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2 Bulletin of the Polish Academy of Sciences. Chemistry

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Solid acids as catalysts for cumene cracking: heteropolyacids as compared with zeolites. Part. 1. Reaction and coke formation

Małecka-Lubańska A., Poźniczek J.

Bulletin of the Polish Academy of Sciences. Chemistry

2002

Vol. 50, No.2

219-236

The catalytic properties of dodecatungstosilicic acid H(4)SiW(12)O(40 (HPA) and NaHY-88 zeolite in cumene cracking reaction were compared. HPA exhibits catalytic activity at temperatures lower (below 160° C) than NaHY-88 (above 170°C) but its deacti-vation is faster. Mass balance shows that in both cases a certain deficit exists due to the formation of carbonaceous deposits. It has been shown that in the formation of deposits both chain hydrocarbons ("propylene deposit") and aromatic ones ("cumene deposit") participate. In the case of both catalysts the course of catalytic reaction and deposit formation were influenced by the contact time. The results enabled us also to propose some conclusions concerning the geometry of deposit distribution in both catalysts.

The reaction of giant wheel polyoxomolybdate clusters with ethanol

Bielański A., Małecka-Lubańska A., Poźniczek J., Müller A., Krickemeyer E., Diemann E.

Bulletin of the Polish Academy of Sciences. Chemistry

2001

Vol. 49, No. 1

85-99

The conversion of ethanol at 100-280° C was used in order to characterise the redox and acid centres present in Na15{0.5[Mo(152)O(457)H14(H(2)O)68] • 0.5[Mo(154)O(462)H(2)14 (H(2)O)(70]}-ca. 400 H(2)O (1). It is concluded that Mo(VI)/Mo pairs at the external surface of the rings, of which the structure of 1 is composed, are the redox centres active in ethanol dehydrogenation to acetaldehyde. Simultaneous ethanol dehydration to diethyl ether or ethylene is a typical reaction occurring on acid centres. It is suggested that OH groups situated in (u3-0)(2)0(2) tetrahedrons inside the ring structure play such role. The formation of ethane predominating at highest temperatures is attributed to secondary reactions of primary ethylene.