Exceptional catalytic performance of Au–Pt/γ-Al2O3 in naphtha reforming at very low Au dosing levels

The catalytic behavior of Au–Pt bimetallic nanoparticles supported on γ-Al2O3 for the reforming reaction of a real desulfurized medium naphtha feed has been investigated. Composite catalysts containing 0.7 wt% metal(s) with Au/Pt weight ratios of 0:100, 1:99, 5:95, and 50:50 have been studied. XPS analysis showed that the ratio of 1:99 results in a distinct positive character of Pt in the Au–Pt nanoalloy. We show for the first time that through colorimetric analysis that the catalyst synthesized with the Au/Pt ratio of 1:99 exhibits clear surface plasmon resonance effects under visible light at 570 nm, peculiar to the electronic configuration supported by the XPS analysis. Naphtha reforming catalytic tests were performed in a WHSV range of 2–6 h−1, at 485 °C. The pressure was 5 bar, typical for continuous catalytic reforming processes. The Au/Pt ratio of 1:99 resulted in a distinct performance, i.e. maximum naphthenes conversion, maximum aromatics production and least production of benzene and hydrocarbons with a carbon number equal or less than 5. This was attributed to the formation of near-surface Au–Pt alloy with an Au mono-sublayer in the presence of H2 during the reaction. The optimal catalyst exceptionally favors dehydrogenation/dehydrogenation over hydrogenolysis reactions.