Activated silica sols.characterization

Figure 3.65. Characterization of activated silica sols. Solid Unis sot A, 1% salt-free sol made by removing sodium from sodium silicate by ion e.xchange and raising the pH to 5. Dashed lines sol B, 1.5% SiO. made by acidifying sodium silicate solution to pH 8.5 and diluting after 0.9 day. Sols aged at 25°C. [From Okura and Goto (19-4).]...

This work is about the development of a new porous composite material [18] which consists of a silica network intercrossed with a carbon network of high activity, being both networks independent and self supported. This new composite was obtained by the sol-gel method, it has an open pore size distribution curve characterized by a big sharpened zone near the 1000 A diameter, and it possess a high thermal stability. 

Amorphous silica-aluminas are high-surface-area materials that can be prepared by co-precipitation or sol-gel techniques from solutions containing sodium silicate and sodium aluminate. Because of their high surface acidities they are potent hydrocarbon cracking catalysts, but their activity is strongly dependent on the silica/alumina ratio and on the method of preparation. Solid-state NMR studies have addressed the structural origins of these variations and have served to characterize the surface acidities. 

Green W.H., Le K.P., Grey J., Au T.T., Sailor M.J. White phosphors from a silicate-carboxylate sol-gel precursor that lack metal activator ions. Science 1997 276 1826-1828 Harreld J.H., Ebina T., Tsubo N., Stucky G. Manipulation of pore size disUibutions in silica and ormosil gels dried under ambient pressure conditions. J. Non-Cryst. Sohds 2002 298 241-251 Hazenkamp M.F., Blasse G. Rare-earth ions adsorbed onto porous ass luminescence as a characterizing tool. Chem. Mater. 1990 2 105-110... 

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