# Subcritical Extraction of Coal Tar Slag and Analysis of Extracts and Raffinates
## 3 Results and Discussion
### Coal Tar Slag Raffinate PY-GC/MS Test  
After the previous infrared spectroscopy and GC-MS extract results, a preliminary conclusion can be drawn: after subcritical 60 \({}^{\circ}\)C extraction on coal tar slag, a large number of aromatic hydrocarbons were detected in the extract; in the second and third extracts, aromatic hydrocarbons were not detected, indicating that the tar slag contained volatile aromatic hydrocarbons. A PY-GC-MS test will be performed on the three raffinates to confirm this conclusion. \begin{table}
\begin{tabular}{c c c c c} \hline
**No.** & **Compound Names** & **Proposed** & **Molecular Weight** & **Relative Content, \%** \\ \hline
52 &
\begin{tabular}{c} Valtrate \\ Squalane \$5 Tetracosane, \\ 2,6,10,15,19,23-hexamethyl- \\ Isophthalic acid, 3,7-dimethylylect-6-enyl \\ tricoglycan ester \\ \end{tabular} & C\({}_{24}\)H\({}_{30}\) & 422.50 & 0.84 \\
55 &
\begin{tabular}{c} L916-Methylriucosaet \\ Heptaosyl trifluoroacetate \\ Hexacosyl trifluoroacetate \\ \end{tabular} & C\({}_{29}\)H\({}_{56}\)F\({}_{3}\)O\({}_{2}\) & 422.50 & 0.26 \\
47 &
\begin{tabular}{c} 2-Methyl-L-7-octadec \\ 5-Methyl-L-2-5-dodecene \\ \end{tabular} & C\({}_{28}\)H\({}_{50}\) & 266.50 & 0.14 \\ \hline
55 &
\begin{tabular}{c} **Nitrogen compounds** \\ Hexadecaneditrile \\ 1-Decanol, 2-hexyl- \\ Carbonic acid, eicosyl vinyl ester \\ \end{tabular} & C\({}_{16}\)H\({}_{28}\)N\({}_{2}\) & 248.41 & 0.09 \\
56 &
\begin{tabular}{c} **Sulfurons compounds** \\ Sulfurons acid, cyclohexylmethyl heptyl ester \\ \end{tabular} & C\({}_{14}\)H\({}_{28}\)O\({}_{5}\) & 276.44 & 0.37 \\
18 &
\begin{tabular}{c} Sulfurons acid, di(cyclohexylmethyl) ester \\ Sulfurons acid, cyclohexylmethyl pentadecyl \\ \end{tabular} & C\({}_{22}\)H\({}_{44}\)O\({}_{5}\) & 388.60 & \\
57 &
\begin{tabular}{c} Sulfurons acid, cyclohexylmethyl pentadecyl \\ ester \\ \end{tabular} & C\({}_{24}\)H\({}_{28}\)O\({}_{5}\) & 388.60 & \\
58 &
\begin{tabular}{c} Sulfurons acid, di(cyclohexylmethyl) ester \\ 2-Pyrazoline, 5-ethyl-1,4-dimethyl- \\ \end{tabular} & C\({}_{27}\)H\({}_{14}\)N\({}_{2}\) & 126.20 & 1.06 \\
59 &
\begin{tabular}{c} **Other compounds** \\ Tetracosyl pentafluoropropionate \\ \end{tabular} & C\({}_{27}\)H\({}_{5}\)F\({}_{3}\)O\({}_{2}\) & 500.70 & 0.44 \\
29 &
\begin{tabular}{c} Nonyl tetracosyl ether \\ 1-Decanol, 2-hexyl- \\ Triacontane, 1-bromo- \\ Hexacosane, 1-iodo- \\ \end{tabular} & C\({}_{28}\)H\({}_{50}\)H\({}_{61}\)Br & 501.70 & 0.61 \\
48 &
\begin{tabular}{c} Hexacosane, 1-iodo- \\ Dotriacontane \\ 2- Bromopropionic acid, octadecyl ester \\ \end{tabular} & C\({}_{29}\)H\({}_{51}\)Br\({}_{52}\)O\({}_{2}\) & 450.50 & 0.53 \\
57 &
\begin{tabular}{c} Heptadecane, 9-(2-cyclohexylethyl)- \\ Cyclohexane, (2-decyldodecyl)- \\ \end{tabular} & C\({}_{28}\)H\({}_{56}\) & 392.70 & 0.53 \\ \hline \end{tabular}
\end{table} 
Table 6: _Cont._Figure 12 below shows the PY-GC-MS total ion flow chromatogram of the first raffinates of the subcritical extraction of tar slag. Table 7 below shows the results of the identification and analysis of the three volatile organic components detected in Figure 12.  
As can be seen in total ion flow chromatogram 12 and Table 7 of the composition of the extract, only three volatile substances were detected in the first extract, which were aliphatic hydrocarbons, with a relative content of 0.79%; aldehydes, with a relative content of 7.60%; and carboxylic acids, with a relative content of 37.56%. These three substances are not in the 16 PAHs announced by the U.S. Environmental Protection Agency, indicating that there are no volatile toxic PAHs in the raffinates after a subcritical 60 \({}^{\circ}\)C extraction. Table 8 below shows the results of the identification and analysis of the two volatile organic components detected in Figure 13.  
As can be seen in total ion flow chromatogram 13 and Table 8 of the composition of the raffinates, only two volatile substances were detected in the second raffinate, which were aldehydes, with a relative content of 7.70%, and carboxylic acids, with a relative content of 37.55.