New insights into the formation of microporous materials by in situ scattering techniques

The formation of zeolite A (LTA) in the presence of tetramethylammonium cations and CoA1PO-5 (AFI structure) in the presence of tetraethyl ammonium hydroxide was studied using time-resolved, in situ energy dispersive X-ray diffraction (EDXRD) and small angle and wide angle X-ray scattering (SAXS/WAXS) techniques. The in situ SAXS measurements show the formation of homogeneous precursors, ca. 10 nm in size, prior to the crystallization of LTA, and consumed during the crystallization. The crystal size is estimated by fitting the SAXS patterns with an equation for a cubic particle, and it is revealed that the final crystal size of the LTA depends on the synthesis temperature. The crystallisation of CoA1PO-5 occurs through the formation of poly-dispersed particles with an average size of the precursor particle of ca. 50 nm.