TIN PLATINUM ON ALUMINA AS CATALYST FOR DEHYDROGENATION OF ISOBUTANE - INFLUENCE OF THE PREPARATION PROCEDURE AND OF THE ADDITION OF LITHIUM ON THE CATALYTIC PROPERTIES/

A series of monometallic and bimetallic Pt and PtSn catalysts, modifie d or not by the addition of Li, was studied in the dehydrogenation of isobutane to isobutene reaction. Special emphasis was devoted to the b ehavior of catalysts obtained following different preparation procedur es. In relation to the addition of lithium, a strong dependence of the catalytic properties on the order in which Li was added was observed. Two alternatives were analyzed: (a) the support was modified by addin g lithium onto it, and then it was impregnated with the metallic precu rsors; (b) the support was impregnated with the metallic precursors an d afterward lithium was added. The application of surface organometall ic chemistry on metals (SOMC/M) techniques for the preparation of PtSn bimetallic catalysts led to solids having a better performance than w hen conventional techniques (successive impregnations with inorganic p recursors) were used. Selectivities close to 100% at a high level of a ctivity were obtained when lithium was added on PtSn catalyst (alterna tive b) prepared from SOMC/M techniques. These systems also showed a g ood performance in deactivation-regeneration cycles.