# Subcritical Extraction of Coal Tar Slag and Analysis of Extracts and Raffinates
## 2 Materials and Methods
### Test Analysis  
Infrared spectroscopy test: Infrared spectroscopy measurements were conducted using a Thermo Fisher Scientific Nicolet IN10&iZ10 FTIR spectrometer (Waltham, MA, USA) with KBr pellets. The scanning time was 2 min, the resolution was 4 cm\({}^{-1}\), and the scanning range was 400-4000 cm\({}^{-1}\).  
GC-MS: The GC-MS-QP 2010S gas chromatography-mass spectrometry (GC-MS) instrument was manufactured by Shimadzu Corporation, Nishinokyo Kuwabara-cho, Japan; the column was 30.0 m \(\times\) 250 \(\upmu\)m \(\times\) 0.25 \(\upmu\)m, the carrier gas was high-purity He, the temperature of the ion source was 230 \({}^{\circ}\)C, the temperature of the inlet port was 300 \({}^{\circ}\)C, the injection mode was shunt injection, the ratio of shunt injection was 120:1, and the injection volume was 1 \(\upmu\)L. The warming program was initialized. The temperature increase program was 60 \({}^{\circ}\)C, residence time of 5 min, 5 \({}^{\circ}\)C/min to 300 \({}^{\circ}\)C, and retained for 8 min.  
PY-GC-MS test: The instrument was an Agilent 7890B Thermal Cracking Mass Spectrometer (TCS-MS), Santa Clara, CA, USA; Firstly, the sample was pyrolyzed by the thermal cracker; the temperature of the sample was set at 200 \({}^{\circ}\)C, the time of the thermal cracking was 10 s, the injection volume of the thermal cracking was 0.5 mg, and the sample was detected using the gas chromatography-mass spectrometer (GC-MS), and the chromatographic column was an HP-5 ms Ultra. The column was HP-5 ms Ultra 30.0 m \(\times\) 250 \(\upmu\)m \(\times\) 0.25 \(\upmu\)m, the carrier gas was high-purity He, the temperature of the ion source was 230 \({}^{\circ}\)C, the scanning mode was Scan, the scanning mass range was 40-500 \(\upmu\)m, the splitting ratio was 150:1, and the injection volume was 1 \(\upmu\)L. The warming program was 5 \({}^{\circ}\)C/min at room temperature to 60 \({}^{\circ}\)C for 10 min, then 8 \({}^{\circ}\)C/min to 100 \({}^{\circ}\)C for 5 min, and then 8 \({}^{\circ}\)C/min for 5 min at room temperature for 5 min. The temperature increase program was 5 \({}^{\circ}\)C/min to 60 \({}^{\circ}\)C for 10 min at room temperature, then 8 \({}^{\circ}\)C/min to 100 \({}^{\circ}\)C for 5 min, followed by 10 \({}^{\circ}\)C/min to 200 \({}^{\circ}\)C for 5 min.  
Compound identification in extracts and raffinates was conducted using GC-MS and PY-GC-MS. The detected compounds were identified using NIST17 (National Institute of Standards and Technology Mass Spectral Library), with compound names and species determined based on confidence levels and similarity indices. Subsequently, semi-quantitative analysis was performed using the peak area method to determine compound species and relative concentrations.  
Data analysis and plotting in the article were performed using Origin2021 software from OriginLab, Inc. of Northampton, MA, USA.  
Experimental apparatus and equipment details are provided in Table 1.  
\begin{table}
\begin{tabular}{c c c c} \hline
**Equipment Name** & **Equipment Model** & **Address** & **Manufacturer** \\ \hline Muffle furnace & KSL-1100X & Hefei, China & Hefei Kejing Material Technology Co., Ltd. \\ Electrically heated blast drying oven & 101-OAB & Tianjin, China & Tianjin Taist Instrument Co., Ltd. \\ Elemental Analyser & Elementar Vario EL II & Hebi, China & Hebi Yingtai Electronic and Electrical \\ Sulfur meter & 5E-S3200 & Yuncheng, China & Anglance Co., Ltd. \\ Subcritical extraction equipment & CBE-T-1L & Henan, China & Ranfena Subcritical Extraction \\ Infrared spectrometer & Nicolet Ni10 kzi210 & Waltham, MA, USA & Thermo Fisher Sciedtific, USA \\ GC-MS & 7890A-5975C & Nishinokyo & Shimadzu Manufacturing, Japan \\ PY-GC-MS & 7890A-5975C & Santa Clara, CA, USA & Agilent Corporation of the United States \\ \hline \end{tabular}
\end{table}
Table 1: Experimental apparatuses and equipment.