Conclusions
0.04%-Pd/PHSNs and TiO2-modified Pd/PHSNs egg-shell nano-catalysts were prepared by impregnation method using porous hollow silica nanoparticles (PHSNs) as support. TEM, SEM, EDS and XRD were employed to characterize the as-prepared catalysts, showing that Pd was loaded evenly on PHSNs and TiO2 was loaded on the active Pd particles as a catalyst modifier. Both catalysts showed good catalytic performance, for conversion rate and ethylene selectivity of the selective hydrogenation of acetylene to ethylene when the catalysts were reduced at proper temperatures and relatively short time to avoid severe sintering and aggregating of the metal particles at high reduction temperatures or long reduction time. Adding a proper amount of Ti to modify the Pd/PHSNs catalyst would promote its ethylene selectivity, while adding too much or too less Ti may result in deterioration of its catalytic performance.