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Hydroquinone is considered to be one of the major, potential molecular precursors for semiquinone-type radicals in the combustion of complex polymeric and oligomeric structures contained in biomass materials. Comprehensive product yield determinations from the high-temperature, gas-phase pyrolysis of hydroquinone in two operational modes (rich and lean hydrogen conditions) are reported at a reaction time of 2.0
s over a temperature range of 250–1000
°C. Below 500
°C,
p-benzoquinone is the dominant product, while at temperatures above 650
°C other products including phenol, benzene, styrene, indene, naphthalene, biphenylene, phenylethyne, dibenzofuran and dibenzo-
p-dioxin are formed. Hydrogen-rich conditions initially inhibit hydroquinone decomposition (below 500
°C) but promote product formation at higher temperatures. The decomposition process apparently proceeds via formation of a resonance stabilized
p-semiquinone radical. Detailed mechanisms of formation of stable molecular species as well as stable radicals are proposed.