Mild Hydrothermal Pretreatment of Microalgae for the Production of Biocrude with a Low N and O Content

Montero-Hidalgo, Miriam; Espada, Juan J.; Rodríguez, Rosalía; Morales, Victoria; Bautista, Luis Fernando; Vicente, Gemma

doi:10.3390/pr7090630

Cited by 5 publications

(4 citation statements)

References 27 publications

(63 reference statements)

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“…HTL allows for the biofuel production from wet microalgae without a drying pre-treatment [5] and it tolerates the conversion of the whole microalga biomass, also including the low-lipid microalgal biomass which normally has higher growth rates [3,[6][7][8][9]. Moderate temperatures (200-380 • C) and high pressures (10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25) and microalga:water ratios within the range 5%-15% are commonly used in HTL [10,11]. HTL yields a solid residue or biochar, a gaseous phase and two liquid fractions (aqueous and organic).…”

Section: Introductionmentioning

confidence: 99%

“…The HTL biocrude can be upgraded with a conventional catalytic hydrotreatment [15], but novel processes involve the modification of the HTL process. Thus, some recent investigations deal to the HTL in two stages, where the N and O contained in the initial biomass is removed at low temperatures in a pre-treatment and the solid phase obtained in this first stage is transform to a low N and O content biocrude in the following HTL step [6,16,17]. Other authors have studied the use of co-solvents such as ethanol [18,19], obtaining high biocrude yields at lower temperatures.…”

Section: Introductionmentioning

confidence: 99%

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Hydrothermal Liquefaction of Microalga Using Metal Oxide Catalyst

et al. 2019

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The yield and composition of the biocrude obtained by hydrothermal liquefaction (HTL) of Nannocloropsis gaditana using heterogeneous catalysts were evaluated. The catalysts were based on metal oxides (CaO, CeO 2 , La 2 O 3 , MnO 2 , and Al 2 O 3 ). The reactions were performed in a batch autoclave reactor at 320 • C for 10 min with a 1:10 (wt/wt) microalga:water ratio. These catalysts increased the yield of the liquefaction phase (from 94.14 ± 0.30 wt% for La 2 O 3 to 99.49 ± 0.11 wt% for MnO 2 ) as compared with the thermal reaction (92.60 ± 1.20 wt%). Consequently, the biocrude yields also raised in the metal oxides catalysed HTL, showing values remarkably higher for the CaO (49.73 ± 0.9 wt%) in comparison to the HTL without catalyst (42.60 ± 0.70 wt%). The N and O content of the biocrude obtained from non-catalytic HTL were 6.11 ± 0.02 wt% and 10.50 ± 0.50 wt%, respectively. In this sense, the use of the metal oxides decreased the N content of the biocrude (4.62 ± 0.15-5.45 ± 0.11 wt%), although, they kept constant or increased its O content (11.39 ± 2.06-21.68 ± 0.03 wt%). This study shows that CaO, CeO 2 and Al 2 O 3 can be promising catalysts based on the remarkable amount of biocrude, the highest values of C, H, heating value, energy recovery, and the lowest content of N, O and S.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Hydrothermal Liquefaction of Microalga Using Metal Oxide Catalyst

et al. 2019

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“…Bio-oil product quality and yield depend on reaction conditions (temperature and reaction time), feedstock characteristics, and presence of a catalyst. − HTL bio-oil upgrading in conventional refineries to substitute fossil crude is hindered by its higher N and O contents. O and N are naturally present in the original feedstock and depending on the operating conditions can be transferred to bio-oil during HTL. ,, This decreases the bio-oil heating value and increases hydrogen consumption during the hydrotreating step to remove O and N. − HTC at low temperatures can partition N into the aqueous phase (AP) while retaining C in the solid hydrochar. ,, On the one hand, N in the APespecially in its inorganic form, e.g., NH 3 –N, NO 2 –N, and NO 3 –N– can be recovered as a fertilizer. , On the other hand, the C-rich hydrochar can be used as a feedstock in a subsequent HTL step to produce a bio-oil with lower N content.…”

Section: Introductionmentioning

confidence: 99%

Direct and Two-Stage Hydrothermal Liquefaction of Chicken Manure: Impact of Reaction Parameters on Biocrude Oil Upgradation

Vadlamudi,

Pecchi,

Sudibyo

et al. 2024

ACS Sustainable Chem. Eng.

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Hydrothermal liquefaction (HTL) provides advantages to traditional methods (e.g., landfilling and composting) to convert wet biomass waste (e.g., agricultural residue) into energy-rich biocrude oil (bio-oil) and nutrient-rich aqueous phase. The challenge associated with these feedstocks lies in their high N and O contents. These heteroatoms are fixed into bio-oil produced from direct-HTL, making it infeasible as a drop-in fuel due to the low calorific value. To address these challenges for chicken manure, this study evaluated two thermochemical conversion approaches: (1) direct-HTL and (2) a two-stage process of hydrothermal carbonization (HTC) followed by HTL. The second scenario aimed to extract most N and oxygenates into the aqueous phase, producing C-rich bio-oil from the second stage (i.e., HTL). Experiments were conducted at different temperatures (160− 350 °C), reaction times (30−60 min), and feedstock pHs (4−9). Acidic conditions were achieved by adding acetic acid as a catalyst, whereas the natural feedstock pH of chicken manure was around 9. Experiments revealed that the bio-oil properties improved from two-stage processing of acidic feedstock with pH = 4−5 with HTC conducted at 190 °C for 30 min and HTL at 300 °C for 30 min. Due to reduced O and N contents, the higher heating value of bio-oil increased from 32−33 (direct-HTL) to 37−38 MJ/kg (twostage). Nonetheless, the overall C recovery in the bio-oil decreased from ∼35 to ∼20% compared with direct-HTL. This shows a trade-off between removing as many heteroatoms as possible and maximizing C recovery in bio-oil. A mechanistic study revealed the underlying degradation mechanisms (dehydration, decarboxylation, and denitrogenation) in direct-HTL and two-stage along with inhibition of Maillard reaction under the acidic environment.

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“…Hydrothermal liquefaction has proven to be an attractive process for the production of biofuels from microalgae, rendering biocrude (the liquid organic phase), aqueous phase compounds, solid residue, and gas phases, as illustrated in three works published in this Special Issue by Dr. Vicente's research group. In the first, Megía-Hervás et al assess the temperature, reactor loading and time of the hydrothermal liquefaction of the microalga Nannochloropsis gaditana at mild temperatures in order to reduce the N and O content in the biocrude and to maximize the yield of the pretreated biomass [10]. Subsequently, Sánchez-Bayo et al improve the hydrothermal liquefaction of the same microalgae using heterogeneous catalysts [11].…”

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confidence: 99%