Mechanistic of the effect of differential electron density characteristic groups on the nitrogen migration transformation in coal
The choice of pyrrole-and pyridine-containing nitrogen heterocycles as the subject of this paper was made in,and based on this,the mechanism and pattern of action of the influence of functional groups on the migration and transformation of nitrogen components of coal pyrolysis were studied.First,the CBS-QB3 was used to optimize the paths of pyrrole and pyridine pyrolysis to HCN and NH3,and the corresponding reaction potential energy surfaces were derived.Additionally,the accumulated 112 nitrogen migration conversion pathways of pyrrole and pyridine derivatives were optimized,the functional groups were divided into electron-donating(EDG)and electron-withdrawing groups(EWG),and the summation values of the bond polarity indices of the groups were calculated based on Pauling electronegativity.Finally,12 appropriate descriptors were screened by comparing Pearson correlation coefficients,which were derived from the structures effectively optimized by DFT calculations.By integrating multiple linear regression models,the greatest response activation energy in the coal-nitrogen migration conversion process was predicted,and the MLR model constructed had a coefficient of determination of 0.83,a root mean square error of 0.41 for the training set and a coefficient of determination of 0.92 and a root mean square error of 0.29 for the test set.The model could be used to estimate activation energy since it has high fitting and prediction ability.An in-depth analysis of the multiple linear regression equation of the model reveals that the coefficient of the group type is the largest(0.71),followed by the energy gap of the reactants(0.64)and the difference between the energy gaps of the reactants and products(-0.59),further confirming the significant influence of the group type on the nitrogen migration transformation.The findings of this paper can guide the mechanistic study of coal nitrogen migration conversion and aid in the creation of new ultra-low NOx combustion technologies.
model coalpyrolysisfunctional groupdensity functional theoryactivation energyNOx
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