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应用Faraday式磁天平,辅以XRD和活性测试,研究了Fe-Mo/Al_2O_3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Fe_2(MoO_4)_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Fe_2(MoO_4)_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。
The relationship between magnetic properties, phase, and activity of Fe-Mo / Al_2O_3 hydrodesulfurization catalyst matrix was studied by Faraday-type magnetic balance and XRD and activity testing. It is found that the Fe / Mo atomic ratio in the sample has an important influence on the phase of the catalyst. When the Fe / Mo value is 0.36-0.86, the main phase is Fe_2 (MoO_4) _3, and the Weiss constant is negative (θ = -53K), indicating that there exists an antiferromagnetic interaction between the sublattices. When the Fe / Mo value is 1.5-3.1, the sample shows superparamagnetism because excess Fe forms a separate phase, α-FeOOH, during coprecipitation and exists in very fine particles due to its high degree of dispersion, As a result, Fe 2 (MoO 4) 3 in the sample is also dispersed. The size of the superparamagnetic particles was about 110 Angstroms from the Langevin function at low magnetic field. The specific surface area of the sample increased with the increase of Fe / Mo value. The apparent catalytic activity for hydrodesulfurization of thiophene appeared at the maximum of Fe / Mo = 1.5.