City Research Online

Abstract

Adsorption studies were carried out in a gravimetric adsorption apparatus, a quartz spring balance being used instead of a more sensitive vacuum microbalance (due to lack of finance). This was connected to gas reservoirs and a vacuum pump. Low pressures (< ltorr) were indicated on Pirani and Penning vacuum gauges, higher pressures were measured on a silicone oil U-tube manometer.
To test the balance BET measurements using nitrogen were made on a Sn-Sb oxide catalyst and carbon-black powder. The physisorption study was satisfactory.
Chemisorption of propene, 1-butene and oxygen was studied on Sn-Sb oxide catalyst. The chemisorption work allowed the calculation of isosteric heats of adsorption from a Clapeyron-Clausius type of equation which were found to decrease in complex ways from 28.08, 95.09 and 66.65 kJ/mol to less than 1 kJ/mol for oxygen, propene and 1-butene respectively. Entropies of adsorption were also calculated and were found to vary in a complex fashion with coverage indicating the importance of lattice oxygen, surface complexes and the complex nature of the mechanism of adsorption.
Data was fitted to various models, the best fit being an empirically modified Langmuir isotherm to some of the olefin data. No satisfactory fit was attained with the oxygen data.

Publication Type:	Thesis (Doctoral)
Subjects:	Q Science Q Science > QD Chemistry
Departments:	School of Science & Technology School of Science & Technology > School of Science & Technology Doctoral Theses Doctoral Theses

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