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利用极稀悬浮液中蒙脱土的解离作用并结合柱化技术过程,制备了介孔结构的铝铁/蒙脱土复合材料(Fe-Al/mmt);并采用粉末X射线衍射、氮等温吸脱附、傅立叶红外光谱、紫外可见光漫反射光谱及苯酚催化羟基化反应表征了其结构和性能。结果显示,铁铝聚合前驱液中铁/铝比影响复合材料中蒙脱土的解离程度,且仅当低铁/铝比时(即Fe/(Fe+Al)物质的量的比介于0.05-0.3),嵌入解离的蒙脱土片层间的混合铁铝物种呈现能耐温350℃的热稳定性;氮等温吸脱附分析反映出这种解离的蒙脱土堆积结构呈现介孔特征,孔径分布窄,介于2.0-2.3nm;红外分析表明材料表面具有L酸和B酸位,并且L酸位量与嵌入解离的蒙脱土结构中的混合铁铝物种相关;由于结构中混合铁铝物种的存在及相应的Si-O→Fe、Al-O→Fe间的电子跃迁,Fe-Al/mmt材料在紫外区呈现宽泛的能量吸收特征。这些结果说明,由于混合铁铝物种嵌入于解离的蒙脱土片层堆积结构中,形成了“卡片屋”式介孔结构。实验条件下,Fe/(Fe+Al)物质的量的比为0.3的Fe-Al/mmt呈现较佳的催化羟基化性能,苯酚转化率为36.7%,二酚产物选择性32.3%;并且初步表明铝掺杂后,通过铁铝比和表面酸性的调整,材料的部分选择氧化性能可以得到改善。
The mesoporous aluminum-iron / montmorillonite composite (Fe-Al / mmt) was prepared by the dissociation of montmorillonite in a very dilute suspension and the combination of the columnar technology. The powder X-ray diffraction, nitrogen Isothermal adsorption and desorption, Fourier transform infrared spectroscopy, UV-visible diffuse reflectance spectroscopy and phenol-catalyzed hydroxylation were used to characterize its structure and properties. The results show that the Fe / Al ratio in the Fe / Al precursor affects the degree of dissociation of the montmorillonite in the composites, and only when the iron / aluminum ratio is low (ie, the ratio of Fe / (Fe + Al) -0.3). The mixed Fe-Al species embedded in the intercalated layers of montmorillonite showed the thermal stability of 350 ℃. The isothermal adsorption-desorption analysis of nitrogen montmorillonite showed that the dissociated montmorillonite was mesoporous The pore size distribution is narrow, ranging from 2.0 to 2.3 nm. Infrared analysis shows that the surface of the material has L acid and B acid sites, and the amount of L acid sites is related to the mixed Fe-Al species embedded in the montmorillonite structure; The presence of Fe-Al mixed species and the corresponding electronic transitions between Si-O → Fe, Al-O → Fe, Fe-Al / mmt material exhibits a wide range of energy absorption characteristics in the UV region. These results indicate that “card house” type mesoporous structures are formed due to the hybrid Al-Fe species embedded in the delaminated montmorillonite lamellae. Under the experimental conditions, the Fe-Al / mmt ratio of Fe / (Fe + Al) was 0.3. The results showed that the conversion of phenol was 36.7% and the selectivity of bisphenol was 32.3% It shows that after the aluminum doping, the partial selective oxidation performance of the material can be improved by adjusting the iron-aluminum ratio and surface acidity.