## 3 Results and Discussions
### Characterization of Narrow Distillate Fractions by GC-MS  
Figure 4 shows the GC-MS chromatograms of narrow distillate fractions obtained by true boiling distillation. Distillation is a very convenient method for separating and concentrating components of liquid fossil fuels. However, ordinary distillation methods are not suitable for the easy-oking and thermal sensitive materials in MLCT. True boiling distillation can be operated under vacuum pressure and helps minimize property changes. As shown in Figure 4, as the distillate boiling point temperature increases, the narrow distillate fractions become heavier, and the peak residence time changes from short to long. Compared with the full-range, the narrow distillate fractions have a simpler composition and a more concentrated carbon distribution. The overlap of adjacent components indicates that the components of MLCT cannot be separated completely by true boiling distillation. The results show that phenols and alkylbenzenes are the main compounds in the distillate fractions below 170 \({}^{\circ}\)C, especially phenol and BTX (benzene, toluene, and xylene) in the fractions below 170 \({}^{\circ}\)C, the content of BTX in MLCT-Z is approximately 27.2%, while the content of phenol in MLCT-S is approximately 33.6%. The fractions below 170 \({}^{\circ}\)C are a suitable feedstock for chemical products rich in BTX aromatics. In the fractions of 170-230 \({}^{\circ}\)C, phenolic substances are dominant, and the content of phenols is more than 60%. However, the other compounds, such as the homologs of benzene and naphthalene compounds are also present. The main phenolic compounds in the170-230 \({}^{\circ}\)C distillate fraction are low-rank phenols, such as phenol, cresol, and xylenol. The higher-rank phenols (such as C\({}_{3}\)-C\({}_{4}\) alkyl phenols), indenols, naphthols, and alkyl naphthols, are concentrated in fractions above 230 \({}^{\circ}\)C. Naphthalene is in the190-210 \({}^{\circ}\)C and 210-230 \({}^{\circ}\)C distillate fractions, and its homologs are in \begin{table}
\begin{tabular}{c c c} \hline \hline \multirow{2}{*}{**Hydrocarbon Group Types**} & \multicolumn{2}{c}{**Weight Percent (wt \%)**} \\ \cline{2-3}  & **MLCT-Z** & **MLCT-S** \\ \hline paraffins & 18.1 & 11.3 \\
1-ring cycloalkanes & 5.6 & 4.2 \\
2-ring cycloalkanes & 3.1 & 2.1 \\
3-ring cycloalkanes & 3.3 & 2.1 \\
4-ring cycloalkanes & 0.7 & 0.7 \\ total cycloalkanes & 12.7 & 9.1 \\ Total Saturates & 30.8 & 20.4 \\ alkylbenzenes & 4.7 & 9.7 \\ naphthalenebenzenes & 0.7 & 0.6 \\ diaphthenebenzenes & 0.8 & 0.7 \\ indans or tetralins & 4.6 & 6.0 \\ indenes & 3.4 & 7.9 \\ total monoaromatics & 14.2 & 24.9 \\ naphthalenes & 7.6 & 7.6 \\ acenaphthenes & 6.3 & 6.8 \\ acenaphthylenes & 3.5 & 4.2 \\ fluorenes & 1.5 & 1.3 \\ total diamoratics & 18.9 & 19.7 \\ total triaromatics & 5.5 & 5.2 \\
4-ring aromatics & 3.2 & 2.9 \\
5-ring aromatics & 0.7 & 0.6 \\ benzothiophenes & 0.7 & 0.6 \\ dibenzothiophenes & 0.2 & 0.2 \\ total sulfur compounds & 0.9 & 0.8 \\ unidentified aromatics & 1.1 & 1.0 \\ Total Aromatics & 44.5 & 55.3 \\ Resins & 24.7 & 24.5 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Hydrocarbon type analysis of the MLCT. the 230-250 \({}^{\circ}\)C and 250-270 \({}^{\circ}\)C distillate fractions. Fluorenes, dibenzofuran and octadecane are in the 270-300 \({}^{\circ}\)C distillate fractions. Alkyl fluorenes and alkyl naphths, phenanthrene, nonadecane are in the 300-320 \({}^{\circ}\)C distillate fractions. Phenanthrenes, eicosane, and heneicosane are in the 320-340 \({}^{\circ}\)C distillate fractions. Alkanes, pyrene, anthracene, phenanthrene, and its homologs are in the 340-360 \({}^{\circ}\)C distillate fractions. The MLCT middle distillates (170-230 \({}^{\circ}\)C) are rich in phenols, which are the main raw chemical materials in the chemical industry and should be extracted from coal tar before hydrogenation. As is known, phenolic compounds generate water during the hydrotreating process.