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Title: Selectivity in catalytic reactions of acetylene
Author: McGown, William Taylor
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1978
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Studies have been made of the kinetics of the hydrogenation of mixtures containing 2% of acetylene in ethylene on an alumina supported palladium catalyst in a static system. Information has been obtained about the nature of the selectivity of the reaction of acetylene. Detailed analyses of the kinetics have been made as the ratio of the pressures of acetylene to ethylene decreases and subsequently as the remaining hydrogen is used up. The poisoning action of carbon monoxide, which selectively inhibits the hydrogenation of ethylene, has also been studied. Tracer studies using carbon 13 labelled acetylene, light ethylene and hydrogen with analysis by combined gas chromatography-mass spectrometry, have shown unambiguously that ethane produced from the hydrogenation of a mixture of acetylene in ethylene comes predominantly from the ethylene. The reaction between acetylene, ethylene and deuterium gives a greater understanding of the surface processes involved and produces ethane which is mainly ethane-dt. It is postulated that two types of site exist on the surface, type X which hydrogenates both acetylene and ethylene and on which acetylene is adsorbed - 2200 times more strongly than ethylene at 293° K and type Y which is easily poisoned by carbon monoxide and can hydrogenate ethylene even in the presence of acetylene. The hydrogenation of acetylene has also been investigated in a spinning-basket reactor. The rate of disappearance of acetylene was found to be controlled by pore diffusion at low acetylene concentrations and was independent of acetylene at high acetylene pressures. In the non-diffusion-controlled region the reaction of acetylene was first order in hydrogen and the rate of ethane formation was independent of both the acetylene and ethylene pressures. This latter observation is consistent with the presence of two types of site. The nature of the C, products has been shown to be dependent on the packing of adsorbed acetylene molecules and on the availability of surface hydrogen. The analysis of a heavy involatile product is also reported.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available