The pyrolysis of anisole (C6H5OCH3) using a hyperthermal nozzle
We have investigated the pyrolysis of anisole (C6H5OCH3), a model compound for methoxy functional groups in lignin. An understanding of the pyrolysis of this simple compound can provide valuable insight into the mechanisms for the thermal decomposition of biomass. Our emphasis in this study is the formation of polynuclear aromatic hydrocarbons (PAHs) and in particular we investigate the formation of naphthalene. The route to the formation of naphthalene from anisole follows the simple unimolecular decomposition of anisole, which leads to the phenoxy radical and then cyclopentadienyl radical. This chemical pathway has been demonstrated before, but the subsequent reaction of two cyclopentadienyl radicals to give naphthalene has only been the subject of theoretical investigations. We have used matrix isolation FTIR spectroscopy together with photoionization time-of-flight (TOF) mass spectrometry to identify intermediates in this reaction mechanism. Using this technique, we have trapped phenoxy and cyclopentadienyl radicals and measured their IR spectra. The formation of these species is confirmed in our TOF mass spectrometer. We have also identified the formation of 9,10-dihydrofulvalene, the adduct from the reaction of two cyclopentadienyl radicals. Finally, we have used molecular beam mass spectrometry (MBMS) and factor analysis to demonstrate the formation of naphthalene from the pyrolysis of anisole.