One‐pot synthesis of Cu/SAPO‐34 with hierarchical pore using cupric citrate as a copper source for excellent NH₃‐SCR of NO performance

Abstract

It is still a serious challenge to develop a simple synthesized method of SAPO-34 sieve modified by Cu with high NH 3-SCR performance. The Cu/SAPO-34 samples with hierarchical structure were synthesized for the first time using cupric citrate as copper source by one-pot hydrothermal method which showed excellent NH 3-SCR performance for NO removal. Among them, the 0.15Cu/SAPO-34 catalyst with a Cu/Al ratio of 0.15 exhibited the widest temperature operating window (160-500°C) and better hydrothermal stability. The physicochemical properties of 0.15Cu/SAPO-34 was measured to understand the impacts of the Cu species on the NH 3-SCR of NO activity by various characterization methods including XRD, NH 3-TPD, N 2 adsorption-desorption, XPS, EPR, UV-vis, NH 3-oxidation, NMR and in situ DRIFTS. The results reveal that the good activity is assigned to the isolated Cu species located at the site (I) in SAPO-34, and the coexistence of surface Cu 2 + and Cu + species with almost equal amounts. In addition, 0.15Cu/SAPO-34 also possesses suitable acidic sites which are conducive to catalytic activity. The results of in situ DRIFTS suggest that the NH 3-SCR reaction follows Eley-Rideal mechanism over 0.15Cu/SAPO-34.

Rare‐earth Yttrium Exchanged Cu‐SSZ‐39 Zeolite with Superior Hydrothermal Stability and SO2‐Tolerance in NH3‐SCR of NOx

“…Hydrothermal stability and SO 2 ‐tolerance are the most important properties for Cu/zeolites used as catalytic converters for the reduction of NO x gases [7a,21] . Our results show that the addition of Y ions enhances the hydrothermal stability and SO 2 ‐tolerance of Cu/zeolites simultaneously, and this enhancement is further dramatically in Cu‐Y‐AEI than in Cu‐Y‐CHA (Figure S7).…”

One‐pot facile synthesis of Cu‐SAPO‐34 via addition of tetraethylenepentamine and its enhanced catalytic activity in selective catalytic reduction of NOx with NH3

“…Moreover, the amount of surface copper for Cu‐SAPO‐34‐TC is about 2.91 wt%, as presented in the supporting information (Table S3), which is larger than that for Cu‐SAPO‐34‐C (about 1.97 wt%). These results indicate the addition of TEPA can enhance the loading amount of surface copper and the formation of more isolated Cu 2+ in the Cu‐SAPO‐34‐TC sample, leading to its good catalytic performance in NH 3 ‐SCR 16,17 …”

“…34‐0137) though the diffraction peaks for these Cu‐SAPO‐34 samples show a slight shift when compared with pure SAPO‐34 due to the crystal distortion caused by the introduction of copper ions. Meanwhile, no obvious diffraction peak of CuO or Cu 2 O can be observed from the XRD results, suggesting that copper was either well dispersed or existed as isolated species 17 . This result reveals that the addition of TEPA really can modify the distribution of copper species in the SAPO‐34 sample and this effect is not dependent on the copper source used.…”

“…1(B) (inset), EPR signal at g // = 2.38 for Cu‐SAPO‐34‐C demonstrates that the isolated Cu 2+ species is in Site (III), the center of the hexagonal prism 21 . Meanwhile, EPR signal at g // = 2.32 for Cu‐SAPO‐34‐TC indicates that the isolated Cu 2+ species exist in the junction of the CHA cage and D6R Site (I), which is regarded as a more easily approachable site for the adsorbates (NH 3 and NO) than others, thus leading to the excellent NH 3 ‐SCR performance of Cu‐SAPO‐34‐TC 17 . In addition, there are also some differences in the 29 Si NMR spectra and NH 3 ‐TPD results for these two samples.…”

“…As mentioned above, it is still a challenge to develop a simple approach to synthesize Cu‐modified SAPO‐34 with outstanding NH 3 ‐SCR performance and high hydrothermal stability. In our previous work, series of Cu‐SAPO‐34 with hierarchical pore structure were synthesized by the ion‐exchange method and one‐pot method 16,17 . Although the obtained catalysts showed better NH 3 ‐SCR performance, the complex repeated ion‐exchange process and low yield of the product are still challenges that need to be considered.…”