## 3 Results
### GC/MS Analysis
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Most Likely Nitogenous Compounds** & **Retention Time** & **Relative Abundance a** & **Relative Content b** \\ \hline
3,5-Dimethylbenzaldehyde thiocarbamoylhydrazzone & 8.497 & 1.87 & 0.19 \\
3-methylcyclohex-2-en-1-one O-methyl oxime & 8.738 & 2.39 & 0.42 \\
4-(isopropylDimethyl)-N,N-dimethylaniline & 9.180 & 2.36 & 0.20 \\
2,2,6,6-tetramethylpiperidin-4-one O-acetyl oxime & 9.451 & 9.10 & 1.24 \\
5-(piperidin-1-yl)furan-2-carbaldehyde & 9.692 & 11.68 & 1.26 \\
3-Ethyl-5,6,7,8-tetrahydroquinoline & 9.973 & 2.61 & 0.24 \\
7-[2,2-dimethoxy-1-propyl]-py pyrrolizin-1-one & 10.074 & 4.06 & 0.38 \\
4-(2,6,6-Trimethyl-cyclohex-1-enyl)-but-3-en-2-one oxime & 11.098 & 5.48 & 1.04 \\
2-Acetyledcarbonylionine-3-carbonitrile & 11.972 & 1.95 & 0.10 \\
8-ethyl-2-methyl-4-quinion & 12.534 & 1.91 & 0.14 \\
12-Azabicyclo [9.2-2]pentadeca-1(14),11(15)-dien-13-one & 12.936 & 12.13 & 2.47 \\
6,7,8,9-Tetrabro-5-methylsiothiazole & 13.066 & 4.82 & 1.14 \\
[5,4-c]isoquinolin-1(2H)-one & 13.187 & 5.23 & 1.66 \\
1-[3-(3,3-Dimethyl-but-1-ynyl)-2,2-dimethyl- & 13.639 & 6.37 & 1.12 \\ cyclopropyl-1 piperazine & 16.672 & 16.68 & 2.74 \\
2-Methyl-a-Pyrolidinopropophenone & 18.459 & 6.63 & 1.38 \\
6,7-dichloro-5-[(1-ethyl)pyrrolidin-2-yl]methylamino]-1,3-dimethyl-pyrido [2,3-d]pyrimidine-2,4(1H,3H)-dione & 19.645 & 96.92 & 18.30 \\ \hline \hline \end{tabular}  
* Relative abundance was calculated from abundance ratios using the highest abundance as 100%; b calculated from Equation (1).  
\end{table} 
Table 4: _Cont._  
Figure 4: TIC plots of co-pyrolysis of tar-rich coal with NH4 Cl and \({}^{15}\)NH4 Cl, respectively (**a**): TIC plot of co-pyrolysis of tar-rich coal with NH4 Cl obtained by Py-GC/MS). (**b**): TIC plot of co-pyrolysis of tar-rich coal and \({}^{15}\)NH4 Cl obtained by Py-GC/MS. (**c**): The tar-rich coal and NH4 Cl tar were obtained by pyrolysis furnace, and then the TIC plot was obtained by GC/MS. (**d**): The tar-rich coal and NH4 Cl tar were obtained by pyrolysis furnace, and then the TIC plot was obtained by GC/MS). In addition, the coal tar from the co-pyrolysis of tar-rich coal with different nitrogen-containing compounds was separately examined by GC/MS, and also compared with the standard samples in the NIST 14 database, and after screening the compounds of each species, the results were calculated using Equation (1). As shown in Table 5, these nitrogen-containing compounds contain different nitrogen-containing functional groups such as amide, nitro, and cyano groups. When nitrogen-containing compounds were added during pyrolysis, the relative contents of aliphatic alkanes were reduced in all cases. Aliphatic alkanes in coal tar are mainly long-chain molecules with side chains, mainly because these aliphatic alkanes break into many short-chain alkane radicals at high temperatures and react with other free radicals to form new compounds. Similarly, the content of aromatic hydrocarbons also decreased to different degrees with each of the six nitrogen-containing compounds. The TIC diagrams of the six pyrolysis products were analyzed for peaks of each aromatic hydrocarbon, and it was found that the decrease in the relative content was mainly due to the increase in the content of nitrogen-containing compounds, which led to an increase in the total area of the peaks of the effective compounds. In addition, a minor contributor was also the exchange of free radicals with the hydrogens on the different aromatic rings. However, the relative content of aromatic hydrocarbons in the polyaniline group was significantly higher than with the other nitrogen-containing compounds, reaching 25.26%. The reason is that more benzene ring radicals are generated during the pyrolysis of polyaniline than other nitrogenous compounds, resulting in a higher relative content of aromatic hydrocarbons among the products. The relative content of phenolics decreased when NH\({}_{4}\)Cl, polyaniline, and melamine were added for the same reason that the content of aromatic hydrocarbons decreased.