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Characterization of slow pyrolysis oil obtained from linseed (Linum usitatissimum L.)
J. Anal. Appl. Pyrolysis 85 (2009) 151–154
Contents lists available at ScienceDirect
Journal of Analytical and Applied Pyrolysis journal homepage: www.elsevier.com/locate/jaap
Characterization of slow pyrolysis oil obtained from linseed (Linum usitatissimum L.) C. Acikgoz a,*, O.M. Kockar b a b
Department of Chemical Technology, Bilecik Higher Vocational School, Bilecik University, 11030 Bilecik, Turkey Department of Chemical Engineering, Faculty of Engineering and Architecture, I˙ki Eylu¨l Campus, Anadolu University, 26470 Eskis¸ehir, Turkey
A R T I C L E I N F O
A B S T R A C T
Article history: Received 12 June 2008 Accepted 23 August 2008 Available online 10 September 2008
This study presents the characterization of pyrolysis oil obtained from linseed (Linum usitatissimum L.) produced by slow pyrolysis in the maximum yield. The pyrolysis oil was analyzed to determine its elemental composition and calorific value. The chemical composition of the pyrolysis oil and fractions were investigated using chromatographic and spectroscopic techniques (1H NMR, IR, and GC). The chemical class composition of the oil was determined by liquid column chromatographic fractionation. The oil was separated into pentane soluble and insoluble fractions by using pentane. The column was eluted successively with n-pentane, toluene and methanol to yield aliphatic, aromatic and polar fractions, respectively. The results of the adsorption chromatography of the oil showed that the pyrolysis oil consists of 88 wt% n-pentane soluble. The aliphatic, aromatic and polar fractions of oils obtained in slow pyrolysis are 30, 34, 36 wt%, respectively. The aliphatic and aromatic subtraction make up 64 wt% in slow pyrolysis oil. This seems to be more appropriate for the production of hydrocarbons and chemicals. ß 2008 Elsevier B.V. All rights reserved.
Keywords: Linseed Slow pyrolysis Bio-oil Biomass Characterization Renewable energy
1. Introduction The depletion of world petroleum reserves and increased environmental concerns has stimulated recent interest in alternative sources for petroleum-based fuels. The risk of climate change due to emission of CO2 from fossil fuel conversion to heat or work is considered to be the main environmental problem. Biomass is of growing importance in satisfying environmental concerns over fossil fuel. Biomass is largely composed of carbohydrate and lignin, produced from CO2 and water by photosynthesis, thereby capturing solar energy in living plants. This energy in biomass can be harvested and stored for subsequent release. Biomass production systems are frequently focused on the production of food, animal feed or fiber, although in some cases there is an energy by-product. All biomass residues can produce bioenergy, and organic wastes can still produce energy after they have served another purpose. Biofuel is a term used to describe biomass processed into a more convenient form for use as a fuel. It commonly applies to liquid transport fuels, but could also include gas and solid fuels. While many types of biomass can be converted directly into heat or power, some types of biomass are more suited to conversion or refinement into an intermediate biofuel.
* Corresponding author. Tel.: +90 2282160063. E-mail address: [email protected] (C. Acikgoz). 0165-2370/$ – see front matter ß 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.jaap.2008.08.011
The direct combustion of biomass for heat in steam boiler or furnace is considered as inefficient biomass conversion process. Several conversion routes are used to change raw biomass into useful forms of energy and to provide energy services such as heat, power, or transportation. Conversion routes for biomass are generally thermochemical or biochemical, but can also include chemical and physical. In recent years, the pyrolysis of biomass has received considerable attention. Pyrolysis describes the process of anaerobic decomposition of biomass at elevated temperatures to produce solid, liquid or gaseous products. The type and ratio of products (particularly oil:char) depend on the speed and temperature of the process. Fast pyrolysis can yield up to 80% bio-oil whereas slow pyrolysis produce more char. Much of the present interest in pyrolysis is focused on liquid production. Pyrolytic oil (synthetic oil) has a strategic value because, as a liquid, its handling, storage, transportation and utilization are similar to that of petroleumbased oil. It can be considered as a fuel for general thermal applications (steam and electricity production). Indeed, there are a number of biomass sources being considered as potential sources of fuels and chemical feedstock. In addition, the solid char may be useful as a fuel either directly as briquettes, activated carbon or as char–oil or charcoal–water slurries. The gas generated has a high content of hydrocarbons and a sufficiently high calorific value to be used for the total energy requirements of a biomass pyrolysis plant. The bulk densities and calorific values of the liquid and solid
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products are high, resulting in a high energy density compared to the original biomass. Pyrolysis products tend to be biofuels that can be stored or transported for use in subsequent and separate energy production activities. Other compounds/chemicals may also be extracted from pyrolysis oil which can improve process economics [1]. Biomass energy sources are found extensively throughout Turkey. The potential value of renewable biomass energy resource is 135 Mtoe (Million tonnes oil equivalent). Technically, exploitable potential of biomass energy is estimated to be 65 Mtoe. Biomass energy also comprises about 13% of total energy use in Turkey. There are a number of biomass sources being considered as potential sources of fuels and chemical feedstock. Turkey has both natural resources and conditions necessary for agricultural products, e.g. oil seeds (ground nuts, hazelnuts, cotton seeds, sesame, sunflower seeds, linseed seed) [2,3]. This study presents the characterization of pyrolysis oil obtained from linseed (Linum usitatissimum L.) produced by slow pyrolysis in the maximum yield. The chemical composition of the pyrolytic oil was investigated using some chromatographic and spectroscopic techniques which are 1H NMR, Fourier transform infrared (FTIR), GC, elemental analysis, calorific value and column chromatography. 2. Methods 2.1. Materials The linseed seed (L. usitatissimum L.) sample investigated in this study has been supplied from the city of Konya located in central Anatolia. Oil, cellulose and protein contents of raw material were determined according to Turkish Standards TS 769, TS 324 3-5 and TS 324 1-3, respectively [4–9]. Elemental analysis of the raw material and pyrolysis oil was performed on a Carlo Erba model, EA 1108 (Carlo Erba Instruments, Italy) Strumentazione Elemental Analyzer. The HHV values were calculated by Beckman’s formula HHV (MJ/kg) = 0.352C + 0.944H + 0.105(S–O). C, H, S, O represent carbon, hydrogen, sulphur and oxygen content of material, respectively, expressed in % by mass on dry basis [10]. Determination of ash, moisture and volatile matter was performed according to ASTM Standards (D-1102-84 for ash and D-2016-74 for moisture). The properties of raw material, proximate and ultimate analysis results are given in Table 1. 2.2. Pyrolysis The slow pyrolysis experiments performed in the Heinze reactor were carried out in sweeping gas atmosphere. The 316 stainless steel Heinze retort defined previously had a volume of a 250 cm3 (54 mm i.d.) and was externally heated by an electric furnace with the temperature being controlled by a thermocouple inside the bed. The connecting pipe between the reactor and the cooling system was heated to 400 8C to avoid condensation of tar vapor. In each experiment, 10 g of air dried seed, +0.425 to 1.8 mm particle size range, were placed in the reactor and the temperature was raised to 400, 500, 550, 600 or 700 8C and held for either a minimum of 30 min or no further release of gas was observed. The furnace heating rate was fixed 5 8C min 1 with a nitrogen flow rate of 100 cm3 min 1. The flow of gas released was measured using a soap film for the duration of the experiments. The products were condensed and collected by a trap system maintained at 0 8C. The condensate consisted of aqueous and oil layers which were separated and weighed. After the pyrolysis, the solid char was removed and weighed, then the gas yield was calculated by difference. All the yields were expressed on a dry,
Table 1 Main characteristics of the linseed seeds. Characteristics a
Linseed seed
Oil (%) Cellulose (%) Proteina (%)
42.2 14.1 14.4
Proximate analysisb (%) Moisture Volatiles Fixed carbon Ash
6.7 77.0 10.7 5.6
Ultimate analysisa (%) Carbon Hydrogen Nitrogen Oxygenc Emprical formula H/C molar ratio O/C molar ratio Calorific value (MJ/kg)
61.0 8.5 2.3 28.2 CH1.7O0.35N0.03 1.7 0.35 28.05
a b c
Weight percentage on dry ash-free basis. As received. By difference.
ash-free (daf) basis. The maximum liquid product yield of 46.4% was obtained at the pyrolysis temperature of 550 8C, particle range of +0.425 to 1.8 mm with heating rate of 5 8C min 1 and nitrogen flow rate of 100 cm3 min 1 [11–17]. In this study, all the yields are expressed on dry, ash-free (daf) basis and the average yields from at least three experiments are presented within the experimental error of less than 0.5 wt%. 2.3. Characterization Proximate analyses were carried out on the linseed seed sample. The carbon, hydrogen and nitrogen contents of the linseed seed and pyrolysis oil were determined using a Fisions, EA 1108 Elemental Analyzer. The oxygen content of the linseed seed and oil was found by difference. The calorific value of the linseed seed and pyrolysis oil was also determined. Functional group compositional analysis of the oil was carried out using Fourier transform infrared spectrometry (Jasco FT/IR-300 E Model, KBr disc). The 1H NMR of the oil was obtained at an H frequency of 90 MHz using a Jeol EX 90 A instrument. The sample was dissolved in chloroform-d. The chemical class composition of the oil was determined by a liquid column chromatographic technique. The oil was separated into two fractions as n-pentane soluble and insoluble compounds (asphaltenes) by using 50 ml n-pentane. The n-pentane soluble fractions were further separated on activated silica-gel (70– 230 mesh) pre-treated at 105 8C for 2 h prior to introduce in a 20 cm 2.5 cm i.d. column. The column was eluted successively with 150 ml n-pentane, 100 ml toluene and 100 ml methanol to produce aliphatic, aromatic and polar fractions, respectively. Each fraction was dried and weighed and then n-pentane fraction was subjected to GC analyses (HP 6890 GC/MS, 30 m 0.25 mm i.d.; 0.25-mm film thickness, HP-5MS column). The oil analyzed was obtained under the experimental conditions giving the maximum oil yields. 3. Results and discussion 3.1. Elemental composition and fractionation of bio-oil The elemental compositions and the proximate analysis of linseed seed are given in Table 1. Table 2 gives the elemental compositions and the calorific value of oil and the column chromato-
C. Acikgoz, O.M. Kockar / J. Anal. Appl. Pyrolysis 85 (2009) 151–154
153
Table 2 The elemental compositions and calorific value of bio-oil and fractions. Component
Oila (%)
n-Pentane fraction (%)
Toluene fraction (%)
Methanol fraction (%)
C H N Ob H/C Calorific values (MJ/kg)
74.2 10.5 1.5 13.8 1.70 34.58
75.2 12.3 0.05 12.5 1.96 36.77
81.2 12.2 1.2 5.4 1.80 39.53
74.1 10.8 2.3 12.8 1.75 34.93
a b
Obtained at 550 8C, 5 8C min By difference.
1
, with the nitrogen flow rate of 100 cm3 min
1
.
Fig. 2. GC chromatogram of the n-pentane eluate.
Fig. 1. IR spectra of the pyrolysis oil.
graphy fractions obtained from slow pyrolysis oil at sweep gas atmosphere. The average chemical compositions nitrogen atmosphere oil analyzed is CH1.64O0.068N0.013. Furthermore, comparison of the H/C ratios with those of conventional fuels indicates that the oils obtained in this work lie between light and heavy petroleum products in this respect. The calorific values of oil are also very close to those of petroleum fractions. The bio-oil was characterized by lower oxygen content than that of the original feedstock. The decrease in the oxygen content of
the bio-oil (13.8%) compared to the original feedstock (28.2%) is important because the high oxygen is not attractive for the production of transport fuels. The pyrolysis oil comprises 88 wt% npentane soluble, of which aliphatic, aromatic and polar fractions account for 30, 34 and 36 wt%, respectively. Consequently, the aliphatic and aromatic sub-fractions make up 64 wt% and this seems to be more appropriate for the production of hydrocarbons and chemicals. 3.2. Oil functional group composition Fig. 1 shows the FTIR spectra, that the representing functional group compositional analysis of bio-oil were carried out on thin films between KBr plates. The O–H stretching vibrations between
Fig. 3. 1H NMR spectra of the bio-oil.
C. Acikgoz, O.M. Kockar / J. Anal. Appl. Pyrolysis 85 (2009) 151–154
154 Table 3 1 H NMR results of the bio-oil. Hydrogen environment
Oila mol% (% of total hydrogen)
Aromatic/alkene (inc. peak at 5.5 ppm) Aliphatic adjacent to oxygen (3.3–4.5 ppm) Aliphatic adjacent to aromatic/alkene group (1.8–3.3 ppm) Other aliphatic (bonded to aliphatic only, 0.4–1.8 ppm)
7.47 3.93 12.32
a
Obtained at 550 8C, 5 8C min
1
76.28
, with the nitrogen flow rate of 100 cm3 min
1
.
3200 and 3400 cm 1 of the bio-oils indicate the presence of phenols and alcohols; the C–H stretching vibrations between 2843 and 2950 cm 1 and C–H deformation vibrations between 1300 and 1468 cm 1 indicate the presence of alkane groups in pyrolysis oil derived from biomass and its sub-fractions. The C O stretching vibrations between 1600 and 1718 cm 1 is compatible with the presence of ketone, quinone, aldehyde groups, etc. The absorbance peaks between 1547 and 1675 cm 1 represent C C stretching vibrations indicative of alkenes and aromatics. Furthermore, mono- and polycyclic and substituted aromatic groups are indicated by the absorption peaks between 700 and 900 cm 1. A gas chromatogram of the aliphatic fractions is given in Fig. 2. The GC chromatogram of the aliphatic fraction showed that the carbon distribution lay between C8 and C29 and the distribution of straight chain alkanes exhibited a maximum in the range of C8–C17 in the bio-oil. Olefins are present in the pentane sub-fraction of the bio-oil but n-alkanes dominate [18–20]. The 1H NMR spectrum of the oil investigated is shown in Fig. 3 and the hydrogen distribution and estimated carbon aromaticity are listed in Table 3. 4. Conclusion In this study, the bio-oil product was characterized by elemental analysis and various chromatographic and spectroscopic techniques and also compared with currently utilized transport fuels and presented as a biofuel candidate. The bio-oil was a mixture of aliphatic and aromatic hydrocarbons having an empirical formula of CH1.64O0.068N0.013, H/C molar ratio 1.7, O/C molar ratios 0.19 and heating value 34.58 MJ/kg. Comparison of H/C molar ratio with those of conventional fuels indicates that the bio-oil obtained in this work lay between light and heavy petroleum products. FTIR analyses
showed that the bio-oil composition was dominated by oxygenated species. The high oxygen content is reflected by the presence of mostly oxygenated fractions such as carboxyl and carbonyl groups produced by pyrolysis of cellulose and phenolic and methoxy groups produced by pyrolysis of lignin. For the evaluation of the employment of pyrolytic oil as a fuel, the following options are recommended: The liquid product may be used a source of low-grade fuel directly or may be upgraded to higher quality liquid fuels. Oil seems to be more appropriate for the production of hydrocarbons and chemicals. There is a great potential for Turkey to exploit biomass reserves as possible synthetic petroleum sources. The findings of laboratory-scale studies are encouraging and warrant larger-scale applications of biomass pyrolysis for synthetic fuels. References [1] [2] [3] [4]
[5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16]
[17] [18] [19] [20]
IEA Bioenergy website, www.ieabioenergy.com S. Yorgun, S. Sensoz, O.M. Kockar, Biomass & Bioenergy 20 (2001) 141–148. I.T. Engin, Turkiye 7, vol. 1, Enerji Kongresi, Ankara, Turkey, 1997, pp. 317–326. S. Besler, O.M. Kockar, A.E. Putun, E. Ekinci, E. Putun, in: Proceedings of the International Conference on Advances in Thermochemical Biomass Conversion, Switzerland, (1992), pp. 1103–1109. A.E. Putun, H.F. Gercel, O.M. Kockar, E. Ozgul, C.E. Snape, Fuel 75 (11) (1996) 1307– 1312. A.E. Putun, N. Ozbay, O.M. Kockar, E. Putun, Energy Sources (1997) 905–915. S. Sensoz, D. Angın, S. Yorgun, O.M. Kockar, Energy Sources 22 (10) (2000) 891– 901. A.V. Bridgewater, G. Grassi, Biomass pyrolysis liquids upgrading and utilisation, Elsevier Applied Science, England, 1991. A.V. Bridgwater, Journal of Analytical Applied Pyrolysis 51 (1999) 3–22. S.A. Channiwala, P.P. Parikh, Fuel 81 (2002) 1051–1063. C. Acikgoz, O. Onay, S.H. Beis, O.M. Kockar, in: Proceedings of the World Renewable Energy Congress, vol. VII, Cologne, Germany, June 29–July 5, 2002. ¨ . Onay, O ¨ .M. Koc¸kar, Biomass & Bioenergy 26 (2004) 289–299. O ¨ . Onay, O ¨ .M. Koc¸kar, Energy Sources 25 (2003) 1053–1062. S.H. Beis, D. Du¨zenli, O ¨ . Onay, O ¨ .M. Koc¸kar, Energy Sources 25 (2003) 879–892. O ¨ . Onay, O ¨ .M. ve Koc¸kar, Renewable Energy 26 (2001) 21–32. S.H. Beis, O ¨ . Onay, E. Atabay, O ¨ .M. ve Koc¸kar, in: Proceedings of the World S.H. Beis, O Renewable Energy Congress (WREC 2000), vol. VI, Brighton, UK, July 1–7, Renewable Energy II (2000) 1360–1363. ¨ .M. Koc¸kar, O ¨ . Onay, A.E. Pu¨tu¨n, E. Pu¨tu¨n, Energy Sources 22 (10) (2000) 913– O 924. ¨ . Onay, O ¨ .M. Koc¸kar, Journal of Analytical and Applied Pyrolysis 71 C. Ac¸ıkgo¨z, O (2004) 417–429. ¨ . Onay, O ¨ .M. Koc¸kar, Renewable Energy 28 (15) (2003) 2417–2433. O ¨ . Onay, S.H. Beis, O ¨ .M. Koc¸kar, Journal of Analytical and Applied Pyrolysis 58–59 O (2001) 995–1007.
Contents lists available at ScienceDirect
Journal of Analytical and Applied Pyrolysis journal homepage: www.elsevier.com/locate/jaap
Characterization of slow pyrolysis oil obtained from linseed (Linum usitatissimum L.) C. Acikgoz a,*, O.M. Kockar b a b
Department of Chemical Technology, Bilecik Higher Vocational School, Bilecik University, 11030 Bilecik, Turkey Department of Chemical Engineering, Faculty of Engineering and Architecture, I˙ki Eylu¨l Campus, Anadolu University, 26470 Eskis¸ehir, Turkey
A R T I C L E I N F O
A B S T R A C T
Article history: Received 12 June 2008 Accepted 23 August 2008 Available online 10 September 2008
This study presents the characterization of pyrolysis oil obtained from linseed (Linum usitatissimum L.) produced by slow pyrolysis in the maximum yield. The pyrolysis oil was analyzed to determine its elemental composition and calorific value. The chemical composition of the pyrolysis oil and fractions were investigated using chromatographic and spectroscopic techniques (1H NMR, IR, and GC). The chemical class composition of the oil was determined by liquid column chromatographic fractionation. The oil was separated into pentane soluble and insoluble fractions by using pentane. The column was eluted successively with n-pentane, toluene and methanol to yield aliphatic, aromatic and polar fractions, respectively. The results of the adsorption chromatography of the oil showed that the pyrolysis oil consists of 88 wt% n-pentane soluble. The aliphatic, aromatic and polar fractions of oils obtained in slow pyrolysis are 30, 34, 36 wt%, respectively. The aliphatic and aromatic subtraction make up 64 wt% in slow pyrolysis oil. This seems to be more appropriate for the production of hydrocarbons and chemicals. ß 2008 Elsevier B.V. All rights reserved.
Keywords: Linseed Slow pyrolysis Bio-oil Biomass Characterization Renewable energy
1. Introduction The depletion of world petroleum reserves and increased environmental concerns has stimulated recent interest in alternative sources for petroleum-based fuels. The risk of climate change due to emission of CO2 from fossil fuel conversion to heat or work is considered to be the main environmental problem. Biomass is of growing importance in satisfying environmental concerns over fossil fuel. Biomass is largely composed of carbohydrate and lignin, produced from CO2 and water by photosynthesis, thereby capturing solar energy in living plants. This energy in biomass can be harvested and stored for subsequent release. Biomass production systems are frequently focused on the production of food, animal feed or fiber, although in some cases there is an energy by-product. All biomass residues can produce bioenergy, and organic wastes can still produce energy after they have served another purpose. Biofuel is a term used to describe biomass processed into a more convenient form for use as a fuel. It commonly applies to liquid transport fuels, but could also include gas and solid fuels. While many types of biomass can be converted directly into heat or power, some types of biomass are more suited to conversion or refinement into an intermediate biofuel.
* Corresponding author. Tel.: +90 2282160063. E-mail address: [email protected] (C. Acikgoz). 0165-2370/$ – see front matter ß 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.jaap.2008.08.011
The direct combustion of biomass for heat in steam boiler or furnace is considered as inefficient biomass conversion process. Several conversion routes are used to change raw biomass into useful forms of energy and to provide energy services such as heat, power, or transportation. Conversion routes for biomass are generally thermochemical or biochemical, but can also include chemical and physical. In recent years, the pyrolysis of biomass has received considerable attention. Pyrolysis describes the process of anaerobic decomposition of biomass at elevated temperatures to produce solid, liquid or gaseous products. The type and ratio of products (particularly oil:char) depend on the speed and temperature of the process. Fast pyrolysis can yield up to 80% bio-oil whereas slow pyrolysis produce more char. Much of the present interest in pyrolysis is focused on liquid production. Pyrolytic oil (synthetic oil) has a strategic value because, as a liquid, its handling, storage, transportation and utilization are similar to that of petroleumbased oil. It can be considered as a fuel for general thermal applications (steam and electricity production). Indeed, there are a number of biomass sources being considered as potential sources of fuels and chemical feedstock. In addition, the solid char may be useful as a fuel either directly as briquettes, activated carbon or as char–oil or charcoal–water slurries. The gas generated has a high content of hydrocarbons and a sufficiently high calorific value to be used for the total energy requirements of a biomass pyrolysis plant. The bulk densities and calorific values of the liquid and solid
152
C. Acikgoz, O.M. Kockar / J. Anal. Appl. Pyrolysis 85 (2009) 151–154
products are high, resulting in a high energy density compared to the original biomass. Pyrolysis products tend to be biofuels that can be stored or transported for use in subsequent and separate energy production activities. Other compounds/chemicals may also be extracted from pyrolysis oil which can improve process economics [1]. Biomass energy sources are found extensively throughout Turkey. The potential value of renewable biomass energy resource is 135 Mtoe (Million tonnes oil equivalent). Technically, exploitable potential of biomass energy is estimated to be 65 Mtoe. Biomass energy also comprises about 13% of total energy use in Turkey. There are a number of biomass sources being considered as potential sources of fuels and chemical feedstock. Turkey has both natural resources and conditions necessary for agricultural products, e.g. oil seeds (ground nuts, hazelnuts, cotton seeds, sesame, sunflower seeds, linseed seed) [2,3]. This study presents the characterization of pyrolysis oil obtained from linseed (Linum usitatissimum L.) produced by slow pyrolysis in the maximum yield. The chemical composition of the pyrolytic oil was investigated using some chromatographic and spectroscopic techniques which are 1H NMR, Fourier transform infrared (FTIR), GC, elemental analysis, calorific value and column chromatography. 2. Methods 2.1. Materials The linseed seed (L. usitatissimum L.) sample investigated in this study has been supplied from the city of Konya located in central Anatolia. Oil, cellulose and protein contents of raw material were determined according to Turkish Standards TS 769, TS 324 3-5 and TS 324 1-3, respectively [4–9]. Elemental analysis of the raw material and pyrolysis oil was performed on a Carlo Erba model, EA 1108 (Carlo Erba Instruments, Italy) Strumentazione Elemental Analyzer. The HHV values were calculated by Beckman’s formula HHV (MJ/kg) = 0.352C + 0.944H + 0.105(S–O). C, H, S, O represent carbon, hydrogen, sulphur and oxygen content of material, respectively, expressed in % by mass on dry basis [10]. Determination of ash, moisture and volatile matter was performed according to ASTM Standards (D-1102-84 for ash and D-2016-74 for moisture). The properties of raw material, proximate and ultimate analysis results are given in Table 1. 2.2. Pyrolysis The slow pyrolysis experiments performed in the Heinze reactor were carried out in sweeping gas atmosphere. The 316 stainless steel Heinze retort defined previously had a volume of a 250 cm3 (54 mm i.d.) and was externally heated by an electric furnace with the temperature being controlled by a thermocouple inside the bed. The connecting pipe between the reactor and the cooling system was heated to 400 8C to avoid condensation of tar vapor. In each experiment, 10 g of air dried seed, +0.425 to 1.8 mm particle size range, were placed in the reactor and the temperature was raised to 400, 500, 550, 600 or 700 8C and held for either a minimum of 30 min or no further release of gas was observed. The furnace heating rate was fixed 5 8C min 1 with a nitrogen flow rate of 100 cm3 min 1. The flow of gas released was measured using a soap film for the duration of the experiments. The products were condensed and collected by a trap system maintained at 0 8C. The condensate consisted of aqueous and oil layers which were separated and weighed. After the pyrolysis, the solid char was removed and weighed, then the gas yield was calculated by difference. All the yields were expressed on a dry,
Table 1 Main characteristics of the linseed seeds. Characteristics a
Linseed seed
Oil (%) Cellulose (%) Proteina (%)
42.2 14.1 14.4
Proximate analysisb (%) Moisture Volatiles Fixed carbon Ash
6.7 77.0 10.7 5.6
Ultimate analysisa (%) Carbon Hydrogen Nitrogen Oxygenc Emprical formula H/C molar ratio O/C molar ratio Calorific value (MJ/kg)
61.0 8.5 2.3 28.2 CH1.7O0.35N0.03 1.7 0.35 28.05
a b c
Weight percentage on dry ash-free basis. As received. By difference.
ash-free (daf) basis. The maximum liquid product yield of 46.4% was obtained at the pyrolysis temperature of 550 8C, particle range of +0.425 to 1.8 mm with heating rate of 5 8C min 1 and nitrogen flow rate of 100 cm3 min 1 [11–17]. In this study, all the yields are expressed on dry, ash-free (daf) basis and the average yields from at least three experiments are presented within the experimental error of less than 0.5 wt%. 2.3. Characterization Proximate analyses were carried out on the linseed seed sample. The carbon, hydrogen and nitrogen contents of the linseed seed and pyrolysis oil were determined using a Fisions, EA 1108 Elemental Analyzer. The oxygen content of the linseed seed and oil was found by difference. The calorific value of the linseed seed and pyrolysis oil was also determined. Functional group compositional analysis of the oil was carried out using Fourier transform infrared spectrometry (Jasco FT/IR-300 E Model, KBr disc). The 1H NMR of the oil was obtained at an H frequency of 90 MHz using a Jeol EX 90 A instrument. The sample was dissolved in chloroform-d. The chemical class composition of the oil was determined by a liquid column chromatographic technique. The oil was separated into two fractions as n-pentane soluble and insoluble compounds (asphaltenes) by using 50 ml n-pentane. The n-pentane soluble fractions were further separated on activated silica-gel (70– 230 mesh) pre-treated at 105 8C for 2 h prior to introduce in a 20 cm 2.5 cm i.d. column. The column was eluted successively with 150 ml n-pentane, 100 ml toluene and 100 ml methanol to produce aliphatic, aromatic and polar fractions, respectively. Each fraction was dried and weighed and then n-pentane fraction was subjected to GC analyses (HP 6890 GC/MS, 30 m 0.25 mm i.d.; 0.25-mm film thickness, HP-5MS column). The oil analyzed was obtained under the experimental conditions giving the maximum oil yields. 3. Results and discussion 3.1. Elemental composition and fractionation of bio-oil The elemental compositions and the proximate analysis of linseed seed are given in Table 1. Table 2 gives the elemental compositions and the calorific value of oil and the column chromato-
C. Acikgoz, O.M. Kockar / J. Anal. Appl. Pyrolysis 85 (2009) 151–154
153
Table 2 The elemental compositions and calorific value of bio-oil and fractions. Component
Oila (%)
n-Pentane fraction (%)
Toluene fraction (%)
Methanol fraction (%)
C H N Ob H/C Calorific values (MJ/kg)
74.2 10.5 1.5 13.8 1.70 34.58
75.2 12.3 0.05 12.5 1.96 36.77
81.2 12.2 1.2 5.4 1.80 39.53
74.1 10.8 2.3 12.8 1.75 34.93
a b
Obtained at 550 8C, 5 8C min By difference.
1
, with the nitrogen flow rate of 100 cm3 min
1
.
Fig. 2. GC chromatogram of the n-pentane eluate.
Fig. 1. IR spectra of the pyrolysis oil.
graphy fractions obtained from slow pyrolysis oil at sweep gas atmosphere. The average chemical compositions nitrogen atmosphere oil analyzed is CH1.64O0.068N0.013. Furthermore, comparison of the H/C ratios with those of conventional fuels indicates that the oils obtained in this work lie between light and heavy petroleum products in this respect. The calorific values of oil are also very close to those of petroleum fractions. The bio-oil was characterized by lower oxygen content than that of the original feedstock. The decrease in the oxygen content of
the bio-oil (13.8%) compared to the original feedstock (28.2%) is important because the high oxygen is not attractive for the production of transport fuels. The pyrolysis oil comprises 88 wt% npentane soluble, of which aliphatic, aromatic and polar fractions account for 30, 34 and 36 wt%, respectively. Consequently, the aliphatic and aromatic sub-fractions make up 64 wt% and this seems to be more appropriate for the production of hydrocarbons and chemicals. 3.2. Oil functional group composition Fig. 1 shows the FTIR spectra, that the representing functional group compositional analysis of bio-oil were carried out on thin films between KBr plates. The O–H stretching vibrations between
Fig. 3. 1H NMR spectra of the bio-oil.
C. Acikgoz, O.M. Kockar / J. Anal. Appl. Pyrolysis 85 (2009) 151–154
154 Table 3 1 H NMR results of the bio-oil. Hydrogen environment
Oila mol% (% of total hydrogen)
Aromatic/alkene (inc. peak at 5.5 ppm) Aliphatic adjacent to oxygen (3.3–4.5 ppm) Aliphatic adjacent to aromatic/alkene group (1.8–3.3 ppm) Other aliphatic (bonded to aliphatic only, 0.4–1.8 ppm)
7.47 3.93 12.32
a
Obtained at 550 8C, 5 8C min
1
76.28
, with the nitrogen flow rate of 100 cm3 min
1
.
3200 and 3400 cm 1 of the bio-oils indicate the presence of phenols and alcohols; the C–H stretching vibrations between 2843 and 2950 cm 1 and C–H deformation vibrations between 1300 and 1468 cm 1 indicate the presence of alkane groups in pyrolysis oil derived from biomass and its sub-fractions. The C O stretching vibrations between 1600 and 1718 cm 1 is compatible with the presence of ketone, quinone, aldehyde groups, etc. The absorbance peaks between 1547 and 1675 cm 1 represent C C stretching vibrations indicative of alkenes and aromatics. Furthermore, mono- and polycyclic and substituted aromatic groups are indicated by the absorption peaks between 700 and 900 cm 1. A gas chromatogram of the aliphatic fractions is given in Fig. 2. The GC chromatogram of the aliphatic fraction showed that the carbon distribution lay between C8 and C29 and the distribution of straight chain alkanes exhibited a maximum in the range of C8–C17 in the bio-oil. Olefins are present in the pentane sub-fraction of the bio-oil but n-alkanes dominate [18–20]. The 1H NMR spectrum of the oil investigated is shown in Fig. 3 and the hydrogen distribution and estimated carbon aromaticity are listed in Table 3. 4. Conclusion In this study, the bio-oil product was characterized by elemental analysis and various chromatographic and spectroscopic techniques and also compared with currently utilized transport fuels and presented as a biofuel candidate. The bio-oil was a mixture of aliphatic and aromatic hydrocarbons having an empirical formula of CH1.64O0.068N0.013, H/C molar ratio 1.7, O/C molar ratios 0.19 and heating value 34.58 MJ/kg. Comparison of H/C molar ratio with those of conventional fuels indicates that the bio-oil obtained in this work lay between light and heavy petroleum products. FTIR analyses
showed that the bio-oil composition was dominated by oxygenated species. The high oxygen content is reflected by the presence of mostly oxygenated fractions such as carboxyl and carbonyl groups produced by pyrolysis of cellulose and phenolic and methoxy groups produced by pyrolysis of lignin. For the evaluation of the employment of pyrolytic oil as a fuel, the following options are recommended: The liquid product may be used a source of low-grade fuel directly or may be upgraded to higher quality liquid fuels. Oil seems to be more appropriate for the production of hydrocarbons and chemicals. There is a great potential for Turkey to exploit biomass reserves as possible synthetic petroleum sources. The findings of laboratory-scale studies are encouraging and warrant larger-scale applications of biomass pyrolysis for synthetic fuels. References [1] [2] [3] [4]
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