采用浸渍法制备了经不同温度焙烧的CuO/γ-Al 2O3催化剂, 并通过BET、XRD、UV-DRS、H2-TPR以及CO完全氧化反应, 研究了不同焙烧温度对CuO/γ-Al2O3催化剂中CuO组分的分散、还原和催化性质的影响. 结果表明: 当焙烧温度为450℃时, CuO在γ-Al2O3上的分散容量约为0.56mmol/100m2; 当焙烧温度达到750℃时, Cu2+同时占据γ-Al2O3载体(110)面上的八面体和四面体空位. 对于450℃焙烧的低CuO含量的样品, 在H2-TPR结果中只观察到处于八面体空位的CuO物种的还原, 而经750℃焙烧的样品则同时观察到处于八面体和四面体空位的CuO物种的还原, 且处于八面体空位的CuO的还原会促进处于四面体空位的CuO的还原. 处于八面体空位的CuO在CO完全氧化反应中的活性要高于处于四面体空位的CuO.
CuO/γ-Al2O3 samples were prepared by impregnating γ-Al2O3 with an aqueous solution containing requisite amount of Cu(NO3)2. BET, XRD, UV-DRS, H2-TPR and CO oxidation were employed to characterize the dispersion, reduction behavior and catalytic properties of CuO/γ-Al2O3 catalyst calcinated at different temperatures. The results indicate that the dispersion capacity of CuO on the surface of γ-Al2O3 is about 0.56mmol/100m2 when it is calcinated at 450℃; while for the samples calcinated at 750℃, Cu2+ would occupy both the octahedral and tetrahedral vacant sites on the (110) plane of γ-Al2O3. For samples with low CuO loading amount, only the reduction peak of Cu2+ in octahedral coordination environment is observed in xxCu/Al-450 samples; while for xx Cu/Al-750 samples, the reduction peaks of Cu2+ in octahedral and tetrahedral coordination environment can be observed and the reduction of Cu2+ in octahedral coordination environment would promote the reduction of Cu2+ in tetrahedral coordination environment. The CO oxidation results indicate that the activity of dispersed CuO species in octahedral coordination environment is higher than that in tetrahedral coordination environment.
参考文献
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