Separation and isomerization of xylenes using zeolite membranes: a short overview

During the last 30 years, there has been a great evolution in p-xylene production technology, with many equipment improvements being instituted in the industry. Typically, these improvements bring economic as well as processing advantages to the producers. Such developments are vital, as the capital costs for process equipment to separate xylene isomers, especially into highly purified p-xylene, still remain very high. In view of this, research efforts have recently focused on the development of zeolite membranes for the separation and production of p-xylene, the precursor for the production of terephthalic acid, for which the current p-xylene world demand stands at about 86% of the production. Over a list of about 200 references, this review reports on the present state-of-the-art in p-xylene separation from lesser used isomers (o- and m-xylene) by means of MFI-type zeolite membranes, and on the most recent achievements in o/m-xylene isomerization to p-xylene using extractor-type catalytic membrane reactors. (C) 2009 Curtin University of Technology and John Wiley & Sons, Ltd.