Sintering of Pd Catalyst Particles on SiO2−TiO2 Carrier Particles of Different Mixing Ratios

Initial sintering rates of nearly monodisperse Pd model catalyst particles on silica, titania, and mixtures thereof were measured as a function of temperature on the time scale of a few seconds in the gas phase. Support particles and active phase were synthesized by aerosol based techniques permitting a high degree of experimental control. It was found that Pd particles sintered more slowly on silica than on titania. This is attributed to the higher surface roughness of the SiO 2 . Adding a small amount of the second oxide phase to either silica or titania increased the surface roughness and thus also the thermal stability of the Pd. This effect was more pronounced for titania. High amounts of the second oxide phase did not further enhance the stability, because phase separation occurred and core−shell structures with similar surface morphologies were formed in the carriers.