Synthesis and surface acid/base properties of magnesium-aluminum mixed oxides obtained from hydrotalcites

Journal Article · Sat Oct 01 00:00:00 EDT 1994 · Langmuir; (United States)

DOI:https://doi.org/10.1021/la00022a082· OSTI ID:7073321

Shen, Jianyi ^[1]; Kobe, J M; Dumesic, J A ^[2]; Chen, Yi ^[3]

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1. Univ. of Wisconsin, Madison, WI (United States) Nanjing Univ. (China)
2. Univ. of Wisconsin, Madison, WI (United States)
3. Nanjing Univ. (China)

Magnesium-aluminum hydrotalcite compounds have been synthesized without possible contamination by alkali cations. Pure hydrotalcite compounds with Mg/Al ratios from 3 to 12 were synthesized without the formation of separate phases. These materials were converted into magnesium-aluminum mixed oxides upon calcination at 773 K, showing the X-ray diffraction pattern of MgO. Microcalorimetric and infrared spectroscopic measurements of NH[sub 3] and CO[sub 2] adsorption were used to characterize the number, strength, and nature of acid/base sites on the surface of the calcined hydrotalcites. These materials do not possess acid sites and base sites with differential heats higher than 120 kJ/mol, respectively. In contrast, [gamma]-Al[sub 2]O[sub 3] possesses acid sites with differential heats from about 60 to kJ/mol, and MgO has base sites with differential heats as high as 170 kJ/mol. Infrared spectroscopy revealed that the acid sites on calcined hydrotalcites are mainly Lewis acids sites, while the base sites are oxygen anions. Calcination of hydrotalcites can be used to prepare Mg-Al-O mixed oxides with high surface are and moderate acidity and basicity. 35 refs., 11 figs., 2 tabs.

• OSTI ID: 7073321
• Journal Information: Langmuir; (United States), Vol. 10:10; ISSN 0743-7463
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
ALUMINIUM OXIDES
SURFACE PROPERTIES
SYNTHESIS
X-RAY DIFFRACTION
AMMONIA
ADSORPTION
CARBON DIOXIDE
MAGNESIUM OXIDES
CALCINATION
CALORIMETRY
COMPILED DATA
INFRARED SPECTRA
NUCLEAR MAGNETIC RESONANCE
ALKALINE EARTH METAL COMPOUNDS
ALUMINIUM COMPOUNDS
CARBON COMPOUNDS
CARBON OXIDES
CHALCOGENIDES
CHEMICAL REACTIONS
COHERENT SCATTERING
DATA
DECOMPOSITION
DIFFRACTION
HYDRIDES
HYDROGEN COMPOUNDS
INFORMATION
MAGNESIUM COMPOUNDS
MAGNETIC RESONANCE
NITROGEN COMPOUNDS
NITROGEN HYDRIDES
NUMERICAL DATA
OXIDES
OXYGEN COMPOUNDS
PYROLYSIS
RESONANCE
SCATTERING
SORPTION
SPECTRA
THERMOCHEMICAL PROCESSES
360201* - Ceramics
Cermets
& Refractories- Preparation & Fabrication
360204 - Ceramics
Cermets
& Refractories- Physical Properties
400102 - Chemical & Spectral Procedures