## 3 Results and Discussions  
The aliphatic-rich solvent was fractionalized by distillation to alter its paraffinicity. As distillation pressure drops, the \(K\)-factor (i.e., a theoretically calculated parameter representing paraffinicity) increases due to the rising atmospheric equilibrium temperature of evaporating substances (Table 1). The individual chemical component was identified by GC-MS, and major substances were analyzed as decane (C\({}_{10}\)H\({}_{22}\)) for distillate #1, dodecane (C\({}_{12}\)H\({}_{26}\)) for distillate #2, and tridecane (C\({}_{13}\)H\({}_{28}\)) for the residue, as shown in Figure 2a. The strong absorbance peak found at ca. 2925 cm\({}^{-1}\) is attributed to paraffinic characteristics (i.e., vibration of axial deformation of C-H of the CH\({}_{2}\) group) [16] and was found to increase in the order of distillate #1, distillate #2, and the residue. The paraffinicity was confirmed to be proportional to the boiling temperatures of aliphatic substances in the solvent, well corresponding to the calculated \(K\)-factors in this work (Table 1). Figure 2: Spectrum of GC-MS **(a)** and FTIR **(b)** for fractionally distilled additives. The high-temperature- and pressure-assisted extraction condition adopted in this work is believed to enhance the QI-extraction efficiency because it is governed by solubility and mass transfer effects dominantly. A high reaction temperature promotes faster diffusive transport between components of the system, while pressurized conditions are beneficial to maintain the liquid state of volatile substances, yielding enhanced solubility. When this process is combined with high-K-factor additives, a drastic reduction in the QI content of the treated coal tar pitch results, as shown in Table 2. The QI content of purified coal tar pitch was analyzed to be 0.1% at a process production yield of up to 72%. However, the extraction condition with a lower-\(K\)-factor additive (i.e., distillate #1) was not found to be effective to remove QI from the coal tar pitch. This result confirms that the paraffinic nature of the extracting solvent is strongly relevant to the QI removal performance for coal tar pitch, as discussed in a previous study [14]. To evaluate the rheological behavior of QI-removed coal tar pitch, dynamic viscosities were measured at various temperatures, times, and shear rates. Figure 3 represents the non-Newtonian thixotropic (i.e., time-dependent) and shear-thinning characteristics of the QI-removed coal tar pitch. The shear-thinning phenomenon was found to be more prominent at higher temperatures (above 150 \({}^{\circ}\)C). Figure 4 shows Arrehenius-type plots ln (\(\mu\)) versus 1/T for QI-removed coal tar pitch and linear regression fits to experimental data. When fitted to an Arrhenius-type equation, the shear activation energy was calculated as 56.6 kJ/mol. As stated in previous work [17], the shear activation energy can be used as a crucial index for molecular susceptibility to environmental temperature variation, the degree of intermolecular entanglement, interaction, and steric hindrance. The shear activation energy of the commercial pitch product with a higher softening point (A240, Marathon Petroleum Corp., softening point of 115 \({}^{\circ}\)C) was reported to be 136 kJ/mol, indicating higher molecular stiffness or restricted inter-molecular motions [17]. The coke texture images attained by the polarized light microscope are shown in Figure 5. The microscopic texture found in all the prepared coke specimens can be categorized into the general anisotropic flow domain. However, coke derived from the QI-removed coal tar soft pitch with an additive solvent having a \(K\)-factor of 10 or above (Figure 5b,c) presented better texture orientation: needle-like uniaxial orientation as the \(K\)-factor fell between 10 and 10.3. This result is believed to be derived from the increased freedom of molecular motion in the QI-removed soft pitch during the coking process [18].