期刊
CHEMICAL ENGINEERING JOURNAL
卷 379, 期 -, 页码 -出版社
ELSEVIER SCIENCE SA
DOI: 10.1016/j.cej.2019.122358
关键词
Cu/SSZ-13 catalyst; Synthesis method; NH3-SCR; Hydrothermal stability; Mechanism
资金
- National Key Research and Development Plan [2016YFC0205200, 2016YFC0208000]
- National Engineering Laboratory for Mobile Source Emission Control Technology [NELMS2017A07]
- National Natural Science Foundation of China [51676127, 51436005, 51176118, 51306115]
- Low Speed Marine Engine Project [CDGC01-KT1203]
- Scientific Research Foundation for the Returned Overseas Chinese Scholars of State Education Ministry
This study focuses on investigating the influence of ion-exchange method (ION-F and ION-A) and one-pot method (ONE-F and ONE-A) on catalytic properties and hydrothermal stability of Cu/SSZ-13. It was found that ONE-F catalyst showed better SCR activity, especially at low temperature range below 400 degrees C. After hydrothermal aging, ION-A exhibited higher low temperature efficiency than ONE-A. The effect of synthesis method on the physicochemical structure, acidity intensity, and Cu species migration or transformation of the fresh and aged Cu/SSZ-13 catalysts were comprehensively characterized by NH3-TPO, H-2-TPR, NH3-TPD, ICP, XRF, BET, XRD, SEM, and TEM. ONE-F has more isolated Cu2(+) sites, higher ratio of active sites Cu2+-2ZACu(OH)](+)-Z, more Lewis acid sites, and smaller particle size than ION-F. However, hydrothermal aging had severe effect on Cu/SSZ-13 prepared by one-pot method, leading to particle aggregation and decrease of active copper sites. According to NH3-SCR kinetic studies, smaller particle size and more uniformly distributed active sites over ONE-F resulted in less effect of pore diffusion limitation. Furthermore, in situ DRIFTS results indicated that more monodentate nitrates adsorbed sites and Lewis acid sites existed in ONE-F. On the other hand, monodentate nitrates were identified to be the most active nitrate species, and Lewis acid sites were ascertained to be more active than Bronsted acid sites. Therefore, ONE-F showed more excellent SCR performance than ION-F. However, hydrothermal aging resulted in loss of majority of nitrate adsorbed sites and acid sites over catalyst prepared by one-pot method, leading to lower SCR performance. In conclusion, Cu/SSZ-13 prepared by ion-exchange method has higher hydrothermal stability, however, fresh Cu/SSZ-13 prepared by one-pot method has excellent catalytic properties.
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