Relation between the hydroxylation state of zirconia, the sulfate promotion method, and the catalytic activity of SO{sub 4}{sup 2-}-ZrO{sub 2} catalysts
- Instituto de Investigaciones en Catalisis y Petroquimica, Santa Fe (Argentina)
Zr(OH){sub 4} samples were prepared from ZrOCl{sub 2} and ZrCl{sub 4}; they were calcined at temperatures between 100 and 620{degrees}C and were sulfated with H{sub 2}SO{sub 4} solutions. The catalytic activity in n-butane isomerization of these samples (at 300 {degrees}C, 1 atm, and WHSV = 2.5 h{sup -1}), previously activated in air at 620{degrees}C is not well correlated with their textural properties or the SO{sub 4}{sup 2-} concentration. Zr(OH){sub 4} samples calcined at temperatures higher than 375{degrees}C are crystalline and adsorb SO{sub 4}{sup 2-} groups, but which are not active catalytically. The catalytic activity decreases with the calcination temperature in a similar way as the OH groups (determined by chlorination) are eliminated, forming less reactive surface groups. When the crystalline samples are sulfated with H{sub 2}SO{sub 4} vapors, catalytically active materials are produced, irrespective of the crystalline state. The drastic sulfation overcomes the inertness of the crystalline surface and catalytic active sites for n-butane isomerization are produced. This in situ resulfaction may also compensate the sulfur losses during the reaction. 21 refs., 8 figs., 5 tabs.
- OSTI ID:
- 478765
- Journal Information:
- Journal of Catalysis, Journal Name: Journal of Catalysis Journal Issue: 2 Vol. 166; ISSN 0021-9517; ISSN JCTLA5
- Country of Publication:
- United States
- Language:
- English
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