In order to investigate the effects of oxygen on the distribution of thermal decomposition products from complex solid fuels, pyrolysis and fuel-rich oxidation experiments have been performed in an isothermal laminar-flow reactor, using the model fuel catechol (ortho-dihydroxybenzene), a phenol-type compound representative of structural entities in coal, wood, and biomass. The gas-phase catechol pyrolysis experiments are conducted at a residence time of 0.3 s, over a temperature range of 500-1000 degrees C, and at oxygen ratios ranging from 0 (pure pyrolysis) to 0.92 (near stoichiometric oxidation). The pyrolysis products are analyzed by nondispersive infrared analysis and by gas chromatography with flame-ionization and mass spectrometric detection. In addition to an abundance of polycyclic aromatic hydrocarbons, catechol pyrolysis and fuel-rich oxidation produce a range Of C-1-C-5 light hydrocarbons as well as single-ring aromatics. Quantification of the products reveals that the major products are CO, acetylene, 1,3-butadiene, phenol, benzene, vinylacetylene, ethylene, methane, cyclopentadiene, styrene, and phenylacetylene; minor products are ethane, propyne, propadiene, propylene and toluene. Under oxidative conditions, CO2 is also produced. At temperatures <850 degrees C, increases in oxygen concentration bring about increases in catechol conversion and yields of C-1-C-5 and single-ring aromatic products-in accordance with increased rates of pyrolytic reactions, due to the enhanced free-radical pool. At temperatures >850 degrees C, catechol conversion is complete, and increases in oxygen bring about drastic decreases in the yields of virtually all hydrocarbon products, as oxidative destruction reactions dominate. Reactions responsible for the formation of the C-1-C-5 and single-ring aromatic products from catechol, under pyrolytic and oxidative conditions, are discussed. (C) 2007 Elsevier Ltd. All rights reserved.