| Abstract
| - To better understand the role of C2 species in the formation of polycyclic aromatic hydrocarbons (PAH) from complex solid fuels, we have performed pyrolysis experiments with the model fuel catechol (ortho-dihydroxybenzene)—a phenol-type compound representative of structural entities in coal, wood, and biomass—in an isothermal laminar-flow reactor, with acetylene added as a dopant. The catechol pyrolysis experiments are conducted at a residence time of 0.3 s, at temperatures of 500−1000 °C, and at a fixed catechol-to-acetylene molar feed ratio of 0.785. The pyrolysis products are analyzed by high-pressure liquid chromatography with ultraviolet-visible absorbance detection and by gas chromatography with flame-ionization and mass spectrometric detection. Product quantification reveals that acetylene addition to the catechol pyrolysis environment does not change catechol conversion or the yields of most C1−C5 hydrocarbon products. Acetylene addition does, however, increase the yields of the C3 products and facilitate consumption of the C4 products. As for the one- and two-ring aromatics, acetylene addition brings about increases in the yields of benzene, toluene, phenylacetylene, and indene. Except for the highest temperature (1000 °C), however, the yields of naphthalene are unaffected by the addition of acetylene. The experimental results show consistency with acetylene addition to a benzyl radical being the dominant pathway for indene formation and with cyclopentadienyl radical self-addition being the dominant reaction pathway for naphthalene formation. Since the C1−C10 products are participants in reactions leading to PAH, the observed effects of acetylene addition are relevant to the mechanisms of PAH formation and growth.
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