Titanium–silicon ferrierites and their delaminated forms modified with copper as effective catalysts for low-temperature NH₃-SCR

Abstract

Titanium–silicon ferrierites with different Si/Ti ratios and their delaminated forms were modified with copper by ion-exchange.

Modified Layered Silicas as Catalysts for Conversion of Nitrogen Pollutants in Flue Gases—A Review

“…Thus, the acid sites in Ti-FER and Ti-ITQ-6 are possibly not strong enough to chemisorb ammonia molecules and protect them against direct oxidation by oxygen present in the reaction mixture. Thus, the conclusions from these studies [34] are in line with the results obtained for the aluminumsilicon zeolites [7]. Results of NH3-SCR catalytic tests for aluminum-silicon (FER) and titanium-silicon (Ti-FER) ferrierites and their delaminated forms, ITQ-6 and Ti-ITQ-6, respectively, modified with copper via ion exchange method.…”

“…It should be noted that the copper-modified catalysts of the Ti-ITQ-6 series effectively operated at lower temperatures [76] than catalysts based on aluminumsilicon ITQ-6 [7], and therefore seem to be very promising as catalysts for the low-temperature NH3-SCR process. On the other hand, the side reaction of direct ammonia in the presence of copper-modified titanium-silicon zeolites started at temperatures significantly lower than in the cases of the copper doped aluminum-silicon zeolites [7,34]. The titanium-silicon zeolites, as shown by NH3-TPD analyses, are characterized by weaker acid sites than analogues of aluminum-silicon zeolites.…”

“…Extra-framework cations, compensating for the negative charge of the zeolite framework, can be relatively easily exchanged for other cations, and therefore this property may be used for the introduction of catalytically active metal cations into zeolites. Moreover, due to the presence of aluminum or some other cations, e.g., Fe 3+ [33] or Ti 4+ [34], zeolites are characterized by the presence of acid sites. Thus, considering their uniform porous structure with pore sizes similar to the sizes of small molecules, the surface acidity, ion exchange properties, as well as the relatively high thermal and hydrothermal stability of zeolites make them very promising materials for catalytic applications [5].…”

“…Swięs et al [7,34] reported very interesting catalytic properties of ferrites (FER) and their delaminated and intercalated forms, which were modified with copper via ion exchange method. The studies were focused on the determination of the role of the porous structure and Si/Al framework ratio in their catalytic performance in the NH 3 -SCR process [7].…”

“…Values in brackets are intended molar Si/Al or Si/Ti ratios in the zeolite framework. Based on the results presented in [7,34] with permission from ref. [34].…”