Enhanced catalytic oxidation performance of K+-modified Ti-MWW through selective breaking of interfacial hydrogen-bonding interactions of H2O2

摘要

Cationic modification was applied to Ti-MWW zeolite via the treatment of potassium chloride (KCl). Compared to the original Ti-MWW zeolite, the K-modified Ti-MWW sample (Ti-MWW-K) exhibited much improved catalytic activity, selectivity and stability in the liquid-phase epoxidation of alkenes. Our investigation shows that the K+ modification has negligible effect on the physicochemical properties, the state of the Ti active sites and the Lewis acidic strength of the Ti-MWW catalyst. Our result has further indicated that breaking of the hydrogenbonding interactions between the O-beta atom of H2O2 (H-alpha-O-alpha-O-beta-H-end) and the H atom of the silanols adjacent to the Ti-OH (Si-OH(HO-Ti)) in the Ti-MWW-K zeolite promotes the activation of H2O2, which is responsible for its superior catalytic oxidation activity. This finding helps shed light on utilizing the hydrogen-bonding interactions based on the titanosilicates/H2O2 system to achieve the excellent catalytic oxidation performance.