Zirconia with Defined Particle Morphology and Hierarchically Structured Pore System Synthesized via Combined Exo- and Endotemplating

摘要

Highly porous zirconia with defined particle morphology can be prepared by impregnation of spherical activated carbon as an exotemplate with a zirconia nano-particle sol. The resulting zirconia spheres show a particle size distribution between 0.2 and 0.4 mm and exhibit high specific surface areas and specific pore volumes up to 104m~2g~(-1) and 0.56 cm~3g~(-1), respectively. Addition of a triblock-copolymer (TBC) as an endotemplate during the synthesis leads to the formation of an additional pore system. The corresponding spherical zirconia products possess a hierarchically structured pore system with a bimodal pore size distribution with maxima at ca. 3 and 20 nm. The relative fraction of pores originating from the endotemplate can be varied by changing the endotemplate content in the zirconia nanoparticle sol. The presence of the TBC also has an influence on the specific surface area and the specific pore volume. Using the ratio of TBC to zirconium of n_(TBC)_(Zr)= 0.027, a material can be prepared that exhibits a specific surface area and a specific pore volume of 161 m~2g~(-1) and 0.62 cm~3g~(-1) respectively. These values are more than twice as high as for zirconia prepared by a conventional precipitation method (68 m~2g~(-1) and 0.11 cm~3g~(-1) respectively).