Ting-Ting Xu, Gang-Gang Li, Kai-Hua Zheng, Xin-Yan Zhang, Xin Zhang, Shao-Qing Zhang
School of Chemistry and Environmental Engineering, Changchun University of Science and Technology Changchun 130022 P. R. China
National Engineering Laboratory for VOCs Pollution Control Material & Technology, University of Chinese Academy of Sciences Beijing 101408 P. R. China.
RSC Adv. 2022 Dec 23;13(1):638-651. doi: 10.1039/d2ra06708k. eCollection 2022 Dec 19.
In this study, a core-shell catalyst of Cu-SAPO-34@Fe-MOR was successfully prepared through a silica-sol adhesion method, and its performance for selective catalytic reduction of nitric oxide by NH (NH-SCR) was evaluated in detail. The Fe-MOR coating has not only increased the high-temperature activity and broadened the reaction temperature window of Cu-SAPO-34 to a large extent, but also increased the hydrothermal stability of Cu-SAPO-34 markedly. It is demonstrated that a strong synergistic interaction effect exists between Cu and Fe ions and promotes the redox cycle and oxidation-reduction ability of copper ions, which greatly accelerates the catalytic performance of the core-shell Cu-SAPO-34@Fe-MOR catalyst. Abundant isolated Cu ions and Fe ions on the ion exchange sites performing NO reduction at low and high temperature region lead to the broad reaction temperature window of Cu-SAPO-34@Fe-MOR. In addition, more weakly adsorbed NO species formed and the increased number of Lewis acid sites may also contribute to the higher catalytic performance of Cu-SAPO-34@Fe-MOR. On the other hand, the better hydrothermal ageing stability of Cu-SAPO-34@Fe-MOR is related to its lighter structural collapse, fewer acidic sites lost, more active components (Cu and Fe) maintained, and more monodentate nitrate species formed in the core-shell catalyst after hydrothermal ageing. Last, the mechanism study has found that both Langmuir-Hinshelwood ("L-H") and Eley-Rideal ("E-R") mechanisms play an essential role in the catalytic process of Cu-SAPO-34@Fe-MOR, and constitute another reason for its higher activity compared with that of Cu-SAPO-34 (only "L-H" mechanism).
在本研究中，通过硅溶胶粘附法成功制备了Cu-SAPO-34@Fe-MOR核壳催化剂，并详细评估了其对NH₃选择性催化还原NO（NH₃-SCR）的性能。Fe-MOR涂层不仅在很大程度上提高了高温活性并拓宽了Cu-SAPO-34的反应温度窗口，还显著提高了Cu-SAPO-34的水热稳定性。结果表明，Cu和Fe离子之间存在强烈的协同相互作用，促进了铜离子的氧化还原循环和氧化还原能力，大大加速了核壳Cu-SAPO-34@Fe-MOR催化剂的催化性能。离子交换位点上大量孤立的Cu离子和Fe离子在低温和高温区域进行NO还原，导致Cu-SAPO-34@Fe-MOR具有较宽的反应温度窗口。此外，形成的更多弱吸附NO物种和增加的路易斯酸位点数量也可能有助于提高Cu-SAPO-34@Fe-MOR的催化性能。另一方面，Cu-SAPO-34@Fe-MOR更好的水热老化稳定性与其较轻的结构坍塌、较少的酸性位点损失、更多的活性组分（Cu和Fe）保留以及水热老化后核壳催化剂中形成更多的单齿硝酸盐物种有关。最后，机理研究发现，Langmuir-Hinshelwood（“L-H”）和Eley-Rideal（“E-R”）机理在Cu-SAPO-34@Fe-MOR的催化过程中都起着至关重要的作用，这也是其比Cu-SAPO-34（仅“L-H”机理）具有更高活性的另一个原因。
