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Titolo:
THERMOCHEMICAL ADSORPTIVE AND CATALYTIC EVENTS OCCURRING DURING ISOPROPANOL DECOMPOSITION OVER MNOX-MODIFIED ALUMINAS - IN-SITU INFRARED SPECTROSCOPIC STUDIES
Autore:
ZAKI MI; HUSSEIN GAM; NOHMAN AKH; NASHED YE;
Indirizzi:
KUWAIT UNIV,FAC SCI,DEPT CHEM,POB 5969 SAFAT 13060 KUWAIT MENIA UNIV,FAC SCI,DEPT CHEM MENIA 61519 EGYPT
Titolo Testata:
Thermochimica acta
, volume: 273, anno: 1996,
pagine: 257 - 268
SICI:
0040-6031(1996)273:<257:TAACEO>2.0.ZU;2-Z
Fonte:
ISI
Lingua:
ENG
Soggetto:
METAL-OXIDE SURFACES; MANGANESE OXIDES; THERMAL GENESIS; CARBON-MONOXIDE; ALCOHOLS;
Keywords:
ALUMINA CATALYSTS; INFRARED SPECTROSCOPY; ISOPROPANOL CATALYTIC DECOMPOSITION; MANGANESE OXIDE-MODIFIED ALUMINA CATALYSTS;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Citazioni:
31
Recensione:
Indirizzi per estratti:
Citazione:
M.I. Zaki et al., "THERMOCHEMICAL ADSORPTIVE AND CATALYTIC EVENTS OCCURRING DURING ISOPROPANOL DECOMPOSITION OVER MNOX-MODIFIED ALUMINAS - IN-SITU INFRARED SPECTROSCOPIC STUDIES", Thermochimica acta, 273, 1996, pp. 257-268

Abstract

Adsorptive and catalytic events occurring at gas/solid interfaces established during isopropanol decomposition over pure and MnOx-modified aluminas were monitored and characterized by in situ infrared spectroscopic measurements. On pure alumina the alcohol adsorbs dissociativelyand non-dissociatively at room temperature, giving rise respectively to isopropoxides coordinated to Lewis acid sites and isopropanol molecules hydrogen-bonded to hydroxyl (and oxide) sites. Those adsorbed species withstand outgassing at room temperature, but are completely eliminated near 200 degrees C. Meanwhile, the alcohol catalytic dehydration is commenced at 150 degrees C and gas-phase propene is thus released. Quantitative conversion into the alkene is effected near 225 degreesC. The modification with MnOx stabilizes the isopropoxide species to thermo evacuation at well above 200 degrees C, but activates their conversion into surface carboxylates at > 300 degrees C. Moreover, the isopropanol dehydration selectivity of alumina is critically suppressed and acetone becomes the dominant gas-phase product. Thus, a strong dehydrogenation selectivity is generated. These and other MnOx-influencedalterations to the adsorptive and catalytic behaviours of alumina arediscussed on the basis of available characterization results for the catalysts and mechanistic aspects established in the field.

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Documento generato il 13/07/20 alle ore 16:49:50