Rational Formulation of Alternative Fuels using QSPR Methods: Application to Jet Fuels
Abstract
Alternative fuels are a promising solution for road transport but also for aircraft. In
the aviation field, a huge amount of work has been done in the past years with the
approval to use up to 50 % by volume of SPK (Synthetic Paraffinic Kerosene) in blends with
conventional fossil Jet A-1. SPK are Fischer-Tropsch (FT) fuels but also Hydroprocessed
Esters and Fatty Acids (HEFA). However, these alternative fuels can have different
chemical properties depending on the process used for their production. These properties
include normal to iso paraffin ratio, carbon chain length and level of branching. R&D studies of alternative fuels are based on the evaluation of products coming from
identified production processes. However, it appears that a better way of studying them
could be firstly to determine the best chemical composition regarding aviation problems
and secondly to find the best process and finishing process in order to obtain such a
product. The objective of this work is to design a tool that aims to guide the future formulation
of alternative fuels for aviation through the prediction of targeted physical properties.
Thus, it is proposed to apply a methodology that identifies relationships between the
structure and properties of a molecule (QSPR for Quantitative Structure Property
Relationship), with the aim of establishing predictive models. These models will be built
for hydrocarbons (normal and iso paraffins, naphthenes, aromatics, etc.) and oxygenated
compounds (esters and alcohols). For aviation, oxygenated compounds are not considered as
a drop-in fuel. It could be seen as a disruptive solution in a long term view. There are
concerns with oxygenates in aviation that are covered in this paper such as the flash
point but others such as the energetic content, the water affinity that are not taken into
account in this paper. The properties currently studied are flash point, cetane number,
density and viscosity. The data sets will contain data from the literature, from
experimental measurements and from molecular simulations for complex molecules. The
interest of such models in the selection of molecules can be shown for example by the
trade-off between cold flow properties and density of paraffinic compounds. If the carbon
chain length is too high, the cold flow properties are compromised. One solution can be to
increase branching or incorporate fuel base with good cold flow properties such as
naphthenic or aromatic compounds. However, this leads to a decrease in density below the
jet fuel specification. Again, using naphthenic of alkyl-aromatic compounds produced from
biomass can help.
Domains
Physics [physics]
Origin : Publication funded by an institution
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