Interface Engineering of a Bifunctional Cu-SSZ-13@CZO Core–Shell Catalyst for Boosting Potassium Ion and SO₂ Tolerance

Abstract

The poisoning of sulfur oxides and alkali metals emitted from diesel exhaust to active sites of copper ion-exchanged chabazite (Cu-CHA) catalysts is still present and remains a formidable challenge in practical application. Herein, a bifunctional core−shell structural Cu-SSZ-13@Ce 0.75 Zr 0.25 O 2 (Cu-SSZ-13@CZO) catalyst was designed and fabricated via a hydrothermally induced self-assembly protocol, and the catalytic activity of Cu-SSZ-13@ CZO for selective catalytic reduction (SCR) of nitrogen oxides (NO x ) with ammonia was systematically investigated. It unveils that Cu-SSZ-13@CZO features Cu-SSZ-13 as the core and dispersed CZO as the shell and that the CZO shell could not only serve as a sacrificial site protecting the Cu-SSZ-13 active core from SO 2 poisoning by the formation of Ce 2 (SO 4 ) 3 , which could further act as adsorption sites capturing the K + through the strong interaction between K + and cerium sulfate, but also render additional Brønsted acid sites functioning as sacrificial sites to trap K + , thereafter inhibiting the adsorption of K + directly on active Cu species in the Cu-SSZ-13 core. As a result, the as-constructed Cu-SSZ-13@ CZO catalyst, therefore, exhibits perceptibly enhanced coresistance to sulfur and potassium ion poisoning with almost 100% NO x conversion in the temperature window of 275−475 °C as compared to 350−450 °C on pristine Cu-SSZ-13. The finding here may contribute to the fundamental understanding of the coresistance to sulfur oxides and alkali metal poison and thereafter inspire the advancement of a highly efficient NH 3 -SCR catalyst in the future.

Design, Synthesis, and Insights into the Redox Mechanism of Highly Efficient One-Pot Cu-ZSM-5 Catalysts for the Reduction of NOx by NH3-SCR at Low Temperatures

“…In situ DRIFT spectra and corresponding mapping were recorded for further analysis of [Cu­(OH)] + in 10-membered rings and Cu 2+ in 6-membered rings. According to the literature, two distinguished bands around 950 and 900 cm –1 are attributed to T–O–T asymmetric vibrations perturbed by [Cu­(OH)] + and Cu 2+ species for Cu-SSZ-13. − These two bands of zeolite framework vibrations are perturbed by Cu species in the neighborhood of the zeolite lattice, representing the solvation of two different types of Cu species with NH 3 , namely, [Cu­(OH)] + and Cu 2+ species, respectively . Similar phenomena also appear in Cu-SAPO-34 and Cu-SAPO-18, while the FTIR bands for [Cu­(OH)] + and Cu 2+ species are around 900 and 850 cm –1 .…”

One-Pot Three-Dimensional Printing of a Hierarchical NiMo/Al2O3 Monolithic Catalyst for 4,6-Dimethyldibenzothiophene Hydrodesulfurization

“…As NiMo/Al 2 O 3 was purged by 500 ppm NH 3 flow at 30 °C, five IR signals were observed in the range of 1000∼2000 cm –1 . Therein, the signals noted at 1278, 1622, and 1691 cm –1 correspond to the bending vibrations of N–H bonds in NH 3 coordinated to L acid sites, and the signals at 1454 and 1489 cm –1 are associated with the asymmetric bending vibration of N–H bonds in NH 4 + chemisorbed on B acid sites. , Note that relative larger ratio of L acid sites was present on NiMo/Al 2 O 3 and; however, B acid sites was predominated on 3D-NiMo/Al 2 O 3 . It indicates that the decrease of MSI on 3D-NiMo/Al 2 O 3 should be resulted from the reduced ratio of strong L acid sites and the increased B acid sites.…”

“…The relative ratio of these acid sites on catalyst surface was also calculated by peak fitting (as depicted in Figure 5B). Note that a significant higher ratio for weak acid and perceptible lower medium-strong and strong acid was observed on 3D-NiMo/Al 2 O 3 than that of NiMo/ Al 38,39 Note that relative larger ratio of L acid sites was present on NiMo/Al 2 O 3 and; however, B acid sites was predominated on 3D-NiMo/Al 2 O 3 . It indicates that the decrease of MSI on 3D-NiMo/Al 2 O 3 should be resulted from the reduced ratio of strong L acid sites and the increased B acid sites.…”

Tuning the Micro-coordination Environment of Al in Dealumination Y Zeolite to Enhance Electron Transfer at the Cu–Mn Oxides Interface for Highly Efficient Catalytic Ozonation of Toluene at Low Temperatures

“…Cu2p 3/2 and Cu2p 1/2 can be detected in the spectra of Cu 2p in Figure 4d, the binding energies at around 932.5 and 934.2 eV are assigned to Cu 1+ and Cu 2+ , respectively. 49,50 It can be observed that the content of Cu 1+ in Cu−Mn/Y was more than that in Cu−Mn/DY, which implies that the coordination state of CuOx is different for the two supports before and after dealumination. Figure 4f shows the spectra of Al 2p, the binding energy of Al increased in the catalysts with dealumination Y as the support, meaning that the electron cloud density around Al decreased.…”