Nature of Cu Species in Cu–SAPO-18 Catalyst for NH₃–SCR: Combination of Experiments and DFT Calculations

Abstract

A series of Cu–SAPO-18 catalysts with various Cu loadings were prepared and their catalytic activities were tested for the selective catalytic reduction of NO with NH3. The catalysts were characterized by means of XRD, N2 adsorption–desorption, TEM, XPS, UV–vis DRS, H2-TPR, NH3-TPD and EPR. Isolated Cu2+ ions are confirmed to be the catalytic active sites. Cu-4.42 catalyst exhibits high NO conversion (>80%) at the lowest temperature of 200 °C among all catalysts. It can be attributed to the maximum amount of isolated Cu2+ ions in Cu-4.42 catalyst. DFT calculations show that the isolated Cu ions are located in the pear shaped cavity and exhibit a preference for the neighboring of 6R planes of Cu–SAPO-18. NH3–SCR mechanism over Cu–SAPO-18 catalyst is elucidated by a combination of in situ DRIFTS technique and DFT calculations, in which the dissociation of NH3 and the oxidation of NO are shown to be key steps in the reaction.

Effects of Lanthanide Doping on the Catalytic Activity and Hydrothermal Stability of Cu-SAPO-18 for the Catalytic Removal of NOx (NH3-SCR) from Diesel Engines

“…As a solid sample, frequency of the OH stretching vibration is in the range of 3500−3300 cm −1 , while those after NH 3 adsorption appeared at 3600, 3625 and 3671 cm −1 . It shows that position of the peak really was shifted due to the interaction of NH 3 , which was consistent with the results reported by Y. Li et al [39]. Additionally, the bands at 3000−3400 cm −1 were attributed to the N−H bonds [30].…”

Zeolitic Materials for DeNOx Selective Catalytic Reduction

“…Our group reported that Cu‐SAPO‐44 exhibits excellent activity and N 2 selectivity over the wide temperature window from 200 to 550 °C . Because of the similar double six‐ring (D6R) structure in AEI and CHA zeolites, AEI‐type Cu‐SSZ‐39, Fe‐SSZ‐39, and Cu‐SAPO‐18 zeolites have been developed and exhibit excellent low‐temperature activity and high hydrothermal stability. Picone et al.…”

Deactivation and Regeneration for the SO2-Poisoning of a Cu-SSZ-13 Catalyst in the NH3-SCR Reaction

“…Figure 5a shows the XPS spectra of Cu 2p bands of the catalysts. According to literature [21,29,30], the Cu 2p 3/2 and Cu 2p 1/2 peaks ascribed to Cu 2+ appeared at about 933.3 and 955.5 eV, with two shakeup satellite peaks located at about 939.9 and 944.7 eV, while peaks assigned to Cu + species were located at about 932.4 and 952.6 eV. Furthermore, the peak at around 938.3 eV pertained to Cu 2+ in CuO, and the one at 944.1 eV represented the existence of dispersed Cu 2+ species on the surface.…”