Nature, Environment and Quantification of Titanium Species in TiSiBEA Zeolites Investigated by XRD, NMR, DR UV–Vis and XPS

Highly Hydrophilic Ti−Beta Zeolite with Ti−Rich Exterior as Efficient Catalyst for Cyclohexene Epoxidation

Nanocrystalline Ti−Beta zeolite with high hydrophilicity and a Ti−rich exterior was successfully prepared via a dissolution–recrystallization method. With the post−treatment of tetraethylammonium hydroxide (TEAOH) solution at elevated temperature, the Si and Ti species within the Ti−Beta matrix were partially dissolved and recrystallized on the outer surface of crystals, resulting in the Ti−rich exterior and higher hydrophilicity, which improved the accessibility of the active Ti sites and the enrichment of H2O2. Simultaneously, some of the closed Ti(OSi)4 species were transformed to more active open Ti(OSi)3OH or Ti(OSi)2(H2O)2(OH)2 species. The modified Ti−Beta zeolite exhibited greatly enhanced catalytic performance in the epoxidation of cyclohexene in comparison to the parent Ti−Beta.

Highly selective 1-pentene epoxidation over Ti-MWW with modified microenvironment of Ti active sites

The hexa-coordinated Ti active sites with the piperidine molecules as ligand significantly accelerate H₂O₂ activation, which effectively improve the catalytic performance of Ti-MWW in the 1-pentene epoxidation reaction.