Cu/SiO_(2)模型催化剂上甲醇部分氧化制氢反应研究

Investigation of Partial Oxidation of Methanol to Hydrogen over Cu/SiO_(2) Catalysts

采用浸渍法 ,制备了不同组成的 Cu/ Si O2 、 Cu/ Zn/ Si O2 催化剂 ,考察了 Cu负载量及 Cu/ Zn比对甲醇部分氧化制氢 (CH3OH+1/ 2 O2 → 2 H2 +CO2 )反应的影响 .结果显示 ,当 Cu的负载量为 10 %、 Cu/ Zn比为 7∶ 3时 ,催化剂活性最好 .H2 - TPR、XRD、XPS等表征结果表明 ,催化剂的制氢活性与 Cu0有关 ,而大量 Cu+与 Cu2 +的存在则不利于催化剂活性的提高 .Zn助剂的引入 ,有利于分散 Cu0 物种 ,提高催化剂的活性 ;但由于同时稳定了Cu+物种 ,导致 Cu2 O物种的大量生成 ,从而提高了催化剂的还原温度 ,抑制了 Cu0的氧化还原过程 (Cu2 +→Cu+ → Cu0 或 Cu0 → Cu+ → Cu2 + ) ,降低了催化剂的活性 .因此 ,对于 Cu/ Zn/ M催化剂 ,存在一个最佳的 Cu/ Zn比 .

The partial oxidation of methanol to hydrogen (CH\-3OH+1/2 O\-2→2 H\-2+CO\-2) was investigated over Cu/SiO\-2? Cu/Zn/SiO\-2 catalysts prepared by impregnation methods. Catalyst performances have been investigated with the different Cu loading on the Cu/SiO\-2 and the various Cu/Zn ratios on the Cu/Zn/SiO\-2 catalysts at 473 K. The kinetic study shows that 10%Cu loading with Cu/Zn=7∶3 exhibit higher CH\-3OH conversion and higher H\-2 selectivity comparing with other catalysts. The results of H\-2 TPR, XRD, XPS characterization reveal that the active site of catalyst is related to Cu\+0 and the existence of excess Cu\++ and Cu\+\{2+\} are not helpful to improve the activity of the catalysts. In addition, the results of introduction of the Zn show that the suitable amount of Zn helps to disperse Cu\+0, which lead to the good performances of the catalysts and the excess Zn introduced is helpful to stabilize Cu\++ species and increase the reduction temperature, which inhibits the process of redox of Cu\+0 (Cu\+\{2+\}→Cu\++→Cu\+0 or Cu\+0→Cu\++→Cu\+\{2+\}). So it can be concluded that there must be suitable Cu/Zn ratio for Cu/Zn/M catalyst.