Magnetic resonance studies of reactions of urea and nitric oxide on FeZSM-5, HZSM-5 and silicalite

Abstract

Abstract Urea is a potential reducing agent for the selective catalytic reduction (SCR) of NOx. In this study, 13 C and 15 N solid state magic angle spinning nuclear magnetic resonance (MAS NMR) experiments were used to investigate the reactions of labeled urea ( 13 C and 15 N ) alone and with nitric oxide (NO) and oxygen on FeZSM-5 (Fe/Al=0.11), HZSM-5 and silicalite (purely siliceous form of ZSM-5) after thermal treatments at different temperatures. The hydrolysis of labeled urea to carbon dioxide and ammonia on FeZSM-5 and HZSM-5 after thermal treatments at elevated temperatures was observed using 13 C and 15 N MAS NMR. Reactions of NO, urea and oxygen on HZSM-5, FeZSM-5 and silicalite were also monitored with 13 C and 15 N MAS NMR. On both HZSM-5 and FeZSM-5, urea, NO and oxygen reacted to form nitrogen, carbon dioxide and ammonia. On silicalite, urea, NO and oxygen reacted to form CO2, ammonia and a side product with an imine functionality. No nitrogen was formed on silicalite. EPR spectroscopy was used to investigate the environment of the iron in FeZSM-5.