Catalytic behaviors of lanthanum and neodymium oxides for dehydrogenation/dehydration of ethanol

Thesis/Dissertation · Tue Jan 01 04:00:00 EST 1985

OSTI ID:5044153

Koprowski, R J

Ethanol dehydrogenation and dehydration reactions have been employed to investigate the nature and behavior of catalytically active sites on lanthanum and neodymium sesquioxides. In support of this objective, x-ray powder diffraction, surface area determinations, and thermogravimetric analyses have been performed to augment previously reported characterization results. Activated lanthanum and neodymium oxide catalysts have been prepared by thermal dehydration of the corresponding trihydroxides. The catalytic reaction data on these materials, when correlated with complemented with infrared spectroscopic measurements of adsorbed species reported in the literature, indicate that arrays of at least two dissimilar types of catalytically active sites are generated. 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. The latter reaction probably occurs via an ethoxide intermediate at 300-400/sup 0/C. The parallel alcohol dehydrogenation pathway, on the other hand, occurs only on Type II sites which have only moderate dehydration activity. The resulting aldehyde product re-absorbs exclusively on the more strongly basic Type I sites, where it undergoes a series of secondary condensation/decarboxylation reactions and consequently leads to a decrease in the overall rate of alcohol dehydration. The contrasting 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 prior pretreatment temperature of the oxides cause thermally-induced transformations of Type I sites into Type II sites by a surface annealing or re-structuring process with corresponding modifications in the observed catalytic behaviors for the two alcohol decomposition pathways.

• Research Organization: Texas A and M Univ., College Station (USA)
• OSTI ID: 5044153
• Country of Publication: United States
• Language: English

Related Subjects

090210* -- Alcohol Fuels-- Properties-- (1976-1989)
10 SYNTHETIC FUELS
ALCOHOLS
CATALYSIS
CATALYTIC EFFECTS
CHALCOGENIDES
CHEMICAL REACTIONS
DEHYDRATION
DEHYDROGENATION
ETHANOL
HYDROXY COMPOUNDS
LANTHANUM COMPOUNDS
LANTHANUM OXIDES
NEODYMIUM COMPOUNDS
NEODYMIUM OXIDES
ORGANIC COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
RARE EARTH COMPOUNDS