Epoxidation of Allyl Alcohol to Glycidol on Ti-MWW Molecular Sieves

Ti-MWW was prepared by acid treatment and calcination on a lamellar precursor, which was synthesized under dynamic hydrothermal crystallization conditions using piperidine as a template and boric acid as a structure-supporting agent. The crystallization time is shortened by the addition of Ti-MWW seeds and raising the stirring rate.Ultraviolet-visible spectra show that the precursor contains tetrahedral and octahedral Ti species. Calcination of the precursor results in a partial condensation of the octahedral Ti to form the anatase phase. The octahedral Ti species belong to a kind of extra-framework Ti, which can be removed easily by the acid treatment in a short time. The calcined Ti-MWW contains anatase when the acid treatment time is too long. The characteristic infrared band at 960 cm−1 is not observed for the Ti-MWW precursor, but it appears in the samples treated with acid. Epoxidation of allyl alcohol with H2O2 on Ti-MWW was studied. Ti-MWW with Si/Ti ratio of 20 and acid treatment for 12–16 h is more effective. The conversion of allyl alcohol is 88.7%, and the selectivity for glycidol is 99% under the reaction conditions of 333 K and 30 min, but the catalytic activity of Ti-MWW decreases when the acid treatment time is too long.