| The perovskite family of metal oxides were investigated as catalysts for the Fischer-Tropsch (F-T) reactions. Ion substituted perovskites were prepared by the High Temperature Aerosol Decomposition (HTAD) process developed for this investigation. This technique involves spraying a metal salt solution into a heated tube furnace where the solvent evaporates, the salt precipitates and is decomposed to the oxide, generally in micron sized hollow spheres. This process provided a wide range of operating conditions and thus a wide range of materials properties for some compositions. Operating temperatures up to 1400{dollar}spcirc{dollar}C were attained. Materials synthesized by this technique were characterized by SEM, surface area and XRD analyses. The perovskite materials synthesized generally showed high surface areas and spherical morphology.; LacCoO{dollar}sb3{dollar} and LaFeO{dollar}sb3{dollar} based catalysts were shown to have a wide range of syngas conversions and selectivities. A differential reactor operated at 250{dollar}spcirc{dollar}C, 300 psig and 2/1 H{dollar}sb2{dollar}/CO with on-line gas chromatographic analysis was used to determine Fischer-Tropsch reactivities. The cobalt based catalysts were unstable while the iron based materials did not decompose under reaction conditions based on XRD data after F-T reaction of up to 80 hours. The ferrite perovskite system showed regular modification in polymerization probability, olefin to paraffin ratio and activity as a function of "A" site substitution for some composition regimes. The (La, Sr)FeO{dollar}sb3{dollar} system showed polymerization probabilities from 0.38 to 0.82, hydrocarbon production increase over 100 fold, and propylene to propane ratio from 2.3 to 4.8. Attempts were made to correlate reactivity changes to structure, composition, valence and oxygen defects. This work demonstrates the use of perovskite materials as optimizable catalysts. |
