MICROCALORIMETRIC STUDY OF THE ACIDITY AND BASICITY OF METAL-OXIDE SURFACES

The adsorption of probe molecules such as NH3 and CO2 was studied on about 20 simple metallic oxides by use of microcalorimetry in order to determine the number and character of basic and acidic surface sites. Microcalorimetry allowed a simultaneous determination of the strength and energy distribution of the adsorption sites. The adsorption isotherms, the differential heats, the integral heats, and the energetic histograms are given for NH3 and CO2 adsorptions. Relationships between the average adsorption heats of NH3 and CO2 have been found as a function of the ionic character percentage and of the charge/radius ratio.