ISSN:
1572-879X
Schlagwort(e):
Carbon supported Fe
;
Fe-Mn
;
K-Fe-Mn catalysts
;
mixed metal carboxyl clusters
;
chemisorption
;
kinetic measurements
;
calorimetric measurements
;
infrared spectroscopy
;
Mössbauer spectroscopy
Quelle:
Springer Online Journal Archives 1860-2000
Thema:
Chemie und Pharmazie
Notizen:
Abstract Carbon-supported Fe, Fe-Mn, and K-Fe-Mn catalysts derived from stoichiometric mixed-metal carbonyl clusters were pretreated at either 473 K or 673 K in hydrogen. Chemisorption and kinetic measurements were conducted following these pretreatments. The iron remained highly dispersed at all times except after high temperature reductions when potassium was present. The single promotion by either Mn or K increases the olefin/paraffin ratio, while the doubly promoted catalyst gave very high selectivities for light olefins. Isothermal, integral heats of adsorption of CO were determined at 300 K, and they increased from 15 kcal/mole for Fe3/C to nearly 17 kcal/mole for both the singly promoted Fe2Mn/C and KFe3/C catalysts to 21 kcal/mole for the doubly promoted KFe2Mn/C sample. A model of the decomposition of these carbonyl clusters is proposed based on calorimetric, Mössbauer effect spectroscopic and diffuse reflectance Fourier transform infrared spectroscopic studies. The state of the MnOx and K phases on the iron surface, as well as the Fe crystallite size, appears to play a dominant role in determining the catalytic behavior.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1007/BF00764505
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