Phase Formation in Alkaline Titanosilicate Systems during Hydrothermal Synthesis

Abstract

The highly alkaline multicomponent systems TiO₂–H₂SO₄–Na₂SiO₃–NaOH–H₂O and TiO₂–H₂SO₄–(NH₄)₂SO₄–Na₂SiO₃–NaOH–H₂O have been studied under conditions of hydrothermal synthesis, which gives new products with specified technical properties. It has been shown that, by a targeted selection of structure-forming components, in particular, titanium compounds, together with optimal parameters of hydrothermal treatment of the formed precursor, one can obtain compounds with given chemical composition and particle size and morphology. It has been found that the rate of structural transformations in the synthesis depends on the phase composition of titanosilicate precursors. Their hydrothermal treatment involves the alkaline and thermal hydrolysis followed by dehydration of the hydrolyzed phases of titanium(IV) and silicon. This is accompanied by the localization of free bonds ensuring the formation of Ti–O–Si–O bridges and their subsequent transformation into new structured species.