One new channel for the reduction of NO during gasification condition: An insight from DFT calculations

ABSTRACT

NCO is an important nitrogen-containing intermediate in coal combustion systems. This work reports the heterogeneous reaction of NCO+NO under gasification conditions using density functional theory (DFT) calculations at the M06–2X/6–311 G(d) level. The initial carbonaceous surface is represented by an armchair model. Under gasification conditions, NCO can be incorporated into the char surface and H₂O has greater reactivity as compared to CO₂. The optimal paths with five products (Pro1-5) are obtained by analysis of the reaction energy and the highest energy in the transition state (HETS). The results demonstrate that, compared with Pro 3 and Pro 4, the reaction paths of Pro 1 and Pro 2 possess lower HETS, which means that these reactions are more likely to occur. As for Pro 5, its highest value of HETS among the five products and the most unstable configuration signify that it is far from the expected product. Subsequently, we propose the reaction mechanism based on the Chemkin calculations. NCO+NO reaction can not only occur in the gas phase, but also can heterogeneously at the char surface. It can occur without external energy input for Pro 1 and Pro 2, indicating it will be one of the NO reduction channel under gasification conditions. The release of CO₂ is more favorable than the release of CO. CO₂ can be eliminated during the reactions and consequently provides good environment for N₂ removal with low energies. This work will provide some new understanding of the NO reduction under gasification condition.

KEYWORDS:

• DFT
• NO+NCO reaction
• reaction energy
• highest energy in transition state

Acknowledgments

This work is supported by the National Natural Science Foundation of China (Grant Nos. 51806140, 51876124) and Natural Science Foundation of Shanghai (Grant No. 21ZR1434300).

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the [51806140,51876124]; [21ZR1434300].