Thermal and mechanical stability of micelle-templated silica supports for catalysis

Thermal and mechanical properties of hexagonal micelle-templated silica (MT S) (Eke MCM-41, SBA-3, SBA-15) are critical features for their application as catalysts and catalyst supports. Care should be taken in the interpretat ion of catalytic results which strongly depend on MTS stability. A decrease in conversion of more than 60% in a reaction of n-hexadecane isomerization has been observed by compressing NITS beyond a critical crushing pressure. Stability data have already been reported in literature, but they are extr emely scattered, and can only be understood if the synthesis conditions whi ch control the properties of NITS are taken into account. We show in this s tudy that thermal stability is strongly dependent on wall thickness, a prop erty which can be controlled by adjusting the alkalinity and the surfactant /silica ratio in the synthesis. The crushing of MTS under uniaxial compress ion follows the same mechanism as macroscopic hexagonal honeycomb structure . Their crushing strength varies as the square of the ratio between wall th ickness and cell parameter. (C) 2001 Elsevier Science B.V. All rights reser ved.