Toward an optimal formulation of alternative jet fuels: Enhanced oxidation and thermal stability by the addition of cyclic molecules

Abstract

Oxidation and thermal stability (OTS) are key concerns for the development of alternative jet fuels, as they imply complex physical and chemical phenomena such as autoxidation, pyrolysis, cooxidation reactions and transfer-limitation. The OTSof an alternative aviation fuel was characterized using PetroOxy test from 120-160°C and JFTOT test at 325°C. The alternative jet fuel is a Synthetic Paraffinic Keroseneproduced from Hydroprocessed Esters and Fatty Acids (HEFA-SPK). Results showed a high thermal stability of HEFA-SPK. However, a low oxidation stability was also observed. The oxidation stability of8model cyclicmolecules was evaluated. Results allowed to estimate the influence of the molecular structure of cyclic molecules on liquid phase reactivity involving the number and the hydrogenation of the aromatic rings and the number and chain-length of the aromatic alkyl groups.The addition of several alkylbenzenes increased almost linearly the induction period of HEFA-SPK. Tetralin and decalin acted as inhibitors of the radical chain mechanism at low concentration, although having inherently low oxidation stability. Besides offering a better oxidation stability, the addition of specific low fractions of several alkylbenzenes, tetralin and decalin to HEFA-SPK allowed to achieve a good thermal stability as well. These molecules represent good candidates to improve OTS of HEFA-SPK. This work opens the way for the development of future fit-for-purpose formulations of alternative jet fuels with an increased fraction of renewables.

Structure–Reactivity Relationships in Fuel Stability: Experimental and Kinetic Modeling Study of Isoparaffin Autoxidation

“…Thus, within the framework of the full comprehension of fuel stability, this work confirms and extends previous work performed on the autoxidation of normal parraffins 12,[15][16][17][18][19] to isoparaffins 17,20,21 . The present study is in-line with others autoxidation studies performed at IFPEn on aromatics 14,22 and naphthenes 22 . All these studies aim at improving the comprehension of the autoxidation of each chemical family present in fuels.…”

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

“…Thermal-oxidative stability refers to the resistance of aviation fuels to self-oxidation, decomposition, and undesirable carbon deposit formation, which can be attributed to several liquid-phase oxidation reactions, at the operating temperature for a short time. Thermal-oxidative stability can be described by thermal and oxidative stabilities, which can be assessed by the jet fuel thermal oxidation stability test (JFTOT) described in ASTM D3241 and the rapid smallscale oxidation test defined in ASTM D7545, respectively [5,109].…”

“…DeWitt et al [110] proposed that the oxidation and molecular growth of aromatics are the major routes for the deposit formation of SPK/aromatic fuel blends; these authors also stated that less steps are required for the growth of aromatics with high molecular size into insoluble deposit precursors. Ben Amara et al [109] measured the thermal stability of HEFA aviation fuel with the addition of different aromatics by JFTOT test at 325 °C. As illustrated in Fig.…”

“…Paraffins have a poor oxidation stability, and thus, bio-jet fuels have relatively poorer oxidative stability than conventional jet fuels owing to their higher paraffin content [5]. For example, the IP (measured under 7 bar of oxygen pressure at 140 °C according to ASTM D7545) of HEFA (1 h) is considerably lower than that of Jet A (2.3 h) [109]. Chatelain et al [118] reported that the IP of n-paraffins drastically decreases with the increase in carbon chain length and levels off at carbon numbers above 12 (Fig.…”

Tendências E Oportunidades Nas Pesquisas Em Biocombustíveis

“…O desenvolvimento de novas metodologias de análises, o investimentos em laboratórios de certificação de biocombustíveis, estudos de viabilidade e scale up de novos processos e estudo de compatibilidade de biocombustíveis com materiais, sobretudo polímeros e elastômeros. Um trabalho da França em parceria com uma empresa fabricante de aeronaves apresentou um estudo de compatibilidade entre materiais atualmente utilizados em aeronaves e materiais alternativos, visando uma formulação ótima desses biocombustíveis (Amara et al, 2016).…”