New approach to the novel synthesis of boehmite (γ-AlOOH) by microwave irradiation of gibbsite: Kinetics of solid-phase reactions and dielectric properties of the reactants

Microwave irradiation of gibbsite is suggested as a method of obtaining crystalline boehmite. The kinetics of solid-state transformations of gibbsite under microwave radiation has been investigated, and the dielectric properties of the initial and microwave-activated gibbsite samples have been determined. Extending the gibbsite irradiation time leads to an increase in tanδ. This indicates that microwave-activated gibbsite has a stronger capacity for dissipating microwave energy owing to the formation of an amorphous component containing a variable amount of weakly bound molecular water. The general chemical formula of the amorphous component can be represented as Al2O3 · xH2O (0.5 < x < 3.0). The results of this study can provide a basis for developing new, low-waste, resource- and energy-saving methods for the synthesis of crystalline boehmite and for converting it into γ-Al2O3 with acid-base and textural properties that are atypical of the known low-temperature modifications of Al3+ oxides.