Determination of concentration of basic sites on oxides by IR spectroscopy

Abstract

As it is commonly known, CO2 reacts simultaneously with basic O2− and basic OH sites on oxides forming carbonates and bicarbonates, which can be followed by infrared spectroscopy (IR). However, here, we succeeded to elaborate experimental conditions under which CO2 reacted solely with O2− forming CO32− for ZrO2 and CeO2, and calculated the extinction coefficients of diagnostic bands of carbonate and bicarbonate species. For the first time, the developed IR method enabled the concentrations of O2− and basic OH for ZrO2, CeO2, Al2O3 and CuO to be measured separately. Moreover, in the case of all IR studied oxides, the sum of concentrations of O−2 and basic OH basic sites was comparable with the concentration determined by pulse adsorption of CO2. Thus, the presented extinction coefficients can be applied for IR basicity studies of various basic catalysts. We also followed the effect of thermal treatment on basicity of oxides.