The main objective of this research was to develop a more complete understanding of underlying chemical processes taking place in the one-pot modified sol-gel synthesis of ordered mesoporous alumina and alumina-based metal oxides. This was accomplished through exploration of the effects of altering synthesis parameters (polymer template, acid concentration, etc.), substitution of constituents (nickel, titanium, etc.) or by the introduction of additives (co-solvent molecules) on the resulting material’s structural properties. In tandem with this approach was the optimization of these alterations in order to produce well ordered mesoporous alumina and alumina-based metal oxides. A secondary goal was in creating general synthesis strategies for tailoring these materials for use in a number of applications.
This project resulted in an increased understanding of the cooperative self-assembly process and the effects of various synthesis components and conditions. The most influential variable in the synthesis mixture is the polymer template which determines pore morphology. Variations from optimal resulted in small decreases in both surface area and pore volume. The second most influential variable is acid concentration. Acid concentration is directly proportional to pore width, up to a limiting concentration. Higher acid concentration also led to higher thermal stability and evidence of transitions from the hexagonal to the cubic phase. The addition of co-solvent molecules at low temperature affected the resulting pore volumes and induced microporosity. Unlike their siliceous counterparts, ordered mesoporous alumina did not display the clear relationship between co-solvent concentration and mesopore width. Materials were found to be stable and the synthesis was highly reproducible.
A sample preparation method for alumina-based metal oxides was demonstrated. This method was found to be limited by additional metal, it’s suitability for an acidic synthesis and it’s compatibility with the alumina framework. However, it was shown that alumina-based metal oxides (specifically nickel- and titanium-aluminum oxide) result in thermally stable, ordered (up to ~20% additional metal) mesopores with a high degree of thermal stability and crystallinity. Materials were present as a mixed metal phase at the stoichiometric equivalent with excesses of either metal at other equivalents. These materials are currently being used in research labs around the world to determine their suitability for numerous industrial applications.