蒙脱土结构和性质对催化不饱和脂肪酸二聚化反应的影响

钠基蒙脱土经过一次插层有机改性和二次插层有机改性后制得有机改性蒙脱土，作为催化剂用于催化不饱和脂肪酸二聚化反应制备二聚酸。采用XRD、SEM、TEM、FTIR和TG等检测手段对有机改性后蒙脱土的内层结构和性质进行分析。实验表明改性后蒙脱土层间距由1.48 nm扩大到3.82 nm，而且保持原来的夹心结构不变。蒙脱土的表面形貌和内部结构发生改变，表面变得疏松，内部层间距扩大且插层剂含量增加，分散实验表明二次插层有机改性蒙脱土在不饱和脂肪酸中分散性能优异。相同条件下，二次插层有机改性蒙脱土催化不饱和脂肪酸二聚化反应，二聚酸产率75.33%，是未改性蒙脱土催化制得二聚酸产率的2.14倍，并通过FTIR、¹H NMR和LC-MS证实合成的产物为二聚酸。

Effect of structure and properties of montmorillonite on catalytic dimerization of unsaturated fatty acids

The organic modified montmorillonite was prepared by first and second intercalation modification of Na-montmorillonite,which was used to catalyze the reaction of technical grade oleic acid to prepare dimer acid,and the influence of the catalyst structure and composition on the catalytic performance was analyzed. All the samples were characterized by X-ray diffraction (XRD),Fourier transform-infrared spectroscopy (FTIR),scanning electron microscope (SEM),transmission electron microscopy (TEM),thermogravimetry (TG),and dispersion experiments. The experimental results show that the layer spacing of modified montmorillonite is expanded from 1.48 nm to 3.82 nm,and the original sandwich structure remains unchanged. The surface morphology and internal structure of modified montmorillonite were changed,the surface became loose,the interlayer spacing was enlarged,and the content of intercalation agent was increased. The dispersion experiment showed that the montmorillonite had good dispersion performance in oleic acid after second modification. Under the same conditions,the second intercalation montmorillonite catalytic dimerization reaction of oleic acid,yield of dimer acid was 75.33%,which was 2.14 times higher than that of Na-MMT. Through FTIR,¹H NMR and LC-MS showed that the synthesized product is dimer acid. Thus,it is evident that,the wider the interlayer spacing,the stronger the dispersion,and the better is the catalytic performance,this indicates that increasing the interlayer spacing and lipophilicity of MMT can promote the diffusion and adsorption of unsaturated fatty acids,thereby significantly increasing the yield of dimer acid.