Kinetics of Hydrous Aluminum Oxide Conversion in Mixtures of Amorphous Alumina Gels of Various Acid Reactivities

Mixtures of two amorphous alumina gels of different acid reactivity change physically and chemically upon aging until a constant state is reached. The gels, when individually aged, retain their initial properties. The end-point appearance, viscosity, X-ray diffraction pattern, DTA thermogram, acid-insoluble fraction, and acid reactivity of the mixture are identical to those of the gel having the lower acid reactivity. The change in properties appears to be due to the conversion of the gel having the higher reactivity into the less reactive form. The rate of conversion is first-order, temperature-dependent, and directly dependent on the initial concentration of the less reactive gel.