CN-117046322-B - Zr-based membrane for benzene/cyclohexane separation and preparation method thereof

Abstract

The invention provides a Zr-based membrane for separating benzene/cyclohexane and a preparation method thereof, wherein the Zr-based membrane comprises a Zr-BDC membrane, a Zr-BDC-PAA or a Zr-BDC-PVA, a polymer is introduced into a Zr-BDC frame through a secondary growth method, the separation selectivity of the membrane to benzene/cyclohexane is improved, the Zr-based membrane is directly synthesized through an in-situ growth method, the synthesis process is simple, and the good benzene/cyclohexane separation performance is realized by adjusting the growth time of the membrane. The Zr-BDC-PAA or Zr-BDC-PVA film is an organic-inorganic hybrid film, and the addition of the polymer can adjust the pore canal structure of the film, enhance the polarity of the film, improve the size selectivity of the film to benzene/cyclohexane separation, promote the intergrowth of the Zr-BDC base film and influence the film thickness to a certain extent. The Zr-BDC film grows to be more compact and continuous by adjusting the growth time of the film, thereby showing good benzene/cyclohexane separation performance.

Inventors

• LIU XINLEI
• WANG CAIXIA

Assignees

• 天津大学

Dates

Publication Date

20260505

Application Date

20230911

Claims (5)

1. 1. A method for preparing a Zr-based membrane for benzene/cyclohexane separation, characterized in that the Zr-based membrane comprises a Zr-BDC-PAA or Zr-BDC-PVA membrane: 1) Placing an alpha-alumina carrier in a reaction kettle containing zirconium chloride, terephthalic acid, deionized water and N, N-dimethylformamide mixed solution, and then placing the reaction kettle in a high-temperature blast drying box at 120 ℃ for reacting for more than 12 hours to prepare a Zr-BDC film; 2) Putting the obtained Zr-BDC film into a reaction kettle containing zirconium chloride, terephthalic acid, deionized water, N-dimethylformamide and polyacrylic acid or polyvinyl alcohol, and then putting the reaction kettle into a blast drying box at 120 ℃ for reaction for 24-72 hours to obtain a Zr-BDC-PAA or Zr-BDC-PVA film; 3) And washing the prepared Zr-BDC-PAA or Zr-BDC-PVA film by using absolute ethyl alcohol until no powder is accumulated on the surface of the film, soaking the film in the absolute ethyl alcohol to remove the residual solvent in the film holes, taking out and drying in a vacuum drying oven at 50-80 ℃ to obtain the Zr-BDC-PAA or Zr-BDC-PVA film.
2. 2. The method of claim 1, wherein the molar ratio of zirconium chloride, terephthalic acid, deionized water, and N, N-dimethylformamide in step 1) is 1:1:1:500.
3. 3. The method of claim 1, wherein in step 2), the molar ratio of zirconium chloride, terephthalic acid, deionized water, N-dimethylformamide to polyacrylic acid or polyvinyl alcohol is 1:x:1:500:2 (1-x), wherein 2 (1-x) is the molar amount of the polymer monomer, and x=0.7 to 0.9.
4. 4. The method according to claim 1, wherein the reaction is carried out in a high-temperature blast drying oven at 120 ℃ in step 1) for 12 to 48 hours.
5. 5. The method according to claim 1, wherein the reaction is carried out in a high temperature blow drying oven at 120 ℃ in step 1) for 12 to 24 hours.

Description

Zr-based membrane for benzene/cyclohexane separation and preparation method thereof Technical Field The invention belongs to the technical field of preparation of organic-inorganic hybrid films, and designs a Zr-based film for separating benzene/cyclohexane and a preparation method thereof, which are suitable for separation application of benzene/cyclohexane at different temperatures (30-100 ℃). Background In industrial production, cyclohexane is produced mainly by benzene hydrogenation. Inevitably, benzene remains in the product, and benzene/cyclohexane separation is of great importance in order to meet the industrial demand for pure cyclohexane. But the benzene and cyclohexane have similar molecular dynamics dimensions (only poor) The boiling points are similar (only 0.6K difference) and an azeotrope is formed at 55% benzene/45% cyclohexane (v/v). Conventional separation techniques such as distillation, extraction, etc. are difficult to separate. The vapor permeation takes the partial pressure difference of the components at two sides of the membrane as driving force, and the components in the mixture are separated by means of preferential permeation of the membrane, so that the method has the advantages of simple process, easy control of operation, low equipment cost and the like, and meanwhile, a third component is not required to be introduced, so that the product quality is stable, and the process is environment-friendly. Pervaporation is used as an emerging membrane separation technology with phase change, has the advantages of simple operation condition, high separation efficiency, environmental protection and unique advantages in the aspects of near-boiling substance and azeotrope separation. Common membranes in the current separation research of benzene/cyclohexane are polymer membranes, inorganic zeolite membranes and organic-inorganic hybrid membranes. Among them, polymer films are easily swelled in organic solvents, some polymer films such as polyvinyl chloride (PVC) films have poor photo-thermal stability, polyimide films have good organic durability, but the permeability of organic liquid is too small. By the copolymerization method, an acrylic acid-methyl acrylate copolymer film, an ethylene-vinyl alcohol copolymer film, a polyvinyl chloride @ ethylene-vinyl acetate copolymer film, and the like are synthesized, and it is difficult to obtain high permeability (flux) and selectivity (separation factor) due to a large molecular size and a similar aromatic/aliphatic molecular structure. The inorganic zeolite membrane has high cost, the synthesis needs a guiding agent, and the intergranular defects such as cracks, pinholes and the like are easy to generate in the process of removing the guiding agent. Among organic-inorganic hybrid membranes, mixed matrix membranes are more common, in which the filler acts to facilitate the transport of components, which can greatly facilitate the diffusion of benzene in the membrane. However, because fillers (e.g., CNTs, MOFs, etc.) have a large specific surface area and a high surface energy, agglomeration is very likely to occur in the polymer matrix, which in turn reduces the separation performance of the membrane. Disclosure of Invention The invention aims to design and develop a Zr-based membrane for benzene/cyclohexane separation, wherein a polymer is introduced into a Zr-BDC frame through a secondary growth method, the separation selectivity of the membrane to benzene/cyclohexane is improved, the Zr-based membrane is directly synthesized through an in-situ growth method, the synthesis process is simple, and the good benzene/cyclohexane separation performance is realized by adjusting the growth time of the membrane. The temperature has obvious influence on the benzene/cyclohexane separation performance, so that the separation performance of the membrane on the benzene/cyclohexane at different temperatures (30-100 ℃) is tested, and the optimal separation temperature is optimized. The technical scheme adopted by the invention is as follows: Zr-based membranes for benzene/cyclohexane separation, including Zr-BDC membranes, zr-BDC-PAA or Zr-BDC-PVA, BDC referring to 1, 4-phthalic acid ligands. The preparation method of the Zr-BDC film for benzene/cyclohexane separation comprises the following steps: 1) Placing an alpha-alumina carrier in a reaction kettle containing zirconium chloride, terephthalic acid, deionized water and N, N-dimethylformamide mixed solution, and then placing the reaction kettle in a high-temperature blast drying box at 120 ℃ for reacting for more than 12 hours to prepare a Zr-BDC film; 2) And cleaning the prepared Zr-BDC film by using absolute ethyl alcohol until no powder is accumulated on the surface of the film, soaking the film in the absolute ethyl alcohol to remove the residual solvent in the film holes, taking out and drying in a vacuum drying oven at 50-80 ℃ to obtain the Zr-BDC film. The preparation method of the Zr-BDC-PAA or Zr-