Hydrogen Exchange between Sulfated Zirconias and per Deutero- Benzene as Characterization of the Surface Acidity

Author： Armendariz H. Sanchez Sierra C. Figueras F. Coq B. Mirodatos C. Lefebvre F. Tichit D.

ISSN： 0021-9517

Source： Journal of Catalysis, Vol.171, Iss.1, 1997-10, pp. : 85-92

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Abstract

The surface acidity of sulfated zirconia has been investigated bydiffuse reflectance IR and¹H MAS-NMR spectroscopies. Bothtechniques give evidence of the existence of two types of acid sites:a weak acid characterized by an infrared band at 3630 cm^-1and an¹H NMR resonance at 3.5 ppm relative to TMS, and a strong acid characterized by resonances at 3300 cm^-1in infrared and 5.8 ppm in¹H NMR. The interaction of deuterated benzene with these solids also shows two types of acid sites: the weaker sites give hydrogen bonding with benzene, evidenced by a shift of the resonance frequency in infrared spectrometry. The presence of strong acid sites able to exchange protons with deuterated benzene has been ascertained by FTIR and NMR investigation of the adsorbed phase and by mass spectrometric analysis of the effluents. The catalytic properties in isomerization ofn-hexane are correlated with the presence of these strong acid sites, the formation of which depends on the type of preparation of the catalyst.