Catalytic Performance of One-Pot Synthesized Fe-MWW Layered Zeolites (MCM-22, MCM-36, and ITQ-2) in Selective Catalytic Reduction of Nitrogen Oxides with Ammonia

Abstract

The application of layered zeolites of MWW topology in environmental catalysis has attracted growing attention in recent years; however, only a few studies have explored their performance in selective catalytic reduction with ammonia (NH3-SCR). Thus, our work describes, for the first time, the one-pot synthesis of Fe-modified NH3-SCR catalysts supported on MCM-22, MCM-36, and ITQ-2. The calculated chemical composition of the materials was Si/Al of 30 and 5 wt.% of Fe. The reported results indicated a correlation between the arrangement of MWW layers and the form of iron in the zeolitic structure. We have observed that one-pot synthesis resulted in high dispersion of Fe3+ sites, which significantly enhanced low-temperature activity and prevented N2O generation during the reaction. All of the investigated samples exhibited almost 100% NO conversion at 250 °C. The most satisfactory activity was exhibited by Fe-modified MCM-36, since 50% of NO reduction was obtained at 150 °C for this catalyst. This effect can be explained by the abundance of isolated Fe3+ species, which are active in low-temperature NH3-SCR. Additionally, SiO2 pillars present in MCM-36 provided an additional surface for the deposition of the active phase.

Synthesis, Characterization, and NH3-SCR Catalytic Performance of Fe-Modified MCM-36 Intercalated with Various Pillars

“…Another significant modification of MCM-22P, patented by Corma et al [ 8 ], involves its swelling with centyltrimethylammonium bromide (CTABr), followed by delamination to yield ITQ-2. The structure of the material can be formed using single 2.5 nm-thick MWW layers, organized in a characteristic “house of cards” arrangement [ 9 ].…”

“…Rutkowska et al [ 5 ] reported that MCM-36 modified with copper by ion-exchange exhibited almost a 100% NO conversion within 230–530 °C. Moreover, in our previous study [ 9 ], we compared the catalytic performances of one-pot synthesized Fe-MCM-22, Fe-MCM-36, and Fe-ITQ-2. Based on our research, we concluded that Fe-MCM-36 showed the superior potential as the catalyst for NO reduction, especially due to the presence of SiO 2 pillars, which contributed to the formation of new acid centers and towards the well-developed texture of the catalyst.…”

“…However, morphological similarities between these two groups of materials led to the conclusion that MCM-36 can be intercalated with the same pillars as the natural clays, e.g., Fe, Ti, Zr, and Al [ 30 , 31 , 32 , 33 ]. Taking into account the exceptional NH 3 -SCR catalytic performance of iron-modified zeolites, which have been documented widely in the literature [ 9 , 34 , 35 ], the introduction of Fe 2 O 3 as the pillaring component seems to be an interesting idea to obtain an MCM-36-supported catalyst. What is more, so far, there are no reports in the literature on the introduction of iron oxide simultaneously with other pillars into the interlayer space of MCM-36.…”

Physicochemical Features and NH3-SCR Catalytic Performance of Natural Zeolite Modified with Iron—The Effect of Fe Loading

“…4, its well-developed pore system, and its thermal stability. According to the Eley-Rideal mechanism, NH 3 -SCR assumes simultaneous adsorption of alkaline NH 3 and neutral NO and their interaction on the catalyst surface [12]. Therefore, high concentration of acid centers delivered by clinoptilolite improves ammonia adsorption capacity and NH 3 -SCR reaction rate.…”

“…Another important issue in the design of a novel NH 3 -SCR catalyst is the active phase. Over recent years, the focus of researchers has shifted to systems with transition metals, especially iron [5,12,19,20]. The choice of Fe was motivated by its environmentally benign characteristics, low price, and prominent thermal stability.…”