Composition of phenolic compounds in wastewater from the fixed-bed gasification of Baishihu coal

Crude phenols extracted using organic solvent from the wastewater of a typical fixed-bed gasification process was used as a raw material, and the distillation range was analyzed. The wide and narrow fractions of the raw material derived from distillation range analysis were cut using a real boiling point distillation device. The phenolic compounds in the different fractions were then qualitatively and quantitatively analyzed by gas chromatography after derivatization pretreatment. The yield of the < 290 °C fraction was 68.50% (mass fraction). A total of 33 effective phenolic compounds were identified in this fraction, and the percentage of identified phenols was nearly 80%. The contents of eight phenolic compounds were high, with phenol being the most abundant (26.34%) followed by catechol (13.44%). The contents of the remaining six abundant phenols ranged from 4% to 8%. The sum of the contents of m-cresol and p-cresol exceeded 12%, and the content of 5-indenol was nearly 8%. The yield of the fraction rich in low-grade phenols (< 230 °C) was 35.40%. The content of phenol in this fraction was more than 40%, the total content of cresol was over 23%, and the total content of m-cresol and p-cresol was nearly 20%. At room temperature, the 235–245 °C and 245–260 °C fractions were white crystals in which the catechol content was approximately 50%, and the 5-indenol content was more than 10%. The contents of these two high-value-added phenolic compounds are low in typical coal tar, making them difficult to extract. However, due to their strong polarity and good water solubility, catechol and 5-indenol are enriched in gasification wastewater by water selection, allowing their further extraction.