AN INVESTIGATION ON PD C INDUSTRIAL CATALYSTS FOR THE PURIFICATION OFTEREPHTHALIC ACID/

Commercial 0.5% Pd/C catalysts for the production of purified terephth alic acid (PTA) have been investigated by several physical techniques (SEM-EDS, CO chemisorption, XRD) and by activity tests performed in co nditions strictly similar to those of industrial operation. These cata lysts show a strongly external Pd distribution, pointing to high Pd co ncentrations in the outer layers of the carrier It was found that Pd s inters very easily and that a rough proportionality exists between cat alytic activity and Pd surface area. Pd sintering was shown to be an i mportant cause of deactivation for PTA catalysts. However, in some cas es deactivation occurs by sulphur poisoning, with the formation of a P d sulphide (Pd4S). (C) 1998 Elsevier Science B.V. All rights reserved.