There has been significant interest in recent years in the development, certification and use of alternative (non-petroleum) aviation fuels.  The motivation for this has been driven by many factors, including the growing demand and reduced supply of petroleum-derived fuels, cost volatility, and desire for a reliable domestic fuel supply.  Extensive laboratory and full-scale testing has resulted in the approval of synthetic paraffinic fuels for use as a blending feedstock (up to 50% by volume) in both commercial and military aviation fuels.  This includes Synthetic Paraffinic Kerosene (SPK) produced via Fisher-Tropsch synthesis and Hydroprocessed Esters and Fatty Acids (HEFA) derived from plant oils and animal fats.  These SPK and HEFA blend stocks are predominantly paraffinic (normal and iso-) in composition and contain minimal aromatic and heteroatomic compounds.  Such paraffinic blend stocks exhibit excellent thermal-oxidative stability characteristics and significantly reduced particulate matter propensity during combustion, which is attributable to the lack of aromatics and heteroatomic compounds.  However, the lack of these compound classes results in blend stocks with poor lubricity and insufficient material compatibility/seal swell characteristics.  As a result, current fuels containing synthetic blend stock require a minimum total aromatic concentration of 8% by volume. This constraint can reduce the beneficial aspects of the neat paraffinic fuels, resulting in behavior which is generally consistent with petroleum-derived fuels.Significant effort is currently being made to improve the understanding of individual species and compound classes which strongly affect material compatibility and lubricity; these studies have primarily focused on the role of aromatic type compounds.  The goal of the studies is to identify potential aromatic compounds and the minimum total aromatic concentration that, when added to synthetic blend stocks, will satisfy required fit-for-purpose fuel properties.  This approach has the potential to produce a fuel which can maximize the beneficial aspects of the synthetic feedstocks.  Several studies related to the effect of aromatic type and concentration on particulate matter production have previously been performed and shown reduced emissions can be realized with low aromatic concentrations (<10%).  However, only limited studies have been performed investigating the effect of aromatic addition on the thermal-oxidative stability of synthetic fuels.  In this effort, the effect of aromatic type and concentration on the oxidative-stability of synthetic fuels was investigated using a single-tube flowing reactor system, a Quartz Crystal Microbalance (QCM) reactor and a Jet Fuel Thermal Oxidation Test (JFTOT) apparatus.  These studies will provide insight into the potential thermal stability impact of blending aromatic compounds into alternative fuels.  The experimental methodologies employed and results and understanding obtained will be presented.

Effect of aromatics addition on the thermal-oxidative stability of alternative jet fuels

244th National Meeting (2012)

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