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Characterization of products from the pyrolysis of rapeseed oil cake
Bioresource Technology 99 (2008) 8771–8776
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Characterization of products from the pyrolysis of rapeseed oil cake Suat Ucar a,*, Ahmet R. Ozkan b a b
Chemistry Program, Izmir Vocational School, Dokuz Eylul University, 35160-Buca-Izmir, Turkey Quality Control and Technical Service, Petkim Holding Co., Aliaga, 35800 Izmir, Turkey
a r t i c l e
i n f o
Article history: Received 6 July 2007 Received in revised form 7 April 2008 Accepted 12 April 2008 Available online 3 June 2008 Keywords: Rapeseed oil cake Pyrolysis Bio-oil Oleic acid Phenols
a b s t r a c t The main aim of this study was to investigate the composition of products from the pyrolysis of rapeseed oil cake in a fixed bed reactor at 400, 450, 500, 700 and 900 °C. The gas products mainly consisted of CO2, CO, CH4 and H2S at 500 °C. Empirical formula of bio-oil from the pyrolysis of rapeseed oil cake was CH1.59O0.16N0.116S0.003 for 500 °C. Bio-oils mainly contained oleic acid, 1H-indole, 2,3,5-trimethoxy toluene, toluene, (Z)-9-octadecanamide, psoralene, phenol and phenol derivatives at all pyrolysis temperatures. Both non-aromatic and aromatic hydrocarbon compounds were determined in water phase of liquid product by Headspace-GC analysis. The heating values of bio-chars were found to be similar (24 MJ kg 1) at all pyrolysis temperatures. Ó 2008 Elsevier Ltd. All rights reserved.
1. Introduction Biomass is a renewable energy resource derived from all the organic materials produced by human and natural activities. It is a complex mixture of organic materials such as carbohydrates, fats and proteins. The main components of the plant biomass are carbohydrates and lignin which can vary with biomass type. The carbohydrates are mainly cellulose or hemicellulose fibers which give strength to the plant structure and lignin which holds the fibers together. Some plants also store starch and fats as sources of energy, mainly in seeds and roots. Some of the biomass types are by-products of the agricultural crops, raw material from the forest, municipal solid waste, animal and human waste. In the developed world, biomass has become more important for applications such as combined heat and power generation. Moreover, it is a source of clean energy and can be replaced fossil fuels. There are a number of technological options available to make use of a wide variety of biomass types as a renewable energy source. These technologies can be classified into two main groups; biochemical (Ramachandran et al., 2007; McKendry, 2002) and thermochemical conversion (McKendry, 2002). Biochemical conversion is the use of the enzymes of bacteria and other microorganisms to convert biomass to fuels and chemicals. Biochemical conversion process includes anaerobic digestion, fermentation and mechanical extraction. Thermochemical conversion can be performed using some processes which are gasification, pyrolysis (slow, fast, flash, and vacuum), hydrothermal upgrading (in water * Corresponding author. Tel.: +90 232 420 48 93; fax: +90 232 420 51 81. E-mail address: [email protected] (S. Ucar). 0960-8524/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.biortech.2008.04.040
or solvent) and combustion. Pyrolysis is the technique of applying high heat to organic matter under the inert atmosphere which results in the converting organic materials into usable fuels and chemical feedstock. This process applied to lignocellulosic materials can produce charcoal, condensable organic liquids (pyrolytic bio fuel) and non-condensable gasses. It is the most effective process for biomass conversion. Rapeseed, which contains around 40% rape oil, is one of the most important oil seed for the production of vegetable oil in the world. The total production of rapeseed plant all around the world was 46.2 Mt in 2005 (FAO, 2006). The production of rapeseed oil in the world was 17.9 Mt in 2005 (Oil World Annual, 2006). Rapeseed oil cake, which is the solid residue remaining after extraction of the oil from the rapeseed, is the most commonly preferred in animal feed because it contains 16–24% protein. All parts of the rapeseed (straw, stalk, seed, oil, and cake) are used as a biomass resource for the production of biofuels and bio-diesel. Even though rapeseed is the third most valuable vegetable oils’ source in the world, it is not commonly grown in Turkey. The annual production of rapeseed plant in Turkey was merely 1000 Mt in 2005 (Oil World Annual, 2006). Thus, a large amount of rapeseed is imported. In the future, rapeseed plant could be expected to become one of the major oil seed crops by the Southeastern Anatolia Project (GAP) in the southeast of Turkey. Because of this, the evaluation of rapeseed is important for Turkey not only for the production of vegetable oil but also production of bio-diesel and bio-oil by thermochemical conversion. With its 25 million hectares of arable land, Turkey has a vast agricultural production and crop diversity (FAO, 1993). Hence, it is very important that agricultural residues in Turkey can be utilized as energy sources to cover the energy
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demand of Turkey from renewable sources. Recent studies related to the pyrolysis of agricultural residues showed that Turkey has to adapt new long-term energy strategies to produce domestic energy from biomass sources (Onay and Kockar, 2004; Sensoz and Kaynar, 2006; Putun et al., 2006; Yorgun et al., 2001). There have been number of studies which dealt with the pyrolysis of rapeseed. In these studies, the influence of final pyrolysis temperature, (Karaosmanoglu et al., 1999; Sensoz et al., 2000a; Onay and Kockar, 2003) particle size, (Sensoz et al., 2000b), varying sweep gas velocity, (Sensoz et al., 2001; Ozcimen and Karaosmanoglu, 2004) heating rate (slow, fast, flash pyrolysis) (Onay and Kockar, 2003; Haykiri-Acma et al., 2006) and different reactor types, i.e. fixed bed, tubular, free fall reactor (Sensoz et al., 2000a; Ozcimen and Karaosmanoglu, 2004; Onay and Kockar, 2006) on the pyrolysis product yields and compositions were investigated. In these studies, the bio-oil was characterized by using elemental analysis, various chromatographic and spectroscopic techniques in order to investigate its possibility of being a potential source of renewable fuel and chemical feedstock. In the present investigation, rapeseed oil cake was pyrolyzed at the temperatures of 400, 450, 500, 700 and 900 °C. The main objective of this study is to investigate the effect of pyrolysis temperature on the product distribution and characterization of all pyrolysis products by using different analytical techniques. The gas products were analyzed by gas chromatograph equipped with thermal conductivity detector (GC-TCD). The liquid products were analyzed by means of the gas chromatograph equipped with a mass selective detector analysis (GC–MS), Headspace-GC and an elemental analyzer. The solid products were analyzed by use of an elemental analyzer and a bomb calorimeter. The analysis of rapeseed oil cake was carried out using a Thermogravimetric analyzer and an elemental analyzer.
2.1. Materials Rapeseed (Brassica napus L.) oil cake was supplied by Altinyag Oil Company, Izmir, Turkey and used as received (average particle size 2 mm). The proximate, ultimate and component analyses (Li Table 1 Proximate, ultimate and component analyses of rapeseed oil cake Proximate analysis (as received, wt%) Moisture Volatile matter Fixed carbon Ash
10.59 67.31 15.80 6.30
Ultimate analysis (dry, wt%) C H N S Oa H/C molar ratio O/C molar ratio Empirical formula
45.92 6.21 6.90 0.88 40.09 1.62 0.65 CH1.62O0.65N0.128S0.007
GCVb, MJ kg-11
19.49
Component analysis (dry, wt%) Extractives c Hemicellulose Lignin Cellulose
19.40 41.40 4.99 28.58
a
c
Calculated from difference. Gross calorific value. Toluene/alcohol (2/1) (v/v).
2.2. Pyrolysis procedure Pyrolysis experiments were carried out under nitrogen atmosphere at the temperatures of 400, 450, 500, 700 and 900 °C. Pyrolysis reactor was a fixed bed design and made of stainless steel (316) with 6 cm diameter and 21 cm height and was placed in an electrical furnace. It was heated externally by the electrical furnace. Pyrolysis temperature was measured with an internal NiCr–Ni thermocouple which was placed in the center of pyrolysis reactor. Before the experiments, the reactor was purged by nitrogen gas for 30 min at a flow rate of 30 ml min 1 to remove the air inside. In a typical pyrolysis experiment, a quantity of 116 g of rapeseed oil cake (on a dry base) was loaded and then the reactor temperature was increased with a heating rate of 5 °C min 1 up to the desired pyrolysis temperature and hold for 30 min at the desired temperature. The nitrogen gas swept all volatile products from the reactor into the collection traps. The liquid products were condensed in the first two traps by cooling within ice bath. Non-condensable volatiles were passed through the last two traps containing lead nitrate solution (33 wt%) to absorb the H2S and then the remaining gases were collected in Tedlar plastic bags. 2.3. Analysis procedure Analysis procedure consists of three stages; gas product analyses, liquid product analyses and solid product analyses.
2. Experimental
b
et al., 2004) of rapeseed oil cake are shown in Table 1. Also, oil content of rapeseed oil cake was obtained as 10.3 wt%. The used solvents are diethyl ether, ethyl alcohol, hexane and toluene. The other used chemicals are sodium hydroxide, barium chloride, anhydrous sodium sulfate, lead nitrate and sulfuric acid. All of them were purchased from Aldrich and used as received.
2.3.1. Gas product analyses The gas products collected in Tedlar bag were analyzed by the gas chromatography, HP model 5890 series II with a thermal conductivity detector. A stainless steel packed column (6.0 m 1/ 8 inch Poropack Q, 2.0 m 1/8 inch, MS 5A molecular sieve, serially connected to each other by means of a switching valve) was used. The separation of CO2, C1, C2, C3, C4, C5, C6, and C7 hydrocarbons was done with Poropack Q column and the separation of O2, N2 and CO was carried out with MS 5A column. The amount of hydrogen sulphur in the gas products was determined as lead sulphur precipitate which was formed from the reaction between H2S and lead nitrate solutions in traps. The lead sulphur precipitate was filtered, washed with distillated water, dried at 110 °C and weighted. 2.3.2. Liquid product analyses The liquid product from the pyrolysis of rapeseed oil cake contained the aqueous and organic phase. It was extracted with equal quantity of diethyl ether. The obtained ether fraction (organic phase) was dried over anhydrous sodium sulfate, filtered and evaporated in a rotary evaporator at 25 °C to remove diethyl ether. Then, this fraction was weighted, bottled and denoted as bio-oil. This procedure was carried out according to previous report at which diethyl ether was used as extraction solvent (Karagoz et al., 2005). Since diethyl ether is very good solvent not only extracted all organic matters in liquid products to organic phase but also green and environmentally friendly solvent. After separation of bio-oil and water by extraction, they were analyzed by using following procedures. The gas chromatograph equipped with a mass selective detector analysis of bio-oil was carried out [GC-MSD; HP 6890 System 5973 MSD; column, HP-1; capillary column with dimethylpolysiloxane, 50 m 0.32 mm i.d.,
2.3.3. Analyses of rapeseed oil cake and solid product Thermogravimetric (TG) analysis of rapeseed oil cake was carried out on Shimadzu-TG-50 instrument. The sample of rapeseed oil cake about 20 mg was placed in a standard alumina crucible. The TG experiments were performed under flowing nitrogen atmosphere with a flow rate of 100 ml min 1. The temperature was increased from ambient temperature to 950 °C with a heating rate of 10 °C min 1. Bio-char products were analyzed by an elemental analyzer and a calorimeter bomb as described in bio-oil analyses. The proximate analyses of rapeseed oil cake and bio-char were done according to ASTM D3174-04 for ash analysis and ASTM D3175-89a for volatile matter.
% Weight
0.52 mm film thickness and the oven temperature; 40 °C (hold 10 min) ? 250 °C (rate 5 °C min 1 and hold for 20 min); flow: 1 ml min 1; split ratio: 5:1] for the identification of various hydrocarbons in bio-oil. The compounds in bio-oils were identified by means of the Wiley Library-HP G1035A and NIST library of mass spectra and subsets-HP G1033A. The bio-oils were analyzed to determine the amounts of carbon, nitrogen, hydrogen, sulphur, and oxygen (by calculated from difference) by LECO CHNS 932 Elemental Analyzer according to ASTM D5291-96. The gross calorific values of bio-oils were determined using an IKA C-2000 Basic model analyzer according to ASTM D240-02. The amounts of total aromatic and non-aromatic hydrocarbons in water phases were determined by Headspace-GC analysis. The conditions of Headspace-GC analysis are as follows: An HP-5890 Gas Chromatograph equipped with a Flame Ionization Detector (GC-FID) and Superox-II fused silica capillary column, 60 m 0.32 mm. FID temperature is 250 °C, Column temperature is isothermal, 70 °C. Carrier gas, N2 flow through column is 0.98 ml min 1. Fuel gases, H2 flow through FID is 30 ml min 1 and air flow is 275 ml min 1. Injector temperature is 230 °C and split ratio is 102:1. Headspace conditions are as follows. Oil bath temperature is 80 °C, loop temperature is 90 °C, the volume of sample vial is 20 ml and the volume of sample is 10 ml. Headspace-GC is used for the analysis of volatiles and semi-volatile organics in solid, liquid and gas samples. The headspace is the gas space in a chromatography vial above the sample so headspace analysis is the analysis of the components present in that gas. In a typical run, a sample is prepared in a chromatography vial containing the sample, the dilution solvent, a matrix modifier and headspace. Chromatography vial is heated up to a specific temperature. Volatile components from complex sample mixtures can be extracted from non-volatile sample components and isolated in the headspace (gas portion of a sample vial) at a specific temperature. According to the partition coefficient of each component, system (the contents of the vial) reaches an equilibrium distribution of an analyte between the sample phase and the gas phase. The gas phase in the headspace (gas portion of a sample vial) is directed to a GC system (Superox-II capillary column) by means of a heated line to separate all of the volatile components. This kind of columns is able to separate the aromatic and non-aromatic fractions effectively because of its high polarity. Each component eluted through column is separated and detected by a Flame Ionization Detector. Concentrations of the components were calculated regarding the results obtained by the runs with the calibration samples.
100 90 80 70 60 50 40 30 20 10 0
0 -1 TG DTG
-3 -4
0
100
200
400
500
600
700
800
900
-5 1000
Fig. 1. TG-DTG curves of rapeseed oil cake.
seed oil cake showed three major weight loss steps. The first weight loss step, which corresponds to the removal of moisture content in rapeseed oil cake, occurred at the temperature range between 45 and 170 °C. The second weight loss step, which consists of the volatilization of hemicellulose component in rapeseed oil cake obtained after the first step, occurred at the temperature range between 170 and 240 °C. The inflection point (where the rate of weight loss is maximum) of this step was 230 °C. The third weight loss step occurred between 240 and 540 °C related to degradation of cellulose and lignin component of rapeseed oil cake. This step was the main pyrolysis process and the inflection point of this step was found to be 333 °C. Similar results were reported in a previous study related to TG analysis of the rapeseed oil cake (Culcuoglu et al., 2001). After this major weight loss, there is no further weight loss from the temperature of 540–950 °C. TG-DTG curves of rapeseed oil cake showed that the maximum weight loss occurred in the temperature range from 170 to 500 °C. In addition, total weight loss of rapeseed oil cake was determined as 75.14% at the temperature zone from 45 to 900 °C. The product distributions from pyrolysis of rapeseed oil cake at the temperatures of 400, 450, 500, 700 and 900 °C are shown in Table 2. It can be seen that the product distributions of rapeseed oil cake changed with increasing the temperature. By increasing the pyrolysis temperature from 400 to 450 and 500 °C, the bio-oil yield increased and the bio-char yield decreased. Except 400 °C, the biooil yield was almost the similar for all tested pyrolysis temperatures. This result was expected since it could be seen that from TG-DTG curves of rapeseed oil cake, there was no remarkable decomposition after 500 °C. Similarly, the fixed bed pyrolysis of rapeseed was investigated in the previous reports (Sensoz et al., 2000a; Sensoz et al., 2001). They found that the maximum liquid product was obtained in the temperature of 500 °C. With increasing the temperature from 500 to 700 and 900 °C, the bio-oil yield decreased slightly while the gas yield increased. As expected, gasification of bio-chars occurred at 700 and 900 °C so the bio-char yield was found to be the lowest at 900 °C. 3.2. Composition of gas products The weight percentages of gases products from the pyrolysis of rapeseed oil cake at 500 °C as follows: C1: 6.93, C2: 3.82, C3: 3.41, Table 2 Product distributions from the pyrolysis of rapeseed oil cake at 400, 450, 500, 700 and 900 °C
3. Results and discussion
The TG and Derivative Thermogravimetric (DTG) curves of rapeseed oil cake are shown in Fig. 1. The thermal degradation of rape-
300
Temperatue, ºC
Reaction products, wt%
3.1. Decomposition of rapeseed oil cake and product distributions
-2
Derivative Weight, (%/min)
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Gasa Bio-oil Water Bio-char a
Temperature, °C 400
450
500
700
900
7.70 14.23 39.67 38.40
7.38 18.18 39.78 34.66
8.18 18.58 40.01 33.23
12.31 17.51 38.01 32.17
14.12 17.39 38.45 30.04
Calculated from difference.
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Table 3 Ultimate analysis of bio-oils from the pyrolysis of rapeseed oil cake at 400, 450 and 500 °C Elemental analysis, wt%
Pyrolysis temperature (°C) 400
450
500
C H N S Oa H/C molar ratio O/C molar ratio Empirical formula GCVb, MJ kg-1
64.05 8.48 8.58 0.52 18.37 1.59
64.26 8.55 8.82 0.54 17.83 1.59
66.80 8.72 9.05 0.59 14.84 1.56
0.21
0.20
0.16
a b
CH1.59O0.21N0.115S0.003 CH1.59O0.20N0.117S0.003 CH1.56O0.16N0.116S0.003 32.85
33.05
33.17
Calculated from difference. Gross calorific value.
C4: 2.86, C5: 1.56, C6: 1.08, C7: 0.35, CO: 7.65, CO2: 68.79, H2: 0.44 and H2S: 3.11 wt%. It can be seen that the gas composition from the pyrolysis of rapeseed oil cake at 500 °C was mainly composed of CO2, CO and C1 together with some C2–C7 and H2S. The COx gases must be derived from oxygenated compounds such as cellulose, hemicellulose and lignin of rapeseed oil cake. The major gas being CO2 from pyrolysis of biomass materials have also been found by other researchers. The gas released from the pyrolysis of olive stones was composed by CO, CO2, CH4, C2H4, C2H6 and H2 (Lopez et al., 2002). The major gas product was CO2 at 450 °C similar to the present study. Moreover, the flash pyrolysis of biomass in a circulating fluid bed reactor was studied and the oxygen compounds
in the gas products (CO and CO2) were obtained as dominant (Lappas et al., 2002). In this study, it was also determined H2S from the pyrolysis of rapeseed oil cake, which was not mentioned most of the biomass pyrolysis studies. The formation of the H2S was derived from the nature of rapeseed oil cake since it contained 0.88 wt% sulphur (see Table 1). 3.3. Composition of liquid products Ultimate analysis of bio-oils from the pyrolysis of rapeseed oil cake at the temperatures of 400, 450 and 500 °C is shown in Table 3. The amount of carbon in bio-oil was the same for the temperatures of 400 and 450 °C. The carbon yield in bio-oil was increased slightly to 66.80 wt% at 500 °C. The amounts of hydrogen in biooils were similar for all pyrolysis temperatures. Empirical formula of bio-oil obtained from the pyrolysis of rapeseed oil cake at 500 °C was CH1.59O0.16N0.116S0.003. The gross calorific values of bio-oils did not change with increasing the pyrolysis temperature. The empirical formula and gross calorific value of bio-oil at 500 °C were very similar to the previous report (Ozcimen and Karaosmanoglu, 2004). The bio-oil characterization was realized by using GC–Mass Spectrometry at the pyrolysis temperatures of 400, 450 and 500 °C. The areas of major compounds in bio-oils are given in Table 4. They were classified with increasing the retention times. Taking into account of area percentage, the highest peak areas of total ion chromatogram (TIC) of compounds were (Z)-9-octadecenoic acid (oleic acid), 1H-indole, 2,3,5-trimethoxy toluene, toluene, phenol, 2,6-dimethoxy-phenol, (Z)-9-octadecenamide and 7H-furo[3,2-g] benzopyran-7-one (psoralene). The highest peak area from the chromatogram of GC-Mass was obtained with oleic acid for all tested pyrolysis temperature. Oleic
Table 4 GC-Mass composition of the major compounds in bio-oils from pyrolysis of rapeseed oil cake at 400, 450 and 500 °C No
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30
R.T. (min)
10.99 11.98 14.65 17.33 19.92 22.69 23.39 25.24 25.41 26.22 28.29 29.20 30.61 32.64 33.73 34.19 35.27 36.85 37.82 38.87 39.72 43.00 44.60 45.40 47.32 48.79 51.37 52.22 52.62 56.43
Quality
91 91 95 94 94 91 91 70 96 97 86 87 92 94 92 94 93 50 55 90 83 78 50 53 60 98 99 99 96 98
Name of compounds
1H-Pyrrole Toluene 2-Methyl pyridine Ethyl benzene 2,5-Dimethyl-1H-pyrrole Phenol 2-Ethyl-4-methyl-1H-pyrrole 2-Acetyl-1H-pyrrole 2-Methyl-phenol (o-cresol) 4-Methyl-phenol (p-cresol) 2,4-Dimethyl-phenol 4-Ethyl-phenol 3-Phenyl propionitrile 1H-Indole 1-Methyl-pyrrolo (1,2-A) pyrazine 2,6-Dimethoxy-phenol 3-Methyl-1H-Indole 3-Pyridinemethanamine N-isobutyl aniline 2,3,5-Trimethoxy toluene 1,4-Dihydrophenanthrene 7H-Furo[3,2-g]benzopyran-7-one (Psoralene) p-Toluen sulfonic acid, n-heptyl ester 3-(Hydroxymethyl)-5-methoxy-phenol Hexadecanitrile n-Hexadecanoic acid (Palmitic acid) (E) 9-Octadecenoic acid, methyl ester (Z) 9-Octadecenoic acid (Oleic acid) Hexadecanamide (Z) 9-Octadecenamide
Molecular formula
C4H5N C7H8 C6H7N C8H10 C6H9N C6H6O C7H11N C6H7NO C7H8O C7H8O C8H10O C8H10O C9H9N C8H7N C8H8N2 C8H10O3 C9H9N C6H8N2 C10H15N C10H14O3 C14H12 C11H6O3 C14H22O3S C8H10O3 C16H31N C16H32O2 C19H36O2 C18H34O2 C16H33NO C18H35NO Total Area:
Area, % 400 °C
450 °C
500 °C
1.99 3.84 1.22 1.08 0.86 3.28 0.58 0.77 1.24 2.13 2.06 2.08 1.40 4.35 1.14 3.15 2.02 0.89 1.09 3.88 0.41 1.78 1.32 0.96 1.92 1.90 0.89 12.61 1.10 2.62 63.57
1.59 3.37 1.08 0.90 0.68 3.53 0.45 0.74 1.30 2.37 1.74 1.23 1.35 4.59 1.18 2.25 2.42 1.06 1.27 3.69 0.54 2.91 1.35 1.40 2.06 1.37 0.85 12.27 1.13 2.92 62.53
1.68 3.27 1.17 0.90 0.66 2.68 0.51 1.01 1.54 2.29 1.85 2.72 1.23 4.78 0.46 2.16 2.44 1.23 1.35 4.59 1.55 2.70 1.45 1.44 2.49 0.85 1.55 12.10 1.18 3.53 66.13
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S. Ucar, A.R. Ozkan / Bioresource Technology 99 (2008) 8771–8776 Table 5 Properties of bio-chars from the pyrolysis of rapeseed oil cake at 400, 500, 700 and 900 °C Pyrolysis temperature, °C Bulk density, at 25 °C, kg/m3 Proximate analysis Volatile matter Fixed carbon Ash
400 674.8
500 682.80
700 687.5
900 717.3
25.01 57.08 17.91
20.01 61.45 18.54
5.76 72.30 21.94
3.50 73.05 23.45
Ultimate analysis (dry, wt%) C H N S Oa H/C molar ratio O/C molar ratio Empirical formula
55.85 2.75 6.47 0.20 34.73 0.59 0.46 CH0.59O0.46N0.099S0.001
56.48 3.22 7.52 0.23 32.55 0.68 0.43 CH0.68O0.43N0.114S0.001
64.02 1.88 6.83 0.24 27.03 0.35 0.31 CH0.35O0.31N0.091S0.001
69.25 1.22 5.15 0.21 24.17 0.21 0.26 CH0.21O0.26N0.063S0.001
GCVb, MJ kg
24.12
23.88
24.68
24.66
a b
1
Calculated from difference. Gross calorific value.
acid (C18H34O2) is a monounsaturated omega-9 fatty acid found in various animal and vegetable sources. The saturated form of this acid is stearic acid. It is used in Lorenzo’s oil (Bishop, 2000). Second major compound was 1H-indole. Natural jasmine oil, used in the perfume industry, contains around 2.5% of 1H-indole (C8H7N). Also, 1H-indole is used in the manufacture of synthetic jasmine oil. Another major compound of bio-oil was psoralene (C11H6O3). It is the parent compound in a family of natural products known as furocoumarins. An important use of psoralene is in PUVA treatment for skin problems such as psoriasis, eczema and vitiligo. This takes advantage of the high UV absorbance of psoralene. It has also been recommended for treating alopecia (Dean, 1963). The amounts of hydrocarbons in water phase of liquid product from the pyrolysis of rapeseed oil cake at 500 °C were determined. Both non-aromatic and aromatic hydrocarbon compounds in water phase were identified by Headspace-GC analysis. The total nonaromatic hydrocarbons were obtained 2520 ppm while total aromatic hydrocarbons were determined as 6.4 ppm in water phase. Headspace-GC analysis showed that the most of organic materials were extracted with diethyl ether from aqueous phase to organic phase. 3.4. Composition of solid products Some physico-chemical properties of bio-chars from the pyrolysis of rapeseed oil cake at 400, 500, 700 and 900 °C are shown in Table 5. Bulk densities of bio-chars were gone up with increasing the temperature from 400 to 900 °C. As expected, the amount of volatile matter in bio-char was the highest at 400 °C besides the other tested pyrolysis temperatures. By increasing the temperature from 400 to 900 °C, the amount of fixed carbon of bio-char increased from 57.08 to 73.05 wt% and the ash contents of bio-chars was increased slightly. Ultimate analyses of bio-chars showed that the carbon amounts were increased with increasing the pyrolysis temperature from 400 to 900 °C. However, the amount of hydrogen, nitrogen and sulphur in bio-chars slightly changed with increasing the temperature. The gross calorific values of bio-chars were found to be similar for all pyrolysis temperatures. 4. Conclusions The pyrolysis of rapeseed oil cake was carried out at the temperatures of 400, 450, 500, 700 and 900 °C. The yield of bio-oil was increased with increasing the temperature from 400 to
500 °C. By increasing the temperature from 500 to 700 and 900 °C, the bio-oil yield decreased slightly. The pyrolysis gas products consisted of CO2, CO, C1–C7 and H2S at the temperature of 500 °C. CO2 was found the highest amount of gas in the gas products. The gross calorific value of bio-oil at 500 °C is 33.17 MJ kg 1 which equals to coal (32–37 MJ kg 1). The relative amount of oleic acid in bio-oils was the highest for all pyrolysis temperatures. In addition, other major compounds of bio-oil were 1H-indole, 2,3,5-trimethoxy toluene, toluene, (Z)-9-octadecanamide, psoralene, phenol and phenol derivatives. As a result, the separation and analysis procedure in the present study is simple and may be applicable at industrial scale. Moreover, each of the pyrolysis products can be utilized as a hydrocarbon source for different applications. For instance, bio-oil can be used as a liquid fuel after upgrading or chemical feedstock after separation. Bio-char can be used as a solid fuel or production of active carbon. Acknowledgements This work was supported by Dokuz Eylül University, Scientific Research Project by 2006-KB FEN-010. I would like to acknowledge to Dr. Selhan KARAGOZ for discussion of GC-Mass results. Special thanks are due to General Manager of Mr. Ilhan GUNC for raw material support and technical information from Altinyag Oil Company-Izmir. Thanks go to technician Mr. Ilkay AKGUN for technical assistance in the laboratory. References ASTM D240-02, 2007. Standard Test Method for Heat of Combustion of Liquid Hydrocarbon Fuels by Bomb Calorimeter. American Society for Testing and Materials, Conshohocken, PA, USA. ASTM D3174-04, 2006. Standard Test Method for Ash in the Analysis Sample of Coal and Coke from Coal. American Society for Testing and Materials, Conshohocken, PA, USA. ASTM D3175-89a, 1997. Standard Test Method for Volatile Matter in the Analysis Sample of Coal and Coke. American Society for Testing and Materials, Conshohocken, PA, USA. ASTM D5291-96, 2007. Standard Test Methods for Instrumental Determination of Carbon, Hydrogen, and Nitrogen in Petroleum Products and Lubricants. American Society for Testing and Materials, Conshohocken, PA, USA. Bishop, P.L., 2000. Pollution Prevention Fundamentals and Practice. McGraw-Hill Book Co., New York. Culcuoglu, E., Ünay, E., Karaosmanoglu, F., 2001. Thermogravimetric analysis of the rapeseed cake. Energy Sources 23, 889–895. Dean, F.M., 1963. Naturally Occurring Oxygen Ring Compounds. Butterworths, London.
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FAO, 1993. Production Yearbook, FAO Statistics Series No-112, vol. 46. Food and Agriculture Organization of the United Nations, Rome. FAO, 2006. Statistical Yearbook, vols. 2/1 and 2/2. Food and Agriculture Organization of the United Nations, Rome. Haykiri-Acma, H., Yaman, S., Kucukbayrak, S., 2006. Effect of heating rate on the pyrolysis yields of rapeseed. Renewable Energy 31, 803–810. Karagoz, S., Bhaskar, T., Muto, A., Sakata, Y., Oshiki, T., Kishimoto, T., 2005. Lowtemperature catalytic hydrothermal treatment of wood biomass: analysis of liquid products. Chemical Engineering Journal 108, 127–137. Karaosmanoglu, F., Tetik, E., Gollu, E., 1999. Biofuel production using slow pyrolysis of the straw and stalk of the rapeseed plant. Fuel Processing Technology 59, 1– 12. Lappas, A.A., Samolada, M.C., Iatridis, D.K., Voutetakis, S.S., Vasalos, I.A., 2002. Biomass pyrolysis in a circulating fluid bed reactor for the production of fuels and chemicals. Fuel 81, 2087–2095. Li, S., Xu, S., Liu, S., Yang, C., Lu, Q., 2004. Fast pyrolysis of biomass in free-fall reactor for hydrogen-rich gas. Fuel Processing Technology 85, 1201–1211. Lopez, M.C.B., Blanco, C.G., Martinez-Alonso, A., Tascon, J.M.D., 2002. Composition of gases released during olive stones pyrolysis. Journal of Analytical and Applied Pyrolysis 65, 313–322. McKendry, P., 2002. Energy production from biomass (Part 2): conversion technologies. Bioresource Technology 83, 47–54. Oil World Annual, 2006. Global Analysis all Major Oilseeds, Oils&Oilmeals, vol. 1-up to 2005, Hamburg, Germany. Onay, O., Kockar, O.M., 2003. Slow, fast and flash pyrolysis of rapeseed. Renewable Energy 28, 2417–2433.
Onay, O., Kockar, O.M., 2004. Fixed-bed pyrolysis of rapeseed (Brassica napus L.). Biomass and Bioenergy 26, 289–299. Onay, O., Kockar, O.M., 2006. Pyrolysis of rapeseed in a free fall reactor for production of bio-oil. Fuel 85, 1921–1928. Ozcimen, D., Karaosmanoglu, F., 2004. Production and characterization of bio-oil and bio-char from rapeseed cake (Technical note). Renewable Energy 29, 779– 787. Putun, E., Uzun, B.B., Putun, A.E., 2006. Fixed-bed catalytic pyrolysis of cotton-seed cake: effects of pyrolysis temperature, natural zeolite content and sweeping gas flow rate. Bioresource Technology 97, 701–710. Ramachandran, S., Singh, S.K., Larroche, C., Soccol, C.R., Pandey, A., 2007. Oil cakes and their biotechnological applications – a review. Bioresource Technology 98, 2000–2009. Sensoz, S., Angın, D., Yorgun, S., Kockar, O.M., 2000a. Bio-oil production from an oilseed crop: fixed-bed pyrolysis of rapeseed (Brassica napus L.). Energy Sources 22, 891–899. Sensoz, S., Angın, D., Yorgun, S., 2000b. Influence of particle size on the pyrolysis of rapeseed, (Brassica napus L.): fuel properties of bio-oil. Biomass and Bioenergy 19, 271–279. Sensoz, S., Yorgun, S., Angın, D., Çulcuoglu, E., Ozcimen, D., Karaosmanoglu, F., 2001. Fixed bed pyrolysis of the rapeseed cake. Energy Sources 23, 873–876. Sensoz, S., Kaynar, I., 2006. Bio-oil production from soybean (Glycine max L.); fuel properties of bio-oil. Industrial Crops and Products 23, 99–105. Yorgun, S., Sensoz, S., Kockar, O.M., 2001. Flash pyrolysis of sunflower oil cake for production of liquid fuels. Journal of Analytical and Applied Pyrolysis 60, 1–12.
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Characterization of products from the pyrolysis of rapeseed oil cake Suat Ucar a,*, Ahmet R. Ozkan b a b
Chemistry Program, Izmir Vocational School, Dokuz Eylul University, 35160-Buca-Izmir, Turkey Quality Control and Technical Service, Petkim Holding Co., Aliaga, 35800 Izmir, Turkey
a r t i c l e
i n f o
Article history: Received 6 July 2007 Received in revised form 7 April 2008 Accepted 12 April 2008 Available online 3 June 2008 Keywords: Rapeseed oil cake Pyrolysis Bio-oil Oleic acid Phenols
a b s t r a c t The main aim of this study was to investigate the composition of products from the pyrolysis of rapeseed oil cake in a fixed bed reactor at 400, 450, 500, 700 and 900 °C. The gas products mainly consisted of CO2, CO, CH4 and H2S at 500 °C. Empirical formula of bio-oil from the pyrolysis of rapeseed oil cake was CH1.59O0.16N0.116S0.003 for 500 °C. Bio-oils mainly contained oleic acid, 1H-indole, 2,3,5-trimethoxy toluene, toluene, (Z)-9-octadecanamide, psoralene, phenol and phenol derivatives at all pyrolysis temperatures. Both non-aromatic and aromatic hydrocarbon compounds were determined in water phase of liquid product by Headspace-GC analysis. The heating values of bio-chars were found to be similar (24 MJ kg 1) at all pyrolysis temperatures. Ó 2008 Elsevier Ltd. All rights reserved.
1. Introduction Biomass is a renewable energy resource derived from all the organic materials produced by human and natural activities. It is a complex mixture of organic materials such as carbohydrates, fats and proteins. The main components of the plant biomass are carbohydrates and lignin which can vary with biomass type. The carbohydrates are mainly cellulose or hemicellulose fibers which give strength to the plant structure and lignin which holds the fibers together. Some plants also store starch and fats as sources of energy, mainly in seeds and roots. Some of the biomass types are by-products of the agricultural crops, raw material from the forest, municipal solid waste, animal and human waste. In the developed world, biomass has become more important for applications such as combined heat and power generation. Moreover, it is a source of clean energy and can be replaced fossil fuels. There are a number of technological options available to make use of a wide variety of biomass types as a renewable energy source. These technologies can be classified into two main groups; biochemical (Ramachandran et al., 2007; McKendry, 2002) and thermochemical conversion (McKendry, 2002). Biochemical conversion is the use of the enzymes of bacteria and other microorganisms to convert biomass to fuels and chemicals. Biochemical conversion process includes anaerobic digestion, fermentation and mechanical extraction. Thermochemical conversion can be performed using some processes which are gasification, pyrolysis (slow, fast, flash, and vacuum), hydrothermal upgrading (in water * Corresponding author. Tel.: +90 232 420 48 93; fax: +90 232 420 51 81. E-mail address: [email protected] (S. Ucar). 0960-8524/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.biortech.2008.04.040
or solvent) and combustion. Pyrolysis is the technique of applying high heat to organic matter under the inert atmosphere which results in the converting organic materials into usable fuels and chemical feedstock. This process applied to lignocellulosic materials can produce charcoal, condensable organic liquids (pyrolytic bio fuel) and non-condensable gasses. It is the most effective process for biomass conversion. Rapeseed, which contains around 40% rape oil, is one of the most important oil seed for the production of vegetable oil in the world. The total production of rapeseed plant all around the world was 46.2 Mt in 2005 (FAO, 2006). The production of rapeseed oil in the world was 17.9 Mt in 2005 (Oil World Annual, 2006). Rapeseed oil cake, which is the solid residue remaining after extraction of the oil from the rapeseed, is the most commonly preferred in animal feed because it contains 16–24% protein. All parts of the rapeseed (straw, stalk, seed, oil, and cake) are used as a biomass resource for the production of biofuels and bio-diesel. Even though rapeseed is the third most valuable vegetable oils’ source in the world, it is not commonly grown in Turkey. The annual production of rapeseed plant in Turkey was merely 1000 Mt in 2005 (Oil World Annual, 2006). Thus, a large amount of rapeseed is imported. In the future, rapeseed plant could be expected to become one of the major oil seed crops by the Southeastern Anatolia Project (GAP) in the southeast of Turkey. Because of this, the evaluation of rapeseed is important for Turkey not only for the production of vegetable oil but also production of bio-diesel and bio-oil by thermochemical conversion. With its 25 million hectares of arable land, Turkey has a vast agricultural production and crop diversity (FAO, 1993). Hence, it is very important that agricultural residues in Turkey can be utilized as energy sources to cover the energy
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demand of Turkey from renewable sources. Recent studies related to the pyrolysis of agricultural residues showed that Turkey has to adapt new long-term energy strategies to produce domestic energy from biomass sources (Onay and Kockar, 2004; Sensoz and Kaynar, 2006; Putun et al., 2006; Yorgun et al., 2001). There have been number of studies which dealt with the pyrolysis of rapeseed. In these studies, the influence of final pyrolysis temperature, (Karaosmanoglu et al., 1999; Sensoz et al., 2000a; Onay and Kockar, 2003) particle size, (Sensoz et al., 2000b), varying sweep gas velocity, (Sensoz et al., 2001; Ozcimen and Karaosmanoglu, 2004) heating rate (slow, fast, flash pyrolysis) (Onay and Kockar, 2003; Haykiri-Acma et al., 2006) and different reactor types, i.e. fixed bed, tubular, free fall reactor (Sensoz et al., 2000a; Ozcimen and Karaosmanoglu, 2004; Onay and Kockar, 2006) on the pyrolysis product yields and compositions were investigated. In these studies, the bio-oil was characterized by using elemental analysis, various chromatographic and spectroscopic techniques in order to investigate its possibility of being a potential source of renewable fuel and chemical feedstock. In the present investigation, rapeseed oil cake was pyrolyzed at the temperatures of 400, 450, 500, 700 and 900 °C. The main objective of this study is to investigate the effect of pyrolysis temperature on the product distribution and characterization of all pyrolysis products by using different analytical techniques. The gas products were analyzed by gas chromatograph equipped with thermal conductivity detector (GC-TCD). The liquid products were analyzed by means of the gas chromatograph equipped with a mass selective detector analysis (GC–MS), Headspace-GC and an elemental analyzer. The solid products were analyzed by use of an elemental analyzer and a bomb calorimeter. The analysis of rapeseed oil cake was carried out using a Thermogravimetric analyzer and an elemental analyzer.
2.1. Materials Rapeseed (Brassica napus L.) oil cake was supplied by Altinyag Oil Company, Izmir, Turkey and used as received (average particle size 2 mm). The proximate, ultimate and component analyses (Li Table 1 Proximate, ultimate and component analyses of rapeseed oil cake Proximate analysis (as received, wt%) Moisture Volatile matter Fixed carbon Ash
10.59 67.31 15.80 6.30
Ultimate analysis (dry, wt%) C H N S Oa H/C molar ratio O/C molar ratio Empirical formula
45.92 6.21 6.90 0.88 40.09 1.62 0.65 CH1.62O0.65N0.128S0.007
GCVb, MJ kg-11
19.49
Component analysis (dry, wt%) Extractives c Hemicellulose Lignin Cellulose
19.40 41.40 4.99 28.58
a
c
Calculated from difference. Gross calorific value. Toluene/alcohol (2/1) (v/v).
2.2. Pyrolysis procedure Pyrolysis experiments were carried out under nitrogen atmosphere at the temperatures of 400, 450, 500, 700 and 900 °C. Pyrolysis reactor was a fixed bed design and made of stainless steel (316) with 6 cm diameter and 21 cm height and was placed in an electrical furnace. It was heated externally by the electrical furnace. Pyrolysis temperature was measured with an internal NiCr–Ni thermocouple which was placed in the center of pyrolysis reactor. Before the experiments, the reactor was purged by nitrogen gas for 30 min at a flow rate of 30 ml min 1 to remove the air inside. In a typical pyrolysis experiment, a quantity of 116 g of rapeseed oil cake (on a dry base) was loaded and then the reactor temperature was increased with a heating rate of 5 °C min 1 up to the desired pyrolysis temperature and hold for 30 min at the desired temperature. The nitrogen gas swept all volatile products from the reactor into the collection traps. The liquid products were condensed in the first two traps by cooling within ice bath. Non-condensable volatiles were passed through the last two traps containing lead nitrate solution (33 wt%) to absorb the H2S and then the remaining gases were collected in Tedlar plastic bags. 2.3. Analysis procedure Analysis procedure consists of three stages; gas product analyses, liquid product analyses and solid product analyses.
2. Experimental
b
et al., 2004) of rapeseed oil cake are shown in Table 1. Also, oil content of rapeseed oil cake was obtained as 10.3 wt%. The used solvents are diethyl ether, ethyl alcohol, hexane and toluene. The other used chemicals are sodium hydroxide, barium chloride, anhydrous sodium sulfate, lead nitrate and sulfuric acid. All of them were purchased from Aldrich and used as received.
2.3.1. Gas product analyses The gas products collected in Tedlar bag were analyzed by the gas chromatography, HP model 5890 series II with a thermal conductivity detector. A stainless steel packed column (6.0 m 1/ 8 inch Poropack Q, 2.0 m 1/8 inch, MS 5A molecular sieve, serially connected to each other by means of a switching valve) was used. The separation of CO2, C1, C2, C3, C4, C5, C6, and C7 hydrocarbons was done with Poropack Q column and the separation of O2, N2 and CO was carried out with MS 5A column. The amount of hydrogen sulphur in the gas products was determined as lead sulphur precipitate which was formed from the reaction between H2S and lead nitrate solutions in traps. The lead sulphur precipitate was filtered, washed with distillated water, dried at 110 °C and weighted. 2.3.2. Liquid product analyses The liquid product from the pyrolysis of rapeseed oil cake contained the aqueous and organic phase. It was extracted with equal quantity of diethyl ether. The obtained ether fraction (organic phase) was dried over anhydrous sodium sulfate, filtered and evaporated in a rotary evaporator at 25 °C to remove diethyl ether. Then, this fraction was weighted, bottled and denoted as bio-oil. This procedure was carried out according to previous report at which diethyl ether was used as extraction solvent (Karagoz et al., 2005). Since diethyl ether is very good solvent not only extracted all organic matters in liquid products to organic phase but also green and environmentally friendly solvent. After separation of bio-oil and water by extraction, they were analyzed by using following procedures. The gas chromatograph equipped with a mass selective detector analysis of bio-oil was carried out [GC-MSD; HP 6890 System 5973 MSD; column, HP-1; capillary column with dimethylpolysiloxane, 50 m 0.32 mm i.d.,
2.3.3. Analyses of rapeseed oil cake and solid product Thermogravimetric (TG) analysis of rapeseed oil cake was carried out on Shimadzu-TG-50 instrument. The sample of rapeseed oil cake about 20 mg was placed in a standard alumina crucible. The TG experiments were performed under flowing nitrogen atmosphere with a flow rate of 100 ml min 1. The temperature was increased from ambient temperature to 950 °C with a heating rate of 10 °C min 1. Bio-char products were analyzed by an elemental analyzer and a calorimeter bomb as described in bio-oil analyses. The proximate analyses of rapeseed oil cake and bio-char were done according to ASTM D3174-04 for ash analysis and ASTM D3175-89a for volatile matter.
% Weight
0.52 mm film thickness and the oven temperature; 40 °C (hold 10 min) ? 250 °C (rate 5 °C min 1 and hold for 20 min); flow: 1 ml min 1; split ratio: 5:1] for the identification of various hydrocarbons in bio-oil. The compounds in bio-oils were identified by means of the Wiley Library-HP G1035A and NIST library of mass spectra and subsets-HP G1033A. The bio-oils were analyzed to determine the amounts of carbon, nitrogen, hydrogen, sulphur, and oxygen (by calculated from difference) by LECO CHNS 932 Elemental Analyzer according to ASTM D5291-96. The gross calorific values of bio-oils were determined using an IKA C-2000 Basic model analyzer according to ASTM D240-02. The amounts of total aromatic and non-aromatic hydrocarbons in water phases were determined by Headspace-GC analysis. The conditions of Headspace-GC analysis are as follows: An HP-5890 Gas Chromatograph equipped with a Flame Ionization Detector (GC-FID) and Superox-II fused silica capillary column, 60 m 0.32 mm. FID temperature is 250 °C, Column temperature is isothermal, 70 °C. Carrier gas, N2 flow through column is 0.98 ml min 1. Fuel gases, H2 flow through FID is 30 ml min 1 and air flow is 275 ml min 1. Injector temperature is 230 °C and split ratio is 102:1. Headspace conditions are as follows. Oil bath temperature is 80 °C, loop temperature is 90 °C, the volume of sample vial is 20 ml and the volume of sample is 10 ml. Headspace-GC is used for the analysis of volatiles and semi-volatile organics in solid, liquid and gas samples. The headspace is the gas space in a chromatography vial above the sample so headspace analysis is the analysis of the components present in that gas. In a typical run, a sample is prepared in a chromatography vial containing the sample, the dilution solvent, a matrix modifier and headspace. Chromatography vial is heated up to a specific temperature. Volatile components from complex sample mixtures can be extracted from non-volatile sample components and isolated in the headspace (gas portion of a sample vial) at a specific temperature. According to the partition coefficient of each component, system (the contents of the vial) reaches an equilibrium distribution of an analyte between the sample phase and the gas phase. The gas phase in the headspace (gas portion of a sample vial) is directed to a GC system (Superox-II capillary column) by means of a heated line to separate all of the volatile components. This kind of columns is able to separate the aromatic and non-aromatic fractions effectively because of its high polarity. Each component eluted through column is separated and detected by a Flame Ionization Detector. Concentrations of the components were calculated regarding the results obtained by the runs with the calibration samples.
100 90 80 70 60 50 40 30 20 10 0
0 -1 TG DTG
-3 -4
0
100
200
400
500
600
700
800
900
-5 1000
Fig. 1. TG-DTG curves of rapeseed oil cake.
seed oil cake showed three major weight loss steps. The first weight loss step, which corresponds to the removal of moisture content in rapeseed oil cake, occurred at the temperature range between 45 and 170 °C. The second weight loss step, which consists of the volatilization of hemicellulose component in rapeseed oil cake obtained after the first step, occurred at the temperature range between 170 and 240 °C. The inflection point (where the rate of weight loss is maximum) of this step was 230 °C. The third weight loss step occurred between 240 and 540 °C related to degradation of cellulose and lignin component of rapeseed oil cake. This step was the main pyrolysis process and the inflection point of this step was found to be 333 °C. Similar results were reported in a previous study related to TG analysis of the rapeseed oil cake (Culcuoglu et al., 2001). After this major weight loss, there is no further weight loss from the temperature of 540–950 °C. TG-DTG curves of rapeseed oil cake showed that the maximum weight loss occurred in the temperature range from 170 to 500 °C. In addition, total weight loss of rapeseed oil cake was determined as 75.14% at the temperature zone from 45 to 900 °C. The product distributions from pyrolysis of rapeseed oil cake at the temperatures of 400, 450, 500, 700 and 900 °C are shown in Table 2. It can be seen that the product distributions of rapeseed oil cake changed with increasing the temperature. By increasing the pyrolysis temperature from 400 to 450 and 500 °C, the bio-oil yield increased and the bio-char yield decreased. Except 400 °C, the biooil yield was almost the similar for all tested pyrolysis temperatures. This result was expected since it could be seen that from TG-DTG curves of rapeseed oil cake, there was no remarkable decomposition after 500 °C. Similarly, the fixed bed pyrolysis of rapeseed was investigated in the previous reports (Sensoz et al., 2000a; Sensoz et al., 2001). They found that the maximum liquid product was obtained in the temperature of 500 °C. With increasing the temperature from 500 to 700 and 900 °C, the bio-oil yield decreased slightly while the gas yield increased. As expected, gasification of bio-chars occurred at 700 and 900 °C so the bio-char yield was found to be the lowest at 900 °C. 3.2. Composition of gas products The weight percentages of gases products from the pyrolysis of rapeseed oil cake at 500 °C as follows: C1: 6.93, C2: 3.82, C3: 3.41, Table 2 Product distributions from the pyrolysis of rapeseed oil cake at 400, 450, 500, 700 and 900 °C
3. Results and discussion
The TG and Derivative Thermogravimetric (DTG) curves of rapeseed oil cake are shown in Fig. 1. The thermal degradation of rape-
300
Temperatue, ºC
Reaction products, wt%
3.1. Decomposition of rapeseed oil cake and product distributions
-2
Derivative Weight, (%/min)
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Gasa Bio-oil Water Bio-char a
Temperature, °C 400
450
500
700
900
7.70 14.23 39.67 38.40
7.38 18.18 39.78 34.66
8.18 18.58 40.01 33.23
12.31 17.51 38.01 32.17
14.12 17.39 38.45 30.04
Calculated from difference.
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Table 3 Ultimate analysis of bio-oils from the pyrolysis of rapeseed oil cake at 400, 450 and 500 °C Elemental analysis, wt%
Pyrolysis temperature (°C) 400
450
500
C H N S Oa H/C molar ratio O/C molar ratio Empirical formula GCVb, MJ kg-1
64.05 8.48 8.58 0.52 18.37 1.59
64.26 8.55 8.82 0.54 17.83 1.59
66.80 8.72 9.05 0.59 14.84 1.56
0.21
0.20
0.16
a b
CH1.59O0.21N0.115S0.003 CH1.59O0.20N0.117S0.003 CH1.56O0.16N0.116S0.003 32.85
33.05
33.17
Calculated from difference. Gross calorific value.
C4: 2.86, C5: 1.56, C6: 1.08, C7: 0.35, CO: 7.65, CO2: 68.79, H2: 0.44 and H2S: 3.11 wt%. It can be seen that the gas composition from the pyrolysis of rapeseed oil cake at 500 °C was mainly composed of CO2, CO and C1 together with some C2–C7 and H2S. The COx gases must be derived from oxygenated compounds such as cellulose, hemicellulose and lignin of rapeseed oil cake. The major gas being CO2 from pyrolysis of biomass materials have also been found by other researchers. The gas released from the pyrolysis of olive stones was composed by CO, CO2, CH4, C2H4, C2H6 and H2 (Lopez et al., 2002). The major gas product was CO2 at 450 °C similar to the present study. Moreover, the flash pyrolysis of biomass in a circulating fluid bed reactor was studied and the oxygen compounds
in the gas products (CO and CO2) were obtained as dominant (Lappas et al., 2002). In this study, it was also determined H2S from the pyrolysis of rapeseed oil cake, which was not mentioned most of the biomass pyrolysis studies. The formation of the H2S was derived from the nature of rapeseed oil cake since it contained 0.88 wt% sulphur (see Table 1). 3.3. Composition of liquid products Ultimate analysis of bio-oils from the pyrolysis of rapeseed oil cake at the temperatures of 400, 450 and 500 °C is shown in Table 3. The amount of carbon in bio-oil was the same for the temperatures of 400 and 450 °C. The carbon yield in bio-oil was increased slightly to 66.80 wt% at 500 °C. The amounts of hydrogen in biooils were similar for all pyrolysis temperatures. Empirical formula of bio-oil obtained from the pyrolysis of rapeseed oil cake at 500 °C was CH1.59O0.16N0.116S0.003. The gross calorific values of bio-oils did not change with increasing the pyrolysis temperature. The empirical formula and gross calorific value of bio-oil at 500 °C were very similar to the previous report (Ozcimen and Karaosmanoglu, 2004). The bio-oil characterization was realized by using GC–Mass Spectrometry at the pyrolysis temperatures of 400, 450 and 500 °C. The areas of major compounds in bio-oils are given in Table 4. They were classified with increasing the retention times. Taking into account of area percentage, the highest peak areas of total ion chromatogram (TIC) of compounds were (Z)-9-octadecenoic acid (oleic acid), 1H-indole, 2,3,5-trimethoxy toluene, toluene, phenol, 2,6-dimethoxy-phenol, (Z)-9-octadecenamide and 7H-furo[3,2-g] benzopyran-7-one (psoralene). The highest peak area from the chromatogram of GC-Mass was obtained with oleic acid for all tested pyrolysis temperature. Oleic
Table 4 GC-Mass composition of the major compounds in bio-oils from pyrolysis of rapeseed oil cake at 400, 450 and 500 °C No
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30
R.T. (min)
10.99 11.98 14.65 17.33 19.92 22.69 23.39 25.24 25.41 26.22 28.29 29.20 30.61 32.64 33.73 34.19 35.27 36.85 37.82 38.87 39.72 43.00 44.60 45.40 47.32 48.79 51.37 52.22 52.62 56.43
Quality
91 91 95 94 94 91 91 70 96 97 86 87 92 94 92 94 93 50 55 90 83 78 50 53 60 98 99 99 96 98
Name of compounds
1H-Pyrrole Toluene 2-Methyl pyridine Ethyl benzene 2,5-Dimethyl-1H-pyrrole Phenol 2-Ethyl-4-methyl-1H-pyrrole 2-Acetyl-1H-pyrrole 2-Methyl-phenol (o-cresol) 4-Methyl-phenol (p-cresol) 2,4-Dimethyl-phenol 4-Ethyl-phenol 3-Phenyl propionitrile 1H-Indole 1-Methyl-pyrrolo (1,2-A) pyrazine 2,6-Dimethoxy-phenol 3-Methyl-1H-Indole 3-Pyridinemethanamine N-isobutyl aniline 2,3,5-Trimethoxy toluene 1,4-Dihydrophenanthrene 7H-Furo[3,2-g]benzopyran-7-one (Psoralene) p-Toluen sulfonic acid, n-heptyl ester 3-(Hydroxymethyl)-5-methoxy-phenol Hexadecanitrile n-Hexadecanoic acid (Palmitic acid) (E) 9-Octadecenoic acid, methyl ester (Z) 9-Octadecenoic acid (Oleic acid) Hexadecanamide (Z) 9-Octadecenamide
Molecular formula
C4H5N C7H8 C6H7N C8H10 C6H9N C6H6O C7H11N C6H7NO C7H8O C7H8O C8H10O C8H10O C9H9N C8H7N C8H8N2 C8H10O3 C9H9N C6H8N2 C10H15N C10H14O3 C14H12 C11H6O3 C14H22O3S C8H10O3 C16H31N C16H32O2 C19H36O2 C18H34O2 C16H33NO C18H35NO Total Area:
Area, % 400 °C
450 °C
500 °C
1.99 3.84 1.22 1.08 0.86 3.28 0.58 0.77 1.24 2.13 2.06 2.08 1.40 4.35 1.14 3.15 2.02 0.89 1.09 3.88 0.41 1.78 1.32 0.96 1.92 1.90 0.89 12.61 1.10 2.62 63.57
1.59 3.37 1.08 0.90 0.68 3.53 0.45 0.74 1.30 2.37 1.74 1.23 1.35 4.59 1.18 2.25 2.42 1.06 1.27 3.69 0.54 2.91 1.35 1.40 2.06 1.37 0.85 12.27 1.13 2.92 62.53
1.68 3.27 1.17 0.90 0.66 2.68 0.51 1.01 1.54 2.29 1.85 2.72 1.23 4.78 0.46 2.16 2.44 1.23 1.35 4.59 1.55 2.70 1.45 1.44 2.49 0.85 1.55 12.10 1.18 3.53 66.13
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S. Ucar, A.R. Ozkan / Bioresource Technology 99 (2008) 8771–8776 Table 5 Properties of bio-chars from the pyrolysis of rapeseed oil cake at 400, 500, 700 and 900 °C Pyrolysis temperature, °C Bulk density, at 25 °C, kg/m3 Proximate analysis Volatile matter Fixed carbon Ash
400 674.8
500 682.80
700 687.5
900 717.3
25.01 57.08 17.91
20.01 61.45 18.54
5.76 72.30 21.94
3.50 73.05 23.45
Ultimate analysis (dry, wt%) C H N S Oa H/C molar ratio O/C molar ratio Empirical formula
55.85 2.75 6.47 0.20 34.73 0.59 0.46 CH0.59O0.46N0.099S0.001
56.48 3.22 7.52 0.23 32.55 0.68 0.43 CH0.68O0.43N0.114S0.001
64.02 1.88 6.83 0.24 27.03 0.35 0.31 CH0.35O0.31N0.091S0.001
69.25 1.22 5.15 0.21 24.17 0.21 0.26 CH0.21O0.26N0.063S0.001
GCVb, MJ kg
24.12
23.88
24.68
24.66
a b
1
Calculated from difference. Gross calorific value.
acid (C18H34O2) is a monounsaturated omega-9 fatty acid found in various animal and vegetable sources. The saturated form of this acid is stearic acid. It is used in Lorenzo’s oil (Bishop, 2000). Second major compound was 1H-indole. Natural jasmine oil, used in the perfume industry, contains around 2.5% of 1H-indole (C8H7N). Also, 1H-indole is used in the manufacture of synthetic jasmine oil. Another major compound of bio-oil was psoralene (C11H6O3). It is the parent compound in a family of natural products known as furocoumarins. An important use of psoralene is in PUVA treatment for skin problems such as psoriasis, eczema and vitiligo. This takes advantage of the high UV absorbance of psoralene. It has also been recommended for treating alopecia (Dean, 1963). The amounts of hydrocarbons in water phase of liquid product from the pyrolysis of rapeseed oil cake at 500 °C were determined. Both non-aromatic and aromatic hydrocarbon compounds in water phase were identified by Headspace-GC analysis. The total nonaromatic hydrocarbons were obtained 2520 ppm while total aromatic hydrocarbons were determined as 6.4 ppm in water phase. Headspace-GC analysis showed that the most of organic materials were extracted with diethyl ether from aqueous phase to organic phase. 3.4. Composition of solid products Some physico-chemical properties of bio-chars from the pyrolysis of rapeseed oil cake at 400, 500, 700 and 900 °C are shown in Table 5. Bulk densities of bio-chars were gone up with increasing the temperature from 400 to 900 °C. As expected, the amount of volatile matter in bio-char was the highest at 400 °C besides the other tested pyrolysis temperatures. By increasing the temperature from 400 to 900 °C, the amount of fixed carbon of bio-char increased from 57.08 to 73.05 wt% and the ash contents of bio-chars was increased slightly. Ultimate analyses of bio-chars showed that the carbon amounts were increased with increasing the pyrolysis temperature from 400 to 900 °C. However, the amount of hydrogen, nitrogen and sulphur in bio-chars slightly changed with increasing the temperature. The gross calorific values of bio-chars were found to be similar for all pyrolysis temperatures. 4. Conclusions The pyrolysis of rapeseed oil cake was carried out at the temperatures of 400, 450, 500, 700 and 900 °C. The yield of bio-oil was increased with increasing the temperature from 400 to
500 °C. By increasing the temperature from 500 to 700 and 900 °C, the bio-oil yield decreased slightly. The pyrolysis gas products consisted of CO2, CO, C1–C7 and H2S at the temperature of 500 °C. CO2 was found the highest amount of gas in the gas products. The gross calorific value of bio-oil at 500 °C is 33.17 MJ kg 1 which equals to coal (32–37 MJ kg 1). The relative amount of oleic acid in bio-oils was the highest for all pyrolysis temperatures. In addition, other major compounds of bio-oil were 1H-indole, 2,3,5-trimethoxy toluene, toluene, (Z)-9-octadecanamide, psoralene, phenol and phenol derivatives. As a result, the separation and analysis procedure in the present study is simple and may be applicable at industrial scale. Moreover, each of the pyrolysis products can be utilized as a hydrocarbon source for different applications. For instance, bio-oil can be used as a liquid fuel after upgrading or chemical feedstock after separation. Bio-char can be used as a solid fuel or production of active carbon. Acknowledgements This work was supported by Dokuz Eylül University, Scientific Research Project by 2006-KB FEN-010. I would like to acknowledge to Dr. Selhan KARAGOZ for discussion of GC-Mass results. Special thanks are due to General Manager of Mr. Ilhan GUNC for raw material support and technical information from Altinyag Oil Company-Izmir. Thanks go to technician Mr. Ilkay AKGUN for technical assistance in the laboratory. References ASTM D240-02, 2007. Standard Test Method for Heat of Combustion of Liquid Hydrocarbon Fuels by Bomb Calorimeter. American Society for Testing and Materials, Conshohocken, PA, USA. ASTM D3174-04, 2006. Standard Test Method for Ash in the Analysis Sample of Coal and Coke from Coal. American Society for Testing and Materials, Conshohocken, PA, USA. ASTM D3175-89a, 1997. Standard Test Method for Volatile Matter in the Analysis Sample of Coal and Coke. American Society for Testing and Materials, Conshohocken, PA, USA. ASTM D5291-96, 2007. Standard Test Methods for Instrumental Determination of Carbon, Hydrogen, and Nitrogen in Petroleum Products and Lubricants. American Society for Testing and Materials, Conshohocken, PA, USA. Bishop, P.L., 2000. Pollution Prevention Fundamentals and Practice. McGraw-Hill Book Co., New York. Culcuoglu, E., Ünay, E., Karaosmanoglu, F., 2001. Thermogravimetric analysis of the rapeseed cake. Energy Sources 23, 889–895. Dean, F.M., 1963. Naturally Occurring Oxygen Ring Compounds. Butterworths, London.
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