Encapsulation of Keggin-type phosphotungstic acid into the mesopores of SBA-16 as a reusable heterogeneous catalyst for the epoxidation of olefins

Abstract

A heterogeneous catalyst for the epoxidation of olefins was prepared by encapsulating Keggin-type phosphotungstic acid (H3PW12O40) into the mesopores of SBA-16. After the encapsulation, the pore entrance size of SBA-16 was reduced through a silylation method to encompass the catalyst in the mesopores and allow the easy diffusion of the reactants and products during the catalytic process. The prepared catalyst was characterized by FT-IR and inductively coupled plasma-optical emission (ICP-OES) spectroscopies, X-ray diffraction (XRD) and transmission electron microscopy (TEM). The analysis results revealed that the mesoporous nature of SBA-16 has been conserved after encapsulation of the catalyst and followed silylation step. The catalytic activity of the prepared material was assessed in the epoxidation of olefins with H2O2. The heterogeneous catalyst was recovered and reused up to five cycles without considerable decrease in activity