Structural parameters governing low temperature activity of small pore copper zeolites in NH3-SCR

Abstract

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.