Effect of Support Crystallite Size on Catalytic Activity and Deactivation of Nanocrystalline ZnAl2O4-Supported Pd Catalysts in Liquid-Phase Hydrogenation

The catalytic activity and deactivation of nanocrystalline ZnAl₂O₄-supported Pd catalysts were investigated for the liquid-phase hydrogenation under mild conditions. Nanocrystalline ZnAl₂O₄ spinels with average crystallite size between 8 and 33 nm were synthesized by the solvothermal method in toluene. Higher turnover frequencies for 1-heptyne hydrogenation and less deactivation due to Pd leaching were obtained for the Pd/ZnAl₂O₄-33 nm catalyst. XPS and ESR results suggest that the presence of defects in larger crystallite size ZnAl₂O₄ resulted in higher Pd dispersion and stronger interaction between Pd and the support.