Functionalization of SSZ-13 and Fe-Beta with Copper by NH3 and NO Facilitated Solid-State Ion-Exchange

Abstract

Abstract:We show that functionalization of SSZ-13 (CHA) and Fe-beta (*BEA) with copper using a recently reported solid-state ion-exchange method, facilitated by NH 3 and nitrogen oxides (NO), is a viable route to prepare Cu-SSZ-13 and (Cu + Fe)-beta catalysts, starting from H-SSZ-13 and Fe-beta, respectively. The physicochemical properties of the prepared catalysts are characterized by XRD, UV-Vis-spectroscopy and STEM-EDS, confirming that copper originally present in the physical mixture of CuO and H-SSZ-13, and CuO and Fe-beta, is inserted into the micropores of SSZ-13 and Fe-beta, respectively. Activity measurements in gas-flow reactor show that the samples are active for NO reduction by NH 3 -SCR over a broad temperature range, i.e., 150-500 • C. For the Cu-SSZ-13 catalysts, which have a copper loading range of 0.5-4 wt. %, the sample prepared from the physical mixture with a CuO/SSZ-13 ratio corresponding to 2 wt. % Cu is the most active catalyst for NH 3 -SCR under the present reaction conditions. Furthermore, the (Cu + Fe)-beta catalyst shows higher NH 3 -SCR activity over a broader temperature range and especially at low temperature as compared to the Fe-beta and Cu-beta counterparts. The results encourage further elaboration on sequential ion-exchange procedures for bimetallic functionalization of zeolites.

Selective catalytic reduction of NOx over Cu- and Fe-exchanged zeolites and their mechanical mixture

“…Despite different reaction conditions, the SCR-NH3 performance of combined (2%)Cu-(2%)Fe-BEA catalyst prepared by solid ion-exchange method ([NH3+NO] SSIE) [14] is similar to our results. Contrary to the results obtained by using the dual-layer samples [10], the activity of the studied mechanical mixture is not decreased by diffusion limitation.…”

“…This suggests a synergistic effect between Cu and Fe metals in the mixed catalysts resulting in higher SCR-NH3 (when NOx/NH3 = 1.3) in a wider temperature range. In addition, it was recently shown that the copper of CuO species becomes mobile in the presence of NH3 and NO at medium temperatures (250-350 °C), resulting in the migration of Cu species [14,39]. Based on this feature, several composite (Cu+Fe)-zeolite catalysts were prepared starting from the physical mixture of CuO and Fe-exchanged zeolites under NO and NH3 [39].…”

“…Given the difference in activities of Feand Cu-zeolites, it seems plausible that a combination of the two catalysts might achieve higher NOx conversions over a broader temperature range. Such combined Fe-and Cuzeolite systems were thoroughly investigated in the literature [10,11,12,13,14]. Mektar et al [10] showed that the Fe-ZSM-5 and Cu-Chabazite dual layer catalyst exhibited excellent NOx reduction efficiency over the entire temperature range of 250-550 °C.…”

“…Other studies showed improvements in NO conversion over zeolites containing simultaneously copper and iron cations [11,12,13,14]. These catalysts were prepared by different methods such as one-pot aqueous ion-exchanged method (AIE) [12,13], solid state ion-exchange method (SSIE) [14], two-step post synthesis and conventional wet impregnation procedure [11]. These methods, however, present several drawbacks.…”

Surface Species and Metal Oxidation State during H2-Assisted NH3-SCR of NOx over Alumina-Supported Silver and Indium

“…Among the most attractive exhaust aftertreatment techniques for lean NO x reduction is the selective catalytic reduction with either ammonia (NH 3 -SCR) or hydrocarbons (HC-SCR). For example, Cu-based zeolites have recently been shown to exhibit high NO x removal activity in a wide temperature range [1][2][3]. In contrast to NH 3 -SCR, the HC-SCR catalysts need to be further improved as to be competitive.…”