Communication Dans Un Congrès Année : 2023

Micro-algae to biofuels: catalytic upgrading of algal oils from hydrothermal liquefaction

Résumé

In order to limit the use of fossil resources, fuel production from renewable resources has become a priority, especially for aviation. Among sustainable bio-resources, microalgae represent an attractive alternative to provide carbon molecules thanks to their fast-growing rate and the high lipid content. In addition, microalgae can be easily transformed into a crude oil by the hydrothermal liquefaction (HTL) process. After HTL process, microalgal oils still contain a large quantity of O-, N- or S- compounds that have to be reduced to be used as fuel. The main components of HTL microalgal oil are the C16-C18 fatty acids issued from the lipids conversion during the HTL process. Those acids, in addition to other components like amides, alkenes, esters, or alcohols are not compatible with transport fuels and need to be upgraded to hydrocarbons. In this work, we propose catalytic upgrading, including deoxygenation, denitrogenation, and desulfurization of an HTL oil obtained from Chlorella vulgaris microalga with various supported catalysts among NiW(Mo) sulfide or nitride and Ni phosphide having hydroconversion ability. During the catalytic upgrading, fatty acids were converted readily to the corresponding alkanes by hydrodeoxygenation (HDO) or decarboxylation/decarbonylation (DCO). The refractory compounds are fatty amides, nitriles, and the various heterocyclic nitrogen molecules coming from proteins. Supported Ni2P catalysts promoted the DCO route, while NiMoN/Al2O3 promoted the HDO pathway. Alumina-supported NiWS catalyst was the most performant solid for the studied reaction, producing a hydrotreated oil with the best higher heating value (HHV), the lowest aromaticity degree, and the lowest average molar mass. The most refractory remaining are cyclic nitrogen compounds such as indoles, pyrroles, and carbazoles. The biofuels obtained with the various catalysts fall mainly in the diesel and jet-fuel ranges as observed by SimDist. For instance, for NiWS/Al2O3 catalyst, 66 wt% of the liquid is recoverable as traditional fuels. Moreover, with this catalyst, a higher reaction temperature (400°C) allowed increasing the jet fuel and diesel fraction, reaching a total of 80 wt%. The screening of catalysts has thus revealed the alumina-supported NiWS catalysts as a robust and performant system to upgrade micro-algal oils into biofuels.

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Dates et versions

hal-04619679 , version 1 (21-06-2024)

Identifiants

  • HAL Id : hal-04619679 , version 1

Citer

B. da Costa Magalhães, D. Laurenti, R. Checa, C. Lorentz, P. Afanasiev, et al.. Micro-algae to biofuels: catalytic upgrading of algal oils from hydrothermal liquefaction. ACS Fall 2023, Aug 2023, San Francisco, United States. ⟨hal-04619679⟩
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