Direct synthesis of TS-1 zeolites with TiO6 active sites for enhanced olefin epoxidation

Abstract

The green and efficient epoxidation of long-chain linear α-olefins represents a crucial step in the synthesis of key industrial intermediates. Although the hydrogen peroxide/titanosilicate-1 (H₂O₂/TS-1) catalytic system is environmentally friendly, its broad industrial implementation has long been hindered by unsatisfactory epoxide selectivity and low H₂O₂ utilization efficiency, which limit large-scale and economical production. To overcome these limitations, a strategy employing tetrapropylammonium bromide (TPABr) as a crystallization modifier was developed to precisely engineer the active sites of TS-1 zeolites. By balancing the incorporation kinetics of titanium and silicon into the framework, uniform distribution of titanium species was achieved, accompanied by the enrichment of highly active Ti(OH)₂(OH₂)₂(OSi)₂ sites. The resulting TS-1-TPABr-40 catalyst delivered outstanding performance in the epoxidation of 1-hexene, exhibiting 97% epoxide selectivity, ∼76% effective H₂O₂ utilization, and good recyclability. These results highlighted how molecular-level coordination engineering in zeolite catalysts could simultaneously enhance catalytic efficiency and oxidant economy, providing a sustainable and scalable strategy for green chemical synthesis.