Energies of different surface rehydration processes on “eta”, “theta” and “alpha” aluminas

Abstract

The adsorption of water vapour on completely dehydroxylated samples of η-, θ- and α-alumina has been investigated at 150°C by a microcalorimetric technique. The same rehydration mechanisms have been found on all three aluminas, essentially dissociative and coordinative chemisorption. The hydroxylation process appears to be inhibited on passing from η- to θ- and α-alumina, the coordination of molecular water in different forms being favoured. However decreases in adsorption capacity and energies are evidenced, which may be correlated both with different alumina structures and with the modification of surface reactivity induced by the increasing preparation temperatures.