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

Journal Article · Sat Oct 01 04:00:00 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), Journal Name: Langmuir; (United States) Vol. 10:10; ISSN LANGD5; ISSN 0743-7463
• Country of Publication: United States
• Language: English

Related Subjects

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