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Title: Titania-silica mixed oxides. V. Effect of sol-gel and drying conditions on surface properties

Abstract

Mesoporous titania-silica aerogels have been prepared by an alkoxide-sol-gel process with ensuing supercritical drying which involved either semicontinuous extraction using supercritical CO{sub 2} or transferring the solution-sol-gel liquid directly into the super-critical state. Surface properties of these materials were compared to those of conventionally dried titania-silica xerogel. The influence of several important preparation parameters (hydrolysis route, Ti-content, and drying method) on surface properties of the gels were investigated by temperature-programmed reaction and desorption (TPRD) of isopropanol and X-ray photoelectron spectroscopy (XPS). The information gained by these surface-sensitive methods was interpreted in the light of previous bulk structural investigations, i.e., X-ray diffraction, FTIR, FTRaman, and UV-vis spectroscopy. Up to 723 K, three TPRD peaks were identified and assigned to the different surface species in titania-silica mixed oxides found in previous structural investigations: inactive silica domains, titania domains, and highly dispersed Ti in silica (Si-O-Ti linkages). The Ti-containing surface species catalyzed dehydration of isopropanol to propene at different temperatures. Depending on the dispersion and nature of titanium oxo species on the surface of the titania-silica sol-gel mixed oxides (Si-O-Ti heteroconnectivity), significant differences in the reaction-desorption profiles were observed. All titania-silica gels showed enrichment of the surface with silica. This behavior strongly dependedmore » on the drying procedure applied. Low-temperature supercritical drying and evaporative drying yielded higher titania surface concentration (lower Si enrichment) compared to high-temperature supercritical drying. 23 refs., 8 figs.« less

Authors:
; ; ;  [1]
  1. Swiss Federal Inst. of Technology, Zurich (Switzerland)
Publication Date:
OSTI Identifier:
468694
Resource Type:
Journal Article
Journal Name:
Journal of Catalysis
Additional Journal Information:
Journal Volume: 164; Journal Issue: 2; Other Information: PBD: Dec 1996
Country of Publication:
United States
Language:
English
Subject:
40 CHEMISTRY; 36 MATERIALS SCIENCE; TITANIUM OXIDES; STRUCTURAL CHEMICAL ANALYSIS; SILICA; CHEMICAL PREPARATION; PHOTOELECTRON SPECTROSCOPY; SOL-GEL PROCESS; DESORPTION; ETHANOL; PROPANOLS; X-RAY SPECTROSCOPY; SURFACE PROPERTIES

Citation Formats

Dutoit, D C.M., Goebel, U, Schneider, M, and Baiker, A. Titania-silica mixed oxides. V. Effect of sol-gel and drying conditions on surface properties. United States: N. p., 1996. Web. doi:10.1006/jcat.1996.0399.
Dutoit, D C.M., Goebel, U, Schneider, M, & Baiker, A. Titania-silica mixed oxides. V. Effect of sol-gel and drying conditions on surface properties. United States. https://doi.org/10.1006/jcat.1996.0399
Dutoit, D C.M., Goebel, U, Schneider, M, and Baiker, A. Sun . "Titania-silica mixed oxides. V. Effect of sol-gel and drying conditions on surface properties". United States. https://doi.org/10.1006/jcat.1996.0399.
@article{osti_468694,
title = {Titania-silica mixed oxides. V. Effect of sol-gel and drying conditions on surface properties},
author = {Dutoit, D C.M. and Goebel, U and Schneider, M and Baiker, A},
abstractNote = {Mesoporous titania-silica aerogels have been prepared by an alkoxide-sol-gel process with ensuing supercritical drying which involved either semicontinuous extraction using supercritical CO{sub 2} or transferring the solution-sol-gel liquid directly into the super-critical state. Surface properties of these materials were compared to those of conventionally dried titania-silica xerogel. The influence of several important preparation parameters (hydrolysis route, Ti-content, and drying method) on surface properties of the gels were investigated by temperature-programmed reaction and desorption (TPRD) of isopropanol and X-ray photoelectron spectroscopy (XPS). The information gained by these surface-sensitive methods was interpreted in the light of previous bulk structural investigations, i.e., X-ray diffraction, FTIR, FTRaman, and UV-vis spectroscopy. Up to 723 K, three TPRD peaks were identified and assigned to the different surface species in titania-silica mixed oxides found in previous structural investigations: inactive silica domains, titania domains, and highly dispersed Ti in silica (Si-O-Ti linkages). The Ti-containing surface species catalyzed dehydration of isopropanol to propene at different temperatures. Depending on the dispersion and nature of titanium oxo species on the surface of the titania-silica sol-gel mixed oxides (Si-O-Ti heteroconnectivity), significant differences in the reaction-desorption profiles were observed. All titania-silica gels showed enrichment of the surface with silica. This behavior strongly depended on the drying procedure applied. Low-temperature supercritical drying and evaporative drying yielded higher titania surface concentration (lower Si enrichment) compared to high-temperature supercritical drying. 23 refs., 8 figs.},
doi = {10.1006/jcat.1996.0399},
url = {https://www.osti.gov/biblio/468694}, journal = {Journal of Catalysis},
number = 2,
volume = 164,
place = {United States},
year = {1996},
month = {12}
}