Cel Laterites are residual products derived from a wide variety of rocks by intensive chemical weathering under strongly oxidising and leaching conditions. The main constituents of these residues are nickel, iron, titanium, silicon, vanadium, zirconium and aluminium, present in the form of hydroxides and/or oxides. The nature and chemical composition of laterite depend on its place of extraction and its particle size. Being available in abundance in Venezuela, this naturally occurring material is considered as a potential candidate as a good catalyst. This potentiality can be inferred from the presence of oxides with some surface acidity or basicity, in which catalytic activity is recognised. Another reason to consider the lateritic material as a catalyst is the presence of some chemical elements like iron which is active in hydrodesulphurisation to some extent.A set of Venezuelan laterites (LV) were chosen for this study. The samples were ground and sieved in order to obtain a particle size of less than 150 microns. Each sample was analysed in the natural state (NS) using X-ray photoelectron spectroscopy (XPS) and thermogravimetric analysis (TGA) and also after calcination up to 500 C under air (AC), again by XPS. The XPS results allow characterisation of the surface composition of natural laterites and the structural transformations they undergo during thermal treatment. The surface composition remains unchanged if the silicon aluminium ratio is considered, but presents a slight increase of the iron aluminium ratio and in a large extent a decrease of the oxygen aluminium ratio (loss of water, dehydroxylation). The TGA and differential themal analysis (DTA) results specify the range of temperature for which the transformations occur. Two endothermic phenomena appear at 250 C and 450 C respectively and are related to the weight loss observed in the TGA experiments. In this range of temperatures, according to the literature, phase transformations from gibsite to boehmi te and then to **-alumina take place. Further analysisof XPS data is needed in order to obtain more information about the phase transformations that occur in samples subjected to thermal treatments. These results will be correlated with the information obtained by using other techniques like X-ray diffraction. Program(-y) IC-ISC C - Activity (Euratom, EEC) on cooperation in science and technology, 1984- Temat(-y) Data not available Zaproszenie do składania wniosków Data not available System finansowania CSC - Cost-sharing contracts Koordynator Université de Lille I (Université des Sciences et Technologies de Lille Flandres Artois) Wkład UE Brak danych Adres Domaine Universitaire Scientifique 59655 Villeneuve d'Ascq Francja Zobacz na mapie Koszt całkowity Brak danych Uczestnicy (1) Sortuj alfabetycznie Sortuj według wkładu UE Rozwiń wszystko Zwiń wszystko Universidad de Los Andes Wenezuela Wkład UE Brak danych Adres Avenida 3 5251 Merida Zobacz na mapie Koszt całkowity Brak danych
