The study of nonstoichiometric alumina-aluminum phosphates as novel supports for catalytic metals

Mixed oxides have attracted significant interest recently as novel catalytic materials. One such mixed oxide is alumina-aluminum phosphate (AAP). The purpose of this study was to investigate the physical and chemical implications of varying the P/Al ratio. In particular, it was desired to determine the dependence of the catalytic properties of the AAP's on composition as well as the effect of composition on the properties of metals highly dispersed on their surfaces.;It was found that phosphorus, when co-precipitated in a 1:1 mixture or less with aluminum, forms an amorphous binary oxide with physical and textural properties which indicate that it is a true micro-composite and not just an admixture of the individual materials. The ratio of P/Al was found to greatly affect the pore volume, pore radius, and specific surface area of the support. Effects of composition were also found for the thermal stability and microcrystallinity of the samples.;The effect of phosphorus content is AAP binary oxides was examined in order to obtain a better understanding of its effect on the chemical properties of the oxide surface. While the activities observed for these oxides indicate that they are not effective as acid catalysts, their use as support materials for catalytic metals seems promising. The results indicate that the stoichiometric ratio of phosphorus to aluminum can affect the acid-base properties of this oxide system. The effect of phosphorus content was most evident in its ability to influence the overall activity/selectivity of the AAP in catalyzing isopropanol decomposition and propylene oxide isomerization.;A series of alumina-aluminumphosphate supported rhodium catalysts were examined in terms of their adsorptive and reactive behavior. The results indicate that both the phosphorus content of the support and the reduction temperature of the catalyst can affect the overall catalytic nature of rhodium. A comparison of these results with a previous study for ruthenium/aluminophosphate catalysts points towards the variability in the strength of interaction between the metal and the support. Possible explanations as to the cause of this variability in interaction are presented. (Abstract shortened with permission of author.)...