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CN-122010686-A - Continuous extraction, rectification and separation method for p-xylene-butanol mixture

CN122010686ACN 122010686 ACN122010686 ACN 122010686ACN-122010686-A

Abstract

The invention provides a continuous extraction, rectification and separation method of a p-xylene-butanol mixture, belonging to the technical field of separation. The method adopts any two of sulfolane, N-methylpyrrolidone and dimethyl sulfoxide as an extractant, the mixed raw material liquid of paraxylene and butanol is added into an extraction tower, then the extractant is added for extraction and rectification, butanol products are extracted from the tower top, the bottom products of the extraction tower containing the extractant and paraxylene are introduced into a solvent recovery tower, after rectification, the paraxylene products can be extracted from the tower top, the extractant is discharged from the bottom of the solvent recovery tower, and the extractant is introduced into the extraction tower for recycling. The method provided by the invention realizes the separation of the p-xylene-butanol azeotropic mixture, has high separation efficiency, is easy to regenerate and is environment-friendly, and the mass fraction of the separated butanol 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 a p-xylene-butanol mixture is characterized in that any two of sulfolane, N-methylpyrrolidone and dimethyl sulfoxide are adopted as an extractant.
  2. 2. The preparation method of claim 1, wherein the extractant is a mixture of sulfolane and N-methylpyrrolidone, and the mass ratio of sulfolane to N-methylpyrrolidone is 1 (0.4-1.8).
  3. 3. The preparation method of claim 1, wherein the extracting agent is a mixture of N-methylpyrrolidone and dimethyl sulfoxide, and the mass ratio of the N-methylpyrrolidone to the dimethyl sulfoxide is 1 (0.4-1.8).
  4. 4. The preparation method of claim 1, wherein the extractant is a mixture of dimethyl sulfoxide and sulfolane, and the mass ratio of the dimethyl sulfoxide to the sulfolane is 1 (0.4-1.8).
  5. 5. The method according to any one of claims 1 to 5, comprising the steps of: s1, adding a mixed raw material liquid of paraxylene-butanol from a raw material feed inlet of an extraction tower, adding an extracting agent from an extracting agent feed inlet of the extraction tower, extracting and rectifying, condensing butanol-rich steam into liquid at the tower top through a condenser, wherein one part of the butanol-rich steam is extracted as butanol product, and the other part of the butanol-rich steam is returned into the tower as condensate; s2, introducing a bottom product of the extraction tower into a feed inlet of a solvent recovery tower, rectifying, and then lifting steam rich in paraxylene to the top of the tower for condensation, extracting paraxylene products from the top of the tower, and introducing the paraxylene products 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-butanol to the extractant is 1 (2.2 to 3.2).
  7. 7. The process according to claim 5, wherein the theoretical plate number of the extraction column is 20 to 32 and the reflux ratio is (1.2 to 2.6): 1.
  8. 8. The method according to claim 5, wherein the temperature of the top of the extraction column is 115-120 ℃, the temperature of the bottom of the extraction column is 145-165 ℃, the pressure of the top of the extraction column is 0.1 MPa, and the total pressure drop of the extraction column is 7-10 kPa.
  9. 9. The process according to claim 7, wherein the number of feed trays for adding the extractant to the extraction column is 2 to 8, and the number of feed trays for adding the mixed raw material liquid to the extraction column is 15 to 30.
  10. 10. The process according to claim 5, wherein the theoretical plate number of the solvent recovery column is 12 to 22 and the reflux ratio is (0.6 to 1.2): 1.

Description

Continuous extraction, rectification and separation method for p-xylene-butanol 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 p-xylene-butanol mixture. Background Para-xylene (PX) and butanol (n-BuOH) are important basic chemical raw materials, PX is a core monomer of polyester industry, the annual demand of the world is over 7000 ten thousand tons, the para-xylene (PX) and butanol (n-BuOH) can be used for Producing Terephthalic Acid (PTA), and the annual consumption of the n-BuOH can be over 1200 ten thousand tons. The two are often accompanied with byproduct systems such as petroleum refining and the like to form a 30-70% mixed system. PX and n-BuOH form the lowest azeotrope under normal pressure, the azeotropic temperature is 99.5 ℃, the azeotropic composition (mol%) is PX 34.8%/n-BuOH 65.2%, the conventional rectification can not be effectively separated, and special rectification or coupling separation technology is needed, so that the efficient separation is difficult to realize. The current industrial production environment and regulation requirements influence the separation technology of the PX-n-BuOH azeotropic system, so that the traditional high-energy separation technology is eliminated, the low-energy extraction and rectification is optimized, the n-BuOH emission is required to reach the standard in terms of VOCs emission control, the recovery efficiency of an extractant is promoted to be more than 99.8%, the related regulation is forbidden to use a high-toxic solvent in terms of solvent environmental protection, the low-toxicity and recoverable solvent is promoted to be applied, and the separation technology is required to meet the requirements that the purity of polyester PX is more than or equal to 99.7%, the purity of industrial n-BuOH is more than or equal to 99.5% and impurity residues are controlled in terms of product purity. Disclosure of Invention The invention aims to provide a continuous extraction, rectification and separation method for a p-xylene-butanol mixture, 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 extracting, rectifying and separating method for the mixture of p-xylene and butanol uses any two of sulfolane, N-methyl pyrrolidone and dimethyl sulfoxide as extractant. Further, the extractant is sulfolane, a mixture of N-methyl pyrrolidone, or a mixture of N-methyl pyrrolidone and dimethyl sulfoxide, or a mixture of dimethyl sulfoxide and sulfolane. More preferably, when the extractant is a mixture of sulfolane and N-methylpyrrolidone, the mass ratio of sulfolane to N-methylpyrrolidone is 1 (0.4-1.8). More preferably, when the extractant is a mixture of N-methylpyrrolidone and dimethyl sulfoxide, the mass ratio of N-methylpyrrolidone to dimethyl sulfoxide is 1 (0.4-1.8). More preferably, when the extractant is a mixture of dimethyl sulfoxide and sulfolane, the mass ratio of the dimethyl sulfoxide to the sulfolane is 1 (0.4-1.8). Further, the method comprises the following steps: s1, adding a mixed raw material liquid of paraxylene-butanol from a raw material feed inlet of an extraction tower, adding an extracting agent from an extracting agent feed inlet of the extraction tower, extracting and rectifying, condensing butanol-rich steam into liquid at the tower top through a condenser, wherein one part of the butanol-rich steam is extracted as butanol product, and the other part of the butanol-rich steam is returned into the tower as condensate; s2, introducing a bottom product of the extraction tower into a feed inlet of a solvent recovery tower, rectifying, and then lifting steam rich in paraxylene to the top of the tower for condensation, extracting paraxylene products from the top of the tower, and introducing the paraxylene products 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-butanol to the extractant is 1 (2.2-3.2). In the present invention, the ratio of paraxylene to butanol in the paraxylene-butanol mixed feed solution may be any. Preferably, the mass percentage of the paraxylene and the butanol in the paraxylene-butanol mixed raw material liquid is (10-40) (60-90). Further, the theoretical plate number of the extraction column is 20 to 32, and the reflux ratio is (1.2 to 2.6): 1. Further, the temperature of the top of the extraction tower is 115-120 ℃, the temperature of the bottom of the extraction tower is 145-165 ℃, the pressure of the top of the extraction tower is 0.1 MPa, and the total pressure drop of the extraction tower is 7-1