Investigation of the activity and selectivity of the MoO3/AI2O3 catalyst and the structural investigation using in-situ raman
Master Thesis
2002
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University of Cape Town
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Abstract
Metathesis is a very versatile reaction, which allows the conversion of Simple, relatively inexpensive olefins into specialty, high-purity olefins which are useful intermediates in the fragrance, agricultural and many other specialty chemical industries. Supported molybdenum on alumina is an active heterogeneous catalyst for the metathesis of olefins. Its activity, as a function of time, passes a maximum. It is known that the activity of molybdenum-based catalyst increases up to monolayer capacity. Catalysts with various Mo-Ioadings were prepared by controlled adsorption method using ammonium heptamolybdate as a precursor. A catalyst using a new slurry impregnation method was also prepared for comparative reasons. Before the metathesis process, the molybdenum catalysts are activated at 550°C under N2 in a fixed bed reactor. The loading of the prepared catalysts was below and above monolayer capacity. It was observed that up to a loading 0.3 g Mo03 per g Ab03 the initial conversion increases more than proportional to the Mo03- loading. The catalysts with a Mo03-loading higher than 0.3 g Mo03 per gram AIz03 show initially a lower activity, ie. The activity per molybdenum atom in the catalyst decreases. With increasing time-on-stream the activity of the catalysts declines. The decline is much stronger over the catalysts with a rligher initial activity.
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Bibliography: leaves 89-94.
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Jacobs, K. 2002. Investigation of the activity and selectivity of the MoO3/AI2O3 catalyst and the structural investigation using in-situ raman. University of Cape Town.