Preparation method of zr-bdc membrane and application of the organic matter separation

Abstract

The application provides a preparation method of Zr-BDC film and application of the Zr-BDC film in separation of organic matters. The application directly uses zirconium propoxide as the only zirconium source in a mother liquor, and continuously synthesizes Zr-BDC film through a solvothermal method; the content of the metal source in the mother liquor is extremely low, so that the film thickness is still thin after three times of solvothermal growth, and the preparation of a high-flux film is facilitated. The application uses a ligand / metal molar ratio of up to 20, and provides application of the Zr-BDC film with less defect sites in separation of MeOH / MTBE. The Zr-BDC film prepared by the application exhibits optimal separation performance of MeOH / MTBE, and when 5wt.% MeOH / MTBE is separated at 40 DEG C, the film flux can reach 5.68kg·m ‑2 ·h ‑1 -1h-1, the separation factor is up to 25802, and the operation stability is greater than 5 days.

Description

Technical Field

[0001] This invention relates to the field of membrane preparation technology, and more particularly to a novel method for preparing zirconium-based phthalic acid (Zr-BDC) membranes, suitable for separating organic-organic mixtures using pervaporation membrane technology. Specifically, it relates to a method for preparing Zr-BDC membranes and their application in organic matter separation. Background Technology

[0002] Methyl tert-butyl ether (MTBE) is an ideal blending component for producing unleaded, high-octane, oxygenated gasoline and is an important chemical raw material. MTBE production mainly involves the reaction of isobutylene with methanol (MeOH). Excess methanol is usually added to increase the reaction conversion rate, which inevitably leads to separation problems. At atmospheric pressure, 14.3 wt.% methanol can form an azeotrope with MTBE at 51°C, further complicating its separation.

[0003] Pervaporation is an emerging membrane technology involving phase change, offering advantages such as simple operating conditions, small footprint, and high separation efficiency. The principle of pervaporation is based on the vapor pressure difference across the membrane, relying on the difference in adsorption and diffusion rates of the two components within the membrane material to achieve separation. Its separation effect is not limited by the gas-liquid equilibrium of the components, making it highly suitable for separating near-boiling and azeotropic substances. Pervaporation technology is widely used in the dehydration of organic solvents, the removal of organic matter from water, and the separation of organic mixtures. The preparation of alcohol-ether separation membranes is a topic of great interest to many researchers.

[0004] MeOH / MTBE separation membrane materials include organic membranes, inorganic membranes, and organic / inorganic hybrid membranes. Organic membranes have lower preparation costs but are prone to swelling, have poor stability, and struggle to overcome the trade-off between permeability and selectivity. Currently, commercially available polymer membranes (PERVAP 2256) are used for separating this system, but their performance is not high (flux < 1 kg·m³). -2 ·h -1 (Selectivity < 200). Although inorganic membranes offer excellent separation performance and good stability, they are expensive and their preparation process is relatively complex. Therefore, developing a membrane that combines the advantages of both organic and inorganic membranes is currently a hot research topic in the field of membrane technology. Zr-BDC, through the construction of a highly connected coordination structure, is a highly stable organic / inorganic hybrid membrane material with great application potential in the membrane separation of organic mixtures.

[0005] A typical formulation for preparing Zr-BDC membranes uses zirconium chloride as the metal source. However, zirconium chloride is unstable at room temperature and pressure, readily absorbs moisture, has strong hygroscopic properties, is difficult to store, and can easily cause safety issues. Furthermore, it generates volatile organic compounds such as hydrogen chloride (HCl) during the membrane fabrication process. Therefore, there is an urgent need to explore methods for preparing thinner, continuous, and defect-free Zr-BDC membranes using other zirconium sources. Summary of the Invention

[0006] To address the problems in existing technologies, this invention proposes a novel method for preparing Zr-BDC membranes. This invention controls the metal source content in the solution to be extremely low (1:12600), resulting in a relatively thin membrane thickness (~500 nm) even after three solvothermal growth cycles. This not only replenishes the nutrients required for membrane formation but also allows for independent control of nucleation and growth, regulating the membrane structure and improving membrane reproducibility. Furthermore, the high stability and suitable pore size of the Zr-BDC membrane facilitate the separation of methanol / methyl tert-butyl ether (MeOH / MTBE).

[0007] To achieve the above objectives, the present invention provides a method for preparing a Zr-BDC membrane; the Zr-BDC membrane is prepared by a three-stage solvothermal method, comprising the following steps:

[0008] A method for preparing a Zr-BDC membrane; the Zr-BDC membrane is prepared by a three-stage solvothermal method, including the following steps:

[0009] 1) Disperse the organic ligand and zirconium propoxide solution in a mixed solvent of methanol, N,N-dimethylformamide and acetic acid, and sonicate at room temperature to prepare the synthesis solution;

[0010] 2) Place the porous α-Al2O3 support in the reactor and pour in the synthesis solution prepared in step 1). React at 110-130℃ for 10-12h. Rinse the surface of the membrane with ethanol to remove the scattered particles, immerse the membrane in ethanol, and then dry it naturally at room temperature to obtain the seed layer membrane.

[0011] 3) Prepare the same synthesis solution as in step 1); place the seed layer film obtained in step 2) in the reaction vessel and pour in the prepared synthesis solution, react at 110-130℃ for 48±2h, rinse the scattered particles on the film surface with ethanol, immerse the film in ethanol, and then dry it naturally at room temperature to obtain the film grown by secondary solvothermal growth.

[0012] 4) Prepare the same solution as in step 1); place the membrane obtained in step 3) after secondary solvothermal growth in a reaction vessel and pour in the prepared synthesis solution. React at 110-130℃ for 20-30 h. Rinse the surface of the membrane with ethanol to remove scattered particles, and soak the membrane in ethanol overnight. Then, allow it to dry naturally at room temperature to obtain the Zr-BDC membrane after tertiary solvothermal growth.

[0013] The preferred organic ligand in step 1) is terephthalic acid or aminoterephthalic acid.

[0014] The preferred molar ratio of the organic ligand to zirconium propoxide in step 1) is 2:0.2 to 0.1.

[0015] The preferred molar ratio of the mixed solvents methanol, N,N-dimethylformamide and acetic acid in step 1) is 7.6:4:1.

[0016] The preferred molar ratio of acetic acid and zirconium propoxide in step 1) is 100:0.2 to 0.1.

[0017] Preferred steps 2) or 3) involve natural drying at room temperature for 6–24 hours.

[0018] Preferred step 4) Dry naturally at room temperature for 24-48 hours.

[0019] The Zr-BDC membrane prepared by the method of the present invention is used for the separation of methanol / methyl tert-butyl ether.

[0020] The specific explanation is as follows:

[0021] This invention specifically emphasizes that the same solution needs to be prepared each time; this is to avoid insufficient nutrients in the solution during the film-forming process. In step 1), some of the solution is prepared to be distributed to the subsequent long film. It seems simple, but during this waiting period, the solution metal and ligand are also reacting slowly! Therefore, we found that this repeated process is very necessary.

[0022] The synthesis solution of this invention has an organic ligand / Zr molar ratio as high as 20, which provides a Zr-BDC membrane with fewer defect sites for the separation of MeOH / MTBE.

[0023] Compared with the prior art, the present invention has the following advantages and technical effects:

[0024] Conventional zirconium sources, such as zirconium chloride (ZrCl4), are highly hygroscopic, making it difficult to control crystal nucleation and growth. Furthermore, they generate volatile organic compounds during the film-forming process. Existing preparation methods all have certain problems, and there is an urgent need for a new method for preparing Zr-BDC films. This invention successfully prepared a continuous and defect-free Zr-BDC film by directly using zirconium propoxide as the sole metal source.

[0025] This invention controls the metal source content in the mother liquor to be extremely low (1:12600), resulting in a relatively thin film thickness (~500 nm) even after three solvothermal growth cycles, which is beneficial for the preparation of high-throughput membranes. The ligand / metal molar ratio used in this invention is as high as 20, resulting in fewer defect sites in the Zr-BDC membrane, which is beneficial for the preparation of highly selective membranes.

[0026] The organic ligand / Zr molar ratio used in this invention is as high as 20, providing Zr-BDC membranes with fewer defect sites for the separation of MeOH / MTBE.

[0027] The Zr-BDC membrane prepared by this invention exhibits optimal MeOH / MTBE separation performance, achieving a membrane flux of 5.68 kg·m³ at 40°C for separating 5 wt.% MeOH / MTBE. -2 ·h -1 The separation factor is as high as 25802, and the operational stability is greater than 5 days. Attached Figure Description

[0028] Figure 1 This is a SEM image of the surface and cross-section of the Zr-BDC membrane in Embodiment 1 of the present invention.

[0029] Figure 2 This is a performance diagram (40°C) of the membrane in Example 1 of the present invention.

[0030] Figure 3 This is a performance diagram of the membrane in Example 1 of the present invention (40°C, 5 wt.% MeOH / MTBE).

[0031] Figure 4 This is a SEM image of the surface and cross-section of the Zr-BDC membrane in Embodiment 2 of the present invention.

[0032] Figure 5 This is a performance diagram (40°C) of the membrane in Example 2 of the present invention.

[0033] Figure 6 This is a SEM image of the surface and cross-section of the Zr-BDC membrane in Embodiment 3 of the present invention.

[0034] Figure 7 This is a SEM image of the surface and cross-section of the Zr-BDC membrane in Example 4 of the present invention.

[0035] Figure 8 This is a SEM image of the surface and cross-section of the Zr-BDC membrane in Embodiment 5 of the present invention. Detailed Implementation

[0036] The invention will now be described in detail with reference to the accompanying drawings of the embodiments, but is not limited to the following embodiments.

[0037] Example 1:

[0038] This embodiment provides a method for preparing a Zr-BDC membrane, the specific steps of which are as follows:

[0039] 1) Disperse 0.2253 g (1.36 mmol) of terephthalic acid and 0.0318 g of zirconium propoxide solution (0.068 mmol) in a mixed solvent of 16.5156 g (0.515 mol) methanol, 19.8293 g (0.271 mol) N,N-dimethylformamide and 4.0728 g (0.068 mmol) acetic acid, and sonicate at room temperature to prepare the synthesis solution;

[0040] 2) Place the porous α-Al2O3 support in the reactor and pour in the synthesis solution prepared in step 1). React at 120°C for 12 h. Rinse the surface of the membrane with ethanol to remove the scattered particles, and immerse the membrane in ethanol for 4 h. Then, allow it to dry naturally at room temperature for 12 h to obtain the seed layer membrane.

[0041] 3) Prepare the same synthesis solution as in step 1); place the seed layer film obtained in step 2) in the reactor and pour in the prepared synthesis solution, react at 120°C for 48 h, rinse the scattered particles on the film surface with ethanol, immerse the film in ethanol for 6 h, and then dry it naturally at room temperature for 12 h to obtain the film grown by secondary solvothermal growth.

[0042] 4) Prepare the same solution as in step 1); place the membrane obtained in step 3) after secondary solvothermal growth in the reactor and pour in the prepared synthesis solution, react at 120°C for 24 h, rinse the scattered particles on the membrane surface with ethanol, soak the membrane in ethanol overnight, and then air dry at room temperature for 48 h to obtain the Zr-BDC membrane after tertiary solvothermal growth.

[0043] The prepared Zr-BDC film was characterized by SEM. Figure 1 (a) The surface SEM image of the Zr-BDC film shows that the Zr-BDC film prepared in this invention has good intergrowth, is dense and defect-free; the corresponding cross-sectional SEM image of the Zr-BDC film ( Figure 1 (b) indicates that the film thickness is approximately 500 nm. Figure 2 The results show that the membrane exhibits excellent performance in the pervaporation separation of methanol / methyl tert-butyl ether. At 40℃, the membrane permeation fluxes for separating 5 wt.%, 15 wt.%, and 20 wt.% MeOH / MTBE are 5.69, 9.32, and 10.63 kg·m³, respectively. -2 ·h -1 The separation factors were 25802, 9778, and 6847, respectively. From... Figure 3 As can be seen, the performance of the membrane did not decrease during the 120h test, and its stability was greater than 5d, which is far superior to that of the commercial polymer membrane (PERVAP 2256).

[0044] Example 2:

[0045] This embodiment provides a novel method for preparing Zr-BDC membranes, the specific steps of which are as follows:

[0046] 1) Disperse 0.2457 g (1.36 mmol) of aminoterephthalic acid and 0.0318 g (0.068 mmol) of zirconium propoxide solution in a mixed solvent of 16.5156 g (0.515 mol) of methanol, 19.8293 g (0.271 mol) of N,N-dimethylformamide and 4.0728 g (0.068 mmol) of acetic acid, and sonicate at room temperature to prepare the synthesis solution;

[0047] 2) Place the porous α-Al2O3 support in the reactor and pour in the synthesis solution prepared in step 1). React at 120°C for 12 h. Rinse the surface of the membrane with ethanol to remove the scattered particles. Then, allow it to dry naturally at room temperature for 8 h to obtain the seed layer membrane.

[0048] 3) Prepare the same synthesis solution as in step 1); place the seed layer film obtained in step 2) in the reactor and pour in the prepared synthesis solution, react at 120°C for 48 h, rinse the scattered particles on the film surface with ethanol, and then let it dry naturally at room temperature for 12 h to obtain the film grown by secondary solvothermal growth.

[0049] 4) Prepare the same solution as in step 1); place the membrane obtained in step 3) after secondary solvothermal growth in the reactor and pour in the prepared synthesis solution, react at 120°C for 24 h, rinse the scattered particles on the membrane surface with ethanol, soak the membrane in ethanol overnight, and then air dry at room temperature for 48 h to obtain the Zr-BDC membrane after tertiary solvothermal growth.

[0050] The prepared Zr-BDC film was characterized by SEM. Figure 4 (a) The surface SEM image of the Zr-BDC film shows that the Zr-BDC film prepared in this invention has good intergrowth; the corresponding cross-sectional SEM image of the Zr-BDC film ( Figure 4 (b) indicates that the film thickness is approximately 500 nm. Figure 5 The results show that the membrane exhibits excellent performance in the pervaporation separation of methanol / methyl tert-butyl ether. At 40℃, the membrane permeation fluxes for separating 5 wt.%, 10 wt.%, and 15 wt.% MeOH / MTBE are 1.69, 2.15, and 2.72 kg·m³, respectively. -2 ·h -1 The separation factors were 4739, 2518 and 2077, respectively, which are far superior to those of commercial polymer membranes (PERVAP 2256).

[0051] Example 3:

[0052] This embodiment provides a method for preparing a Zr-BDC membrane, the specific steps of which are as follows:

[0053] 1) Disperse 0.2253 g (1.36 mmol) of terephthalic acid and 0.0635 g (0.136 mmol) of zirconium n-propoxide solution in a mixed solvent of 16.5156 g (0.515 mol) of methanol, 19.8293 g (0.271 mol) of N,N-dimethylformamide and 4.0728 g (0.068 mmol) of acetic acid, and sonicate at room temperature to prepare the synthesis solution;

[0054] 2) Place the porous α-Al2O3 support in the reactor and pour in the synthesis solution prepared in step 1). React at 110℃ for 11 h. Rinse the surface of the membrane with ethanol to remove the scattered particles. Then, allow it to dry naturally at room temperature for 6 h to obtain the seed layer membrane.

[0055] 3) Prepare the same synthesis solution as in step 1); place the seed layer film obtained in step 2) in the reactor and pour in the prepared synthesis solution, react at 110°C for 48 h, rinse the scattered particles on the film surface with ethanol, and then let it dry naturally at room temperature for 12 h to obtain the film grown by secondary solvothermal growth.

[0056] 4) Prepare the same solution as in step 1); place the membrane obtained in step 3) after secondary solvothermal growth in the reactor and pour in the prepared synthesis solution, react at 110°C for 30 h, rinse the scattered particles on the membrane surface with ethanol, soak the membrane in ethanol overnight, and then air dry at room temperature for 48 h to obtain the Zr-BDC membrane after tertiary solvothermal growth.

[0057] The prepared Zr-BDC film was characterized by SEM. Figure 6 (a) The surface SEM image of the Zr-BDC film shows that the Zr-BDC film prepared in this invention has good intergrowth; the corresponding cross-sectional SEM image of the Zr-BDC film ( Figure 6 (b) indicates that the membrane thickness is approximately 1 μm. At 40 °C, the membrane permeation flux for separating 5 wt.% MeOH / MTBE is 2.68 kg·m³. -2 ·h -1 With a separation factor of 451, it outperforms commercial polymer membranes (PERVAP 2256).

[0058] Example 4

[0059] This embodiment provides a method for preparing a Zr-BDC membrane, the specific steps of which are as follows:

[0060] 1) Disperse 0.2253 g (1.36 mmol) of terephthalic acid and 0.0635 g (0.136 mmol) of zirconium n-propoxide solution in a mixed solvent of 16.5156 g (0.515 mol) of methanol, 19.8293 g (0.271 mol) of N,N-dimethylformamide and 4.0728 g (0.068 mmol) of acetic acid, and sonicate at room temperature to prepare the synthesis solution;

[0061] 2) Place the porous α-Al2O3 support in the reactor and pour in the synthesis solution prepared in step 1). React at 130℃ for 10 h. Rinse the surface of the membrane with ethanol to remove the scattered particles, and immerse the membrane in ethanol for 6 h. Then, allow it to dry naturally at room temperature for 12 h to obtain the seed layer membrane.

[0062] 3) Prepare the same synthesis solution as in step 1); place the seed layer film obtained in step 2) in the reactor and pour in the prepared synthesis solution, react at 130°C for 48 h, rinse the scattered particles on the film surface with ethanol, and then let it dry naturally at room temperature for 12 h to obtain the film grown by secondary solvothermal growth.

[0063] 4) Prepare the same solution as in step 1); place the membrane obtained in step 3) after secondary solvothermal growth in a reaction vessel and pour in the prepared synthesis solution, react at 130°C for 20 h, rinse the scattered particles on the membrane surface with ethanol, soak the membrane in ethanol overnight, and then air dry at room temperature for 36 h to obtain the Zr-BDC membrane after tertiary solvothermal growth.

[0064] The prepared Zr-BDC film was characterized by SEM. Figure 7 (a) The surface SEM image of the Zr-BDC film shows that the Zr-BDC film prepared in this invention has good intergrowth; the corresponding cross-sectional SEM image of the Zr-BDC film ( Figure 7 (b) indicates that the membrane thickness is approximately 700 nm. At 40 °C, the membrane permeation flux for separating 5 wt.% MeOH / MTBE is 3.28 kg·m³. -2 ·h -1 With a separation factor of 1008, it outperforms commercial polymer membranes (PERVAP 2256).

[0065] Example 5

[0066] This embodiment provides a method for preparing a Zr-BDC membrane, the specific steps of which are as follows:

[0067] 1) Disperse 0.2253 g (1.36 mmol) of terephthalic acid and 0.0477 g (0.102 mmol) of zirconium propoxide solution in a mixed solvent of 16.5156 g (0.515 mol) of methanol, 19.8293 g (0.271 mol) of N,N-dimethylformamide and 4.0728 g (0.068 mmol) of acetic acid, and sonicate at room temperature to prepare the synthesis solution;

[0068] 2) Place the porous α-Al2O3 support in the reactor and pour in the synthesis solution prepared in step 1). React at 120°C for 12 h. Rinse the surface of the membrane with ethanol to remove the scattered particles. Then, allow it to dry naturally at room temperature for 6 h to obtain the seed layer membrane.

[0069] 3) Prepare the same synthesis solution as in step 1); place the seed layer film obtained in step 2) in the reactor and pour in the prepared synthesis solution, react at 120°C for 48 h, rinse the scattered particles on the film surface with ethanol, and then let it dry naturally at room temperature for 12 h to obtain the film grown by secondary solvothermal growth.

[0070] 4) Prepare the same solution as in step 1); place the membrane obtained in step 3) after secondary solvothermal growth in the reactor and pour in the prepared synthesis solution. React at 120°C for 20 h. Rinse the surface of the membrane with ethanol to remove scattered particles, and soak the membrane in ethanol overnight. Then, allow it to dry naturally at room temperature for 48 h to obtain the Zr-BDC membrane after tertiary solvothermal growth.

[0071] The prepared Zr-BDC film was characterized by SEM. Figure 8 (a) The surface SEM image of the Zr-BDC film shows that the Zr-BDC film prepared in this invention has good intergrowth; the corresponding cross-sectional SEM image of the Zr-BDC film ( Figure 8 (b) indicates that the membrane thickness is approximately 850 nm. At 40 °C, the membrane permeation flux for separating 5 wt.% MeOH / MTBE is 3.60 kg·m³. -2 ·h -1 The separation factor is 13085, which is superior to that of commercial polymer membranes (PERVAP 2256).

[0072] The above description is a specific embodiment of the present invention. Those skilled in the art can refer to the content of this article and, without departing from the technical scope of the present invention, appropriately optimize the synthesis route and explore its application in the separation of organic mixtures. The scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for preparing a Zr-BDC membrane for separating methanol / methyl tert-butyl ether; characterized in that, The Zr-BDC membrane was prepared by a three-stage solvothermal method, including the following steps: 1) Disperse the organic ligand and zirconium propoxide solution in a mixed solvent of methanol, N,N-dimethylformamide and acetic acid, and sonicate at room temperature to prepare the synthesis solution; 2) Place the porous α-Al2O3 support in the reactor and pour in the synthesis solution prepared in step 1). React at 110~130 °C for 10~12 h. Rinse the surface of the membrane with ethanol to remove the scattered particles, immerse the membrane in ethanol, and then let it dry naturally at room temperature to obtain the seed layer membrane. 3) Prepare the same synthesis solution as in step 1); place the seed layer film obtained in step 2) in the reactor and pour in the prepared synthesis solution, react at 110~130 ℃ for 48±2 h, rinse the scattered particles on the surface of the film with ethanol, immerse the film in ethanol, and then dry it naturally at room temperature to obtain the film grown by secondary solvothermal growth. 4) Prepare the same solution as in step 1); place the membrane obtained in step 3) after secondary solvothermal growth in the reactor and pour in the prepared synthesis solution. React at 110~130 ℃ for 20~30 h. Rinse the surface of the membrane with ethanol to remove the scattered particles, and soak the membrane in ethanol overnight. Then dry it naturally at room temperature to obtain the Zr-BDC membrane after tertiary solvothermal growth. The organic ligand is terephthalic acid or aminoterephthalic acid; the molar ratio of the organic ligand to zirconium propoxide is 2:0.2~0.1; the molar ratio of the mixed solvents methanol, N,N-dimethylformamide and acetic acid is 7.6:4:1; and the molar ratio of acetic acid to zirconium propoxide is 100:0.2~0.

1.

2. The method for preparing the Zr-BDC membrane as described in claim 1; characterized in that, Step 2) or 3) Dry naturally at room temperature for 6-24 hours.

3. The method for preparing the Zr-BDC membrane as described in claim 1; characterized in that, Step 4) Dry naturally at room temperature for 24~48 hours.

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