CeO2负载过渡金属催化氧化甲苯

Catalytic behavior of toluene oxidation on CeO2 supported transition metal catalysts

采用浸渍法制备了一系列过渡金属/CeO 2催化剂,通过催化活性评价和催化表征等方法考察了过渡金属/CeO 2催化剂催化氧化甲苯的活性。研究表明:过渡金属/CeO 2催化剂活性为Mn/CeO 2>Co/CeO 2>Cr/CeO 2>Fe/CeO 2>CeO 2。Mn/CeO 2催化剂具有最低的起燃温度,甲苯转化率达到50%时的温度(T 50)为180℃,其在215℃下甲苯的转化效率可稳定在80%。过渡金属/CeO 2催化剂的活性主要由过渡金属活性组分决定。Mn/CeO 2、Co/CeO 2、Cr/CeO 2和Fe/CeO 2催化剂中活性组分分别为Mn 3O 4、Co 3O 4、Cr 2O 3和Fe 2O 3,其中Mn 3O 4的催化活性最强,Co 3O 4次之。此外,催化剂活性与催化剂的物化结构及活性氧物种有一定的关系。Mn/CeO 2具有最大的比表面积、孔体积和Ce(Ⅳ)的3d 94f 2O2p 4形式比例及合适的活性氧物种比值(晶格氧、表面氧摩尔比为3.8)。

Series of CeO 2 supported transition metal catalysts were prepared by impregnation method.The catalytic behavior of toluene oxidation on CeO 2 supported transition metal catalysts were investigated by activity test and catalyst characterization.The results showed that toluene conversion over transition metal/CeO 2 catalysts decreased in the order of Mn/CeO 2>Co/CeO 2>Cr/CeO 2>Fe/CeO 2>CeO 2.Mn/CeO 2 displayed the lowest light-off temperature.Toluene conversion could reach 50%and 80%on Mn/CeO 2 at 180,215℃,respectively.The activity of CeO 2 supported transition metal catalysts were mainly determined by active site.The active components of Mn/CeO 2,Co/CeO 2,Cr/CeO 2 and Fe/CeO 2 were Mn 3O 4,Co 3O 4,Cr 2O 3 and Fe 2O 3,respectively.The catalytic activity of Mn 3O 4 was the highest,followed by Co 3O 4.Additionally,the activity of catalysts was related to the physicochemical structure and active oxygen species of the catalysts.Mn/CeO 2 had the highest surface area,pore volume and content of 3d 94f 2O2p 4 style of Ce(Ⅳ).An optimum ratio of active oxygen species(molar ratio of lattice oxygen to surface oxygen=3.8)existed on Mn/CeO 2.