Selective Oxidation and Kinetic Modelling of Isobutane Over Phosphomolybdate Substrates

Abstract

This thesis is concerned with the oxidation reaction processes associated with phosphomolybdic acid (H₃[PMo₁₂O₄ₒ]) and derivatives. The derivatives are synthesized via cation exchange of the protons of phosphomolybdic acid with various metal cations. These metals are sourced from selected regions of the periodic table, with a view to understanding and correlating the influence of elemental properties on oxidation activity and selectivity. All phosphomolybdates have been analysed by X-ray diffraction. The structure of these compounds varies significantly according to cation selection; triclinic, body centred cubic and primitive cubic phases were identified. Relationships between cation volume contributions and phase compositions of the phosphomolybdate structure have been established. Caesium phosphomolybdates were investigated using X-ray fluorescence in order to determine compositional information. It was found that this technique was unreliable and hence inappropriate for phosphomolybdates. UV-Visible spectroscopy was applied to solutions of phosphomolybdates in order to ascertain electronic transitional properties and a surface analysis was conducted to elucidate pore and surface area features.