Measurement of soot mass and PAHs during the pyrolysis of C2[sbnd]C4 alcohols at high temperatures

Abstract

Particulate matter (PM) is emitted from a range of combustion sources, can vary greatly in properties, and is able to penetrate deep into the human lungs, conveying carcinogenic PAHs present on the particle surface. Alcohol based biofuels have been shown to potentially reduce PM emissions when displacing fossil fuels. To improve understanding of the influence of fuel bound oxygen on and the relative toxicity of PM, this paper investigates quantitatively the soot mass and PAHs produced from the pyrolysis of ethanol, 1-propanol, 2-propanol,1-butanol, and 2-butanol in a laminar flow reactor. The pyrolysis of alcohol fuels and collection of soot-bound and gas-phase PAH was carried out between 1323 and 1623 K at a fixed carbon atom concentration in nitrogen. Accelerated solvent extraction (ASE) was used to extract soot bound PAH and gaseous species captured on XAD resin, with speciation and quantification of PAHs undertaken using GCMS. Of the primary alcohols, the highest and lowest masses of soot were observed for 1-butanol and ethanol respectively, while secondary alcohols generated more soot mass than corresponding primary alcohols. An effect of hydroxyl group position on the total PAH distribution in the gas and particulate-bound phases was observed within the temperature range of 1323 to 1423 K. At 1323 K, 1-propanol produced approximately three times more particle phase (PP) PAH concentration than 2-propanol. Amongst the fuels tested, 1-propanol produced the highest level of carcinogenic PAHs at 1323 K, while for all C3 and C4 fuels the toxicity equivalence factor decreased with increasing pyrolysis temperature.