| 摘要 |
PURPOSE: A method for separating p-xylene from C8 aromatic hydrocarbons by using simulated moving bed adsorption and crystallization and its apparatus are provided, to obtain p-xylene of high purity continuously. CONSTITUTION: The method comprises the steps of contacting a supply source containing m-xylene, p-xylene, ethylbenzene and optionally o-xylene with a zeolite-based adsorbent layer continuously in the presence of a desorption solvent in at least one simulated moving bed adsorption region, to obtain a first fraction containing a solvent, m-xylene, ethylbenzene and optionally o-xylene and a second fraction containing a solvent and p-xylene of a purity of 75-98 %; distilling the first fraction to separate the desorption solvent from m-xylene, ethylbenzene and optionally o-xylene; isomerizing the mixture in isomerization region to obtain isomers and recirculating the isomers to the first step; distilling the second fraction to separate into a solvent and p-xylene of a purity of 75-98 %; crystallizing the obtained p-xylene in crystallization region of -25 to 10 deg.C to obtain a solution to be recirculated to the first step and the p-xylene crystal soaked in the solution; and washing the p-xylene crystal with a washing solvent to obtain p-xylene of a purity of 99.7 % or more.
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