Fe3O4改性的Ru/γ-Al2O3催化剂的原位液相加氢性能

采用分步浸渍法制备负载型Ru-Fe₃O₄/γ-Al₂O₃ 催化剂, 并利用透射电子显微镜(TEM)、X 射线衍射(XRD)、N₂吸附-脱附(BET)、傅里叶变换红外(FTIR)光谱与X射线光电子能谱(XPS)表征催化剂的纳米颗粒粒径分布、晶相组成、表面结构及吸附物种等性质. 将Ru-Fe₃O₄/γ-Al₂O₃催化剂用于3,4-二氯硝基苯选择性原位液相加氢反应, 考察了反应条件对催化活性的影响, 并讨论了不同制备条件下催化剂的稳定性能. 结果表明, 在473 K、液压3 MPa、原料质量分数2%, 乙醇/水体积比75:25 的反应条件下, 3,4-二氯硝基苯的转化率为100%, 3,4-二氯苯胺的选择性高达96.4%. Fe₃O₄含量对催化剂稳定性能有显著影响, 当Ru和Fe 的质量分数分别为2%和6%时, 催化剂可稳定200 h以上. 表面吸附CO与积碳是导致催化剂失活的主要原因, 以Fe₃O₄作为高效的助剂, 进行水汽转换(WGS)反应与费托合成(FTS)可移除CO, 而采用煅烧法去除表面积碳. 晶相变化与纳米颗粒的聚集可能导致催化剂部分失活, 其原因以及再生方法需进一步考察.

Fe3O4 Modified Alumina Supported Ruthenium Catalyst for Novel In-situ Liquid Phase Catalytic Hydrogenation

Ru-Fe₃O₄/γ-Al₂O₃ was synthesized by stepwise impregnation method and applied to the in-situ liquid phase selective hydrogenation of 3,4-dichloronitrobenzene (3,4-DCNB). The nanoparticle size and distribution, metallic crystalline constitution, surface structure parameters, and adsorption species were systematically characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, N₂ adsorption-desorption (BET), and X-ray photoelectron spectroscopy (XPS). The Ru-Fe₃O₄/γ-Al₂O₃ catalyst was investigated using the in-situ liquid phase hydrogenation of 3,4-DCNB as probe reaction, the effect of different reaction conditions and different synthetic factors on the catalytic properties was studied. Experimental results showed that the catalytic properties of the Ru-Fe₃O₄/γ-Al₂O₃ catalyst were significantly influenced by its Fe₃O₄ content, under the optimum condition of 473 K, 3.0 MPa, 2% (w) 3,4-DCNB concentration with 75% ethanol and 25% water, the Ru-Fe₃O₄/γ-Al₂O₃ catalyst with Ru and Fe mass fractions of 2% and 6% exhibited the highest activity and stability, with 100% conversion of 3,4-DCNB, 96.4% selectivity of 3,4-dichloroaniline (3,4-DCAN), and this catalyst could be stabilized for more than 200 h. The main reason for the deactivation of the catalyst is CO coverage on active centers, and the poisoning-deactivated catalysts were regenerated by water-gasshift (WGS) reaction and Fischer-Tropsch synthesis (FTS), which employ Fe₃O₄ modified Ru/Al₂O₃ as catalyst due to its high efficiency of CO transformation. Carbon deposition on the catalyst surface is the reason second only to carbon monoxide poisoning, and this could be removed through calcination. Crystalline phase change and nanoparticles aggregation may cause partial deactivation, and investigation of the mechanism and catalyst regeneration are in progress.