The removal of nitrogen oxides (NOx), which are major atmospheric pollutants, in exhaust gas after-treatment systems, has been studied extensively. The catalytic reduction of NOx in lean-burn environments is challenging in diesel after-treatment technology. The most relevant catalytic NOx reduction technologies for diesel engines are summarized in this review paper, focusing on current catalytic after-treatment systems for compliance with emission standards. Four promising after-treatment technologies for the abatement of tail-pipe NOx emissions are discussed: (i) lean NOx trap (LNT) and LNT combined with selective catalytic reduction (SCR) (LNT + SCR), (ii) Urea/NH₃-SCR, (iii) Hydrocarbon-SCR (HC-SCR), and (iv) CO/H₂-SCR. The relevant reaction mechanisms and current major challenges are reviewed in detail. The effects of the active phases and support modifications of the respective catalysts are examined to evaluate their contribution to the after-treatment systems. Major issues in practical applications, such as hydrothermal aging, chemical poison, and metallic additives for improving de-NOx performance, are extensively reviewed in this paper.

在废气后处理系统中，作为主要大气污染物的氮氧化物（NOx）的去除已被广泛研究。在稀燃环境中催化还原NOx在柴油后处理技术中具有挑战性。这篇综述总结了与柴油机最相关的催化NOx还原技术，重点关注当前符合排放标准的催化后处理系统。讨论了减少尾管NOx排放的四种有前途的后处理技术：（i）稀薄的NOx捕集器（LNT）和LNT与选择性催化还原（SCR）（LNT + SCR）结合，（ii）尿素/ NH ₃ -SCR，（iii）烃-SCR（HC-SCR）和（iv）CO / H ₂-SCR。详细审查了相关的反应机制和当前的主要挑战。检查活性相和相应催化剂的载体改性的效果，以评估它们对后处理系统的贡献。本文广泛地审查了实际应用中的主要问题，例如水热老化，化学毒物和提高脱硝性能的金属添加剂。