The Structure of Hexaaluminate and Application in High-Temperature Reaction

Hexaaluminate materials exhibit remarkable thermal stability due to their peculiar layered structure. The Al3+ ions in the hexaaluminate lattice can be substituted by transition or noble metals, giving rise to redox centers for a variety of reactions. Oxygen in the mirror plane of hexaaluminate is loosely packed, making it a preferential diffusion route of oxygen. All of these favor the application of hexaaluminate in high-temperature oxygen-involved reaction. In this review, the structure of hexaaluminate is firstly introduced. Furthermore, the effect of structure type (magnetoplumbite and beta-Al2O3) and metal substitution on the microstructure of hexaaluminate (especially metal chemical state) are crefully described. Then we discuss recent advances of hexaaluminate in high-temperature oxygen-involved reactions, such as, catalytic combustion of CH4, process-gas N2O abatement, decomposition of N2O as a propellant, CH4 chemical looping combustion and reforming, with a special emphasis on the relationship between the microstucture and reaction performance. At last, a brief summary and an outlook are given