Destructive adsorption of carbon tetrachloride on lanthanum and cerium oxides

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 spectrosco py and in situ Raman spectroscopy as a function of the reaction temperature and the amount of CCl4 injected. La2O3 was much more reactive than CeO2, a nd CCl4 destruction started at around 300 degrees C with the rapid formatio n of LaOCl, and the release of CO2 into the gas phase. The complete transfo rmation 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 degrees C, and was accompanied by t he reduction of Ce(IV) to Ce(III) and the formation of CeOCl as an intermed iate product. The complete transformation of CeO2 into CeCl3 was only obser ved at reaction temperatures near 600 degrees C. These results are compared with those recently reported for alkaline earth metal oxides.