Understanding the nature and origin of fuel powertrain deposits by the use of high resolution chromatography and mass spectrometry

Abstract

Recent changes to diesel fuel specifications and engine design to meet new legislative mandates have coincided with an increase in the number of reports detailing fuel delivery system failures. These failures may occur due to fuel filter blockages and can result in increased emissions, reduced efficiency, and engine failure. The nature and origin of these fuel filter plugging incidences is of great interest to the petrochemical industry, as new mitigation strategies to prevent fuel delivery system failures are investigated and developed. Multiple chromatography and mass spectrometry analytical approaches were developed for the identification of analytes present in diesel fuel and filter material. The novel approaches herein were successful in simplifying analysis protocols and identifying trace level problematic material; further adding to the understanding of fuel filter plugging incidences. Thermal desorption (TD) style sample introduction methods were developed, enabling straightforward and efficient analysis of fuel filters. These methods were developed with a focus on sustainability and were proven to be faster and more sustainable than existing approaches, whilst maintaining analytical efficacy in identifying analytes of interest. Problematic species known to contribute to fuel filter fouling such as glycerol, free fatty acids (FFAs), monoacylglycerides (MAGs) and fatty acid methyl ester (FAME) oxidation products were identified. The novel use of comprehensive two-dimensional gas chromatography – mass spectrometry (GCxGC-MS) for the analysis of fuel filters was demonstrated. The GCxGC-MS methods developed allowed the investigation of IP 618 filters, whereby analysis of these particular fuel filters would not have been possible using existing analytical methods. It was possible to identify FAMEs, FFAs, glycerol and FAME oxidation products using GCxGC-MS. The critical combination of orthogonal and complementary techniques, including GCxGC-MS, ultra-high performance supercritical fluid chromatography - mass spectrometry (UHSFC-MS) and high-resolution MS, was demonstrated. This multi technique approach enabled the identification of volatile, semi-volatile and non-volatile biodiesel related contaminants to inform on the nature of insoluble material formation that may cause fuel filter blocking. A novel approach for the detection of ACCUTRACE™ S10 in fuel using a Waters™ RADIAN ASAP instrument was developed; the addition of solid ammonium acetate was found to improve the sensitivity of the method. This method is a promising candidate for roadside detection of the illegal use of rebated fuel marked with 2.5 ppm ACCUTRACE™ S10. Application of widespread roadside detection units may aid HMRC in deterring the illegal use of rebated fuel in the UK. Possible routine analytical approaches were explored for the detection of the new fuel marker used in the EU, ACCUTRACE™ Plus. The need for robust fuel markers to ensure an effective deterrent against the use of rebated fuel was highlighted.

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Identifiers

ORCID for John Langley: orcid.org/0000-0002-8323-7235

ORCID for Julie Herniman: orcid.org/0000-0003-4834-1093

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