A method has been developed for the chemical characterization of the heavy semivolatile HC fraction of diesel and biodiesel exhaust emissions. This method involves the capture of heavy compounds in TENAX-TA fiber and their subsequent analysis with GC/MS. Based on the data presented in this work, the following conclusions can be drawn. The biodiesel content increases the total amount of heavy HC emissions. These increments are more evident for aromatics and oxygenated compounds like aldehydes and ketones. This emission behavior could not be satisfactorily explained. The few studies available on detailed speciation of biodiesel fuel report large fluctuations in emission characteristics, which made impossible to find any clear trend. The source of this variation may be the engine type, test regime (transient or stationary), type of biodiesel fuel, etc. New compounds like aromatic esters, oxygenated aromatics and furans were found in biodiesel exhaust emissions. No information about these species in automotive engines is known. Additional research is needed before a reliable evaluation can be made. TENAX-TA fiber is not able to trap +2-ring aromatics because they are usually attached to PM (Particulate Matter), making necessary the speciation of individual compounds associated to particles for complete interpretation of semivolatile data. However, since the biodiesel content causes such a dramatic change in the character of heavy HC emissions, it is not recommendable to focus only on individual compounds in PM, but also to search for new compounds that were not already present in diesel exhaust. The satisfactory analysis of speciated semivolatile and PM compounds require an adequate conservation of species. Thereby, an acceptable method of conservation after sampling has to be developed.
Speciation of diesel exhaust hydrocarbons emissions using biofuels on an automotive engine
Spezifikation der Kohlenwasserstoffemissionen aus dem Auspuffgas eines mit Biokraftstoffen betriebenen Kraftfahrzeugdieselmotors
2006
16 Seiten, 4 Bilder, 4 Tabellen, 35 Quellen
Conference paper
English
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