Simulating temperature programmed desorption of water on hydrated gamma-alumina from first-principles calculations.

The knowledge of the properties of gamma-alumina is of great importance in order to control its surface for numerous applications. We investigate the kinetic behavior of the hydrated alumina (110) surface toward water desorption: the minimum energy path is presented for successive desorption steps starting from the completely hydrated surface toward the dehydrated one. It appears that water desorption is a non activated process. A kinetic model is proposed based on an extension of the Eyring theory. This model is a useful tool to understand the evolution of water coverage during the pretreatment of alumina. It is then used to model temperature programmed desorption experiments for various heating rates. The shape of the desorption curve is qualitatively reproduced, and the differences between theory and experiments are discussed.