杂多酸/离子液体杂化材料催化苯的高选择性羟基化

Highly Selective Hydroxylation of Benzene Catalyzed by Hybrids of Polyoxometalate/Ionic Liquid

制备了V取代的磷钼酸H_3+xPMo_(12-x)V_xO_(40)(x=0,1,2)及1-丁基-3-甲基咪唑溴盐离子液体([C4mim]Br),并采用离子交换的方法制备了系列杂化材料([C4mim]3+xPMo12-xVxO40,x=0,1,2);采用X射线衍射(XRD)、傅里叶变换红外光谱(FT-IR)、紫外-可见漫反射光谱(UV-Vis DRS)对所制备样品进行了表征;以H2O2为氧化剂,考察了所得样品催化苯羟基化制苯酚的活性。结果表明,和相应的离子液体及杂多酸相比,杂化材料的催化活性得到了很大的提高,尤其是催化剂[C4mim]5PMo10V2O40,在优化后的条件下,苯的转化率可达到21%,苯酚的选择性在99%以上。而且,该催化剂具有很好的可重复使用性,连续使用五次后,苯的转化率和苯酚的选择性没有明显降低。

Aseries of hybrid materials （[C4 mim]3＋xPMo12-xVxO40, x = 0, 1,2） based on V-substituted phosphomolybdic acid H3.xPMO12-xVxO40 （x = 0, 1, 2） and ionic liquid 1-butyl-3-methyl imidazolium bromide （[C4mim]Br） have been prepared by an anion-exchange method. The samples were characterized by X-ray diffraction （XRD）, Fourier transform infrared spectrophotometry （FT-IR） and UV-Vis diffuse reflectance spectra （UV-Vis DRS） analysis. The catalytic performances of the samples were tested in oxidation of benzene to produce phenol using H2O2 as the oxidant. The results showed that the hybrids [C4mim]3＋xPMo,2-xVxO40 exhibit much higher catalytic properties than both the corresponding moieties. In particular, under the optimized conditions, 21% of benzene conversion and 99% selectivity for phenol have been obtained with [C4 mim]5PMo10V2O40. The sample also exhibits good reusability and was reused five times without a significant decrease in conversion and selectivity.