Liquid-phase semihydrogenation of phenylacetylene under mild conditions has been investigated on a series of solvothermal-derived nano-TiO2 supported Pd catalysts with various TiO2 crystallite sizes in the range of 9-23 nm. As revealed by CO chemisorption and transmission electron microscopy, all the catalysts exhibited strong metal-support interaction (SMSI) when reduced at 500 degrees C. The catalysts with SMSI show remarkably high catalytic performance in terms of both hydrogenation activities (turnover frequencies (TOFs) 9.1-21.4 s(-1)) and moderate-high selectivities to styrene (86-90%) at complete conversion of phenylacetylene. Without SMSI effect (the catalysts reduced at 40 degrees C), styrene selectivity and catalytic activity depended largely on the Pd particle size in which small Pd particles (formed on small crystallite size TiO2 supports) exhibited lower phenylacetylene conversion and poor styrene selectivity. Moreover, the TOF values of the non-SMSI catalysts were similar to those reported in the literature for other supported Pd catalyst; in liquid-phase semi hydrogenation of phenylacetylene under mild conditions (TOFs 1.3-2.8 s(-1)). (C) 2009 Elsevier Inc. All rights reserved.