不同形貌Co_(3)O_(4)的控制合成及其催化氧化甲苯性能

Controllable synthesis of Co_(3)O_(4)with different morphologies and its catalytic oxidation performance of toluene

采用溶剂热方法控制合成了一系列具有球状、蝴蝶结状和块状的Co_(3)O_(4)催化剂,并评价其催化氧化消除甲苯的性能。通过X射线衍射(X-ray diffraction,XRD)、扫描电子显微镜(Scanning electron microscopy,SEM)、H2程序升温还原(H2-temperature programmed reduction,H2-TPR)和X射线光电子能谱(X-ray photoelectron spectroscopy,XPS)等方法表征了这些催化剂的结构和表面性质,探讨其形貌结构与活性的关系。研究结果表明,在质量体积空速为40000 mL·g^(-1)·h^(-1)的条件下,所制备的具有不同形貌的三种催化剂中,球状Co_(3)O_(4)催化剂活性最佳,可以在246℃时使甲苯达到90%的转化(T_(90)),而蝴蝶结状和块状催化剂催化甲苯转化的T_(90)分别为250和263℃。而且球状Co_(3)O_(4)催化剂在250℃时,甲苯转化率可以在12 h内保持稳定。表征结果表明,在三种同为尖晶石相的Co_(3)O_(4)催化剂中,球状样品表面的Co3+和晶格氧含量最高,且其氧化能力最强,这可能是该样品具有优异催化氧化甲苯活性的原因。

A series of Co_(3)O_(4)catalysts with spherical,bow-shaped and blocky shapes were prepared by solvothermal method,and their catalytic oxidation performance to remove toluene was evaluated.These catalysts were characterized by X-ray diffraction(XRD),scanning electron microscopy(SEM),H_2-temperature programmed reduction(H_2-TPR)and X-ray photoelectron spectroscopy(XPS)to discuss the relationship among their structure,surface properties and activity.The results show that the spherical Co_(3)O_(4)catalyst exhibits better catalytic activity under the test conditions of weight hourly space velocity of 40000 mL·g^(-1)·h^(-1)among the three catalysts and the temperature of 90%toluene conversion(T_(90))is approximately 246℃,while T_(90)is 250 and 263℃over the bow-shaped and block samples,respectively.Moreover,the conversion rate remains stable at 250℃within 12 h for the spherical Co_(3)O_(4)catalyst.It is concluded that among the three Co_(3)O_(4)catalysts with the same spinel phase,the spherical sample has the highest Co~(3+)and the surface lattice oxygen content,and its oxidation ability is the strongest,which may be the reason for the excellent catalytic oxidation activity of toluene.