Moessbauer investigation of supported Fe and FeNi Fischer-Tropsch catalysts--1. Effect of pretreatment on particle size
Catalysts containing 10Vertical Bar3< iron or 5Vertical Bar3< iron/5Vertical Bar3< nickel on high-surface area silica were prepared from the nitrates by the incipient wetness impregnation technique, air-dried at room temperature for three weeks, and either vacuum-dried to 413/sup 0/K or calcined in 1Vertical Bar3< oxygen in helium or in a flow of oxygen to 723/sup 0/K. The Moessbauer spectra of these catalysts were studied before and after reduction with hydrogen, and the results compared with X-ray diffraction measurements of particle size. Vacuum drying prior to reduction produced smaller metal particles with both catalysts than either direct reduction or calcining prior to reduction; apparently removal of water prior to nitrate decomposition helps anchor the metal ions to the support and prevents massive precipitation of salt particles in the pores. The particle sizes increased with increasing pretreatment severity, but the small particles formed on evacuated catalysts were relatively stable against further growth. The reducibility increased with increasing particle size. The vacuum-dried Fe/Ni catalyst formed an equimolar alloy, but phase separation occurred in the larger particles.
- Research Organization:
- Purdue Univ.
- OSTI ID:
- 7062073
- Journal Information:
- J. Catal.; (United States), Vol. 58:3
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
CATALYSTS
CHEMICAL PREPARATION
FISCHER-TROPSCH SYNTHESIS
IRON NITRATES
MOESSBAUER EFFECT
NICKEL NITRATES
PARTICLE SIZE
PHASE TRANSFORMATIONS
STRUCTURAL CHEMICAL ANALYSIS
CHEMICAL REACTIONS
IRON COMPOUNDS
NICKEL COMPOUNDS
NITRATES
NITROGEN COMPOUNDS
OXYGEN COMPOUNDS
SIZE
SYNTHESIS
TRANSITION ELEMENT COMPOUNDS
400201* - Chemical & Physicochemical Properties