ISSN:
1572-879X
Keywords:
superacid catalysts
;
sulfated zirconia
;
surface Lewis acidity
;
CO adsorption
;
IR spectra of surface species
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
Notes:
Abstract In the preparation of active SO4-ZrO2 catalysts, several steps involving various chemical and/or physical processes are necessary. In particular it has been reported that, after sulfation of amorphous Zr hydrates, a calcination atT calc〉773 K is needed to guarantee the crystallization of ZiO2 in the tetragonal phase. By the use of a stabilized tetragonal ZrO2, it is here demonstrated that a calcination atT calc〉773 K is indeed necessary for all SO4-ZrO2 systems, and that its actual role is the selective elimination of sulfates from highly energetic crystallographic defects. The calcination step atT calc〉773 K so creates the conditions for the formation of strong Lewis acid centres, that are necessary in the catalytic process, and the presence of which is here monitored spectroscopically by the reversible adsorption of carbon monoxide.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00811720
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