The ammonia selective catalytic reduction activity of copper-exchanged small-pore zeolites

Environmentally-benign catalysts for the selective catalytic reduction of NOxfrom diesel engines: structure–activity relationship and reaction mechanism aspects

“…Fickel et al 142 considered that the excellent hydrothermal stability of Cu-SSZ-13 and Cu-SAPO-34 catalysts was mainly due to the unique structure of CHA zeolites containing eight-memberedring pores with small pore size (0.38 Â 0.38 nm). For example, the 27 Al-NMR results by Kwak et al 140 showed that the hydrothermally treated Cu-SSZ-13 catalyst showed no noticeable change in the peak intensity of AlO 4 species compared with the fresh catalyst; however, the peak intensity of AlO 4 species in Cu-ZSM-5 and Cu-beta catalysts decreased ca.…”

“…The small pore structure in Cu-CHA catalysts was also expected to be more resistant to HC poisoning due to the difficulty in diffusion of HC with larger size, such as isobutane, with a kinetic diameter of 5.5 Å. 142 Using a variable-temperature XRD method, Fickel and Lobo 144 proved that the ion-exchange of Cu species into NH 4 -SSZ-13 could greatly enhance its thermal stability. Through a comprehensive study using Rietveld refinement of the XRD data, in situ UV-Vis and XAFS techniques, Fickel and Lobo, 144 Korhonen et al 145 and Deka et al 146 finally concluded that only the isolated Cu 2+ species located in the six-membered-rings of CHA structure coordinating with three oxygen atoms was the real active species in the NH 3 -SCR reaction (Scheme 4).…”

Prospective Catalytic Structured Converters for NH3-SCR of NOx from Biogas Stationary Engines: In Situ Template-Free Synthesis of ZSM-5 Cu Exchanged Catalysts on Steel Carriers

“…Low hydrothermal stability of majority of zeolites is claimed to be surpassed by the process of ultra-stabilization which was discovered for Y zeolite and also investigated in our previous paper for Cu-USY [11]. Recently small pore size zeolite-SSZ-13 of chabazite (CHA) structure has received a lot of attention due to its high hydrothermal stability, high activity in SCR and high selectivity to N 2 [12,13]. Also, the catalyst producers has begun to offer zeolitic catalyst designed for higher temperature operation window than the classic vanadia based SCR catalysts.…”

A novel one-pot synthesized CuCe-SAPO-34 catalyst with high NH3-SCR activity and H2O resistance

“…Copper-containing small-pore zeolites such as Cu-SAPO-34 and Cu-SSZ-13 have been attracting increasing attention as superior NH 3 -SCR catalysts [1][2][3][4][5][6]. The Cu-SAPO-34 catalyst showed excellent SCR activity over a wide range of temperature and quite outstanding hydrothermal stability at high temperatures [7][8][9].…”