一氧化氮Pd-In催化还原反应机理研究

REDUCTION MECHANISM OF NITRIC OXIDE ON Pd-In CATALYST

采用15N同位素标记法研究了NO催化还原反应机理及其含量对反应选择性影响,为实现NO3-选择性还原为N2提供参考数据。结果表明,NO通过吸附在催化剂Pd-In活性中心而参加还原反应,形成中间体N2O以及终产物N2和NH3,其含量控制着还原反应选择性。当NO含量较高时,主导反应是NO分子间相互作用还原为N2;当NO含量较低时,其与吸附氢作用形成NH3的反应明显增强。这主要是与Pd-In催化活性中心对NO吸附存在一个饱和阈值有关。引入NO对亚硝酸根(15NO2-)中15N还原为N2的原子转化率提高作用不明显,可能是因为引入的NO是通过取代NO2-还原产生的进而吸附在催化剂活性中心的NO而参加反应的。

The reduction mechanism of NO and its content on the selectivity of reactions were investigated using isotope labelled nitrogen species （15N）, which is useful for the selective reduction of nitrate to N2 on industry scale. NO participates in the reduction reaction by adsorbing on catalytic active sites of Pd-In, yielding intermediate （nitrous oxide） and products （N2 and NH3）. The concentration of NO governs the eventual product selectivity. When NO content is high, the interaction of adsorbed NO takes the dominant role and the reduction to N： prevails. Whereas NO content is low, the formation ofNH3 is strengthened. This is associated with the adsorption threshold of the Pd-In catalyst for NO. The effect of NO content on the atomic transfer percent of 15^N in nitrite （15NO2-） to N2 is marginal, presumably owing to the fact that the externally induced NO takes part in the reduction by replacing the adsorbed 15NO stemming from 15NO2-.