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Communication Dans Un Congrès Année : 2022

Hydrotreatment of HTL micro-algal bio-oil over sulfide, nitride, and phosphide catalysts

Résumé

Microalgae seem to be a potential raw material for third-generation fuel production due to their high growth rate, the potential for CO2 fixation, and high lipids content which can provide a high biofuel yield. Hydrothermal liquefaction (HTL) is a thermochemical process that has been used for the conversion of microalgae in bio-oil. However, the HTL micro-algal bio-oil contains a high amount of heteroatoms such as N, O, and sometimes S which causes harmful emissions upon combustion and also reduced the quality of the fuel. Therefore, an upgrading step is required before the commercialization of this kind of biofuel to reach transportation fuel specifications. Being part of the Rafbioalg project (ANR-18-CE43-0009) that explores the production of biofuel from algae growth until fuel combustion with a LCA analysis of the all value chain, we investigated the catalytic upgrading step of the HTL algal oils. The whole algae, Chlorella Sorokiniana grew at CEA Cadarache, was converted to a bio-oil using a continuous reactor at 300 °C, under 10 MPa for 15 min at Liten laboratory in CEA Grenoble. The bio-oil was upgraded using a batch reactor at 375 °C under 10 MPa (H2), over NiWS/Al2O3, NiMoN, and Ni2P/Al2O3. The nitride and phosphide catalysts were prepared using a methodology described in the literature. The produced HTL and HDT oils were characterized by CHONS, XRF, ICP-OES, GPC–RID/DAD, 13C-NMR, SIMDIS, and GCxGC-MS/FID. The hydroconversion experiments performed with nickel phosphide showed the same conversion as an experiment without catalyst, indicating that, even though Ni phosphides have been reported in the literature as good candidate to replace sulfide catalysts, this active phase is not efficient for algal oil. However, the W sulfide and Mo nitride catalysts permitted to reduce O, N and S content and thus improved the quality of bio-oil. The main compounds formed after the upgrading step were C15, C16, C17, and C18 from carboxylic acids hydrogenation (HDO) or decarboxylation/decarbonylation (DCO). More than 60 wt% of upgraded bio-oil eluted on the diesel range, which corroborates fully the potential of microalgae as a feedstock for biofuel production. The degree of deoxygenation and denitrogenation were, respectively, 91% and 67% for sulfide catalyst, 93% and 46% for nitride catalyst, and 84% and 6% for phosphide. Therefore, NiWS/Al2O3 had a higher hydrodenitrogenation (HDN) ability than NiMoN and Ni2P/Al2O3 catalysts. GCxGC-MS/FID analysis revealed that fatty amides were first converted into nitriles and then in alkanes. The experiments performed over Ni2P/Al2O3 and without catalyst showed a family of nitriles that are completely converted with nitride and sulfide systems. Besides, it was also observed that NiWS/Al2O3 converted more cyclic nitrogen compounds, such as, pyrroles, indoles, and carbazoles than NiMoN which is associated with a higher hydrogenation ability of this catalyst, since these nitrogen molecules should be hydrogenated before the HDN reaction. The HHV increased from 36 MJ/kg in the HTL micro–algal bio-oil to 47 MJ/kg in the upgraded bio-oil over sulfide catalyst, and the average molar mass reduced from 363 to 265 g/mol indicating that heavy molecules were converted during the upgrading step.
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Dates et versions

hal-03681060 , version 1 (30-05-2022)

Identifiants

  • HAL Id : hal-03681060 , version 1

Citer

B. Magalhaes, R. Checa, C. Lorentz, P. Afanasiev, D. Laurenti, et al.. Hydrotreatment of HTL micro-algal bio-oil over sulfide, nitride, and phosphide catalysts. FCCAT 3 2022, May 2022, Ronce-les-Bains, France. ⟨hal-03681060⟩
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