In-Depth Interpretation of Mid-Infrared Spectra of Various Synthetic Fuels for the Chemometric Prediction of Aviation Fuel Blend Properties

Abstract

The aim of this work was to predict composition and nine selected physicochemical properties of fossil/synthetic aviation fuel blends by chemometric analysis of mid-infrared spectra. Therefore, infrared spectra of various mixtures with six different synthetic hydrocarbon fuels were recorded and comprehensively interpreted, supported by data from comprehensive two-dimensional gas chromatography–mass spectrometry analysis of these fuels. Deep insight has been gained on how individual blend components are differentiated in principal component analysis and how they influence physicochemical properties by means of partial least squares regression. A chemometric model has been established to determine the amount of an individual synthetic fuel in a blend with a precision of <1 vol % and a detection limit of <2 vol %. The quality of prediction of physicochemical properties is good enough to compete with results obtained by established test methods.

Review on the Relationship Between Liquid Aerospace Fuel Composition and Their Physicochemical Properties

“…Furthermore, Shi et al [55] used two-dimensional GC with MS and flame ionization detector (GC × GC-MS/ FID) to accurately measure the aviation fuel composition, which was sorted into 10 hydrocarbon classes and carbon numbers (C 7 -C 19 ); they further developed the quantitative composition-property relationship of aviation fuels by different statistical algorithms, including weighted average (WA) method, partial least squares (PLS) analysis, genetic algorithm, and modified WA method. Moreover, the PLS regression models based on near-IR or Fourier transform IR spectroscopy (FT-IR) spectra can provide a practical method to predict fuel density [56][57][58]. Al-Nuaimi et al [19] predicted the density of hydrocarbon mixture with mass fractions of n-, iso-, and cyclo-paraffins (Entry 13, Table 2).…”

“…Al-Nuaimi et al [19] proposed several multiple nonlinear correlations between the freezing point and the composition of fuel blends composed of n-, iso-and cyclo-paraffins to predict the freezing points of blending fuels (Entry 9, Table 5). Analogous to the density and NHOC, PLS regression method based on FT-IR spectra can also predict the fuel freezing point [58]. (11) To simplify the relationship between the freezing point and molecular structure of aviation fuels, we attempted to correlate the freezing point with H/C molar ratios and M; however, we failed to obtain a suitable model probably given the difficulty of reflecting molecular symmetry and intermolecular forces [55,88].…”

“…12a, b). Scheuermann et al [58] reported that the introduction of aliphatic compounds with a low boiling point reduces the fuel flash point, whereas hydrocarbon fuels containing high-boilingpoint aromatics exhibit high flash points. Typically, the flash point of iso-paraffins is lower than that of n-paraffins, and iso-paraffins with more molecular branches have a lower flash point at a given carbon number, e.g., 2,3-dimethylpentane (− 6.2 °C) versus 2,2,4-trimethylpentane (TMP) (− 12.2 °C) [104].…”

Future-Oriented Experimental Characterization of 3D Printed and Conventional Elastomers Based on Their Swelling Behavior

“…Furthermore, the competing technologies need further improvements to become competitive, but finally a mix of technologies must be considered and tailored to the respective applications. Liquid aviation fuels in a chemical view are composed of different hydrocarbon classes: linear alkanes, branched isoalkanes, cycloalkanes, and aromatics [29]. The fuel properties are highly dependent on the chemical composition and the distribution of the hydrocarbons.…”

“…Applied Research Associates (ARA) produces the synthetic jet drop-in fuel ReadiJet™ used here. Chemically, it is a complex mixture of hydrocarbons similar to the conventional kerosene Jet A-1 with an aromatics content of 21.2 vol% measured according to Standard ASTM D1319-20a [43] and a density of 0.823 g cm −3 [29,30] and is used as the immersion fluid.…”