silicatetitanate

Silicatetitanate is a class of inorganic compounds that contain silicon, titanium, and oxygen, often forming titanosilicate networks in which titanium atoms substitute for silicon within a silica-like framework. The term is commonly used for titanosilicate materials in which Ti4+ occupies tetrahedral sites in a silicate lattice, producing porous, oxide-rich structures with catalytic potential. These materials are distinguished from simple mixtures of silicon and titanium oxides by the integration of Ti into the framework.

Most silicatetitanates are framework solids comprising interlinked SiO4 and TiO4 tetrahedra that share corners to create three-dimensional networks. The titanium substitution introduces Lewis acid sites and can enable redox chemistry when paired with suitable oxidants. The overall composition is often described as Si1−xTixO2, with x typically small (a few percent), though higher Ti loadings are reported in non-framework titanates or partially substituted frameworks.

Examples and synthesis: The archetypal member is titanium silicalite, commonly referred to as TS-1, a titanium-substituted MFI-type framework synthesized by hydrothermal methods with structure-directing agents. Other framework types and non-zeolitic titanosilicates have been synthesized by similar methods using silica sources, titanium precursors, and appropriate directing agents.

Applications and properties: Silicatetitanates are used as heterogeneous catalysts, particularly in selective oxidation reactions with hydrogen peroxide, such as epoxidation of alkenes and oxidation of alkanes. Their solid acidity and hydrothermal stability also make them candidates for adsorption and photocatalysis. A key challenge is achieving uniform Ti incorporation and preventing the formation of inactive or extra-framework titanium species, which can reduce catalytic efficiency.

See also: titanosilicate zeolites, TS-1, silicalite.