METAL-Supported SBA-15: Preparation, CHARACTERIZATION and Application IN the Adsorption of Benzothiophene

Aromatic sulfur compounds, such as benzothiophene (BT) and its derivatives, are noticeably refractory to hydrodesulfurization (HDS) processes. In order to meet the increasingly strict environmental requirements, selective physisorption may be a feasible option to lowering the sulfur content of the outlet streams of current HDS units. Yang and co-workers have reported an extensive work on the preparation of adsorbents containing transition metals, especially zeolites, among which copper(I) and palladium(II) have demonstrated to be the most selective towards sulfur compounds as compared to other aromatic species present in fossil fuels [1]. Since BT and its derivatives are bulky molecules, mesoporous matrices, such as MCM-41 and SBA-15, have been recently proposed for their adsorption. The present work reports adsorption/desorption studies of benzothiophene (BT) on SBA-15 loaded with PdCl2 and CuCl by in situ FTIR. The adsorbent was prepared following a similar procedure as that reported by Yangxs group [2], using pure siliceous SBA-15 as the starting material. The adsorbents were characterized by N2 adsorption isotherms, TEM, X-ray diffraction and X-ray photoelectron spectroscopy (XPS). The incorporated metals were well dispersed as nanoparticles on the mesoporous channels of SBA, under different oxidation states. Surface area decreased significantly for samples with incorporated metals, although hexagonal arrangement and average pore size remained approximately unaltered. The prepared samples and the starting SBA-15 were then subjected to adsorption at 20oC of BT vapors (carried by He at 150 mL/min), followed by desorption under the same helium flux at distinct temperatures. DRIFT spectra of the adsorbents (under adsorption/desorption) were recorded in situ. The incorporation of metals effectively increased the retention of the adsorbent towards the sulfur compound and the FTIR results were analysed in the light of the textural parameters and surface properties (XPS).

[1] Y. Wang, F. H. Yang, R. T. Yang, J. M. Heinzel and A. D. Nickens, Ind. Eng. Chem. Res. 45(2006) 7649.

[2] Y. Wang, R. T. Yang and J. M. Heinzel, Chem. Eng. Sci. 63 (2008) 356.