Реферат: O.V. Gorbunovaa,b, O.N. Baklanovaa, T.I. Gulyaevaa, M.V. Trenikhina a) Institute of Hydrocarbons Processing SB RAS, Omsk, Russia b) Omsk State Technical University, Omsk, Russia A significant number of studies are devoted to the development of synthetic methods those allow to regulate the pore size and pore morphology of the silica. Sol-gel synthesis in the presence of different structure directing agents (SDA) is the most common method to produce silica having specific characteristics of the porous structure [1-3]. Today, complicated amphiphilic molecules, those are capable of forming micelles and more complex spatial structures in solution, are usually used as SDA. In this study, we used nonionic, linear, water-soluble biodegradable polymer – polyethylene glycol (PEG) as SDA. It is known that PEG (i) reduces the dielectric constant of the solvent, (ii) affects the hydrolysis of the silica precursor [4], and (iii) form the macromolecules fluctuation network above some critical concentration and flocculate silica particles. These properties of PEG are proposed to control the textural characteristics of the silica obtained in the sol-gel synthesis [5]. Sample preparation procedure is examined in details in the paper [5]. The nitrogen adsorption-desorption isotherms at 77.4 K for the calcined samples were obtained with ASAP-2020M (Micromeritics) using standard continuous procedures. Additionally, we used STA-449C Jupiter (Netzsch) to determine the amount of PEG in the SiO2-PEG composites after drying. To analyze the mechanism of formation and morphology of the obtained silica we use a solid state 29Si NMR spectroscopy and high resolution transmission electron microscopy (JEM- 2100, JEOL). We address the effect of PEG molecular weight (400 to 200,000) and its concentration (in the range of 0.0001 to 0.1 mol/L) on a porous structure of the silica materials. Figure 1. Textural diagram – the silica porous structure as function of PEG molecular weight and concentration of the solutions. The dot line has no physical meaning and is only guide for the eyes. All the obtained results are generalized in the diagram showing the dependence of silica porous structure on molecular weights and the solution concentrations (Fig.1). It is observed that using the solution of PEG 1300 and less the mesoporous silica was formed, independently of the concentration. When the diluted and concentrated solutions of PEG-3000 and more are used, it produces also the mesoporous materials. In the field of transitional concentrations (1-12% mass) of PEG the microporous silica with fraction of micropores equals 90-95% is generated. We hope that our findings extend the understanding the mechanisms of silica structure formation in presence of SDA and open up some new possibilities of their application. References: [1] N.K. Raman, M.T. Anderson, C.J. Brinker, Chemistry of Materials 8 (1996) 1682. [2] C.-C. Ting, H.-Y. Wu, A. Palani, A.S.T. Chiang, H.-M. Kao, Microporous and Mesoporous Materials 116, (2008) 323. [3] G.N. Shao, D.V. Quang, H.T. Kim, Applied Surface Science 287 (2013) 84. [4] M.S.W. Vong, N. Bazin, E.A. Sermon, Journal of Sol-Gel Science and Technology 8 (1997) 499. [5] O.V. Gorbunova, O.N. Baklanova, T.I. Gulyaeva, M.V. Trenikhin, V.A. Drozdov, Microporous and Mesoporous Materials 190 (2014) 146.

Библиографическая ссылка: Gorbunova O.V. , Baklanova O.N. , Gulyaeva T.I. , Trenikhin M.V.
Sol-gel synthesis of porous silica with polyethylene glycol
Ninth International Symposium “Effects of Surface Heterogeneity in Adsorption and Catalysis on Solids” 17-23 Jul 2015