Synthesis of nanostructured mesoporous zirconia using CTMABr-ZrOCl2•8H2O systems:: a kinetic study of synthesis mechanism

A systematic kinetic study of mesoporous zirconia formation has been performed in order to optimize the synthesis conditions without addition of structure stabilizing agents such as sulfate or phosphate anions. We have investigated in particular the effect of synthesis time and temperature. On the basis of TEM, SEM, XRD and N-2 adsorption-desorption results, a synthesis mechanism has been proposed. It is observed that at low temperature or for short durations at higher temperatures, the obtained materials are first supermicroporous, then if hydrothermal treatment is prolonged, a breakdown of the walls separating adjacent pores allows the transformation to mesopores. The obtained materials have a uniform pore size and their surface can reach 300 m(2)/g. The channel array is, at least part of samples, wormlike. However, if hydrothermal treatment is performed at too high temperature or for too long durations, mesoporous compounds are no longer obtained, but thermodynamically more stable crystalline zirconium oxides with very low specific surface area, namely the tetragonal and monoclinic forms, are the final phases. (C) 2001 Published by Elsevier Science Ltd.