Effect of γ-Al2O3 hydrothermal treatment on the formation and properties of platinum sites in Pt/γ-Al2O3 catalysts

• Increase the fraction of bridging OH groups and concentration of Lewis acid sites.
• Preferential formation of outer-sphere complexes.
• Changes in the dispersion and electronic state of supported Pt.
• Effect of hydrothermal treatment of the support on catalytic properties of Pt/Al2O3.

The effect of hydrothermal treatment (HTT) of γ-alumina on the state of its surface functional cover, anchoring of hexachloroplatinate, and properties of platinum sites was investigated. Hydrothermal treatment of γ-Al2O3 was found to increase the fraction of surface bridging OH groups and concentration of Lewis acid sites (LAS) and alter the metal complex–support interaction. Adsorption of hexachloroplatinate on the support surface is accompanied mainly by the formation of outer-sphere complexes, which are characterized by a lower reduction temperature. As a result, dispersion and electronic state of supported platinum are changed. Influence of γ-Al2O3 hydrothermal treatment on the catalytic properties of Pt/Al2O3 in n-hexane transformations and propane dehydrogenation was demonstrated. The revealed effect of γ-Al2O3 hydrothermal treatment on the formation of platinum sites in Pt/Al2O3 catalysts can be of fundamental importance for the steps of supported system synthesis where solid phase is contacting with water and aqueous solutions (impregnation and drying).

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