Study On Precipitation Of Iron Fischer-tropsch Synthesis From Different Iron Precursors

Fischer-Tropsch synthesis?FTS?is the process of converting syngas?H₂+CO?produced from carbonaceous resources such as coal,natural gas and biomass into liquid fuels and high value-added products.Due to its low cost,high reactivity and water gas shift activity,and suitable for coal-based syngas with low hydrogen to carbon ratio.Therefore,Fischer-Tropsch synthesis iron-based catalysts are one of the most industrially valuable and hottest catalysts in the field of Fischer-Tropsch synthesis.Although iron-based catalysts are currently industrialized,research and development of Fischer-Tropsch synthesized iron-based catalysts with high stability,high activity,and high selectivity still face enormous challenges.Starting from the traditional Fe/Cu/K/SiO₂ iron-based catalysts,the effects of preparation methods,iron precursors,Cu promoter and reaction conditions on precipitated iron Fischer-Tropsch synthesis catalysts were systematically studied.The effect of preparation methods on the performance of iron catalysts was investigated,it was found that the catalyst prepared from cocurrent precipitation had a special rod-like structure and enriched the pore structure of the catalyst.Moreover,the catalyst prepared from cocurrent precipitation had good dispersibility,crystallinity and reducibility,therefore,it had the best activity and stability in the Fischer-Tropsch synthesis reaction.and exhibited higher low-carbon olefin selectivity and hydrocarbon product yield,and the highest content of gasoline components in the liquid phase product.By studying the effect of iron precursors on precipitated iron catalyst,it was found that the catalyst prepared from FeC₂O₄ had higher specific surface area,the lowest reduction temperature,the highest crystallinity and the highest CO conversion.Moreover,the catalyst prepared from FeC₂O₄ had the best hydrocarbon product yield,and the highest content of gasoline components in the liquid phase products.The catalyst prepared from Fe?NO₃?₃ exhibited higher low carbon olefin selectivity.The effect of reaction temperature and reaction space velocity on the performance of precipitated iron catalyst was explored,it was found that increasing the reaction temperature is beneficial to increase the activity and product selectivity of the catalyst,and increasing the reaction space velocity can contribute to the formation of low-carbon hydrocarbons.Cu promoter had different effects in different iron-based catalysts.In the catalysts prepared from Fe?NO₃?₃,when Fe/Cu=100/5.7,the catalyst possessed the best catalytic activity,and the change in the amount of Cu promoter had little effect on the selectivity of the products.When Fe/Cu=100/5,the catalyst prepared from FeSO₄ exhibited the highest activity and stability,and with the increase of Cu promoter content,the selectivity of CH₄ and C₂=^C₄=increased,and the selectivity of C₅₊showed a downward trend.The selectivity of CH₄ was at least 1.00%,and the selectivity of C₅₊was up to 82.29%.In the catalysts prepared from FeC₂O₄,the catalyst exhibited the highest activity and stability when Fe/Cu=100/4.With the increase of Cu promoter content,the selectivity of CH₄ increased and the selectivity of C₅₊decreased first and then increased,the Cu promoter had no effect on the selectivity of C₂=^C₄=.