The nature of catalytic sites on lanthanum and neodymium oxides for dehydration/dehydrogenation of ethanol

Journal Article · Thu Mar 01 04:00:00 EST 1990 · Journal of Catalysis; (USA)

DOI:https://doi.org/10.1016/0021-9517(90)90263-J· OSTI ID:6348370

Rosynek, M P; Koprowski, R J; DelliSante, G N ^[1]

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1. 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), Journal Name: Journal of Catalysis; (USA) Vol. 122:1; ISSN 0021-9517; ISSN JCTLA
• Country of Publication: United States
• Language: English

Related Subjects

10 SYNTHETIC FUELS
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37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201 -- Chemical & Physicochemical Properties
ALCOHOLS
CATALYTIC EFFECTS
CHALCOGENIDES
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
DEHYDRATION
DEHYDROGENATION
ETHANOL
HYDROXY COMPOUNDS
INFRARED SPECTRA
KINETICS
LANTHANUM COMPOUNDS
LANTHANUM OXIDES
MEDIUM TEMPERATURE
NEODYMIUM COMPOUNDS
NEODYMIUM OXIDES
ORGANIC COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
PH VALUE
PHASE TRANSFORMATIONS
RARE EARTH COMPOUNDS
REACTION INTERMEDIATES
REACTION KINETICS
SAMPLE PREPARATION
SPECTRA
SURFACE PROPERTIES