Highly dispersed uniformly sized Pt nanoparticles on mesoporous Al-SBA-15 by solid state impregnation

Highly dispersed Pt nanoparticles on modified mesoporous Al-SBA-15 were obtained by a solid state impregnation (SSI) methodology, which consisted of a physical mixture of Al-SBA-15 support with a given amount of Pt(acac)2 in order to have 1 wt.% of Pt on the final solid. The solid mixture was ground vigorously and annealed at 180 °C (e.g. the sublimation point of Pt(acac)2) for 0.5 h and then at 400 °C in inert atmosphere, to decompose the organic ligand. The materials were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) by applying high angle annular dark field (HAADF) technique, nitrogen physisorption, pyridine adsorption by infrared spectroscopy (FTIR), X-ray photoelectronic spectroscopy (XPS) and FTIR of CO adsorption. Catalytic activity of Pt nanoparticles was evaluated in naphthalene hydrogenation (HYD) as test reaction. The results were compared with those obtained on Pt nanoparticles dispersed on Al-SBA-15 by wet impregnation (WI) method. Both SSI and WI methods produce significant differences in the population of flat and edge sites on the Pt nanoparticles with dimensions around 1.0 nm. However, Pt nanoparticles obtained by SSI showed higher activity upon naphthalene HYD than those obtained by WI method, which was explained by the higher density of edge sites measured by FTIR of CO adsorption.

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► 1 nm Pt nanoparticles are formed by a solid impregnation of Pt(acac)2 on Al-SBA-15
► A near sublimation point, 180̊C, heat-treatment is used to diffuse Pt(acac)2 onto SBA
► 6 times more edge/flat Pt sites are attained in comparison with a wet impregnation
► Pt/Al-SBA-15 is twice active in naphthalene hydrogenation than by wet impregnation