Computerized infrared spectroscopic study of surface reactions on selected lanthanide oxides

Thesis/Dissertation · Fri Jan 01 04:00:00 EST 1982

OSTI ID:6204630

Dellisante, G N

The natures of adsorption sites on La/sub 2/O/sub 3/, Nd/sub 2/O/sub 3/, and selected praseodymium oxides were investigated by examining surface reactions of probe molecules using computerized transmission ir spectroscopy on unsupported samples. Additionally, the rehydration/dehydration behavior and crystallographic phase transitions of these oxides were examined in pretreatment temperature experiments involving rehydration of the sesquioxides to hydroxides by water exposure. Following rehydration of La/sub 2/O/sub 3/ to La(OH)/sub 3/, the effect of increasing vacuum pretreatment temperature (350 to 1000/sup 0/C) is to gradually remove surface hydroxyl and carbonate entities (up to 650/sup 0/C), and increase the degree of A-type crystallinity. Increasing crystallinity causes a concomitant decrease in surface oxide basicity. The removal of hydroxyl and carbonate species, as well as increases in oxide basicity, strongly correlated to increases in certain catalytic activities. The adsorption of NH/sub 3/, CO/sub 2/, mixtures of NH/sub 3/ and CO/sub 2/, formic acid, acetic acid, acetaldehyde, and ethanol on the oxides was determined to weakly coordinate in Ln/sup 3 +/ sites, and the surface reactions are discussed. Heating was found to desorb the adsorbed compounds and/or causes changes of the originally adsorbed form into other compounds. The effects of temperature on both adsorption and desorption are reported.

• Research Organization: Texas A and M Univ., College Station (USA)
• OSTI ID: 6204630
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360204 -- Ceramics
Cermets
& Refractories-- Physical Properties
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
400301 -- Organic Chemistry-- Chemical & Physicochemical Properties-- (-1987)
ACETALDEHYDE
ACETIC ACID
ADSORPTION
ALCOHOLS
ALDEHYDES
AMMONIA
CARBON COMPOUNDS
CARBON DIOXIDE
CARBON OXIDES
CARBOXYLIC ACIDS
CHALCOGENIDES
ETHANOL
FORMIC ACID
HYDRIDES
HYDROGEN COMPOUNDS
HYDROXY COMPOUNDS
INFRARED SPECTRA
MONOCARBOXYLIC ACIDS
NITROGEN COMPOUNDS
NITROGEN HYDRIDES
ORGANIC ACIDS
ORGANIC COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
RARE EARTH COMPOUNDS
SORPTION
SORPTIVE PROPERTIES
SPECTRA
SURFACE PROPERTIES