Propene epoxidation over Au/Ti-SBA-15 catalysts

Abstract

Highly dispersed gold nanoparticles were synthesized within the channels of a mesoporous Ti-SBA-15 support, followed by thorough catalyst characterization and testing in the selective epoxidation of propene to propene oxide. For this purpose, two series of Ti-SBA-15 materials differing in their Ti content were prepared by either grafting or direct synthesis. The resulting Au/Ti-SBA-15 catalyst materials were characterized by X-ray fluorescence (XRF), X-ray diffraction (XRD), transmission electron microscopy (TEM), nitrogen sorption, UV–visible diffuse reflectance spectroscopy (UV–vis DRS), and X-ray absorption spectroscopy (EXAFS and XANES) at both the Ti K and Au L3 edges. The catalytic performance of the Au/Ti-SBA-15 materials was been evaluated in the direct epoxidation of propene using a mixture of H2 and O2. The reaction data indicate that Au/Ti-SBA-15 materials obtained by Ti grafting have greater catalytic activity than the samples in which Ti-SBA-15 was obtained by direct synthesis. These differences in catalytic behavior are attributed to differences in the amount and dispersion of Ti within the mesoporous silica support, as well as to differences in the Au nanoparticle size, and are discussed in relation to data obtained previously for Au/TiO2 catalysts.