Mechanistic proposals for the different SCR subreactions are integrated into one surface reaction mechanism that describes the main SCR reactions (Standard SCR, Fast SCR, NO₂ SCR), transient effects due to nitrate storage, as well as the production of the side product N₂O over a copper chabazite catalyst. The mechanism is parameterised to steady state and transient experiments, and is shown to predict the behaviour of the catalyst during a driving cycle, without any refitting of kinetic parameters.

A dual site approach is used, where site 1 accounts for the adsorbed ammonia that forms on the Brønsted acid sites and copper ions, while site 2 is a copper ion (Cu²⁺-OH) where nitrites and nitrates are adsorbed. All main SCR reactions proceed via a reaction between ammonia and nitrites (ammonium nitrite pathway) to produce nitrogen; nitrites are also the linking species between the Standard SCR and NO oxidation reactions. Reactions between nitrates and ammonia to produce ammonium nitrate are also included, along with ammonium nitrate decomposition pathways (i.e., via NO addition to feed). Additionally, a global reaction taking place between adsorbed ammonia and gaseous NO₂ to produce N₂ at low temperatures (< 250 °C) is added, to account for an observed reaction taking place on the copper-free zeolite.

The mechanism was used to analyse the importance of nitrate formation during a standard driving cycle. Surprisingly, although a significant amount of inhibitive ammonium nitrate is modelled to form during low temperature Fast and NO₂ SCR steady state experiments, almost no ammonium nitrate is predicted to form during the driving cycle, thus allowing for a higher reaction activity than predicted based on steady state data. From a modelling and catalyst testing perspective, this shows the importance of capturing the catalyst’s transient behaviour rather than only steady state conditions, since steady state is not necessarily reached during practical driving scenarios.

针对不同SCR子反应的机理建议被整合到一个表面反应机理中，该机理描述了主要的SCR反应（标准SCR，快速SCR，NO ₂ SCR），由于硝酸盐存储而产生的瞬态效应以及副产物N _2的产生O在菱沸石铜催化剂上。该机制被参数化为稳态和瞬态实验，并显示出可预测驾驶循环中催化剂的行为，而无需任何动力学参数的调整。

使用双重位点方法，其中位点1解释了在布朗斯台德酸位点和铜离子上形成的吸附氨，而位点2是其中吸附有亚硝酸盐和硝酸盐的铜离子（Cu ²⁺ -OH）。所有主要的SCR反应都是通过氨和亚硝酸盐之间的反应（亚硝酸铵途径）进行的，从而产生氮；亚硝酸盐也是标准SCR和NO氧化反应之间的连接物质。还包括硝酸盐和氨之间的反应，以生成硝酸铵，以及硝酸铵的分解途径（即，通过向进料中添加NO）。另外，在吸附的氨和气态NO ₂之间发生全局反应以生成N ₂ 在低温（<250°C）下添加，以说明观察到的在无铜沸石上发生的反应。

该机制用于分析标准驾驶循环中硝酸盐形成的重要性。出人意料的是，尽管模拟了在低温快速和NO ₂ SCR稳态实验期间形成大量的抑制性硝酸铵，但预计在驾驶周期内几乎不会形成硝酸铵，因此，其反应活性高于基于稳态数据。从建模和催化剂测试的角度来看，这表明了捕获催化剂的瞬态行为的重要性，而不仅仅是稳态条件，因为在实际驾驶情况下不一定达到稳态。