Microcalorimetric and infrared spectroscopic studies of [gamma]-Al[sub 2]O[sub 3] modified by basic metal oxides

Journal Article · Thu Aug 18 00:00:00 EDT 1994 · Journal of Physical Chemistry; (United States)

DOI:https://doi.org/10.1021/j100084a025· OSTI ID:7015504

Shen, J ^[1]; Cortright, R D; Dumesic, J A ^[2]; Chen, Y ^[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)

Microcalorimetric and infrared spectroscopic studies of ammonia and carbon dioxide adsorption were used to study the surface acid/base properties of [gamma]-Al[sub 2]O[sub 3] following addition of K[sub 2]O, MgO, and La[sub 2]O[sub 3]. Microcalorimetric measurements of NH[sub 3] adsorption at 423 K showed that addition of basic metal oxide cations at loadings less than 200 [mu]mol/g converted the stronger acid sites (heats from 140-160 kJ/mol) to sites of intermediate strength (100-140 kJ/mol). Increasing the loadings of the basic oxides further eliminated the stronger acid sites and eliminated sites of intermediate strength. Infrared spectra of adsorbed NH[sub 3] showed that [gamma]-Al[sub 2]O[sub 3] contained both Bronsted and Lewis acid sites after calcination at 723 K, and addition of potassium removed Bronsted acid sites. The addition of basic metal oxides at loadings less than 500 [mu]mol/g increased the number of weak basic sites (heats from 60-100 kJ/mol) and sites of intermediate strength (100-140 kJ/mol). Strong basic sites (140-160 kJ/mol) were formed at higher loadings of basic oxides on alumina. The effectiveness of basic metal oxides to neutralize acid sites and to generate basic sites on alumina can be related to the electronegativities of these oxides. 41 refs., 14 figs., 1 tab.

• OSTI ID: 7015504
• Journal Information: Journal of Physical Chemistry; (United States), Journal Name: Journal of Physical Chemistry; (United States) Vol. 98:33; ISSN JPCHAX; ISSN 0022-3654
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400102 -- Chemical & Spectral Procedures
400201* -- Chemical & Physicochemical Properties
ADSORPTION
ALKALI METAL COMPOUNDS
ALKALINE EARTH METAL COMPOUNDS
ALUMINIUM COMPOUNDS
ALUMINIUM OXIDES
AMMONIA
CALORIMETRY
CARBON COMPOUNDS
CARBON DIOXIDE
CARBON OXIDES
CHALCOGENIDES
HYDRIDES
HYDROGEN COMPOUNDS
INFRARED SPECTRA
INORGANIC ACIDS
LANTHANUM COMPOUNDS
LANTHANUM OXIDES
LEWIS ACIDS
MAGNESIUM COMPOUNDS
MAGNESIUM OXIDES
NITROGEN COMPOUNDS
NITROGEN HYDRIDES
OXIDES
OXYGEN COMPOUNDS
POTASSIUM COMPOUNDS
POTASSIUM OXIDES
RARE EARTH COMPOUNDS
SORPTION
SPECTRA
SURFACE PROPERTIES