Mechanism Of NO Decomposition Research Articles

On the mechanism of NO decomposition on Cu-ZSM-5 catalysts

Decomposition of NO was studied on Cu-ZSM-5 catalysts prepared by solid state ion exchange using CuCl 2 (I), CuO (II) and by conventional liquid phase ion exchange with copper acetate (III). There was no difference in the catalytic activity among samples (I), (II) and (III) using the same copper loading. Treatment of the samples in argon, in air or in NO/Ar mixture at 700°C was necessary to develop optimum catalytic activity. Transient kinetic experiments using NO carried out under isothermal conditions, showed overshoots in the N 2 and O 2 concentration at the front and tail edge, respectively. Fourier transform-infrared studies indicated the formation of oxidized copper sites and adsorbed NO 2 species during the NO decomposition. In a proposed mechanism Cu 2+(O)(NO)(NO 2) intermediate was suggested to play a key role in the NO decomposition.

UHV-TPD study of NO adsorption/reaction over [formula omitted

The chemisorption state of NO adsorbed on Cu ZSM-5 was investigated by the TPD method in an UHV system and was discussed to be correlated with the NO decomposition mechanism. The three distinct states of NO adsorbed on Cu ZSM-5 ( T ad = 175 K) are indicated by the appearance of the peaks at 210 K (α), 330 K (β) and 480 K (γ) with increasing exposure. It is found that the β peak is attributable to NO adsorbed on Cu + ions, while the α peak is assigned to NO physically adsorbed on support. At high exposure pressure, a new peak is developed and N 2 and N 2O are produced during TPD, suggesting that a dinitrosyl species as an intermediate species for NO decomposition is formed.

Mechanism of NO decomposition in a solid electrolyte reactor by SEP method

The mechanism of the NO decomposition in the presence of excess O 2, H 2O and CO 2 using a ceria-based oxide ionic conductor with a Pd electrode has been studied by solid electrolyte potentiometry (SEP) method. A single compartment cell for measuring P O 2 , Pt | YSZ | Pt, are attached to another single compartment cell for decomposing NO, Pd | Ce 0.8Sm 0.2O 1.9 | Pd, where their working electrodes come into contact with each other. Experiments were carried out with a mixture of 2611 ppm NO, 0.1–4% O 2, 0–5% H 2O and 0–5% CO 2 in argon at 800°C. A P O 2 measurement in the neighborhood of the Pd electrode during NO decomposition confirms that the NO decomposition is initiated after the electrochemical oxygen pump is completed. A comparison of the Pd electrodes heated at 850°C with that heated at 1300°C shows that the poorer the oxygen pumping property, the better the NO decomposition. On the basis of these results, the mechanism of the NO decomposition is discussed in detail. In addition, the SEP method also gives information about the influences of the coexistent O 2, H 2O and CO 2 on the NO decomposition.