To elucidate the reactions involved in the three-way catalyst under stoichiometric conditions, the reactivity of CO + NO has been studied by continuous flow and surface reactions over Pd supported on Ce_0.75Zr_0.25O₂ (CZO) and Al₂O₃ model catalysts with different Pd particles sizes and oxidation states. Pd/CZO showed higher activity with complete NO removal at 125 °C than Pd/Al₂O₃ at 300 °C As a primary by-product, N₂O was produced on both catalysts prior to reaching complete CO conversion in a 1:1 NO/CO feed ratio. NO inhibition through N₂O formation was intensified when 2:1 NO/CO feed ratio was used, where the complete CO conversion can’t be achieved during the course of the reaction. When 1:1 NO/CO feed ratio was used over Pd/Al₂O₃, a concave feature in the CO light-off curve was observed, where the CO light-off curve showed a downward inflections after complete NO conversion had been reached, and then started to increase again with further increase in temperature. The inflection of CO conversion coincided with the maximum yield of N₂O vs. reaction temperature. It was also found that the CO + NO reactivity was affected by the Pd oxidation state and particles size. in situ DRIFT experiments showed that the formation of NCO and NCO-derived N₂O intermediate species is closely related to the inflection of CO conversion. A pathway of N₂O formation via the NCO intermediate species has been proposed to be responsible for the fallback in CO conversion when the reaction temperature increased, as both interactions of “NCO_ad + N_ad” and “NCO_ad + NO_ad," which produce N₂ and N₂O, respectively, consume NO but generate CO.

为了阐明化学计量条件下三元催化剂的反应，通过在Ce _0.75 Zr _0.25 O ₂（CZO）和Al ₂ O ₃模型催化剂上负载的Pd上的连续流动和表面反应，研究了CO + NO的反应性。具有不同的Pd颗粒尺寸和氧化态。Pd / CZO在300°C时具有比Pd / Al ₂ O ₃更高的活性，在125°C时可完全去除NO。作为主要副产物，两种催化剂均会先生成N ₂ O，然后以1的比例完全转化为CO： 1 NO / CO进料比。通过N ₂抑制NO当使用2：1的NO / CO进料比时，O的形成会加剧，在反应过程中无法实现完全的CO转化。当使用1：1的NO / CO进料比Pd / Al ₂ O _3时，在CO起燃曲线中观察到凹形特征，其中在达到完全NO转化后，CO起燃曲线显示出向下的拐点。 ，然后随着温度的进一步升高而再次升高。CO转化率的变化与N ₂ O相对于反应温度的最大产率相吻合。还发现CO + NO反应性受Pd氧化态和颗粒尺寸的影响。原位DRIFT实验表明NCO和NCO衍生的N _2的形成O中间物种与CO转化的影响密切相关。已提出当反应温度升高时，通过“ NCO _ad + N _ad ”和“ NCO _ad + NO _ad ”的相互作用，通过NCO中间物种形成N ₂ O的途径是导致CO转化率下降的原因。分别产生N ₂和N ₂ O的NO消耗NO但产生CO。