Molybdenum-Confined Hierarchical Titanium Silicalite-1: The Synthesis, Characterization, and Catalytic Activity in Alkene Oxidation

Abstract

Titanium silicalite-1 (TS-1) is an important catalyst for alkene epoxidation, but the crystalline micropore is too small for some alkenes. Although the diffusion limitation would be relieved by intracrystalline mesopores, the catalytic performance should further be improved, considering the alkene conversion. Herein, molybdenum encapsulation was achieved during a silanization process for hierarchical TS-1 synthesis. Although the relative crystallinity decreased, more supermicropores of about 1.2–1.8 nm and mesopores in the 2–4 nm range have been created, leading to increased specific area, mesopore volume (VME), and total pore volume (VT). Comparatively, the VME and VT increased with the Mo content, and most of the Mo and Ti have been confined inside the crystals. Owing to the excellent activity of Mo and the improved accessibility, the catalytic performance was notably enhanced, especially when organic hydroperoxide was the oxidant. More importantly, the stability of the encapsulated molybdenum species in the catalysts is excellent.