PROPERTIES AND CATALYTIC BEHAVIOR FOR THE FISCHER-TROPSCH SYNTHESIS OF AMORPHOUS IRON-BASED ALLOYS PREPARED BY SPARK-EROSION

Fully amorphous Fe80B20 and partially amorphous iron catalysts were produced in powder form by the spark-erosion method using kerosene as the dielectric. Large amounts of carbon as well as perceptible levels of hydrogen were incorporated in the powders' structure during production. When the catalysts were heated in an inert atmosphere, the hydrogen present in the powders desorbed as pure hydrogen and also combined with carbon, as hydrocarbons of low-molecular weight. Removal of carbon by sedimentation resulted in a large decrease in surface area, from 102 m2/g to 2 m2/g for Fe80B20 powder. The use of the iron-based powders as catalysts for Fischer-Tropsch synthesis was also studied. At 280-degrees-C and 1 bar, the main reaction products were methane and low-molecular-weight hydrocarbons, mainly alkenes. Selectivities to alkenes reached values as high as 90 mol-% for amorphous Fe80B20 powder. Product distributions were found to follow the Schulz-Flory model, over the temperature range 260-340-degrees-C, for all the catalysts studied.