Study of the support evolution through the process of preparation of rhodium/lanthana catalysts

Abstract

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.