Metal-support interactions in supported Pt catalysts

Abstract

The metal-support interactions of platinum supported on $γ-Al_2O_3$, $SiO_2$, $SiO_2-Al_2O_3$, and $TiO_2$ were experimentally studied with cyclohexene hydrogenation reaction and hydrogen chemisorption. The chemisorption properties of Pt/$TiO_2$ were observed at temperatures from 100 to 800℃. The reaction was performed in a quasi-differential flow reactor, and the chemisorption was carried out in a static sorption apparatus. The catalysts were prepared by incipient wetness method with chloroplatinic acid solution ($H_2PtCl_6ㆍ6H_2O$). The $Pt/γ-Al_2O_3$ and $Pt/TiO_2$ showed similar behaviors; the activity and dispersion of the two catalysts decreased upon reduction at 800℃, and they increased with oxidation at 500℃ followed by reduction at 400℃. However, the activity and dispersion properties of $Pt/γ-Al_2O_3$ were due to redispersion phenomena, and those of $Pt/TiO_2$ were due to SMSI phenomena. The catalytic activity of $Pt/SiO_2$ also increased by oxidation, but not the dispersion. The $PT/SiO_2-Al_2O_3$ showed only sintering behavior. Different behaviors between $Pt/γ-Al_2O_3$ and $Pt/TiO_2$ were demonstrated with serial oxidation treatment.