A series of 0.2 wt% Pd/Sn_(0.9)Ce_(0.1)O_2 catalysts were prepared by impregnation method based on the presynthesis of Sn_(0.9)Ce_(0.1)O_2 support prepared by co-precipitation method, and then characterized by Brunauer–Emmett–Teller(BET), X-ray diffraction(XRD), X-ray photoelectron spectroscopy(XPS), Raman, CO chemical adsorption and hydrogen temperature-programmed reduction(H_2-TPR) techniques. The effect of calcination temperature of the composite oxide support on the catalytic performances of the Pd/Sn_(0.9)Ce_(0.1)O_2 catalyst for the CH_4 total oxidation was studied. It is found that the catalytic activity of the Pd/Sn_(0.9)Ce_(0.1)O_2 catalyst increases with the increase in calcination temperature of the Pd/Sn_(0.9)Ce_(0.1)O_2 support. The 0.2 wt% Pd/Sn_(0.9)Ce_(0.1)O_2/1100 catalyst(the Pd/Sn_(0.9)Ce_(0.1)O_2 support was calcined at 1100 ℃) exhibits the best reactive activity(T_(10)= 255 ℃). The excellent activity of the 0.2 wt% Pd/Sn_(0.9)Ce_(0.1)O_2/1100 catalyst should be attributed to the high reducibility of PdO, the excellent oxygen mobility of the support and the high content of active Pd^(2+) species on the Pd/Sn_(0.9)Ce_(0.1)O_2 catalyst.
Kai ShenJia-Pan LinQian XiaLu DaiGuo-Jun ZhouYang-Long GuoGuan-Zhong LuWang-Cheng Zhan
Hierarchically porous single-crystalline nanosized zeolites as heterogeneous catalysts show great potential in fine chemistry because they offer more rich hierarchically porous channels for the mass transfer and molecular diffusion. However, the synthesis of hierarchically porous nanosized zeolites generally requires the assistance of templates acting as the mesoporogens, which limits its popularity. Herein,we report a one-pot and template-free synthesis of hierarchically porous single-crystalline nanosized zeolite beta only by introducing sodium carbonate in precursor solution. The resulted sample features the extraordinary properties, including the uniform nanocrystal(200–300 nm), high pore volume(0.65 cm^3g^(-1)) and the hierarchical pore-size distribution(e.g. 2–8 and 90–150 nm). After slicing processing, it is interestingly found that a large number of interconnected mesopores penetrate throughout whole material, which enables the hierarchically porous nanosized zeolite beta remarkably superior catalytic activity than the conventional zeolite beta in condensation of benzaldehyde with ethanol at room temperature. More importantly, this one-pot sodium carbonate-assisted synthetic strategy is highly versatile, which has also been successfully developed to synthesize hierarchically porous nanosized singlecrystalline zeolites ZSM-5 and TS.
Xiaoxia ZhouYu ChenTongguang GeZile HuaHangrong ChenJianlin Shi
