State-of-the-art monitoring of fuel acidity

Development of a novel iridium oxide (IrOx) based acidity sensor for off-line monitoring of fuel acidity is described. The sensor works in the potentiometric mode using an IrOx electrode as an indicating electrode and a Ag/AgCl or Ag/Ag2O—reference electrode. The data show that the IrOx sensor responds to compounds present in fuel that have acid–base character. Using an off-line IrOx sensor, it is possible to determine the acidity of different fuels and discriminate between unstressed and thermally stressed fuels. It is possible to correlate the response of an IrOx sensor with the total acid numbers of different fuels. Experimental results also indicate that the low fuel conductance, the material used for sensor encapsulation, and/or the type of reference electrode may influence the response time of the IrOx sensor. Finally, the IrOx response has been demonstrated to be faster, better defined, more accurate and more reproducible than a glass electrode response for titrations of non-aqueous solutions.