CAJ | 학술논문

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2.0～2.3 nm;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.
이용겁희현부액중몽탈토적해리작용병결합주화기술과정,제비료개공결구적려철/몽탈토복합재료(Fe-Al/mmt);병채용분말X사선연사、담등온흡탈부、부립협홍외광보、자외가견광만반사광보급분분최화간기화반응표정료기결구화성능.결과현시,철려취합전구액중철/려비영향복합재료중몽탈토적해리정도,차부당저철/려비시(즉Fe/(Fe+Al)물질적량적비개우0.05～0.3),감입해리적몽탈토편층간적혼합철려물충정현능내온350℃적열은정성;담등온흡탈부분석반영출저충해리적몽탈토퇴적결구정현개공특정,공경분포착,개우2.0～2.3 nm;홍외분석표명재료표면구유L산화B산위,병차L산위량여감입해리적몽탈토결구중적혼합철려물충상관;유우결구중혼합철려물충적존재급상응적Si-O→Fe、Al-O→Fe간적전자약천,Fe-Al/mmt재료재자외구정현관범적능량흡수특정.저사결과설명,유우혼합철려물충감입우해리적몽탈토편층퇴적결구중,형성료"잡편옥"식개공결구.실험조건하,Fe/(Fe+Al)물질적량적비위0.3적Fe-Al/mmt정현교가적최화간기화성능,분분전화솔위36.7%,이분산물선택성32.3%;병차초보표명려참잡후,통과철려비화표면산성적조정,재료적부분선택양화성능가이득도개선.
Using delamination of the ultra dilute montmorillonite (mmt) suspension and pillaring techniques, the mixed Fe-Al/montmorillonite (Fe-Al/mmt) composites with mesoporous structure have been synthesized. Powder X-ray diffraction (XRD), N2 adsorption-desorption isotherms, Fourier transform infrared spectroscopy (FTIR), UVVis-diffuse reflectance spectroscopy (UV-Vis-DRS) and catalytic hydroxylation of phenol with H2O2 were used to characterize the samples. The XRD results suggest that the content of Fe plays an important role in the delaminating degree of mmt owing to flocculation of Fe-Al polyoxycations precursors. Only under lower molar ratio of0.05 to 0.3 of Fe/(Fe+Al), can Fe-Al/mmt composites with the intercalated and occluded mixed thermally stable Fe-Al oxide particles up to 350 ℃ be obtained. Accordingly, the nitrogen sorption isotherms of resulting samples are of mesoporous type with hysteresis loops and narrow pore size distribution. The FTIR spectra preliminarily show the synthesized Fe-Al/mmt composites contain both Bronsted and Lewis acid sites. Lewis acid sites could be mainly provided and adjusted by intercalated/occluded mixed Fe-Al species. The UV-Vis-DRS spectra indicate the occurrence of clay Si-O → Fe and Al-O → Fe charge transfer transitions and interband transitions, leading tothe characteristic broad absorbance and confirming the formation of mixed Fe-Al oxide in mmt aggregates. So it has been postulated that under experimental conditions, when the ultra dilute mmt suspension was used, the flocculation of mmt by pillaring Fe-Al polyoxycations could lead to delaminated aggregates, the "card-house" structure occluding in mixed Fe-Al polyoxycations species. The catalytic activity of phenol hydroxylation was at a ratio of Fe/(Fe+Al)=0.3 with phenol conversion of 36.7% and selectivity to hydroxylation products of 32.3%. The doping of alumina could improve the catalytic partial oxidation via adjustment of Fe/(Fe+Al) ratio and the surface acidity.