The effect of TiO2 particle size on the characteristics of Au–Pd/TiO2 catalysts

•Au–Pd catalysts were prepared on TiO2 with average crystallite sizes 9 and 15 nm.•The size of Au–Pd alloy depended on the TiO2 crystallite size.•Electronic effect by Au–Pd alloy formation was more pronounced on the larger TiO2.•Au acted as an electronic promoter for Pd, which promoted 1-heptene hydrogenation.

The nanocrystalline TiO2 materials with average crystallite sizes of 9 and 15 nm were synthesized by the solvothermal method and employed as the supports for preparation of bimetallic Au/Pd/TiO2 catalysts. The average size of Au–Pd alloy particles increased slightly from sub-nano (< 1 nm) to 2–3 nm with increasing TiO2 crystallite size from 9 to 15 nm. The catalyst performances were evaluated in the liquid-phase selective hydrogenation of 1-heptyne under mild reaction conditions (H2 1 bar, 30 °C). The exertion of electronic modification of Pd by Au–Pd alloy formation depended on the TiO2 crystallite size in which it was more pronounced for Au/Pd on the larger TiO2 (15 nm) than on the smaller one (9 nm), resulting in higher hydrogenation activity and lower selectivity to 1-heptene on the former catalyst.