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Titolo:
MICROCALORIMETRIC STUDIES OF SURFACE ACID BASE PROPERTIES OF MAGNESIUM-IRON CATALYSTS PREPARED FROM HYDROTALCITE-TYPE PRECURSORS/
Autore:
TU M; SHEN JY; CHEN Y;
Indirizzi:
NANJING UNIV,DEPT CHEM NANJING 210093 PEOPLES R CHINA NANJING UNIV,DEPT CHEM NANJING 210093 PEOPLES R CHINA
Titolo Testata:
Journal of solid state chemistry
fascicolo: 1, volume: 128, anno: 1997,
pagine: 73 - 79
SICI:
0022-4596(1997)128:1<73:MSOSAB>2.0.ZU;2-2
Fonte:
ISI
Lingua:
ENG
Soggetto:
METAL-OXIDE SURFACES; THERMAL-DECOMPOSITION; MIXED OXIDES; BASE PROPERTIES; ADSORPTION;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Science Citation Index Expanded
Citazioni:
29
Recensione:
Indirizzi per estratti:
Citazione:
M. Tu et al., "MICROCALORIMETRIC STUDIES OF SURFACE ACID BASE PROPERTIES OF MAGNESIUM-IRON CATALYSTS PREPARED FROM HYDROTALCITE-TYPE PRECURSORS/", Journal of solid state chemistry, 128(1), 1997, pp. 73-79

Abstract

Magnesium-iron mixed oxides with Mg/Fe molar ratios 1, 3, and 6 were prepared from hydrotalcite-type precursors. Microcalorimetric adsorption of NH3 and CO2 showed that the surface acidity and basicity of the mixed oxides after calcination at 673K are similar despite the different Mg/Fe ratios. Increasing calcination temperature from 673 to 773K significantly decreased the surface area of the 3 Mg/Fe oxide, but the densities of both the acid and base sites were not changed. Mossbauer spectroscopy revealed that the reduction of the 3 Mg/Fe oxide (Fe2O3/MgO) in H-2 at 673K converted all Fe3+ to Fe2+. The resulted FeO/MgO exhibited the same acidity as that of the Fe2O3/MgO, but the basicity ofthe FeO/MgO was greatly enhanced. Reduction at 773K resulted in the formation of 76% Fe2+ and 24% Fe-0 as detected by Mossbauer spectroscopy. The Fe/FeO/MgO sample formed exhibited very low heat for the adsorption of NH3 (40 kJ/mol) indicating that all iron atoms on the surface are Fe-0. However, a substantial basicity remained on the surface of this sample that may account for its high olefin selectivity compared with pure iron catalyst in the Fischer-Tropsch synthesis. (C) 1997 Academic Press.

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Documento generato il 05/07/20 alle ore 08:45:25