Synthesis and Characterization of Metal-Supported Mesoporous Silicas Applied to the Adsorption of Benzothiophene

Abstract

The present work reports adsorption/desorption studies of benzothiophene (BT) onto SBA-15 loaded with Fe, Pd and Cu employing in situ FT-IR spectroscopy and batch liquid-phase adsorption methods. The adsorbents were prepared by post-synthesis impregnation of metal salts onto pure siliceous SBA-15 by solid mixture and incipient wetness methods. The adsorbents were characterized by nitrogen adsorption isotherms, TEM, X-ray diffraction and X-ray photoelectron spectroscopy (XPS). The incorporated metals, in different oxidation states, were dispersed as nanoparticles on the mesoporous channels of SBA-15. The surface area decreased significantly for samples with incorporated metals, especially for those prepared by solid-mixture impregnation (Cu and Pd), although the hexagonal arrangement and the average pore size remained virtually unaltered. As revealed by batch adsorption isotherms, the incorporation of metals effectively increased the retention of the adsorbent towards the sulphur compound in the following order: Pd Cu. DRIFT spectra (under in situ adsorption/desorption conditions) of the samples containing Fe and Pd showed that adsorption of BT onto the former is mainly reversible, whereas BT seems to be chemisorbed in the latter and did not desorb readily upon thermal treatment under He flow.