Study of Mesostructured CeO2 Synthesis via Nanocasting Using SBA-15 as a Template: Influence of the Cerium Precursor

Mesoporous materials with high surface area, large pore volume, and adjustable pore size are promising in the fields of adsorption and heterogeneous catalysis. In this work, ordered meso-porous ceria structures were successfully prepared via nanocasting using SBA-15 as a template with Ce(NO3)3·6H2O or CeCl3·7H2O as ceria precursors. The materials were characterized before and after template removal. CeO2 crystallite size in the CeO2/SBA-15 composites increases with successive impregnations until they reach the pore size of the SBA 15. Upon removal of the SBA-15 template, the synthesized materials exhibit pore diameters corresponding to the wall thickness of the SBA-15, evidencing that the inverted structure is obtained. Mesoporous ceria exhibits in-creasingly ordered structure up to 5 successive impregnations with 1.3 mmolCe/gSBA-15. Using ce-rium chloride as a precursor, highly ordered structures are reached after only 3 impregnations. The feasibility of this synthesis in fewer steps (1, 3, and 5) employing the same amount of Ce precursor (6.7 mmolCe/gSBA-15) was also studied. Results show a higher ordering degree and oxygen mobility capacity at higher impregnation steps. The mesostructured ceria samples exhibit significantly higher oxygen mobility than commercial bulk ceria, along with high thermal stability, which high-lights the usefulness of these structures.

具备高比表面积、大孔容及可调孔径的介孔材料，在吸附与多相催化领域极具应用前景。本研究以SBA-15为模板，以Ce(NO₃)₃·6H₂O或CeCl₃·7H₂O作为氧化铈前驱体，通过纳米浇铸法成功制备出有序介孔氧化铈结构。本研究对模板去除前后的材料进行了表征分析。CeO₂/SBA-15复合材料中的CeO₂晶粒尺寸随浸渍次数增加而增大，直至达到SBA-15的孔径尺寸。去除SBA-15模板后，合成产物的孔径与SBA-15的孔壁厚度一致，证明成功获得了反相结构。在铈负载量为1.3 mmol Ce/g SBA-15的条件下，介孔氧化铈的有序结构随浸渍次数增加而优化，直至5次浸渍后达到最佳状态。以氯化铈作为前驱体时，仅需3次浸渍即可获得高度有序的介孔氧化铈结构。本研究还探究了在固定铈前驱体负载量（6.7 mmol Ce/g SBA-15）的条件下，采用更少浸渍次数（1、3、5次）的合成可行性。结果表明，浸渍次数越多，材料的有序度与氧迁移能力越高。该介孔结构氧化铈样品的氧迁移能力显著优于商用块状氧化铈，同时具备优异的热稳定性，充分体现了此类结构的应用价值。