SAXS and USAXS Investigation on Nanometer-Scaled Precursors in Organic-Mediated Zeolite Crystallization from Gelating Systems

• Published in: Chemistry of materials Vol. 11; no. 1; pp. 36 - 43
• Main Authors: de Moor, Peter-Paul E. A, Beelen, Theo P. M, van Santen, Rutger A, Tsuji, Katsuyuki, Davis, Mark E
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 01.01.1999
• Subjects: Chemistry; Colloidal gels. Colloidal sols; Colloidal state and disperse state; Exact sciences and technology; General and physical chemistry; Ion-exchange; Surface physical chemistry; Zeolites: preparations and properties; Silica gel; Zeolite; Experimental study; Colloid particle; Molecular sieve; Crystallization
• ISSN: 0897-4756; 1520-5002
• DOI: 10.1021/cm9807079

The formation of precursor particles in the crystallization of zeolites from gelating systems has been studied using X-ray scattering at small angles. The crystallization of Si−MFI using trimethylene-bis(N-hexyl, N-methyl-piperidinium) as the structure-directing agent shows the formation of two categories of precursors:  gel particles and nanometer-scaled primary units. The size of the primary units for the crystallization of Si−MFI is found to be 2.8 nm both for gelating and nongelating systems using different structure-directing agents. Zeolites Si−BEA and Si−MTW have been prepared using the same organic (trimethylene-bis(N-benzyl, N-methyl-piperidinium)) at different concentrations. Primary units with a size of 2.6 nm are found to be present in the synthesis of Si−BEA, while their size is 1.5 nm in the synthesis mixture directing to Si−MTW. Our data suggest that the nanometer-scaled primary units are specific for the zeolite topology formed.