Abstract
The catalytic activities and properties of noble metals (Pt, Pd, Rh, Ru) supported on silica gel (SiO 2 ) and alumina-modified silica gel (Al 2 O 3 -SiO 2 ) were investigated for the hydrodesulfurization of thiophene. Al 2 O 3 -SiO 2 was prepared by an impregnation method using aluminum nitrate (Al(NO 3 ) 3 · 9H 2 O) aqueous solution. Pt/ 8 wt%Al 2 O 3 -SiO 2 catalyst showed the highest activity for hydrodesulfurization of thiophene among various supported noble metal catalysts and this activity was higher than that of commercial CoMo/Al 2 O 3 hydrodesulfurization catalyst. The sulfur tolerance of noble metal/SiO 2 was enhanced by Al 2 O 3 modification of SiO 2 and Pt/8 wt%Al 2 O 3 -SiO 2 catalyst showed the highest sulfur tolerance among the supported noble metal catalysts. Pt/ 8 wt%Al 2 O 3 -SiO 2 catalyst had high hydrogenating ability for unsaturated C 4 hydrocarbons formed in the hydrodesulfurization of thiophene. The catalysts were characterized by 2-propanol dehydration, cumene cracking, XRD, H 2 adsorption and FT-IR. Dispersion of Pt on 8 wt%Al 2 O 3 -SiO 2 was remarkably higher than that on SiO 2 and the particle size of Pt on 8 wt%Al 2 O 3 -SiO 2 was the lowest among the supported noble metal catalysts. The acidity of 8 wt%Al 2 O 3 -SiO 2 was higher than that of SiO 2 . Furthermore, Bronsted acid sites were present on 8 wt%Al 2 O 3 -SiO 2 . FT-IR spectroscopy of thiophene adsorbed on 8 wt%Al 2 O 3 -SiO 2 support indicated that the thiophene molecule interacts with the Bronsted acid site on 8 wt%Al 2 O 3 -SiO 2 . The activity of the double-layer (Pt/SiO 2 + 8 wt%Al 2 O 3 -SiO 2 ) catalyst obtained experimentally was higher than that calculated. This suggests that spillover hydrogen was present on Pt/Al 2 O 3 -SiO 2 in the hydrodesulfurization of thiophene. Both the Bronsted acid sites of Al 2 O 3 -SiO 2 and the Pt particles in the Pt/Al 2 O 3 -SiO 2 catalyst act as active sites for the hydrodesulfurization of thiophene.
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