Thermogravimetric adsorption data for CzH4 and H 2 0 and i.r. and n.m.r. spectroscopic results are combined to obtain information on the role played by acidic Bronsted sites in the H-ZSM-5 zeolite in the adsorption and activation of C2H4. Water and ethene compete for such sites in various ways which depend on the pretreatment of the zeolite. Physisorbed water prevents the adsorption of C2H4. Ethene is readily activated and reacts on the Bronsted acidic sites, even at room temperature. There is further evidence for the formation of carbenium-type intermediates.

No abstract

Ein überraschendes Verhalten bei der Desorption aus Silicalit zeigen von den n‐Alkanen mit vier bis zehn C‐Atomen n‐Hexan und n‐Heptan. Während die längeren und kürzeren n‐Alkane in einem Schritt desorbieren, ist die Desorption von n‐Hexan und n‐Heptan zweistufig. Diese Ergebnisse können durch ein kommensurables Einfrieren erklärt werden, ein Phänomen, das kürzlich anhand der Ergebnisse von Computersimulationen vorausgesagt wurde.

No abstract

CoAPO Molecular Sieve Acidity Investigated by Adsorption Calorimetry and IR Spectroscopy.-Adsorption calorimetric measurements on Co-and Si-substituted show that the adsorption potential for acetonitrile, a probe allowing investigations of both Lewis and Broensted acidity, is enhanced upon Co incorporation. From the heats of adsorption the formation of strong acid sites due to Co incorporation and of weaker acid sites, probably P-OH, are indicated. The presence of some Broensted-bonded ammonia and acetonitrile in combination with Lewis-bonded species is shown by IR measurements of adsorbed NH3 and acetonitrile. While the Broensted-bonded species are presumably due to interaction of the base with weakly acidic P-OH groups, the Lewis-bonded species yield from coordination of the lone pair of the base to lattice Co. -(JAENCHEN, J.; PEETERS, M. P. J.; VAN WOLPUT, J. H. M. C.; WOLTHUIZEN, J. P.; VAN HOOFF, J. H. C.; LOHSE, U.; J. Chem. Soc., Faraday Trans.: Phys. Chem. Chem. Phys. 90 (1994) 7, 1033-1039; Schuit Inst. Catal., Eindhoven Univ. Technol., 5600 MB Eindhoven, Neth.; EN)