Fe3O4@PI催化剂的制备及其费托合成性能

分别采用水热、水热-包覆、球磨法制备了Fe_3O_4、聚酰亚胺(PI)改性的Fe_3O_4@PI和Fe_3O_4-PI催化剂用于费托合成反应,对比研究了PI改性及其含量变化对Fe基催化剂催化CO加氢产物分布的影响规律。结合XRD、SEM、TEM、H_2-TPR、COTPD、FT-IR、XPS、TG和接触角实验等手段对催化剂样品进行了表征。结果表明,Fe_3O_4、Fe_3O_4@PI和Fe_3O_4-PI样品均为球形颗粒; PI改性促进了Fe_3O_4的还原,亲水性增强。Fe_3O_4@PI样品中,PI均匀包覆于Fe_3O_4表面,具有较好的热稳定性;与Fe_3O_4、Fe_3O_4-PI相比,Fe_3O_4@PI样品CO吸附增强。在CO加氢反应中,与Fe_3O_4相比,PI改性的Fe_3O_4@PI和Fe_3O_4-PI样品催化活性下降,二次加氢能力受到抑制,烯烃选择性提高; Fe_3O_4@PI样品烯烃选择性增加明显,烯烷比(O/P)由改性前的0.50提高至2.15;适宜含量的PI改性促进C5+烃生成。

Preparation of Fe3O4@PI and its catalytic performances in Fischer-Tropsch synthesis

Polyimide (PI) modified Fe₃O₄@PI and Fe₃O₄-PI catalyst samples were prepared by hydrothermal-coating and ball milling methods, respectively. The effect of PI modification on the product distribution of the Fe-based catalysts for Fischer-Tropsch synthesis was investigated. The catalysts were characterized by XRD, SEM, TEM, H₂-TPR, CO-TPD, FT-IR, XPS, TG and contact angle measurements. The results showed that Fe₃O₄, Fe₃O₄@PI and Fe₃O₄-PI were spherical with uniform particle size, and the Fe₃O₄@PI particle size was smaller. PI modification promoted the reduction and the hydrophilicity of Fe₃O₄. For Fe₃O₄@PI sample, PI was uniformly coated on Fe₃O₄ surface, which led to good thermal stability. Compared with Fe₃O₄ and Fe₃O₄-PI samples, CO adsorption was promoted on Fe₃O₄@PI. Compared with Fe₃O₄, the catalytic activity of Fe₃O₄@PI and Fe₃O₄-PI decreased, and the secondary hydrogenation ability was inhibited, resulting in increase of olefin selectivity. For Fe₃O₄@PI, the olefin selectivity was enhanced significantly with olefin to alkane ratio in C_2-4 fraction increased from 0.50 to 2.15. PI modification with suitable content favored the formation of C₅₊ hydrocarbons.