DFT Study on the C–NO Coupling Reaction with Different Active Sites

ABSTRACT

The heterogeneous interaction between NO and char with two to four active sites (R1–R3) has been studied using density functional theory (DFT). The thermodynamic parameters which can be used as an important foundation for distinguishing the differences in reaction mechanism are calculated. The calculations show that active sites play an important role in NO adsorption. R3 provides more sites for NO adsorption, which is more favorable for NO chemisorption. The energy barrier for NO reduction to N₂O or N₂ on R1, R2, and R3 surface is 122.25, 81.5, and 38.4 kJ/mol, respectively, signifying that the more active sites on char surface are more conducive to NO reduction. On the other hand, the difference in energy barrier values of N₂ desorption on R2 and R3 surface reveal that oxygen-containing groups on different char surface have different effects on N₂ desorption. Thermodynamic parameters of char-NO reaction at different active sites are further analyzed, and the strong dependence of the reaction process on the active sites is clarified through thermodynamics. The calculation results deepen the mechanism of NO reduction and lay a foundation for further research.

KEYWORDS:

• Char
• NO
• active site
• thermodynamic parameters
• density functional theory

Highlights

$\bullet$Active sites play an important role in NO adsorption.

$\bullet$More active sites on char surface are more beneficial to NO reduction.

$\bullet$Oxygen-containing groups on different char surface have different effects on N₂ desorption.

$\bullet$Thermodynamic analysis shows that NO heterogeneous reaction process strongly depends on the active sites.

Acknowledgments

This work was supported by the National Key Research and Development Program of China (2017YFB0601805) and the National Natural Science Foundation of China (51776001, 51376008).

Additional information

Funding

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