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

Abstract

The NH3-SCR activities and hydrothermal stabilities of five xCu/MCM-22 zeolites with different Cu loadings (x = 2–10 wt%) prepared by incipient wetness impregnation method were systematically investigated. The physicochemical properties of xCu/MCM-22 zeolites were analyzed by XRD, nitrogen physisorption, ICP-AES, SEM, NH3-TPD, UV-vis, H2-TPR and XPS experiments. The Cu species existing in xCu/MCM-22 are mainly isolated Cu2+, CuOx and unreducible copper species. The concentrations of both isolated Cu2+ and CuOx species in xCu/MCM-22 increase with Cu contents, but the increment of CuOx species is more distinct, especially in high Cu loadings (>4 wt%). NH3-SCR experimental results demonstrated that the activity of xCu/MCM-22 is sensitive to Cu content at low Cu loadings (≤4 wt%). When the Cu loading exceeds 4 wt%, the NH3-SCR activity of xCu/MCM-22 is irrelevant to Cu content due to the severe pore blockage effects caused by aggregated CuOx species. Among the five xCu/MCM-22 zeolites, 4Cu/MCM-22 with moderate Cu content has the best NH3-SCR performance, which displays higher than 80% NOx conversions in a wide temperature window (160–430 °C). Furthermore, the hydrothermal aging experiments (xCu/MCM-22 was treated at 750 °C for 10 h under 10% water vapor atmosphere) illustrated that all the xCu/MCM-22 zeolites exhibit high hydrothermal stability in NH3-SCR reactions.

Modified Layered Silicas as Catalysts for Conversion of Nitrogen Pollutants in Flue Gases—A Review

“…For the delaminated zeolite, ITQ-6, containing copper in highly dispersed from, the NO conversion above the level of 90% was achieved in the range of 275-425 • C (Figure 7), while for the silica-intercalated zeolite, ITQ-36, which was also doped with highly dispersed copper species, this was achieved in the range of 300-425 • C [7]. Thus, the results were slightly different from those obtained for MCM-22 and its delaminated and intercalated forms modified with copper [80], which effectively operated in a broader temperature range compared to the catalysts of ITQ-6 and ITQ-36 series modified with copper [7]. This could be related to the differences in the porous structures of the zeolite materials, especially zeolite layers, however possibly the surface acidity of the zeolitic samples, related to the Si/Al ratio, is a more important factor.…”

“…MCM-22 zeolites modified with copper were reported to be very effective catalysts of low-temperature NH 3 -SCR [80]. A series of catalysts were prepared via deposition of various amounts of copper on MCM-22 (Si/Al = 15) through incipient wetness impregnation.…”

High-Dispersed V2O5-CuOX Nanoparticles on h-BN in NH3-SCR and NH3-SCO Performance

“…This result was consistent with the XPS data, and it su ported the notion that the formation of Cu + species might contribute to oxidation of NH The NH3-TPD and H2-TPR profiles were obtained in the temperature range 100-800 and the results were shown in Figure 4. Adsorption capacity (acid point, strength, a amount) for NH3 is one of the most critical factors in the SCR reaction [55,56]. NH3 adsorb on the catalyst surface is converted to active-NH3 (i.e., absorbed-NH3 and NH4 + ) and th volatilized as nitrogen oxides.…”

A review on the characterization of metal active sites over Cu-based and Fe-based zeolites for NH3-SCR

“…12 In order to suppress the occurrence of side reactions so as to investigate the detailed reaction pathway of NH 3 -SCR, the total metal loadings in Cubased or Fe-based zeolites are usually lower than 5 wt%, normally at about 2 wt%, to suppress the formation of undesired highly aggregated metal oxides or nanoparticles. 13,34,35 This poses a problem that, the qualitative and quantitative determination of various metal species over zeolites became difficult due to their low content and high dispersion over zeolites. Therefore, the detailed study on the type, content and distribution of active metal species in metal-based zeolites and their catalytic roles in NH 3 -SCR with advanced characterization methods are necessary for a better understanding of NH 3 -SCR reaction mechanism.…”