THERMAL-DESORPTION AND INFRARED STUDIES OF AMINES ADSORBED ON SIO2, AL2O3, FE2O3, MGO, AND CAO

The adsorption of diethylamine and triethylamine on SiO2, γ-Al2O3, α-Fe2O3, MgO, and CaO at the solid/vapour interface has been studied by infrared spectroscopy and temperature-programmed desorption (TPD). At beam temperature hydrogen bonding between surface hydroxy groups and amine molecules (both amines) and dissociative adsorption (diethylamine only) occur on SiO2. Adsorption on the other oxides mainly involves the formation of coordination bonds between amine molecules and Lewis-acidic surface sites (coordinatively unsaturated cations). With increasing temperature during the TPD runs, amine molecules adsorbed on the different surface sites undergo chemical transformations (including CC-, CN-, and NH-bond breakages) which cause the desorption of characteristic reaction products. © 1990.