The Effect of Oxygen Played in Nitrous Oxide Heterogeneous Reduction and the Behavior of Oxygen on Char Surface: Quantum Chemical and Kinetics Calculations

ABSTRACT

Oxygen plays an important role in heterogeneous reduction of N₂O by char in coal-fired power plants. In this study, we use quantum chemistry to investigate the most probable transition states, intermediates and products in the process of heterogeneous reduction between char and N₂O and to study the behavior of oxygen remaining on the surface of char. The oxygen-containing char surface, both the armchair and zigzag char, are beneficial to the adsorption of N₂O, but inhibits the reduction of N₂O. The mechanism and reaction rate between N₂O and two char models are different, which allowed us to study the different effects of oxygen on the heterogeneous reduction of N₂O by two char models. The results show that the adsorption rate constant of N₂O in the zigzag model is always greater than that of the armchair model and oxygen has a significant effect on the desorption of N₂ on the surface of armchair char. The behavior of oxygen remaining on char surface will take place CO₂ desorption, and it markedly occurs when the rate constants are higher than 10° s⁻¹ (>1000 K). The values of activation energy required for CO₂ desorption and the temperature of desorption are all consistent with available experimental results

KEYWORDS:

• Char
• heterogeneous reduction of N₂O
• oxygen
• desorption of N₂
• CO₂ desorption

Nomenclature

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Additional information

Funding

This work was supported by theNational Key Research and Development Program of China [grant number 2017YFB0601805] and the National Natural Science Foundation of China [grant number 51776001], [grant number 51376008].