Manganese sulfate effect on PAH formation from polystyrene pyrolysis

Polystyrene (PS) was pyrolyzed with/without manganese sulfate addition in a 100% N-2 environment at 600, 700 and 800 degrees C in a laboratory quartz reactor. The mole ratio of carbon (in PS) to Mn was 40/1. The gas-phase and liquid-phase polycyclic aromatic hydrocarbons (PAHs) were extracted with d ichloromethane (DCM) and subsequent;ly prepared for further analysis with a n HPLC equipped with a wavelength-scanning ultraviolet (UV) detector and a fluorescence (FL) detector. Virtually no char or coke residue was observed in the reactor at the end of the pyrolysis reaction. The addition of MnSO4 into the high-temperature pyrolysis of PS reduced PAH formation in ail liqu id and gas products. The transition metal-chelating oxidation mechanism pre viously used to explain soot reduction during combustion was not adequate f or explaining the results of PAH reduction via MnSO4 addition into the iner t pyrolysis. Furthermore, it is suggested that soot reduction via manganese salt addition into oxygen-rich combustion might not result only from the w ell-accepted chelating oxidation mechanism; rather, it might result from th e reduction of hydrocarbon species in the locally fuel-rich environment via manganese salt addition, as inferred from the reduction of PAH formation d uring inert pyrolysis with/without MnSO4 addition observed in this study. ( C) 1999 Elsevier Science B.V. All rights reserved.