Alkane isomerization on highly reduced Pd/Al2O3 catalysts. The crucial role of Pd-Al species

• Published in: Catalysis communications 2019-04, Vol.123, p.17-22
• Main Authors: Radlik, Monika, Małolepszy, Artur, Matus, Krzysztof, Śrębowata, Anna, Juszczyk, Wojciech, Dłużewski, Piotr, Karpiński, Zbigniew
• Format: Article
• Language: English
• Subjects: Effect of catalyst reduction; N-Hexane isomerization; Pd-Al active centers; Pd/Al2O3; Pd0.82Al018
• ISSN: 1566-7367; 1873-3905
• DOI: 10.1016/j.catcom.2019.02.002

Highly reduced (at 500 and 600 °C) 1 wt% Pd/Al2O3 samples showed remarkable isomerization selectivity in n-hexane conversion, >80%, in agreement with previous reports. The catalytic behavior of highly reduced Pd/Al2O3 becomes typical of platinum, the metal regarded as unique in alkane isomerization. Although not detected in low metal loaded catalysts, Pd-Al species evidenced by formation of Pd-Al alloys in 5 wt% metal loaded catalysts appear essential active sites responsible for n-hexane isomerization. Other possible reasons (contribution from alumina acidity and changes in the structure of metal surface) were analyzed and discarded. A mechanistic rationale for the improvement of n-hexane isomerization is outlined. [Display omitted] •Highly reduced Pd/Al2O3 show high isomerization selectivity in hexane conversion.•Catalytic behavior of highly reduced Pd/Al2O3 resembles that of platinum.•Effect of support acidity on catalytic behavior of Pd/Al2O3 ruled out.•Phase transformation 5 wt% Pd/Al2O3 → Pd-Al alloy evidenced by XRD.•Electronic properties of Pd-Al clusters explain high rate of alkane isomerization.