Preparation, structural properties, and hydrogenation activity of highly porous palladium-titania aerogels

Journal Article · Mon Aug 01 00:00:00 EDT 1994 · Journal of Catalysis; (United States)

DOI:https://doi.org/10.1006/jcat.1994.1249· OSTI ID:6618637

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

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

Mesoporous to macroporous palladium-titania aerogels with high surface area have been synthesized by the sol-gel-aerogel route. A titania gel was prepared by the addition of an acidic hydrolysant to tetrabutoxytitanium(IV) in methanol. The palladium precursor solutions, added after the redispersion of the titania gel, were either Na[sub 2]PdCl[sub 4], (NH[sub 4])[sub 2]PdCl[sub 4], Pd(acac)[sub 2], or Pd(OAc)[sub 2] dissolved in protic or aprotic solvents. The palladium-titania aerogels have a BET surface area of 170-190 m[sup 2]g[sup [minus]1] after a thermal treatment up to 673 K and contain well-developed anatase crystallites of about 7-8 nm mean size. Depending on the palladium precursor used, the volume-weighted-mean particle size, determined by TEM, varies significantly in the range 21-224 nm, this being independently consistent with XRD line-broadening results. All aerogel samples showed pronounced structural stability of both the titania matrix and the palladium particles towards the pretreatment media used (air or hydrogen) at temperatures up to 773 K. Thermal analysis, combined with mass spectrometry, revealed that the untreated catalysts contain a considerable amount of entrapped organic impurities after high-temperature supercritical drying. Liquid-phase hydrogenations of tras-stilbene and benzophenone were used as test reactions for characterizing the activity and accessibility of the palladium particles. A comparison of the best dispersed Pd(OAc)[sub 2]-derived aerogel catalysts with conventionally impregnated titania-supported palladium catalysts in the liquid-phase hydrogenation of 4-methylbenzaldehyde reveals superior activity and selectivity for the aerogel catalysts. 32 refs., 10 figs., 4 tabs.

• OSTI ID: 6618637
• Journal Information: Journal of Catalysis; (United States), Vol. 148:2; ISSN 0021-9517
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
BENZOPHENONE
HYDROGENATION
PALLADIUM
CATALYTIC EFFECTS
STILBENE
TITANIUM OXIDES
CATALYST SUPPORTS
CHEMICAL PREPARATION
GELS
MASS SPECTROSCOPY
POROUS MATERIALS
TRANSMISSION ELECTRON MICROSCOPY
X-RAY DIFFRACTION
AROMATICS
CHALCOGENIDES
CHEMICAL REACTIONS
COHERENT SCATTERING
COLLOIDS
DIFFRACTION
DISPERSIONS
ELECTRON MICROSCOPY
ELEMENTS
HYDROCARBONS
KETONES
MATERIALS
METALS
MICROSCOPY
ORGANIC COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
PLATINUM METALS
SCATTERING
SPECTROSCOPY
SYNTHESIS
TITANIUM COMPOUNDS
TRANSITION ELEMENT COMPOUNDS
TRANSITION ELEMENTS
400201* - Chemical & Physicochemical Properties