Synthesis of anatase-free nano-sized hierarchical TS-1 zeolites and their excellent catalytic performance in alkene epoxidation

Nano-sized hierarchical titanosilicate TS-1 without extra-framework anatase TiO2 has been successfully synthesized by using Triton X-100 as a mesoporous template under rotational crystallization conditions. The resultant material contains a large external surface area and uniform mesopores (2-4 nm). Notably, the titanium ions are fully incorporated into the framework of TS-1 and no extra anatase TiO2 exists. Triton X-100 and rotational crystallization conditions play an important role in eliminating anatase TiO2. The addition of Triton X-100 slows down the crystallization rate of TS-1, while the rota-crystallization accelerates the incorporation rate of Ti, so that the insertion rate of titanium into the framework matches well with that of silicon. As such, the generation of extra-framework anatase TiO2 can be inhibited. Furthermore, in comparison with nano-sized hierarchical TS-1 prepared under static conditions, nano-sized hierarchical TS-1 prepared under rotational conditions exhibits excellent catalytic activity and high stability in alkene epoxidation, especially in bulky alkene epoxidation. The facile synthetic strategy for nano-sized hierarchical TS-1 without extra-framework anatase TiO2 may open new perspectives for its potential application in selective oxidation reactions involving large molecules.