In this study, we designed an active hydrocarbon (HC) trap with additional low-temperature HC oxidation ability. For this, we employed a wet impregnation method to add Cu⁺ ions (for HC adsorption) inside a zeolite socony mobil-5 (ZSM-5) zeolite and CuO particles (for HC oxidation) on the outer surface. To elucidate the effect of the zeolite support on the activity, two types of zeolite were used as supports: Na-form and H-form ZSM-5 s. Interestingly, in Na-form ZSM-5 s, the preferred formation of CuO particles occurred on the outer surface, whereas in H-form ZSM-5 s, Cu⁺ ions were placed inside the zeolite and tiny CuO particles formed on the outer surface. Accordingly, the Cu-impregnated H-form ZSM-5 showed much improved cold start test (CST) performance with respect to representative HCs (propene and toluene). In addition, hydrothermal treatments under various conditions were conducted to simulate different degrees of long-term driving. Furthermore, we found a clear correlation between the CST performances of the Cu-impregnated ZSM-5 zeolites and the physicochemical properties. To the best of our knowledge, we, for the first time, show that the chemical properties of Cu⁺ ions and Lewis acid sites, corrected by appropriate physical properties (in this case, the micropore volume), can account for the HC removal abilities of fresh and hydrothermally treated Cu-impregnated ZSM-5 zeolites. Furthermore, we demonstrated the effective oxidation ability of the tiny CuO particles (as small as ca. 3.2 nm) on the outer surface of Cu-impregnated H-form ZSM-5 s at low temperatures (ca. 210 °C), thus yielding an active HC trap. Finally, the preferred adsorption and low-temperature oxidation worked synergistically for HC removals.

在这项研究中，我们设计了一种具有额外低温 HC 氧化能力的活性碳氢化合物 (HC) 捕集器。为此，我们采用湿浸渍法在沸石 socony mobil-5 (ZSM-5) 沸石内添加 Cu ⁺离子（用于 HC 吸附），并在外表面添加 CuO 颗粒（用于 HC 氧化）。为了阐明沸石载体对活性的影响，使用两种类型的沸石作为载体：Na 型和 H 型 ZSM-5 s。有趣的是，在 Na 型 ZSM-5 s 中，CuO 颗粒的优选形成发生在外表面，而在 H 型 ZSM-5 s 中，Cu ⁺离子被放置在沸石内部，并在外表面上形成微小的 CuO 颗粒。因此，铜浸渍的 H 型 ZSM-5 相对于代表性的 HC（丙烯和甲苯）显示出大大改善的冷启动测试 (CST) 性能。此外，还进行了各种条件下的水热处理，以模拟不同程度的长期驾驶。此外，我们发现浸渍铜的 ZSM-5 沸石的 CST 性能与理化性质之间存在明显的相关性。据我们所知，我们首次证明了 Cu ⁺的化学性质离子和路易斯酸位点，通过适当的物理特性（在这种情况下，微孔体积）进行校正，可以解释新鲜和水热处理的铜浸渍 ZSM-5 沸石的 HC 去除能力。此外，我们证明了在低温（约 210°C）下铜浸渍的 H 型 ZSM-5 s 外表面上的微小 CuO 颗粒（小至约 3.2 nm）的有效氧化能力，从而产生一个活跃的 HC 陷阱。最后，优选的吸附和低温氧化协同作用去除 HC。