Carburant aviation

Résumé

Suivant le type de propulsion (turbines, moteurs à pistons), les aéronefs brûlent différents types de carburants, dits « carburants aviation ». Carburants basés sur le kérosène Les moteurs d'aviation à turbine (turboréacteurs, turbopropulseurs) utilisent des carburants à base de kérosène. En aviation civile, le carburant de ce type le plus répandu est le Jet A-1, défini par la norme internationale AFQRJOS (en), qui gèle au minimum à (car c'est la limite inférieure définie par l'AFQRJOS). Aux États-Unis, il existe également un carburant Jet A, dont la fabrication est un peu moins coûteuse mais qui gèle à une température inférieure à . La norme américaine de carburant militaire JP-8 est proche du , à quelques additifs près. Pour un usage en environnement froid, notamment dans le nord canadien, il existe aussi une spécification Jet B ; ce carburant inclut, en sus du kérosène, une fraction d'essence (coupe naphta), ce qui lui permet de rester liquide à de plus basses températ

Source officielle

https://fr.wikipedia.org/wiki/Carburant_aviation

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Catalytic Upgrading of Biomass-Derived Carboxylic Acids to Fuels and Chemicals

Jher Hau Yeap

Our reliance on fossil fuels, which is unsustainable due to dwindling reserves, has led to various environmental issues. Lignocellulosic biomass could serve as a renewable source of carbon and energy for the production of fuels and chemicals. While several valorization routes of biomass-derived sugars (via furans or sugar alcohols) exist, the upgrading of the biological carboxylate platform is relatively unexplored, mainly due to historical focus on ethanol production via fermentation. Research on biomass-derived carboxylic acids could increase our knowledge on carboxylic acid upgrading and open up new avenues towards sustainable production of fuels and chemicals from lignocellulosic biomass. The production of olefins from carboxylic acids via tandem hydrogenation/dehydration was carried out, with olefin selectivities > 90% at close to 99% conversion of carboxylic acids using a Cu/SiO2-Al2O3 catalyst. Interestingly, a sudden selectivity switch from olefins to predominantly alkanes was observed at full conversion. Using various intermediate products and catalyst surface studies, this selectivity switch phenomenon was ascertained to originate from the adsorption of small amounts of carboxylic acid on the catalyst surface, which prevented the binding and subsequent overhydrogenation of olefins. This finding suggests that carboxylic acids has potential to be used in influencing product distributions of other catalytic reactions, especially if selective double bond preservation is required. This phenomena could also be used to explain the difference in catalyst performance observed when using commercial model compounds versus real biomass-derived feed, given the prevalence of carboxylic acid impurities in biomass-derived streams. This route represents a single-step upgrading of carboxylic acids to olefins with no loss in carbon efficiency and without use of expensive stoichiometric reagents, which is important for economical production of bulk chemicals from lignocellulosic biomass. In parallel, a study on carboxylic acid upgrading via single-step ketonization/cascade aldol condensation to an aviation fuel additive was performed over Cu/ZrO2. Biomass-derived acetic acid and butanoic acid was converted to an organic oil composed of aromatics and cycloalkenes with a carbon number range of C8 - C16 at mass yields of around 20 wt %. By-products include gaseous hydrocarbons (mainly propylene) and water resulting from condensation. This organic oil represents up to 96% deoxygenation of the starting carboxylic acids, and has been tested to be compatible as a 10 vol % blend with Jet A-1 fuel in terms of specific energy and distillation properties. While previous research on ketonization and aldol condensation have performed the reactions separately, this route combines both in a single step to upgrade short carboxylic acids to long chain hydrocarbons, while valorizing the often neglected acetate fraction of biomass. This study shows a combination of C-C coupling and extensive deoxygenation, both crucial towards successful upgrading of lignocellulosic biomass to fuels.

EPFL2019

Chargement

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In many plant species, the acetate fraction is the fourth most prominent fraction by weight after cellulose, hemicellulose and lignin, and can be easily extracted as a single stable molecule, acetic acid, at high yields. Despite this, upgrading the acetate fraction of biomass has received very limited attention. Here, we demonstrate a valorization route for the acetate fraction as well as mixtures of acetic acid and other volatile fatty acids produced from the polysaccharide fraction. Aqueous solutions of acetic acid, including solutions produced during steam explosion pretreatment and subsequently purified can be upgraded at high selectivity to a valuable mixture of aromatics, substituted cycloalkenes and gas olefins in a single step using Cu/ZrO2. The catalyst displays remarkable stability despite the presence of acids, water and other biomass-derived impurities. We also show that acetic acid can be further valorized over the same catalyst by converting it in the presence of butanoic acid that was produced in a consolidated bioprocess from the same pretreated wood that was the source of the acetic acid. In this case, the acetic acid rapidly ketonizes with the butanoic acid and the resulting beta-ketones further condense to form aromatics and cycloalkenes with a higher average carbon number than those produced solely from acetic acid. Overall, our process yields a biomass-derived organic oil consisting of aromatics and cycloalkenes that spontaneously separates from water, can be tuned by varying the incoming mixture of carboxylic acids and has suitable properties for being used as a direct blend with aviation fuel.

2019

Chargement

With the rapid growth and increased consumption of biofuels worldwide, and the multitude of policy decisions supporting this expansion, growing concerns about the biofuels sustainability have arisen. Therefore, the European project "ITAKA", aiming at supporting the development of aviation biofuels in an economically, socially, and environmentally sustainable manner has devoted considerable effort to take sustainability into account, in a quantitative and qualitative manner. More precisely, a robust assessment of a lifecycle greenhouse gas (GHG) calculation for the produced bio jet fuel have been set up, using the RSB EU RED methodology. This pathway includes feedstock production, feedstock processing, biofuel production, biofuel distillation, and all transport steps involved. A significant reduction in GHG emissions (up to 66%) has been demonstrated.

2016

Chargement

Catalytic Upgrading of Biomass-Derived Carboxylic Acids to Fuels and Chemicals

Jher Hau Yeap

EPFL2019