Porosity of micro/mesoporous composites

The porous structure of a series of micro/mesoporous composite materials synthesized from a mixture of precursor solutions generally used for preparation of Beta microporous molecular sieves and pure mesoporous MCM-48 silica has been investigated. A short crystallization time of the precursor solutions results in the formation of small crystalline zeolitic domains, while after prolonged synthesis the development of larger Beta zeolitic crystallites is observed. An analysis of nitrogen isotherms based on the αs-method has revealed a relationship between the synthesis conditions and the development of both micro- and mesoporosity of these materials. With increasing the size of the zeolitic domains the mesoporosity of the composite materials decreases while the microporosity is increased. The structural features of these composites determined by XRD corroborate with the nitrogen sorption results.