Study of the properties of supported Pd catalysts for steam and autothermal reforming of methane

Abstract

The effect of support kind on the structure, surface properties and catalytic behavior of Pd catalysts supported on alumina and mixed La2O3–Al2O3 oxides, prepared by impregnation and sol–gel method was studied. It was found that the catalytic performances of Pd catalysts in steam reforming (SR) and autothermal reforming (ATR) of methane were significantly affected by the kind of support. The highest specific reaction rate and TOFsCH4 of La-containing Pd catalysts in SRM were related to the electronic interaction between Pd and modified alumina support surface with La oxide species and formation of Pd0[Pdδ+OxLa] like species, promoting the CH4 activation and carbon oxidation. Despite the filamentous carbon formation these catalysts exhibited the highest activity and stability in ATR caused by the presence of small Pd particles with average particle size of about 14–17nm. It was shown that the wide particle size distribution up to 70nm and the formation of encapsulated carbon species are responsible for the fast deactivation of non-La promoted Pd/Al catalyst.