摘要
用TPR,H_2-O_2滴定技术研究了Mn-O/γ-Al_2O_3(Ⅰ)和 Mn-Ce-O/γ-Al_2O_3(Ⅱ)催化剂中氧和氢的反应,并用XRD,AES和XPS对(Ⅰ)和(Ⅱ)的固相结构和表面组成进行了表征。结果表明,(Ⅰ)的TPR谱有三种氢吸收峰,峰温为350和430℃的峰分别表征MnO_2和Mn_2O_3的氧的还原,680℃的峰为Mn和Al界面共有氧的还原。铈的存在不影响(Ⅰ)TPR特征峰,但使350℃峰的面积(对应于MnO_2的量)有较大的增加。当CeO_2的含量大于10％时680℃峰消失。铈还能提高氧化锰的分散度,使β-MnO_2和Mn_2O_3的聚集相在XRD谱中消失,并提高其贮氧能力约40％,增强了还原态试样的吸氧恢复能力。还原态(Ⅰ)在室温中第一个脉冲的吸氧量为0.5ml/g-cat,还原态(Ⅱ)为 1.56ml/g-cat。
TPR, XRD, XPS, ESR and H2-O2 pulse injection were used to study the reaction between H2 and oxygen in Cu-Mn-O(I) and Cu-Mn-Ce-O(II) supported on alumina, and their oxygen storage capacity and solid structure were also studied. The results show that the TPR traces of (Ⅰ) and (Ⅱ) are similar to that of Cu-O/y-Al2O3 and the TPR feature peaks of Mn-O, Ce-O are not seen; as CeO2 loading increases to more than 10%, the peak temperature of (Ⅱ) is lower than that of (Ⅰ); the reoxidizing(Ⅱ) prereduced is easier than(Ⅰ) prereduced. The presence of Ce inhibits the growth of the spinel phases (CuMn2O4) and makes Cu, Mn of high valence state more stable. There is Cu0 in(Ⅱ) prereduced but it disappears after reoxidation. H2-O2 titration indicates that the addition of CeO2 into(Ⅰ) enhances its oxygen storage capacity and the reaction between H2 and oxygen of the catalysts.
