High surface area platinum-titania aerogels: Preparation, structural properties, and hydrogenation activity

Journal Article · Wed Jun 01 00:00:00 EDT 1994 · Journal of Catalysis; (United States)

DOI:https://doi.org/10.1006/jcat.1994.1167· OSTI ID:7275841

Schneider, M; Duff, D G; Mallat, T; Wildberger, M; Baiker, A ^[1]

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1. Swiss Federal Institute of Technology, Zuerich (Switzerland)

High surface area platinum-titania aerogels with marked meso-to macroporosity have been synthesized via the sol-gel-aerogel route. An acid-catalyzed titania gel was prepared from tetrabutoxy-titanium(IV) with methanol as solvent. The platinum precursor solutions added after the redispersion of the titania gel were either PtCl[sub 4], (NH[sub 4])[sub 2]PtCl[sub 6] or Pt(acac)[sub 2] dissolved in protic solvents. Platinum metal particles formed upon high-temperature supercritical drying. The platinum-titania aerogels have a BET surface area of 150 to 190 m[sup 2] g[sup [minus]1] after thermal pretreatments up to 673 K and the titania matrix consists of well-developed anatase crystallites of about 8-9 nm mean size. Depending on the platinum precursor used, the volume-weighted-mean particle size, determined by TEM, varies in the range 3.6 to 68 nm, consistent with XRD results for the platinum component. All aerogel samples showed a pronounced stability of both the titania matrix and the platinum particles towards air or hydrogen at temperatures up to 673 K. Thermal analysis, combined with mass spectroscopy, revealed that the untreated catalysts contain a considerable amount of entrapped organic impurities after the high-temperature supercritical drying. For the characterization of the activity and the accessibility of platinum particles the liquid phase hydrogenations of trans-stilbene and benzophenone were used as test reactions. Compared to a commercial alumina-supported platinum catalyst, the untreated 2-5 wt% platinum-titania catalysts derived from (NH[sub 4])[sub 2]PtCl[sub 6]- and especially PtCl[sub 4]-precursor solutions exhibit a markedly higher catalytic activity. In general, air pretreatments at 573 K or above had either no or promoting influence on activity. In contrast, pretreatments in hydrogen produced either no or detrimental activity change. 50 refs., 9 figs., 3 tabs.

• OSTI ID: 7275841
• Journal Information: Journal of Catalysis; (United States), Vol. 147:2; ISSN 0021-9517
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
02 PETROLEUM
BENZOPHENONE
HYDROGENATION
PLATINUM
CATALYTIC EFFECTS
STILBENE
TITANIUM OXIDES
CATALYST SUPPORTS
CATALYSTS
MASS SPECTROSCOPY
SOL-GEL PROCESS
STRUCTURAL CHEMICAL ANALYSIS
THERMAL ANALYSIS
TRANSMISSION ELECTRON MICROSCOPY
X-RAY DIFFRACTION
AROMATICS
CHALCOGENIDES
CHEMICAL REACTIONS
COHERENT SCATTERING
DIFFRACTION
ELECTRON MICROSCOPY
ELEMENTS
HYDROCARBONS
KETONES
METALS
MICROSCOPY
ORGANIC COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
PLATINUM METALS
SCATTERING
SPECTROSCOPY
TITANIUM COMPOUNDS
TRANSITION ELEMENT COMPOUNDS
TRANSITION ELEMENTS
400201* - Chemical & Physicochemical Properties
020400 - Petroleum- Processing