Aleksandra Gomułka

Prace badawcze dotyczyły opracowania katalizatorów procesu niskotemperaturowej redukcji tlenków azotu amoniakiem bazujących na wysokopowierzchniowych materiałach krzemionkowych. Mezoporowate krzemionki typu MCM-41 (Mobil Composition of Matter No. 41) oraz MCM-48 (Mobil Composition of Matter No. 48) dotowano miedzią metodą jonowej wymiany templatu (TIE) oraz metodą TIE rozszerzoną o etap dodawania do próbek dotowanych miedzią roztworu amoniaku. Rozszerzona procedura TIE pozwoliła na uzyskanie katalizatorów o podwyższonej zawartości miedzi w formie wysokorozproszonej w porównaniu do standardowej procedury TIE. Z drugiej strony działanie roztworu amoniaku na mezoporowate krzemionki powodowo częściową destrukcję ich uporządkowanej struktury porowatej. Katalizatory uzyskane metodą TIE, obejmującą używanie amoniaku, wykazywały bardzo dużą aktywność w procesie selektywnej katalitycznej redukcji tlenku azotu amoniakiem (NH3-SCR). Najbardziej obiecujący katalizator, uzyskany na bazie mezoporowatej krzemionki typu MCM-48 dotowanej miedzią metodą TIE, a następnie traktowany roztworem amoniaku, pozwalał na osiągnięcie konwersji NO na poziomie 90%, przy selektywności do azotu sięgającej 99% już w temperaturze około 200°C. Wyniki te lokują badane materiały w grupie najaktywniejszych układów katalitycznych dedykowanych dla niskotemperaturowego procesu NH3-SCR.

Mesoporous silicas of MCM-41 and MCM-48 types were synthesized and modified with copper using the ammonia-driven deposition precipitation (ADP) method, resulting in highly dispersed copper species. Samples with varying copper loadings were thoroughly characterized in terms of their porous structure, metal content, copper species’ aggregation, and the stability of deposited forms under reaction conditions. Copper-modified mesoporous silicas exhibited excellent catalytic performance in the low-temperature NH₃-SCR process. Their activity in NO to NO₂ oxidation suggests that the fast-SCR pathway plays a significant role in NO_x conversion at low temperatures. However, direct ammonia oxidation limited SCR efficiency at higher temperatures. These findings demonstrate the potential of ADP-modified copper–silica catalysts for effective and selective NO_x removal under low-temperature conditions.

Mesoporous silicas of MCM-41 and MCM-48 types were synthesized and modified with copper using the ammonia driven deposition precipitation (ADP) method, resulting in highly dispersed copper species. Samples with varying copper loadings were thoroughly characterized in terms of porous structure, metal content, copper species aggregation and the stability of deposited forms under reaction conditions. Copper-modified mesoporous silicas exhibited excellent catalytic performance in the low-temperature NH₃-SCR process. Their activity in NO to NO₂ oxidation suggests that the fast-SCR pathway plays a significant role in NOₓ conversion at low temperatures. However, direct ammonia oxidation limited SCR efficiency at higher temperatures. These findings demonstrate the potential of ADP-modified copper-silica catalysts for effective and selective NOₓ removal under low-temperature conditions.

Mesoporous silicas of MCM-41 and MCM-48 types were synthesized and modified with copper by template ion-exchange (TIE) technique. A high dispersion of deposited copper species was managed by subsequent treatment of the samples with ammonia, urea, or acetonitrile solution. Copper-modified silicas were analysed in terms of their chemical composition (ICP-OES), ordering of porous structure (XRD), textural parameters (low-temperature N₂ sorption), dispersion and form of introduced copper species (UV–vis-DR, XRD, H₂-TPR, NH₃-TPD). Mesoporous silicas modified with copper exhibited promising catalytic efficiency in selective catalytic reduction of NO with ammonia (NH₃-SCR). The samples containing dispersed copper species (predominantly monomeric copper cations) presented enhanced catalytic activity compared to catalysts containing CuO aggregates. On the other hand, CuO aggregates showed greater catalytic activity in the side process of direct ammonia oxidation by oxygen present in the reaction mixture. It was demonstrated that TIE post-treatment of the samples with urea resulted in most effective improving dispersion of deposited copper and is less destructive for ordered porous structures of mesoporous silica comparing to treatment with ammonia solution. Graphical abstract