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采用固相法合成层状α-LiNbWO6,通过质子交换获得HNbWO6,并对其改性得Fe0.33NbWO6、HNbWO6纳米片、HNbWO6/Fe2O3、HNbWO6/Fe2O3-SO42-。利用X射线衍射(XRD)、透射电镜(TEM)、NH3-TPD等方法对催化剂进行表征。利用间二氯苯和乙酰氯的Friedel-Crafts酰化反应合成2,4-二氯苯乙酮来对样品的催化性能进行评价。结果表明:层状化合物对间二氯苯和乙酰氯的Friedel-Crafts酰化反应的催化活性不仅取决于层间距的大小,还取决于酸强度的强弱。由于HNbWO6的层间通道狭窄,反应物无法进入层间,层间的H+无法起到酸催化作用,使HNbWO6没有表现明显的催化作用;Fe3+改性的Fe0.33NbWO6也因为层间通道狭小阻碍反应物进入层间,并且酸强度也明显减小而没有催化活性。剥片后的HNbWO6纳米片使层间酸位暴露出来,酸量增加,但因酸强度下降也导致没有催化作用;Fe2O3柱撑的HNbWO6/Fe2O3不仅增加了层间距,使反应物能进入层间,而且酸量也增加,表现一定的催化效果,HNbWO6/Fe2O3-SO42-使酸位分布更加集中均匀,催化效果更好。实验说明通过增加HNbWO6的层间距和增加酸性强度可以明显提高催化作用。
Hierarchical α-LiNbWO6 was synthesized by solid state reaction. HNbWO6 was obtained by proton exchange and was modified into Fe0.33NbWO6, HNbWO6 nanosheets, HNbWO6 / Fe2O3 and HNbWO6 / Fe2O3-SO42-. The catalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and NH3-TPD. The catalytic performance of the sample was evaluated by Friedel-Crafts acylation of m-dichlorobenzene and acetyl chloride to synthesize 2,4-dichloroacetophenone. The results show that the catalytic activity of layered compounds for the Friedel-Crafts acylation of m-dichlorobenzene and acetyl chloride depends not only on the size of the interlayer spacing but also on the strength of the acid. HNbWO6 did not show obvious catalysis due to the narrow interlayer channels of HNbWO6, the reactants could not enter the interlayer, and H + in the interlayer did not play the role of acid catalysis. Fe3 + 3NbWO6 modified Fe3.3NbWO6 also hindered the narrow channel reaction Into the interlayer, and the acid strength is also significantly reduced without catalytic activity. HNbWO6 nanosheets after stripping exposed the interlayer acidity and increased the amount of acid but did not result in the catalytic effect due to the decrease of acid strength. The HNbWO6 / Fe2O3 with Fe2O3 pillared not only increased the interlayer spacing but also allowed the reactants to enter the interlayer, But also increased the amount of acid, showing a certain catalytic effect, HNbWO6 / Fe2O3-SO42- to make the acid distribution more concentrated, better catalytic effect. Experiments show that by increasing the HNbWO6 layer spacing and increase the acid strength can significantly improve the catalytic effect.