Characterization of the acid strength of SiO[sub 2]-ZrO[sub 2] mixed oxides

Journal Article · Mon Aug 01 04:00:00 EDT 1994 · Journal of Catalysis; (United States)

DOI:https://doi.org/10.1006/jcat.1994.1253· OSTI ID:6879586

Bosman, H J.M.; Kruissink, E C; Spoel, J van der; Brink, F van den ^[1]

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1. DSM Research B.V., Gelenee (Netherlands)

The preparation of SiO[sub 2]-ZrO[sub 2] mixed oxides and the single oxides SiO[sub 2] and ZrO[sub 2] from H[sub 2]SiF[sub 6] and/or H[sub 2]ZrF[sub 6] is described. The catalysts are characterized using Hammett colour indicators, temperature programmed desorption of ammonia, XRD, XPS, and infrared spectroscopy. New IR bands and absence of XRD crystallinity show mixing of SiO[sub 2] and ZrO[sub 2] on an atomic scale in the amorphous coprecipitate. However, as could be concluded from the difference between surface concentrations of Zr and Si measured with XPS and the mean bulk concentrations, the ZrO[sub 2] precipitates somewhat more quickly than SiO[sub 2]. The acid strength of the SiO[sub 2]-ZrO[sub 2] mixed oxides corresponds to an H[sub 0] value between -11.4 and 13.8 (super-acidity). There is a fair correlation between the surface concentration of strong acid sites, determined from NH[sub 3] TPD, and the performance in the acid catalyzed dehydration of cyclohexanol to cyclohexene. In addition to the concentration of acid sites, their acid strength is an important factor determining the performance of the SiO[sub 2]-ZrO[sub 2] catalysts in the dehydration of cyclohexanol. The acid strength needed for the dehydration of cyclohexanol corresponds to H[sub 0] [<=] +2.8. Chemically mixed SiO[sub 2]-ZrO[sub 2] oxides contain strong acid sites as opposed to the single oxides SiO[sub 2] and ZrO[sub 2], which contain only weak acid sites. XPS shows an oxygen depletion on the surface of the mixed oxides, which indicates that the strong acid sites are of the Lewis type. 27 refs., 11 figs., 4 tabs.

• OSTI ID: 6879586
• Journal Information: Journal of Catalysis; (United States), Journal Name: Journal of Catalysis; (United States) Vol. 148:2; ISSN 0021-9517; ISSN JCTLA5
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical &amp; Physicochemical Properties
ABSORPTION SPECTROSCOPY
ALCOHOLS
AMMONIA
CATALYTIC EFFECTS
CHALCOGENIDES
CHEMICAL PREPARATION
COHERENT SCATTERING
CYCLOHEXANOL
DEHYDRATION
DESORPTION
DIFFRACTION
ELECTRON SPECTROSCOPY
HYDRIDES
HYDROGEN COMPOUNDS
HYDROXY COMPOUNDS
INORGANIC ACIDS
LEWIS ACIDS
NITROGEN COMPOUNDS
NITROGEN HYDRIDES
ORGANIC COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
PHOTOELECTRON SPECTROSCOPY
SCATTERING
SILICON COMPOUNDS
SILICON OXIDES
SORPTION
SPECTROSCOPY
SYNTHESIS
TEMPERATURE DEPENDENCE
TRANSITION ELEMENT COMPOUNDS
X-RAY DIFFRACTION
X-RAY SPECTROSCOPY
ZIRCONIUM COMPOUNDS
ZIRCONIUM OXIDES