A STUDY OF THE ACIDIC PROPERTIES OF PURE AND COMPOSITE OXIDES BY INVERSE GAS-CHROMATOGRAPHY AT INFINITE DILUTION

A family of n-alkenes and alkenes has been used in conjunction with the technique of inverse gas chromatography (IGC) to study the acidic properties of pure and composite oxides. Commercial and laboratory-prepared silica and alumina and alumina on silica composites derived from them were subjected to a modified Benesi titration scheme, and the results are compared to those obtained from IGC. We find that changes in acidity due to changes in composition of the samples can be determined from IGC data and the results are consistent with those obtained from the more conventional colorimetric titration. On the other hand, acidity changes due to dehydroxylation of the oxides can be easily monitored using IGC while the results from the modified Benesi titration are not sensitive enough to disclose any acidity changes. To our knowledge, this is the first application of IGC to study the surface acidity properties of composite oxides. The simplicity, sensitivity, and flexibility of IGC for study of catalysts and catalyst supports point toward its potential to add to the arsenal of techniques that characterize both commercial and laboratory prepared materials. © 1991.