Pretreatment chemistry in the preparation of silica-supported Pt, Ru, and Pt-Ru catalysts: An in situ UV diffuse reflectance study
- Tulane Univ., New Orleans, LA (United States)
Silica-supported metal catalysts were prepared from strongly absorbing Pt(NH{sub 3}){sub 4}(NO{sub 3}){sub 2} and Ru(NH{sub 3}){sub 6}Cl{sub 3} precursors at a pH of 9. When supported (Pt(NH{sub 3}){sub 4}){sup 2+} was directly reduced in H{sub 2} at 400 C, a Pt dispersion of 40% was obtained. Pretreatment in flowing oxygen resulted in a Pt dispersion of 70%. The in situ diffuse UV reflectance data suggest that pretreatment in H{sub 2} results in the formation of a mobile (Pt(NH{sub 3}){sub 2}(H){sub 2}){sup 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 decomposition of the Pt precursor is carried out in flowing O{sub 2}, a Pt{sup 2+} 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(NH{sub 3}){sub 6}Cl{sub 3} as the metal precursor resulted in very low dispersions when the pretreatment was carried out in O{sub 2}. 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 RuO{sub 4}. Reduction in H{sub 2} resulted in the formation of highly dispersed Ru. In addition to diffuse reflectance spectroscopy, surface characterization techniques included TEM, EDXS, and chemisorption.
- DOE Contract Number:
- FG02-86ER13511
- OSTI ID:
- 6977642
- Journal Information:
- Journal of Catalysis; (United States), Vol. 133:1; ISSN 0021-9517
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
CATALYSTS
CHEMICAL PREPARATION
ABSORPTION SPECTROSCOPY
AGGLOMERATION
BIMETALS
CATALYST SUPPORTS
CHEMISORPTION
DIFFUSION
DISTRIBUTION
HYDROGEN
PLATINUM
PLATINUM ALLOYS
PRECURSOR
REDUCTION
REFLECTIVITY
RUTHENIUM
RUTHENIUM ALLOYS
RUTHENIUM OXIDES
SILICON OXIDES
SPECTROSCOPY
SURFACE PROPERTIES
TEMPERATURE DEPENDENCE
TRANSMISSION ELECTRON MICROSCOPY
ULTRAVIOLET RADIATION
X-RAY SPECTROSCOPY
ALLOYS
CHALCOGENIDES
CHEMICAL REACTIONS
ELECTROMAGNETIC RADIATION
ELECTRON MICROSCOPY
ELEMENTS
METALS
MICROSCOPY
NONMETALS
OPTICAL PROPERTIES
OXIDES
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
PLATINUM METAL ALLOYS
PLATINUM METALS
RADIATIONS
REFRACTORY METAL COMPOUNDS
RUTHENIUM COMPOUNDS
SEPARATION PROCESSES
SILICON COMPOUNDS
SORPTION
SYNTHESIS
TRANSITION ELEMENT COMPOUNDS
TRANSITION ELEMENTS
400201* - Chemical & Physicochemical Properties