The Cu migration of Cu-SAPO-34 catalyst for ammonia selective catalytic reduction of NOx during high temperature hydrothermal aging treatment

Abstract

Two kinds of Cu-SAPO-34 catalysts, prepared with a one-pot technique using Cutetraethylenepentamine as co-template and an ion-exchange method, were hydrothermally treated at 750 o C for at least 16 h. The migration of Cu species during hydrothermal treatment and the corresponding effect on the selective catalytic reduction (SCR) of NOx were examined and characterized. A certain amount of CuO exists outside and inner the crystallites in the as prepared ion-exchanged sample, whereas copper is mainly atomically dispersed in the one-pot sample existing as isolated Cu 2+ .After hydrothermal treatment for 16 h, the amount of the inner nanosized CuO in the ion-exchanged sample reduced and the copper disperses to form more isolated Cu 2+ . However, surface CuO particles increase at the sacrifice of isolated Cu 2+ with extending the hydrothermal treatment to 24 h. Aggregation of Cu 2+ species also happens during the aging treatment over the one-pot prepared sample where the initial Cu is atomically

Catalytic Performances of Cu/MCM-22 Zeolites with Different Cu Loadings in NH3-SCR

“…The In comparison with 2Cu/MCM-22, the NOx conversion of 2Cu/MCM-22-aged at 100-200 °C significantly increased, as shown in Figure 9A. According to the literature [74][75][76][77], some of CuOx species (with low activity in NH3-SCR) on the surface of Cu-SAPO-34 may migrate into the ionexchange sites of SAPO-34 zeolite to form active isolated Cu 2+ species during the hydrothermal aging process, thereby causing an increase of NH3-SCR activity for Cu-SAPO-34 after hydrothermal aging. This may be one of the reasons for the enhanced activity of 2Cu/MCM-22 in NH3-SCR after hydrothermal aging.…”

Novel Cu-Based CHA/AFI Hybrid Crystal Structure Catalysts Synthesized for NH3-SCR

“…The results of NH 3 -SCR activity are depicted in Figure A. Except for Cu/SAPO-5 and Cu/SAPO-34/5(0.19), the almost same high-temperature (above 350 °C) activities could be due to the similar NH 3 oxidation capacities of other samples. , However, the low-temperature (150–350 °C) deNO x performances differ obviously over these catalysts and vary basically following this sequence: Cu/SAPO-34/5(3.16) > Cu/SAPO-34/5(1.44) ≈ Cu/SAPO-34 ≈ Cu/SAPO-34/5(0.61) > Cu/SAPO-34/5(0.19) > Cu/SAPO-5. When the ratio of SAPO-34/5 is close to about 1 [including Cu/SAPO-34/5(1.44) and Cu/SAPO-34/5(0.61)], the NH 3 -SCR activities are similar to that of Cu/SAPO-34.…”

Low-Temperature Solid-State Ion-Exchange Method for Preparing Cu-SSZ-13 Selective Catalytic Reduction Catalyst

“…Another key point is that the precursors should be well dispersed over In the present work the impregnation method is employed. Otherwise, surface CuO species are formed which are adverse for SCR 55 (Figures 1b and 8b for CuAc 2 and Figure S3a and S11b for Cu(NO 3 ) 2 ) if just mixing the copper salts with the zeolite mechanically followed by the same calcination process.…”