Biomass pyrolysis in a fixed-bed reactor: Effects of pyrolysis parameters on product yields and characterization of products

Energy 64 (2014) 1002e1025

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Biomass pyrolysis in a fixed-bed reactor: Effects of pyrolysis parameters on product yields and characterization of products Tevfik Aysu*, M. Mas¸uk Küçük Yuzuncu Yil University, Educational Faculty, 65080 Van, Turkey

a r t i c l e i n f o

a b s t r a c t

Article history: Received 29 June 2013 Received in revised form 7 October 2013 Accepted 19 November 2013 Available online 16 December 2013

Slow pyrolysis of eastern giant fennel (Ferula orientalis L.) stalks has been performed in a fixed-bed tubular reactor with (ZnO, Al2O3) and without catalyst at six different temperatures ranging from 350
C to 600
C with heating rates of 15, 30, 50
C/min. The amounts of bio-char, bio-oil and gas produced, as well as the compositions of the resulting bio-oils were determined by FT-IR and GCeMS. The effects of pyrolysis parameters such as temperature, catalyst and ratio of catalyst, particle size (Dp) and sweeping gas flow rate on product yields were investigated. According to results, temperature and catalyst seem to be the main factors effecting the conversion of F. orientalis L. into solid, liquid and gaseous products. The highest liquid yield (45.22%) including water was obtained with 15% zinc oxide catalyst at 500
C temperature at a heating rate of 50
C/min when 0.224 > Dp > 0.150 mm particle size raw material and 100 cm3/min of sweeping gas flow rate were used. Ó 2013 Elsevier Ltd. All rights reserved.

Keywords: Energy Biomass Pyrolysis Bio-oil Giant fennel Ferula orientalis L.

1. Introduction In recent years, interest in renewable energies has increased due to environmental concerns about global warming and air pollution and the increasing demands of energy by the world. Among renewable energies, biomass is one of the most plentiful and wellutilised source in the world [1]. Biomass is defined as the plant material derived from the reaction between CO2 in the air, water and sunlight by photosynthesis process which produces carbohydrates, the building blocks of biomass. Biomass resources include woody plants, herbaceous plants, aquatic plants and manures [2]. The obtaining of energy from biomass can be achieved in a number of ways which include production of crops, burning solid wastes, landfill gas and bio-oil production. In recent years, converting biomass to energy was centered mainly to biochemical and thermochemical processes. Of them, thermochemical processes can be subdivided into gasification, pyrolysis, carbonization, and direct liquefaction. Amongst the thermochemical processes, pyrolysis has received much more attention than others as its conditions could be optimized to produce high energy density pyrolytic oils as well as the derived biochar and gas [3]. Pyrolysis is defined as the thermal decomposition of biomass by heat in the absence of oxygen

* Corresponding author. Tel.: þ90 432 225 17 02; fax: þ90 432 225 13 69. E-mail addresses: tevfi[email protected], tevfi[email protected] (T. Aysu). 0360-5442/$ e see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.energy.2013.11.053

which produces solid (bio-char), liquid (bio-oil) and gaseous products. According to operating conditions, pyrolysis processes are generally divided into three sub-classes: conventional or slow pyrolysis, fast pyrolysis and flash pyrolysis. Conventional or slow pyrolysis is performed under the conditions of slow heating rates, low temperatures and, lengthy gas and solids residence times. This type of pyrolysis results in the production of solid, liquid, and gaseous products in significant amounts. If the aim is the production of mainly liquid and gaseous products, the preferred technology is fast or flash pyrolysis at high temperatures with very short residence times [4]. Biomass feedstocks, such as wood, agricultural and forest residues, energy plants, urban and solid industrial wastes, lumber and municipal wastes have attracted great attention as renewable energy sources in the worldwide. Turkey has high potential of agricultural renewable source with diverse crops production in 25 million hectares of arable land [3]. Numerous types of plants grow in the lands of Turkey and they could be used as a source of biomass for production of clean energy or chemicals [5e9]. One of them, commonly named as “eastern giant fennel”, is Ferula orientalis L. is a perennial plant which grows in eastern region of Turkey with 2 m tall massive stalks and numerous clusters of yellow flowers. Essential oils of leaves and flowers of F. orientalis L. are used in folk medicine in a wide range. However, there is no single study of evaluation of its stalks which go dormant by midsummer and no value in terms of industrial respect in the literature. As one of the

T. Aysu, M.M. Küçük / Energy 64 (2014) 1002e1025 Table 1 Main characteristics of the Ferula orientalis L. Components Moisture (%)

5.66 a

Proximate analysis (%) Ash Lignin Cellulose Hemicellulose a-Cellulose Soxhlet extractives (40e60
C petroleum ether)

4.85 26.11 41.28 22.57 45.60 0.87

Ultimate analysisb (%) Carbon Hydrogen Nitrogen Oxygenc H/C molar ratio O/C molar ratio Empirical formula

44.408 6.7357 1.3257 47.5306 1.82 0.81 CH1.82N0.025O0.81

Higher heating value (MJ/kg) Dulong’s formula

16.16

a b c

Weight percentage on dry basis. Weight percentage on dry and ash free basis. By difference.

abundant and fast growing plants found in many parts of Turkey, F. orientalis L. has been chosen with the idea of bio-oil and bio-char or chemical feedstock production from its stalks. Therefore, in this work, considering it as one of the promising species for bio-oil and bio-char production, we have performed the catalytic (ZnO, Al2O3) and non-catalytic slow pyrolysis of its stalks at six different temperatures between 350 and 600
C. Effects of pyrolysis parameters

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such as temperature, types of catalyst, ratio of catalyst, heating rate were investigated. Furthermore, characterization of some of the selected products (bio-chars and bio-oils) obtained from pyrolysis has been carried out elemental, Fourier transform infrared spectroscopy (FT-IR), gas chromatography/mass spectrometry (GCeMS). 2. Materials and methods 2.1. Materials F. orientalis L. plants were collected in an agricultural zones rı province of between the countries of Hamur and Tutak in Ag Turkey. They were harvested in May and the stems cleaned from leaves and tops and dried naturally in open air and then were ground, milled, and screen-sieved. Samples of different particle size ranging between 0.150 and 0.85 mm were used to in this study. Ultimate and proximate analyses of the F. orientalis L. were performed. Ultimate analysis of the sample was carried out using an Elemental analyzer (LECO CHNS 932). The tests for determining the main characteristics of the F. orientalis L. were performed according to Tappi Test methods [10] . Lignin was determined according to Tappi T222. Hollocellulose and cellulose contents were determined using the chloride method [11] and Tappi T202 method. Ash and moisture contents were determined by Tappi T211 and Tappi T264 respectively. Higher heating value was calculated by Dulong’s Formula. Fourier transform infrared (FT-IR) analysis of the F. orientalis L. was also carried out using a Varian model Scimitar 2000 to identify structural groups using potassium bromide as transparent pellets. The results of ultimate and proximate analyses of F. orientalis L. are given in Table 1. FT-IR spectra of raw material are given in Fig. 1. The raw F. orientalis L. was characterized by FT-IR in the middle region, including the wave

Fig. 1. FT-IR spectra of raw material (Ferula orientalis L.).

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Fig. 2. TGeDTA curves of Ferula orientalis L. obtained under nitrogen atmosphere.

numbers between 4000 and 650 cm1. The aim of the analysis was to identify the functional groups of raw material and then compare any structural changes after the liquefaction experiments. The bands in the spectra of raw F. orientalis L. indicate that it is mainly composed of lignin, cellulose and hemicelluloses [12e 15]. The band at 3335 cm1 is caused by OH of lignin in F. orientalis L. The absorption at wave number of 1736 cm1 is the characteristic of xylans of hemicellulose. The absorption peaks at about 3362, 2900,1365 and 1143 cm1 are the characteristics of cellulose. Generally, similar absorption peaks are observed in the spectrum of lignin. The absorptions at 2900, 1600e1500, 1416, 1314, and 830e750 cm1 represent the lignin [12e14]. The characteristic absorption peaks of raw F. orientalis L. prove the presence of lignin, cellulose and hemicelluloses. Before performing the pyrolysis experiments, thermal behaviour of the raw material (F. orientalis L.) was also investigated by

thermogravimetric (TG) and differential thermal analysis (DTA). The thermogravimetric weight loss and the corresponding derivative curves are given in Fig. 2. When TG curve is examined, 6% weight loss until 160
C indicates the amount of moisture content of raw material which is very close to the value given in Table 1. Hemicellulose and cellulose of the raw material, the main components of biomass start to decompose at 225
C. The temperature at which the maximum decomposition occurs is determined as 304
C. All of the components (hemicellulose, cellulose and lignin) of the raw material decompose very rapidly at this temperature reaching a maximum weight loss. At 382
C, rate of decomposition gradually decreases and gets a minimum approximately at 435
C. After 435
C, difference in weight loss gets smaller and becomes zero at 600
C [16,17]. The amount of matter left behind after 600
C is the percentage of ash which is calculated as 4.90% by weight from TG curve.

Fig. 3. Schematic diagram for the fixed-bed tubular reactor system.

T. Aysu, M.M. Küçük / Energy 64 (2014) 1002e1025 Table 2 The conversiona and distribution of products obtained by pyrolysis of Ferula orientalis L. at different temperatures without catalyst. Temperature (
C)

Conversion (%)

Solid (%)

Liquid (%)

Gas (%)

15
C/min 350
C 400
C 450
C 500
C 550
C 600
C

59.74 63.52 65.93 69.44 70.86 73.71

40.26 36.48 34.07 30.56 29.14 26.29

38.61 39.73 41.95 43.07 42.86 41.04

21.13 23.79 23.98 26.37 28.00 32.67

30
C/min 350
C 400
C 450
C 500
C 550
C 600
C

61.25 65.47 68.09 71.62 73.21 75.14

38.75 34.53 31.91 28.58 26.79 24.86

40.52 42.03 42.66 43.55 43.47 41.78

20.73 23.44 25.43 27.87 29.74 33.36

50
C/min 350
C 400
C 450
C 500
C 550
C 600
C

62.88 67.23 70.26 73.85 74.59 76.62

37.12 32.77 29.74 26.15 25.41 23.38

41.89 42.56 43.29 45.02 43.64 42.37

20.99 24.67 26.97 28.83 30.95 34.25

a

Mass fraction percentage of the dry and ash free feedstock.

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2.2. Experimental procedure The slow pyrolysis experiments were performed in a fixed-bed tubular reactor made of stainless steel with dimensions of 70 mm inner diameter, 10 mm outer diameter and 200 mm height equipped with connection for inert gas input. Schematic diagram for the fixed-bed tubular reactor system is given in Fig. 3. In each trial, 20 g of raw material was put inside the reactor, closed tightly with connections for inert gas entry and products output pipe connected to liquid product collecting bottles. The reactor was heated externally by an electric furnace and the temperature is controlled by a NiCreNi thermocouple placed inside the bed. The liquid collecting bottles were cooled to 10
C using frozen salt-ethanol and water mixture and the temperature kept constant as 10
C until no more gas is evolved from pyrolysis process. The gas product was discharged into a chimney through a hose and a fan. During the whole pyrolysis process, nitrogen gas is circulated in the reactor with 100 cm3/min constant flowing rate to provide the inert atmosphere inside the reactor. By inputting the desired variables to the control unit in heater, pyrolysis experiments at different conditions have been performed. The pyrolysis experiments were done in four series. In the first one, experiments without catalyst at six different temperatures ranging from 350
C to 600
C with heating rates of 15, 30, 50
C/ min were carried out to investigate the effect of temperature and heating rate. The condensed liquid products which contain an aqueous (pyrolignic acid) and oil (pyrolytic oil) phase were collected in bottles. They were washed with dichloromethane, put in a

Fig. 4. The effect of pyrolysis temperature and heating rate on the products yields.

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separating funnel and separated from each other by decantation. Pyrolytic oil or bio-oil is dried with anhydrous sodium sulphate and recovered by evaporating the solvent in a rotary evaporator at temperature of 313 K and reduced pressure of 11 kPa and its yield (liquid) were calculated. After cooling the pyrolysis reactor, the amount of solid (bio-char) left behind was removed and weighed. The conversion of raw material to liquid and gaseous products was calculated by subtraction of amount of solid (bio-char) left behind in the reactor. The amount of gas evolved was calculated by subtraction of amount of solid and liquid products from 20, the amount of initial raw material. From the first group of experiments, it was found that 500
C pyrolysis temperature and 50
C/min heating rate provide the optimum conditions for producing highest amount of liquid products in the non-catalytic experiments. In the second group of experiments, two different catalysts (ZnO and Al2O3) with different ratios (5%, 10%, 15%) were added to reactor and pyrolysis experiments at the same temperatures used in non-catalytic runs with constant heating rate of 50
C/min were carried out to investigate the effect of catalyst and catalyst ratio on product yields. After completion of all experiments, the product yields were calculated and expressed on dry and ash free basis. Third group of experiments was performed to determine the effect of particle size on product yields. Four different particle size (0.850 > Dp > 0.425, 0.425 > Dp > 0.300, 0.300 > Dp > 0.224, 0.224 > Dp > 0.150) samples were used and pyrolysis experiments were carried out at the optimum conditions of 500
C pyrolysis temperature with a heating rate of 50
C/min and 100 cm3/min nitrogen gas flow rate.

The last group of experiments was performed to determine the effect of sweeping gas (nitrogen) flow rate on the product yields, specifically liquid product yield. Pyrolysis experiments in this group were conducted with five different sweeping gas flow rates of 100, 150, 200, 250 and 300 cm3/min by using the optimum conditions of 500
C pyrolysis temperature with a heating rate of 50
C/min and 0.224 > Dp > 0.150 mm particle size raw material. 3. Results and discussion 3.1. Effect of temperature and heating rate on product yields The results of pyrolysis and distribution of products obtained at different temperatures with different heating rates without catalyst are given in Table 2. The effects of temperature and heating rate on product yields are given in Fig. 4. The data given in the Fig. 4. were obtained from the experimental runs (Table 2) at different temperatures ranging from 350
C to 600
C with heating rates of 15, 30, 50
C/min. It can be seen from Fig. 4 that temperature has a positive effect either sharply or slightly on both conversion and liquid product yield. According to results, when temperature is increased from 350 to 500
C, liquid product yield increases from 38.61% to 43.07% at a heating rate of 15
C/min, from 40.52% to 43.55% at a heating rate of 30
C/min and from 41.89% to 45.02% at a heating rate of 50
C/min. So, the highest liquid product yield was obtained at 500
C with a heating rate of 50
C/min in the noncatalytic runs. Beyond at 500
C, even though the conversion has

Fig. 5. The effect of aluminium oxide catalyst ratio on the products yields.

T. Aysu, M.M. Küçük / Energy 64 (2014) 1002e1025

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Fig. 6. The effect of zinc oxide catalyst ratio on the products yields.

increased steadily, the liquid yields have decreased to 41.04%, 41.78%, and 42.37% at 600
C at heating of rates of 15, 30, 50
C/min respectively. According to literature, temperature is the most important parameter on product yields [17e21].

In one of the studies carried out by Özbay et al. [22], apricot pulps was pyrolyzed in a fixed-bed reactor under different pyrolysis conditions to determine the role of final temperature, sweeping gas flow rate and steam velocity on the product yields and liquid

Table 3 The conversiona and distribution of products obtained by pyrolysis of Ferula orientalis L. at different temperatures with ZnO catalyst.

Table 4 The conversiona and distribution of products obtained by pyrolysis of Ferula orientalis L. at different temperatures with Al2O3 catalyst.

Temperature (
C)

Conversion (%)

Gas (%)

Temperature (
C)

Conversion (%)

Solid (%)

Liquid (%)

Gas (%)

42.56 43.23 44.65 44.97 42.58 41.54

21.66 24.71 27.17 29.17 32.45 35.28

Catalyst ratio: 5% 350
C 400
C 450
C 500
C 550
C 600
C

66.25 70.59 74.22 76.88 77.53 78.16

33.75 29.41 25.78 23.12 22.47 21.84

41.42 42.38 43.18 44.67 41.73 40.86

24.83 28.21 31.04 32.21 35.80 37.30

33.83 31.44 26.39 24.42 24.23 23.05

42.58 43.01 44.62 44.96 42.47 40.89

23.59 25.55 28.99 30.62 33.30 36.06

Catalyst ratio: 10% 350
C 400
C 450
C 500
C 550
C 600
C

68.82 72.07 75.15 77.26 78.64 78.77

31.18 27.93 24.85 22.74 21.36 21.23

40.83 41.66 42.78 42.21 40.95 39.68

27.99 30.41 32.37 35.05 37.69 39.09

33.07 30.82 25.61 24.32 23.08 22.86

43.08 43.56 45.03 45.22 41.85 40.34

23.85 25.62 29.36 30.46 35.07 36.80

Catalyst ratio: 15% 350
C 400
C 450
C 500
C 550
C 600
C

69.45 73.36 76.89 78.07 78.61 79.24

30.55 26.64 23.11 21.93 21.39 20.76

40.11 40.87 41.59 41.64 39.72 39.13

29.34 32.49 35.30 36.43 38.89 40.11

Solid (%)

Catalyst ratio: 5% 350
C 400
C 450
C 500
C 550
C 600
C

64.22 67.94 71.82 74.14 75.03 76.82

35.78 32.06 28.18 25.86 24.97 23.18

Catalyst ratio: 10% 350
C 400
C 450
C 500
C 550
C 600
C

66.17 68.56 73.61 75.58 75.77 76.95

Catalyst ratio: 15% 350
C 400
C 450
C 500
C 550
C 600
C

66.93 69.18 74.39. 75.68 76.92 77.14

a

Liquid (%)

Mass fraction percentage of the dry and ash free feedstock.

a

Mass fraction percentage of the dry and ash free feedstock.

1008

T. Aysu, M.M. Küçük / Energy 64 (2014) 1002e1025 Table 5 The results of elemental analyses of some of the bio-chars. Elemental analysisa

No catalyst (500
C)

With 15% ZnO (500
C)

With 15% Al2O3 (500
C)

No catalyst (550
C)

With 15% Al2O3 (450
C)

Carbon Hydrogen Nitrogen Oxygenb H/C molar ratio O/C molar ratio Higher heating value (MJ/kg)

63.920 3.2680 0.9490 31.863 0.613 0.373 20.59

63.800 3.0680 0.8180 32.314 0.577 0.379 20.18

67.850 3.4450 0.9940 27.711 0.609 0.306 22.92

70.320 3.5360 0.9260 25.218 0.603 0.268 24.34

59.744 3.7090 1.6790 34.868 0.744 0.437 19.27

a b

Fig. 7. The effect of particle size on the product yields.

product composition with a heating rate of 5
C/min. Final temperature range studied was between 300 and 700
C and the highest liquid product yield was obtained at 550
C. In a most recent study [23], pyrolysis of blue-green algae blooms was carried out by in a fixed-bed reactor to determine the effects of pyrolysis temperature, particle size and sweep gas flow rate on pyrolysis product yields and bio-oil properties. It has been found that the maximum oil yield of 54.97% was obtained at a pyrolysis temperature of 500
C, particle size below 0.25 mm and sweep gas flow rate of 100 mL min1. The gas product yields have increased constantly with increasing pyrolysis temperature. As it is seen from Table 2 and Fig. 4, when temperature is increased from 350 to 600
C, the gas product yield increases from 21.13% to 32.67% at a heating rate of 15
C/min, from 20.73% to 33.36% at a heating rate of 30
C/min and from 20.99% to 34.25% at a heating rate of 50
C/min. The reason of decreasing of liquid product yield and increasing of gaseous product yield at higher pyrolysis temperatures is thought to be the formation of secondary cracking reactions of the pyrolysis vapors. On the other hand, secondary decomposition of the bio-char could

produce non-condensable gaseous substances at higher temperatures contributing an increase in gaseous products [3,17,24e26]. As seen from Fig. 4, in accordance with the previous studies reported in literature [21,27,28] for the slow pyrolysis of various biomass feeds, change in heating rate have slight effects on liquid product yields when compared with fast pyrolysis. Bio-char yields always decreased with increasing the pyrolysis temperature and the heating rate because of greater primary decomposition of the biomass or secondary decomposition of the char residue, leading the higher conversions with increasing temperature. As pyrolysis temperature increases from 350 to 600
C, bio-char yields decrease from 40.26% to 26.29% at a heating rate of 15
C/min, from 38.75% to 24.86% at a heating rate of 30
C/min and from 37.12% to 23.38% at a heating rate of 50
C/min. The higher heating rate causes the solid material to a fast depolymerization to primary volatiles, on the other hand, the lower heating rate leads to a very slow and limited dehydration to more stable anhydrocellulose [29,30]. Table 6 The results of elemental analysesa of some of the bio-oils. Temperature (
C)

No catalyst

With 15% Al2O3

With 15% ZnO

500
C Carbon Hydrogen Nitrogen Oxygenb H/C molar ratio O/C molar ratio Higher heating value (MJ/kg)

53.96 7.410 1.227 37.403 1.647 0.519 22.20

52.44 6.830 1.341 39.389 1.562 0.563 20.49

54.61 6.972 1.232 37.186 1.532 0.510 21.82

450
C Carbon Hydrogen Nitrogen Oxygenb H/C molar ratio O/C molar ratio Higher heating value (MJ/kg)

51.46 7.001 0.964 40.575 1.632 0.591 20.19

52.87 6.861 0.382 39.887 1.557 0.565 20.59

54.70 6.746 0.435 38.119 1.479 0.522 21.36

400
C Carbon Hydrogen Nitrogen Oxygenb H/C molar ratio O/C molar ratio Higher heating value (MJ/kg)

51.89 7.003 0.994 40.113 1.619 0.579 20.42

52.67 6.971 1.054 39.305 1.588 0.559 20.78

53.50 6.943 1.154 38.403 1.557 0.538 21.19

a

Fig. 8. The effect of sweeping gas flow rate on the product yields.

Weight percentage on dry and ash free basis. By difference.

b

Weight percentage on dry and ash free basis. By difference.

T. Aysu, M.M. Küçük / Energy 64 (2014) 1002e1025

Fig. 9. FT-IR spectrums of bio-chars obtained at 450 and 500
C.

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Fig. 9. (continued).

3.2. Effects of catalysts and ratio of catalysts on product yields The effects of catalysts and catalyst ratios on conversion are given in Figs. 5 and 6. The data given in the Figs. 5 and 6 were obtained from the experimental runs given in Tables 3 and 4. Pyrolysis experiments with catalysts were carried out at a constant heating rate of 50
C/min at the same temperatures used in noncatalytic runs to determine both effects of catalysts (ZnO and Al2O3) and catalyst ratio (5, 10, 15%) on the product yields. As seen from Figs. 5 and 6, catalysts have shown different effects on product yields. Both catalysts have increased the conversion with increasing temperature and catalyst ratios compared with noncatalytic runs. Of them, aluminium oxide is more effective than zinc oxide in terms of conversion. The highest conversion (79.24%) was obtained with 15% aluminum oxide in the catalytic runs at 600
C temperature. On the other hand, effects of catalysts on liquid product yields were different from each other. Namely, in the experiments performed with zinc oxide (Fig. 6), the liquid product (bio-oil) yields have increased steadily as the ratio of catalyst increased at the temperatures of 350, 400, 450 and 500
C but have decreased at the temperatures of 550 and 600
C. As for

aluminium oxide (Fig. 5), even though it has much more positive effect on conversion than zinc oxide, the liquid product yields have constantly decreased as the ratio of catalyst increased at all pyrolysis temperatures. The liquid product yield, which was 41.89% without catalyst, reached the maximum value of 40.11% with 15% aluminium oxide catalyst at 350
C. The gaseous product yields for both catalysts have increased with increasing catalyst ratios when compared with non-catalytic runs. For example, the gas product yield of 23.59% at 350
C has increased to 36.06% at 600
C in the catalytic run with 10% zinc oxide. Similar results were observed in the previous studies [31e33]. There are many pyrolysis studies regarding the effect of catalysts on product yields of biomass samples in recent years. The usage of catalyst could make significant changes on the properties and yields of pyrolysis products. Generally, using catalyst has been increased the liquid yields while in some studies, it had negative effect and decreased the liquid product yields [34e41]. Similar results were obtained for bio-char and gaseous product yields which were either increased or decreased by using catalysts [42,43]. The liquid product obtained in pyrolysis contains an aqueous phase and bio-oil or oil phase which is generally named as

T. Aysu, M.M. Küçük / Energy 64 (2014) 1002e1025

Fig. 10. FT-IR spectrums of bio-oils obtained at 500
C.

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Fig. 11. FT-IR spectrums of bio-oils obtained at 450
C.

T. Aysu, M.M. Küçük / Energy 64 (2014) 1002e1025

Fig. 12. FT-IR spectrums of bio-oils obtained at 400
C.

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Fig. 13. FT-IR spectrums of bio-oils obtained at 350
C.

T. Aysu, M.M. Küçük / Energy 64 (2014) 1002e1025

pyrolytic liquid. It is a black liquid containing highly oxygenated compounds used as boiler fuel in power stations for heat production. If it is intended to be used as transportation fuels, they should be upgraded first by hydrodeoxygenation to produce aromatics or hydrocarbons, or catalytic cracking by using zeolite to produce light aromatic hydrocarbons and light alkanes. Aluminium oxide as catalyst, having acidic sites on it, can speed up the dehydration, decarbonylation and hydrogeration reactions occur during pyrolysis. The carbon and hydrogen in the feedstock are converted to carbon monoxide and hydrogen gases. The removal of oxygen to water, carbon monoxide and carbon dioxide may result in low biooil yields [40,44]. One of the recent studies in which zinc oxide was used as catalyst carried out by Zhou et al. [45]. They have used different ratios of biomassecatalyst mixtures to investigate the effect of zinc

1015

oxide on the product yields of pyrolysis of rice husk at 550
C temperature and the sweeping gas (nitrogen) flow rate of 150 cm3/ min. In accordance with our results obtained with zinc oxide catalyst at 550
C and 600
C, they found out that the liquid product yields were decreased approximately 6% (wt) with increasing catalyst ratio while gaseous products were increased. The bio-char yields were not affected by the ratio of catalyst and kept constant. They also observed that the viscosity of the bio-oil obtained by using zinc oxide catalyst was significantly lower than that of the bio-oil obtained without catalyst. 3.3. Effect of particle size on product yields The effect of particle size on the product yields obtained by pyrolysis experiments at constant temperature of 500
C and at a

Fig. 14. GCeMS spectrums of bio-oils obtained at 500
C.

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T. Aysu, M.M. Küçük / Energy 64 (2014) 1002e1025

constant heating rate of 50
C/min is given in Fig. 7. As it is seen from Fig. 7, change in particle size did not effect significantly pyrolysis yields. The highest conversion and liquid yield were 73.85% and 45.02% obtained with a particle size of 0.224 > Dp > 0.150 mm respectively. When particle size is increased 0.224 > Dp > 0.150 to 0.850 > Dp > 0.425, the liquid yield decreased from 45.02% to 43.29% and gas yield from 28.83% to 27.54% while bio-char yield increased from 26.15% to 29.17%. These results are consistent with the previous studies reported in literature, that is, increase in particle size leads to greater temperature gradients inside the particles and the core temperature of the particles is lower than the surface which causes higher bio-char yield and lower bio-oil and gas yields [46e48]. The effect of particle size is explained in terms of heating rate in which bigger particles will heat up more slowly causing lower temperature of average particles which result in less amounts of

volatile yields. Uniform heating could be established with sufficiently small particle size samples. It has been reported that particle size less than 5 mm does not have significant effect on the process rate. The results of our study show that 0.224 > Dp > 0.150 mm and 0.300 > Dp > 0.224 mm particle size samples are the most suitable for obtaining high liquid yields from pyrolysis of F. orientalis L. [3,49]. In a recent work, biomass cellular structure is reported as another element that needs to be taken into account to explain the decreases in liquid yield with increasing biomass particle size. It is proposed that the cell structure may affect the pyrolysis behaviour of biomass, such as the release of alkaline or alkaline earth metallic species. In the preparation of small biomass particles ranging between 0.18 and 0.6 mm by using a cutting mill, much of the cellular structure of biomass is destroyed. The diffusion of pyrolysis products which were formed inside wood cells is

Fig. 15. GCeMS spectrums of bio-oils obtained at 450
C.

T. Aysu, M.M. Küçük / Energy 64 (2014) 1002e1025

affected seriously by cell walls. The increase of intensity of secondary reactions in the closed cells may cause to decrease in the yield of liquid yield. That is to say, during pyrolysis process, cell contents in the small particles are released much more easily than in the big particles [50,51]. 3.4. Effect of sweeping gas flow rate on product yields The effect of sweeping gas flow rate on product yields was determined by performing the pyrolysis experiments with different nitrogen gas flow rates using the optimum conditions (particle size: 0.224 > Dp > 0.150, temperature: 500
C, heating rate:50
C/min) obtained in the first group of experiments. Fig. 8 shows the effect of sweeping gas flow rate on product yields. As seen from Fig. 8, the maximum liquid product yield of 46.87% was obtained at a sweeping gas flow rate of 200 cm3/min. The conversion and liquid product yields were increased with increasing sweeping gas flow

1017

rate, reaching the maximum values at 200 cm3/min, and then decreased. The gas and bio-char yields, on the other hand, first decreased with increasing sweeping gas flow rate, reaching the minimum values at 200 cm3/min, and then start to increase. The liquid product yield was increased from 45.02% to 46.87%, when nitrogen flow rate was increased from 100 cm3/min to 200 cm3/min and then decreased to 42.56% at 300 cm3/min flow rate. The gas yield was decreased from 28.83% to 27.26%, when nitrogen flow rate was increased from 100 cm3/min to 200 cm3/min and then increased to its maximum value of 29.68% at 300 cm3/min flow rate. As for bio-char yield, it decreased to its minimum value of 25.87% as nitrogen flow rate was increased from 100 cm3/min to 200 cm3/min and then decreased to its maximum value of 27.76% at 300 cm3/min flow rate. Ignoring the small differences in the values obtained in our study from previous studies, similar results have been reported in the literature [17,21,24,52,53] regarding the effect of sweeping gas on pyrolysis products yields.

Fig. 16. GCeMS spectrums of bio-oils obtained at 400
C.

1018

T. Aysu, M.M. Küçük / Energy 64 (2014) 1002e1025

According to the reports in literature, the role of sweeping gas is to minimize the secondary reactions including thermal cracking, repolymerisation and recondensation by removing the form the formed products from the hot zone and hence to maximize the liquid product yield. The reason for decrease in liquid product yields and increase in gaseous product yields at higher flow rates is because of either poor cooling or fast leaving of pyrolysis vapours before condensation [17,21,24,54,55]. 3.5. Characterization of bio-chars and bio-oils by elemental, FT-IR and GCeMS analysis Out of sixty one products, some of the selected bio-chars and bio-oils obtained at various conditions were analyzed and characterized by chromatographic and spectroscopic techniques such as

elemental, FT-IR and GCeMS. All analyses were carried out at scientific and technological research center in Malatya Inonu University. Elemental analyses were performed with LECO CHNS 932 Elemental Analyser and infrared analysis with a Perkin Elmer Spectrophotometer. The GCeMS analyses were performed on Agilent GCeMS 7890A/5975C series. The column (HP-INNOWAX, length: 60 m, I.D.: 0.250 mm, film: 0.25 mm and temperature limits: from 40
C to 260
C) and injector temperatures were the same as those for GC. Chemical constituents were identified by comparison of their retention indices with literature values [56,57] and their mass spectral data with those from the Wiley7n.1, ADAMS.1 and NIST05a.L mass spectral databases. The results of elemental analyses of five bio-chars and nine biooils are given in Tables 5 and 6 respectively. Tables 5 and 6 show that both bio-chars and bio-oils have higher carbon contents and

Fig. 17. GCeMS spectrums of bio-oils obtained at 350
C.

T. Aysu, M.M. Küçük / Energy 64 (2014) 1002e1025

1019

Table 7 Main chemical compounds present in the bio-oils obtained at 500
C. No

Compound types

Monoaromatics 1 Furfural 2 2-Furancarboxaldehyde, 5-methyl3 2-Acetylfuran 4 Furan, 2,3,5-trimethyl5 2 (3H)-Furanone, dihydro6 2-Furanmethanol 7 2 (5H)-Furanone, 3-methyl8 2 (5H)-Furanone 9 2 (3H)-Furanone 10 Guaiacol 11 Mequinol 12 Phenol, 2-methoxy-3-methyl13 Phenol, 2-methoxy-4-methyl14 Cresol 15 Phenol 16 p-Ethyl guaiacol 17 Benzeneethanol, 2-methoxy18 Phenol, 4-ethyl-2-methoxy19 Phenol, 2-ethyl20 Phenol, 2,5-dimethyl21 Phenol, 2,6-dimethyl22 Phenol, 2,4-dimethyl23 Phenol, 2,3-dimethyl24 Phenol, 3,4-dimethyl25 Phenol, 3,5-dimethyl26 Cresol 27 Cresol 28 Phenol, 3-ethyl29 p-Propylguaicol 30 2-Methoxy-4-vinylphenol 31 2,6-Xylenol 32 Phenol, 2,6-dimethoxy33 3-Allyl-6-methoxyphenol 34 Phenol, 2-methoxy-4-(1-propenyl)35 2, 3, 5-Trimethoxy toluene 36 Phenol, 2,6-dimethoxy-4-(2-propenyl)37 2,6-Dimethyl-3-(methoxymethyl)-p-benzoquinone 38 Cinnamic acid, 3-Hydroxy-4-methoxy39 Cinnamic acid, 4-Hydroxy-3-methoxy40 Phenol, 2-methoxy-5-(1-propenyl)-(E)41 Trans-5,8-Dioxatricyclo [5.1.0.0 (4,5)] oct-2-ene 42 2-Propanone, 1-hydroxy-3-(4-hydoxy-3-methoxyphenyl)43 1, 2-Benzenediol 44 2, 5-Dimethoxyterephthalic acid 45 Desaspidinol

Aliphatics 46 Pentane, 3-methyl47 1-Ethyl-4-methylcyclohexane

Oxygenated compounds 48 2-Cyclopenten-1-one, 2-methyl49 2-Cyclopenten-1-one 50 2-Decanone 51 Butanal, 3-methyl52 1-Hydroxy-2-butanone 53 Acetic acid 54 1-Penten-3-ol, 2-methyl55 1-Acetoxyacetone 56 Propanoic acid 57 2-Cyclopenten-1-one, 3-methyl58 2-Cyclopenten-1-one, 2,3-dimethyl59 Pentanoic acid 60 1-methoxy-1,3-cyclohexadiene 61 Butanoic acid 62 4-formyl-4-methyl-tetrahydropyran 63 2-Cyclopenten-1-one, 2-hydroxy-3-methyl-

Chemical formula

C5H4O2 C6H6O2 C6H6O2 C7H10O C4H6O2 C5H6O2 C5H6O2 C4H4O2 C4H4O2 C7H8O2 C7H8O2 C8H10O2 C8H10O2 C7H8O C6H6O C9H12O2 C9H12O2 C9H12O2 C8H10O C8H10O C8H10O C8H10O C8H10O C8H10O C8H10O C7H8O C7H8O C8H10O C10H14O2 C9H10O2 C8H10O C8H10O3 C10H12O2 C10H12O2 C10H14O3 C11H14O3 C10H12O3 C10H10O4 C10H10O4 C10H12O2 C6H6O2 C10H12O3 C6H6O2 C10H10O6 C11H14O4

C6H14 C9H18

C6H8O C5H6O C10H20O C5H10O C4H8O2 C2H4O2 C6H12O C5H8O3 C3H6O2 C6H8O C7H10O C5H10O2 C7H10O C4H8O2 C7H12O2 C6H8O2

Molecular weight

96.08 110.11 110.11 110.15 86.08 98.10 98.10 84.07 84.07 124.14 124.13 138.16 138.16 108.14 94.11 152.19 152.19 152.19 122.16 122.16 122.16 122.16 122.16 122.16 122.16 108.14 108.14 122.16 166.21 150.17 122.16 154.16 164.20 164.20 182.22 194.22 180.20 194.18 194.18 164.20 110.11 180.20 110.10 226.18 210.22

86.18 126.24

96.13 82.04 156.27 86.13 88.11 60.05 100.16 116.11 74.07 96.13 110.15 102.13 110.15 88.11 128.17 112.13

Relative abundance (% area) Without catalyst

With 15% Al2O3

With 15% ZnO

1.00 e 0.49 e e 2.09 e e e e 5.31 0.44 1.35 1.60 3.25 e e 2.08 0.91 0.71 1.80 0.63 e e e 1.16 2.11 e 0.57 3.87 0.90 15.64 e 5.86 5.61 1.24 6.52 1.35 e e e 1.32 3.35 6.27 2.70

3.36 1.23 1.08 e 1.44 4.87 0.36 1.13 e 8.14 e e 1.54 2.73 3.73 e 0.58 e 0.42 e 1.41 0.79 e 2.32 e 1.58 e 1.42 e 2.32 e 11.68 2.25 e e e 0.93 1.44 e e e e e e e

4.03 e 1.01 1.27 1.92 3.97 0.47 e 0.87 9.27 e e 0.64 3.02 6.75 0.68 e e 0.56 0.64 0.58 0.72 0.80 e 2.06 1.95 3.17 1.09 e 1.95 e 7.89 e e e e e e 1.27 1.54 1.69 e e e e

80.13

56.75

59.81

e e

e 0.49

1.56 e

e

0.49

1.56

0.55 e e e 0.91 3.27 e 0.30 1.12 0.87 0.71 e 0.50 0.50 e e

0.70 1.61 0.68 1.57 e 12.11 1.40 e 2.67 1.89 1.31 0.52 e e e e

1.56 1.83 e e e 20.33 1.44 e 2.53 1.52 1.36 e e 0.52 0.45 1.44 (continued on next page)

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T. Aysu, M.M. Küçük / Energy 64 (2014) 1002e1025

Table 7 (continued ) No

Compound types

Chemical formula

Molecular weight

Relative abundance (% area) Without catalyst

With 15% Al2O3

With 15% ZnO

64 65 66 67 68 69 70 71 72 73 74 75

Ethyl cyclopentenolone 2-Butenoic acid, 2-methyl-, E2-Butenoic acid, 3-methyl4-Hydroxy-6-methyl 2H-pyran-2-one 1,2-Cyclopentanedione, 3-methyl1,2-Cyclopentanedione 2-Cyclopenten-1-one, 3-ethyl-2-hydroxy4H-Pyran-4-one, 3-hydroxy-2-methyl3-Pentanone, 2,2-dimethylHexanal, 2-ethyl1,4:3,6-Dianhydro-.alpha.-d-glucopyranose n-Hexadecanoic acid

C7H10O2 C5H8O2 C5H8O2 C6H6O3 C6H8O2 C5H6O2 C7H10O2 C6H6O3 C7H14O C8H16O C6H8O4 C16H32O2

126.15 100.12 100.12 126.03 112.13 98.09 126.15 126.03 114.19 128.21 144.13 256.42

0.56 0.68 0.81 0.39 1.96 e 0.99 0.75 e e e 3.33

e e e e 1.98 0.89 e e e 5.51 1.06 e

e e e e e e e e 1.64 e e e

18.20

33.90

31.74

0.95 e 0.77 e

e 2.15 e e

2.32 e e 0.39

1.65

2.15

2.71

e e

e 1.06

0.37 0.93

e

1.06

1.30

99.98

94.35

97.12

Nitrogenated compounds 76 1H-Imidazole, 1-methyl77 N-Nitrosodimethylamine 78 Butyric acid hydrazide 79 2-Butanone, 4-(1-piperidinyl)-

Polyaromatic compounds 80 Naphthalene, 2-methyl81 1H-Inden-1-one, 2,3-dihydro-

C4H6N2 C2H6N2O C4H10N2O C9H17NO

C11H10 C9H8O

Total

lower oxygen content than the original raw material and accordingly have higher heating values when compared with higher heating value of the raw material. As shown in Tables 5 and 6, the higher heating values of bio-chars and bio-oils were higher than 20 MJ/kg, in comparison with the low higher heating value (16.16 MJ/kg) of the raw material. FT-IR spectrums of bio-chars obtained at 450 and 500
C. are given in Fig. 9. When they are compared with raw material, there have been significant changes in the FT-IR spectrum as a result of pyrolysis. The OeH stretching vibration band at 3335 cm1 has been almost disappeared for all bio-chars which shows that the oxygen was removed from raw material during pyrolysis which causes the phenolic and aromatic structures to crack producing carbonaceous solid products. The FT-IR spectrums of bio-chars are very similar to each other. The observed weak bands between 2500 cm1 and 2600 cm1 are assigned to aliphatic CeH stretching. The CeC stretching vibrations between 1350 and 1650 cm1 indicate the presence of aromatics and alkanes. The CeO stretching absorbance peaks observed between 1050 and 1350 cm1 indicate the presence of primary, secondary and tertiary alcohols, phenols, ethers and esters. FT-IR analyses prove that the bio-chars obtained by pyrolysis are mainly composed of aromatic and aliphatic compounds. FT-IR and GCeMS spectrums of twelve bio-oils (without and with catalyst) obtained at 500
C, 450
C, 400
C, 350
C which mostly represent the whole are given in Figs. 10e17. The list of the compounds identified by GCeMS in Figs. 14e17 is given in Tables 7e10 respectively. As expected, bio-oils produced by degradation of hemicellulose, cellulose and lignin of biomass contain many types of compounds having different molecular structures and molecular weights. Number and types of compounds obtained at higher temperatures are greater than at lower temperatures. That means that the degradation of lignin is not complete and continue as the temperature is further increased.

82.11 74.08 102.14 155.24

142.20 132.16

Bio-oils identified by GCeMS consist of complex mixtures of organic compounds These compounds can be grouped into four different classes of monoaromatics, aliphatics, oxygenated compounds, nitrogenated compounds, aromatic compounds and derivatives. Monoaromatics include benzene and derivatives, toluene, furans, phenols and derivatives. Aliphatics are mainly composed of alkanes, alkenes and their derivatives while oxygenated compounds contain aldehydes, ketones, esters and carboxylic acids. Amines and amides such as pyridine and pyrazole are classified as nitrogenated compounds. In accordance with the previous studies reported in literature [34,45,58e61] most of the identified compounds of bio-oils are phenolics and its derivatives are formed by degradation of lignin in the raw material. They consist of phenols, methoxy phenols, alkyl phenols and eugenol. As bio-oils obtained by pyrolysis can be used not only as a fuel in engines or boilers, but also as a valuable organic chemicals, phenols could be considered as one of them for its commercial value. Bio-oils are composed of mainly aldehydes, ketones and phenolic compounds. Most of these compounds are formed from the degradation of lignin and the others are from cellulose. The most abundant compounds in the bio-oils are acetic acid, 2,6-dimethoxy phenol, guaiacol, furfural and furan derivatives. During pyrolysis of woody biomass, hemicelluloses decompose first (200e280
C) forming the acidic compounds such as acetic acid. On the other hand, decomposition of cellulose (240e350
C) produces levoglucosan as the primary breakdown product during thermal treatment, but other anhydroglucoses, furan and furan derivatives are also produced. Phenols and derivatives such as 2,6-dimethoxy phenol and guaiacol, the majority of the compounds in bio-oils, are obviously the primary products of degradation of lignin (280e500
C) during pyrolysis [62]. The FT-IR spectrums confirm and are consistent with the list of compounds in Tables 7e10. Absorbance peaks of the OeH or NeH vibrations between 3100 and 3700 cm1 indicate the presence of

T. Aysu, M.M. Küçük / Energy 64 (2014) 1002e1025

1021

Table 8 Main chemical compounds present in the bio-oils obtained at 450
C. No

Compound types

Monoaromatics 1 Furfural 2 2-Acetylfuran 3 2-Furancarboxaldehyde, 5-methyl4 Furan, 2,5-dimethyl5 2-Furanmethanol 6 2 (5H)-Furanone 7 2 (3H)-Furanone 8 2 (3H)-Furanone, dihydro9 Furan, 2-methoxy10 Benzene, 1-fluoro-2-methoxy11 Guaiacol 12 1-ethoxy-2-methoxy-4-methylbenzene 13 Phenol, 2-methoxy-4-methyl14 Cresol 15 Phenol 16 Benzeneethanol, 2-methoxy17 Phenol, 4-methyl-2-methoxy18 Phenol, 2-ethyl19 Phenol, 2,6-dimethyl20 Phenol, 2,4-dimethyl21 Phenol, 4-ethyl-2-methoxy22 Cresol 23 Cresol 24 Phenol, 3,5-dimethyl25 Phenol, 2,3-dimethyl26 Phenol, 3,4-dimethyl27 Phenol, 3-ethyl28 Eugenol 29 2-Methoxy-4-vinylphenol 30 Phenol, 2,5-dimethyl31 Phenol, 2,6-dimethoxy32 2,3,5,6-Tetrafluoroanisole 33 Trans-5,8-Dioxatricyclo [5.1.0.0 (4,5)] oct-2-ene 34 Phenol, 2-methoxy-4-(1-propenyl)-(E)35 3-Furancarboxylic acid, 2,5-dimethyl-, methyl ester 36 2,6-Dimethyl-3-(methoxymethyl)-p-benzoquinone 37 Phenol, 2,6-dimethoxy-4-(2-propenyl)-

Aliphatics 38 3-Hexyne 39 3-Heptyne 40 3-Methyl pentane 41 Bicyclo [2.2.2] octane

Oxygenated compounds 42 2-Cyclopenten-1-one, 2-methyl43 2-Cyclopenten-1-one, 3-methyl44 1-Hydroxy-2-butanone 45 Acetic acid 46 1-Acetoxyacetone 47 1-Penten-3-ol, 2-methyl48 Propanoic acid 49 2-Cyclopenten-1-one, 2,3-dimethyl50 Butanoic acid 51 Ethylcyclopentenolone 52 2-Butenoic acid, 2-methyl-, (E)53 2-Butenoic acid, 3-methyl54 1,2-Cyclopentanedione, 3-methyl55 2-Cyclopenten-1-one, 2-hydroxy-3-methyl56 2-Cyclopenten-1-one, 3-ethyl-2-hydroxy57 4H-Pyran-4-one, 3-hydroxy-2-methyl58 3-Pentanone, 2,2-dimethyl59 2-Propenoic acid, 3-(4-hydroxy-3-methoxyphenyl)60 Cinnamic acid, 4-hydroxy-3-methoxy61 n-Hexadecanoic acid

Chemical formula

Molecular weight

Relative abundance (% area) Without catalyst

With 15% Al2O3

With 15% ZnO

C5H4O2 C6H6O2 C6H6O2 C6H8O C5H6O2 C4H4O2 C4H4O2 C4H6O2 C5H6O2 C7H7FO C7H8O2 C10H14O2 C8H10O2 C7H8O C6H6O C9H12O2 C8H10O2 C8H10O C8H10O C8H10O C9H12O2 C7H8O C7H8O C8H10O C8H10O C8H10O C8H10O C10H12O2 C9H10O2 C8H10O C8H10O3 C7H4OF4 C6H6O2 C10H12O2 C8H10O3 C10H12O3 C11H14O3

96.08 110.11 110.11 96.13 98.10 84.07 84.07 86.08 98.10 126.13 124.14 166.21 138.16 108.14 94.11 152.19 138.16 122.16 122.16 122.16 152.19 108.14 108.14 122.16 122.16 122.16 122.16 164.20 150.17 122.16 154.16 180.10 110.11 164.20 154.16 180.20 194.22

1.42 1.03 0.97 1.54 4.21 0.71 e e e 0.66 9.29 0.66 1.90 1.12 3.81 e e e e e 3.09 1.22 e e e e e 1.16 4.05 e 13.67 e e 4.58 4.04 4.34 4.52

1.79 1.16 e e 2.94 e 1.20 1.50 e e 7.95 e 1.03 3.47 7.23 e 1.07 1.05 1.11 1.14 e 2.36 3.75 e 1.00 3.21 1.66 3.05 2.25 1.29 16.59 1.27 3.68 e e e e

3.56 1.19 1.43 e 4.28 1.29 e 1.83 1.00 e 7.31 e 1.04 3.41 5.54 0.55 e e 0.93 1.04 e 1.90 3.73 3.43 e e 2.69 2.05 1.92 e 10.35 e e e e e e

67.99

72.75

60.47

e e e e

1.18 e 1.14 0.96

1.88 0.74 1.54 e

e

3.28

4.16

1.00 e 2.22 7.95 0.65 1.90 2.61 e 0.88 0.97 0.95 1.23 e 3.26 1.45 0.92 e e e 2.90

e 1.07 e 10.95 e 1.15 1.68 e e e e e 1.61 e e e e 1.72 e e

e 2.26 e 12.67 e 1.61 2.47 1.60 e e e e 2.36 e e e 5.12 2.81 1.19 e

28.89

18.18

C6H10 C7H12 C6H14 C8H14

C6H8O C6H8O C4H8O2 C2H4O2 C5H8O3 C6H12O C3H6O2 C7H10O C4H8O2 C7H10O2 C5H8O2 C5H8O2 C6H8O2 C6H8O2 C7H10O2 C6H6O3 C7H14O C10H10O4 C10H10O4 C16H32O2

82.14 96.17 86.18 110.19

96.13 96.13 88.11 60.05 116.11 100.16 74.07 110.15 88.11 126.15 100.12 100.12 112.13 112.13 126.15 126.03 114.19 194.18 194.18 256.42

31.09 (continued on next page)

1022

T. Aysu, M.M. Küçük / Energy 64 (2014) 1002e1025

Table 8 (continued ) No

Compound types

Nitrogenated compounds 62 1H-Pyrazole, 3-methyl63 N-Nitrosodimethylamine 64 2-Ethyl-5-(2-fluorobenzylideneamino)-1,3,4-thiadiazole 65 1H-Imidazole-2-carboxaldehyde, 1-methyl-

Polyaromatic compounds 66 1H-Inden-1-one, 2,3-dihydro-

Chemical formula

Molecular weight

Relative abundance (% area) Without catalyst

With 15% Al2O3

With 15% ZnO

C4H6N2 C2H6N2O C11H10FN3S C5H6N2O

82.10 74.08 235.28 110.11

1.97 e e 1.15

e 1.27 e e

e e 2.05 e

3.12

1.27

2.05

e

1.29

1.23

e

1.29

1.23

e

3.23

e

e

3.23

e

100

100

99.00

C9H8O

Other compounds 67 Triethylaluminum

C6H15Al

132.16

114.16

Total

Table 9 Main chemical compounds present in the bio-oils obtained at 400
C. No

Compound types

Monoaromatics 1 Benactyzine 2 Furfural 3 Ethanone, 1-(2-furanyl)4 2-Furancarboxaldehyde, 5-methyl5 Furan, 2,3,5-trimethyl6 p-Benzoquinone 7 2-Furanmethanol 8 2 (5H)-Furanone 9 2 (3H)-Furanone 10 2 (3H)-Furanone, dihydro11 4-Fluorophenol 12 Mequinol 13 Guaiacol 14 Cresol <2-methoxy-para> 15 Cresol 16 Phenol 17 Benzeneethanol, 2-methoxy18 Phenol, 2,6-dimethyl19 Phenol, 2,4-dimethyl20 Cresol 21 Cresol 22 Phenol, 2-ethyl23 Phenol, 3-ethyl24 2-Methoxy-4-vinylphenol 25 2-Pentanone, 4,4-dimethyl26 Phenol, 3,4-dimethyl27 Eugenol 28 Phenol, 2,6-dimethoxy-4-(2-propenyl)29 Phenol, 2,6-dimethoxy30 Phenol, 2-methoxy-4-(1-propenyl)-(E)31 Trans-5,8-Dioxatricyclo [5.1.0.0 (4,5)] oct-2-ene 32 5-formyl-2-furancarboxylic acid 33 1,2-diethoxybenzene 34 1,3-Isobenzofurandione

Aliphatics 35 Pentane, 3-methyl 36 2-Octene, (E)37 2-Octene, (Z)-

Chemical formula

C20H25NO3 C5H4O2 C6H6O2 C6H6O2 C7H10O C6H4O2 C5H6O2 C4H4O2 C4H4O2 C4H6O2 C6H5FO C7H8O2 C7H8O2 C8H10O2 C7H8O C6H6O C9H12O2 C8H10O C8H10O C7H8O C7H8O C8H10O C8H10O C9H10O2 C7H14O C8H10O C10H12O2 C11H14O3 C8H10O3 C10H12O2 C6H6O2 C6H4O4 C10H14O2 C8H4O3

C6H14 C8H16 C8H16

Molecular weight

327.41 96.08 110.11 110.11 110.15 108.09 98.10 84.07 84.07 86.08 112.10 124.13 124.14 138.16 108.14 94.11 152.19 122.16 122.16 108.14 108.14 122.16 122.16 150.17 114.19 122.16 164.20 194.22 154.16 164.20 110.11 140.09 166.22 148.11

86.18 112.21 112.21

Relative abundance (% area) Without catalyst

With 15% Al2O3

With 15% ZnO

0.97 2.26 1.16 e 1.05 5.25 2.56 e 1.28 2.10 1.21 6.76 e e 1.55 5.91 e e e 1.09 1.16 e e e 1.86 1.94 e 1.86 7.43 e e e e 0.19

e 2.68 e 1.21 e e 3.51 1.98 e 1.36 e e 7.19 1.02 2.91 5.70 1.76 1.70 1.76 1.65 2.83 2.56 1.69 2.16 e e e e 13.52 2.66 4.76 e e e

e e e e e e 2.55 e 0.90 e e e 7.75 e 1.90 6.25 0.70 e 0.70 1.80 2.35 2.05 3.55 1.80 7.00 e 4.50 2.90 21.00 e e 2.55 7.65 e

47.59

64.61

77.90

1.67 1.75 0.22

1.65 e e

e e e

3.64

1.65

e

T. Aysu, M.M. Küçük / Energy 64 (2014) 1002e1025

1023

Table 9 (continued ) No

Compound types

Oxygenated compounds 38 2-Cyclopenten-1-one 39 2-Cyclopenten-1-one, 2-methyl40 1-Hydroxy-2-pentanone 41 1-Penten-3-one, 2-methyl42 2-Cyclopenten-1-one, 3-methyl43 Propanoic acid 44 Acetic acid 45 2,3-Dimethyl-2-cyclopenten-1-one 46 Hexanal, 2-ethyl47 Bicyclo [3.3.0] oct-1 (2)-en-3-one48 1,4:3,6-Dianhydro-.alpha.-d-glucopyranose 49 2,5-Cyclohexadiene-1,4-dione 50 2-Cyclopenten-1-one, 2-hydroxy-3-methyl51 2-Propenoic acid, 3-(4-hydroxy-3-methoxyphenyl)52 4H-1-Benzopyran-4-one, 3,5,8-trimethoxy-2-methyl53 2-Pentadecanone

Nitrogenated compounds 54 N-Nitrosodimethylamine 55 Isopropyl,methoxy pyrazine

Polyaromatic compounds 56 1H-Inden-1-one, 2,3-dihydro57 Phenanthrene, 1,2-epoxy-1,2-dihydro-

Chemical formula

C5H6O C6H8O C5H10O2 C6H10O C6H8O C3H6O2 C2H4O2 C7H10O C8H16O C8H10O C6H8O4 C6H4O2 C6H8O2 C10H10O4 C13H14O5 C15H30O

Molecular weight

82.04 96.13 102.13 98.14 96.13 74.07 60.05 110.15 128.21 122.16 144.13 108.09 112.13 194.18 250.02 226.40

C2H6N2O C8H12N2O

74.08 152.19

C9H8O C14H10O

132.16 194.22

Total

Relative abundance (% area) Without catalyst

With 15% Al2O3

With 15% ZnO

2.37 0.85 e 2.41 1.90 3.77 22.36 1.40 e 1.13 e 6.10 e e 1.86 e

1.98 e e 1.04 1.02 1.98 14.09 e 5.59 e e e 1.74 2.62 e e

e e 1.65 e 1.05 1.90 5.95 e e e 2.55 e 1.65 e e 1.60

44.15

30.06

16.35

3.22 1.40

1.89 e

e e

4.62

1.89

e

e e

1.79 e

1.50 1.25

e

1.79

2.75

100

100

97

Table 10 Main chemical compounds present in the bio-oils obtained at 350
C. No

Compound types

Monoaromatics 1 Furfural 2 2 (3H)-Furanone, dihydro3 2-Furanmethanol 4 2 (5H)-Furanone 5 2 (3H)-Furanone6 Guaiacol 7 Cresol 8 Phenol 9 Phenol, 3,5-dimethyl10 Phenol, 2,4-dimethyl11 Cresol 12 Cresol 13 Phenol, 3,4-dimethyl14 Phenol, 3-ethyl15 Phenol, 4-ethyl16 2-Methoxy-4-vinylphenol 17 Guaiacol 18 Phenol, 2,6-dimethoxy19 Benzene, 1,4-dimethoxy20 Trans-5,8-Dioxatricyclo [5.1.0.0 (4,5)] oct-2-ene 21 1,2-Benzenedicarboxylic acid, dihexyl ester 22 1,3-Isobenzofurandione

Aliphatics 23 2,4-Dimethyl-1-heptene

Chemical formula

Molecular weight

Relative abundance (% area) Without catalyst

With 15% Al2O3

With 15% ZnO

C5H4O2 C4H6O2 C5H6O2 C4H4O2 C4H4O2 C7H8O2 C7H8O C6H6O C8H10O C8H10O C7H8O C7H8O C8H10O C8H10O C8H10O C9H10O2 C7H8O2 C8H10O3 C8H10O2 C6H6O2 C24H38O4 C8H4O3

96.08 86.08 98.10 84.07 84.07 124.14 108.14 94.11 122.16 122.16 108.14 108.14 122.16 122.16 122.16 150.17 124.14 154.16 138.16 110.11 390.55 148.11

2.61 1.48 3.46 1.29 e 5.46 4.29 7.97 1.49 1.29 3.29 6.12 4.29 2.42 e 1.49 e 12.93 e 4.17 e e

e e 3.31 1.78 e e 2.97 12.64 e e e 3.55 3.36 e 2.58 3.25 11.65 12.98 1.73 e e e

e 2.82 7.05 e 3.29 12.22 1.88 11.75 e e e e e e e 3.29 e 17.26 e 4.23 1.86 0.47

64.05

59.80

66.12

e

e

C9H18

126.24

1.88 (continued on next page)

1024

T. Aysu, M.M. Küçük / Energy 64 (2014) 1002e1025

Table 10 (continued ) No

Compound types

Chemical formula

Molecular weight

Relative abundance (% area) Without catalyst

With 15% Al2O3

With 15% ZnO

24 25 26

3-Methyl pentane 1-Pentene, 3-ethyl4-Undecen, 9-methyl-(Z)-

C6H14 C7H14 C12H24

86.18 98.19 168.29

1.50 e e

e e e

e 3.76 4.70

1.50

e

10.34

2.56 e e 19.64 3.22 4.92 e e e e e

e 1.65 e e 2.23 e e 14.98 e 2.48 2.06

e e 3.76 e e e 8.30 e 0.94

30.34

23.40

13.00

e e 1.65 2.46 e

1.32 e e e 5.45

3.29 2.35 e e e

4.11

5.45

5.64

e e e e

2.23 e 2.64 e

e 4.23 e 0.67

e

4.87

4.90

e e

1.78 3.38

e e

e

5.16

e

100

98.68

100

Oxygenated compounds 27 Lyxitol, 1-O-nonyl28 2H-Pyran, tetrahydro29 Heptane, 1,1-dimethoxy30 Acetic acid 31 Propanoic acid 32 3-Pentanone, 2,2-dimethyl33 2-Pentanone, 4,4-dimethyl34 3-Hexanone, 5-methyl35 2,5-Cyclohexadiene-1,4-dione 36 2-Decanone 37 1,4:3,6-Dianhydro-.alpha.-d-glucopyranose

Nitrogenated compounds 38 Hydrazine, 1,1-dimethyl39 1H-Pyrazole-4-carboxylic acid, 3-methyl40 Maleic hydrazide 41 Benzothiazole, 2-amino-6-methyl42 2-Propenamide, N-(4-aminobutyl)-3-(3,4-dihydroxyphenyl)-, (E)-

Polyaromatic compounds 43 1H-Inden-1-one, 2,3-dihydro44 4 (3H)-Quinazolinone, 2-methyl-3-(2-methylphenyl)45 1H-Indole, 2-methyl-3-phenyl46 3-Benzyl-idene-6-methoxy-chroman-4-one

Other compounds 47 Selenium dioxide dimer 48 Stannane, butyltriethyl-

C14H30O5 C5H10O C9H20O2 C2H4O2 C3H6O2 C7H14O C7H14O C7H14O C6H4O2 C10H20O C6H8O4

C4H8N2 C5H6N2O2 C4H4N2O2 C8H8N2S C13H18N2O3

C9H8O C16H14N2O C15H13N C17H14O3

O2S C10H24Sn

Total

the abundant compounds of phenols and alcohols and the absorbance peaks of CeH and ]CeH vibrations between 2900 and 3000 cm1 show the presence of alkanes and alkenes. The typical carbonyl group (C]O) stretching vibrations at about 1710 cm1 in bio-oils show that aldehydes, ketones or carboxylic acids were produced by degradation of raw material. The C]C stretching vibrations at about 1608 cm1 in bio-oils prove the presence of alkenes. Presence of alcohols and esters could be confirmed by CeH bending vibrations between 880 and 1300 cm1 and CeO stretching vibrations between 1200 and 1300 cm1 in bio-oils. Aromatic compounds are confirmed by the aromatic C]C stretching vibrations between 1450 and 1550 cm1. Benzene derivatives and phenol compounds are thought to be formed from decomposition of lignin. On the other hand, the decomposition of hemicellulose and cellulose produces mainly alkanes, aldehydes, alcohols, carboxylic acids, furan and its derivatives.

278.38 86.13 160.25 60.05 74.07 114.19 114.19 114.19 108.09 156.27 144.13

60.10 126.11 112.09 164.23 250.29

132.16 250.29 207.27 266.28

110.95 263.00

e

optimum condition for bio-oil formation is at 500
C with a heating rate of 50
C/min in the non-catalytic runs. The effects of different catalysts on degradation of F. orientalis L. were also investigated and types of catalysts have changed both product distribution and selectivity. Zinc oxide was found to be more effective than aluminium oxide in terms of bio-oil formation. Besides, the effects of particle size and sweeping gas flow rate on product yields were also determined under the optimum temperature and heating rate conditions. The composition of the bio-oils was characterized by chromatographic and spectroscopic techniques as well as the calorific values of bio-chars and bio-oils. It was found that pyrolysis oil is a complex mixture of aromatic, oxygenated, and nitrogenated organic compounds. The obtained bio-oils have higher heating values than the raw material. The GCeMS results of bio-oils indicate that the pyrolysis of F. orientalis L. is a promising process for both renewable fuel production and chemical feedstock. However, more trials with different catalysts should be performed in a pilot scale plant.

4. Conclusion Acknowledgements In this study, pyrolysis of a specific biomass (F. orientalis L.) was performed to obtain solid (bio-char) and liquid (bio-oil) products under different heating rate conditions at temperatures ranging from 350 to 600
C with and without catalyst. It was found that the

This study was supported by Yuzuncu Yil University Research Fund, and we gratefully acknowledge the financial support of this study (no: 2013-FBE-D004).

T. Aysu, M.M. Küçük / Energy 64 (2014) 1002e1025

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