Modification of Silica Gel by Heteropolyacids

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Silica gels containing incorporated heteropolyacids (HPAs) were synthesized in acidic media by co-condensation of tetraethoxysilane (TEOS) with phosphotungstic or phosphomolybdic acids using the sol-gel technique. The effect of the synthesis conditions on their structure and morphology was studied. Yields of modified materials were somewhat lower compared to non-modified silica gels. All materials were mesoporous but contained micropores in their structures. Presence of bands of Keggin’s structures in FT-IR spectra along with absence of XRD patterns of crystalline HPAs 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 HPA. High ratio HPA/TEOS resulted in partial loss of porosity. Obtained results might be used for optimization of synthesis of effective catalysts and adsorbents containing HPAs in mesoporous structure.

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Periodical:

Edited by:

Prof. K.M. Gupta, Prof. Donato Firrao, Prof. Hao Gong

Pages:

126-132

DOI:

10.4028/www.scientific.net/KEM.689.126

Citation:

O. Adetola et al., "Modification of Silica Gel by Heteropolyacids", Key Engineering Materials, Vol. 689, pp. 126-132, 2016

Online since:

April 2016

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$38.00

* - Corresponding Author

[1] T. Okuhara, Water-tolerant solid acid catalysts. Chem. Rev., 102, (2002), 3641-3665.

[2] A.D. Newman, A.F. Lee, K. Wilson, N.A. Young, On the active site in H3PW12O40/SiO2 catalysts for fine chemical synthesis, Catal. Lett., 102, (2005), 45-50.

DOI: 10.1007/s10562-005-5201-y

[3] L. Yang, Y. Qi, X. Yuan, J. Shen, J. Kim, Direct synthesis, characterization and catalytic application of SBA-15 containing heteropolyacid H3PW12O40, J. Mol. Catal. A: Chem., 229, (2005), 199-205.

DOI: 10.1016/j.molcata.2004.11.024

[4] K. Li, J. Hu, W. Li, F. Ma, L. Xu, Y. Guo, Design of mesostructured H3PW12O40-silica materials with controllable ordered and disordered pore geometries and their application for the synthesis of diphenolic acid, J. Mater. Chem., 19, (2009).

DOI: 10.1039/b910416j

[5] Y. Guo, K. Li, X. Yu, J.H. Clark, Mesoporous H3PW12O40-silica composite: Efficient and reusable solid acid catalyst for the synthesis of diphenolic acid from levulinic acid, Appl. Catal. B: Environ., 81, (2008), 182-191.

DOI: 10.1016/j.apcatb.2007.12.020

[6] B. -B. Dong, B. -B. Zhang, H. -Y. Wu, S. -D. Li, K. Zhang, X. -C. Zheng, Direct synthesis, characterization and application in benzaldehyde oxidation of HPWA-SBA-15 mesoporous catalysts, Micropor. Mesopor. Mater., 176, (2013), 186-193.

DOI: 10.1016/j.micromeso.2013.03.051

[7] X. Sheng, J. Kong, Y. Zhou, Y. Zhang, Z. Zhang, S. Zhou, Direct synthesis, characterization and catalytic application of SBA-15 mesoporous silica with heteropolyacid incorporated into their framework, Micropor. Mesopor. Mater., 187, (2014), 7-13.

DOI: 10.1016/j.micromeso.2013.12.007

[8] P. -Y. Hoo, A. Z. Abdullah, Direct synthesis of mesoporous 12-tungstophosphoric acid SBA-15 catalyst for selective esterification of glycerol and lauric acid to monolaurate, Chem. Eng. J., 250, (2014), 274-287.

DOI: 10.1016/j.cej.2014.04.016

[9] T. Okuhara, T. Nishimura, M. Misono, Novel microporous solid superacids,: CsxH3−xPW12O40 (2≤x≤3), in: J.W. Hightower, W.N. Delgass, E. Iglesia, A.T. Bell (Eds. ); Studies in Surface Science and Catalysis, Volume 101, Elsevier, Amsterdam, 1996, pp.581-590.

DOI: 10.1016/s0167-2991(96)80269-2

[10] I. V. Kozhevnikov, Catalysis for Fine Chemical Syntheses, Volume 2, Catalysis by Polyoxometalates, Wiley, New York, (2002).

[11] A. Popa, V. Sasca, O. Verdes, P. Barvinschi, I. Holclajtner-Antunović, Acidic and neutral cesium 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, (2014).

DOI: 10.1016/j.materresbull.2013.11.015

[12] A. J. Bridgeman, Density functional study of the vibrational frequencies of α-Keggin heteropolyanions, Chem. Phys., 287, (2003), 55-69.

DOI: 10.1016/s0301-0104(02)00978-3

[13] D. Zhao, J. Feng, Q. Huo, N. Melosh, G.H. Fredrickson, B.F. Chmelka, G.D. Stucky, Triblock copolymer syntheses of mesoporous silica with periodic 50 to 300 angstrom pores, Science, 279, (1998), 548-552.

DOI: 10.1126/science.279.5350.548

[14] S. Ruthstein, V. Frydman, S. Kababya, M. Landau, D. Goldfarb, Study of the formation of the mesoporous material SBA-15 by EPR spectroscopy, J. Phys. Chem. B, 107, (2003), 1739-1748.

DOI: 10.1021/jp021964a

[15] P. Feng, X. Bu, D.J. Pine, Control of pore sizes in mesoporous silica templated by liquid crystals in block copolymer-cosurfactant-water systems, Langmuir, 16, (2000), 5304-5310.

DOI: 10.1021/la991444f

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