Meso-macroporous zirconia

In comparison with the materials synthesized in the presence of surfactants, the surface area of the hierarchically porous zirconium oxides obtained via the self-formation phenomenon is relatively lower. Furthermore, the synthesis temperature can affect the crystallinity of the final product [124,139]. Upon increase of the hydrothermal treatment temperature to 130 °C (generally reported to be 60-80 °C), thermally stable meso-macroporous zirconias with a nanocrystalline framework were prepared by using a mixture of amphiphilic block copolymer P123 and poly(ethylene oxide) surfactant Brij 56. 

The zirconia meso-macroporous particles used as catalyst support in this work have a size of around 10pm [7,8]. The synthesized zirconia particles contain regular arrays of macropores having a diameter range from 300 to 500 nm. The hollow macrochannels are always orthogonal to the face of the monolithic particle. Moreover, macroporous walls are mesostructured with a disordered wormhole like assembly of meso/micropores into macroporous framework. 

This method allows independent control over both the macropores, which are determined by the emulsion droplets in the first step of the process, and the mesopores, by the supramolecular self-assembly in the second step. Therefore, the two templating systems do not interfere vhth each other, and consequently the meso-and macro-structures can be optimized separately [21]. Inorganic oxides, such as silica, titania and zirconia, were obtained by this two-step process. The bimodal distribution of pores was characterized by highly ordered mesopores (5-10 nm) and by interconnected macropores (0.1 to 5 p,m). These materials possess high pore volumes (17 cm g ) and specific surface areas, as determined by the BET method applied to the nitrogen adsorption isotherm, of between 250 and 750 The... 

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