Separation and identification of carbazole, benz[ e]indole and benz[ g]indole in coal-derived materials

Abstract

Nitrogen-containing polycyclic aromatic compounds (N-PAC) are generally found in products of coal utilization from processes such as liquefaction, gasification, combustion and coking. Carbazole, a three-ring pyrrole compound, is typically one of the major N-PAC components. In studying the chemical composition of the pyrrolic-PAH isolate of a solvent-refined coal (SRC) liquid, other isomers of carbazole ( m z 167) were detected by gas chromatography-mass spectrometry. From subsequent analyses, carbazole and two additional C 12H 9N pyrrolic isomers have been identified: 1 H-benz[ g]indole and 3 H-benz[ e]indole. Isolation of the three C 12H 9N isomers was achieved by an integrated separation method using adsorption, liquid and gas chromatography. Molecular structures and elemental compositions were determined by highresolution mass spectrometry, ultraviolet spectrophotometry and nuclear magnetic resonance spectroscopy. Carbazole, 1 H-benz[ g]indole and 3 H-benz[ e]indole were identified in a SRC distillate liquid and a commercial creosote oil.