Synthesis of mesoporous silica gels with embedded heteropolyacids
- 169 Downloads
Silica gels containing embedded heteropolyacids were synthesized in acidic media by co-condensation of tetraethoxysilane with phosphotungstic or phosphomolybdic acids using the sol-gel technique. Surfactants dodecylamine, sodium dodecylsulfate, trimethylstearylammonium chloride, and Pluronic P123 were used as templates. The effect of the synthesis conditions on their structure and morphology was studied. All materials were mesoporous but contained micropores in their structures. Presence of bands of Keggin structures in fourier transform infrared spectroscopy spectra along with absence of X-ray diffraction patterns of crystalline heteropolyacids confirmed their fine incorporation into silica network. Particle sizes of modified materials were 500–1100 nm except for the W-containing sample obtained with trimethylstearylammonium chloride, which was significantly lower. This unusual effect was attributed to stabilization of primary silica nanoparticles by interactions between the surfactant and heteropolyacid. High ratio heteropolyacid/tetraethoxysilane resulted in partial loss of porosity. Obtained results might be used for optimization of synthesis of effective catalysts and adsorbents containing heteropolyacids in mesoporous structure.
KeywordsSilica gel Heteropolyacids Sol-gel synthesis Mesoporous materials
This research was sponsored by NATO’s Emerging Security Challenges Division in the framework of the Science for Peace and Security Programme (grant SfP 984639). Authors acknowledge support of the School of Graduate Studies of East Tennessee State University (grant E85033).
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
- 9.Kaleta W, Nowinska K. (2001) Immobilisation of heteropoly anionsPlease provide volume number for reference Kaleta and Nowinska (2001) in Si-MCM-41 channels by means of chemical bonding to aminosilane groups. Chem Commun 535–536Google Scholar
- 16.Okuhara T, Nishimura T, Misono M (1996) Novel microporous solid “superacids”: CsxH3−xPW12O40 (2≤x≤3). In: Hightower JW, Delgass WN, Iglesia E, Bell AT (eds) Studies in surface science and catalysis, vol 101. Elsevier, Amsterdam, p 581–590Google Scholar
- 17.Kozhevnikov IV (2002) Catalysis for fine chemical syntheses. Wiley, New York, Volume 2, Catalysis by polyoxometalatesGoogle Scholar
- 18.Popa A, Sasca V, Verdes O, Barvinschi P, Holclajtner-Antunović I (2014) Acidic and neutral caesium salts of 12-molybdophosphoric acid supported on SBA-15 mesoporous silica. The influence of Cs concentration and surface coverage on textural and structural properties. Mater Res Bull 50:312–322CrossRefGoogle Scholar
- 20.Kouznetsova TF, Ratko AI, Komarov VS, Eremenko SI (2008) Effect of sodium dodecylsulfate and cetylpyridinium chloride act as templates at different pH values on sorption and textural properties of mesoporous silicas. In: Innocenti P, Zub YI, Kessler VG (eds) Sol-gel methods for material processing, Dordrecht, Springer, p 337–342Google Scholar