Cu/SiO2结构及其催化苯酚羟基化反应性能的研究

Study on the Structure of Cu/SiO2 and Their Catalytic Performance in the Reaction of Phenol Hydroxylation

以不同结构的SiO2为载体,采用传统浸渍法,合成3种负载型的Cu/SiO2.使用X射线衍射(XRD)、N2的等温吸-脱附、紫外漫反射光谱(DR UV-vis)、X射线电子能谱(XPS)、等离子原子发射光谱(ICP)和H2的程序升温还原(H2-TPR)方法对样品进行表征.考察了以H2O2为氧化剂,样品对苯酚直接羟基化合成苯二酚的催化性能.结果表明:具有介孔和MFI结构的二氧化硅(MS-1),稳定性强,有利于引入Cu物种在其孔内扩散及分布,形成更多的高分散CuO.一定反应条件下,Cu/MS-1催化活性最高,苯二酚的收率和选择性分别高达38.91%和81.5%.Cu/MS-1催化剂重复使用10次后,苯二酚的收率为37.64%,而Cu含量仅从2.5%变为2.1%,具有较强稳定性;高分散CuO是目标反应的主要活性物种.

Three kinds of Cu/SiO2 were prepared by the impregnation method using the synthesized and purchased SiO2 with different structures as the support.The samples were characterized by X-ray diffraction(XRD),N2 isothermal absorption-desorption,ultraviolet-visible diffuse reflectance spectra,X-ray photoelectron spectroscopy,inductively coupled plasma atomic emission spectrometry and H2 temperature programmed reduction.The catalystic activity of the samples in the phenol hydroxylation to dihydroxybenzenes using H2O2 was investigated.The results showed that good stability of MS-1 possessing MFI topology and mesoporous structure were advantageous to diffuse copper species from surface to pore and further formed more highly dispersed copper species.The Cu/MS-1 catalysts gave a desired dihydroxybenzenes yield(38.91%)with excellent selectivity(81.5%).The dihydroxybenzenes yield reached up to 37.64%and copper loading of the Cu/MS-1 dropped slightly from 2.5%to 2.1%after use ten runs.The results demonstrated good reusability of Cu/MS-1,and the highly dispersed CuO in samples was main active species of the selective oxidation of phenol with H2O2 produces catechol,hydroqinone and benzoquinone.We believed that MS-1 prepared in this study was a promising metial-supported and was widely used to catalytic field,particularly for those employing in macromolecular liquid reaction.