SiO_2-TiO_2负载钯催化剂的制备及其催化Suzuki反应研究

Preparation of palladium catalyst supported on SiO_2-TiO_2 and its application in Suzuki reaction

以正硅酸乙酯和钛酸正丁酯作前体,通过均匀沉淀法制备了SiO2-TiO2复合氧化物,并采用X射线粉末衍射(XRD)对复合氧化物进行了表征。采用浸渍制备了复合氧化物负载的钯催化剂Pd/SiO2-TiO2,并考察了负载催化剂在Suzuki反应中的催化性能。当投料摩尔比n(Pd)∶n(PhBr)∶n[PhB(OH)2]∶n(K2CO3)为1∶70∶105∶140,Ti/Si摩尔比和钯质量分数分别为0.5和2.0%时,回流反应10 h,联苯产率达92.8%。负载催化剂通过简单过滤即可回收利用,在5次循环使用过程中,催化活性除第1次有明显降低外,其后基本保持不变。

SiO2-TiO2 mixed oxide was prepared by the homogeneous precipitation method using tetraethoxysilane and tetrabutyl titanate as precursors, and the structure of the products was characterized by X-ray diffraction （XRD）. Palladium catalyst supported on Pd/SiO2-TiO2 was prepared by incipient wetness impregnation method and the catalytic characteristic in Suzuki reaction was investigated. The yield of biphenyl reaches 92. 8% under the conditions that the molar ratio of n（Pd ） of Ti/Si is 0.5 and the mass fraction of ： n（PhBr） ： n[ PhB（ OH）2] ： n（K2CO3 ） = 1：70：105 ： 140, the molar ratio palladium is 2.0%, and the reflux reaction time is 10 h. The supported catalyst can be simply separated by filtration and reused without further disposal. The results show that no significant loss of catalytic activity is observed during the five recycles except for the first run.