还原剂和水蒸汽对钯催化NO还原反应性能的影响

为满足严格的排放法规，在控制好NOx排放的同时，也需减少N2O、NH3等二次污染物的排放。为探究尾气组分对NOx还原产物的影响，本文用催化活性模拟评价装置，对自制单钯三效催化剂，进行了还原剂种类、CO浓度及水蒸汽浓度对NO转化效率及N2O和NH3生成产物的影响研究。结果表明，CO催化还原NO是导致N2O生成的主要原因，其内在本质在于催化剂表面活性氧物种的协同作用，NH3的生成量在150~400 ℃范围内与反应温度正相关；水蒸汽的加入会促进N2O和NH3的生成，H2O分子在催化剂表面吸附作用抑制了活性氧物种的消耗；增加CO浓度可抑制N2O生成但会促进NH3生成。

Effects of reductants and steam on the palladium-catalyzed reduction of NO

Besides controlling NOx emissions, reducing the emissions of secondary pollutants including N2O and NH3 is required to meet the strict emission regulations. In order to understand the effects of exhaust gas components on catalytic NOx reduction, NO conversion as well as the formation features of N2O and NH3 were tested on a catalytic activity simulation evaluation device and the catalytic reaction was carried out by using a self-prepared three-way catalyst under different reductants and at different concentrations of CO and steam. It was found that N2O formation was significantly ascribed to the catalytic reduction of NO by CO, because of the synergistic effect of active oxygen species on the catalyst surface. And the amounts of NH3 formation were positively correlated with the reaction temperature in the range of 150~400 ℃. Introducing water vapour led to an increase in N2O and NH3 contents and the adsorption of H2O molecules on the catalyst surface inhibited the consumption of reactive oxygen species. Increasing CO concentration would reduce N2O formation but promote NH3 generation.