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与仅采用一种技术的系统相比,由氮氧化物(NO_x)吸附催化器(NAC)和选择性催化还原(SCR)装置组合的排放控制系统能够对稀燃条件下的NO_x控制提供更大的优势。然而,组合系统也对新的催化剂设计提出了挑战。与仅采用NAC的系统相比,NO_x再生时,NAC+SCR组合系统中NAC生成的氨(NH_3)是所需的特性。组合系统中的SCR需要与单独的SCR技术一样耐热,同时必须能抵抗上游的NAC周期性脱硫时出现的高温稀/浓状态反复变化。研究中,特别为组合系统研发了先进的NAC和SCR催化剂。改进的NAC催化剂展示出更宽广的运行温度窗口,并在减少铂族金属涂敷量的情况下获得了更高的NH_3生成活性。先进的SCR具有优异的低温NO_x还原效率,即便在高温稀/浓状态反复交替后依然具有极好的耐久性。采用改进的NAC和SCR催化剂后,系统性能显著提高。新研发的催化剂的优势也在车辆上得到了验证。
The emission control system, which is a combination of a nitrogen oxide (NO x) adsorption catalyst (NAC) and a selective catalytic reduction (SCR) unit, can provide greater NO x control in lean conditions compared to a system that employs only one technique The advantages. However, the combination system also poses a challenge to the new catalyst design. The NAC-generated ammonia (NH 3) in the NAC + SCR system is the desired characteristic when NO_x is regenerated compared to a system using only NAC. The SCR in the combined system needs to be as heat-resistant as the SCR technology alone and must be able to withstand repeated high and low temperature / rich conditions that occur during upstream NAC periodic desulfurization. In the study, advanced NAC and SCR catalysts were specially developed for the combined system. The improved NAC catalyst exhibits a broader operating temperature window and achieves higher NH3 production activity with less platinum group metal coating. Advanced SCR has excellent low-temperature NO_x reduction efficiency, even after repeated high-temperature dilute / rich state still has excellent durability. System performance is significantly improved with the improved NAC and SCR catalysts. The advantages of newly developed catalysts have also been validated in vehicles.