Vanadia-silica low-temperature aerogels: Influence of aging and vanadia loading on structural and chemical properties

doi:https://doi.org/10.1021/cm9504293

Title: Vanadia-silica low-temperature aerogels: Influence of aging and vanadia loading on structural and chemical properties

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Abstract

Vanadia-silica mixed oxides were prepared via the sol-gel method involving acid catalysis together with prehydrolysis in order to achieve matching of the reactivities of vanadium (V) oxide triisopropoxide and tetraethoxysilicon(IV) precursors. Gelation was forced by the addition of basic solution. The as-received gels were supercritically dried by semicontinuous extraction with supercritical CO{sub 2} at 313 K (low-temperature aerogels). The effects of composition, aging, and calcination temperature on the chemical, structural, and textural properties of the solids were investigated. The oxides were characterized by N{sub 2} physisorption, XRD, vibrational spectroscopy, thermal analysis, UV-vis,and {sup 51}V NMR. The low-temperature vanadia-silica aerogels were mesoporous and highly disperse. The increasing V content from 5 to 20 wt % nominal V{sub 2}O{sub 5} caused a gradual decline in V dispersion. For 30 wt % {open_quotes}V{sub 2}O{sub 5}{close_quotes} the continuous formation of V-O-V connectivity resulted in crystallization of V{sub 2}O{sub 5}. The effect of aging to basic medium confined to the textural properties, significantly increasing BET surface area and especially pore volume. The prepared aerogels revealed a marked lack of stability against both apolar solvents in the presence of peroxides and polar solvents. The marked thermal stability in air at {le}873 K, however, combined with mesoporositymore »« less

Authors:

Dutoit, D C.M.; Schneider, M; Fabrizioli, P; Baiker, A ^[1]

Swiss Federal Inst. of Technology, Zuerich (Switzerland)

Publication Date:: 1996-03-01

OSTI Identifier:: 285008

Resource Type:: Journal Article

Journal Name:: Chemistry of Materials

Additional Journal Information:: Journal Volume: 8; Journal Issue: 3; Other Information: PBD: Mar 1996

Country of Publication:: United States

Language:: English

Subject:: 36 MATERIALS SCIENCE; VANADIUM OXIDES; MICROSTRUCTURE; SILICA; X-RAY DIFFRACTION; NUCLEAR MAGNETIC RESONANCE; CRYSTAL STRUCTURE; CHEMICAL PROPERTIES; CALCINATION; CHEMICAL COMPOSITION; ADSORPTION; ABSORPTION SPECTROSCOPY; THERMAL ANALYSIS; PORE STRUCTURE; CATALYSTS

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                    Dutoit, D C.M., Schneider, M, Fabrizioli, P, and Baiker, A. Vanadia-silica low-temperature aerogels: Influence of aging and vanadia loading on structural and chemical properties.  United States: N. p., 1996. 
        Web.  doi:10.1021/cm9504293.

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                    Dutoit, D C.M., Schneider, M, Fabrizioli, P, & Baiker, A. Vanadia-silica low-temperature aerogels: Influence of aging and vanadia loading on structural and chemical properties.  United States.  https://doi.org/10.1021/cm9504293

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                    Dutoit, D C.M., Schneider, M, Fabrizioli, P, and Baiker, A. Fri .  
        "Vanadia-silica low-temperature aerogels: Influence of aging and vanadia loading on structural and chemical properties".  United States.  https://doi.org/10.1021/cm9504293.

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@article{osti_285008,

  title        = {Vanadia-silica low-temperature aerogels: Influence of aging and vanadia loading on structural and chemical properties},

  author       = {Dutoit, D C.M. and Schneider, M and Fabrizioli, P and Baiker, A},

  abstractNote = {Vanadia-silica mixed oxides were prepared via the sol-gel method involving acid catalysis together with prehydrolysis in order to achieve matching of the reactivities of vanadium (V) oxide triisopropoxide and tetraethoxysilicon(IV) precursors. Gelation was forced by the addition of basic solution. The as-received gels were supercritically dried by semicontinuous extraction with supercritical CO{sub 2} at 313 K (low-temperature aerogels). The effects of composition, aging, and calcination temperature on the chemical, structural, and textural properties of the solids were investigated. The oxides were characterized by N{sub 2} physisorption, XRD, vibrational spectroscopy, thermal analysis, UV-vis,and {sup 51}V NMR. The low-temperature vanadia-silica aerogels were mesoporous and highly disperse. The increasing V content from 5 to 20 wt % nominal V{sub 2}O{sub 5} caused a gradual decline in V dispersion. For 30 wt % {open_quotes}V{sub 2}O{sub 5}{close_quotes} the continuous formation of V-O-V connectivity resulted in crystallization of V{sub 2}O{sub 5}. The effect of aging to basic medium confined to the textural properties, significantly increasing BET surface area and especially pore volume. The prepared aerogels revealed a marked lack of stability against both apolar solvents in the presence of peroxides and polar solvents. The marked thermal stability in air at {le}873 K, however, combined with mesoporosity and high V dispersion, render these solids promising catalysts for gas-phase reactions. 58 refs., 10 figs., 4 tabs.},

  doi          = {10.1021/cm9504293},

  url          = {https://www.osti.gov/biblio/285008},
  journal      = {Chemistry of Materials},
number       = 3,

  volume       = 8,

  place        = {United States},

  year         = {1996},

  month        = {3}

}

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