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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.
A series of Au-Pd bimetallic catalysts were prepared by impregnation and sol-supported methods. The catalysts were characterized by N2 adsorption, XRD, TPR, SEM and XPS ( XPS) were used to characterize the catalysts.The preparation methods, different types of supports, atomic ratio of Au / Pd, impregnation sequence, activation temperature, catalyst dosage and reaction were investigated under the condition of absence of any other solvent in the presence of molecular oxygen as oxidant Time and other factors on the selective oxidation of toluene.The experimental results show that the activity and selectivity of the catalyst prepared by co-impregnation are the best for the SiO 2 carrier; the activity and selectivity of the TiO 2 carrier prepared by sol loading Au Pd bimetallic catalyst has better catalytic activity than mono-gold or mono-palladium catalyst, in which Au Pd / SiO 2 -I catalyst made the conversion of toluene reach 56.8%, the selectivity of benzyl benzoate was 9 1.3%, TON Value 3692.Au Pd / SiO_2-I catalyst in the oxidation state of palladium and zero-valent gold is more conducive to the electron transport in the catalyst in order to facilitate the catalytic oxidation reaction.