skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: An investigation of molecular templating in amorphous silicas by cross-polarization NMR spectroscopy

Abstract

The precise pore sizes defined by crystalline zeolite lattices have led to intensive research on zeolite membranes. Unfortunately, zeolites have been extremely difficult to prepare in a defect-free thin film form needed for membrane flux and selectivity. The authors introduced tetrapropylammonium (TPA), a structure-directing agent for zeolite ZSM-5, into a silica sol and exploit the development of high solvation stresses to create templated amorphous silicas with pore apertures similar in size to those of ZSM-5. Silicon and carbon NMR experiments were performed to evaluate the efficacy of the templating approach. The {sup 29}Si NMR spectrum of the silica matrix was observed by an intermolecular cross-polarization experiment involving the {sup 1}H nuclei of TPA and the {sup 29}Si nuclei in the silica matrix. The efficiency of the cross-polarization interaction was used to investigate the degree to which the matrix formed a tight cage surrounding the template molecule. Bulk xerogels, prepared by gelation and slow drying of the corresponding sols, exhibited only weak interactions between the two sets of nuclei. Thin film xerogels, where drying stresses are greater, exhibited significantly increased interactions. Intramolecular cross-polarization experiments between the {sup 1}H and {sup 13}C nuclei of the template molecule demonstrated that much of themore » increased efficiency was a result of reduced rotational mobility of the TPA molecule.« less

Authors:
; ; ;
Publication Date:
Research Org.:
Univ. of Missouri, Rolla, MO (US)
OSTI Identifier:
20017483
Resource Type:
Journal Article
Journal Name:
Journal of Physical Chemistry B: Materials, Surfaces, Interfaces, amp Biophysical
Additional Journal Information:
Journal Volume: 104; Journal Issue: 2; Other Information: PBD: 20 Jan 2000; Journal ID: ISSN 1089-5647
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; ZEOLITES; AMMONIUM COMPOUNDS; MEMBRANES; SOL-GEL PROCESS

Citation Formats

Click, C A, Assink, R A, Brinker, C J, and Naik, S J. An investigation of molecular templating in amorphous silicas by cross-polarization NMR spectroscopy. United States: N. p., 2000. Web. doi:10.1021/jp992762q.
Click, C A, Assink, R A, Brinker, C J, & Naik, S J. An investigation of molecular templating in amorphous silicas by cross-polarization NMR spectroscopy. United States. https://doi.org/10.1021/jp992762q
Click, C A, Assink, R A, Brinker, C J, and Naik, S J. 2000. "An investigation of molecular templating in amorphous silicas by cross-polarization NMR spectroscopy". United States. https://doi.org/10.1021/jp992762q.
@article{osti_20017483,
title = {An investigation of molecular templating in amorphous silicas by cross-polarization NMR spectroscopy},
author = {Click, C A and Assink, R A and Brinker, C J and Naik, S J},
abstractNote = {The precise pore sizes defined by crystalline zeolite lattices have led to intensive research on zeolite membranes. Unfortunately, zeolites have been extremely difficult to prepare in a defect-free thin film form needed for membrane flux and selectivity. The authors introduced tetrapropylammonium (TPA), a structure-directing agent for zeolite ZSM-5, into a silica sol and exploit the development of high solvation stresses to create templated amorphous silicas with pore apertures similar in size to those of ZSM-5. Silicon and carbon NMR experiments were performed to evaluate the efficacy of the templating approach. The {sup 29}Si NMR spectrum of the silica matrix was observed by an intermolecular cross-polarization experiment involving the {sup 1}H nuclei of TPA and the {sup 29}Si nuclei in the silica matrix. The efficiency of the cross-polarization interaction was used to investigate the degree to which the matrix formed a tight cage surrounding the template molecule. Bulk xerogels, prepared by gelation and slow drying of the corresponding sols, exhibited only weak interactions between the two sets of nuclei. Thin film xerogels, where drying stresses are greater, exhibited significantly increased interactions. Intramolecular cross-polarization experiments between the {sup 1}H and {sup 13}C nuclei of the template molecule demonstrated that much of the increased efficiency was a result of reduced rotational mobility of the TPA molecule.},
doi = {10.1021/jp992762q},
url = {https://www.osti.gov/biblio/20017483}, journal = {Journal of Physical Chemistry B: Materials, Surfaces, Interfaces, amp Biophysical},
issn = {1089-5647},
number = 2,
volume = 104,
place = {United States},
year = {Thu Jan 20 00:00:00 EST 2000},
month = {Thu Jan 20 00:00:00 EST 2000}
}