Short-Chain Alkane Activation. An Investigation of SO2-Promoted Propane Oxidation over Pt (111) and Pt-AlOx Model Systems

SO₂ chemisorption on oxygenated Pt(111) enormously enhances the dissociative chemisorption and subsequent combustion of propane. This activation of the metal surface is induced by an adsorbed sulfoxy species which is formed > 220 K. In the absence of adsorbed SO₂ the sticking probability of propane is immeasurably small. However in the presence of SO₂, the precursor-mediated initial sticking probability rises from ∼0.02 at 300 K to ∼ 0.15 at 160 K. XPS and HREELS measurements identify the active species as SO₄ ^2-, and also demonstrate the consumption of SO₄ during the oxidation reaction. Coincident CO₂ and SO₂ formation suggest decomposition of a complex reaction intermediate: this is supported by isotope experiments involving CO adsorption onto SO₂/¹⁸O₂ precovered Pt(111). Propane oxidation over sulphated AlO_x films on Pt(111) is also reported, with increased activity for submonolayer oxidised Al films being observed compared to clean Pt(111).