铁-锆交联蒙脱土的制备和结构表征

我们首次合成了铁锆复合柱交联蒙脱土, 并用XRD, 比表面及孔径测定和Mossbauer谱学等方法进行了表征。结果表明, 铁锆交联蒙脱土比表面增大为原土的三倍以上, 其层间距可达0.88nm(d001=1.84nm)。热稳定性明显高于单一Fe柱交联蒙脱土。在500℃加热后层间距保持0.63nm~0.71nm。但由于铁柱的坍塌造成微孔减少, 比表面明显下降。Mossbauer谱研究表明, 500℃焙烧单一铁柱转变为α-Fe~2O~3, 而Fe-Zr-PILC中铁仍以超顺磁Fe^3^+存在, 单一铁柱的铁组分在400℃可还原为金属铁, 而铁锆混合柱交联蒙脱土中由于铁与锆之间存在较强的相互作用, 450℃氢气气氛中铁组分仍不能还原为金属铁。

Preparation and characterization of hydroxy-Fe-Zr pillared crossed-linked montmorillonites

Hydroxy-Fe-Zr pillared clays (Fe-Zr-PILC) with basal spacing of 1.84nm was first prepared. Three different preparation routes were studied. The most stable Fe-Zr-PILC can be obtained by first intercalating montmorillonite with hydroxy-Zr to prepare Zr-PILC and then using hydroxy-Fe-pillaring agent to intercalating Zr-PILC. For comparison study, Fe-PILC and Zr-PILC were also prepared. The pillar structure, and thermal stability of the samples were determined by XRD, BET surface area and average pore diameter measurement and Mossbauer spectroscopy. It was found that the surface area of the prepared Fe-Zr-PILC was 158m^2/g almost three times larger than that of the montmorillonite. after treated in air at 500℃, for this sample the basal spacing was kept almost unchanged, but the surface area decreased to 98.8m^2/g. For Fe-PILC, after treated at 350℃, due to the collapse of the Fe pillar, the basal spacing decreased from 1.64nm to 1.04nm and the surface area decreased from 143.8m^2/g to 114.6m^2/g. However after treated at 500℃ in air, the basal spacing and the surface area of Zr-PILC were all kept constant. So we may suggest that the Zr-pillar is responsible for the constant basal spacing of Fe-Zr-PILC and the decrease of the surface area and the increase of the average pore diameter in due to the callapse of the Fe pillar. Mossbauer study showed that after treated at 500℃, for Fe-PILC, α-Fe~2O~3 was formed, but only Fe^2^+ and supermagnetic Fe^3^+ species can be found for Fe-Zr-PILC, It seems that there is a strong interaction between iron and zirconium component in Fe-Zr-PILC, the iron oxide component in Fe-Zr-PILR is highly dispersed on Zr pillar surface as supermagnetic state and in this case, the crystalline α-Fe2O3, can not be formed. After reduced in H2 at 400℃, 64% iron oxide pillar in Fe-PILC was reduced to Fe°, however, in Fe-Zr-PILC, due to the Fe-Zr interaction, iron component still kept as Fe^3^+ and Fe^2^+ state even after reduction at 450℃.