AuPd/SiO_2催化剂用于无溶剂条件下分子氧液相氧化甲苯

采用浸渍法和溶胶负载法制备了一系列Au-Pd双金属催化剂,用氮吸附法,X光粉末衍射(XRD)、程序升温还原(TPR),扫描电镜(SEM)和X射线光电子能谱(XPS)对催化剂进行了表征.以分子氧为氧化剂,在无任何其它溶剂存在的条件下,考察了催化剂制备方法、不同类型载体、Au/Pd原子比、浸渍顺序、活化温度、催化剂用量及反应时间等多种因素对甲苯选择氧化反应的影响.实验结果表明:对SiO_2载体,以共浸渍法制备的催化剂活性和选择性最好;TiO_2载体,以溶胶负载法制备的催化剂活性和选择性较好;Au Pd双金属催化剂比单金或者单钯催化剂具有更好的催化活性.其中Au Pd/SiO_2-I催化剂使甲苯转化率达到56.8%,苯甲酸苄酯的选择性为9 1.3%,TON值为3692.Au Pd/SiO_2-I催化剂中氧化态的钯和零价金更利于催化剂中的电子传递从而利于催化氧化反应的进行.

AuPd/SiO2 Catalyst for Selective Solvent-Free Oxidation of Toluene by Dioxygen

A series of Au-Pd bimetallic catalysts were prepared respectively by modified impregnation and sol immobilization methods. In order to study the textural, structural and redox properties, the samples were characterized by nitrogen adsorption, X-ray diffraction (XRD), temperature-programmed reduction (TPR), scanning electro microscope (SEM) and X-ray electron spectroscopy(XPS). The effects of preparation methods, different supporters, atomic ratio of Au/Pd, impregnation sequence and activation temperature on the activity for solvent-free toluene oxidation with dioxygen were investigated. The results showed that, for impregnation method, the catalysts supported by SiO2 represents better catalytic performance. For sol immobilization method, TiO2 is the preferable support. AuPd bimetallic catalysts presents better activity than monometallic catasysts. AuPd/SiO2 is an effective catalyst exhibiting 56.8% conversion of toluene, 91.3% selectivity to benzylbenzoate and the TON values can be achieved 3692. Au0 and PdO are the active phases in AuPd/SiO2 catalyst, these phases seem to be beneficial to the electron transfer and in favour of the activity of the catalyst.