Separation and Purification of Indole in Model Coal Tar Fraction of 9 Compounds System

ABSTRACT

Separation and purification of indole present in model coal tar fraction was examined by the combination of extraction to separate indole from the crude model coal tar fraction, distillation to obtain high concentration of indole in the extract, and solute crystallization (SC) to obtain high-purity indole present in indole-enriched distillate. The model fraction was made up of four types of nitrogen heterocyclic compounds (quinoline, iso-quinoline, 4.66% indole, and quinaldine), three types of bicyclic aromatic compounds (1-methylnaphthalene, 2-methylnaphthalene, and dimethylnaphthalene), biphenyl, and phenyl ether. Aqueous solutions of formamide and n-hexane were used as the extraction solvent and the SC solvent, respectively. Through the combination of formamide extraction, distillation, and SC using n-hexane in this work, 99.5% indole was recovered. We confirmed that the combination examined by this work was one of the very useful combinations for the high-purity purification of indole present in the coal tar fraction.

KEYWORDS:

• Coal tar fraction
• extraction–distillation–crystallization combination
• high-purity purification
• indole
• nitrogen heterocyclic compounds
• separation

Funding

This work was supported by an Academic Research Fund of Chungwoon University in 2016.