Acid strength of silica-supported oxide catalysts studied by microcalorimetric measurements of pyridine adsorption

Journal Article · Thu Jan 31 23:00:00 EST 1991 · Journal of Catalysis; (USA)

DOI:https://doi.org/10.1016/0021-9517(91)90193-8· OSTI ID:5485940

Cardona-Martinez, N; Dumesic, J A ^[1]

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1. Univ. of Wisconsin, Madison (USA)

Microcalorimetric measurements of the differential heat of pyridine adsorption were used to probe the distribution of acid strength on a series of silica-supported oxide catalysts. Depositing oxides of the following cations onto silica increased the acid strength of the catalyst: Ga{sup 3{plus}}, Zn{sup 2{plus}}, Al{sup 3{plus}}, Fe{sup 3{plus}}, Fe{sup 2{plus}}, Mg{sup 2{plus}}, and Sc{sup 3{plus}}. The acid strength distribution curves for the supported oxide samples showed either two or three regions of constant heat of adsorption while silica had an energetically homogeneous surface. The Ga, Al, and Sc samples were found to have both Bronsted and Lewis acidity while the remaining samples showed only Lewis acidity. Incremental adsorption of pyridine indicated that the initial region of highest heat corresponds to strong Lewis acidity while intermediate heats seemed to be due to weaker Lewis acid sites or a combination of Lewis and Bronsted acid sites. The final region of lowest heat was due to H-bonded pyridine on silica. Estimates of the entropies of adsorption were determined, providing information about the mobility of the adsorbed pyridine molecules. The initial differential heat of adsorption increases proportionally to the Sanderson electronegativity of the added oxide.

• DOE Contract Number: FG02-84ER13183
• OSTI ID: 5485940
• Journal Information: Journal of Catalysis; (USA), Journal Name: Journal of Catalysis; (USA) Vol. 127:2; ISSN 0021-9517; ISSN JCTLA
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
020400 -- Petroleum-- Processing
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
ADSORPTION
ADSORPTION HEAT
ALKALINE EARTH METAL COMPOUNDS
ALUMINIUM COMPOUNDS
ALUMINIUM OXIDES
AZINES
BROENSTED ACIDS
CALORIMETRY
CATALYST SUPPORTS
CATALYSTS
CATALYTIC EFFECTS
CHALCOGENIDES
ENTHALPY
ENTROPY
GALLIUM COMPOUNDS
GALLIUM OXIDES
HETEROCYCLIC COMPOUNDS
HYDROGEN COMPOUNDS
INORGANIC ACIDS
IRON COMPOUNDS
IRON OXIDES
LEWIS ACIDS
MAGNESIUM COMPOUNDS
MAGNESIUM OXIDES
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
PH VALUE
PHYSICAL PROPERTIES
PYRIDINE
PYRIDINES
SCANDIUM COMPOUNDS
SCANDIUM OXIDES
SILICON COMPOUNDS
SILICON OXIDES
SORPTION
THERMODYNAMIC PROPERTIES
TRANSITION ELEMENT COMPOUNDS
ZINC COMPOUNDS
ZINC OXIDES