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Title: 1-butene isomerisation over silica-alumina catalyst
Author: Stefanowicz-Pieta, Izabela
ISNI:       0000 0001 3479 4898
Awarding Body: University of Aberdeen
Current Institution: University of Aberdeen
Date of Award: 2006
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Reactions involving double-bond and skeletal isomerization of alkenes have been widely investigated, however, the relations between the activity and selectivity and strength or density of the acid sites are still not fully understood. Most authors believe that the reaction is catalysed by Bmnsted acid sites while others support the idea that Lewis sites can act in this reaction and discussion still exists as to the exact role of carbonaceous materials and of dimeric/ oligomeric intermediates. The double-bond isomerization of n-butene has been studied previously and it seems that an apparent correlation exists between selectivity and acidity or basicity of the catalyst. This reaction is considered to take place through a carboanionic or carbocationic mechanism. However until now the subject of surface acidity/basicity and its correlation with catalytic activity and also the mechanism of double bond isomerization reaction is still under debate. In order to investi~ate the correlation between activity and surface acidity silica-alumina catalysts were calcined at a range of temperature 300-550 °c in order to produce a series of samples with different Bmnsted and Lewis acid site densities. The numbe~ of acid sites was measured by combined FTIR/gravimetric measurements from the adsorption of2,6 and 2,4lutidine and pyridine. For each catalyst, a cycle of I-butene isomerization reactions was carried out. Reactions were performed using a fixed bed reactor under a constant flow of I ml/min of I-butene in total flow of the gases 100 ml/min. The only products of this reaction were cis-butene and trans-butene. This study indicates that amorphous silica-alumina is an active catalyst for double bond isomerization. In agreement with previously studies, no dimerization, oligomerization, coke or by-product formation was found under the reaction conditions selected. However deactivation is observed especially during the first 50 min of the reaction. The calculated activation energy of cis-butene formation was 48±5 kJ morl consistent with values reported in the literature. The work presented aims at establishing a relationships between the type, or types of acidity and number of sites, with the activity in the isomerisation reaction.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available