Process for making p-xylene with a purity of more than 99.8% by

Details Process for making p-xylene with a purity of more than 99.8% by Process for making p-xylene with a purity of more than 99.8% by

1989-10-20

1991-10-08

Davis, Curtis R.

Chemistry of hydrocarbon compounds

Purification, separation, or recovery

By cooling of liquid to obtain solid, e.g., crystallization,...

885812, 885816, 885817, C07C 714

Patent

active

050556304

ABSTRACT:
The process for obtaining a p-xylene final product more than 98% pure from a crystalline starting material with a purity of about 98%, includes the steps of intermixing the starting material with precooled water and fed back recovered p-xylene in a mixer at a temperature of 0.degree. to 13.degree. C. to form a p-xylene-crystal-water mixture containing p-xylene crystals and water; continuously transferring the mixture produced as soon as it contains about 30% by weight p-xylene crystals into a purifying centrifuge via a dewatering filter to form a fluid phase and a p-xylene crystal slurry; separating the fluid phase further from the p-xylene crystals in a first stage of a purifying centrifuge, mixing the p-xylene crystal slurry in a second stage with a partial flow of final product, heating at about 13.degree. C. and subsequently liberating from the fluid phase still adhering, whereby the p-xylene crystals are drawn off into a heated vessel; drawing off the p-xylene crystals melted in the heated vessel as the final product with the desired purity and also drawing off a partial flow of final product, which is fed back to the second stage of the purifying centrifuge, being heated previously to a temperature of from 60.degree. to 80.degree. C., and feeding the fluid phase separated from the p-xylene crystals to the second stage of the centrifuge for recovery of additional p-xylene which becomes part of the final product stream.

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patent: 3720647 (1973-03-01), Gelbe et al.
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