XAFS Characterization of Co/ZrO₂ Aerogel Ultrafine Particle Catalysts

The series of Co/ZrO₂ catalysts with different particle size and cobalt dispersion have been prepared by the supercritical fluid drying and conventional impregnation methods. The Structure of cobalt oxide for Co/ZrO₂ aerogel ultrafine catalysts with higher surface area is difficult to ascertain from X-ray diffraction.XANES and EXAFS results show that the form of cobalt oxide is CoO for Co/ZrO₂ aerogel ultrafine catalyst as prepared and the form is Co₃O₄, after it is calcined at 450℃ in air because the dispersed state CoO is castly oxidized.Compared with Co/ZrO₂ catalysts prepared by the impregnahon method, the neighbor coordination surrounding of aerogel ultrafine catalysts has significant change. As the surface area for these catalysts increases gradually, the particle size of ZrO₂ support decreases, the cobalt dispersion increases and the particle size of cobalt oxide decrease, the number of Co neighbors decreases and the disorder factor has a tendency to increase.