Specific Behavior of Tailor-Made Pt–Ge/Al2O3 Catalysts in Transformation of Hydrocarbons

Germanium in amounts corresponding nominally to 2 or 1/8 monolayers was added to a 1% Pt/Al2O3 catalyst by controlled surface reaction. These catalysts, noted as Ge2 and Ge1/8, were tested in transformation of hexane, benzene, and cyclohexene in hydrogen excess and compared with the Ge-free parent sample. All catalysts produced isomers, methylcyclopentane, fragments, benzene, and hexenes from hexane at T=603 K. Ge2 gave the highest TOF values, likely by preventing carbon accumulation. The selectivity of a saturated C6 product was highest on Ge1/8, which also gave cyclohexane in amounts that increased as more H2 was present. Particular Pt(111) arrangements required for the formation of benzene may have been selectively blocked by Ge on the Ge1/8 sample. This was supported by comparing benzene and cyclohexene transformation. The Ge1/8 sample was almost inactive in benzene hydrogenation, and active in cyclohexene transformation, whereas the parent and the Ge2 sample were active in both reactions. The catalyst Ge1/8 may serve as a basis for development of novel reforming catalysts producing isomers and less aromatic compounds.