Synthesis of Al – Fe/SiO2 and Al – Co/SiO2 catalysts by solid-phase method

Abstract

Powders of catalysts from aluminides Fe and Co on a SiO2 support (33.3 wt. %) were obtained by mechano-thermal synthesis. The formation of large powder fractions (> 100 μm) was experimentally established. The fractions of these fractions for Fe – Al – SiO2 and Co – Al – SiO2 respectively amounted to ~ 43 % and ~ 55 %, which is a positive result for further catalytic studies. After annealing the powders at 700 and 900 °C in vacuum, the SiO2 support and compounds: Co27Al73 (close in composition to CoAl3, Co4Al13 type intermetallic compounds), Fe3Al intermetallic compound with iron silicide type Fe0.9Si0.1 and compound Al0,3Fe3Si0.7 in small volumes. On the synthesis of cobalt aluminides, a conclusion has been made about more efficient annealing at 900 °C than at 700 °C. For Fe – Al – SiO2 powders, it is advisable to anneal in the temperature range 700 – 750 °C with the assumption that the SiO2 support influences the thermosynthesis of iron aluminides. An experimental analysis of the morphology and elemental composition of the surface of the obtained samples is presented. It was found that the catalyst powders have medium sphericity and angularity. Fe – Al – SiO2 powders have a more developed surface than Co – Al – SiO2. Lower intermetallics are predominantly formed on the surface of the Co – Al – SiO2 sample. The correction of the mechanical alloying modes by means of the fragmentation of the process, changes in the intensity of its parameters, and various annealing conditions for Co – Al – SiO2 and Fe – Al – SiO2 are proposed.