Method for separating p-xylene from mixed xylene

Abstract

The invention relates to a method for separating p-xylene from mixed xylene, and mainly solves the problem of high energy consumption during the separation in the prior art. The method comprises the following steps of: crystallizing the mixed xylene in a crystallizer and allowing the crystal magma to flow out from the bottom of the crystallizer; separating the crystal magma by a solid-liquid separator to obtain p-xylene crystals and crystallized and filtered mother liquor; melting the p-xylene crystals after heat exchange, wherein 5 to 30 weight percent of the p-xylene is returned to the solid-liquid separator to serve as washing solution, and 70 to 95 weight percent of the p-xylene serving as a product enter a product can; the crystallized and filtered mother liquor is divided into two streams, of which 5 to 95 weight percent of the crystallized and filtered mother liquor of the first stream is returned to the crystallizer, and 5 to 95 weight percent of the crystallized and filtered mother liquor of the second stream is fed into a mother liquor can after exchanging heat with the mixed xylene; clarifying a part of crystal magma in the crystallizer to obtain crystallized clear mother liquor; allowing the crystallized clear mother liquor to flow out of the side face of the crystallizer; and packaging the crystallized clear mother liquor in the mother liquor can after exchanging heat with the mixed xylene. The technical scheme for separating the p-xylene from the mixed xylene solves the problem well and can be used in the industrial production of the p-xylene.

Description

technical field [0001] The invention relates to a method for separating p-xylene from mixed xylenes. Background technique [0002] P-xylene is an important raw material for the polyester industry, mainly used to produce purified terephthalic acid (PTA) or purified dimethyl terephthalate (DMT), and then produce polyester (PET) from PTA and DMT, and separate Mixed xylene is the main production method of p-xylene. Mixed xylenes are mainly composed of p-xylene, m-xylene, o-xylene and ethylbenzene. The difference between the boiling points of each component is small, but the difference in melting point is large. The crystallization method can be used to separate p-xylene. [0003] The patent US5448005 discloses a method for separating p-xylene from mixed xylenes. This method separates high-purity p-xylene products through the first-stage crystallization process, and recovers the remaining p-xylene in the crystallization mother liquor through the second-stage crystallization proc...

AI Technical Summary

Problems solved by technology

[0004] The technical problem to be solved by the present invention is the problem of large energy consumption in the existi

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