The Influence of the Support on the Behaviour of Supported Metal Catalysts in Hydrocarbon Hydrogenation Reactions

Boumarafi, Belkacem (1986) The Influence of the Support on the Behaviour of Supported Metal Catalysts in Hydrocarbon Hydrogenation Reactions. MSc(R) thesis, University of Glasgow.

Abstract

Platinum and rhodium metal catalysts supported on a transition metal oxide titania, and on the non-transition metal oxides alumina and silica have been used to determine the possible effects of Metal-Support Interactions on metal surface areas and the catalytic hydrogenation of buta-1:3-diene. The adsorption of [14C]carbon monoxide on platinum and rhodium metal surfaces has been used to determine the metal surface area for each catalyst. The results of these determinations have shown that metal-support interactions are extant, particularly in the platinum and rhodium supported on titania catalysts, as revealed by a decrease in metal area following high-temperature reduction in hydrogen. Temperature-programmed reduction, has been used and the shapes of the reduction profiles determined for each catalyst. Comparisons have been made between platinum and rhodium supported on various oxides with regard to the structure of the reduction profiles, which vary from support to support particularly with regard to the temperature at which the main peak in the profile occurs. The hydrogenation of buta-1:3-diene over these catalysts has been found to occur in two distinct stages. In the first stage of the reaction buta-1:3-diene was predominantly hydrogenated to n-butenes, together with small amounts of n-butane, whilst in the second stage which was accompanied by an increase in rate, the n-butenes were further hydrogenated to n-butane. All three isomeric n-butenes are observed as initial products, but-1-ene being the major product over each catalyst and cis-but-2-ene being only a minor product. The selectivities for butene formation are relatively high over all catalysts studied. The variation of reduction temperatures of the catalysts, which causes a variation in surface area does not affect either the initial butene distributions or selectivities over any of the catalysts. Each catalyst underwent a change in activity with usage. With the platinum catalysts this was of the form of a straight deactivation to a steady state activity. However, with the rhodium catalysts the activity at first increased with usage passing through a maximum before following a normal deactivation curve to a steady state activity. Activation energies were determined for each catalyst. With most catalysts the variation of reduction temperatures did not affect the activation energy values except with Pt on TiO2, which gave a significantly higher value of activation energies when reduced at high temperature, suggesting the possibility that, in this case, metal-support interactions may have some effect on the activation energy.

• Item Type: Thesis (MSc(R))
• Qualification Level: Masters
• Keywords: Physical chemistry
• Date of Award: 1986
• Depositing User: Enlighten Team
• Unique ID: glathesis:1986-77408
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 14 Jan 2020 09:09
• Last Modified: 14 Jan 2020 09:09
• URI: https://theses.gla.ac.uk/id/eprint/77408