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 stucture-supporting agent. The crystallization time is shortened by adding Ti-MWW seeds and increasing 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 extraframework Ti, which can be removed easily by the acid treatment in a short time. The calcined Ti-MWW contains the anatase when the acid-treated 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 by 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 similar to 16 h is more effective. The conversation 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-treated time is too long.