- Email: [email protected]
Selective extraction of neutral lipid from wet algae paste and subsequently hydroconversion into renewable jet fuel
Accepted Manuscript Selective extraction of neutral lipid from wet algae paste and subsequently hydroconversion into renewable jet fuel Chao Ju, Feng Wang, Yong Huang, Yunming Fang PII:
S0960-1481(17)31130-8
DOI:
10.1016/j.renene.2017.11.028
Reference:
RENE 9430
To appear in:
Renewable Energy
Received Date: 7 November 2016 Revised Date:
25 July 2017
Accepted Date: 11 November 2017
Please cite this article as: Ju C, Wang F, Huang Y, Fang Y, Selective extraction of neutral lipid from wet algae paste and subsequently hydroconversion into renewable jet fuel, Renewable Energy (2017), doi: 10.1016/j.renene.2017.11.028. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
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Ethanol Neutral lipids
Water
Hexane
Ethanol
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Polar lipid
Wet algae paste
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Neutral lipids
Others
Polar lipids
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Pt/meso-ZSM-5
Neutral Jet fuel lipid Hydro-cracking
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Selective extraction of neutral lipid from wet algae paste and
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subsequently hydroconversion into renewable jet fuel ∗
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National Energy Research Center for Biorefinery, Beijing University of Chemical Technology, 100029, Beijing, China
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Abstract: Wet algae paste, after harvested, was converted into renewable jet fuel through
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selective extraction and subsequent hydroconversion without further purification. A
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fractional extraction method based on ethanol and hexane starting from wet algae was
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firstly designed and investigated. The oil recovery was as high as 90 wt.% of lipid after
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three extraction cycles. Such a method results in fractional extraction of polar lipid and
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neutral lipid separately from wet algal biomass. The obtained neutral lipid rich fraction
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has very low metal content, in which the Ca, Mg, and Cu contents are 2, 0, and 3 mg/kg,
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respectively. It can be converted into jet fuel range paraffin by one-step hydrocracking
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over Pt/Meso-ZSM-5 catalyst directly. The freeze point, flash point, and energy density
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of the obtained jet fuel are -57 °C, 42 °C, and 45 MJ/kg, respectively, which satisfies the
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ASTM 7566 standard and can be used as high quality jet fuel blend.
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Keywords: Wet algae paste, fractional extraction, direct hydroconversion, Pt/Meso-
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ZSM-5 catalyst
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Chao Ju, Feng Wang, Yong Huang, Yunming Fang
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Corresponding author. Tel. & Fax:+86-10-64429057 E-mail address: [email protected] (Yunming Fang)
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1. Introduction The exploration of an alternative jet fuel has been drawing worldwide attention
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because of the double threats of oil shortage and environmental concerns [1]. The levy of
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carbon tax further accelerates the development of renewable jet fuel. As the only
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renewable carbon-containing source in the world, the production of jet fuel from biomass
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becomes one of the most promising routes [2]. Algae are potentially very promising
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biomass feedstock due to their fast growth rate and high per-acre productivity [3].
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The biochemical composition of algae is conventionally classified to lipids,
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carbohydrates, proteins, and nucleic acids [3, 4]. Based on their molecular information,
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lipids such as triglycerides, free fatty acids, phospholipids, and glycolipids have high
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potential to be an alternative fuel. For instance, triglycerides could be converted to jet
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fuel by combination of hydrocracking and isomerization, and the products generated had
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suitable properties and were compatible with current infrastructure [5]. Therefore,
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extensive research works on the extraction of lipids, as one of the most important and
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challenging steps in the production of algal biofuel, have been carried out [6-16]. These
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works can be divided into the following catalogs: 1) application of commercial extraction
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methods such as hexane extraction and mechanical express process used for terrestrial
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oilseed plants; 2) co-solvent system (chloroform/methanol, hexane/ethanol, and so on)
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extraction methods originally used for laboratory scale analyses [6-8]; 3) cell rupture
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(ultrasonic or electromagnetic release) based extraction methods [9]; 4) employing high
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pressure such as accelerated solvent extraction, subcritical water extraction, supercritical
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methanol or carbon dioxide extraction, and so on [10-13]; 5) simultaneous lipid
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extraction and transesterification [14-16]. Unfortunately, those above-mentioned methods
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are either poor in extraction yield or difficult for large scale industrial application.
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Moreover, drying process, one of the most energy-intensive steps, is usually necessary
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before the extraction. Development of high-efficient extraction for lipids without drying
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step is thus essential.
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Most of the studies for algal jet fuel mainly focus on the conversion of extracted lipid
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into jet fuel range acyclic paraffins (C9–C15) [17-19]. The existing process was often
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divided into multi steps, including long-chain paraffins production and hydro-
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isomerization/hydrocracking [20]. The production of long-chain alkane can further be
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divided into hydrodeoxygenation and decarboxylation mechanisms [18]. However, the
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multi-step process requires high investment for system equipment and consumes much
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hydrogen (7-10% hydrogen of algal oil). Recently, Verma et al. proposed a single-step
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process for conversion of algal lipid to jet fuel range paraffins using sulfide Ni-Mo
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catalyst supported on semi-crystalline ZSM-5 with high surface area, and the yield of jet
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range compounds from resultant paraffins was as high as 77% [1]. The single-step
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process not only shortens the reaction pathway but also simplifies the operation. On the
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other hand, the level of contaminants in the extracted lipids such as metals, phosphorous,
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nitrogen, chlorine, and sulfur varies widely depends upon both methods of cultivation and
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lipid extraction. Lipids rich in above contaminants present challenges for catalytic
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processing without additional pretreatments, e.g., degumming processes, which lead to
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additional cost for the whole algae to jet fuel process [21, 22].
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As discussed above, algal biofuel (including algal jet fuel) production chain covers a
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series of unit operations. Up to date, a lot of researches have been working on separate
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operations [23,24]. For example, research on drying step generally focused on the
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efficient energy input and drying reactor development but overlooked the influence of
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drying step on the oil extraction step. Indeed, oil extraction starting form wet algae or
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dried algae can be very different. Similarly, in the oil extraction, the influence of different
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extraction steps on the processing ability of lipid product was not systematically studied.
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Furthermore, the influence of algal feedstocks (such as ash, polar lipid, pigment and so
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on) on jet fuel production was also not carefully studied. In an ideal case, these unit
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operations such as drying, oil extraction, and processing should be considered together.
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The boundary of different unit operations, which was largely overlooked currently,
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should be studied in detail. With such a consideration, the wet algae paste was converted
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into jet fuel through a combination of selective neutral lipid extraction and direct
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hydroconversion processes in the paper.
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2. Experimental
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2.1 Materials
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Scendesmus dimorphus (SD) algae samples with aournd 75 wt% of water content
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harvested from outdoor glass panel system were used in this work. The glass panel
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system was constructed and equipped with CO2 supply pipelines and temperature control
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system. Glass panels were placed in East–West orientation. The maximum culture
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temperature in glass panels outdoors was around 38 °C by an internal thermal exchanger
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connected to an evaporative cooling unit. Culture mixing and CO2 supply in panel system
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were provided by air bubbles enriched with 2% CO2. Algae samples, after removed the
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bulk water by centrifugation, were kept as 3–5 cm algae cake at -80 °C refrigerator until
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use. The lipid content and subclass composition were determined according to reference
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[8] and given in Table 1. Chemicals such as ethanol, hexane with HPLC grade, and
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Chloroplatinic acid hydrate (H2PtCl6.xH2O, ≥99.9 % trace metals basis) were purchased
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from Sigma-Aldrich and used as received without any further treatment. The mesoporous
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ZSM-5 zeolite and Pt/Meso-ZSM-5 catalyst were synthesized according to pervious
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publication [25]. Algal oil extracted from SD algae by chloroform/methanol mixture [8]
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was used as reference.
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2.2 Algal oil extraction
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The extraction was carried out as follows: pre-calculated amount of wet algae
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biomass and ethanol solvent (6 mL/g dry algae) were added into an extraction autoclave
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equipped with condenser, mechanical stirring, and thermocouple. The mixture was
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extracted for 1 h under reflux conditions. After cooled to the room temperature, the
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mixture was subjected to vacuum filtration and crude extract and residue were obtained.
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The pore size of microporous membrane for filtration was 0.22 µm. The crude extract
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was further separated to lipid fraction and non-lipid fraction by liquid-liquid extraction,
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in which water and hexane were added to achieve a volume ratio of ethanol: hexane:
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water at 1: 1: 1. The residue was subjected into a next sequential extraction. Two
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sequential ethanol extraction cycles were used in this study, after which hexane
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extraction cycle was employed. Two hexane extraction cycles were performed in Lab
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scale experiment, while only one cycle was carried out for the neutral-lipid-rich algae.
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The total lipids of algae samples were analyzed in a chloroform–methanol–water
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system according to Bligh and Dyer’s method and used as reference for the lipid recovery
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calculation [5]. The pigment content was determined according to Wellburn’s method
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[26]. Total lipids were further separated into neutral lipids and polar lipids by column
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chromatography using silica gel (60–200 mesh) (Merck Corp., Germany) as previously
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described [19]: six volumes of chloroform to collect the neutral lipid class and six
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volumes of methanol to collect the polar lipids. Each lipid fraction was transferred into a
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pre-weighed vial, evaporated at 30 °C using a rotary evaporator (Büchi, Switzerland), and
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then dried under high vacuum. The dried residue was placed under nitrogen and then
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weighed. Fatty acid profile of lipids were quantified by GC/MS after derivatization into
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fatty acid methyl esters using heptadecanoic acid (C17:0) as the internal standard [19].
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The metal content of the extracted lipid sample was analyzed by ICP analysis. The
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samples (solid algae or algal oil) were combusted in air at 800 °C to get the ash. The
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obtained ash was dissolved in HNO3 solution for metal content test through ICP analysis.
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The weight in all the steps was recorded carefully for the calculation of metal content.
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The catalyst used for hydro-conversion was analyzed by high resolution TEM with a
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JEOL 3010F microscope. The catalyst was dispersed in ethanol, and deposited on a holey
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film supported on a lacey support films.
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2.3 Hydroconversion of neutral fraction of algal lipid into jet fuel
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Hydroconversion was carried out in a fixed bed trickle reactor. The Pt-Meso-ZSM-5
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catalyst (20-40 mesh, 2.5 mL) which the Pt content was 0.6 wt.% (determined by ICP
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analysis), diluted with SiC (5 mL) to ensure sufficient catalyst-bed length and to improve
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the reaction-heat transfer, was loaded into a stainless steel tubular reactor (1.5 cm in inner
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diameter and 30 cm in length) [27]. Hydrogen pressure was controlled by a back pressure
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regulator, gas flow was controlled by a mass flow controller, and catalyst bed
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temperatures were monitored by thermocouples. A high pressure liquid metering pump
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was used to maintain desired liquid flow. The gas-liquid mixture passed through the
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pressure gas-liquid separator to separate gaseous fraction from liquid product. Gaseous
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product was released to atmosphere by a gas-meter and analyzed using an Agilent GC
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7890A, while liquid product was drained to the atmospheric separator in order to remove
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trace amounts of gases. The reaction condition for all the catalytic hydrotreating
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experiments was as follows: temperature, 375°C; pressure, 30 bar; LHSV, 1 h-1; and H2
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to feed ratio (V/V), 1500 [28]. The liquid products were sampled after stabilization of
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reaction conditions (12 h) in two-hour intervals and analyzed by off-line GC/MS analysis
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after separation of the water phase. The reaction gases were analyzed using an Agilent
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7890A equipped with a flame ionization detector (FID) and two thermal conductivity
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detectors (TCD). The quality of obtained bio-jet fuel such as energy density, flash and
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freeze points was analyzed by ASTM methods included in ASTM 7566.
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In order to confirm the reliable of experiment results. The oil extraction and
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conversion experiments were carried out at least for twice. The results shown in Table
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and Figures indicate the reliability of our experiment results since the standard errors in
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most cases are less than 5%. And the catalytic performance of oil obtained in two
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different batches used the same method were almost the same.
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3 Results and discussion
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3.1 Fractional extraction from wet algae biomass
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ethanol and hexane as solvents in different extraction steps was firstly designed and
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inverstigated. The extraction performance of proposed ethanol/hexane extraction process
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of algae is shown in Figure 1. It was found that the oil recovery was as high as 90 wt% of
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lipid after three extraction cycles, which suggested the excellent extraction performance
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of the proposed system [29]. As also shown in Figure 1, the lipid composition is changed
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with the extraction cycles. The results of column chromatography revealed that the
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neutral lipid percentages in the crude extract were 12%, 57%, 93%, and 94% from the
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first to fourth steps, respectively. The appearance of extract from each cycle was also
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quite different. The extract from the first cycle was a dark black semi-solid after the
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solvent was removed, while it was yellow liquid with good flow quality from the third
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cycle (Figure S1 in supporting information). The difference in color of each extract was
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further examined by a pigment content analysis. The ratios of carotenoid to chlorophyll
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were 0.05, 0.27, 0.31, and 0.34 from the first to fourth cycles. The change in flow
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property of each extract was explained by the different lipid composition. The very high
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polar lipid content was the main reason for its semi-solid appearance since polar lipid is
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generally considered as “gum” in the oil industry [30]. The fatty acid profile of each
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crude extract was detected by GC/MS after it converted to fatty acid methyl ester. Similar
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fatty acid composition was found to all extracts with 16:0, 16:1, 16:2, 18:0, 18:1, 18:2,
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18:3, and 20:5 as the main components. The detail fatty acid profile of algal oil extracted
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through this fractional extraction and reference method was shown in Table 2.
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Based on the results described above, it was concluded that polar and neutral lipid
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fractions were separated during the extraction process, which were explained by the
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change in the polarity of the solvent used in each extraction cycle. The solubility of polar
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and neutral lipid in aqueous ethanol altered with different ethanol concentration [22]. It
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needed to be noted that the sorption capacity of algae to solvent was quite high. In this
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experiment, it was found that the algae cake retained solvent as much as 2 mL/g. In the
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first extraction cycle, the strong polar solvent (~70% of aqueous ethanol solution)
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selectively extracted polar lipid from algae. From the third extraction cycle, the neutral
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lipid was miscible in the solvents mixture (ethanol and hexane) while the solubility of
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polar lipid was limited. Thus neutral lipid was selectively extracted in the third and fourth
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extraction cycles. Unlike the first and third extraction cycle, the second cycle obtained a
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comparable polar lipid and neutral lipid content since the ethanol concentration is 92% in
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this step which neither selectively extracted polar lipid nor neutral lipid. The second cycle
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was thus considered to be a transition step with moderate neutral lipid (55%) in the crude
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extract. That was also the reason why at least three extraction cycles were necessary in
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the current extraction system. Since the solvent properties have large influence on the
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extraction performance, it can be expected that the water content in algae paste have large
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influence on the extraction performance. When compared with the objective outlined in
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the DOE algal biofuel roadmap, our process met most of those criteria, such as efficient
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extraction of algal oil from a water rich algae biomass, recovery of more than 85% lipid
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as so on. With respect to the energy consumption criteria (15% of the final product
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according to DOE), larger scale extraction experiments as well as process simulation
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should be implemented before a scientific conclusion can be drawn [29].
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3.2 Catalytic hydroconversion of neutral fraction of algal lipid into jet fuel range
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paraffin
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Algal oil usually contains strong polar lipid and pigment, and the metal content is
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also high [31]. It was reported in bio-oil hydrogenation, the high metal content is the
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main hindrance to the catalytic performance. The deposition of metal over catalyst
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surface can poison the catalytic active sites, so that it has negative influence on the
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catalytic performance. Removing the metal through ion-exchange and filtration can
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dramatically improve the catalyst lifetime. Hence the metal contents in common algal
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lipid extracted by chloroform/methanol and in neutral lipid (lipid extracted with hexane)
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extracted by our process were firstly studied. From Figure 2, it can be found the metal
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content in common algal lipids extracted by mixture solvent are relatively high. The Ca,
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Mg, and Cu contents are 1400, 820, and 200 mg/kg, while the Ca, Mg, and Cu contents in
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neutral lipid are 2, 0, and 3 mg/kg, respectively.The reduced metal content can be
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attributed to the formation mechanism of polar lipid and pigment since the metals are
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always existed in polar lipid or pigments. The fractional extraction of neutral lipid
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renders its lower metal content. The reduced metal content could have a positive point in
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lipid hydroconversion.
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Verma et al. reported a mesoporous ZSM-5 supported Ni-Mo catalyst for one-step
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conversion of lipid into jet fuel range paraffin and iso-paraffin [1]. Here in this paper, a
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similar mesoporous ZSM-5 was synthesized and used as catalyst support. The
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characterization results were shown in Figure 3. The X-ray diffraction (XRD) pattern of
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the mesoporous ZSM-5 shows a typical XRD pattern that belongs to MFI structure.
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Nitrogen sorption studies show a type IV isotherm, which is typical for mesoporous
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materials with both characteristics belonging to microporous materials and mesoporous
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materials. HRTEM analysis proved the high crystalline of MFI zeolite nature since the
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crystal lattice is clear visible. No diffractions belonging to Pt metal was found in the 1%
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Pt/Meso-ZSM-5 bifunctional catalyst. The nitrogen adsorption isotherms are very similar
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to that of parent mesoporous ZSM-5. The results shown in Table 3 indicate the textural
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properties are little affacted after Pt deposition. The HRTEM images also proved the high
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dispersion of Pt nanoparticles over the mesoporous ZSM-5 support. The size of Pt
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particles is around 2~3 nm according to the TEM analysis.
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The catalytic conditions for neutral lipid conversion were firstly optimized with
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soybean oil as model compound. The optimized conditions (375 °C, 3 MPa, H2/oil=700)
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were then used in the experiment with algal oil (hexane fraction) extracted in two
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different batches. Figure 4 shows the comparison of the algal oil samples conversion over
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the Pt/meso-ZSM-5. In the initial period, the catalyst was able to convert the lipid oil into
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hydrocarbon with very high conversion at 375 °C. However, with the common lipid oil as
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feedstock, the catalyst was deactivated within 10 h. Elemental analysis of the deactivated
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catalyst indicated the deposition of Ca and Mg on the catalyst surface. The catalyst with
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the extracted neutral lipid rich algal oil as feedstock can be operated stably for more than
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100 h.
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The jet fuel yield from neutral lipid is 38 wt.%, which is a typical value due to the
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loss of oxygen and hydrocracking nature. The overall algae to jet fuel yield is about 7%.
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It should be noted our report here focuses on the process ability of extracted algal oil rich
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in neutral lipid. The overall performance of this process could be further improved if
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more desired algae feedstocks and catalytic materials was developed and used. Figure 5
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gives the hydrocarbon distribution of the jet fuel product from algal oil. It can be found
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the carbon chain of isomers distributes uniformly between C9 and C15, and the jet fuel
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sample is rich in iso-paraffin. The iso-paraffin is ideal as jet fuel due to its low freezing
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point. The jet fuel product from neutral lipid meets most of the standard of ASTM 7566
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as alternative aviation fuel including the desired freezing point (-57 °C), density (0.74
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g/mL), flash point (42 °C), heat of combustion (45 MJ/kg), and aromatics content (<1%).
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The density (0.735 g/mL) is slightly lower than the required value in ASTM 7566
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specification [32]. However, the low density is a general limitation of iso-paraffin as jet
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fuel, and this can be improved to meet the specification requirement by addition of
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aromatics and cycloalkane.
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4. Conclusion
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The following conclusions can be derived from the present study:
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1)
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fractional separation of polar and neutral lipids. This fractional extraction system meets
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most of the criteria recommended in DOE roadmap.
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2)
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metal content than the oil extracted from typical mixture solvent system, and results in
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stable conversion (100 h) over Pt/Meso-ZSM-5.
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3)
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57 °C, 42 °C, and 45 MJ/kg, respectively, which satisfies the ASTM 7566 standard and
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can be used as high quality jet fuel blend.
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The freeze point, flash point, and energy density of the obtained jet fuel are -
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Sequential extraction of wet algae paste with ethanol and hexane result in the
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hydrocarbons using heterogeneous catalysts: A review, J. Ind. Eng. Chem. 29 (2015) 12-
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23.
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[21] F. Marrakchi, K. Kriaa, B. Hadrich, N. Kechaou, Experimental investigation of
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processing parameters and effects of degumming, neutralization and bleaching on
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lampante virgin olive oil's quality, Food Bioprod Process 94 (2015) 124-135.
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[22] F.Y. Jiang, J.M. Wang, I. Kaleem, D.Z. Dai, X.H. Zhou, C. Li, Degumming of
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vegetable oils by a novel phospholipase B from Pseudomonas fluorescens BIT-18,
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Bioresource Technol. 102 (2011) 8052-8056.
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[23] J.J. Milledge, S. Heaven, A review of the harvesting of micro-alage for biofuel
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production, Rev. Environ. Sci. Bio. 12 (2013) 165-178.
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[24] J. Ruiz, G Olivieri, J. de Vree, R. Bosma, P. Willems, J.H. Reith, M.M. Eppink,
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D.M.M. Kleinegris, R.H. Wijffels, M.J. Barbosa, Towards industrial products from
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microalgae 9 (2016) 3036-3043.
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[25] M. Li, I.N. Oduro, Y. Zhou, Y. Huang, Y. Fang, Amphiphilic organosilane and seed
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assisted hierarchical ZSM-5 synthesis: Crystallization process and structure, Micropor.
335
Mesopor. Mat. 221 (2016) 108-116.
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[26] A.R. Wellburn, The spectral determination of chlorophylls a and b, as well as total
337
carotenoids, using various solvents with spectrophotometers of different resolution, J.
338
Plant Physiol 144 (1994) 307-313.
339
[27] Y. Wang, T. He, K. Liu, J. Wu, Y. Fang, From biomass to advanced bio-fuel by
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catalytic pyrolysis/hydro-processing: Hydrodeoxygenation of Bio-oil derived from
341
biomass catalytic pyrolysis, Bioresource Technol. 108 (2012) 280-284.
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[28] C. Ju, Y. Zhou, M. He, Q. Wu, Y. Fang, Improvement of selectivity from lipid to jet
343
fuel by rational integration of feedstock properties and catalytic strategy, Renew. Energy
344
97 (2016) 1-7.
345
[29] J. Ferrell, V. Sarisky-Reed, National Algal Biofuels Technology Roadmap. United
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States: N. p., 2010. Web. doi:10.2172/121856.
347
[30] A.J. Dijkstra, O.M. Van, The total degumming process. J. Am. Oil Chem. Soc. 66
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(1989) 1002-1009.
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[31] C. Wang, J.S. Buchanan, W.R. Kliewer, K. Qian, Water-washing to reduce metals in
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oils extracted from Nannochloropsis algae for potential FCC feedstock, Fuel 155 (2015)
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63-67.
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[32] Standard Specification for Aviation Turbine Fuel Containing Synthesized
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Hydrocarbons, http://www.astm.org/Standards/D7566.htm.
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Table 1. The lipid class percentage in different algal oil samples*1 Oil samples
Neutral lipid/%
Polar lipid/%
Free fatty acid/%
Algae2
67±0.2
27±0.2
6±0
65±0.3
28±0.1
8±0.2
97±0.1
2±0.03
Oil extracted by common method Oil extracted by fractional method
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1±0.05
*1 Results were expressed in mean ± standard error from duplicate analyses.
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*2 25% total lipid content
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Table 2. Fatty acid profile of algal oil (total lipid) extracted through this fractional extraction and reference method Extraction method
16:0
16:1
18:0
18:1
18:2
18:3
20:0
20:1
Others
Reference/%
36.2
2.87
3.3
24.5
19.2
11.1
0.71
1.11
1.01
Fractional/%
35.8
3.1
3.2
23.7
18.7
12.3
361
0.57
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1.31
1.32
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Table 3. Textural and chemical properties of Meso-ZSM-5 and Pt/Meso-ZSM-5 SBET
V meso
Vmicro
V total
(mL/g)
(mL/g)
(mL/g)
4.73
0.47
0.08
0.55
4.52
0.47
0.07
0.54
2
Dpore (nm)
Meso-ZSM-5
483
Pt/Meso-ZSM-5
479
Zeolite
(m /g)
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Neutral lipid Neutral lipid
Polar lipid Polar lipid
100
80
16
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14
Lipid recovery (% of Lipid)
18
12
60
10 8
40
6 4
20
2 0
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Lipid recovery (% of DW)
20
Total lipid Total lipid
0
1
2
3
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Figure 1. Algal oil extraction performance with ethanol/hexane solvent system. The total,
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polar and neutral lipid recovery to lipid are calculated with the overall total lipid, polar
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lipid and neutral lipid as 100%, respectively. Results were expressed in mean ± standard
369
error from duplicate extraction. The left y-axis corresponds to the bar graph, and the right
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y-axis corresponds to the line graph.
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1600
Oil extracted by common method Oil extracted by fractional method
6 4
800
2 0
Ca
Mg
Cu
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8
0 Ca
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Metal content (ppm)
1200
Mg
Cu
Metals
Figure 2. Difference of metal content of algal oil in reference sample and oil extracted by
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the developed fractional approach. Results were expressed in mean ± standard error from
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duplicate extraction.
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Meso-ZSM-5
500
400
Pt/Meso-ZSM-5 300
200
Meso-ZSM-5
100
0 10
20
30
40
50
0.0
0.2
0.4
0.6
0.8
1.0
Relative Pressure (P/P0)
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Pt/Meso-ZSM-5
Volume Adsorbed (cm3/g, STP)
Intensity (a.u.)
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Figure 3. XRD patterns (a) and nitrogen adsorption isotherms (b) of Meso-ZSM-5 and
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Pt/Meso-ZSM-5 (The y axis offset of Pt/Meso-ZSM-5 in (b) is 150 cm3/g, respectively);
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HRTEM images of the synthetic Meso-ZSM-5 (c) and Pt/Meso-ZSM-5 (d)
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Oil extracted by fractional method
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90
80
70
1st run 2nd run 3rd run
Oil extracted by common method
60 0
20
40
60
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Conversion (%)
100
80
100
379
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Time on Stream (h)
Figure 4. Catalytic performance of the algal oil samples over the Pt/Meso-ZSM-5
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catalyst. Catalytic conversion was repeatedly investigated using neutral lipid rich algal oil
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extracted from two different batches.
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Relative content (%)
16
12 10 8 6
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iC 9 nC 9 iC 10 nC 10 iC 11 nC 11 iC 12 nC 12 iC 13 nC 13 iC 14 nC 14 iC 15 nC 15 iC 16 nC 16
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Carbon number
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Figure 5. Carbon chain length of jet fuel products from neutral lipid rich algal oil
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Highlights Algal oil was extracted directly from wet algae with high efficiency (>90%) Fractional extraction achieved with renewable ethanol and hexane as solvent
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Neutral lipid rich oil has very low metal content
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Neutral lipid rich oil was directly converted into jet fuel over Pt/Meso-ZSM-5
S0960-1481(17)31130-8
DOI:
10.1016/j.renene.2017.11.028
Reference:
RENE 9430
To appear in:
Renewable Energy
Received Date: 7 November 2016 Revised Date:
25 July 2017
Accepted Date: 11 November 2017
Please cite this article as: Ju C, Wang F, Huang Y, Fang Y, Selective extraction of neutral lipid from wet algae paste and subsequently hydroconversion into renewable jet fuel, Renewable Energy (2017), doi: 10.1016/j.renene.2017.11.028. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
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Ethanol Neutral lipids
Water
Hexane
Ethanol
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Pt/meso-ZSM-5
Neutral Jet fuel lipid Hydro-cracking
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Selective extraction of neutral lipid from wet algae paste and
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subsequently hydroconversion into renewable jet fuel ∗
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National Energy Research Center for Biorefinery, Beijing University of Chemical Technology, 100029, Beijing, China
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Abstract: Wet algae paste, after harvested, was converted into renewable jet fuel through
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selective extraction and subsequent hydroconversion without further purification. A
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fractional extraction method based on ethanol and hexane starting from wet algae was
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firstly designed and investigated. The oil recovery was as high as 90 wt.% of lipid after
10
three extraction cycles. Such a method results in fractional extraction of polar lipid and
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neutral lipid separately from wet algal biomass. The obtained neutral lipid rich fraction
12
has very low metal content, in which the Ca, Mg, and Cu contents are 2, 0, and 3 mg/kg,
13
respectively. It can be converted into jet fuel range paraffin by one-step hydrocracking
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over Pt/Meso-ZSM-5 catalyst directly. The freeze point, flash point, and energy density
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of the obtained jet fuel are -57 °C, 42 °C, and 45 MJ/kg, respectively, which satisfies the
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ASTM 7566 standard and can be used as high quality jet fuel blend.
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Keywords: Wet algae paste, fractional extraction, direct hydroconversion, Pt/Meso-
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ZSM-5 catalyst
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Chao Ju, Feng Wang, Yong Huang, Yunming Fang
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Corresponding author. Tel. & Fax:+86-10-64429057 E-mail address: [email protected] (Yunming Fang)
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1. Introduction The exploration of an alternative jet fuel has been drawing worldwide attention
25
because of the double threats of oil shortage and environmental concerns [1]. The levy of
26
carbon tax further accelerates the development of renewable jet fuel. As the only
27
renewable carbon-containing source in the world, the production of jet fuel from biomass
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becomes one of the most promising routes [2]. Algae are potentially very promising
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biomass feedstock due to their fast growth rate and high per-acre productivity [3].
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The biochemical composition of algae is conventionally classified to lipids,
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carbohydrates, proteins, and nucleic acids [3, 4]. Based on their molecular information,
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lipids such as triglycerides, free fatty acids, phospholipids, and glycolipids have high
33
potential to be an alternative fuel. For instance, triglycerides could be converted to jet
34
fuel by combination of hydrocracking and isomerization, and the products generated had
35
suitable properties and were compatible with current infrastructure [5]. Therefore,
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extensive research works on the extraction of lipids, as one of the most important and
37
challenging steps in the production of algal biofuel, have been carried out [6-16]. These
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works can be divided into the following catalogs: 1) application of commercial extraction
39
methods such as hexane extraction and mechanical express process used for terrestrial
40
oilseed plants; 2) co-solvent system (chloroform/methanol, hexane/ethanol, and so on)
41
extraction methods originally used for laboratory scale analyses [6-8]; 3) cell rupture
42
(ultrasonic or electromagnetic release) based extraction methods [9]; 4) employing high
43
pressure such as accelerated solvent extraction, subcritical water extraction, supercritical
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methanol or carbon dioxide extraction, and so on [10-13]; 5) simultaneous lipid
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extraction and transesterification [14-16]. Unfortunately, those above-mentioned methods
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are either poor in extraction yield or difficult for large scale industrial application.
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Moreover, drying process, one of the most energy-intensive steps, is usually necessary
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before the extraction. Development of high-efficient extraction for lipids without drying
49
step is thus essential.
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Most of the studies for algal jet fuel mainly focus on the conversion of extracted lipid
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into jet fuel range acyclic paraffins (C9–C15) [17-19]. The existing process was often
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divided into multi steps, including long-chain paraffins production and hydro-
53
isomerization/hydrocracking [20]. The production of long-chain alkane can further be
54
divided into hydrodeoxygenation and decarboxylation mechanisms [18]. However, the
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multi-step process requires high investment for system equipment and consumes much
56
hydrogen (7-10% hydrogen of algal oil). Recently, Verma et al. proposed a single-step
57
process for conversion of algal lipid to jet fuel range paraffins using sulfide Ni-Mo
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catalyst supported on semi-crystalline ZSM-5 with high surface area, and the yield of jet
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range compounds from resultant paraffins was as high as 77% [1]. The single-step
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process not only shortens the reaction pathway but also simplifies the operation. On the
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other hand, the level of contaminants in the extracted lipids such as metals, phosphorous,
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nitrogen, chlorine, and sulfur varies widely depends upon both methods of cultivation and
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lipid extraction. Lipids rich in above contaminants present challenges for catalytic
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processing without additional pretreatments, e.g., degumming processes, which lead to
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additional cost for the whole algae to jet fuel process [21, 22].
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As discussed above, algal biofuel (including algal jet fuel) production chain covers a
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series of unit operations. Up to date, a lot of researches have been working on separate
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operations [23,24]. For example, research on drying step generally focused on the
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efficient energy input and drying reactor development but overlooked the influence of
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drying step on the oil extraction step. Indeed, oil extraction starting form wet algae or
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dried algae can be very different. Similarly, in the oil extraction, the influence of different
72
extraction steps on the processing ability of lipid product was not systematically studied.
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Furthermore, the influence of algal feedstocks (such as ash, polar lipid, pigment and so
74
on) on jet fuel production was also not carefully studied. In an ideal case, these unit
75
operations such as drying, oil extraction, and processing should be considered together.
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The boundary of different unit operations, which was largely overlooked currently,
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should be studied in detail. With such a consideration, the wet algae paste was converted
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into jet fuel through a combination of selective neutral lipid extraction and direct
79
hydroconversion processes in the paper.
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2. Experimental
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2.1 Materials
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Scendesmus dimorphus (SD) algae samples with aournd 75 wt% of water content
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harvested from outdoor glass panel system were used in this work. The glass panel
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system was constructed and equipped with CO2 supply pipelines and temperature control
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system. Glass panels were placed in East–West orientation. The maximum culture
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temperature in glass panels outdoors was around 38 °C by an internal thermal exchanger
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connected to an evaporative cooling unit. Culture mixing and CO2 supply in panel system
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were provided by air bubbles enriched with 2% CO2. Algae samples, after removed the
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bulk water by centrifugation, were kept as 3–5 cm algae cake at -80 °C refrigerator until
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use. The lipid content and subclass composition were determined according to reference
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[8] and given in Table 1. Chemicals such as ethanol, hexane with HPLC grade, and
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Chloroplatinic acid hydrate (H2PtCl6.xH2O, ≥99.9 % trace metals basis) were purchased
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from Sigma-Aldrich and used as received without any further treatment. The mesoporous
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ZSM-5 zeolite and Pt/Meso-ZSM-5 catalyst were synthesized according to pervious
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publication [25]. Algal oil extracted from SD algae by chloroform/methanol mixture [8]
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was used as reference.
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2.2 Algal oil extraction
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The extraction was carried out as follows: pre-calculated amount of wet algae
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biomass and ethanol solvent (6 mL/g dry algae) were added into an extraction autoclave
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equipped with condenser, mechanical stirring, and thermocouple. The mixture was
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extracted for 1 h under reflux conditions. After cooled to the room temperature, the
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mixture was subjected to vacuum filtration and crude extract and residue were obtained.
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The pore size of microporous membrane for filtration was 0.22 µm. The crude extract
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was further separated to lipid fraction and non-lipid fraction by liquid-liquid extraction,
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in which water and hexane were added to achieve a volume ratio of ethanol: hexane:
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water at 1: 1: 1. The residue was subjected into a next sequential extraction. Two
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sequential ethanol extraction cycles were used in this study, after which hexane
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extraction cycle was employed. Two hexane extraction cycles were performed in Lab
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scale experiment, while only one cycle was carried out for the neutral-lipid-rich algae.
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The total lipids of algae samples were analyzed in a chloroform–methanol–water
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system according to Bligh and Dyer’s method and used as reference for the lipid recovery
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calculation [5]. The pigment content was determined according to Wellburn’s method
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[26]. Total lipids were further separated into neutral lipids and polar lipids by column
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chromatography using silica gel (60–200 mesh) (Merck Corp., Germany) as previously
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described [19]: six volumes of chloroform to collect the neutral lipid class and six
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volumes of methanol to collect the polar lipids. Each lipid fraction was transferred into a
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pre-weighed vial, evaporated at 30 °C using a rotary evaporator (Büchi, Switzerland), and
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then dried under high vacuum. The dried residue was placed under nitrogen and then
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weighed. Fatty acid profile of lipids were quantified by GC/MS after derivatization into
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fatty acid methyl esters using heptadecanoic acid (C17:0) as the internal standard [19].
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The metal content of the extracted lipid sample was analyzed by ICP analysis. The
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samples (solid algae or algal oil) were combusted in air at 800 °C to get the ash. The
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obtained ash was dissolved in HNO3 solution for metal content test through ICP analysis.
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The weight in all the steps was recorded carefully for the calculation of metal content.
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The catalyst used for hydro-conversion was analyzed by high resolution TEM with a
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JEOL 3010F microscope. The catalyst was dispersed in ethanol, and deposited on a holey
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film supported on a lacey support films.
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2.3 Hydroconversion of neutral fraction of algal lipid into jet fuel
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Hydroconversion was carried out in a fixed bed trickle reactor. The Pt-Meso-ZSM-5
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catalyst (20-40 mesh, 2.5 mL) which the Pt content was 0.6 wt.% (determined by ICP
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analysis), diluted with SiC (5 mL) to ensure sufficient catalyst-bed length and to improve
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the reaction-heat transfer, was loaded into a stainless steel tubular reactor (1.5 cm in inner
133
diameter and 30 cm in length) [27]. Hydrogen pressure was controlled by a back pressure
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regulator, gas flow was controlled by a mass flow controller, and catalyst bed
135
temperatures were monitored by thermocouples. A high pressure liquid metering pump
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was used to maintain desired liquid flow. The gas-liquid mixture passed through the
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pressure gas-liquid separator to separate gaseous fraction from liquid product. Gaseous
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product was released to atmosphere by a gas-meter and analyzed using an Agilent GC
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7890A, while liquid product was drained to the atmospheric separator in order to remove
140
trace amounts of gases. The reaction condition for all the catalytic hydrotreating
141
experiments was as follows: temperature, 375°C; pressure, 30 bar; LHSV, 1 h-1; and H2
142
to feed ratio (V/V), 1500 [28]. The liquid products were sampled after stabilization of
143
reaction conditions (12 h) in two-hour intervals and analyzed by off-line GC/MS analysis
144
after separation of the water phase. The reaction gases were analyzed using an Agilent
145
7890A equipped with a flame ionization detector (FID) and two thermal conductivity
146
detectors (TCD). The quality of obtained bio-jet fuel such as energy density, flash and
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freeze points was analyzed by ASTM methods included in ASTM 7566.
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In order to confirm the reliable of experiment results. The oil extraction and
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conversion experiments were carried out at least for twice. The results shown in Table
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and Figures indicate the reliability of our experiment results since the standard errors in
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most cases are less than 5%. And the catalytic performance of oil obtained in two
152
different batches used the same method were almost the same.
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3 Results and discussion
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3.1 Fractional extraction from wet algae biomass
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ethanol and hexane as solvents in different extraction steps was firstly designed and
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inverstigated. The extraction performance of proposed ethanol/hexane extraction process
158
of algae is shown in Figure 1. It was found that the oil recovery was as high as 90 wt% of
159
lipid after three extraction cycles, which suggested the excellent extraction performance
160
of the proposed system [29]. As also shown in Figure 1, the lipid composition is changed
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with the extraction cycles. The results of column chromatography revealed that the
162
neutral lipid percentages in the crude extract were 12%, 57%, 93%, and 94% from the
163
first to fourth steps, respectively. The appearance of extract from each cycle was also
164
quite different. The extract from the first cycle was a dark black semi-solid after the
165
solvent was removed, while it was yellow liquid with good flow quality from the third
166
cycle (Figure S1 in supporting information). The difference in color of each extract was
167
further examined by a pigment content analysis. The ratios of carotenoid to chlorophyll
168
were 0.05, 0.27, 0.31, and 0.34 from the first to fourth cycles. The change in flow
169
property of each extract was explained by the different lipid composition. The very high
170
polar lipid content was the main reason for its semi-solid appearance since polar lipid is
171
generally considered as “gum” in the oil industry [30]. The fatty acid profile of each
172
crude extract was detected by GC/MS after it converted to fatty acid methyl ester. Similar
173
fatty acid composition was found to all extracts with 16:0, 16:1, 16:2, 18:0, 18:1, 18:2,
174
18:3, and 20:5 as the main components. The detail fatty acid profile of algal oil extracted
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through this fractional extraction and reference method was shown in Table 2.
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Based on the results described above, it was concluded that polar and neutral lipid
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fractions were separated during the extraction process, which were explained by the
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change in the polarity of the solvent used in each extraction cycle. The solubility of polar
179
and neutral lipid in aqueous ethanol altered with different ethanol concentration [22]. It
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needed to be noted that the sorption capacity of algae to solvent was quite high. In this
181
experiment, it was found that the algae cake retained solvent as much as 2 mL/g. In the
182
first extraction cycle, the strong polar solvent (~70% of aqueous ethanol solution)
183
selectively extracted polar lipid from algae. From the third extraction cycle, the neutral
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lipid was miscible in the solvents mixture (ethanol and hexane) while the solubility of
185
polar lipid was limited. Thus neutral lipid was selectively extracted in the third and fourth
186
extraction cycles. Unlike the first and third extraction cycle, the second cycle obtained a
187
comparable polar lipid and neutral lipid content since the ethanol concentration is 92% in
188
this step which neither selectively extracted polar lipid nor neutral lipid. The second cycle
189
was thus considered to be a transition step with moderate neutral lipid (55%) in the crude
190
extract. That was also the reason why at least three extraction cycles were necessary in
191
the current extraction system. Since the solvent properties have large influence on the
192
extraction performance, it can be expected that the water content in algae paste have large
193
influence on the extraction performance. When compared with the objective outlined in
194
the DOE algal biofuel roadmap, our process met most of those criteria, such as efficient
195
extraction of algal oil from a water rich algae biomass, recovery of more than 85% lipid
196
as so on. With respect to the energy consumption criteria (15% of the final product
197
according to DOE), larger scale extraction experiments as well as process simulation
198
should be implemented before a scientific conclusion can be drawn [29].
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3.2 Catalytic hydroconversion of neutral fraction of algal lipid into jet fuel range
200
paraffin
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also high [31]. It was reported in bio-oil hydrogenation, the high metal content is the
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main hindrance to the catalytic performance. The deposition of metal over catalyst
204
surface can poison the catalytic active sites, so that it has negative influence on the
205
catalytic performance. Removing the metal through ion-exchange and filtration can
206
dramatically improve the catalyst lifetime. Hence the metal contents in common algal
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lipid extracted by chloroform/methanol and in neutral lipid (lipid extracted with hexane)
208
extracted by our process were firstly studied. From Figure 2, it can be found the metal
209
content in common algal lipids extracted by mixture solvent are relatively high. The Ca,
210
Mg, and Cu contents are 1400, 820, and 200 mg/kg, while the Ca, Mg, and Cu contents in
211
neutral lipid are 2, 0, and 3 mg/kg, respectively.The reduced metal content can be
212
attributed to the formation mechanism of polar lipid and pigment since the metals are
213
always existed in polar lipid or pigments. The fractional extraction of neutral lipid
214
renders its lower metal content. The reduced metal content could have a positive point in
215
lipid hydroconversion.
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Verma et al. reported a mesoporous ZSM-5 supported Ni-Mo catalyst for one-step
217
conversion of lipid into jet fuel range paraffin and iso-paraffin [1]. Here in this paper, a
218
similar mesoporous ZSM-5 was synthesized and used as catalyst support. The
219
characterization results were shown in Figure 3. The X-ray diffraction (XRD) pattern of
220
the mesoporous ZSM-5 shows a typical XRD pattern that belongs to MFI structure.
221
Nitrogen sorption studies show a type IV isotherm, which is typical for mesoporous
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materials with both characteristics belonging to microporous materials and mesoporous
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materials. HRTEM analysis proved the high crystalline of MFI zeolite nature since the
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crystal lattice is clear visible. No diffractions belonging to Pt metal was found in the 1%
225
Pt/Meso-ZSM-5 bifunctional catalyst. The nitrogen adsorption isotherms are very similar
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to that of parent mesoporous ZSM-5. The results shown in Table 3 indicate the textural
227
properties are little affacted after Pt deposition. The HRTEM images also proved the high
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dispersion of Pt nanoparticles over the mesoporous ZSM-5 support. The size of Pt
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particles is around 2~3 nm according to the TEM analysis.
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The catalytic conditions for neutral lipid conversion were firstly optimized with
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soybean oil as model compound. The optimized conditions (375 °C, 3 MPa, H2/oil=700)
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were then used in the experiment with algal oil (hexane fraction) extracted in two
233
different batches. Figure 4 shows the comparison of the algal oil samples conversion over
234
the Pt/meso-ZSM-5. In the initial period, the catalyst was able to convert the lipid oil into
235
hydrocarbon with very high conversion at 375 °C. However, with the common lipid oil as
236
feedstock, the catalyst was deactivated within 10 h. Elemental analysis of the deactivated
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catalyst indicated the deposition of Ca and Mg on the catalyst surface. The catalyst with
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the extracted neutral lipid rich algal oil as feedstock can be operated stably for more than
239
100 h.
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The jet fuel yield from neutral lipid is 38 wt.%, which is a typical value due to the
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loss of oxygen and hydrocracking nature. The overall algae to jet fuel yield is about 7%.
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It should be noted our report here focuses on the process ability of extracted algal oil rich
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in neutral lipid. The overall performance of this process could be further improved if
244
more desired algae feedstocks and catalytic materials was developed and used. Figure 5
245
gives the hydrocarbon distribution of the jet fuel product from algal oil. It can be found
246
the carbon chain of isomers distributes uniformly between C9 and C15, and the jet fuel
247
sample is rich in iso-paraffin. The iso-paraffin is ideal as jet fuel due to its low freezing
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point. The jet fuel product from neutral lipid meets most of the standard of ASTM 7566
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as alternative aviation fuel including the desired freezing point (-57 °C), density (0.74
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g/mL), flash point (42 °C), heat of combustion (45 MJ/kg), and aromatics content (<1%).
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The density (0.735 g/mL) is slightly lower than the required value in ASTM 7566
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specification [32]. However, the low density is a general limitation of iso-paraffin as jet
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fuel, and this can be improved to meet the specification requirement by addition of
254
aromatics and cycloalkane.
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4. Conclusion
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The following conclusions can be derived from the present study:
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1)
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fractional separation of polar and neutral lipids. This fractional extraction system meets
259
most of the criteria recommended in DOE roadmap.
260
2)
261
metal content than the oil extracted from typical mixture solvent system, and results in
262
stable conversion (100 h) over Pt/Meso-ZSM-5.
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3)
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57 °C, 42 °C, and 45 MJ/kg, respectively, which satisfies the ASTM 7566 standard and
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can be used as high quality jet fuel blend.
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The freeze point, flash point, and energy density of the obtained jet fuel are -
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Sequential extraction of wet algae paste with ethanol and hexane result in the
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Table 1. The lipid class percentage in different algal oil samples*1 Oil samples
Neutral lipid/%
Polar lipid/%
Free fatty acid/%
Algae2
67±0.2
27±0.2
6±0
65±0.3
28±0.1
8±0.2
97±0.1
2±0.03
Oil extracted by common method Oil extracted by fractional method
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1±0.05
*1 Results were expressed in mean ± standard error from duplicate analyses.
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*2 25% total lipid content
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Table 2. Fatty acid profile of algal oil (total lipid) extracted through this fractional extraction and reference method Extraction method
16:0
16:1
18:0
18:1
18:2
18:3
20:0
20:1
Others
Reference/%
36.2
2.87
3.3
24.5
19.2
11.1
0.71
1.11
1.01
Fractional/%
35.8
3.1
3.2
23.7
18.7
12.3
361
0.57
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1.31
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Table 3. Textural and chemical properties of Meso-ZSM-5 and Pt/Meso-ZSM-5 SBET
V meso
Vmicro
V total
(mL/g)
(mL/g)
(mL/g)
4.73
0.47
0.08
0.55
4.52
0.47
0.07
0.54
2
Dpore (nm)
Meso-ZSM-5
483
Pt/Meso-ZSM-5
479
Zeolite
(m /g)
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Neutral lipid Neutral lipid
Polar lipid Polar lipid
100
80
16
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Lipid recovery (% of Lipid)
18
12
60
10 8
40
6 4
20
2 0
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Lipid recovery (% of DW)
20
Total lipid Total lipid
0
1
2
3
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Figure 1. Algal oil extraction performance with ethanol/hexane solvent system. The total,
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polar and neutral lipid recovery to lipid are calculated with the overall total lipid, polar
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lipid and neutral lipid as 100%, respectively. Results were expressed in mean ± standard
369
error from duplicate extraction. The left y-axis corresponds to the bar graph, and the right
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y-axis corresponds to the line graph.
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1600
Oil extracted by common method Oil extracted by fractional method
6 4
800
2 0
Ca
Mg
Cu
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0 Ca
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Metal content (ppm)
1200
Mg
Cu
Metals
Figure 2. Difference of metal content of algal oil in reference sample and oil extracted by
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the developed fractional approach. Results were expressed in mean ± standard error from
373
duplicate extraction.
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Meso-ZSM-5
500
400
Pt/Meso-ZSM-5 300
200
Meso-ZSM-5
100
0 10
20
30
40
50
0.0
0.2
0.4
0.6
0.8
1.0
Relative Pressure (P/P0)
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2θ (degree)
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Volume Adsorbed (cm3/g, STP)
Intensity (a.u.)
600
Figure 3. XRD patterns (a) and nitrogen adsorption isotherms (b) of Meso-ZSM-5 and
376
Pt/Meso-ZSM-5 (The y axis offset of Pt/Meso-ZSM-5 in (b) is 150 cm3/g, respectively);
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HRTEM images of the synthetic Meso-ZSM-5 (c) and Pt/Meso-ZSM-5 (d)
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Oil extracted by fractional method
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90
80
70
1st run 2nd run 3rd run
Oil extracted by common method
60 0
20
40
60
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Conversion (%)
100
80
100
379
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Figure 4. Catalytic performance of the algal oil samples over the Pt/Meso-ZSM-5
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catalyst. Catalytic conversion was repeatedly investigated using neutral lipid rich algal oil
382
extracted from two different batches.
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20 18
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Relative content (%)
16
12 10 8 6
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iC 9 nC 9 iC 10 nC 10 iC 11 nC 11 iC 12 nC 12 iC 13 nC 13 iC 14 nC 14 iC 15 nC 15 iC 16 nC 16
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Carbon number
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Figure 5. Carbon chain length of jet fuel products from neutral lipid rich algal oil
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Highlights Algal oil was extracted directly from wet algae with high efficiency (>90%) Fractional extraction achieved with renewable ethanol and hexane as solvent
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Neutral lipid rich oil has very low metal content
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Neutral lipid rich oil was directly converted into jet fuel over Pt/Meso-ZSM-5