钴、钾浸渍的介孔分子筛的制备、表征与催化氧化性能研究

Preparation,Characterization and Catalytic Oxidation Performance of Co,K-Impregnated Mesoporous Molecular Sieves

以六方介孔二氧化硅分子筛(HMS)为载体,以水合醋酸钴、醋酸钾为浸渍金属前驱体,乙二醇为浸渍溶剂,采用初始湿法浸渍法制备了钴、钾负载的介孔分子筛。合成材料用X射线粉末衍射(XRD)、N2吸附-脱附等温线、漫反射紫外可见光谱(UV-VIS)和热重-差热分析(TG-DTA)进行了表征,并考察了它们在温和的反应条件下,以分子氧为氧化剂在对叔丁基甲苯液相氧化中的催化性能。结果表明,钴载量为4%(wt),钾载量为2%～6%(wt)时,合成材料具有较好的介孔结构和较大的BET比表面积(490～865m2·g-1)和孔体积(0.69～0.87cm3·g-1)。合成材料中四配位钴(Ⅱ)为主要的金属物种。在实验条件下,催化剂在反应中表现出较好的催化活性,4%Co-2%K-HMS在反应中表现出最好的催化活性,对叔丁基甲苯的转化率为26.8%,对叔丁基苯甲醛的收率为21.0%。Co-HMS中适当掺杂钾有利于提高催化活性和稳定性。

The catalysts with cobalt and potassium supported on mesoporous molecular sieves were prepared by incipient wetness impregnation using cobalt acetate tetrahydrate and potassium acetate as metal precursors,hexagonal mesoporous silica（HMS） as support and ethylene glycol as impregnation solvent.The catalysts prepared were characterized by powder X-ray diffraction（XRD）,nitrogen adsorption-desorption isotherms,diffuse reflectance UV visible spectroscopy（UV-VIS） and differential thermal analysis（TG-DTG）,respectively.The results show that the prepared catalysts possess mesostructure,high BET surface area（490～865 m2·g-1） and pore volume（0.69～0.87 cm3·g-1）;The tetrahedral divalent cobalt is dominant metal species in the samples of Co,K-supported HMSs.The catalytic performances of the prepared Co,K-supported HMSs were tested by the oxidation reaction of 4-ter-butyltoluene in liquid phase under mild reaction conditions with dioxygen as oxidant.Results show that the prepared catalysts offer good catalytic activities in the oxidation reaction;and among them,the 4%Co-2%K-HMS exhibits higher activity and gives 21.0% yield of 4-ter-butylbenzaldehyde with 26.8% conversion of 4-ter-butyltoluene.It was found that the adding proper amount of potassium in the Co-HMS results in improving its catalytic activity and stability.