Preparation method of high-purity methanol

Abstract

The invention relates to a preparation method of high-purity methanol, and belongs to the technical field of methanol generation, the preparation method of the high-purity methanol comprises the following operation steps: placing a modified polyethersulfone microfiltration membrane in a membrane pool, introducing crude methanol into the membrane pool, and filtering to obtain the high-purity methanol, the flow velocity of the crude methanol in the membrane pool purification process being 1-3 L / min, and the permeation side pressure being 10-60 kPa; the preparation method of the modified polyethersulfone microporous filter membrane comprises the following steps: preparing a membrane by using a phase inversion method, adding Zn-MOF-74 into DMAc, adding polyethersulfone after complete dispersion to obtain a membrane casting solution, casting the prepared membrane casting solution on a smooth glass plate, and performing vacuum drying to obtain the modified polyethersulfone microporous filter membrane. The membrane separation technology is adopted, the methanol separation and purification efficiency is effectively improved on the premise that equipment investment is not increased and purification energy consumption is saved, and the content of the prepared methanol can reach 99.99% or above.

Description

Technical Field

[0001] The present invention belongs to the technical field of methanol production, and particularly relates to a method for preparing high-purity methanol. Background Art

[0002] Methanol is an important organic chemical raw material, clean liquid fuel, and important basic product of C1 chemistry. High-purity methanol has a wide range of applications in many fields such as energy, chemical industry, medicine, analytical testing, and national defense. With the continuous progress of technology and the improvement of environmental awareness, the application prospect of high-purity methanol will be even broader.

[0003] The main methods for preparing high-purity methanol include distillation, crystallization, membrane separation, etc. Among them, membrane separation technology has the advantages of high efficiency, energy saving, environmental protection, high selectivity, continuous operation, and easy automation compared with other methods, and is a green and friendly separation technology with great development potential.

[0004] The patent document with the patent publication number CN114011108A discloses a system for separating methanol-water by coupling distillation and membrane separation. The system includes a distillation column, a condenser, a reboiler, a centrifugal pump, and a membrane separator. The method for separating methanol-water using the above system is as follows: a mixture of methanol and water is introduced into the distillation column, and most of the water is separated from the bottom of the distillation column. The residual water and methanol mixed gas evaporated from the top of the distillation column is introduced into the condenser for condensation. The condensed mixture of residual water and methanol is partially refluxed to the distillation column, and the remaining part is pressurized by a centrifugal pump and then enters the membrane separator to finally obtain high-purity methanol.

[0005] The patent document with the patent announcement number CN212833551U discloses a methanol preparation system, including a methanol synthesis unit, a methanol separation unit, a methanol purification unit, and a heat exchange unit. The methanol separation unit is used to cool and separate the primary crude methanol synthesized by the methanol synthesis unit to obtain secondary crude methanol. The methanol purification unit is used to purify the secondary crude methanol to obtain methanol. The heat exchange unit is used to transfer the heat of the primary crude methanol to the secondary crude methanol that is about to enter the methanol purification unit before the primary crude methanol enters the methanol separation unit.

[0006] The above patents and the prior art have too complex a process for refining high-purity methanol, a long operation cycle, and relatively high consumption and energy consumption. Summary of the Invention

[0007] In order to solve the problems in the background art that the prior art for refining high-purity methanol has too complex a process, a long operation cycle, and relatively high consumption and energy consumption, the present invention provides a method for preparing high-purity methanol.

[0008] A preparation method of high-purity methanol, the operation steps of which are as follows:

[0009] Place the modified polyethersulfone microporous membrane in a membrane cell, introduce crude methanol into the membrane cell, filter to obtain high-purity methanol. During the purification process in the membrane cell, the flow rate of the crude methanol is 1-3 L / min, and the pressure on the permeate side is 10-60 kPa.

[0010] Furthermore, the preparation method of the modified polyethersulfone microporous membrane is as follows:

[0011] Use the phase inversion method to prepare the membrane. Add Zn-MOF-74 to DMAc, ultrasonically disperse it for 30 min to completely disperse Zn-MOF-74, then add polyethersulfone, stir at room temperature for 9 h to obtain a membrane casting solution. Degas the prepared membrane casting solution for 12 h, cast it on a smooth glass plate, adjust the height of the casting knife to 200 μm, then immerse the glass plate with the membrane casting solution in ultrapure water for 48 h to remove the residual solvent, and vacuum dry it for 24 h to obtain the modified polyethersulfone microporous membrane;

[0012] Among them, the mass ratio of DMAc, Zn-MOF-74 and polyethersulfone is 80-80.9:0.1-1:19.

[0013] Furthermore, the preparation method of Zn-MOF-74 is as follows:

[0014] Dissolve 2,5-dihydroxyterephthalic acid and zinc nitrate hexahydrate in an aqueous DMF solution, continuously stir for 1 h, then transfer it to a 100 L autoclave, heat it at 100 °C for 24 h. After the reaction is completed, place the autoclave at room temperature to cool naturally. Centrifuge the product once, immerse the obtained solid in DMF and wash for 24 h, change the DMF every 12 h, then immerse the solid in anhydrous methanol for solvent replacement for 48 h, change the anhydrous methanol every 12 h, and finally dry it in a vacuum drying oven at 100 °C for 12 h to obtain Zn-MOF-74;

[0015] Among them, the mass ratio of 2,5-dihydroxyterephthalic acid and zinc nitrate hexahydrate is 0.3:1.2-1.5, and the volume ratio of DMF to deionized water in the aqueous DMF solution is 60:3.

[0016] Furthermore, the average diameter of the modified polyethersulfone microporous membrane is 0.2-0.8 μm.

[0017] The beneficial effects of the present invention:

[0018] 1. The present invention adopts a membrane separation technology, which effectively improves the separation and purification efficiency of methanol without increasing equipment investment and saving energy consumption for purification.

[0019] 2. The present invention prepares a modified polyethersulfone microporous membrane by a phase inversion method using Zn-MOF-74 and polyethersulfone. Zn-MOF-74 has a high specific surface area and adjustable pore size, which can improve the porosity and permeability of the polyethersulfone membrane, enabling methanol molecules to pass through the membrane layer more smoothly, effectively retaining impurity molecules, and improving the purity of methanol. At the same time, hydrophilic groups such as hydroxyl groups in Zn-MOF-74 can be exposed on the surface of the polyethersulfone membrane, thereby increasing the number of hydrophilic groups on the membrane surface. These hydrophilic groups can form hydrogen bonds with water molecules, reduce the interfacial tension between the membrane and water, improve the hydrophilic property of the membrane, and reduce the water content in the methanol product. Further, Zn-MOF-74 has unsaturated coordinated metal sites, and the unsaturated metal sites carry positive charges, so they can produce electrostatic interactions with substances carrying opposite charges or polar molecules, and can adsorb impurities such as CO, H2, NO, and H2O generated during the methanol production process. Moreover, the unsaturated metal sites can form various interactions with the carboxyl groups in organic acid molecules, including hydrogen bonds and coordination bonds. These interactions enable organic acid molecules to be stably adsorbed on the metal surface, thereby adsorbing impurities such as organic acids in the methanol product. Detailed implementation manners

[0020] Next, in combination with the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention.

[0021] Example 1

[0022] A preparation method of high-purity methanol described in this example has the following operating steps:

[0023] Place the modified polyethersulfone microporous membrane in a membrane cell, introduce crude methanol into the membrane cell, filter to obtain high-purity methanol. During the purification process in the membrane cell, the flow rate of the crude methanol is 1 L / min, and the pressure on the permeate side is 10 kPa.

[0024] The preparation method of the modified polyethersulfone microporous membrane is as follows:

[0025] Use the phase inversion method to prepare the membrane. Add 0.1 kg of Zn-MOF-74 to 80.9 kg of DMAc, ultrasonically disperse it for 30 min until Zn-MOF-74 is completely dispersed, then add 19 kg of polyethersulfone, stir at room temperature for 9 h to obtain a membrane casting solution. Degas the prepared membrane casting solution for 12 h, cast it on a smooth glass plate, adjust the height of the casting knife to 200 μm, and then immerse the glass plate with the membrane casting solution in ultrapure water for 48 h to remove the residual solvent. After vacuum drying for 24 h, a modified polyethersulfone microporous membrane is obtained.

[0026] The preparation method of Zn-MOF-74 is as follows:

[0027] Dissolve 0.3 kg of 2,5-dihydroxyterephthalic acid and 1.2 kg of zinc nitrate hexahydrate in 60 L of DMF and 3 L of deionized water, stir continuously for 1 h, then transfer to a 100-L autoclave, heat at 100 °C for 24 h. After the reaction, let the autoclave cool naturally at room temperature. Centrifuge the product once, immerse the obtained solid in DMF and wash for 24 h, changing the DMF every 12 h. Then immerse the solid in anhydrous methanol for solvent replacement for 48 h, changing the anhydrous methanol every 12 h. Finally, dry in a vacuum drying oven at 100 °C for 12 h to obtain Zn-MOF-74.

[0028] The average diameter of the modified polyethersulfone microporous membrane is 0.2 μm.

[0029] Example 2

[0030] A preparation method of high-purity methanol described in this example has the following operating steps:

[0031] Place the modified polyethersulfone microporous membrane in a membrane cell, pass crude methanol into the membrane cell, filter to obtain high-purity methanol. During the purification process of the membrane cell, the flow rate of the crude methanol is 2 L / min, and the pressure on the permeate side is 30 kPa.

[0032] The preparation method of the modified polyethersulfone microporous membrane is as follows:

[0033] Use the phase inversion method to prepare the membrane. Add 0.5 kg of Zn-MOF-74 to 80.5 kg of DMAc, ultrasonicate for 30 min to completely disperse Zn-MOF-74, then add 19 kg of polyethersulfone, stir at room temperature for 9 h to obtain a membrane casting solution. Degas the prepared membrane casting solution for 12 h, cast it on a smooth glass plate, adjust the height of the casting knife to 200 μm, and then immerse the glass plate with the membrane casting solution in ultrapure water for 48 h to remove the residual solvent. After vacuum drying for 24 h, obtain the modified polyethersulfone microporous membrane.

[0034] The preparation method of Zn-MOF-74 is as follows:

[0035] Dissolve 0.3 kg of 2,5-dihydroxyterephthalic acid and 1.3 kg of zinc nitrate hexahydrate in 60 L of DMF and 3 L of deionized water, stir continuously for 1 h, then transfer to a 100-L autoclave, heat at 100 °C for 24 h. After the reaction is completed, let the autoclave cool naturally at room temperature. Collect the product by centrifugation once, immerse the obtained solid in DMF and wash for 24 h, changing the DMF every 12 h. Then immerse the solid in anhydrous methanol for solvent replacement for 48 h, changing the anhydrous methanol every 12 h. Finally, dry in a vacuum drying oven at 100 °C for 12 h to obtain Zn-MOF-74.

[0036] The average diameter of the modified polyethersulfone microporous membrane is 0.5 μm.

[0037] Example 3

[0038] A preparation method of high-purity methanol described in this example has the following operating steps:

[0039] Place the modified polyethersulfone microporous membrane in a membrane cell, introduce crude methanol into the membrane cell, filter to obtain high-purity methanol. During the purification process of the membrane cell, the flow rate of the crude methanol is 3 L / min, and the pressure on the permeate side is 60 kPa.

[0040] The preparation method of the modified polyethersulfone microporous membrane is as follows:

[0041] Use the phase inversion method to prepare the membrane. Add 1 kg of Zn-MOF-74 to 80 kg of DMAc, ultrasonicate for 30 min to completely disperse Zn-MOF-74, then add 19 kg of polyethersulfone, stir at room temperature for 9 h to obtain a membrane casting solution. Degas the prepared membrane casting solution for 12 h, pour it on a smooth glass plate, adjust the height of the casting knife to 200 μm, and then immerse the glass plate with the membrane casting solution in ultrapure water for 48 h to remove the residual solvent. After vacuum drying for 24 h, obtain the modified polyethersulfone microporous membrane.

[0042] The preparation method of Zn-MOF-74 is as follows:

[0043] Dissolve 0.3 kg of 2,5-dihydroxyterephthalic acid and 1.5 kg of zinc nitrate hexahydrate in 60 L of DMF and 3 L of deionized water, stir continuously for 1 h, then transfer to a 100-L autoclave, heat at 100 °C for 24 h. After the reaction is completed, let the autoclave cool naturally at room temperature. Collect the product by centrifugation once, immerse the obtained solid in DMF and wash for 24 h, changing the DMF every 12 h. Then immerse the solid in anhydrous methanol for solvent replacement for 48 h, changing the anhydrous methanol every 12 h. Finally, dry in a vacuum drying oven at 100 °C for 12 h to obtain Zn-MOF-74.

[0044] The average diameter of the modified polyethersulfone microporous membrane is 0.8 μm.

[0045] Comparative Example 1

[0046] The rest is the same as in Example 1, except that the preparation method of the polyethersulfone microporous membrane is as follows:

[0047] Add 19 kg of polyethersulfone to 80 kg of DMAc, stir at room temperature for 9 h to obtain a membrane casting solution. Degas the prepared membrane casting solution for 12 h, pour it on a smooth glass plate, adjust the height of the casting knife to 200 μm, and then soak the glass plate with the membrane casting solution in ultrapure water for 48 h to remove the residual solvent. After vacuum drying for 24 h, a polyethersulfone microporous membrane is obtained.

[0048] Perform the following performance tests on the high-purity methanol obtained by the preparation methods described in Examples 1-3 and Comparative Example 1. The items are as follows:

[0049] The methanol determination method adopts GB338-2011 "Industrial Methanol"; use a Mettler-Toledo DL37 Karl Fischer coulometric moisture analyzer to measure the water content of methanol; use a UV-2100 type ultraviolet-visible spectrophotometer to measure the ultraviolet transmittance of methanol. The above test results are shown in Table 1.

[0050] Table 1

[0051] Methanol content % Water content ppm UV transmittance at wavelength 207 nm % Crude methanol 45.954 1985.4 0.34 Example 1 99.993 216.3 11.4 Example 2 99.995 182.8 12.3 Example 3 99.998 160.4 14.2 Comparative Example 1 92.643 526.4 6.1

[0052] It can be seen from the data in Table 1 that the methanol content obtained in Examples 1-3 is significantly better than that of crude methanol and Comparative Example 1. The methanol content prepared by this method can reach more than 99.99%.

[0053] In the description of the specification, the description referring to terms such as "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0054] The above content is only an example and explanation of the present invention. Those skilled in the art of this technology can make various modifications or supplements to the described specific embodiments or use similar methods to replace them. As long as they do not deviate from the invention or exceed the scope defined by the claims of this patent, they should fall within the protection scope of the present invention.

Claims

1. A method for preparing high-purity methanol, characterized in that, The operation steps are as follows: Place the modified polyethersulfone microporous membrane in a membrane cell, introduce crude methanol into the membrane cell, and filter to obtain high-purity methanol; The preparation method of the modified polyethersulfone microporous membrane is as follows: Add Zn-MOF-74 to DMAc, ultrasonicate for 30 min to completely disperse Zn-MOF-74, then add polyethersulfone, stir at room temperature for 9 h to obtain a membrane casting solution. Degas the prepared membrane casting solution for 12 h, cast it on a glass plate, then soak the glass plate with the membrane casting solution in ultrapure water for 48 h, and dry it in vacuum for 24 h to obtain the modified polyethersulfone microporous membrane.

2. The preparation method of a high-purity methanol according to claim 1, characterized in that, The preparation method of the Zn-MOF-74 is as follows: Dissolve 2,5-dihydroxyterephthalic acid and zinc nitrate hexahydrate in an aqueous DMF solution, continuously stir for 1 h, then transfer it to a high-pressure reactor, heat at 100 °C for 24 h. After the reaction, cool the reactor to room temperature, collect and centrifuge the product once. Immerse the obtained solid in DMF for washing for 24 h, replace DMF every 12 h, then immerse the solid in anhydrous methanol for solvent replacement for 48 h, replace DMF every 12 h, and finally dry it in a vacuum drying oven at 100 °C for 12 h to obtain Zn-MOF-74.

3. The preparation method of a high-purity methanol according to claim 1, characterized in that, During the purification process in the membrane cell, the flow rate of the crude methanol is 1 - 3 L / min, and the pressure on the permeate side is 10 - 60 kPa.

4. The preparation method of a high-purity methanol according to claim 1, characterized in that The mass ratio of DMAc, Zn-MOF-74, and polyethersulfone is 80 - 80.9:0.1 - 1:

19.

5. A method for preparing high-purity methanol according to claim 1, characterized in that, Adjust the height of the casting knife to 200 μm.

6. The preparation method of high-purity methanol according to claim 2, characterized in that, The mass ratio of 2,5-dihydroxyterephthalic acid and zinc nitrate hexahydrate is 0.3:1.2 - 1.

5.

7. The preparation method of high-purity methanol according to claim 2, characterized in that, The volume ratio of DMF to deionized water in the aqueous DMF solution is 60:

3.

8. A method for preparing high-purity methanol according to claim 1, wherein, The average diameter of the modified polyethersulfone microporous membrane is 0.2 - 0.8 μm.