Selective catalytic reduction of NOx with ammonia (NH3-SCR) over copper loaded LEV type zeolites synthesized with different templates

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 two topologically different framework sites in double and single 6-rings, resolvable by Al-27 MAS NMR spectroscopy. Hydrothermal stability was found to be related to the silanol concentration, Si/Al ratio, particle size, crystal morphology, crystal defects, external surface area, and microporosity. Catalytic activity in NH3-SCR was dependent on preferential Al siting in the double 6-rings. Levinite synthesized using adamantylamine showed the strongest preference for Al atoms sitting in double 6-ring sites, and showed the highest catalytic turnover frequency. Unfortunately, because of the large crystal size, copper loading of this sample was limited to 0.6 wt% while other samples could be loaded with copper up to 3.3 wt%. An optimum combination of hydrothermal stability and catalytic activity was obtained with N,N '-bis-dimethylpentanediyldiammonium dibromide as structure-directing agent.

Automated summary

This paper investigates the synthesis of LEV type zeolites and their conversion to copper loaded NH3-SCR catalysts. It is found that the synthesis recipe affects the distribution of aluminum in the zeolite, and hydrothermal stability is related to factors such as silanol concentration and crystal morphology. Catalytic activity is dependent on the positioning of aluminum in the double 6-rings.