Synthesis and characterization of silica-alumina prepared from tetraalkylammonium hydroxides

The synthesis and textural properties of amorphous silica-alumina prepared from tetraalkylammonium solutions in presence of alkali cations (sodium and potassium) have been studied. Alkali cations are needed to polymerize silicon and aluminium from the solution and they are preferentially incorporated into the silica-alumina. All the aluminium in the solidn is present in tetrahedral coordination. The samples are dealuminated and dehydroxylated by calcination in air, leaving materials with surface areas close to 300 m2g−1, and very narrow pore distribution, centered at ca. 20 Å of pore radii. Steaming leads to deep dealumination, while the surface area strongly decreases and the microporous structure collapses.