Zeolites are microporous materials driving industrial scale adsorption, ion exchange, and catalytic processes. Their water content dramatically impacts their properties, but its quantification with Karl Fisher titration or thermal gravimetric analysis is problematic. When standard addition of water is combined with H magic angle spinning (MAS) NMR detection, absolute quantification of water in microporous materials becomes possible. The method was demonstrated on five different, commercially available zeolites.
EU-7 zeolite with Si/Al ratio of 15 is identified as a BIK type zeolite. The framework charge is compensated with Cs+ cations located in 8-ring channels at regular distances. Even partially exchanged, Cu-loaded EU-7 is active in NH3-SCR and withstands hydrothermal aging at 900 °C needed for application in diesel particulate filters.
Low temperature performance is key for catalysts used in selective catalytic reduction of NOx with ammonia (NH3-SCR). The best performing NH3-SCR catalysts are based on small pore copper loaded zeolites. A key question remains which structural and compositional parameters make a copper zeolite catalytically active in this application. In this work a collection of 83 different zeolite samples having 25 different frameworks and compositional variations was evaluated to uncover the critical structural and compositional parameters governing catalytic activity at 150 °C. The Si/Al ratio, the content of double six ring building units, the framework density and pore dimensionality were identified as having a strong impact on the catalytic activity of zeolites. A critical value for each of these parameters was determined. This knowledge was used to predict MOZ, SZR and GME as active NH3-SCR catalysts. They were synthesized respecting the compositional prerequisites and their catalytic evaluation confirmed the predicted high catalytic activity.
LEV type zeolites were synthesized with four different structure-directing agents and converted to copper loaded NH3-SCR catalysts. The synthesis recipe was found to impact the respective Al population in the...
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