Polycyclic aromatic hydrocarbons from the pyrolysis of catechol ( ortho-dihydroxybenzene), a model fuel representative of entities in tobacco, coal, and lignin

Abstract

In order to better understand the formation of polycyclic aromatic hydrocarbons (PAH) from complex fuels, we have performed pyrolysis experiments in a laminar-flow reactor, using the model fuel catechol ( ortho-dihydroxybenzene), a phenol-type compound representative of structural entities in tobacco, coal, and wood. Employing high pressure liquid chromatography with diode-array ultraviolet–visible (UV) detection, we have unequivocally identified 59 individual species among the condensed-phase products of catechol pyrolysis at a temperature of 1000°C and a residence time of 0.4 s. Also identified are two oxygen-containing compounds that are produced only at pyrolysis temperatures lower than 900°C. Of the total 61 species, fifty have never before been identified as pyrolysis products of any pure phenol-type compound. Two of the catechol pyrolysis products, 5-ethynylacenaphthylene and 3-ethynylphenanthrene, have never before been identified as products of any fuel. Ranging in size from one to eight fused aromatic rings, the catechol pyrolysis products comprise several compound classes: bi-aryls, indene benzologues, benzenoid PAH, alkylated aromatics, fluoranthene benzologues, cyclopenta-fused PAH, ethynyl-substituted aromatics, polyacetylenes, and oxygen-containing aromatics. The catechol pyrolysis products bear remarkable compositional similarity to the products of bituminous coal volatiles pyrolyzed at the same temperature – demonstrating the relevance of these catechol model compound experiments to the study of complex fuels such as coal, wood, and tobacco. The UV spectra, establishing compound identity, are presented for several of the identified catechol product components.