On the performance of Fe-Cu-ZSM-5 catalyst for the selective catalytic reduction of NO with NH3: the influence of preparation method

Abstract

The Selective Catalytic reduction of NO with ammonia (NH3-SCR) in the presence of H2O was studied over a series of Fe-Cu-ZSM-5 catalysts prepared by solid-state ion exchange (SSIE), aqueous ion exchange and dry impregnation methods. The prepared samples were characterized by a wide number of techniques (ICP-AES, N2 physisorption at 77 K, XRD, STEM-EDX, XPS, H2-TPR and DRS UV-vis) to investigate the effect of the preparation method on the activity, texture, structure and metal speciation of the studied catalysts. It was found that the aqueous ion exchange method induced a significant metal loss during the preparation procedure but without any activity deterioratation of the catalyst which encloses highly dispersed metal species. The catalysts prepared by SSIE and impregnation showed the highest metal contents and a large number of oxide aggregates leading to an activity decline at high reaction temperatures due to the ammonia oxidation phenomenon. Keywords Ion exchange. Impregnation . NO . NH3-SCR . Zeolite

Ce-promoted Fe–Cu–ZSM-5 catalyst: SCR-NO activity and hydrothermal stability

“…Above 480 °C the NO conversion of Ce-Fe-Cu-Z catalyst notably decreases in comparison with the unpromoted sample, such behaviour is explained by to the over-oxidation of NH 3 to NO, which is in perfect agreement with previous studies reporting that the addition of Ce increases the oxidation of NH 3 [19]. Other studies have proven that such reaction is promoted by the presence of large metal oxide particles, mainly CuO x [12]. In accordance with this and as observed in the STEM micrograph of Ce-Fe-Cu-Z, the degree of aggregation of Cu has increased, which explains the highest activity of the latter catalyst in the ammonia oxidation reaction.…”

“…Examination of ICP results shows that metals are well retained by the zeolite during the preparation process where the experimental amounts approximate the theoretical values set for the catalysts preparation. This result is expected since the SSIE is the most convenient method for controlling the metal amount in the prepared solids, which is in perfect agreement with our previous works [12][13][14]. The ratio of the parent zeolite stated by Zeolyst (CBV024E, Si/Al=15) was decreased in the case of prepared catalysts and that can be attributed to the reproducibility of routine sequential syntheses which may vary from batch to batch [30].…”

“…To be an interesting candidate for automotive Diesel applications, such catalyst must support the severe conditions of vehicle engine and show a high hydrothermal stability up to 800 °C [10][11][12][13][14]. Recently, Ce-based catalysts [15][16][17][18] have also received considerable attention for NO removal through the NH 3 -SCR process thanks to its single properties to combine elevated oxygen transport capacity and to shift easily between Ce 4+ /Ce 3+ reduced and oxidized states [19][20][21].…”

Alkali poisoning of Fe-Cu-ZSM-5 catalyst for the selective catalytic reduction of NO with NH3

“…Metal exchanged zeolite SCR catalysts, are among the most effective systems for nitrogen oxides (NOx) abatement from exhaust gases of Diesel engines and power plants providing reduction of NOx emissions up to 99% (Jouini et al 2019;Jouini et al 2018a, b). The durability of this category of catalysts dedicated to automotive applications regarding hydrothermal aging and chemical deactivation must be proven over the lifetime of the vehicle.…”

Theoretical Studies on the Mechanism of deNOx Process in Cu–Zn Bimetallic System—Comparison of FAU and MFI Zeolites

“…Research on bimetallic systems is also of considerable interest [ 32 , 33 , 34 , 35 ]. Such catalysts offer the possibility of taking separate advantage of the properties of each metal, which may influence each other to improve catalytic activity.…”