80°C.

[0055] The vapor permeation performance of the Zr-BDC-PAA membrane under benzene / cyclohexane conditions at 50°C and 0 bar (all pressures in this patent are absolute pressures) was tested: P Bz =51.4 GPUs, P Chx =2.04 GPUs, S Bz / Chx =25.3.

[0056] Example 6

[0057] Step 1) Weigh 0.0360g of deionized water, 73.09g of N,N-dimethylformamide, 0.3323g of terephthalic acid, and 0.4661g of zirconium chloride into a 100ml beaker using an electronic balance at room temperature. Sonicate the solution until completely dissolved to obtain a clear solution. Fix the α-alumina support wrapped with PTFE tape onto a PTFE support, then place it in the PTFE liner of the reactor. Pour the sonicated solution into the liner. Place the reactor in a 120℃ high-temperature drying oven for 24 hours. After the reaction, allow the reactor to cool to room temperature. Remove the membrane (at this point, it is a Zr-BDC seed membrane). Clean the membrane surface with anhydrous ethanol to remove any powder buildup, then immerse it in anhydrous ethanol to remove any residual solvent from the membrane pores. Remove the membrane and dry it in a high-temperature drying oven.

[0058] Step 2) Weigh 0.0360g of deionized water, 73.09g of N,N-dimethylformamide, 0.2658g of terephthalic acid (corresponding to x = 0.8), and 0.4661g of zirconium chloride into a 100ml beaker using an electronic balance at room temperature. Sonicate the mixture until completely dissolved to obtain clear solution 1. Then weigh 0.0576g of polyacrylic acid (molecular weight ~450,000), transfer the clear solution to a polytetrafluoroethylene (PTFE) liner, and dissolve and disperse the weighed polyacrylic acid powder in the clear solution using magnetic stirring to obtain solution 2. Wrap the Zr-BDC seed film, which was dried and naturally cooled to room temperature in Step 1), with PTFE tape, and then place it in the PTFE liner of the reactor. Place the reactor in a 120℃ high-temperature drying oven for 72 hours.

[0059] Step 3) After the reaction in Step 2) is complete and the reactor has cooled to room temperature, remove the membrane and clean it with anhydrous ethanol until no powder accumulates on the surface. Then, immerse it in anhydrous ethanol to remove any residual solvent from the membrane pores. Remove the membrane and dry it in a vacuum drying oven at 50–80°C.

[0060] The prepared Zr-BDC-PAA membrane has a thickness of approximately 1.6–2.9 μm. The vapor permeation performance of the Zr-BDC-PAA membrane for benzene / cyclohexane was tested at different temperatures and 1.0 bar (all pressures in this patent are absolute pressures): at 50°C, P... Bz =135 GPU, P Chx =115 GPUs, S Bz / Chx =1.17; at 75℃, P Bz =102 GPUs, P Chx =58.0 GPU, S Bz / Chx =1.76; at 100℃, P Bz =141 GPUs, P Chx =89.7 GPUs, S Bz / Chx=1.57. The pervaporation separation performance of the Zr-BDC-PAA membrane at 30℃ for 1 / 1 / 98wt.% benzene / cyclohexane / anhydrous ethanol was tested, with a total flux J = 0.522 kg·m³. -2 ·h -1 The benzene / cyclohexane separation factor α = 2.12;

[0061] Example 7

[0062] Step 1) Weigh 0.0360g of deionized water, 73.09g of N,N-dimethylformamide, 0.3323g of terephthalic acid, and 0.4661g of zirconium chloride into a 100ml beaker using an electronic balance at room temperature. Sonicate the solution until completely dissolved to obtain a clear solution. Fix the α-alumina support wrapped with PTFE tape onto a PTFE support, then place it in the PTFE liner of the reactor. Pour the sonicated solution into the liner. Place the reactor in a 120℃ high-temperature drying oven for 12 hours. After the reaction, allow the reactor to cool to room temperature. Remove the membrane (at this point, it is a Zr-BDC seed membrane). Clean the membrane surface with anhydrous ethanol to remove any powder buildup, then immerse it in anhydrous ethanol to remove any residual solvent from the membrane pores. Remove the membrane and dry it in a high-temperature drying oven.

[0063] Step 2) Weigh 0.0360g of deionized water, 73.1120g of 0.0723wt.% N,N-dimethylformamide solution containing polyvinyl alcohol, 0.0309g of N,N-dimethylformamide, 0.2326g of terephthalic acid (corresponding to x = 0.7), and 0.4661g of zirconium chloride into a 100ml beaker using an electronic balance at room temperature. Sonicate the solution until completely dissolved to obtain a clear solution. Transfer the Zr-BDC seed film (dried and naturally cooled to room temperature in Step 1) wrapped with PTFE tape and the clear solution into a PTFE liner. Then, place the reactor in a 120℃ high-temperature drying oven for 24 hours.

[0064] Step 3) After the reaction in Step 2) is complete and the reactor has cooled to room temperature, remove the membrane and wash it with anhydrous ethanol until no powder accumulates on the membrane surface. Then, immerse it in anhydrous ethanol to remove any residual solvent from the membrane pores. Remove the membrane and dry it in a vacuum drying oven at 50–80°C.

[0065] The prepared Zr-BDC-PVA membrane has a thickness of approximately 1.5–1.9 μm. The vapor permeation performance of the Zr-BDC-PVA membrane against benzene / cyclohexane was tested at 50 °C and 0 bar (all pressures in this patent are absolute pressures): P Bz =95.2 GPU, P Chx =2.79 GPUs, S Bz / Chx =34.2.

[0066] Example 8

[0067] Step 1) Weigh 0.0360g of deionized water, 73.09g of N,N-dimethylformamide, 0.3323g of terephthalic acid, and 0.4661g of zirconium chloride into a 100ml beaker using an electronic balance at room temperature. Sonicate the solution until completely dissolved to obtain a clear solution. Fix the α-alumina support wrapped with PTFE tape onto a PTFE support, then place it in the PTFE liner of the reactor. Pour the sonicated solution into the liner. Place the reactor in a 120℃ high-temperature drying oven for 12 hours. After the reaction, allow the reactor to cool to room temperature. Remove the membrane (at this point, it is a Zr-BDC seed membrane). Clean the membrane surface with anhydrous ethanol to remove any powder buildup, then immerse it in anhydrous ethanol to remove any residual solvent from the membrane pores. Remove the membrane and dry it in a high-temperature drying oven.

[0068] Step 2) Weigh 0.0360 g of deionized water, 48.7414 g of 0.0723 wt.% N,N-dimethylformamide solution containing polyvinyl alcohol, 24.3838 g of N,N-dimethylformamide, 0.2658 g of terephthalic acid (corresponding to x = 0.8), and 0.4661 g of zirconium chloride into a 100 ml beaker using an electronic balance at room temperature. Sonicate the solution until completely dissolved to obtain a clear solution. Transfer the Zr-BDC seed film (dried and naturally cooled to room temperature in Step 1) wrapped with PTFE tape and the clear solution into a PTFE liner. Then, place the reactor in a 120°C high-temperature drying oven and react for 24 h.

[0069] Step 3) After the reaction in Step 2) is complete and the reactor has cooled to room temperature, remove the membrane and wash it with anhydrous ethanol until no powder accumulates on the membrane surface. Then, immerse it in anhydrous ethanol to remove any residual solvent from the membrane pores. Remove the membrane and dry it in a vacuum drying oven at 50–80°C.

[0070] The prepared Zr-BDC-PVA film has a thickness of approximately 0.6–1.1 μm (SEM images of the film cross-section are shown in Figure 1). Figure 4 (As shown). The infrared spectra of the Zr-BDC-PVA film and the Zr-BDC film in Example 13 are as follows. Figure 2 As shown, 743cm -1 The peak at this point corresponds to the bending vibration after mixing CH and OH with Zr-O. The peak intensity of the Zr-BDC-PVA membrane is significantly increased compared to the Zr-BDC membrane, confirming the successful introduction of polyvinyl alcohol (PVA). The vapor permeation performance of the Zr-BDC-PVA membrane at 50℃ and 0 bar for benzene / cyclohexane was tested: P Bz =111 GPUs, P Chx =3.12 GPUs, S Bz / Chx=35.4, and the membrane can operate stably under these conditions for ≥132h (e.g. Figure 3 (As shown); at 75℃, P Bz =248 GPUs, P Chx =45.3 GPUs, S Bz / Chx =5.53.

[0071] Example 9

[0072] Step 1) Weigh 0.0360g of deionized water, 73.09g of N,N-dimethylformamide, 0.3323g of terephthalic acid, and 0.4661g of zirconium chloride into a 100ml beaker using an electronic balance at room temperature. Sonicate the solution until completely dissolved to obtain a clear solution. Fix the α-alumina support wrapped with PTFE tape onto a PTFE support, then place it in the PTFE liner of the reactor. Pour the sonicated solution into the liner. Place the reactor in a 120℃ high-temperature drying oven for 12 hours. After the reaction, allow the reactor to cool to room temperature. Remove the membrane (at this point, it is a Zr-BDC seed membrane). Clean the membrane surface with anhydrous ethanol to remove any powder buildup, then immerse it in anhydrous ethanol to remove any residual solvent from the membrane pores. Remove the membrane and dry it in a high-temperature drying oven.

[0073] Step 2) Weigh 0.0360g of deionized water, 24.3707g of 0.0723wt.% N,N-dimethylformamide solution containing polyvinyl alcohol, 48.7369g of N,N-dimethylformamide, 0.2991g of terephthalic acid (corresponding to x = 0.9), and 0.4661g of zirconium chloride into a 100ml beaker using an electronic balance at room temperature. Sonicate the solution until completely dissolved to obtain a clear solution. Transfer the Zr-BDC seed film (dried and naturally cooled to room temperature in Step 1) wrapped with PTFE tape and the clear solution into a PTFE liner. Then, place the reactor in a 120℃ high-temperature drying oven for 24 hours.

[0074] Step 3) After the reaction in Step 2) is complete and the reactor has cooled to room temperature, remove the membrane and wash it with anhydrous ethanol until no powder accumulates on the membrane surface. Then, immerse it in anhydrous ethanol to remove any residual solvent from the membrane pores. Remove the membrane and dry it in a vacuum drying oven at 50–80°C.

[0075] The prepared Zr-BDC-PVA film has a thickness of approximately 1.1–1.7 μm. The particle size distributions of the Zr-BDC-PVA powder (average pore size 0.61 nm) and the Zr-BDC powder (average pore size 0.65 nm) in Example 13 are as follows: Figure 5As shown, the introduction of polyvinyl alcohol (PVA) reduces the pore size of Zr-BDC, thereby improving the diffusion selectivity of the membrane for benzene / cyclohexane. The vapor permeation performance of the Zr-BDC-PVA membrane for benzene / cyclohexane was tested at 50°C and 0 bar: P Bz =40.5 GPUs, P Chx =2.56 GPUs, S Bz / Chx =15.8; at 75℃, P Bz =196 GPUs, P Chx =14.0 GPU, S Bz / Chx =14.0.

[0076] Example 10

[0077] Step 1) Weigh 0.0360g of deionized water, 73.09g of N,N-dimethylformamide, 0.3323g of terephthalic acid, and 0.4661g of zirconium chloride into a 100ml beaker using an electronic balance at room temperature. Sonicate the solution until completely dissolved to obtain a clear solution. Fix the α-alumina support wrapped with PTFE tape onto a PTFE support, then place it in the PTFE liner of the reactor. Pour the sonicated solution into the liner. Place the reactor in a 120℃ high-temperature drying oven for 18 hours. After the reaction, allow the reactor to cool to room temperature. Remove the membrane (at this point, it is a Zr-BDC seed membrane). Clean the membrane surface with anhydrous ethanol to remove any powder buildup, then immerse it in anhydrous ethanol to remove any residual solvent from the membrane pores. Remove the membrane and dry it in a high-temperature drying oven.

[0078] Step 2) Weigh 0.0360 g of deionized water, 48.7414 g of 0.0723 wt.% N,N-dimethylformamide solution containing polyvinyl alcohol, 24.3838 g of N,N-dimethylformamide, 0.2658 g of terephthalic acid (corresponding to x = 0.8), and 0.4661 g of zirconium chloride into a 100 ml beaker using an electronic balance at room temperature. Sonicate the solution until completely dissolved to obtain a clear solution. Transfer the Zr-BDC seed film (dried and naturally cooled to room temperature in Step 1) wrapped with PTFE tape and the clear solution into a PTFE liner. Then, place the reactor in a 120°C high-temperature drying oven and react for 48 h.

[0079] Step 3) After the reaction in Step 2) is complete and the reactor has cooled to room temperature, remove the membrane and wash it with anhydrous ethanol until no powder accumulates on the membrane surface. Then, immerse it in anhydrous ethanol to remove any residual solvent from the membrane pores. Remove the membrane and dry it in a vacuum drying oven at 50–80°C.

[0080] The vapor permeation performance of the Zr-BDC-PVA membrane at 50°C and 0 bar was tested for benzene / cyclohexane: P Bz=314 GPUs, P Chx =293 GPUs, S Bz / Chx =1.07.

[0081] Example 11

[0082] Step 1) Weigh 0.0360g of deionized water, 73.09g of N,N-dimethylformamide, 0.3323g of terephthalic acid, and 0.4661g of zirconium chloride into a 100ml beaker using an electronic balance at room temperature. Sonicate the solution until completely dissolved to obtain a clear solution. Fix the α-alumina support wrapped with PTFE tape onto a PTFE support, then place it in the PTFE liner of the reactor. Pour the sonicated solution into the liner. Place the reactor in a 120℃ high-temperature drying oven for 12 hours.

[0083] Step 2) After the reaction is complete and the reactor has cooled to room temperature, remove the membrane and wash it with anhydrous ethanol until no powder accumulates on the membrane surface. Then, immerse the membrane in anhydrous ethanol to remove any residual solvent from the membrane pores. Remove the membrane and dry it in a vacuum drying oven at 50–80°C.

[0084] The prepared Zr-BDC film thickness was approximately 0.1–0.4 μm. The particle size distribution of the Zr-BDC powder (average particle size 0.62 nm) is shown in the figure. Figure 6 The left figure shows the vapor permeation performance of the Zr-BDC membrane at 50°C and 0 bar (all pressures in this patent are absolute pressures) for benzene / cyclohexane: P Bz =609 GPUs, P Chx =435 GPUs, S Bz / Chx =1.40.

[0085] Example 12

[0086] Step 1) Weigh 0.0360g of deionized water, 73.09g of N,N-dimethylformamide, 0.3323g of terephthalic acid, and 0.4661g of zirconium chloride into a 100ml beaker using an electronic balance at room temperature. Sonicate the solution until completely dissolved to obtain a clear solution. Fix the α-alumina support wrapped with PTFE tape onto a PTFE support, then place it in the PTFE liner of the reactor. Pour the sonicated solution into the liner. Place the reactor in a 120℃ high-temperature drying oven for 36 hours.

[0087] Step 2) After the reaction is complete and the reactor has cooled to room temperature, remove the membrane and wash it with anhydrous ethanol until no powder accumulates on the membrane surface. Then, immerse the membrane in anhydrous ethanol to remove any residual solvent from the membrane pores. Remove the membrane and dry it in a vacuum drying oven at 50–80°C.

[0088] The prepared Zr-BDC film thickness was approximately 0.4–0.7 μm. The particle size distribution of the Zr-BDC powder (average particle size 0.61 nm) is shown in the figure. Figure 6 The right figure shows that as the growth time is extended from 12h to 36h, the membrane becomes increasingly dense. The vapor permeation performance of the Zr-BDC membrane at 50℃ and 0 bar (all pressures in this patent are absolute pressures) for benzene / cyclohexane was tested: P Bz =53.8 GPUs, P Chx =5.60 GPU, S Bz / Chx =9.61.

[0089] Example 13

[0090] Step 1) Weigh 0.0360g of deionized water, 73.09g of N,N-dimethylformamide, 0.3323g of terephthalic acid, and 0.4661g of zirconium chloride into a 100ml beaker using an electronic balance at room temperature. Sonicate the solution until completely dissolved to obtain a clear solution. Fix the α-alumina support wrapped with PTFE tape onto a PTFE support, then place it in the PTFE liner of the reactor. Pour the sonicated solution into the liner. Place the reactor in a 120℃ high-temperature drying oven for 48 hours.

[0091] Step 2) After the reaction is complete, wait for the reaction vessel to cool to room temperature, remove the membrane, wash it with anhydrous ethanol until there is no powder accumulation on the membrane surface, and then immerse it in anhydrous ethanol to remove residual solvent in the membrane pores. Remove the membrane and dry it in a vacuum drying oven at 50-80℃.

[0092] The prepared Zr-BDC membrane has a thickness of approximately 0.9–1.3 μm. The vapor permeation performance of the Zr-BDC membrane against benzene / cyclohexane was tested at 50 °C and 0 bar (all pressures in this patent are absolute pressures): P Bz =148 GPUs, P Chx =11.5 GPUs, S Bz / Chx =12.9.

[0093] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the requirements of the present invention should be included within the protection scope of the present invention.

[0094] The technical solutions disclosed and proposed in this invention can be implemented by those skilled in the art by appropriately modifying the conditions and routes, etc. Although the methods and preparation techniques of this invention have been described through preferred embodiments, those skilled in the art can obviously modify or recombine the methods and technical routes described herein without departing from the content, spirit, and scope of this invention to achieve the final preparation technique. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art and are considered to be included within the spirit, scope, and content of this invention.

Claims

1. A method for preparing a Zr-based membrane for benzene / cyclohexane separation, characterized in that, Zr-based films include Zr-BDC-PAA or Zr-BDC-PVA films: 1) The α-alumina support was placed in a reaction vessel containing a mixed solution of zirconium chloride, terephthalic acid, deionized water and N,N-dimethylformamide. The reaction vessel was then placed in a high-temperature drying oven at 120°C for more than 12 hours to obtain a Zr-BDC membrane. 2) The obtained Zr-BDC membrane is placed in a reaction vessel containing zirconium chloride, terephthalic acid, deionized water, N,N-dimethylformamide and polyacrylic acid or polyvinyl alcohol. The reaction vessel is then placed in a forced-air drying oven at 120°C for 24~72 h to obtain Zr-BDC-PAA or Zr-BDC-PVA membrane. 3) Use anhydrous ethanol to clean the prepared Zr-BDC-PAA or Zr-BDC-PVA membrane until there is no powder accumulation on the membrane surface. Then immerse the membrane in anhydrous ethanol to remove the residual solvent in the membrane pores. Then take it out and place it in a vacuum drying oven at 50~80℃ to dry it to obtain Zr-BDC-PAA or Zr-BDC-PVA membrane.

2. The preparation method according to claim 1, characterized in that, In step 1), the molar ratio of zirconium chloride, terephthalic acid, deionized water, and N,N-dimethylformamide is 1:1:1:

500.

3. The preparation method according to claim 1, characterized in that, In step 2), the molar ratio of zirconium chloride, terephthalic acid, deionized water, N,N-dimethylformamide and polyacrylic acid or polyvinyl alcohol is 1:x:1:500:2(1-x), where 2(1-x) is the molar amount of the polymer monomer, and x = 0.7~0.

9.

4. The preparation method according to claim 1, characterized in that, In step 1), react in a high-temperature drying oven at 120°C for 12 to 48 hours.

5. The preparation method according to claim 1, characterized in that, Step 1) React in a high-temperature drying oven at 120℃ for 12~24 hours.

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