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.