Thermochemistry of Surfactant-Templating of USY Zeolite

With the aim of understanding the thermochemistry of the introduction of mesoporosity in zeolites by using surfactants, high temperature oxide melt solution calorimetry was used to determine the change in the enthalpy of formation of USY zeolite before and after the introduction of mesoporosity. Our results confirm that this process only slightly destabilizes the zeolite by the additional surface area. However, this can be overcome by the stabilizing effect of the interactions between the surfactant and the zeolite framework.     

The Energetics of Surfactant‐Templating of Zeolites

Mesoporosity can be conveniently introduced into zeolites by treating them in basic surfactant solutions. The apparent activation energy involved in the formation of mesopores in USY by surfactant‐templating was determined using a combination of in situ synchrotron X‐ray diffraction and ex situ gas adsorption. Additionally, techniques such as pH measurement and thermogravimetry/differential thermal analysis were employed to determine OH^? evolution and cetyltrimethylammonium ion (CTA⁺) uptake during the development of mesoporosity, thereby providing information about the different steps involved. The combination of both in situ and ex situ techniques has allowed determination of the apparent activation energies of the different processes involved in the mesostructuring of USY zeolites for the first time. Apparent activation energies are of the same order of magnitude (30–65 kJ mol^?1) as those involved in the crystallization of zeolites. Hence, important mechanistic insight into the surfactant‐templating method was obtained.