STUDY BY EXAFS AND TEM OF THE EFFECT OF THE REDUCTION-OXIDATION CYCLES OVER PT AL2O3-K AND PTSN/AL2O3-K CATALYSTS/

TEM and X-Ray absorption spectroscopy at the Pt L(III) edge have been used to study the effect of several consecutive reduction-oxidation cy cles on the state of platinum for two Pt/Al2O3-K and PtSn/Al2O3-K cata lysts used industrially for the selective dehydrogenation of high mole cular weight paraffins. The results indicate that, whereas the size of the platinum oxide particles in the Pt/Al2O3-K monometallic catalyst increase after the different reduction-oxidation cycles, the presence of tin induces that platinum binds more strongly to the alumina surfac e, avoiding the sintering of platinum during the different reduction-o xidation cycles.