TY - JOUR
T1 - Mössbauer investigation of supported Fe and FeNi catalysts. I. Effect of pretreatment on particle size
AU - Raupp, G. B.
AU - Delgass, W. N.
N1 - Funding Information:
We gratefully acknowledge by NSF (Grant ENG76-20853) Materials Research Program 00889Al), and thank E. M. Bild to the understanding of supported
Funding Information:
of this work and the NSF (Grant DMR76- for contributions FeNi.
PY - 1979/7
Y1 - 1979/7
N2 - Silica-supported Fe and FeNi catalysts show strong dependence of metal particle size on pretreatment, particularly the initial dehydration step. Room temperature Mössbauer spectra and supporting X-ray diffraction data reveal that mild pretreatment in the form of slow vacuum drying prior to reduction produces significantly smaller particles of Fe and FeNi on silica than either direct reduction or calcining. Once the catalyst precursor is completely dried, metal particles are relatively stable against further growth, suggesting that residual water or anions from the incipient wetness impregnation play a critical role in metal agglomeration during pretreatment. For 5 wt% Fe 5 wt% Ni on silica, vacuum drying and subsequent reduction produce FeNi alloy particles small enough to exhibit superparamagnetic behavior. Precalcining this catalyst increases the alloy particle size considerably as shown by a ferromagnetically split Mössbauer spectrum. Computer fitting of the broad peaks reveals significant amounts of metallic iron or extremely iron-rich alloy and, therefore, that phase separation can accompany particle growth in FeNi alloy catalysts.
AB - Silica-supported Fe and FeNi catalysts show strong dependence of metal particle size on pretreatment, particularly the initial dehydration step. Room temperature Mössbauer spectra and supporting X-ray diffraction data reveal that mild pretreatment in the form of slow vacuum drying prior to reduction produces significantly smaller particles of Fe and FeNi on silica than either direct reduction or calcining. Once the catalyst precursor is completely dried, metal particles are relatively stable against further growth, suggesting that residual water or anions from the incipient wetness impregnation play a critical role in metal agglomeration during pretreatment. For 5 wt% Fe 5 wt% Ni on silica, vacuum drying and subsequent reduction produce FeNi alloy particles small enough to exhibit superparamagnetic behavior. Precalcining this catalyst increases the alloy particle size considerably as shown by a ferromagnetically split Mössbauer spectrum. Computer fitting of the broad peaks reveals significant amounts of metallic iron or extremely iron-rich alloy and, therefore, that phase separation can accompany particle growth in FeNi alloy catalysts.
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U2 - 10.1016/0021-9517(79)90273-2
DO - 10.1016/0021-9517(79)90273-2
M3 - Article
AN - SCOPUS:0000258577
SN - 0021-9517
VL - 58
SP - 337
EP - 347
JO - Journal of Catalysis
JF - Journal of Catalysis
IS - 3
ER -