A study of the unreduced molybdena-alumina system

Journal Article · Thu Jul 01 04:00:00 EDT 1993 · Journal of Catalysis; (United States)

DOI:https://doi.org/10.1006/jcat.1993.1193· OSTI ID:5621323

Pantoja, A; Sarrin, J; Gonzalez, L; Noguera, O; Perez Zurita, M J; Galavis, J L; Goldwasser, J ^[1]

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1. Escuela de Quimica, Caracas (Venezuela)

The isomerization and metathesis of 1-butene was carried out over a series of molybdena-alumina catalysts (1.0-8.2 wt% Mo) prepared by the adsorption equilibrium method. Catalytic conversion measurements (including the effect of preadsorbed water), tracer experiments (1-butene-d[sub o]+1-butene-d[sub 8]), pyridine adsorption followed by IR spectroscopy, and ESR studies were used as tools for the characterization of the solids. The pyridine adsorption experiments showed an increase in the number of acid sites as well as in the acid strength with increasing metal loading. The catalytic measurements showed a related increase in the rate of isomerization as the %Mo is increased. The cis/trans ratios decreased with increasing molybdenum loading, suggesting an increase in the acid strength of the remaining alumina hydroxyl groups. The results suggest a Broensted acid mechanism for the isomerization reaction over catalysts with molybdenum loading [ge] 3.9% Mo. The 1.0% molybdena-alumina catalyst behaved totally different. The results suggest a [pi]-allylic mechanism operative on the unperturbed alumina surface. The rate of formation of ethylene and propylene (products of metathesis) increased dramatically with increasing molybdenum loading. The catalysts evacuated at 500[degrees]C were considerably more active for the metathesis transformations than after evacuation at 500[degrees]C and/or after contacting the catalyst with the olefin. No Mo(V) signal was observed for the 1.0% Mo catalyst. The results suggest that the more easily reducible the catalyst is, the easier it would be to effect olefin metathesis. 35 refs., 4 figs., 6 tabs.

• OSTI ID: 5621323
• Journal Information: Journal of Catalysis; (United States), Journal Name: Journal of Catalysis; (United States) Vol. 142:1; ISSN 0021-9517; ISSN JCTLA5
• Country of Publication: United States
• Language: English

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ABSORPTION SPECTROSCOPY
ALKENES
ALUMINIUM COMPOUNDS
ALUMINIUM OXIDES
BROENSTED ACIDS
BUTENES
CATALYSTS
CATALYTIC EFFECTS
CHALCOGENIDES
CHEMICAL REACTIONS
ELECTRON SPIN RESONANCE
EQUILIBRIUM
ETHYLENE
HYDROCARBONS
HYDROGEN COMPOUNDS
INORGANIC ACIDS
ISOMERIZATION
MAGNETIC RESONANCE
MOLYBDENUM COMPOUNDS
MOLYBDENUM OXIDES
ORGANIC COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
PROPYLENE
REFRACTORY METAL COMPOUNDS
RESONANCE
SPECTROSCOPY
TRANSITION ELEMENT COMPOUNDS