When Cu–TEPA (Cu2+ coordinated with tetraethylenepentamine) is used as a template in the one-pot synthesis of Cu–SSZ-13, Cu2+ will be reduced to Cu0, resulting in a too high Cu content in the product. Herein, by adding iron complexes to the precursor, the reduction of Cu2+ could be inhibited and FeCu–SSZ-13 samples with rational Cu and Fe contents were prepared by a simple one-pot strategy. Although these samples show high activity in the NH3-SCR at low temperature, their high temperature performance is poor due to the lack of strong NH3 adsorption sites such as Brønsted acid sites. Meanwhile, different iron complexes were used as iron sources to synthesize FeCu–SSZ-13, and among them the sample with sodium nitroprusside shows the highest activity. Due to the large ionic radius of K+, it is easily retained which blocks the pores, so the performance of the samples synthesized with a K-type iron source is poorer than that of their Na-type counterparts. Moreover, the activity of the catalyst synthesized with an Fe3+ source is higher than that synthesized with an Fe2+ source because the valence state of Fe sources has a great influence on the Fe chemical state in the catalysts.
For traditional strategies to construct SO 2 and H 2 O co-resistant systems in low-temperature NH 3 selective catalytic reduction (NH 3 -SCR) catalysts, the primary challenge lies in mitigating the partial loss of redox activity at active sites. Herein, we present an approach to construct a protective system based on interface engineering principles, effectively safeguarding Cu active sites in ZnO/FeCu-SSZ-13 under SO 2 and H 2 O exposure. The core innovation stems from the creation of a strong interface effect originated from Zn-O-Al bonds formed between ZnO and the framework Al on the FeCu-SSZ-13 surface. This interface effect can regulate the electronic structure of Zn O bonds on ZnO component, producing abundant basic sites around the Cu active sites, enabling the preferential adsorption of SO 2 and its oxidation into ZnSO 4 , thereby virtually eliminating the redox ability loss of Cu active sites. As a result, ZnO/FeCu-SSZ-13 achieves exceptional low-temperature NH 3 -SCR performance, maintaining over 90 % NO x conversion even in the presence of SO 2 and H 2 O. Our work opens a new avenue for developing low-temperature NH 3 -SCR catalysts with desired SO 2 and H 2 O resistance, offering valuable insights for advancing catalytic performance in challenging reaction conditions.
Lin Zheguan,Cao Wanying,Cui Qingyan,Li Tiesen,Bao Xiaojun,Fu Xianzhi,Yue Yuanyuan
Water-induced deactivation of catalysts
under low-temperature
and
high-humidity conditions remains a major challenge for the practical
application of NH 3 -selective catalytic reduction (NH 3 -SCR) technology. Herein, a dynamic Brønsted acid site
compensation strategy based on the heterolytic dissociation of H 2 O is proposed to improve the water tolerance of Cu-based chabazite
catalysts. Following this strategy, a Co-WO 3 /FeCu-SSZ-13
catalyst was rationally designed. Co doping effectively modulates
the d-band center of WO 3 , enabling heterolytic H 2 O dissociation and the in situ generation of hydroxyl
groups that act as Brønsted acid sites, thereby significantly
enhancing NH 3 adsorption and activation. Simultaneously,
preferential utilization of H 2 O for Brønsted acid
site compensation mitigates its competitive occupation of the intrinsic
metal active sites in FeCu-SSZ-13, preserving the NO oxidation pathway
under high-humidity conditions. Therefore, this synergistic regulation
of dynamic compensation of Brønsted acid sites and the release
of active metal sites enables Co-WO 3 /FeCu-SSZ-13 to achieve
a NO x conversion exceeding 90% at 165
° C in the presence of 20 vol % H 2 O. This work highlights
the dual role of H 2 O in simultaneously regulating the acid
and redox cycles, offering a general strategy for designing water-tolerant
NH 3 -SCR catalyst.
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