Synthesis, characterization, and catalytic activity in the n-heptane conversion over Pt/In–Al2O3 sol–gel prepared catalysts
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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 m2/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–Al2O3 catalysts, in comparison with the Pt-In/Al2O3–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%) of indium.
KeywordsPlatinum–indium sol–gel catalysts Platinum–indium catalysts Indium doped-alumina supports 27Al NMR-MAS indium-doped alumina Indium doped-alumina supports acidity
We acknowledge CONACYT for the financial support for Project No. 32274. V.R. thanks CONACYT for a fellowship.
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