Destructive adsorption of carbon tetrachloride on lanthanum and cerium oxides

Abstract

The destructive adsorption of CCl4 on La2O3 and CeO2 in the absence of any oxidant, such as oxygen, has been studied by X-ray photoelectron spectroscopy and insitu Raman spectroscopy as a function of the reaction temperature and the amount of CCl4 injected. La2O3 was much more reactive than CeO2, and CCl4 destruction started at around 300°C with the rapid formation of LaOCl, and the release of CO2 into the gas phase. The complete transformation of LaOCl into LaCl3 was much more difficult to obtain, and required high reaction temperatures and large amounts of CCl4. In the case of CeO2, CCl4 destruction started at around 450°C, and was accompanied by the reduction of Ce(IV) to Ce(III) and the formation of CeOCl as an intermediate product. The complete transformation of CeO2 into CeCl3 was only observed at reaction temperatures near 600°C. These results are compared with those recently reported for alkaline earth metal oxides.