DFT study on the alternative NH3 formation path and its functional group effect

Impact Factor:

5.772

DOI number:

10.1016/j.fuel.2017.11.001

Journal:

Fuel

Key Words:

NH3 formation, DFT study, the functional group effect, activation energy, reaction energy

Abstract:

This study attempts to better understand through DFT calculations the NH3 formation mechanism associated with the reaction energy and barrier height. The formation of NH3 can be completed by (1) heterogeneous nitrogen migration; (2) NH2 desorption; and (3) homogeneous H-abstraction. Several transition structures have been characterized and we can conclude from energy analysis of these species that the heterogeneous nitrogen migration is the rate determining step and the formation of NH3 is largely dependent on the char-N stability. The NH3 formation is affected not only by the availability of H radicals but also by the vicinity of functional groups. The functional group effect is then investigated and further analyzed by the transferring of valence electrons and NBO charges. The results seem to be clear that NH3 formation is group-dependent. For example, the OH group acting as an electron donor will activate the carbonaceous surface and decrease the barrier height and the endothermicity, while the electron-withdrawing NO2 group plays an opposite role. Our work gives the molecular-level understanding for the previous experimental finding that oxygen-containing functional groups are important for the NH3 formation.

Co-author:

Jianguo Liu, Lei Luo, Xiumin Jiang

First Author:

Hai Zhang

Correspondence Author:

Jiaxun Liu

Volume:

214

Issue:

2018

Page Number:

108-114

ISSN No.:

0016-2361

Translation or Not:

no

Date of Publication:

2018-02-15

Links to published journals:

https://www.sciencedirect.com/science/article/pii/S0016236117313935