Temperature Programmed Desorption of Pyridine and 2,6-Dimethylpyridine from Differently Pretreated Pd/Al2O3 Catalysts

• Autorzy: Skotak M. , Karpiński Z.
• Języki publikacji: EN

Abstrakty

EN

The temperature programmed desorption (TPD) of pyridine and 2,6-dimethylpyridine from alumina and two alumina-supported palladium catalysts of different metal loadings (0.3 and 2.77 wt.% Pd) confirmed the presence of strong acid sites in the samples subjected to high temperature reduction at 600°C. Roughly similar amounts of both organic bases were desorbed from the catalysts which underwent similar pretreatments. However, 2,6-dimethylpyridine appears less strongly bonded than pyridine to Lewis acid sites in alumina, apparently because of some steric hindrance produced by the presence of methyl substituents in 2- and 6-position to the nitrogen lone pair. Thus, pyridine is better suited for probing evolution of Lewis acidity in alumina, brought about by high temperature reduction at 600°C.With increasing temperature during thermodesorption, both organic bases adsorbed on palladium-containing samples undergo transformation, leading to desorption of several products, among which hydrogen and nitrogen predominate. Introduction of increasing amounts of palladium to alumina makes the acidity probing difficult, because a considerable part of adsorbed organic base is decomposed on metal sites. Decomposition of pyridine and 2,6-dimethylpyridine may serve as a convenient probe of availability of palladium surface. After high temperature reduction of Pd/Al2O3 a considerable part of Pd surface is blocked by support species.

Słowa kluczowe

EN

pyridine; 2,6-dimethylpyridine; temperature programmed desorption of (TPD); acid sites; alumina; effect of pretreatment; Pd/Al2O3

• Wydawca: Polskie Towarzystwo Chemiczne
• Czasopismo: Polish Journal of Chemistry
• Rocznik: 2004
• Tom: Vol. 78 / nr 10
• Strony: 1953--1959
• Opis fizyczny: Bibliogr. 32 poz., rys.

Twórcy

autor

Skotak M.

• Institute of Physical Chemistry of the Polish Academy of Sciences, ul. Kasprzaka 44/52, PL-01224 Warszawa, Poland

autor

Karpiński Z.

• Institute of Physical Chemistry of the Polish Academy of Sciences, ul. Kasprzaka 44/52, PL-01224 Warszawa, Poland
• Faculty of Mathematics and Natural Sciences, Cardinal Stefan Wyszyñski University, ul. Dewajtis 5, PL-01815 Warszawa, Poland

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