核-壳结构多酸/磁性铈铁纳米复合氧化物@SiO2吸附-氧化脱硫性能

水热法合成了铈铁纳米复合氧化物,采用化学沉积法在其表面包裹SiO₂制备核-壳结构磁性材料,以其为载体负载H₂O₂结合Keggin结构磷钼酸(HPMo)制备了HPMo-H₂O₂/CeFe_xO_y@SiO₂吸附-氧化脱硫催化剂。 采用扫描电子显微镜(SEM)、透射电子显微镜(TEM)、傅里叶红外光谱(FT-IR)、X射线粉末衍射(XRD)、氮气吸附脱附(BET)、³¹P魔角核磁共振(MAS-NMR)和X射线光电子能谱(XPS)等对催化剂的结构进行表征。 结果表明,SiO₂将CeFe_xO_y包裹形成核-壳结构纳米复合材料,以其为载体负载HPMo-H₂O₂后Keggin型多酸的骨架结构保持,并产生少量过氧化磷钼酸盐活性物种。 不同催化剂对有机硫化物二苯并噻吩(DBT)的吸附脱硫和氧化脱硫性能,均呈现出HPMo-H₂O₂/CeFe_xO_y@SiO₂＞CeFe_xO_y@SiO₂＞CeFe_xO_y的活性顺序,多酸的引入大大提升了其对大分子有机硫化物的吸附和氧化脱除性能,催化氧化脱硫活性的提高源于多酸分子“假液相”反应过程的结果。 在反应温度60 ℃,反应3 h,m(油)∶m(催化剂)=35∶1,n(O)∶n(S)=10∶1的条件下,对DBT氧化脱除率达到99.4%。 制备的磁性核-壳结构氧化脱硫剂有理想的氧化脱除DBT的循环使用性能,并且可通过外加磁场进行简单分离,是一类制备方法简单、催化活性高且稳定性好的绿色环保型催化剂。

Adsorption-Oxidative Desulfurization Performance of Core-Shell Polyoxometalate/Magnetic Cerium-Iron Nanocomposite Oxide@SiO2

The manganese-cerium mixed iron oxide nanocomposites were synthesized by hydrothermal synthesis method. The surface was wrapped by SiO₂ by chemical vapor deposition to prepare the core-shell magnetic material which was then loaded by H₂O₂ with Keggin structure phosphomolybdic acid (HPMo) to synthesize the HPMo-H₂O₂/CeFe_xO_y@SiO₂ adsorption-oxidative desulfurization catalyst. The catalyst was characterized by SEM, TEM, FT-IR, XRD, ³¹P MAS-NMR and XPS. The results of SEM, TEM and XPS characterization show that CeFe_xO_y is wrapped by SiO₂ to form core-shell nanocomposite material. The Keggin-type structure is retained after being loaded by HPMo-H₂O₂ and a little peroxophosphomolybdate active species are produced in this process. The active order of different catalysts on the adsorption and oxidation desulfurization presents as the following:HPMo-H₂O₂/CeFe_xO_y@SiO₂＞CeFe_xO_y@SiO₂＞CeFe_xO_y. The introduction of HPMo greatly improves the adsorption activity of organic sulfides, especially its remarkable performance in oxidative desulfurization. The improvement of the performance in oxidative desulfurization is due to the “pseudo-liquid phase” reaction process of polyoxometalate. The dibenzothiophene(DBT) oxidation removal rate reaches 99.4% under such conditions:m(oil)∶m(catalyst)=35∶1, n(H₂O₂)∶n(S)=10∶1 at 60 ℃ for 3 h. The prepared magnetic core-shell oxidative-desulfurization catalyst has ideal recycling performance for oxidative removal of DBT. HPMo-H₂O₂/CeFe_xO_y@SiO₂ catalyst becomes a kind of environmental-friendly catalysts with simple preparation method, high catalytic activity and good stability.