Preparation of SiO₂-Al₂O₃ Gels from Tetraethoxysilane and Aluminum Chloride

Abstract

A new method for preparing SiO2-Al2O3 gels from aque ous solutions of tetraethoxysilane and aluminum chlo ride was investigated.Addition of propylene oxide to the solutions promoted gelation reaction, yielding translucent gels. It was found that the 4-coordinated Al incorporated in the framework of the gels was formed without heat treatment.Residual chloride ions were removed from the gels by heating. The gels ob tained had large surface areas and were presumed to be homogeneous.

A general epoxide-assisted sol–gel route for the synthesis of metal oxide–silica composites and silicates ultrafine particles

“…(1), the epoxide consumes protons from the aqua complexes [M(H 2 O) x ] n+ , which promotes the hydrolysis and condensation of the complexes resulting in the formation of a gel. This method has been proven successful for the preparation of metal oxides [12][13][14][15][16][17][18][19][20][21][22][23].…”

Advances in monolithic porous materials tailored in liquid media: around inorganic oxides and organic polymers

“…Other strategies to reduce the reactivity employ the chelating agents such as ¢-diketones 7),32) to stabilize the monomer by coordinating to the titanium, or gradually supplying water as the byproduct of esterification of acid and alcohol. 34) The outstanding progress for homogeneous network formations of metal oxides was established by Itoh et al 35) and Gash et al 36) from ionic precursors, in which hydrated metal ions undergo hydrolysis and condensation under the co-presence of a proton scavenger. A stable metal salt is dissolved in water to form aqua complex, and subsequent addition of an epoxide (the proton scavenger, such as propylene oxide) consumes protons from the acidic hydrated metal, which promote further hydrolysis and olation/oxolation-based polycondensation under an increasing JCS-Japan pH condition.…”

Development of Non-Siliceous Porous Materials and Emerging Applications

“…59,60 This is partly because of the stable and uniform dispersion of metal cations in the starting solution. Expanding this method, the generation of thermodynamic instability during the epoxide-mediated solgel polymerization enables well-defined macropores to be formed even in mixed oxide systems.…”