Welcome to the new version of CaltechAUTHORS. Login is currently restricted to library staff. If you notice any issues, please email coda@library.caltech.edu
Published January 1999 | public
Journal Article

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

Abstract

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.

Additional Information

© 1999 American Chemical Society. Received March 25, 1998. Revised Manuscript Received October 14, 1998. Publication Date (Web): December 23, 1998. The SAXS/WAXS experiments were performed by an EPSRC grant at the Daresbury Synchrotron Radiation Source, where good help was provided by Dr. B. U. Komanschek. USAXS measurements were performed at the European Synchrotron Radiation Facility under Grants SC-138 and SC-202. We thank Dr. O. Diat for installing and perfectly aligning the Bonse-Hart setup. Dr. P. J. Kooyman of the National Centre for High Resolution Electron Microscopy, Delft University of Technology, Delft, The Netherlands, is acknowledged for performing the electron microscopy investigations. The work at CalTech was partially supported by the Chevron Research and Technology Company.

Additional details

Created:
August 19, 2023
Modified:
October 17, 2023