A series of synthetic minerals based on hydrotalcite, Mg₆Al₂(0H)₁₆C0₃.4H₂0, has been prepared using coprecipitation techniques in order to yield materials with similar morphologies and yet greater potential for forming heterogeneous catalysts after a relatively low temperature activation step. The idealised formulae of these hydrotalcite-type compounds (HTc's) covered a range of increasing Fe¹¹-for-Mg¹¹ substitution from Mg₆Al₂(0H)₁₆C0₃.4H₂0 through to Fe₆Al₂(OH)₁₆C0₃.4H₂0. These catalyst precursor materials have been characterised using a range of techniques which include infrared spectroscopy, X-ray powder diffraction, scanning electron microscopy and differential thermal analysis. A number of aluminium-substituted iron oxides have also been prepared both directly and via the iron oxide intermediate known as 'green rust', which is isostructural with hydrotalcite. These materials were prepared and characterised for comparison with the HTc's due to their chemical and structural similarities and their potential for use as heterogeneous catalysts.
A study of the calcination of the HTc's has been undertaken, with the aim of producing high porosity/surface area materials whilst retaining the platelet morphology displayed by the HTc's and attaining as low a maximum calcination temperature as possible. The effects of various temperature regimes were explored and the calcined materials characterised.
The use of the prepared HTc's as base catalysts was investigated using the
cyanoethylation of a range of alcohols as a test reaction. The study included a study of the activation of the HTc's prior to the reaction and their subsequent activity and selectivity for the reaction.
The activity and selectivity of the calcined HTc's for the oxidation of sulfur dioxide to sulfur trioxide and the dehydrogenation of cyclohexane was also investigated. A purpose-built test rig utilising in-line gas chromatography was constructed in order to do this.