Pretreatment chemistry in the preparation of silica-supported Pt, Ru, and PtRu catalysts: An in situ UV diffuse reflectance study
Pretreatment chemistry in the preparation of silica-supported Pt, Ru, and PtRu catalysts: An in situ UV diffuse reflectance study
- Journal of catalysis, 133(1), p.202-219, 1992 .
Silica-supported metal catalysts were prepared from strongly absorbing Pt(NH3)4(NO3)2 and Ru(NH3)6Cl3 precursors at a pH of 9. When supported [Pt(NH3)4]2+ was directly reduced in H2 at 400°C, a Pt dispersion of 40 Silica-supported metal catalysts were prepared from strongly absorbing Pt(NH3)4(NO3)2 and Ru(NH3)6Cl3 precursors at a pH of 9. When supported [Pt(NH3)4]2+ was directly reduced in H2 at 400°C, a Pt dispersion of 40 percent was obtained. Pretreatment in flowing oxygen resulted in a Pt dispersion of 70 percent. The in situ diffuse UV reflectance data suggest that pretreatment inH2 results in the formation of a mobile [Pt(NH3)2(H)2]0 Species. Surface diffusion during reduction results in the agglomeration of Pt particles to form a supported catalyst with a relatively low dispersion. When the decompositon of the Pt precursor is carried out in flowing O2, a Pt2+ precursor with low surface mobility is formed. This results in the formation of a much more highly dispersed Pt catalyst. Studies carried out using Ru(NH3)6Cl3 as the metal precursor resulted in very low dispersions when the pretreatment was carried out in O2. The Ru dispersion was a direct function of the oxidative pretreatment temperature. It was concluded that the mobile surface species consisted of Ru oxides, most likely RuO4. Reduction in H2 resulted in the formation of highly dispersed Ru. In addition to diffuse reflectance spectroscopy, surface characterization techniques included TEM, EDXS, and chemisorption.
Silica-supported metal catalysts were prepared from strongly absorbing Pt(NH3)4(NO3)2 and Ru(NH3)6Cl3 precursors at a pH of 9. When supported [Pt(NH3)4]2+ was directly reduced in H2 at 400°C, a Pt dispersion of 40 Silica-supported metal catalysts were prepared from strongly absorbing Pt(NH3)4(NO3)2 and Ru(NH3)6Cl3 precursors at a pH of 9. When supported [Pt(NH3)4]2+ was directly reduced in H2 at 400°C, a Pt dispersion of 40 percent was obtained. Pretreatment in flowing oxygen resulted in a Pt dispersion of 70 percent. The in situ diffuse UV reflectance data suggest that pretreatment inH2 results in the formation of a mobile [Pt(NH3)2(H)2]0 Species. Surface diffusion during reduction results in the agglomeration of Pt particles to form a supported catalyst with a relatively low dispersion. When the decompositon of the Pt precursor is carried out in flowing O2, a Pt2+ precursor with low surface mobility is formed. This results in the formation of a much more highly dispersed Pt catalyst. Studies carried out using Ru(NH3)6Cl3 as the metal precursor resulted in very low dispersions when the pretreatment was carried out in O2. The Ru dispersion was a direct function of the oxidative pretreatment temperature. It was concluded that the mobile surface species consisted of Ru oxides, most likely RuO4. Reduction in H2 resulted in the formation of highly dispersed Ru. In addition to diffuse reflectance spectroscopy, surface characterization techniques included TEM, EDXS, and chemisorption.