Luminescence and IR characterization of acid sites on alumina
- Univ. of Connecticut, Storrs, CT (United States)
- Engelhard Corporation, Menlo Park, NJ (United States)
Luminescence and infrared (IR) spectroscopies of pyridine and ammonia adsorption have been used to measure acidities of [gamma]-alumina. Neither luminescence nor IR spectra of pyridine adsorption show an Bronsted acidity on [gamma]-alumina pretreated to 400[degrees]C. However, luminescence emission data reveal four weak OH bands even when pretreatment is done at 600[degrees]C. Pyridine and subsequent water adsorption yield six luminescence emission bands. A red shift of the pyridine emission band is found when pretreatment or desorption temperature is increased. IR spectra of ammonia on alumina pretreated at 400[degrees]C show three deformation bands at 1452, 1465, and 1485 cm[sup [minus]1]. The first band is also observed together with a band at 1554 cm[sup [minus]1] even for pretreatment at 950[degrees]C, and it corresponds to NH[sup +][sub 4] formed from dissociative adsorption of ammonia, while the other two bands are assigned to ammonia adsorbed on Bronsted acid sites. These two bands disappear along with the appearance of a new band at 1429 cm[sup [minus]1], when deuterated alumina is pretreated at 400[degrees]C and subsequently subjected to ammonia. This new band at 1429 cm[sup [minus]1] is due to NH[sub 3]D[sup +] formed from ammonia adsorbed on acidic OD sites. Consequently, ammonia IR results demonstrate the existence of Bronsted acid sites on alumina pretreated at 400[degrees]C. 38 refs., 9 figs., 2 tabs.
- OSTI ID:
- 7197571
- Journal Information:
- Journal of Catalysis; (United States), Vol. 146:2; ISSN 0021-9517
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
ALUMINIUM OXIDES
SORPTIVE PROPERTIES
AMMONIA
ADSORPTION
PYRIDINE
ABSORPTION SPECTROSCOPY
BROENSTED ACIDS
DEUTERIUM COMPOUNDS
EMISSION SPECTROSCOPY
ALUMINIUM COMPOUNDS
AZINES
CHALCOGENIDES
HETEROCYCLIC COMPOUNDS
HYDRIDES
HYDROGEN COMPOUNDS
INORGANIC ACIDS
NITROGEN COMPOUNDS
NITROGEN HYDRIDES
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
PYRIDINES
SORPTION
SPECTROSCOPY
SURFACE PROPERTIES
400201* - Chemical & Physicochemical Properties