Heteroatomic jet fuel components: Lichen substances as fuel component and potential additives

Abstract

This article presents chemical analysis of jet fuel (Jet A-1) heteroatomic fuel components with identification of an antioxidant lichen substance in methanol extracted fuel samples. Thermal stressing of jet fuel produces soluble macromolecular oxidatively reactive species (SMORS) and heteroatomic deposits. SMORS are deposit precursors and elementary heteroatomic units containing unsaturated and aromatic hydrocarbons. Fuel additives such as antioxidants can inhibit SMORS and deposit formation within limited heating residence time and temperature range. Jet A-1 was thermally stressed in the autoxidation regime (150 to 300 0C) followed by spectroscopic analysis. Thermally stressed jet fuel static tests electrospray ionization mass spectra (ESI-MS) show higher molecular weight compounds in the mass range 300-1000 Da compared with unstressed fuel samples supporting deposition. Jet A-1 samples were analyzed by electrospray ion source mass spectrometry (ESI-MS), Fourier transform infrared (FTIR) and 13C nuclear magnetic resonance (NMR) spectroscopy. FTIR bands for oxygen containing species reveal the presence of alcohol, phenol and ether groups. 13C nuclear magnetic resonance (NMR) standard and distorsionless enhancement polarization transfer (DEPT 135) spectra recorded heteroatomic alkoxy species in both unstressed and thermally stressed fuel samples. Natural products polyphenols and lichen derived oxygenated compounds are excellent antioxidants. A new perspective of using lichen substances as fuel additives emerged in this study. Exploring further, natural products extraction methods optimization remains a key challenge and advantages of polyphenolic lichen acids as potential fuel and chemical additives are discussed.