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), Vol. 109:2
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
01 COAL, LIGNITE, AND PEAT
COPPER OXIDES
CRYSTAL STRUCTURE
ZINC OXIDES
CARBON MONOXIDE
CATALYSTS
CHEMICAL PREPARATION
CHEMICAL REACTIONS
COPPER CARBONATES
DIFFERENTIAL THERMAL ANALYSIS
MAGNETIC SUSCEPTIBILITY
METHANOL
SPECTROSCOPY
SYNTHESIS
THERMAL GRAVIMETRIC ANALYSIS
X-RAY DIFFRACTION
ZINC CARBONATES
ALCOHOLS
CARBON COMPOUNDS
CARBON OXIDES
CARBONATES
CHALCOGENIDES
CHEMICAL ANALYSIS
COHERENT SCATTERING
COPPER COMPOUNDS
DIFFRACTION
GRAVIMETRIC ANALYSIS
HYDROXY COMPOUNDS
MAGNETIC PROPERTIES
ORGANIC COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
QUANTITATIVE CHEMICAL ANALYSIS
SCATTERING
THERMAL ANALYSIS
TRANSITION ELEMENT COMPOUNDS
ZINC COMPOUNDS
400201* - Chemical & Physicochemical Properties
010408 - Coal
Lignite
& Peat- C1 Processes- (1987-)