Rational Design of Mesoporous CuO–CeO₂ Catalysts for NH₃-SCR Applications Guided by Multiple In Situ Spectroscopies

Abstract

Efficient nontoxic catalysts for low-temperature NH3 selective catalytic reduction (NH3-SCR) applications are of great interest. Owing to their promising redox and low-temperature activity, we prepared CuO–CeO2 catalysts on a mesoporous SBA-15 support using targeted solid-state impregnation (SSI), guided by multiple in situ spectroscopy. The use of template P123 allowed dedicated modification of the surface properties of the SBA-15 matrix, resulting in a changed reactivity behavior of the metal precursors during the calcination process. To unravel the details of the transformation of the precursors to the final catalyst material, we applied in situ diffuse reflectance infrared Fourier transform (DRIFT), UV–visible (UV–vis), and Raman spectroscopies as well as online Fourier transform infrared (FTIR) monitoring of the gas-phase composition, in addition to ex situ surface, porosity, and structural analysis. The in situ analysis reveals two types of nitrate decomposition mechanisms: a nitrate-bridging route leading to the formation of a CuO–CeO2 solid solution with increased low-temperature NH3-SCR activity, and a hydrolysis route, which facilitates the formation of binary oxides CuO + CeO2 showing activity over a broader temperature window peaking at higher temperatures. Our findings demonstrate that a detailed understanding of catalytic performance requires a profound knowledge of the calcination step and that the use of in situ analysis facilitates the rational design of catalytic properties.

Highly electron-deficient ultrathin Co nanosheets supported on mesoporous Cr2O3 for catalytic hydrogen evolution from ammonia borane

“…It can be clearly found that the weight loss of complete decomposition for the mixed component of KIT-6 and Cr(NO 3 ) 3 is 448.8 °C, which is slightly higher than that of pure Cr(NO 3 ) 3 (421.1 °C), attributed to the support effect that can inhibit the nitrate salt decomposition. 36 In addition, the band from 200 to 260.1 °C for mesoporous Cr 2 O 3 is attributed to the removal temperature of KIT-6. This result suggests that the introduction of KIT-6 can largely affect the structure Cr 2 O 3 .…”

Studies of NO Reduction with Ammonia Over Copper Species Deposited on MCM‐41 Nanospheres ‐ Experimental Evidence of Reaction Mechanism

“…Low-temperature activity in the NH 3 -SCR has been reported for various catalyst systems, including char-based materials [5,6,7] and zeolites modified with transition metals. [8,9,10] To transition metals catalytically active in the low-temperature reduction of nitrogen oxides belong, among others, copper [9,11,12] and manganese, [13,14,15] used as main catalytically active components or in combinations with other metals, e. g., Cu-Fe, [16] Cu-Ce, [17] Mn-Ce, [18] Mn-Co. [19] Catalytic performance of the NH 3 -SCR catalysts strongly depends on the form and aggregation of catalytically active transition metal species as well as properties of the used catalytic support, such as surface acidity [20] or porosity. [21] Recently, a very promising catalytic performance in the lowtemperature NH 3 -SCR process has been reported for copper modified mesoporous silicas obtained by template ion-exchange (TIE) method.…”