abstract
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Platinum catalysts supported on indium-doped alumina were prepared by the sol-gel method. The method allows the incorporation of In3 in the alumina network. The indium-doped alumina supports showed narrow pore size distribution (5.4-4.0 nm) and high specific surface areas (258-280 m 2/g). The 27Al NMR-MAS spectroscopy identified aluminum in tetrahedral, pentahedral, and octahedral coordination; however, the intensity of the signal assigned to aluminum in pentahedral coordination diminishes with the increase of the content of indium. Total acidity determined by ammonia thermodesorption diminishes strongly in Pt/In-Al2O3 catalysts, suggesting a selective deposit of platinum over the acid sites of the support. The effect of the support in the platinum catalytic activity was evaluated in the n-heptane dehydrocyclization reaction. The selectivity patterns for such reaction were modified substantially in the doped Pt/In-Al 2O3 catalysts, in comparison with the Pt-In/Al 2O3-I coimpregnated reference catalyst. As an important result, the formation of benzene was suppressed totally over the indium-doped alumina sol-gel supports with a high content (3 wt%25) of indium. © Springer Science Business Media, LLC 2007.
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Platinum catalysts supported on indium-doped alumina were prepared by the sol-gel method. The method allows the incorporation of In3%2b in the alumina network. The indium-doped alumina supports showed narrow pore size distribution (5.4-4.0 nm) and high specific surface areas (258-280 m 2/g). The 27Al NMR-MAS spectroscopy identified aluminum in tetrahedral, pentahedral, and octahedral coordination; however, the intensity of the signal assigned to aluminum in pentahedral coordination diminishes with the increase of the content of indium. Total acidity determined by ammonia thermodesorption diminishes strongly in Pt/In-Al2O3 catalysts, suggesting a selective deposit of platinum over the acid sites of the support. The effect of the support in the platinum catalytic activity was evaluated in the n-heptane dehydrocyclization reaction. The selectivity patterns for such reaction were modified substantially in the doped Pt/In-Al 2O3 catalysts, in comparison with the Pt-In/Al 2O3-I coimpregnated reference catalyst. As an important result, the formation of benzene was suppressed totally over the indium-doped alumina sol-gel supports with a high content (3 wt%25) of indium. © Springer Science%2bBusiness Media, LLC 2007.
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