Structural characterization of malachite-like coprecipitated precursors of binary CuO-ZnO catalysts
Copper and zinc hydroxycarbonates with Cu/Zn atomic ratios of 100/0, 92/8, 85/15, 77/23, 67/33, and 50/50 were prepared by the coprecipitation method. The samples with the ratios 100/0, 92/8 and 85/15 were monophasic with the monoclinic P2/sub 1//a malachite structure, whereas the richer zinc samples contained in addition to the malachite phase the orthorhombic B22/sub 1/2 aurichalcite, whose concentration was very low in the 77/23 specimen but increased continuously with zinc content. The amount of aurichalcite in the biphasic powders has been estimated by means of quantitative X-ray diffraction and differential thermal analysis. With only those X-ray reflections belonging to the malachite structure taken into account, the unit cell constants for all the solid solution hydroxycarbonates have been determined, showing that as a whole the cell volume of malachite decreases continuously with increasing zinc content. This result is related, as shown also by DTA measurements and thermochemical literature data, to an increasing stability of compounds richer in zinc, to increasing covalent effects, and/or to less octahedral site distortion around the metal atoms when zinc substitutes for Cu/sup 2 +/ ions in the malachite lattice. Magnetic susceptibility and thermogravimetric measurements together with diffuse reflectance spectra are also presented and discussed.
- Research Organization:
- Universita di Roma La Sapienza (Italy)
- OSTI ID:
- 5354044
- Journal Information:
- J. Catal.; (United States), Journal Name: J. Catal.; (United States) Vol. 109:2; ISSN JCTLA
- Country of Publication:
- United States
- Language:
- English
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37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
ALCOHOLS
CARBON COMPOUNDS
CARBON MONOXIDE
CARBON OXIDES
CARBONATES
CATALYSTS
CHALCOGENIDES
CHEMICAL ANALYSIS
CHEMICAL PREPARATION
CHEMICAL REACTIONS
COHERENT SCATTERING
COPPER CARBONATES
COPPER COMPOUNDS
COPPER OXIDES
CRYSTAL STRUCTURE
DIFFERENTIAL THERMAL ANALYSIS
DIFFRACTION
GRAVIMETRIC ANALYSIS
HYDROXY COMPOUNDS
MAGNETIC PROPERTIES
MAGNETIC SUSCEPTIBILITY
METHANOL
ORGANIC COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
QUANTITATIVE CHEMICAL ANALYSIS
SCATTERING
SPECTROSCOPY
SYNTHESIS
THERMAL ANALYSIS
THERMAL GRAVIMETRIC ANALYSIS
TRANSITION ELEMENT COMPOUNDS
X-RAY DIFFRACTION
ZINC CARBONATES
ZINC COMPOUNDS
ZINC OXIDES