A method for extracting diethylbenzene intermediate diethylbenzene and p-diethylbenzene through three consecutive extractions and rectifications

Abstract

The present invention provides a method for extracting m-diethylbenzene and p-diethylbenzene from diethylbenzene by three times of successive extractive distillation. The method comprises the following steps: mixing sulfolane, raw materials and the diethylbenzene, adding the mixture into a first extractive distillation tower, obtaining m-diethylbenzene-rich liquid from a tower top, and obtaining a sulfolane mixture from a tower bottom; adding the sulfolane mixture into a first solvent recovery tower, obtaining sulfolane to recycle from the tower bottom, obtaining p-diethylbenzene-rich liquid from the tower top; adding the m-diethylbenzene-rich liquid and the sulfolane into a second extractive distillation tower, obtaining m-diethylbenzene of which the content is greater than or equal to 95.0 wt% from the tower top, and adding a sulfolane mixture obtained from the tower bottom into a second solvent recovery tower to obtain sulfolane to recycle; and adding the p-diethylbenzene-rich liquid and glycerol into a third extractive distillation tower, obtaining p-diethylbenzene of which the content is greater than or equal to 95.0 wt% from the tower top, adding a glycerol mixture obtained from the tower bottom into a third solvent recovery tower to obtain glycerol to recycle. According to the method provided by the present invention, by using three times of extractive distillation, the content of the m-diethylbenzene is above 95.0 wt%, and the content of the p-diethylbenzene is above 95.0 wt%.

Description

technical field [0001] The invention relates to a separation method of mixed diethylbenzene, in particular to a method for extracting the middle diethylbenzene and p-diethylbenzene of mixed diethylbenzene through three consecutive extraction and rectifications. Background technique [0002] my country is rich in mixed diethylbenzene resources. Industrially, polyethylbenzene is produced as a by-product during the production of ethylbenzene and styrene by alkylation of benzene, which is as high as nearly 1 million tons per year. The polyethylbenzene is separated by rectification to obtain mixed diethylbenzene fractions. Mixed diethylbenzene Intermediate diethylbenzene and p-diethylbenzene are important chemical raw materials and intermediates. Diethylbenzene is an indispensable desorbent for producing pure p-xylene in the production process of polyester. Diethylbenzene can also be used as a chemical etchant for aluminum alloy printing plates, plastic molds, an extraction agen...

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Problems solved by technology

Although the precision distillation method is a mature technology, its disadvantages are large number of plates, large reflux ratio, low separation yield and high cost; the complex extraction and crystallization method utilizes the difference in relative alkalinity of C10 aromatic isomers, and HF and BF 3 As a complexing agent, m-diethylbenzene is selectively separated at 0°C ~ room temperature and 5 atm, and then high-purity p-diethylbenzene can be obtained through crystallization treatment. The equipment scale and operating costs of this process are relatively low, and the reaction conditions are relatively mild. , can significantly reduce energy consumption, but HF and BF 3 It has strong toxicity and corrosiveness, so this method has high requirements for the material and operation control of the equipment, and it will also cause environmental pollution; the crystallization method is a method that utilizes the melting point difference between diethylbenzene isomers The separation method has the advantages of mature technology, good operating performance, no pollution, and no corrosion, but the required equipment is huge, energy consumption is high, and the yield and purity are limited by the eutectic point of isomers; Substances and carbonyls have a strong adsorption effect to separate m-diethylbenzene and p-diethylbenzene. The advantages of the adsorption method are stable operation and high product purity. The disadvantage is that the investment is large, and it is difficult to determine efficient adsorbents and corresponding desorbents.

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