The nature of catalytic sites on lanthanum and neodymium oxides for dehydration/dehydrogenation of ethanol
- Texas A and M Univ., College Station (USA)
The multi-pathway (dehydration/dehydrogenation) conversion of ethanol has been used to investigate the nature and behavior of catalytically active sites on lanthanum and neodymium sesquioxides. Catalytic reaction data, coupled with infrared spectroscopic characterizations of adsorbed species, indicate that at least two different types of catalytically active sites are generated on activated La{sub 2}O{sub 3} and Nd{sub 2}O{sub 3} surfaces that are prepared by thermal dehydration of the corresponding trihydroxides. One kind of site (designated Type I) is much less numerous than the other (Type II), but is more strongly basic and has a much higher initial activity for alcohol dehydration, via a probable ethoxide intermediate, at 300-400{degree}C. The parallel alcohol dehydrogenation pathway, on the other hand, occurs only on Type II sites, which also have moderate dehydration activity. The resulting aldehyde products readsorbs exclusively on the more strongly basic Type I sites, where it undergoes a series of secondary condensation reactions that cause a decrease in the overall rate of alcohol dehydration. The comparative behavioral features of the two kinds of sites may be due to differing surface environments, with Type I sites being in structurally more defective and/or more energetic surface locations than are Type II sites. Increases in pretreatment temperature of the oxides cause thermally induced transformations of Type I sites into Type II sites by a surface annealing or restructuring process, with corresponding modifications in the observed catalytic behavior for the two alcohol conversion pathways. 33 refs.
- DOE Contract Number:
- AS05-78ER06042
- OSTI ID:
- 6348370
- Journal Information:
- Journal of Catalysis; (USA), Vol. 122:1; ISSN 0021-9517
- Country of Publication:
- United States
- Language:
- English
Similar Records
Catalytic behaviors of multi-valent lanthanide oxides. Progress report, September 1, 1981-October 31, 1982
Correlations of physical and chemical properties of lanthanide oxides with catalytic behaviors. Progress report, September 1, 1980-August 31, 1981
Related Subjects
37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
ETHANOL
DEHYDRATION
DEHYDROGENATION
LANTHANUM OXIDES
CATALYTIC EFFECTS
NEODYMIUM OXIDES
CHEMICAL REACTION KINETICS
INFRARED SPECTRA
MEDIUM TEMPERATURE
PH VALUE
PHASE TRANSFORMATIONS
REACTION INTERMEDIATES
SAMPLE PREPARATION
SURFACE PROPERTIES
ALCOHOLS
CHALCOGENIDES
CHEMICAL REACTIONS
HYDROXY COMPOUNDS
KINETICS
LANTHANUM COMPOUNDS
NEODYMIUM COMPOUNDS
ORGANIC COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
RARE EARTH COMPOUNDS
REACTION KINETICS
SPECTRA
102000* - Synthetic Fuels- Products & By-Products- (1990-)
100200 - Synthetic Fuels- Production- (1990-)
400201 - Chemical & Physicochemical Properties