Kalcinované hydrotalcit-zeolitové sloučeniny jako katalyzátory pro selektivní katalytickou oxidaci NH3

Abstract

This bachelor’s thesis examines composite catalysts based on calcined hydrotalcite materials deposited on the surface of ZSM-5 and Y zeolites intended for the selective catalytic oxidation of ammonia (NH₃-SCO). The aim of the thesis is to test the activity and elucidate the influence of the structure and composition of these catalysts on their catalytic properties, while also assessing the influence of experimental conditions on the activity and selectivity of NH3-SCO. The materials were characterised by using temperature-programmed ammonia desorption (NH3-TPD) and reactive frontal nitrous oxide chromatography (N2O-RFC), which provide information on the distribution and strength of acid sites and the specific surface area of copper. Catalytic tests were conducted under various conditions, namely in the presence of NOx and water vapour, to assess their effect on ammonia conversion and nitrogen selectivity. The best catalytic results were achieved on a sample containing ZSM-5 zeolite (Si/Al=6) and 13,6 wt.% Cu. The addition of NOx increased NH₃ conversion while maintaining high selectivity toward N₂, whereas the addition of H₂O decreased it. Deactivation due to H₂O was partially reversible; repeated exposure to H₂O did not lead to a further decrease, suggesting that only a small fraction of the active sites was irreversibly affected.