Polycyclic aromatic hydrocarbon (PAH) formation in a diesel engine fueled with diesel, biodiesel and biodiesel/n-butanol blends

• Biodiesel–n-butanol blends were tested in a diesel engine for blends up to 40% n-butanol.
• Exhaust gas emissions and PAHs were extensively determined and analyzed.
• Most of the PAHs were emitted as semi-volatile compounds and not bound to particulate matter.
• Blending more than 20% n-butanol with biodiesel also increased the toxicity of PAH emission.

Polycyclic aromatic hydrocarbons (PAHs), described as unregulated emissions, are harmful to the environment, human health and engines, and need to be controlled and reduced. Two of the most common alternative fuel types are biodiesel and alcohols, and their effects on PAH formation are not well-known, currently. Since biodiesel (B) fuels do not contain aromatic components and are suitable for use in diesel engines, the use of biodiesel as the base fuel for studying the effect of n-butanol (Bu) on PAH formation is natural.With this purpose in mind, waste oil methyl ester, which is a compatible alternative fuel with diesel engines, was blended with 10%, 20% and 40% of n-butanol by volume, and BBu10, BBu20 and BBu40 blends were created. After determining fuel properties, these blends were tested in an ONAN diesel generator under four engine loads at 1800 rpm to quantify PAHs and to determined engine performance characteristics and regulated emissions. Separately, in order to quantify PAHs under the same engine conditions, GC–MS PAH speciation method was applied to real samples obtained from the engine. Cold flow properties were improved by adding n-butanol to biodiesel. For PAHs, it was shown that most of the aromatic hydrocarbons were emitted as semi-volatile compounds and were not bound to particulate matter. Blending more than 20% n-butanol into biodiesel also increased the toxicity of PAHs. No significant change in the aromaticity of the PAH emissions was found between blends.

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