Confined space synthesis. A novel route to nanosized zeolites

Confined space synthesis is a novel method in zeolite synthesis. It involve s crystallization of the zeolite inside the pore system of an inert mesopor ous matrix. In this way it is possible to prepare nanosized zeolites with a controlled size distribution by proper choice of the inert matrix. Here, c onfined space synthesis was adopted to prepare nanosized ZSM-5, zeolite Bet a, zeolite X, and zeolite A with tailored crystal size distributions using mesoporous carbon blacks as inert matrices. All zeolites were characterized by X-ray powder diffraction, transmission electron microscopy, and nitroge n adsorption/desorption prior to and after removal of the carbon matrix. ZS M-5 with Si/Al ratios of 50, 100, and infinity (silicalite-l) were synthesi zed with controlled average crystal sizes in the range 20-75 nm. Nanosized zeolite Beta (7-30 nm), zeolite X (22-60 nm), and zeolite A (25-37 nm) were prepared similarly. Removal of the carbon matrix by controlled combustion allows a convenient method for isolation of the pure and highly crystalline zeolites. Therefore, confined space synthesis appears to be an attractive method for preparation of zeolites with a controlled size distribution.