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Characteristics of vacuum fractional distillation from pyrolytic macroalgae (Saccharina japonica) bio-oil
G Model JIEC 3315 No. of Pages 10
Journal of Industrial and Engineering Chemistry xxx (2016) xxx–xxx
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Characteristics of vacuum fractional distillation from pyrolytic macroalgae (Saccharina japonica) bio-oil Jae Hyung Choia , Seung-Soo Kimb,* , Hee Chul Wooa,** a b
Department of Chemical Engineering, Pukyong National University, 365 Sinseon-ro, Nam-gu, Busan 48513, Republic of Korea Department of Chemical Engineering, Kangwon National University, 346 Joongang-ro, Samcheok-si, Gangwon-do 25913, Republic of Korea
A R T I C L E I N F O
Article history: Received 1 February 2017 Received in revised form 21 February 2017 Accepted 4 March 2017 Available online xxx Keywords: Vacuum fractional distillation Bio-oil Fuel blend Fuel property Brown alga Saccharina japonica
A B S T R A C T
Crude bio-oil from the brown alga Saccharina japonica was separated into distilled fractions under reduced pressure (40 mmHg). The three bio-oil distillates were depending on temperature (Fraction I; 40 C, Fraction II; 40–120 C, Fraction III; 120–160 C, solid residue; b.p. > 160 C). The characteristic of the middle distillates showed that aliphatics (including alkanes) and aromatics (including heterocyclics) were mostly distributed in a dark hydrophobic oil (DHO) of Fractions II and III, while anhydrosugars, acids, ketones and ethers were mainly concentrated in a transparent hydrophilic oil (THO) of Fractions II and III. © 2017 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.
Introduction The need for sustainable energy security, as well as the need to address global warming will limit the use of fossil fuels for power generation and transportation in the future. Alternative energy technologies have emerged and are currently under investigation. Among these, biomass has great potential to contribute to renewable energy resources and extensive research is underway for converting it into fuels and chemicals [1–6]. Macroalgae as aquatic biomass can convert solar energy into chemical energy with higher photosynthetic efficiency (6–8% on average) than terrestrial biomass (1.8–2.2% on average) [7]. In addition, macroalgae have competitive advantages such as short life cycle (3–4 months), high productivity, efficient CO2 fixation, and less competition with food crops and farmland [8,9]. Despite the environmental and economic merits of macroalgae, there are still many challenges associated with biofuel production from macroalgae. These involve key processes such as feedstock mass production, suitable pretreatment, and process integration to minimize energy demands [10]. Pyrolysis has received special attention because it can convert biomass directly into energy products that could be used
* Corresponding author. Fax: +82 33 570 6535. ** Corresponding author. Fax: +82 51 629 6929. E-mail addresses: [email protected] (S.-S. Kim), [email protected] (H.C. Woo).
successfully for the production of heat, power, and chemicals [11]. Fast pyrolysis in the absence of oxygen, can produce a liquid product known as bio-oil, a solid residue (bio-char), and several light gaseous compounds (e.g., carbon dioxide, carbon monoxide, hydrogen, and light hydrocarbons) [12]. Crude bio-oil is generally a complex dark brown mixture, and mainly includes water and hundreds of oxygenated organic compounds such as aldehydes, alcohols, carboxylic acids, esters, ethers, furans, ketones, phenols, and anhydrosugars [13]. The crude bio-oil is hard to use directly as a fuel because of its low heating value, high viscosity, high water and oxygen content, and instability due to the presence of unsaturated and phenolic moieties [14]. These qualities must be taken into careful consideration when it is to be used as a fuel for generating heat and electricity [15]. The current techniques have reported in the literature for upgrading bio-oil involved in distillation, solvent extraction, emulsification, supercritical fluid, hydro treatment, hydrocracking, and steam reforming [11]. In addition to these approaches to bio-oil upgrading and separation technology (bio-oil distillation) can also provide a source of valuable chemicals and useful fuels [15,16]. The most extensively used separation technique in petrochemical refinery is conventional atmospheric distillation. This technique can also be the most economically feasible pathway to separate the complex bio-oil mixture into chemical fractions and upgrade the fuel sources via biorefinery development. However, the high temperatures needed for atmospheric distillation can cause formation of unexpected products from bio-oil. Hence, tremendous efforts have been made to mitigate the aforementioned problems [17]. Distillation under
http://dx.doi.org/10.1016/j.jiec.2017.03.002 1226-086X/© 2017 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.
Please cite this article in press as: J.H. Choi, et al., Characteristics of vacuum fractional distillation from pyrolytic macroalgae (Saccharina japonica) bio-oil, J. Ind. Eng. Chem. (2017), http://dx.doi.org/10.1016/j.jiec.2017.03.002
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mixture could provide information useful for setting the quality standards of bio-oil based fuels.
Nomenclature
American Society for Testing and Materials Dark hydrophobic oil Elemental analyzer Fourier transform infrared Gas chromatography–mass spectrometry Higher heating value Korea Petroleum Quality and Distribution Authority NMR Nuclear magnetic resonance OFDB Organic fraction of distilled bio-oil PAHs Polycyclic aromatic hydrocarbons S. japonica Saccharina japonica TG Thermogravimetric THO Transparent hydrophilic oil ASTM DHO EA FT-IR GC–MS HHV KPetro
reduced pressure requires a lower distillation temperature, and can be used to reduce the occurrence of distillation residue and aging reaction [17,18]. Recently, Nam et al. [19] reported that microalgae pyrolytic bio-oil was separated into three fractions compared with atmospheric and vacuum distillation. The light and middle fractions showed 40–41 MJ/kg as high potential for transportation fuels. However, the distillation characteristics of macroalgae pyrolytic bio-oil have still been investigated as limited studies. In this study, crude bio-oil derived from the brown alga Saccharina japonica was separated into three distillates under reduced pressure (40 mmHg) within the temperature range 25– 160 C. The objectives of this study were to qualitatively identify and quantify the components in distillate fractions, and to obtain stable chemical fractions for use in alternative fuel and chemicals. The blend-testing of the bio-oil distillate with petroleum-based heavy oil is the first trial in this work. The fuel properties of the
Experimental Bio-oil distillation The brown alga S. japonica (the feedstock) was supplied from Wando Island, Republic of Korea. The crude bio-oil used in this study was produced by fast pyrolysis in a fixed-bed reactor at 450 C. A detailed description of the reactor system and experimental procedure has been described [20]. As shown in Fig. 1, the distillation system consisted of a round bottom flask, a jacketed distillation column with 10-theoretical plates (Catalog #6566-05, ACE Glass Inc.), and a receiver connected to the vacuum pump (N840 Diaphragm Pump, KNF, Germany). The temperature was monitored by inserting a thermocouple in the distillation tip and a round bottom flask through the other neck. In a typical distillation run, 1.2 kg of crude bio-oil was put in a round bottom flask. Distillation fractions were collected at various range of vapor temperature monitored from distillation tip. The yield of each fraction was calculated from initial weight of crude bio-oil. Choi et al. in our previous study reported that the moisture content of crude bio-oil derived from raw S. japonica was in range of 55.13– 72.35 wt% in fixed-bed [20], microtubing [21], and fluidized-bed reactor [22]. The high amount of water contained in crude bio-oil need to be vaporized at low temperature (<40 C) under 40 mmHg because it is thermally unstable. The distillation of bio-oil at a constant 40 mmHg was carried out according to ASTM D2892, and replicated three times to confirm the reproducibility. The standard deviation of each run reported in experimental results. All of the organic fractions of the bio-oil distillates obtained between 40 and 160 C at 40 mmHg were blended with No. 6 fuel oil which was supplied from Korea Petroleum Quality and Distribution Authority (KPetro). A total of 500 mL of blends containing 5 and 10 vol% of the organic fraction were prepared. For characterization of fuel properties, those of blends to
Fig. 1. Schematic diagram of a reduced pressure distillation apparatus.
Please cite this article in press as: J.H. Choi, et al., Characteristics of vacuum fractional distillation from pyrolytic macroalgae (Saccharina japonica) bio-oil, J. Ind. Eng. Chem. (2017), http://dx.doi.org/10.1016/j.jiec.2017.03.002
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homogenization were stirred at 40 5 C for 24 h in 1000 mL sealed round-bottom flask. Analysis methods The moisture content of the bio-oil distillate samples was determined by Karl–Fischer (CA-200, Mitsubishi) titration according to the ASTM E203 method. Elemental compositions (C, H, O, N, and S) of the bio-oil distillates were determined with the following elemental analyzers: the content of carbon, hydrogen, and nitrogen (FLASH 2000, Thermo Scientific, ASTM D5291), the sulfur content (NSX–2100 V, Mitsubishi Chemical Analytech, ASTM D4294), and the oxygen content (FLASH 1112 series, Thermo Finnigan, ASTM D5622). The average value of three replicate measurements of the samples was reported according to ASTM test methods in KPetro. The organic components of the bio-oil distillates were qualitatively identified with gas chromatography–mass spectrometry (GC–MS 7890A, Agilent Technologies, HP–5 ms capillary column, 60 m 0.25 mm 0.25 mm). The GC oven temperature was held at 40 C for 5 min, and was programmed to ramp at 5 C/ min to 300 C. Then, the oven temperature was kept at 300 C for 10 min. The injector temperature was 280 C, and an injection volume of 1 mL was adopted, with the split ratio set as 50:1. The mass spectrometer was operated in full scan mode, and its mass range was 30–300 atomic mass units. The identification of the chromatographic peaks was based on an automatic library search (NIST library version 2.0). The functional groups of the bio-oil distillate samples were measured by Fourier Transform Infrared Spectroscopy (Nicolet iS50R, Thermo Scientific) with the attenuated total reflectance (ATR) method. The 1H and 13C Fourier Transform Nuclear Magnetic Resonance Spectrometer (FT-NMR) spectra were determined using a JEOL JMS ECP-400 spectrometer at 400 MHz in deuterated solvents (i.e., CCl3D-d for a hydrophobic oil and DMSO-d6 for a hydrophilic oil). The proximate analysis of the solid residue from distillation determined the moisture and ash contents according to the ASTM E1755 and E1756, respectively. Volatile matter was determined using a non-isothermal thermogravimetric (TG) method that followed the ASTM E872 method. Fixed carbon was a calculated value of the difference between 100 and the sum of the moisture, ash, and volatile matter, where all values were on the same moisture reference base. The elemental composition (C, H, N, and S) of the solid residue was determined using an elemental analyzer (Vario macro/micro, Elementar, ASTM D5373). The metal compositions (Ca, K, Mg, Na, and P) of the solid residue were analyzed using an ICP–OES (Optima 5300DV, Perkin Elmer). The average value of three replicate measurements of the sample was reported. The higher heating value (HHV) of the solid residue was then estimated by the correlation of Channiwala and Parikh [23].
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The fuel properties of the bio-oil distillate and blends were determined as follows: HHV (6400EF, Paar, ASTM D240), moisture content (CA-200, Mitsubishi, ASTM E203), kinematic viscosity (CAV-2100, Cannon Instrument Company, ASTM D445), density (DMA 4500, Anton Paar, ASTM D4052), ash content (Muffle furnace, Fisher Scientific, ASTM D482), pH (SevenCompact S220, Mettler Toledo, ASTM E 70), flash point (ATM-7, Tanaka, ASTM D93), pour point (MPC-602, Tanaka, ASTM D97), and water and sediment (Rotanta460R, Hettich, ASTM D2709). The experiments were replicated three times to confirm the repeatability and the reproducibility of the reported results according to ASTM test methods in KPetro. Results and discussion Bio-oil distillation yields As shown in Table 1, the three distilled fractions and residue from the crude bio-oil were obtained at temperature 25–160 C at 40 mmHg: Fraction I (first distillate, b.p. 40 C), Fraction II (second distillate, 40 C < b.p. 120 C), Fraction III (third distillate, 120 C < b.p. 160 C), and the residue (solid residue, b.p. > 160 C). The second and third distillates obtained at 40–160 C and 40 mmHg, separated into two phases (a dark hydrophobic oil (DHO) top layer, and a transparent hydrophilic oil (THO) bottom layer). This phenomenon is due to high moisture content as well as to different polarities of sugars, aliphatics, and aromatics in bio-oil [24]. A small weight loss could be obtained by fast evacuation of vapor during reduced pressure condition [25]. The yield of Fraction I (water-rich fraction) was 58.05 wt%, and had a moisture content of 89.61 wt%. The considerable amount of moisture in Fraction I was evaporated at saturated water vapor pressure (34.1 C and 40 mmHg), and originated from dehydration reactions during biomass pyrolysis, as well as from moisture within the biomass itself [18,25]. The yields of Fractions II and III THOs were 7.06 and 11.67 wt%, respectively (and their moisture contents were 51.40 and 10.28 wt%, respectively). The moisture content in Fractions II and III gradually decreased. However, at higher temperature, most of the remaining water was caused by dehydration reactions in unstable compounds in Fractions II and III [18]. The yields of the Fractions II and III DHOs were 1.43 and 4.88 wt%, respectively, and their moisture contents were 5.86 and 1.30 wt%. The H/C ratios of Fractions II and III were in the range 1.54–1.69, which were closer to the values for cyclics and aromatics than to those of alkanes [26]. The O/C ratios of the bottom layer oils were 0.53–1.16, and those values were larger than the top layer oils (0.11–0.16). Choi et al. [27] reported that the higher O/C ratio was affected by large amounts of moisture and oxygenated compounds. The solid residue (15.4 wt%) was obtained, and was a sticky, high-molecular-weight material. It is considered that the lower H/C ratio of the residue is due to a high
Table 1 Results of reduced pressure distillation of S. japonica bio-oil. Distillation temperature ( C)
Yield (wt%, wet basis)
Moisture content (wt%)
Ultimate analysis (wt%, wet basis) C
Fraction I Fraction II Top layer (DHO) Bottom layer (THO) Fraction III Top layer (DHO) Bottom layer (THO) Solid residue Loss a
<40 40–120
120–160
>160
58.05 2.02 8.49 0.71 1.43 0.47 7.06 0.24 16.55 0.67 4.88 0.34 11.67 1.01 15.35 0.46 1.56 0.17
H
O
H/Ca
O/Ca
89.61 2.40
1.36
10.06
85.63
0.28
3.34
5.86 0.62 51.40 1.91
66.82 16.94
9.29 8.07
19.60 71.87
1.54 1.63
0.16 1.16
1.30 0.21 10.28 1.12
73.48 47.24 68.63
10.59 7.80 5.54
12.31 42.39 20.50
1.69 1.68 0.96
0.11 0.53 0.22
Appearance
Bright yellow Phase separation Dark brown Yellow orange Phase separation Dark brown Yellow green Black
Determined by molar ratio on dry basis.
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degree of unsaturated structures formed by condensation polymerization [18]. The chemical properties of the solid residue were characterized by proximate and ultimate analysis (Table 2). The abundant carbon (68.6 wt%) and hydrogen (5.5 wt%) are the principal combustible elements in the solid residue. The high concentration of volatile matter can be easy to ignite, whereas the highly fixed carbon content tends to burn for a long time with a smoky flame [28]. The trace ash of burned solid residue is attributed to inherent mineral components of the brown algal biomass. GC–MS analysis The GC–MS total ion chromatograms of bio-oil distillates obtained at each temperature range were compared in Fig. 2. All of the bio-oil distillates were analyzed without dilution of the samples for comparing each peak area. The main peaks of Fractions I and III-THO indicated furan derivatives [e.g., 1-(2-furanyl)ethanone, dihydro-2(3H)-furanone] and dianhydrohexitols (e.g., dianhydromannitol, isosorbide as oxygenated compounds), respectively (Supplementary Tables S1 and S3). It is worth mentioning that their distillates have the potential to be further separated into pure bio-chemicals using their different boiling points (i.e., via distillation) [16,29,30]. The chromatograms of Fractions II and III DHOs showed unseparated peak resolution with a rising baseline during the GC–MS analysis (Fig. 2). This phenomenon implies that the low-polarity column (HP–5 ms) may have great difficulty separating the non-polar compounds in these fractions. The main components of the bio-oil distillates identified in the GC–MS are exhibited in Fig. 3. The major components were qualitatively identified with accuracy above 85% by comparing them with the NIST Spectral Mass Library. The components detected in each of the bio-oil distillates were classified into acids, aliphatic ketones, furans, cyclics, heterocyclics, other aliphatics, aromatics, phenolics, polycyclic aromatic hydrocarbons (PAHs), sugars, and esters (Fig. 3 and Supplementary Tables S1–S5). This list of components was then compared with one from crude bio-oil derived from S. japonica as reported by Kim et al. [31]. The acids (e.g., carboxylic acid of C2–C4 and C14–C16) and aliphatic ketones (e.g., 2-propanone and 1-hydroxy-2-propanone) were mainly distributed in all of the fractions (Supplementary Tables S1–S5). The water is not completely removed from the bio-oil fractions because of H-bonding interactions between the acids and ketones [13,32]. The furan derivatives (e.g., 1-(2-furanyl)-ethanone, dihydro-2(3H)-furanone); cyclic components (e.g., cyclopentenones and cyclohexenone of methyl, ethyl, and hydrooxy groups); and heterocyclic components (e.g., pyridine, pyrazines, and pyrroles of methyl and ethyl groups) as biofuel sources were mainly found to be distributed in Fractions I and II (Supplementary Tables S1–S3). Also, the aliphatic compounds (e.g., n-alkane and alkene series of C15–C20); benzenes (e.g., benzenes of methyl and ethyl groups); phenolics (e.g. phenols of methyl and ethyl groups); and PAHs (e.g.
1H-indenes and naphthalenes of methyl and ethyl groups) as sources for biofuels, were mainly distributed in the Fractions II and III DHOs (Supplementary Tables S3 and S5). The sugar diols (e.g., dianhydrohexitols of dianhydromannitol and isosorbide) were mainly distributed in the Fraction III THO (Supplementary Table S4). The sugar diols could be used to synthesize or modify polycondensates like polycarbonates or epoxy resins [33]. Compared to normal aliphatic diols, their attractive feature as monomers is linked to their rigidity, chirality, non-toxicity, and thermomechanical stability [34]. The sugar diols derived from renewable resources could have the potential to reduce petroleum-based polymers in the field of polymeric materials. The esters (e.g., C14–C18 methyl esters of fatty acids) were mainly distributed in the Fraction III DHO (Supplementary Table S5). The long chain fatty acids (C14–C18) from the esters are derived from lipids [26]. The carboxylic acid derivatives could be attributed to esterification or aldol condensations with carboxylic acids, alcohols, and aldehydes during distillation. FT-IR analysis The FT-IR spectra of the bio-oil distillates are shown in Fig. 4. The broad bands of O-H stretching vibrations between 3600 and 3200 cm1 indicate the presence of water, carboxylic acids, alcohols, and phenols in the Fractions I, II- and III-THOs (Supplementary Tables S1, S2, and S4). The aliphatic C-H vibrations at 3000–2850 cm1 (stretching) and at 1375 cm1 (bending) showed the presence of alkanes associated with CH2- and CH3. The bands at 1600 and 1470 cm1 appeared to be characteristic of the C¼C vibration of aromatic compounds that come mainly from the Fractions II and III DHOs (Supplementary Tables S3 and S5) [35]. The strong bands between 1640 and 1720 cm1 were assigned to C¼O functional groups, possibly from carboxylic acids, esters, ketones, and aldehydes, in all of the fractions (Supplementary Tables S1–S5). The bands between 1150 and 1000 cm1 were assigned to C-O-C groups from ether linkages specifically present in carbohydrate derivatives from the Fraction III THO (Supplementary Table S4) [36]. NMR analysis The 1H NMR spectra with main signal characteristics of functional groups such as aliphatics, aromatics, and carbohydrates in each bio-oil distillates are exhibited in Fig. 5. In the 1H NMR spectra, it was possible to identify four main regions. The first region from 0.5 to 3.0 ppm represents protons on aliphatic carbon atoms related to heteroatoms or unsaturated groups [37,38]. These were mainly exhibited in the Fractions II and III DHOs (Supplementary Tables S3 and S5). The second proton region between 3.0 and 4.5 ppm was assigned to hydroxyl and methoxy groups on anhydrosugars or alcohols [37,39], and was attributed to carbohydrate derivatives (e.g., dianhydrohexitols) mainly in the Fraction III THO (Supplementary Table S4). The third region peak between 4.5
Table 2 Proximate and ultimate analysis, heating value, and metal content of solid residue. Proximate analysis (wt%)
Solid residue a b c d e
Ultimate analysis (wt%, dry basis)
Moisturea
Volatile matterb
Fixed carbonc
Ashd
C
H
N
S
O
0.01 0.01
50.78
49.12
0.10 0.02
68.63
5.54
4.72
0.62
20.50
HHVe (MJ/kg)
28.35
Metal content (ppm) Ca
K
Mg
Na
P
24
265
20
47
370
Determined according to the ASTM E1756 standard method. Determined by thermogravimetric analysis. By difference. Determined according to the ASTM E1755 standard method. The higher heating value (HHV) was estimated by the correlation of Channiwala and Parikh [23].
Please cite this article in press as: J.H. Choi, et al., Characteristics of vacuum fractional distillation from pyrolytic macroalgae (Saccharina japonica) bio-oil, J. Ind. Eng. Chem. (2017), http://dx.doi.org/10.1016/j.jiec.2017.03.002
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Fig. 2. Total ion chromatograms of (a) Fraction I, (b) Fraction II-THO, (c) Fraction II-DHO, (d) Fraction III-THO, and (e) Fraction III-DHO.
Please cite this article in press as: J.H. Choi, et al., Characteristics of vacuum fractional distillation from pyrolytic macroalgae (Saccharina japonica) bio-oil, J. Ind. Eng. Chem. (2017), http://dx.doi.org/10.1016/j.jiec.2017.03.002
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Fig. 3. Component distributions of bio-oil distillates identified by GC–MS with accuracy above 85%.
ketones, and carboxylic acids in all of the fractions (Supplementary Tables S1–S5) [37,38]. Overall, the NMR and FT-IR analyses showed that the characteristics of aliphatic, aromatic, and carbohydrate derivative groups were the most prevalent for each of the bio-oil distillates derived from brown algae. Mullen et al. [38] reported that aliphatic protons are most prevalent for wood-based bio-oil, while protons proximal to heteroatoms (alcohols, carbohydrates) are highly concentrated in grass-based bio-oil. Fuel properties
Fig. 4. FT-IR spectra of (a) Fraction I, (b) Fraction II-THO, (c) Fraction II-DHO, (d) Fraction III-THO, and (e) Fraction III-DHO.
and 6.0 ppm represents hydrogen bonding in phenolic OH and non-conjugated olefin groups [37,39], and stem from phenols and olefins in the Fractions II and III DHOs (Supplementary Tables S3 and S5). The fourth one between 6.0 and 8.5 ppm represents the hydrogen atoms in benzenoids and heteroaromatics containing O and N [37,38], and originate from heteroaromatics in the Fractions II and III DHOs (Supplementary Tables S3 and S5). As shown in Fig. 6, the 13C NMR spectra of each of the bio-oil distillates also indicated four main functional groups. From 10 to 50 ppm, the aliphatic carbons from CH3 and CH2 were present in all of the fractions (Supplementary Tables S1–S5). The region between 60 and 90 ppm was assigned to aliphatic carbons bound to oxygen [37,40], which was attributed to the carbohydrate derivatives obtained mainly from Fraction III THO (Supplementary Table S4). The signals from 100 to 160 ppm were attributed to aromatic rings or double bonded carbons in the Fraction II DHO (Supplementary Table S3) [35]. From 160 to 180 ppm, the signals were assigned to carbon from carbonyl groups as aldehydes,
Biomass-derived bio-oils have characteristics very different from petroleum-based fuels, as regards both physical properties and chemical composition. Crude bio-oil is typically composed of multicomponent mixtures of oxygenated hydrocarbons with an appreciable proportion of water obtained from both the original moisture and reaction product. Moreover, it has been reported that the bio-oils from macroalgae have higher water content (26.6– 70.7 wt%) than those from lignocellulosic biomass [24,41,42]. Chiaramonti et al. [43] reported that water content >30 wt% in biooil could be separated into two immiscible phases. Hence, the unusual properties of these bio-oils should be taken into careful consideration, if they are to be used for the generation of heat and power by combustion in boilers, burners, gas turbines, and diesel engines. In this study, an organic fraction (i.e., a mixture of Fractions II and III DHOs) from crude bio-oil of S. japonica was prepared by distillation at 40–160 C at 40 mmHg. The fuel properties of the organic fraction of distilled bio-oil (OFDB) for use as alternative liquid fuels are summarized in Table 3. The OFDB exhibited excellent fuel properties compared to crude bio-oil from S. japonica [31]. Especially, it meets all of the specifications of No. 4 fuel oil (ASTM D396) for use in commercial and/or industrial burners [HHV (33.5 MJ/kg), moisture (0.84 wt%), kinematic viscosity (16.54 at 50 C), density (1.03 kg/m3 at 20 C), ash (0.00 wt%), pH (4.9), flash point (71 C), and pour point (25 C), and water and sediment (< 0.1)]. However, the sulfur content (0.2 wt%) of the OFDB does not meet the specification (<0.05 wt%) of ASTM D7544. The OFDB could be blended with fuel oils to meet the desired specification in commercial or industrial burners [44]. The HHV of the OFDB was significantly higher (by four times) than crude bio-
Please cite this article in press as: J.H. Choi, et al., Characteristics of vacuum fractional distillation from pyrolytic macroalgae (Saccharina japonica) bio-oil, J. Ind. Eng. Chem. (2017), http://dx.doi.org/10.1016/j.jiec.2017.03.002
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Fig. 5. 1H NMR spectra of (a) Fraction I, (b) Fraction II-THO, (c) Fraction II-DHO, (d) Fraction III-THO, and (e) Fraction III-DHO.
Please cite this article in press as: J.H. Choi, et al., Characteristics of vacuum fractional distillation from pyrolytic macroalgae (Saccharina japonica) bio-oil, J. Ind. Eng. Chem. (2017), http://dx.doi.org/10.1016/j.jiec.2017.03.002
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Fig. 6.
13
C NMR spectra of (a) Fraction I, (b) Fraction II-THO, (c) Fraction II-DHO, (d) Fraction III-THO, and (e) Fraction III-DHO.
Please cite this article in press as: J.H. Choi, et al., Characteristics of vacuum fractional distillation from pyrolytic macroalgae (Saccharina japonica) bio-oil, J. Ind. Eng. Chem. (2017), http://dx.doi.org/10.1016/j.jiec.2017.03.002
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Table 3 Fuel properties of the organic fraction of distilled bio-oil (OFDB) in comparison with crude bio-oil, pyrolysis liquid biofuel, and Nos. 4 and 6 fuel oils.a Properties
Methods
OFDBb
Crude biooilc
Pyrolysis liquid biofuel (ASTM D7544)
No. 4 fuel oil (ASTM D396) No. 6 fuel oild (Bunker C oil)
HHV (MJ/kg) Moisture content (wt%) Kinematic viscosity (mm2/ s) Density (kg/dm3)
ASTM D240 ASTM E203 ASTM D445
33.5 0.84 16.54 at 50 C 1.03 at 20 C
8.7 70.7 n/a
>15 <30 <125 at 40 C
n/a n/a <24 at 40 C
40 0.1 351 at 50 C
n/a
1.1–1.3 at 20 C
>0.87 at 15 C
0.94–0.96 at 15 C
0.00 4.9 71.0 25 <0.1
n/a 6.9 n/a n/a n/a
<0.15 Report >45 <9 n/a
<0.10 Report >55 <6 <0.5
0.03 n/a 100 21 <1.0
71.6
16.2
n/a
n/a
85.6
9.0
10.2
n/a
n/a
10.3
2.5
<0.3
n/a
n/a
0.6
0.2
<0.3
<0.05
n/a
2.5
15.9
63.9
n/a
n/a
0.6
132 15 24 0 37
n/a n/a n/a n/a n/a
n/a n/a n/a n/a n/a
n/a n/a n/a n/a n/a
ASTM D4052 ASTM D482 Ash content (wt%) pH ASTM E70 Flash point ( C) ASTM D93 Pour point ( C) ASTM D97 Water and sediment (vol%) ASTM D2709 Elemental composition (wt%) Carbon ASTM D5291 ASTM Hydrogen D5291 ASTM Nitrogen D5291 ASTM Sulfur D4294 ASTM Oxygen D5622 Metal content (ppm) Ca K Mg Na P a b c d
The experiments were replicated three times to confirm the repeatability and reproducibility of the reported results according to ASTM test methods in KPetro. All of the organic fraction of Fractions II and III as OFDB was obtained by distillation between 40 and 160 C at 40 mmHg. Choi et al. [26]. Chiaramonti et al. [43].
oil (8.7 MJ/kg) [31], and the value was slightly lower than No. 6 fuel oil (Bunker C oil) [43]. This observation indicates that the presence of water has both negative and positive effects on the fuel properties. Czernik and Bridgwater [15] reported that the addition of water to bio-oil reduced the heating value and viscosity, whereas it was beneficial for pumping and atomization during combustion. The No. 6 fuel oil can be economically mixed with the OFDB to improve its fuel properties expect for the HHV. However, to blend with diesel or No. 4 fuel oil, the catalytic upgrading with increasing process cost is required to improve the properties of the OFDB. The kinematic viscosity of OFDB was twenty-one times lower than that of the No. 6 fuel oil. In general, lower viscosity makes it easier to pump and lubricate, whereas higher viscosity fuels cause incomplete combustion by increasing the spray droplets [41]. The ash content was not detected in the OFDB. This means that ash
existing in biomass was bound to the bio-char during pyrolysis. The pH value (pH 4.9) of the OFDB was lower than those of crude bio-oil (pH 6.9) [26] and organic phase (pH 5.96) from crude bio-oil [37]. The acidic pH of the OFDB is affected by carboxylic acids included in the Fractions II and III DHOs (Fig. 3, Supplementary Tables 3S and 5S). The flash and pour point could be determined depending on the chemical composition of the bio-oil. The flash point (71 C) of the OFDB was lower than that of No. 6 fuel oil (100 C) [43], and higher than those of light fuel oil (60 C) [43] and mineral oil (>65 C) [44,45]. A flash point above 45 C (as an indicator of safety for storage and transportation) is recommended based on the ASTM D7544 standard for burner fuels [45,46]. The pour point (25 C) of the OFDB was significantly lower than that of No. 6 fuel oil (21 C) [43], and similar to those of light fuel oil (15 C) [43] and mineral oil (5 to 15 C) [44,45]. The pour point is an indication of the lowest temperature at which a fuel could be
Table 4 Fuel properties of No. 6 fuel oil, OFDB, and No. 6 fuel oil/OFDB blends.a Properties
Methods
Fuel specification of Bunker C fuel oilb
No. 6 fuel oilc (Bunker C fuel oil)
Flash point ( C) Kinematic viscosity at 50 C (mm2/s) Water and sediment (vol%) Sulfur (wt%)
ASTM ASTM ASTM ASTM
>70 <540 <1.0 <4.0
85.5 283.5 0.125 3.301
a b c d
D93 D445 D2709 D4294
No. 6 fuel oil/OFDB blends 95/5
90/10
83.5 241.3 <0.1 3.113
81.5 182.9 <0.1 2.931
OFDBd
71.0 16.5 <0.1 2.203
The experiments were replicated three times to confirm the repeatability and reproducibility of the reported results according to ASTM test methods in KPetro. Fuel specification for Bunker C fuel oil according to Petroleum and Petroleum Substitute Fuel Business Act in Republic of Korea. No. 6 fuel oil was supplied by KPetro. All of the organic fraction of Fractions II and III as OFDB was obtained by distillation between 40 and 160 C at 40 mmHg.
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pumped. Rick and Vix [47] reported that the recommended upper limit for pumpability is about 600 mm2/s. As discussed in Table 3, the OFDB could potentially substitute for fuel oils. Its mixture with petroleum based heavy oil as a method to lower cost, could be expected to result in fuel properties similar to commercial fuels. Such mixes could be used as fuels in burners or combustion engines for heat and power generation. Table 4 shows the fuel properties when a 5 and 10 vol% of OFDB was mixed with No. 6 fuel oil (Bunker C fuel oil). The ignition delay (flash point) and kinematic viscosity of No. 6 fuel oil were decreased by blending with the OFDB. The sulfur content of the OFDB blends was lower than that of the No. 6 fuel oil as well. The water and sediment values of the OFDB blends was less than 0.1 vol %. The addition of up to 10% OFDB in No. 6 fuel oil could improve combustion stability and reduce sulfur emission in combustion systems. However, a blend with >10% OFDB with No. 6 fuel oil, could present the problem of immiscibility due to the high oxygen content (15.9 wt%) of the OFDB (Table 3). Further research is required to improve the physical upgrading process or to develop fuel optimization techniques such as emulsification and additive blending [48]. Conclusions The bio-oil distillates from brown alga S. japonica for potential alternative petroleum-based fuels and chemicals were systematically characterized. The three distilled fractions from crude bio-oil were obtained at temperatures in the range 25–160 C at 40 mmHg. The H/C ratio of Fractions II and III was in the range 1.54–1.69, which was closer to the value for aromatics than for alkanes. The main components of the bio-oil distillates were acids, aliphatic ketones, furans, cyclics, heterocyclics, other aliphatics, aromatics, phenolics, polycyclic aromatic hydrocarbons (PAHs), sugars, and esters. The 1-(2-furanyl)-ethanone, dianhydromannitol, and isosorbide for bio-chemical intermediates were present in transparent hydrophilic oils (bottom layers) of the bio-oil distillates. The fuel properties of the OFDB and its mixture with No. 6 fuel oil were analyzed, and included such as HHV, moisture, kinematic viscosity, density, ash, pH, flash and pour point, and water and sediment. Considering the high water and ash content, high viscosity, and unacceptable flash and pour points of crude S. japonica bio-oil, it could only be used directly, as a substitute for No. 6 fuel oil. Acknowledgement This work was financially supported by the Ministry of Oceans and Fisheries of Korea (Project No. 20140559). Appendix A. Supplementary data Supplementary data associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/j.jiec.2017.03.002.
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Characteristics of vacuum fractional distillation from pyrolytic macroalgae (Saccharina japonica) bio-oil Jae Hyung Choia , Seung-Soo Kimb,* , Hee Chul Wooa,** a b
Department of Chemical Engineering, Pukyong National University, 365 Sinseon-ro, Nam-gu, Busan 48513, Republic of Korea Department of Chemical Engineering, Kangwon National University, 346 Joongang-ro, Samcheok-si, Gangwon-do 25913, Republic of Korea
A R T I C L E I N F O
Article history: Received 1 February 2017 Received in revised form 21 February 2017 Accepted 4 March 2017 Available online xxx Keywords: Vacuum fractional distillation Bio-oil Fuel blend Fuel property Brown alga Saccharina japonica
A B S T R A C T
Crude bio-oil from the brown alga Saccharina japonica was separated into distilled fractions under reduced pressure (40 mmHg). The three bio-oil distillates were depending on temperature (Fraction I; 40 C, Fraction II; 40–120 C, Fraction III; 120–160 C, solid residue; b.p. > 160 C). The characteristic of the middle distillates showed that aliphatics (including alkanes) and aromatics (including heterocyclics) were mostly distributed in a dark hydrophobic oil (DHO) of Fractions II and III, while anhydrosugars, acids, ketones and ethers were mainly concentrated in a transparent hydrophilic oil (THO) of Fractions II and III. © 2017 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.
Introduction The need for sustainable energy security, as well as the need to address global warming will limit the use of fossil fuels for power generation and transportation in the future. Alternative energy technologies have emerged and are currently under investigation. Among these, biomass has great potential to contribute to renewable energy resources and extensive research is underway for converting it into fuels and chemicals [1–6]. Macroalgae as aquatic biomass can convert solar energy into chemical energy with higher photosynthetic efficiency (6–8% on average) than terrestrial biomass (1.8–2.2% on average) [7]. In addition, macroalgae have competitive advantages such as short life cycle (3–4 months), high productivity, efficient CO2 fixation, and less competition with food crops and farmland [8,9]. Despite the environmental and economic merits of macroalgae, there are still many challenges associated with biofuel production from macroalgae. These involve key processes such as feedstock mass production, suitable pretreatment, and process integration to minimize energy demands [10]. Pyrolysis has received special attention because it can convert biomass directly into energy products that could be used
* Corresponding author. Fax: +82 33 570 6535. ** Corresponding author. Fax: +82 51 629 6929. E-mail addresses: [email protected] (S.-S. Kim), [email protected] (H.C. Woo).
successfully for the production of heat, power, and chemicals [11]. Fast pyrolysis in the absence of oxygen, can produce a liquid product known as bio-oil, a solid residue (bio-char), and several light gaseous compounds (e.g., carbon dioxide, carbon monoxide, hydrogen, and light hydrocarbons) [12]. Crude bio-oil is generally a complex dark brown mixture, and mainly includes water and hundreds of oxygenated organic compounds such as aldehydes, alcohols, carboxylic acids, esters, ethers, furans, ketones, phenols, and anhydrosugars [13]. The crude bio-oil is hard to use directly as a fuel because of its low heating value, high viscosity, high water and oxygen content, and instability due to the presence of unsaturated and phenolic moieties [14]. These qualities must be taken into careful consideration when it is to be used as a fuel for generating heat and electricity [15]. The current techniques have reported in the literature for upgrading bio-oil involved in distillation, solvent extraction, emulsification, supercritical fluid, hydro treatment, hydrocracking, and steam reforming [11]. In addition to these approaches to bio-oil upgrading and separation technology (bio-oil distillation) can also provide a source of valuable chemicals and useful fuels [15,16]. The most extensively used separation technique in petrochemical refinery is conventional atmospheric distillation. This technique can also be the most economically feasible pathway to separate the complex bio-oil mixture into chemical fractions and upgrade the fuel sources via biorefinery development. However, the high temperatures needed for atmospheric distillation can cause formation of unexpected products from bio-oil. Hence, tremendous efforts have been made to mitigate the aforementioned problems [17]. Distillation under
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mixture could provide information useful for setting the quality standards of bio-oil based fuels.
Nomenclature
American Society for Testing and Materials Dark hydrophobic oil Elemental analyzer Fourier transform infrared Gas chromatography–mass spectrometry Higher heating value Korea Petroleum Quality and Distribution Authority NMR Nuclear magnetic resonance OFDB Organic fraction of distilled bio-oil PAHs Polycyclic aromatic hydrocarbons S. japonica Saccharina japonica TG Thermogravimetric THO Transparent hydrophilic oil ASTM DHO EA FT-IR GC–MS HHV KPetro
reduced pressure requires a lower distillation temperature, and can be used to reduce the occurrence of distillation residue and aging reaction [17,18]. Recently, Nam et al. [19] reported that microalgae pyrolytic bio-oil was separated into three fractions compared with atmospheric and vacuum distillation. The light and middle fractions showed 40–41 MJ/kg as high potential for transportation fuels. However, the distillation characteristics of macroalgae pyrolytic bio-oil have still been investigated as limited studies. In this study, crude bio-oil derived from the brown alga Saccharina japonica was separated into three distillates under reduced pressure (40 mmHg) within the temperature range 25– 160 C. The objectives of this study were to qualitatively identify and quantify the components in distillate fractions, and to obtain stable chemical fractions for use in alternative fuel and chemicals. The blend-testing of the bio-oil distillate with petroleum-based heavy oil is the first trial in this work. The fuel properties of the
Experimental Bio-oil distillation The brown alga S. japonica (the feedstock) was supplied from Wando Island, Republic of Korea. The crude bio-oil used in this study was produced by fast pyrolysis in a fixed-bed reactor at 450 C. A detailed description of the reactor system and experimental procedure has been described [20]. As shown in Fig. 1, the distillation system consisted of a round bottom flask, a jacketed distillation column with 10-theoretical plates (Catalog #6566-05, ACE Glass Inc.), and a receiver connected to the vacuum pump (N840 Diaphragm Pump, KNF, Germany). The temperature was monitored by inserting a thermocouple in the distillation tip and a round bottom flask through the other neck. In a typical distillation run, 1.2 kg of crude bio-oil was put in a round bottom flask. Distillation fractions were collected at various range of vapor temperature monitored from distillation tip. The yield of each fraction was calculated from initial weight of crude bio-oil. Choi et al. in our previous study reported that the moisture content of crude bio-oil derived from raw S. japonica was in range of 55.13– 72.35 wt% in fixed-bed [20], microtubing [21], and fluidized-bed reactor [22]. The high amount of water contained in crude bio-oil need to be vaporized at low temperature (<40 C) under 40 mmHg because it is thermally unstable. The distillation of bio-oil at a constant 40 mmHg was carried out according to ASTM D2892, and replicated three times to confirm the reproducibility. The standard deviation of each run reported in experimental results. All of the organic fractions of the bio-oil distillates obtained between 40 and 160 C at 40 mmHg were blended with No. 6 fuel oil which was supplied from Korea Petroleum Quality and Distribution Authority (KPetro). A total of 500 mL of blends containing 5 and 10 vol% of the organic fraction were prepared. For characterization of fuel properties, those of blends to
Fig. 1. Schematic diagram of a reduced pressure distillation apparatus.
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homogenization were stirred at 40 5 C for 24 h in 1000 mL sealed round-bottom flask. Analysis methods The moisture content of the bio-oil distillate samples was determined by Karl–Fischer (CA-200, Mitsubishi) titration according to the ASTM E203 method. Elemental compositions (C, H, O, N, and S) of the bio-oil distillates were determined with the following elemental analyzers: the content of carbon, hydrogen, and nitrogen (FLASH 2000, Thermo Scientific, ASTM D5291), the sulfur content (NSX–2100 V, Mitsubishi Chemical Analytech, ASTM D4294), and the oxygen content (FLASH 1112 series, Thermo Finnigan, ASTM D5622). The average value of three replicate measurements of the samples was reported according to ASTM test methods in KPetro. The organic components of the bio-oil distillates were qualitatively identified with gas chromatography–mass spectrometry (GC–MS 7890A, Agilent Technologies, HP–5 ms capillary column, 60 m 0.25 mm 0.25 mm). The GC oven temperature was held at 40 C for 5 min, and was programmed to ramp at 5 C/ min to 300 C. Then, the oven temperature was kept at 300 C for 10 min. The injector temperature was 280 C, and an injection volume of 1 mL was adopted, with the split ratio set as 50:1. The mass spectrometer was operated in full scan mode, and its mass range was 30–300 atomic mass units. The identification of the chromatographic peaks was based on an automatic library search (NIST library version 2.0). The functional groups of the bio-oil distillate samples were measured by Fourier Transform Infrared Spectroscopy (Nicolet iS50R, Thermo Scientific) with the attenuated total reflectance (ATR) method. The 1H and 13C Fourier Transform Nuclear Magnetic Resonance Spectrometer (FT-NMR) spectra were determined using a JEOL JMS ECP-400 spectrometer at 400 MHz in deuterated solvents (i.e., CCl3D-d for a hydrophobic oil and DMSO-d6 for a hydrophilic oil). The proximate analysis of the solid residue from distillation determined the moisture and ash contents according to the ASTM E1755 and E1756, respectively. Volatile matter was determined using a non-isothermal thermogravimetric (TG) method that followed the ASTM E872 method. Fixed carbon was a calculated value of the difference between 100 and the sum of the moisture, ash, and volatile matter, where all values were on the same moisture reference base. The elemental composition (C, H, N, and S) of the solid residue was determined using an elemental analyzer (Vario macro/micro, Elementar, ASTM D5373). The metal compositions (Ca, K, Mg, Na, and P) of the solid residue were analyzed using an ICP–OES (Optima 5300DV, Perkin Elmer). The average value of three replicate measurements of the sample was reported. The higher heating value (HHV) of the solid residue was then estimated by the correlation of Channiwala and Parikh [23].
3
The fuel properties of the bio-oil distillate and blends were determined as follows: HHV (6400EF, Paar, ASTM D240), moisture content (CA-200, Mitsubishi, ASTM E203), kinematic viscosity (CAV-2100, Cannon Instrument Company, ASTM D445), density (DMA 4500, Anton Paar, ASTM D4052), ash content (Muffle furnace, Fisher Scientific, ASTM D482), pH (SevenCompact S220, Mettler Toledo, ASTM E 70), flash point (ATM-7, Tanaka, ASTM D93), pour point (MPC-602, Tanaka, ASTM D97), and water and sediment (Rotanta460R, Hettich, ASTM D2709). The experiments were replicated three times to confirm the repeatability and the reproducibility of the reported results according to ASTM test methods in KPetro. Results and discussion Bio-oil distillation yields As shown in Table 1, the three distilled fractions and residue from the crude bio-oil were obtained at temperature 25–160 C at 40 mmHg: Fraction I (first distillate, b.p. 40 C), Fraction II (second distillate, 40 C < b.p. 120 C), Fraction III (third distillate, 120 C < b.p. 160 C), and the residue (solid residue, b.p. > 160 C). The second and third distillates obtained at 40–160 C and 40 mmHg, separated into two phases (a dark hydrophobic oil (DHO) top layer, and a transparent hydrophilic oil (THO) bottom layer). This phenomenon is due to high moisture content as well as to different polarities of sugars, aliphatics, and aromatics in bio-oil [24]. A small weight loss could be obtained by fast evacuation of vapor during reduced pressure condition [25]. The yield of Fraction I (water-rich fraction) was 58.05 wt%, and had a moisture content of 89.61 wt%. The considerable amount of moisture in Fraction I was evaporated at saturated water vapor pressure (34.1 C and 40 mmHg), and originated from dehydration reactions during biomass pyrolysis, as well as from moisture within the biomass itself [18,25]. The yields of Fractions II and III THOs were 7.06 and 11.67 wt%, respectively (and their moisture contents were 51.40 and 10.28 wt%, respectively). The moisture content in Fractions II and III gradually decreased. However, at higher temperature, most of the remaining water was caused by dehydration reactions in unstable compounds in Fractions II and III [18]. The yields of the Fractions II and III DHOs were 1.43 and 4.88 wt%, respectively, and their moisture contents were 5.86 and 1.30 wt%. The H/C ratios of Fractions II and III were in the range 1.54–1.69, which were closer to the values for cyclics and aromatics than to those of alkanes [26]. The O/C ratios of the bottom layer oils were 0.53–1.16, and those values were larger than the top layer oils (0.11–0.16). Choi et al. [27] reported that the higher O/C ratio was affected by large amounts of moisture and oxygenated compounds. The solid residue (15.4 wt%) was obtained, and was a sticky, high-molecular-weight material. It is considered that the lower H/C ratio of the residue is due to a high
Table 1 Results of reduced pressure distillation of S. japonica bio-oil. Distillation temperature ( C)
Yield (wt%, wet basis)
Moisture content (wt%)
Ultimate analysis (wt%, wet basis) C
Fraction I Fraction II Top layer (DHO) Bottom layer (THO) Fraction III Top layer (DHO) Bottom layer (THO) Solid residue Loss a
<40 40–120
120–160
>160
58.05 2.02 8.49 0.71 1.43 0.47 7.06 0.24 16.55 0.67 4.88 0.34 11.67 1.01 15.35 0.46 1.56 0.17
H
O
H/Ca
O/Ca
89.61 2.40
1.36
10.06
85.63
0.28
3.34
5.86 0.62 51.40 1.91
66.82 16.94
9.29 8.07
19.60 71.87
1.54 1.63
0.16 1.16
1.30 0.21 10.28 1.12
73.48 47.24 68.63
10.59 7.80 5.54
12.31 42.39 20.50
1.69 1.68 0.96
0.11 0.53 0.22
Appearance
Bright yellow Phase separation Dark brown Yellow orange Phase separation Dark brown Yellow green Black
Determined by molar ratio on dry basis.
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degree of unsaturated structures formed by condensation polymerization [18]. The chemical properties of the solid residue were characterized by proximate and ultimate analysis (Table 2). The abundant carbon (68.6 wt%) and hydrogen (5.5 wt%) are the principal combustible elements in the solid residue. The high concentration of volatile matter can be easy to ignite, whereas the highly fixed carbon content tends to burn for a long time with a smoky flame [28]. The trace ash of burned solid residue is attributed to inherent mineral components of the brown algal biomass. GC–MS analysis The GC–MS total ion chromatograms of bio-oil distillates obtained at each temperature range were compared in Fig. 2. All of the bio-oil distillates were analyzed without dilution of the samples for comparing each peak area. The main peaks of Fractions I and III-THO indicated furan derivatives [e.g., 1-(2-furanyl)ethanone, dihydro-2(3H)-furanone] and dianhydrohexitols (e.g., dianhydromannitol, isosorbide as oxygenated compounds), respectively (Supplementary Tables S1 and S3). It is worth mentioning that their distillates have the potential to be further separated into pure bio-chemicals using their different boiling points (i.e., via distillation) [16,29,30]. The chromatograms of Fractions II and III DHOs showed unseparated peak resolution with a rising baseline during the GC–MS analysis (Fig. 2). This phenomenon implies that the low-polarity column (HP–5 ms) may have great difficulty separating the non-polar compounds in these fractions. The main components of the bio-oil distillates identified in the GC–MS are exhibited in Fig. 3. The major components were qualitatively identified with accuracy above 85% by comparing them with the NIST Spectral Mass Library. The components detected in each of the bio-oil distillates were classified into acids, aliphatic ketones, furans, cyclics, heterocyclics, other aliphatics, aromatics, phenolics, polycyclic aromatic hydrocarbons (PAHs), sugars, and esters (Fig. 3 and Supplementary Tables S1–S5). This list of components was then compared with one from crude bio-oil derived from S. japonica as reported by Kim et al. [31]. The acids (e.g., carboxylic acid of C2–C4 and C14–C16) and aliphatic ketones (e.g., 2-propanone and 1-hydroxy-2-propanone) were mainly distributed in all of the fractions (Supplementary Tables S1–S5). The water is not completely removed from the bio-oil fractions because of H-bonding interactions between the acids and ketones [13,32]. The furan derivatives (e.g., 1-(2-furanyl)-ethanone, dihydro-2(3H)-furanone); cyclic components (e.g., cyclopentenones and cyclohexenone of methyl, ethyl, and hydrooxy groups); and heterocyclic components (e.g., pyridine, pyrazines, and pyrroles of methyl and ethyl groups) as biofuel sources were mainly found to be distributed in Fractions I and II (Supplementary Tables S1–S3). Also, the aliphatic compounds (e.g., n-alkane and alkene series of C15–C20); benzenes (e.g., benzenes of methyl and ethyl groups); phenolics (e.g. phenols of methyl and ethyl groups); and PAHs (e.g.
1H-indenes and naphthalenes of methyl and ethyl groups) as sources for biofuels, were mainly distributed in the Fractions II and III DHOs (Supplementary Tables S3 and S5). The sugar diols (e.g., dianhydrohexitols of dianhydromannitol and isosorbide) were mainly distributed in the Fraction III THO (Supplementary Table S4). The sugar diols could be used to synthesize or modify polycondensates like polycarbonates or epoxy resins [33]. Compared to normal aliphatic diols, their attractive feature as monomers is linked to their rigidity, chirality, non-toxicity, and thermomechanical stability [34]. The sugar diols derived from renewable resources could have the potential to reduce petroleum-based polymers in the field of polymeric materials. The esters (e.g., C14–C18 methyl esters of fatty acids) were mainly distributed in the Fraction III DHO (Supplementary Table S5). The long chain fatty acids (C14–C18) from the esters are derived from lipids [26]. The carboxylic acid derivatives could be attributed to esterification or aldol condensations with carboxylic acids, alcohols, and aldehydes during distillation. FT-IR analysis The FT-IR spectra of the bio-oil distillates are shown in Fig. 4. The broad bands of O-H stretching vibrations between 3600 and 3200 cm1 indicate the presence of water, carboxylic acids, alcohols, and phenols in the Fractions I, II- and III-THOs (Supplementary Tables S1, S2, and S4). The aliphatic C-H vibrations at 3000–2850 cm1 (stretching) and at 1375 cm1 (bending) showed the presence of alkanes associated with CH2- and CH3. The bands at 1600 and 1470 cm1 appeared to be characteristic of the C¼C vibration of aromatic compounds that come mainly from the Fractions II and III DHOs (Supplementary Tables S3 and S5) [35]. The strong bands between 1640 and 1720 cm1 were assigned to C¼O functional groups, possibly from carboxylic acids, esters, ketones, and aldehydes, in all of the fractions (Supplementary Tables S1–S5). The bands between 1150 and 1000 cm1 were assigned to C-O-C groups from ether linkages specifically present in carbohydrate derivatives from the Fraction III THO (Supplementary Table S4) [36]. NMR analysis The 1H NMR spectra with main signal characteristics of functional groups such as aliphatics, aromatics, and carbohydrates in each bio-oil distillates are exhibited in Fig. 5. In the 1H NMR spectra, it was possible to identify four main regions. The first region from 0.5 to 3.0 ppm represents protons on aliphatic carbon atoms related to heteroatoms or unsaturated groups [37,38]. These were mainly exhibited in the Fractions II and III DHOs (Supplementary Tables S3 and S5). The second proton region between 3.0 and 4.5 ppm was assigned to hydroxyl and methoxy groups on anhydrosugars or alcohols [37,39], and was attributed to carbohydrate derivatives (e.g., dianhydrohexitols) mainly in the Fraction III THO (Supplementary Table S4). The third region peak between 4.5
Table 2 Proximate and ultimate analysis, heating value, and metal content of solid residue. Proximate analysis (wt%)
Solid residue a b c d e
Ultimate analysis (wt%, dry basis)
Moisturea
Volatile matterb
Fixed carbonc
Ashd
C
H
N
S
O
0.01 0.01
50.78
49.12
0.10 0.02
68.63
5.54
4.72
0.62
20.50
HHVe (MJ/kg)
28.35
Metal content (ppm) Ca
K
Mg
Na
P
24
265
20
47
370
Determined according to the ASTM E1756 standard method. Determined by thermogravimetric analysis. By difference. Determined according to the ASTM E1755 standard method. The higher heating value (HHV) was estimated by the correlation of Channiwala and Parikh [23].
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Fig. 2. Total ion chromatograms of (a) Fraction I, (b) Fraction II-THO, (c) Fraction II-DHO, (d) Fraction III-THO, and (e) Fraction III-DHO.
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Fig. 3. Component distributions of bio-oil distillates identified by GC–MS with accuracy above 85%.
ketones, and carboxylic acids in all of the fractions (Supplementary Tables S1–S5) [37,38]. Overall, the NMR and FT-IR analyses showed that the characteristics of aliphatic, aromatic, and carbohydrate derivative groups were the most prevalent for each of the bio-oil distillates derived from brown algae. Mullen et al. [38] reported that aliphatic protons are most prevalent for wood-based bio-oil, while protons proximal to heteroatoms (alcohols, carbohydrates) are highly concentrated in grass-based bio-oil. Fuel properties
Fig. 4. FT-IR spectra of (a) Fraction I, (b) Fraction II-THO, (c) Fraction II-DHO, (d) Fraction III-THO, and (e) Fraction III-DHO.
and 6.0 ppm represents hydrogen bonding in phenolic OH and non-conjugated olefin groups [37,39], and stem from phenols and olefins in the Fractions II and III DHOs (Supplementary Tables S3 and S5). The fourth one between 6.0 and 8.5 ppm represents the hydrogen atoms in benzenoids and heteroaromatics containing O and N [37,38], and originate from heteroaromatics in the Fractions II and III DHOs (Supplementary Tables S3 and S5). As shown in Fig. 6, the 13C NMR spectra of each of the bio-oil distillates also indicated four main functional groups. From 10 to 50 ppm, the aliphatic carbons from CH3 and CH2 were present in all of the fractions (Supplementary Tables S1–S5). The region between 60 and 90 ppm was assigned to aliphatic carbons bound to oxygen [37,40], which was attributed to the carbohydrate derivatives obtained mainly from Fraction III THO (Supplementary Table S4). The signals from 100 to 160 ppm were attributed to aromatic rings or double bonded carbons in the Fraction II DHO (Supplementary Table S3) [35]. From 160 to 180 ppm, the signals were assigned to carbon from carbonyl groups as aldehydes,
Biomass-derived bio-oils have characteristics very different from petroleum-based fuels, as regards both physical properties and chemical composition. Crude bio-oil is typically composed of multicomponent mixtures of oxygenated hydrocarbons with an appreciable proportion of water obtained from both the original moisture and reaction product. Moreover, it has been reported that the bio-oils from macroalgae have higher water content (26.6– 70.7 wt%) than those from lignocellulosic biomass [24,41,42]. Chiaramonti et al. [43] reported that water content >30 wt% in biooil could be separated into two immiscible phases. Hence, the unusual properties of these bio-oils should be taken into careful consideration, if they are to be used for the generation of heat and power by combustion in boilers, burners, gas turbines, and diesel engines. In this study, an organic fraction (i.e., a mixture of Fractions II and III DHOs) from crude bio-oil of S. japonica was prepared by distillation at 40–160 C at 40 mmHg. The fuel properties of the organic fraction of distilled bio-oil (OFDB) for use as alternative liquid fuels are summarized in Table 3. The OFDB exhibited excellent fuel properties compared to crude bio-oil from S. japonica [31]. Especially, it meets all of the specifications of No. 4 fuel oil (ASTM D396) for use in commercial and/or industrial burners [HHV (33.5 MJ/kg), moisture (0.84 wt%), kinematic viscosity (16.54 at 50 C), density (1.03 kg/m3 at 20 C), ash (0.00 wt%), pH (4.9), flash point (71 C), and pour point (25 C), and water and sediment (< 0.1)]. However, the sulfur content (0.2 wt%) of the OFDB does not meet the specification (<0.05 wt%) of ASTM D7544. The OFDB could be blended with fuel oils to meet the desired specification in commercial or industrial burners [44]. The HHV of the OFDB was significantly higher (by four times) than crude bio-
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Fig. 5. 1H NMR spectra of (a) Fraction I, (b) Fraction II-THO, (c) Fraction II-DHO, (d) Fraction III-THO, and (e) Fraction III-DHO.
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Fig. 6.
13
C NMR spectra of (a) Fraction I, (b) Fraction II-THO, (c) Fraction II-DHO, (d) Fraction III-THO, and (e) Fraction III-DHO.
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Table 3 Fuel properties of the organic fraction of distilled bio-oil (OFDB) in comparison with crude bio-oil, pyrolysis liquid biofuel, and Nos. 4 and 6 fuel oils.a Properties
Methods
OFDBb
Crude biooilc
Pyrolysis liquid biofuel (ASTM D7544)
No. 4 fuel oil (ASTM D396) No. 6 fuel oild (Bunker C oil)
HHV (MJ/kg) Moisture content (wt%) Kinematic viscosity (mm2/ s) Density (kg/dm3)
ASTM D240 ASTM E203 ASTM D445
33.5 0.84 16.54 at 50 C 1.03 at 20 C
8.7 70.7 n/a
>15 <30 <125 at 40 C
n/a n/a <24 at 40 C
40 0.1 351 at 50 C
n/a
1.1–1.3 at 20 C
>0.87 at 15 C
0.94–0.96 at 15 C
0.00 4.9 71.0 25 <0.1
n/a 6.9 n/a n/a n/a
<0.15 Report >45 <9 n/a
<0.10 Report >55 <6 <0.5
0.03 n/a 100 21 <1.0
71.6
16.2
n/a
n/a
85.6
9.0
10.2
n/a
n/a
10.3
2.5
<0.3
n/a
n/a
0.6
0.2
<0.3
<0.05
n/a
2.5
15.9
63.9
n/a
n/a
0.6
132 15 24 0 37
n/a n/a n/a n/a n/a
n/a n/a n/a n/a n/a
n/a n/a n/a n/a n/a
ASTM D4052 ASTM D482 Ash content (wt%) pH ASTM E70 Flash point ( C) ASTM D93 Pour point ( C) ASTM D97 Water and sediment (vol%) ASTM D2709 Elemental composition (wt%) Carbon ASTM D5291 ASTM Hydrogen D5291 ASTM Nitrogen D5291 ASTM Sulfur D4294 ASTM Oxygen D5622 Metal content (ppm) Ca K Mg Na P a b c d
The experiments were replicated three times to confirm the repeatability and reproducibility of the reported results according to ASTM test methods in KPetro. All of the organic fraction of Fractions II and III as OFDB was obtained by distillation between 40 and 160 C at 40 mmHg. Choi et al. [26]. Chiaramonti et al. [43].
oil (8.7 MJ/kg) [31], and the value was slightly lower than No. 6 fuel oil (Bunker C oil) [43]. This observation indicates that the presence of water has both negative and positive effects on the fuel properties. Czernik and Bridgwater [15] reported that the addition of water to bio-oil reduced the heating value and viscosity, whereas it was beneficial for pumping and atomization during combustion. The No. 6 fuel oil can be economically mixed with the OFDB to improve its fuel properties expect for the HHV. However, to blend with diesel or No. 4 fuel oil, the catalytic upgrading with increasing process cost is required to improve the properties of the OFDB. The kinematic viscosity of OFDB was twenty-one times lower than that of the No. 6 fuel oil. In general, lower viscosity makes it easier to pump and lubricate, whereas higher viscosity fuels cause incomplete combustion by increasing the spray droplets [41]. The ash content was not detected in the OFDB. This means that ash
existing in biomass was bound to the bio-char during pyrolysis. The pH value (pH 4.9) of the OFDB was lower than those of crude bio-oil (pH 6.9) [26] and organic phase (pH 5.96) from crude bio-oil [37]. The acidic pH of the OFDB is affected by carboxylic acids included in the Fractions II and III DHOs (Fig. 3, Supplementary Tables 3S and 5S). The flash and pour point could be determined depending on the chemical composition of the bio-oil. The flash point (71 C) of the OFDB was lower than that of No. 6 fuel oil (100 C) [43], and higher than those of light fuel oil (60 C) [43] and mineral oil (>65 C) [44,45]. A flash point above 45 C (as an indicator of safety for storage and transportation) is recommended based on the ASTM D7544 standard for burner fuels [45,46]. The pour point (25 C) of the OFDB was significantly lower than that of No. 6 fuel oil (21 C) [43], and similar to those of light fuel oil (15 C) [43] and mineral oil (5 to 15 C) [44,45]. The pour point is an indication of the lowest temperature at which a fuel could be
Table 4 Fuel properties of No. 6 fuel oil, OFDB, and No. 6 fuel oil/OFDB blends.a Properties
Methods
Fuel specification of Bunker C fuel oilb
No. 6 fuel oilc (Bunker C fuel oil)
Flash point ( C) Kinematic viscosity at 50 C (mm2/s) Water and sediment (vol%) Sulfur (wt%)
ASTM ASTM ASTM ASTM
>70 <540 <1.0 <4.0
85.5 283.5 0.125 3.301
a b c d
D93 D445 D2709 D4294
No. 6 fuel oil/OFDB blends 95/5
90/10
83.5 241.3 <0.1 3.113
81.5 182.9 <0.1 2.931
OFDBd
71.0 16.5 <0.1 2.203
The experiments were replicated three times to confirm the repeatability and reproducibility of the reported results according to ASTM test methods in KPetro. Fuel specification for Bunker C fuel oil according to Petroleum and Petroleum Substitute Fuel Business Act in Republic of Korea. No. 6 fuel oil was supplied by KPetro. All of the organic fraction of Fractions II and III as OFDB was obtained by distillation between 40 and 160 C at 40 mmHg.
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pumped. Rick and Vix [47] reported that the recommended upper limit for pumpability is about 600 mm2/s. As discussed in Table 3, the OFDB could potentially substitute for fuel oils. Its mixture with petroleum based heavy oil as a method to lower cost, could be expected to result in fuel properties similar to commercial fuels. Such mixes could be used as fuels in burners or combustion engines for heat and power generation. Table 4 shows the fuel properties when a 5 and 10 vol% of OFDB was mixed with No. 6 fuel oil (Bunker C fuel oil). The ignition delay (flash point) and kinematic viscosity of No. 6 fuel oil were decreased by blending with the OFDB. The sulfur content of the OFDB blends was lower than that of the No. 6 fuel oil as well. The water and sediment values of the OFDB blends was less than 0.1 vol %. The addition of up to 10% OFDB in No. 6 fuel oil could improve combustion stability and reduce sulfur emission in combustion systems. However, a blend with >10% OFDB with No. 6 fuel oil, could present the problem of immiscibility due to the high oxygen content (15.9 wt%) of the OFDB (Table 3). Further research is required to improve the physical upgrading process or to develop fuel optimization techniques such as emulsification and additive blending [48]. Conclusions The bio-oil distillates from brown alga S. japonica for potential alternative petroleum-based fuels and chemicals were systematically characterized. The three distilled fractions from crude bio-oil were obtained at temperatures in the range 25–160 C at 40 mmHg. The H/C ratio of Fractions II and III was in the range 1.54–1.69, which was closer to the value for aromatics than for alkanes. The main components of the bio-oil distillates were acids, aliphatic ketones, furans, cyclics, heterocyclics, other aliphatics, aromatics, phenolics, polycyclic aromatic hydrocarbons (PAHs), sugars, and esters. The 1-(2-furanyl)-ethanone, dianhydromannitol, and isosorbide for bio-chemical intermediates were present in transparent hydrophilic oils (bottom layers) of the bio-oil distillates. The fuel properties of the OFDB and its mixture with No. 6 fuel oil were analyzed, and included such as HHV, moisture, kinematic viscosity, density, ash, pH, flash and pour point, and water and sediment. Considering the high water and ash content, high viscosity, and unacceptable flash and pour points of crude S. japonica bio-oil, it could only be used directly, as a substitute for No. 6 fuel oil. Acknowledgement This work was financially supported by the Ministry of Oceans and Fisheries of Korea (Project No. 20140559). Appendix A. Supplementary data Supplementary data associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/j.jiec.2017.03.002.
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Please cite this article in press as: J.H. Choi, et al., Characteristics of vacuum fractional distillation from pyrolytic macroalgae (Saccharina japonica) bio-oil, J. Ind. Eng. Chem. (2017), http://dx.doi.org/10.1016/j.jiec.2017.03.002