*3.3. Fractional Distillation*

The pretreated condensate (referred as oil) was successfully divided into its fractions by means of distillation. The initial boiling point of the oil was 67 ◦C. The highest column head temperature reached was AET 225 ◦C at 100 mbar. All substances (and mixtures) with boiling points above 225 ◦C were considered as residue and were not prepared for analysis. Four pure monocyclic aromatic fractions (referred to as main products) including BTEX aromatics and styrene with a total mass fraction of 46.68 wt.% of the initial oil feed were obtained from distillation. Additionally, three fractions enriched in valuable monocyclic aromatic substances as styrene, phenol, α-methyl styrene, cresols, and polycyclic naphthalene with a total mass fraction of 20.89 wt.% were yielded. Along with these, 27.66 wt.% residue and 2.04 wt.% cold trap fractions were produced. Two cold trap fractions were collected during distillation. A mass balance of the distillation process is presented in Table 4, implying a mass loss of 2.73 wt.%, presumably due to mass hold-up in the column.


All fractions yielded by means of distillation are depicted in Figure 4. It can be observed that fractions 1 to 4 were colorless and transparent, indicating high chemical stability. Fractions 5 and 6 showed a light brown color, which is typical for oxidized phenolic compounds contained in the fractions. Fraction 7 and the distillation residue comprise dark brown to black opaque appearance.

Fraction 1 (RT–85 ◦C), with a mass fraction of 8.92 wt.%, solely consisted of benzene and toluene with a proportion of 88.00 area% benzene and 12.00 area% toluene. The chlorine, bromine, and water concentrations were determined to be 221 ± 25 ppm, 20 ± 1 ppm, and 8833 ± 170 ppm, respectively.

Fraction 2 (85–115 ◦C) contained mostly toluene with a proportion of 96.23 area% as well as benzene (3.20 area%), 113 ± 33 ppm chlorine, 3 ± 1 ppm bromine, and 1333 ± 125 ppm water. The mass fraction represented 14.29 wt.% of the initial mass.

Fraction 3 (115–140 ◦C) with a mass fraction of 5.95 wt.% contained a mixture of toluene, ethylbenzene, xylenes, and styrene. The GC-MS result shows that ethylbenzene had the highest proportion with 43.15 area%, followed by 26.83 area% toluene, 25.41 area% styrene, and 4.15 area% xylenes. The fraction had a chlorine concentration of 836 ± 93 ppm, a bromine concentration of 6 ± 1 ppm, and a water concentration of 400 ± 216 ppm.

Fraction 4 (140–150 ◦C) with a mass fraction of 17.52 wt.% mostly consisted of styrene 79.98 area%. The GC/MS analysis also determined 16.83 area% ethylbenzene, 2.26 area% xylenes, and a trace amount of toluene and 1-methylethyl-benzene. Moreover, this fraction contained 150 ± 23 ppm chlorine, 280 ± 3 ppm bromine, and 333 ± 170 ppm water.

Fraction 5 (150–190 ◦C) consisted of styrene, phenol, α-methyl styrene, and naphthalene, where phenol 35.13 area% is the most present, followed by 23.52 area% styrene, and 10.48 area% α-methyl styrene. It was noted that this fraction also contained 12.74 area% indene (SI 96%). The bromine concentration of fraction 5 was the highest compared to the other fractions (1100 ± 58 ppm), along with 303 ± 27 ppm chlorine and 1233 ± 125 ppm water. The mass fraction of fraction 5 was 10.84 wt.%

Fraction 6 (190–205 ◦C), with a mass fraction of 6.24 wt.%, consisted of 37.07 area% phenol, 27.16 area% naphthalene, 19.06 area% benzonitrile (SI 98%), 13.98 area% cresols, trace amounts of aniline, 3-phenyl-2-propenal, and derivatives of benzene, indene, and benzofuran. This fraction exhibited chlorine, bromine, and water concentrations of 99 ± 13 ppm, 249 ± 1 ppm, and 833 ± 170 ppm, respectively.

Fraction 7 (205–225 ◦C) represented 3.81 wt.% of the initial mass, predominantly containing naphthalene with a proportion of 40.45 area%, followed by 31.81 area% cresols, 6.87 area% 1-methyl-naphthalene (SI 97%), 4.52 area% 2-methyl-benzonitrile (SI 96%), 3.56 area% benzonitrile (SI 98%), 1.24 area% phenol, as well as several derivatives of benzonitrile, naphthalene, benzofuran and traces of other compounds. High chlorine (1914 ± 517 ppm) and bromine (405 ± 10 ppm) concentration compared to lower boiling point fractions were determined. This fraction's water concentration exhibited 900 ± 141 ppm.

In the distillation residue (boiling point >225 ◦C), derivatives of naphthalene, benzene, fluorene, anthracene, and pyrene were identified, containing high concentrations of chlorine (1538 ± 36 ppm) and bromine (4316 ± 159 ppm).

The results from GC-MS, EDXRF, and water concentration analysis are summarized and presented in Figures 2 and 3.

*Processes* **2021**, *9*, 530
