【摘要】 应用Faraday式磁天平,辅以XRD和活性测试,研究了Fe-Mo/Al₂O₃加氢脱硫催化剂基体的磁学性质、物相、和活性之间的关系。发现样品中的Fe/Mo原子比对催化剂的物相有重要影响。当Fe/Mo值为0.36—0.86时,主要物相为Fe₂（MoO₄）₃,其Weiss常数为负值（θ=-53K）,说明子晶格之间存在着反铁磁相互作用。当Fe/Mo值为1.5—3.1时,样品显示超顺磁性,这是由于过量的Fe在共沉淀时生成单独的物相α-FeOOH,并以极微细的颗粒存在,由于它的高度分散,致使样品中的Fe₂（MoO₄）₃也随之分散。自低磁场下的Langevin函数求得超顺磁性颗粒的大小约为110埃。样品的比表面随Fe/Mo值的增大而增加;对噻吩加氢脱硫的表观催化活性则在Fe/Mo=1.5左右时出现最大值。更多还原

【Abstract】 The precursors of the industrial Fe-Mo/Al2O3 hydrodesulfurization (HDS) catalyst, i. e. the precipitates prepared from ferrous sulfate and ammonium molybdate by the coprecipitation method without supported on alumina were characterized by the magnetic measurement and identified by XRD method. The catalytic activity of the samples for the HDS of thiophene at 380C was measured in a continuous flow type micro-reactor. The results are as follows:(1) The phase component of the precursor is dependent on its atomic ratio of Fe/Mo. When Fe/Mo<1.5,Fe2(MoO4)3 is the principal component, with a negative Weiss constant, -53K, which implies there occurred antiferroparamagnetic interaction between neighbouring Fe3+. When Fe/Mo= 1.5 -3.1, the samples reveal superparamagnetism for which the highly dispersed antiferromagnetic component a-FeOOH is responsible. Owing to the high dispersivity of a-FeOOH as formed in the coprecipitation process, the component Fe2(MoO4)3 formed in the same process is accordingly also highly dispersed. The average particle size evaluated by Langevin function and the low field magnetization versus H/T plots for the superparamagnetic component is about 110A-(2) As a consequence of the difference in phase components and their different dispersivity, the catalytic activity for HDS of thiophene is found to be affected by both of the surface area and Mo content of the samples. When Fe/Mo=1.5, there appears a maximum activity which is explained as the mutual effects of the surface area and the Mo content of the samples.(3) The effects of aging and calcination on the activity of the samples are also examined. Under optimum conditions, the coprecipitation process may result in a highly dispersed Fe-Mo precursor available to the Fe-Mo/Al2O3 catalyst.更多还原