Aromatic reduction over supported modified platinum catalysts - Influence of a second metal on the sulfur resistance of platinum

Pt-M/Al2O3 bimetallic catalysts with M = Ge, An or Pd were prepared and characterised by H2O2 Volumetric titration and IR(CO) spectroscopy. The effects of the second metal on the sulfur resistance of platinum were investigated by the hydrogenation of orthoxylene. Compared to platinum monometallic reference catalyst, the bimetallic catalysts ranking in terms of hydrogenation activity was PtPd > PtAu >= Pt >> PtGe. Correlation between these catalysis results and electronic properties extracted from IR(CO), or orthoxylene hydrogenation without sulfur, shows that sulfur resistance of platinum can not be exclusively related to an electronic effect and an electrodeficient character of Pt surface atoms. The mechanism of sulfur poisoning is discussed.