H2O、CO2组分对NOx存储-还原性能的影响

Impacts of H2O and CO2 on NOx Storage-Reduction Performance

NOx存储-还原技术是控制汽车稀燃NOx排放的重要手段之一,在汽车尾气中H2O、CO2组分含量均相对较高,有必要弄清这些组分对NOx存储-还原特性的影响.我们以MnOx改性Pt/Ba/Al2O3催化剂为研究对象,评价在不同气氛下的NOx存储能力和催化还原性能.结果表明:CO2、H2O组分均能抑制催化剂的NOx存储性能,H2O的抑制作用主要表现在低温区,CO2对NOx存储性能的抑制作用在高温区更为显著.CO2对NOx存储速率的抑制作用较H2O更为明显,且其NOx存储速率随着温度的升高表现的差异性更为明显.对于NOx催化还原过程,CO2、H2O或CO2+H2O添加均导致N2选择性降低,其N2选择性按CO2>H2O>CO2+H2O的顺序降低.

NOx storage-reduction technology has been regarded as one of the important means to control NOx emissions from lean burn conditions.The H2O and CO2 components in automotive exhaust are relatively high,indicating that it is necessary to understand the impacts of these components on NOx storage-reduction performance.In this work,the MnOx modified Pt/Ba/Al2O catalyst was used as the research object to evaluate the NOx storage capacity and catalytic reduction performance in different atmospheres.It was found that both CO2 and H2O inhibited the NOx storage performance of the catalyst.The H2O-inhibited NOx storage was mainly observed in the low temperature region,while the inhibition of CO2 on NOx storage was more significant in the high temperature region.The inhibition effect of CO2 on NOx storage rate is more obvious than that of H2O component,and the difference of NOx storage rate is gradually clear with the increase of temperature.As for NOx catalytic reduction process,the addition of CO2,H2O or CO2+H2O components led to decrease in the N2 selectivity,which was reduced in the order of CO2>H2O>CO2+H2O.