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Method for separating low-concentration 1,2-propanediol from ethylene glycol by azeotropic distillation

An azeotropic distillation column and ethylene glycol technology, applied in chemical instruments and methods, preparation of organic compounds, organic chemistry, etc., can solve the problem of heavy load of ketal removal unit, high energy consumption, large amount of ketal, etc. problems, to achieve the effects of reducing equipment investment and energy consumption, simplifying the separation process, and high yield

Active Publication Date: 2020-11-06
EAST CHINA UNIV OF SCI & TECH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

However, this process requires the use of 1-octene equivalent to the sum of the mass of propylene glycol and ethylene glycol to achieve this effect, so the energy consumption of this separation scheme is very large; Guo Yanzi et al. found that C 7 ~C 10 The ketal can be used as an entrainer, but a ketal with a molar mass of 1.5 to 3 times that of ethylene glycol is required to distill all the ethylene glycol to the top of the tower for extraction, which requires a large amount of ketal and high energy consumption; in addition, ketal The polarity of aromatics and olefins is stronger than that of aromatics and olefins, so the solubility in ethylene glycol is also large, and the load for removing ketal units is heavy
[0004] The above-mentioned extractive distillation, azeotropic distillation and other methods all need to introduce a third component to realize the separation of ethylene glycol and 12PDO, and in order to recover the extractant or entrainer, an additional recovery tower needs to be designed, which increases the complexity of the process. Complexity and operating energy consumption

Method used

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  • Method for separating low-concentration 1,2-propanediol from ethylene glycol by azeotropic distillation

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0024] The flow rate is 1000kmol / hr, the raw material containing 99.8% ethylene glycol (EG) and 0.2% (mol) of 1,2 propylene glycol (12PDO) enters the EG-12PDO separation tower T101 together with dimethyl oxalate (DMO), and the separation tower The operating pressure of T101 is 10bar, the number of trays is 60, and the reflux ratio is 20; the EG product of 997.8kmol / h and 99.9% (mol) is obtained at the bottom of the tower; the azeotropic mixture of DMO and 12PDO is at the top of the tower, and the top mixture enters Low-pressure azeotropic distillation column T102;

[0025] The operating pressure of the low-pressure azeotropic rectification column T102 is 1 bar, the number of trays is 60, and the reflux ratio is 10; the 12PDO of 1.995 kmol / h and 99.9% (mol) is obtained at the bottom of the tower, and the azeotrope of 12PDO and DMO is obtained at the top of the tower. Containing 12PDO17.6% (mol), the overhead stream enters the high-pressure azeotropic rectification tower T103 su...

Embodiment 2

[0028] Flow rate is 1000kmol / hr, containing EG 99.8%, the raw material containing 12PDO 0.2% (mol) enters EG-12PDO separation tower T101 together with DMO, the operating pressure of separation tower T101 is 10bar, plate number 60, reflux ratio is 20; The EG product of 998kmol / h, 99.9% (mol) is obtained at the bottom of the tower; the azeotropic mixture of DMO and 12PDO is obtained at the top of the tower, and the mixture at the top of the tower enters the low-pressure azeotropic rectification tower T102 subsequently;

[0029] The operating pressure of the low-pressure azeotropic rectification column T102 is 5 bar, the number of trays is 72, and the reflux ratio is 9; the 12PDO of 1.991kmol / h, 99.9% (mol) is obtained at the bottom of the tower, and the azeotropic mixture of 12PDO and DMO is obtained at the top of the tower. Containing 12PDO30.2% (mol), the overhead stream enters the high-pressure azeotropic rectification tower T103 subsequently;

[0030] The operating pressure ...

Embodiment 3

[0032] Flow rate is 1000kmol / hr, containing EG 99.8%, the raw material containing 12PDO 0.2% (mol) enters EG-12PDO separation tower T101 together with DMO, the operating pressure of separation tower T101 is 10bar, plate number 60, reflux ratio is 20; The EG product of 997.7kmol / h, 99.9% (mol) is obtained at the bottom of the tower; the azeotropic mixture of DMO and 12PDO is obtained at the top of the tower, and the mixture at the top of the tower enters the low-pressure azeotropic rectification tower T102 subsequently;

[0033] The operating pressure of the low-pressure azeotropic rectification column T102 is 10bar, the number of trays is 90, and the reflux ratio is 8; the 12PDO of 1.993kmol / h and 99.9% (mol) is obtained at the bottom of the tower, and the azeotropic mixture of 12PDO and DMO is obtained at the top of the tower. Containing 12PDO38.2% (mol), the overhead stream enters the high-pressure azeotropic rectification tower T103 subsequently;

[0034] The operating pres...

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Abstract

The invention discloses a method for separating 1,2-propanediol (12PDO) with low concentration from ethylene glycol (EG) by adopting an azeotropic distillation method. The method comprises the following steps: enabling a mixture of the EG and the12 PDO and an entrainer DMO to jointly enter an ethylene glycol knockout tower to obtain an EG product at the tower bottom and an azeotrope of the 12 PDOand the DMO at tower top; sequentially carrying out low-pressure azeotropy and high-pressure azeotropy and respectively separating out the 12 PDO and the DMO, wherein the entrainer DMO can be recycled. The method disclosed by the invention has the advantage that the problem that a mixture of the EG as an overhead product and other by-product dihydric alcohol are difficultly separated in a processof preparing the EG by using coal-based synthesis is solved. According to the process disclosed by the invention, a main product EG has high purity and high yield; in addition, the entrainer DMO can be repeatedly recovered and recycled; a hydrogenation reaction raw material DMO is used as the entrainer, so that the introduction of a third component is avoided, the separation process of the EG is simplified, equipment investment and energy consumption of the whole process are reduced and important economic value is achieved.

Description

technical field [0001] The invention belongs to the technical field of chemical industry, and specifically relates to a method for separating low-concentration 1,2-propanediol (12PDO) from ethylene glycol by azeotropic rectification. The method is used for high-purity ethylene glycol in the process of preparing ethylene glycol from coal-based syngas Alcohol refining. Background technique [0002] Ethylene glycol (EG) is an important chemical raw material, mainly used in the production of polyester fibers, polyester plastics, antifreeze, lubricants, plasticizers, explosives and chemical intermediates. The process routes for synthesizing EG mainly include petroleum route, coal-to-EG route and biomass-to-EG route. At present, the dominant route is still petroleum route—ethylene oxide hydration method. With the increasing shortage of petroleum resources, the development of C1 chemical industry based on natural gas and coal-based raw materials has important practical significanc...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C07C29/82C07C31/20
CPCC07C29/82C07C31/202
Inventor 沈荣春李伟周静红郑赛男孙建磊
Owner EAST CHINA UNIV OF SCI & TECH