Reactions of unsaturated hydrocarbons catalysed by transition metal compounds
A range of different heterogeneous catalysts for the isomerisation of ortho-xylene have been prepared and evaluated. These included commercially-available samples, supported metal catalysts and zirconia-based catalysts. The greatest activity was seen for the former, which was found also to be active for a number of related reactions. Zirconia-based catalysts, in particular sulphated zirconia, gave significant activity. It was possible to prepare a catalyst to give 9.5% conversion of ortho-xylene per gram of catalyst with good selectivity to the meta isomer. The catalyst was prepared in two ways, either by the action of ammonium sulphate on "zirconium hydroxide", a hydrated zirconia precursor, or by precipitation from a sulphuric acid-containing solution of zirconium (IV) propoxide. The factors in the synthesis procedure which affect the catalytic performance of the catalyst were investigated. These included choice of reagents, preparative method and calcination procedure. This information was used to prepare an 'idealised' catalyst, which showed activity for a number of reactions of commercial interest. A range of different aminophosphine complexes based on the reaction of a N,N'- substituted diamine with chlorodiphenylphosphine have been prepared for subsequent study as ligands in complexes active in homogeneous catalysis. Palladium and platinum complexes of the type [(diaminodiphosphine)MCl(_2)] have also been prepared and characterised. A number of x-ray diffraction analyses have been performed, which along with other data has allowed the solid state and solution structures to be discussed. The relative reactivities of the ligands have been determined by reactions with manganese pentacarbonyl bromide and also with palladium dichloride complexes. This depends largely on the steric requirements of the ligand in question. The potential of these ligands in catalysis has been evaluated by the performance of their platinum dichloride complexes in the tin (II)-promoted hydroformylation of styrene, and their palladium acetate complexes for the methoxycarbonylation of ethene.