Anatase-Free Nanosized Hierarchical Titanosilicate TS-1 Synthesis via Nitric Acid-Catalyzed Gel Preparation.

A new approach to the synthesis of a nanosized and hierarchical titanosilicate, TS-1, is presented. Instead of using specific solid or additional mesoporous templates or individual additives to slow down the hydrolysis of titanium alkoxides, it is proposed that the titanosilicate TS-1 can be obtained from gels synthesized with hydrolysis catalysts (HNO and tetrapropylammonium hydroxide). When nitric acid catalyzes tetraethyl orthosilicate (TEOS) hydrolysis, the resulting crystalline TS-1 that can be obtained has uniform particle sizes (150-180 nm), is anatase-free, and contains up to 46-67% of mesopores. When a base catalyst is applied, the obtained material's features are opposite. Moreover, acid-promoted TS-1 samples catalyze cyclohexene HO-oxidation via a heterolytic route to the cyclohexane epoxide with 67% selectivity, which is non-typical.