The deactivation behavior of a TiO2-added Pd catalyst, reduced at 773 K, for the selective hydrogenation of acetylene showed that the added TiO2 suppressed the formation of green oil and, consequently, improved the lifetime of the catalyst. The average number of carbon atoms per green oil molecule was smaller for the TiO2-added catalyst than for the Pd-only catalyst because multiply coordinated I'd sites were suppressed on the TiO2-added catalyst. The added TiO2 also retarded the sintering of Pd particles during catalyst regeneration, presumably due to the anchoring effect of TiO2, and suppressed green oil formation, even after the regeneration step. (C) 2004 Elsevier Inc. All rights reserved.