An intermittent temperature-programmed desorption method for studying kinetics of desorption from heterogeneous surfaces

Reported results show the interest of an intermittent temperature-programmed desorption (ITPD) technique for gaining information on thermodynamics and desorption kinetics of small molecules from the surface of dispersed solids. This technique is a differential form of TPD where a saw-tooth heating program is used to generate a sequence of interrupted desorptions. Two examples are described and discussed in terms of heat of desorption, activation energy of desorption and frequency factors. We first considered ammonia desorption from two different zeolites, that is H-ZSM5 and H-Omega, in order to get information on their surface acidity. Secondly, oxygen desorption from SnO2 was investigated in order to get quantitative data on O-2/SnO2 interaction, this oxide being used in sensors of reducing gases in the atmosphere. (C) 2004 Elsevier B.V. All rights reserved.