PURPOSE: To prepare high purity p-xylene, economically, in high yield, by the combination of an adsorption separation process and a crystallization separation process, characterized in that the filtrate free of p-xylene and obtained from the crystallization separation zone is introduced into the concetration region of the adsorption separation zone at a specific position.
CONSTITUTION: A mixture of C8 aromatic hydrocarbons, or raw materials containing the mixture, is fed between the adsorption zone and the concentration zone of an adsorption separation column containing a cation exchange zeolite as an adsorbent, and concentrated p-xylene solution is extracted from an outlet between said concentration zone and a desorption zone. The concentrated solution is cooled at -20W +10°C in the following crystallization separation vessel to crystallize and separate p-xylene. The filtrate obtained from the crystallizer is fed to the adsorption separation column at a position between the mixture-inlet and the p-xylene-outlet and specified by the formula [Z is the position of the filtrate-inlet with reference to the feed-inlet (0%) and the concentrate-outlet (100%); t is crystallization temperature (°C); α is adsorption selectivity of p-xylene based on m-xylene], to obtain high purity p-xylene, economically, in high yield.
TSUCHIYA FUJIO
YAMAGUCHI KOKUSEI
