Cr助剂对Fe基催化剂结构和费托合成性能的影响

Effects of Cr Promoter on Structure and Fischer-Tropsch Synthesis Performance over Fe-Based Catalysts

采用N2吸附-脱附、X射线衍射、穆斯堡尔谱、X射线光电子能谱、程序升温还原和热重分析等技术研究了助剂Cr含量对Fe基费托合成催化剂的织构性质、还原行为以及物相变化的影响.在H2/CO=2.0,260-300℃,1.5MPa和2000ml/（g·h）条件下,在固定床反应器中考察了Cr含量对Fe基催化剂费托合成反应活性和产物烃选择性的影响.结果表明,在氧化态催化剂中,Cr助剂与Fe物相存在较强的相互作用,形成固溶体相α-（Cr1-xFex）2O3;随着Cr含量的增加,逐渐由单一的富Fe相α-（Fe1-xCrx）2O3向富Fe相和富Cr相α-（Cr1-yFey）2O3两相过渡.Fe-Cr固溶体的生成显著抑制了催化剂的还原,导致催化剂还原度降低,因而催化剂活性下降.同时,Cr的添加提高了甲烷和轻质烃选择性,但抑制了水煤气变换活性.

The effects of promoter Cr content in the Fe-based Fischer-Tropsch synthesis（FTS） catalysts on the textural properties,reduction behavior,and phase transformation of the catalysts during reduction and reaction were investigated by N2 adsorption,X-ray diffraction,Mssbauer spectroscopy,X-ray photoelectron spectroscopy,H2 differential thermogravimetric analysis,and CO temperature-programmed reduction over the coprecipitated Fe-based catalysts.The FTS performance of the Fe-based catalysts promoted with Cr was studied in a fixed-bed reactor under the conditions of H2/CO = 2.0,260-300 oC,1.5 MPa,and 2 000 ml/（g·h）.The results showed that the strong interaction existed between Fe and Cr species by the formation of Fe-Cr solid solution,α-（Fe1-xCrx）2O3.With the increase of promoter Cr content in the Fe-based catalysts,the phases of the catalysts gradually transformed to the Fe-rich phase and Cr-rich phase.Because the Fe-Cr solid solution strongly inhibited the reduction of the catalyst,Cr-promoted Fe-based catalysts exhibited low activity due to its lower extents of both reducibility and carburization.The promoter Cr enhanced the formation of methane and light hydrocarbon products but inhibited the activity of water-gas-shift reaction.