Mechanisms of molecular product and persistent radical formation from the pyrolysis of hydroquinone.
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 2.0s over a temperature range of 250-1000 degrees C. Below 500 degrees C, p-benzoquinone is the dominant product, while at temperatures above 650 degrees 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 degrees 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.
Truong
Hieu
H
Department of Chemistry, Louisiana State University Baton Rouge, LA 70803, USA.
Lomnicki
Slawo
S
Dellinger
Barry
B
D019840:2-Propanol / Q000737:chemistry; D006358:Hot Temperature; D006868:Hydrolysis; D006873:Hydroquinones / Q000737:chemistry*
D006873:Hydroquinones; D019840:2-Propanol; C031927:hydroquinone