GC-MS determination of polycyclic aromatic hydrocarbons evolved from pyrolysis of biomass
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A method for the determination of polycyclic aromatic hydrocarbons (PAHs) in liquid pyrolysate of biomass (bio-oil) was developed with attention to greenness along with accuracy. Bio-oil obtained from preparative pyrolysis at 500 °C of poplar wood as representative biomass matrix was dissolved into acetonitrile (ACN). An aliquot of the ACN solution (0.1 mg bio-oil) was added with water (20% v/v) and spiked with perdeuterated standards, then PAHs were extracted with n-hexane and separated from phenolic interferents by silica gel solid-phase extraction (SPE). All 16 priority PAHs were detected at concentrations between 7.7 µg g−1 (naphthalene) and 0.1 µg g−1 (benz[a]anthracene) with RSD in the 6–23% range. Recovery of perdeuterated acenaphthene, phenanthrene and chrysene was 84, 93 and 90%, respectively. Results obtained from the analysis of bio-oil were used to evaluate the performance of analytical pyrolysis conducted with a heated platinum filament in off-line configuration. Two sampling procedures were compared: (1) sorption onto silica gel followed by elution with n-hexane (Py-SPE), (2) dynamic solid-phase micro-extraction followed by fibre cleanup with aqueous ammonia (Py-SPME). Emission levels of priority PAHs could be determined by Py-SPE with RSD in the 13–45% range, while Py-SPME was unsatisfactory for quantitation. Emission levels determined by Py-SPE fell in the 6.4–0.1 µg g−1 range slightly higher than those calculated from bio-oil analysis. Both Py methods were adequate for screening purposes to assess the effect of catalysts on PAH formation. In particular, they agreed to show that the content of PAHs expected in bio-oil increased dramatically when pyrolysis was conducted over HZSM-5 zeolite.
KeywordsBiomass Fuel GC-MS Polycyclic aromatic compounds Pyrolysis
- 3.Cirad, Aston University, BFH, An assessment of bio-oil toxicity for safe handling and transportation, Final Technical Report, Part I, 2003 (available on-line at www.pyne.co.uk).