Patent ID: 6689929
Filing Date: 2004-02-10
Classification: C07C

Abstract:
A process for the production of para-xylene from a feed comprising toluene comprising:(1) subjecting the toluene feed to toluene conversion to produce a xylene-containing effluent stream comprising para-xylene, meta-xylene, ortho-xylene, ethylbenzene, unreacted toluene, and other unconverted reactants, (2) separating unreacted toluene and the other unconverted reactants from the xylene-containing effluent stream from step (1) to produce a para-xylene-containing stream comprising para-xylene, meta-xylene, ortho-xylene, and ethylbenzene and converting the para-xylene-containing stream to a gaseous mixture comprising para-xylene, meta-xylene, ortho-xylene, and ethylbenzene; and (3) subjecting the gaseous mixture to a pressure swing adsorption process for separating para-xylene from a feed comprising the gaseous mixture comprising para-xylene, meta-xylene, ortho-xylene, and ethylbenzene under substantially isothermal conditions, said pressure swing adsorption process comprising: (a) adsorbing the mixture onto an adsorbent defining non-selective voids and comprising a para-selective adsorbent capable of selectively adsorbing para-xylene at a temperature and pressure at which at least 0.01 grams of para-xylene may be adsorbed per gram of adsorbent; (b) producing a first effluent stream comprising a mixture of ortho-xylene and meta-xylene which contains no more than a total of about 25 mole percent of para-xylene; (c) selectively removing a portion of the mixture from the non-selective voids; (d) selectively desorbing para-xylene from the adsorbent by decreasing partial pressure of para-xylene; and (e) collecting a para-xylene-rich stream comprising the para-xylene from Step (d) which contains no more than a total of about 50 mole percent of meta-xylene and ortho-xylene based on total C8 aromatics.