Coprecipitated iron-containing catalysts (Fe-Al2O3, Fe-Co-Al2O3, Fe-Ni-Al2O3) for methane decomposition at moderate temperatures I.: Genesis of calcined and reduced catalysts

Genesis of the composition and structure of the active component of coprecipitated iron containing catalysts (Fe-Al2O3, Fe-Co-Al2O3, Fe-Ni-Al2O3) with high metal loadings (>50 wt.%) for methane decomposition at moderate temperatures (600-650degreesC) has been investigated by XRD, EXAFS. radial electron density distribution (REDD), TEM, FTIR and Mossbauer spectroscopy. The main stages of the catalyst genesis during drying, thermal decomposition and reduction have been studied. For bimetallic systems (Fe-Co-Al2O3, Fe-Ni-Al2O3) intermediate spinel phases with a composition (M-II,M- Fe)(3)O-4 (M = Co, Ni) have been shown to form during heat treatment and reduction. This leads to a decrease of the reduction temperature for iron oxides. Reduced bimetallic catalysts (Fe-Co-Al2O3, Fe-Ni-Al2O3) are composed of alloys. The structure and parameters of their crystal lattices depend on the type and concentration of the added metal. Alumina has been shown to behave as a Structural promoter. A model of the reduced catalysts consisting of highly dispersed (20-50 nm) metal and alumina particles with a spinel phase at their interface has been suggested. (C) 2004 Elsevier B.V. All rights reserved.