Solid-State Nuclear Magnetic Resonance Study of Acetone Oxime Adsorbed on CuZSM-5 and on HZSM-5

Abstract

The reactions of acetone oxime, a proposed reaction intermediate for the selective catalytic reduction (SCR) of NO with propane on CuZSM-5 and on HZSM-5, have been studied with13C and15N solid-state magic-angle spinning nuclear magnetic resonance (MAS NMR). The carbon- and/or nitrogen-containing surface species, as well as the products formed under conditions of thermodynamic equilibrium, have been monitored and identified. In the absence of NO and after heating to 150–200°C, the main hydrolysis products of adsorbed acetone oxime on CuZSM-5 are acetone and hydroxylamine, while the main hydrolysis products on HZSM-5 are acetic acid and methylamine. In addition, N2and N2O are formed from acetone oxime adsorbed on both HZSM-5 and CuZSM-5. In the presence of15NO, the observation of mixed-labeled14N15NO and15N14NO shows that new N–N bonds are formed over CuZSM-5 and HZSM-5 between two different nitrogen atoms: one from gaseous15NO molecules and the other from adsorbed acetone oxime and/or acetone oxime hydrolysis products. When15NO and unlabeled acetone oxime are reacted on CuZSM-5, the14N15NO/15N14NO ratio is approximately 3, suggesting that the NO bond of gas-phase NO remains intact when it reacts with acetone oxime to form N2O. It is also found that the formation of new N–N bonds from the reaction of NO and acetone oxime occurs at room temperature on CuZSM-5, but not until ∼150°C on HZSM-5.