In situ infrared (IR) and mass spectroscopy (MS) coupled with temperature-programmed reaction (TPR), isotopic temperature-programmed desorption (TPD), step transient, and pulse transient techniques have been used to study the dynamic behavior of adsorbed species in the NO decomposition reaction on over-and underexchanged Cu-ZSM-5. Overexchanged Cu-ZSM-5 showed higher NO decomposition activity and produced more Cu + sites at lower temperatures than the underexchanged sample during the TPR study. Furthermore, overexchanged Cu-ZSM-5 allows rapid equilibrium between gaseous NO and Cu + (NO)/Cu 2+ -(NO 3 -) during NO decomposition. N 2 formation accompanied by the presence of Cu + (NO) suggests that Cu + initiates the NO decomposition process. However, no direct correlation between Cu + (NO)/Cu + (NO) 2 intensity and N 2 formation was observed. Adsorbed oxygen from dissociated NO changes the oxidation state of Cu + ion, causing the formation of Cu 2+ (NO 3 -). While Cu 2+ (NO 3 -) decomposes to N 2 , N 2 O, NO 2 , and O 2 during TPD, it is only partially responsible for the formation of O 2 during NO decomposition. Isotopic study shows that adsorbed oxygen on Cu-ZSM-5 desorbs during the pulse NO reaction. These results demonstrate the presence of two pathways for O 2 formation: oxygen produced from the decomposition of Cu 2+ (NO 3 -) and oxygen from the desorption of adsorbed oxygen on Cu-ZSM-5.
Highly dispersed uranium oxide nanocrystals supported on ordered mesoporous silica matrixes with large surface areas and porosities have been synthesized via a co-assembly methodology; the preliminary catalysis tests showed that these materials have a high catalytic activity for the thermal oxidation of volatile organic compounds (VOCs).
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