Separation of ethylbenzene and p-xylene using extractive distillation with p-dinitrobenzene

Though p-xylene derived from naphtha reformate is in high demand as a raw material in the production of polyesters and polyethylene terephthalates, its separation from the FCC reformate is not easy due to close boiling points among the components in the reformate. When a proper solvent for the p-xylene separation is available, an extractive distillation can be applied in the separation. Currently the separation utilizes an adsorption process requiring a large amount of costly adsorbent and a desorption process followed by distillation. In the proposed extractive distillation here, p-dinitrobenzene has been utilized to improve the separation of p-xylene from its ethylbenzene mixture. The VLE data of the ternary mixture estimated with the UNIFAC were compared to those computed from molecular simulation to show their reliability. An extractive distillation and solvent recovery were applied to obtain 99.6% purity p-xylene with 99.1% recovery. The economics of the proposed process demonstrates its comparability to the existing Parex process.