Study of the support evolution through the process of preparation of rhodium/lanthana catalysts
The evolution undergone by the support throughout the processes involved in the preparation of some lanthana-supported rhodium catalysts has been studied by thermal gravimetry, temperature-programmed decomposition – mass-spectrometry, temperature-programmed reduction – mass-spectrometry and X-ray diffraction. Following the impregnation process, the support consists of partially carbonated lanthanum hydroxide. A study of the reduction process shows that, at 623 K, a catalyst that can be described as Rh/LaO(OH) is obtained. Reduction temperatures as high as 723 K are necessary to prepare true Rh/La2O3 catalysts. In contrast to results observed for the dehydration of the support, the reduction of the carbonated phase on lanthana is strongly activated by the presence of the supported rhodium.