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CN-122010687-A - Continuous extraction, rectification and separation method for paraxylene-propanol azeotropic mixture

CN122010687ACN 122010687 ACN122010687 ACN 122010687ACN-122010687-A

Abstract

The invention provides a continuous extraction, rectification and separation method of a paraxylene-propanol azeotropic mixture, belonging to the technical field of separation. The method adopts any two of dibutyl phthalate, N-methyl pyrrolidone and sulfolane as an extractant. Adding the mixed raw material liquid of paraxylene and propanol into an extraction tower, adding an extractant, carrying out extractive distillation, extracting a propanol product from the tower top, introducing the bottom product of the extraction tower containing the extractant and paraxylene into a solvent recovery tower, rectifying, extracting the paraxylene product from the tower top, discharging the extractant from the bottom of the solvent recovery tower, and introducing the extractant into the extraction tower for recycling. The method provided by the invention realizes the separation of the p-xylene-propanol azeotropic mixture, has high separation efficiency, is easy to regenerate and is environment-friendly, and the mass fraction of the separated propanol and p-xylene can reach more than or equal to 99.9%.

Inventors

  • YUAN MEILONG
  • ZHAO YU
  • JI LEI

Assignees

  • 中材国际环境工程（北京）有限公司

Dates

Publication Date
20260512
Application Date
20260203

Claims (10)

  1. 1. A continuous extraction, rectification and separation method for an azeotropic mixture of paraxylene and propanol is characterized in that any two of dibutyl phthalate, N-methylpyrrolidone and sulfolane are adopted as an extractant.
  2. 2. The preparation method of claim 1, wherein the extractant is a mixture of dibutyl phthalate and sulfolane, and the mass ratio of dibutyl phthalate to sulfolane is 1 (1-2).
  3. 3. The preparation method of claim 1, wherein the extracting agent is a mixture of N-methylpyrrolidone and sulfolane, and the mass ratio of the N-methylpyrrolidone to the sulfolane is 1 (1-2).
  4. 4. The preparation method of claim 1, wherein when the extractant is a mixture of N-methylpyrrolidone and dibutyl phthalate, the mass ratio of N-methylpyrrolidone to dibutyl phthalate is 1 (1-2).
  5. 5. The method according to any one of claims 1 to 4, comprising the steps of: s1, adding a mixed raw material liquid of paraxylene-propanol from a feed inlet of an extraction tower, adding an extracting agent from an upper feed inlet of the extraction tower, performing extraction rectification, condensing steam rich in propanol into liquid at the top of the tower through a condenser, wherein one part of the liquid is extracted as a propanol product, and the other part of the liquid is returned to the tower as condensate; S2, introducing a tower bottom product of the extraction tower into a middle feed inlet of the solvent recovery tower, and after separation, rising steam rich in paraxylene to the tower top for condensation, extracting the paraxylene product from the tower top, and introducing the paraxylene product into a product tank for storage; s3, introducing the extractant discharged from the bottom of the solvent recovery tower into the upper part of the extraction tower, and entering the extraction tower for recycling.
  6. 6. The process according to claim 5, wherein the mass ratio of the mixed raw material liquid of p-xylene-propanol to the extractant is 1 (1-3).
  7. 7. The process according to claim 5, wherein the theoretical plate number of the extraction column is 45 to 72 and the reflux ratio is (0.5 to 1.5): 1.
  8. 8. The method according to claim 5, wherein the temperature of the top of the extraction column is 95-98 ℃, the temperature of the bottom of the extraction column is 115-135 ℃, the pressure of the top of the extraction column is 101 kPa, and the total pressure drop of the extraction column is 5-8 kPa.
  9. 9. The process according to claim 7, wherein the number of feed trays for adding the extractant to the extraction column is 6 to 8, and the number of feed trays for adding the mixed raw material liquid to the extraction column is 23 to 26.
  10. 10. The process according to claim 5, wherein the theoretical plate number of the solvent recovery column is 17 to 24, the reflux ratio is (1.4 to 2.1): 1, the temperature of the top of the solvent recovery column is 134 to 142 ℃, the temperature of the bottom of the column is 180 to 220 ℃, the pressure of the top of the column is 101 kPa, and the pressure drop of the column is 4 to 6 kPa.

Description

Continuous extraction, rectification and separation method for paraxylene-propanol azeotropic mixture Technical Field The invention belongs to the technical field of separation, and particularly relates to a continuous extraction, rectification and separation method of a paraxylene-propanol azeotropic mixture. Background Para-xylene (PX) is a core raw material of the polyester industry, and is mainly used for Producing Terephthalic Acid (PTA), further synthesizing polyester fibers, PET plastics, films and the like, and is widely applied to the fields of spinning, packaging, electronics and the like. Propanol (n-propanol/isopropanol) is a common organic solvent, can be used for diluting paint, printing ink and adhesive, is also used for pharmaceutical and cosmetic formulas, and can be used as a chemical intermediate for synthesizing ester and ether compounds. The mixture of the paraxylene and the propanol is easy to form the lowest azeotrope, and the common rectification can not realize complete separation through a single tower, so that the azeotropic balance is required to be additionally broken. Near the azeotropic composition, the difference of the volatilization capacity of the two is very small, so that the number of theoretical plates required by rectification is very large, and the separation difficulty is greatly improved. And both are organic solvents, so that the intersolubility is good, the intermolecular acting force is similar, and the separation driving force is further weakened. Extraction and rectification are effective techniques for solving the separation of a low-relative-volatility system, and are characterized in that the extraction agent is added to strengthen the relative volatility difference among mixed components, thereby reducing the separation difficulty and the energy consumption. At present, the method has few researches on the extractive distillation of a paraxylene and propanol system, and the prior art mostly adopts a single extractant (such as sulfolane and NMP), has the problems of insufficient selectivity, high solvent recovery difficulty, high energy consumption and the like, has poor combination adaptability of partial mixed extractants, is easy to generate layering, high solvent loss and the like, and is difficult to meet the requirement of industrial large-scale production. Therefore, the composite extractant and the matched process with high selectivity, low energy consumption, environmental protection and economy are developed, and the method has important industrial application value. Disclosure of Invention The invention aims to provide a continuous extraction, rectification and separation method for an azeotropic mixture of paraxylene and propanol, which effectively overcomes the technical defects existing in the prior art. To achieve the above object or other objects, the present invention is achieved by the following technical solutions. A continuous extraction, rectification and separation method for an azeotropic mixture of paraxylene and propanol adopts any two of dibutyl phthalate, N-methyl pyrrolidone and sulfolane as an extractant. Further, the extractant is a mixture of dibutyl phthalate and sulfolane, or a mixture of N-methylpyrrolidone and sulfolane, or a mixture of N-methylpyrrolidone and dibutyl phthalate. More preferably, when the extractant is a mixture of dibutyl phthalate and sulfolane, the mass ratio of dibutyl phthalate to sulfolane is 1 (1-2). More preferably, when the extractant is a mixture of N-methylpyrrolidone and sulfolane, the mass ratio of N-methylpyrrolidone to sulfolane is 1 (1-2). More preferably, when the extractant is a mixture of N-methylpyrrolidone and dibutyl phthalate, the mass ratio of N-methylpyrrolidone to dibutyl phthalate is 1 (1-2). Further, the method comprises the following steps: s1, adding a mixed raw material liquid of paraxylene-propanol from a feed inlet of an extraction tower, adding an extracting agent from an upper feed inlet of the extraction tower, performing extraction rectification, condensing steam rich in propanol into liquid at the top of the tower through a condenser, wherein one part of the liquid is extracted as a propanol product, and the other part of the liquid is returned to the tower as condensate; S2, introducing a tower bottom product of the extraction tower into a middle feed inlet of the solvent recovery tower, and after separation, rising steam rich in paraxylene to the tower top for condensation, extracting the paraxylene product from the tower top, and introducing the paraxylene product into a product tank for storage; s3, introducing the extractant discharged from the bottom of the solvent recovery tower into the upper part of the extraction tower, and entering the extraction tower for recycling. Further, the mass ratio of the mixed raw material liquid of the paraxylene-propanol to the extractant is 1 (1-3). In the present invention, the ratio of paraxylene to propanol in the paraxylene-p