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Fuel Processing Technolo
Bio-oil from olive oil industry wastes: Pyrolysis of olive residue under
different conditions
Ayse E. Putun a, Basak Burcu Uzun a, Esin Apaydin a, Ersan Putun b,*
a Department of Chemical Engineering, Anadolu University, 26470 Eskisehir, Turkeyb Department of Material Science and Engineering, Anadolu University, 26470 Eskisehir, Turkey
Received 13 January 2005; received in revised form 21 April 2005; accepted 21 April 2005
Abstract
Olive residues were pyrolysed 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 product composition with a heating rate of 7 -C/min. Final temperature range
studied was between 400 and 700 -C and the highest liquid product yield was obtained at 500 -C. Liquid product yield increased significantly
under nitrogen and steam atmospheres. Liquid products obtained under the most suitable conditions were characterised by elemental analyses, FT-
IR and 1H-NMR. In addition, column chromatography was employed and the yields of the sub-fractions were calculated. Gas chromatography was
achieved on n-pentane fractions. The results show that it is possible to obtain liquid products similar to petroleum from olive residue if the
pyrolysis conditions are chosen accordingly.
D 2005 Elsevier B.V. All rights reserved.
Keywords: Olive residue; Biomass pyrolysis; Characterisation
1. Introduction
Renewable energy sources hold promise for the future in
both industrialised and developing countries. Although in most
cases the renewables are still unable to compete with
conventional energies, several types of renewable energies
are destined to play an important role in future systems.
Biomass for producing energy has a special place among all
other renewable energy sources and it is estimated to contribute
with 10–14% to the world’s total energy supply. Biomass
energy can be used to generate electricity, heat, or economi-
cally competitive liquid transportation fuels for motor vehicles
[1–3].
The conversion of biomass into useful forms of energy can
be achieved in a number of ways. Pyrolysis has received
special attention since it produces solid, liquid and gas
products, yields of each depending on the conditions [1,2,4].
Solid product, char, can be used as a fuel either directly as
0378-3820/$ - see front matter D 2005 Elsevier B.V. All rights reserved.
doi:10.1016/j.fuproc.2005.04.003
* Corresponding author. Tel.: +90 222 33350580/6351; fax: +90 222
3239501.
E-mail address: [email protected] (E. Putun).
briquettes or as char–oil or char–water slurries or it can be
used as feedstocks to prepare activated carbons [5,6]. The
liquid product, bio-oil, is also useful as a fuel, may be added to
petroleum refinery feedstocks or upgraded by catalysts to
produce premium grade refined fuels, or may have a potential
use as chemical feedstocks. The third product gas having a high
calorific value may also be used as a fuel [1,6,7]. There are a
number of benefits to produce and use bio-oils. The most
important one is that bio-oils produce fewer harmful emissions
such as SOx, NOx gases during production and combustion and
they contribute virtually no CO2 to the atmosphere which
accelerates the greenhouse effect [6,8,9].
Many research studies on the potential recovery of fuels and
chemicals from biomass via pyrolysis in relation to process
conditions have been investigated. Cottonseed cake was taken
as the biomass sample by Ozbay et al. [10] to determine the
effects of reactor geometry, pyrolysis atmosphere and pyrolysis
temperature on the product yields and chemical composition of
the liquid product. The maximum oil yield was attained under
nitrogen atmosphere at a pyrolysis temperature of 550 -C with
a heating rate of 7 -C/min in tubular reactor. The effect of water
vapor on the structure of the products from pyrolysis of
cottonseed cake was also investigated [11]. It was found that
gy 87 (2005) 25 – 32
www.else
Biomass
Pyrolysis
Normal Atmosphere Sweeping Gas Atmosphere Steam Atmosphere
CharLiquidCharLiquidCharLiquidElemental analysis Elemental analysis Elemental analysis
Liquid Product (bio-oil) 1H-NMR
Pentane solubles(Maltenes)
Pentane insolubles(Asphaltenes)
Pentane EluateAliphatics
Toluene EluateAromatics
Methanol EluatePolars
FT-IRElemental Analysis
FT-IRElemental Analysis
FT-IR, GC-MSElemental Analysis
Column Chromatography
Fig. 1. Flow scheme of pyrolysis studies and characterisation of the products
A.E. Putun et al. / Fuel Processing Technology 87 (2005) 25–3226
liquid product yields from steam atmosphere were higher than
that of static atmosphere. Pyrolysis of olive residues (cuttings
and kernels) in a captive sample reactor at atmospheric pressure
under helium with a heating rate of 200 -C/s to a temperature
range from 300 to 600 -C has been carried out by Zabaniotou
et al. [12] to determine the yields of products in relation to
pyrolysis temperature. Their results showed that as the final
temperature increased the percentage of liquid and gaseous
products increased and oil products reached a maximum value
of ¨30% of dry biomass at about 450–550 -C. Minkova et al.
[13] have studied the pyrolysis of different biomass samples in
a fixed bed reactor under a flow of steam to the final
temperatures of 700–800 -C. Their results indicated that the
presence of steam has strong effect on the yield and properties
of products.
In this study, olive residue generated by the industrial
processing of olive fruit is taken as the biomass sample for
pyrolysis experiments. In Mediterranean basin countries, Italy,
Greece, Spain, Portugal and Turkey, olive (Olea Europea L.)
cultivation is a typical activity. The worldwide olive production
was 13,741,161 Mt in 2000 with 97% of the total production
provided by the Mediterranean area; Turkey alone produced
approximately 1,800,000 tons of olive in the year 2000 [14,15].
It is possible to recover 15–22 kg olive oil and 35–45 kg olive
residue from 100 kg of olive. Although Turkey has a potential
of producing 505,500 tons/year of olive residue, the mean
amount of the residue is varying from 128,320 tons/year to
360,000 tons/year, according to the fruitfulness of the year.
Having low content of sulfur (0.05–0.1%) and ash (2–3%),
olive residue is a clean and renewable energy source [16].
These by-products with a high content of lignocellulosic
material from olive plantations are currently used as raw
materials for energy production and have been recently
employed to produce bio-oils, gaseous products and solid
products as activated carbons [12,16].
This present work focuses on two aspects on olive residue
pyrolysis: (i) effect of pyrolysis conditions on the product
yields; (ii) liquid product characterisation.
2. Method
2.1. Raw material
Olive residue samples which have been taken from some
olive oil factories around Ayvalik, Balikesir located in Western
Anatolia were used as the raw material for the pyrolysis
Table 1
Properties of olive residue
Proximate analysis
(wt.%)
Component analysis
(wt.%)
Elemental analysis
(daf a )
Moisture 10.6 Cellulose 56.0 Carbon 44.82
Volatiles 70.4 Oil 4.7 Hydrogen 5.08
Ash 3.7 Protein 4.25 Nitrogen 0.92
Fixed carbon 15.3 – – Oxygenb 49.18
a Dry, ash-free basis.b By difference.
.
experiments. Air-dried olive residues were ground to obtain a
uniform material of an average particle size (1.29 mm). The
average bulk density of this raw material was found to be 700
kg/m3 using ASTM methods.
Proximate analyses of the raw material having average
particle size were performed according to The Standard
Methods of the American Society for Testing and Materials
(ASTM) procedure (Table 1).
Ultimate analyses were performed on olive residue samples
to determine the elemental composition. A Carlo Erba, EA
1108 Elemental Analyser was used to determine the weight
fractions of carbon, hydrogen and nitrogen, and the weight
fraction of oxygen was calculated by the difference (Table 1).
H/C and O/C ratios of olive residue were found to be 1.32 and
0.62, respectively. Calorific value of olive residue was
calculated as 17.7 MJ/kg with Du-Long’s formula with the
known values of elemental composition [17].
Cellulose, oil and protein, being the main constituents of
olive residue, were also determined. Protein content was
determined by the Kjeldahl method using Labconco Rapid
still-2 and N�6.25 as the conversion factor.
Fig. 1 shows the flow scheme of the experimental studies
for both laboratory work and instrumental analyses.
2.2. Pyrolysis experiments
Pyrolysis experiments were performed in a 316 stainless
steel fixed-bed reactor having a volume of 400 cm3 (70 mm
ID). It is heated externally by an electrical furnace and the
temperature is measured by a thermocouple inside the bed. The
connecting pipe between the reactor and the trapping system
was heated to 400 -C to avoid condensation of tar vapour.
Pyrolysis runs were carried out with 10 g sample of olive
residue with a heating rate of 7 -C/min. Pyrolysis product
15
20
25
30
35
300 400 500 600 700
Pyrolysis Temperature (oC)
Char yield
Bio-oilyield
Fig. 2. Pyrolysis of olive residue at different temperatures, product yields.
20
25
30
35
40
45
0.6 1.3 2.7
Steam velocity (cm/min)
Char yieldBio-oil
Fig. 4. Pyrolysis of olive residue at different steam velocities, product yields.
Table 2
Elemental compositions and calorific values of bio-oils obtained under different
A.E. Putun et al. / Fuel Processing Technology 87 (2005) 25–32 27
yields were determined gravimetrically by weighing the three
products. After reaching the final pyrolysis temperature the
reactor was set to cool to room temperature. Solid product,
char, was removed and weighed. The liquid phase was
collected in cold traps maintained at about 0 -C using salty
ice. The liquid phase consisted of aqueous and oil phases were
separated and weighed. The flow of gas released was
controlled using a soap film for the duration of experiments.
The gas yield was calculated by the difference.
Pyrolysis of olive residue was carried out in three groups of
experiments to investigate the effect of pyrolysis conditions on
the product yields and liquid product composition and to
determine the pyrolysis condition that gives the maximum bio-
oil yield. For the experiments, 10 g sample of olive residue was
placed into the reactor and the experiments were carried out with
a heating rate of 7 -C/min to the final temperature and held for
either a minimum of 30 min or until no further significant release
of gas was observed. For the first group of experiments, final
temperatures of 400, 500, 550 and 700 -Cwere carried out under
normal atmosphere. Nitrogen gas was used as the sweeping gas
with the flow rates of 50, 100, 200 and 200 cm3/min for the
second group experiments to determine the effect of sweeping
gas flow rate. The third group of experiments were performed to
establish the effect of water vapour velocity on the pyrolysis
yields. The experiments were conducted at water vapour
velocities of either 0.6, 1.3 or 2.7 cm/s. For all the experiments
under sweeping gas and steam atmospheres the heating rate and
the final pyrolysis temperature were 7 -C/min and 500 -C,respectively, basing on the first group of experiments.
All the yields are expressed on a dry, ash-free basis and were
the average yield of at least three pyrolysis experimental results
with a measurement error of less than T0.5%.
2.3. Bio-oil characterisation
The oils analysed in this study have been obtained under
experimental conditions that gave maximum oil yield.
15
20
25
30
35
40
0 100 200 300 400
Nitrogen flow rate (cm3/min)
Char yield
Bio-oilyield
Gas yield
Fig. 3. Pyrolysis of olive residue at different nitrogen flow rates, product yields.
Elemental analyses were carried out with Carlo Erba, EA
1108 and the calorific values were determined. For character-
isation of bio-oils, 1H-NMR spectra were recorded using a
BRUKER DPX-400, 400 MHz High Performance Digital FT-
NMR Instrument.
Chemical class compositions of the oils were determined by
liquid column chromatographic fractionation. Bio-oils were
separated into two fractions as asphaltenes and maltanes using
n-pentane as the solvent. Silica gel that was pre-treated at 105
-C for 2 h prior to use was the packing material. Pentane
soluble materials, maltenes, were further separated into
aliphatic, aromatic, ester and polar fractions using 200 ml of
pentane, toluene, ether and methanol, respectively. Each
fraction was dried and weighed.
The FT-IR spectra of the oils and their aliphatic and aromatic
subfractions were recorded using a Mattson 1000 Infrared
Spectrophotometer. GC/MS analyses of the aliphatic subfrac-
tions were performed using a Hewlett-Packard 6890 Model gas
chromatograph coupled with mass selective detector.
3. Results and discussion
3.1. Effect of pyrolysis temperature on product yields
Fig. 2 shows the product yields for the pyrolysis of olive
residue in relation to final temperature of pyrolysis at heating
rate of 7 -C/min. The yield of conversion increased from
67.6% to 72.5% while the final pyrolysis temperature was
increased from 400 -C to 700 -C. While the oil yield was
28.7% at the pyrolysis temperature of 400 -C, it appeared to go
through a maximum of 32.7% at the final temperature of
atmospheres at 500 -C
Component Normal (%) Sweeping gas (%) Steam (%)
C 67.9 68.13 76.09
H 8.7 9.00 10.32
N 1.7 1.34 0.70
Oa 21.7 21.53 12.88
H/C 1.54 1.58 1.63
O/C 0.24 0.24 0.13
Molar formula CH1.523N0.021O0.239 CH1.58N0.017O0.238 CH1.63N0.008O0.127
Calorific value
(MJ/kg)
31.6 32.14 38.31
a By difference.
(c)
(b)
(a)
ppm 8 6 4 2 0
Chemical Shift
Fig. 5. 1H-NMR spectra for bio-oils: (a) normal atmosphere; (b) sweeping gas
atmosphere; (c) steam atmosphere.
A.E. Putun et al. / Fuel Processing Technology 87 (2005) 25–3228
500 -C. Then at the final pyrolysis temperature of 700 -C, theoil yield decreased to 30.2%.
These results are consistent with literature. It is known that
pyrolysis temperature plays an important role on product
distribution. As olive oil residue reaches elevated temperatures,
the different chemical components undergo thermal degrada-
tion that affects the conversion yield and product quality. The
extent of the changes depends on the temperature and length of
pyrolysis time. At relatively lower temperatures, between 65
and 180 -C, olive oil residue loses its moisture, generates non-
combustible gases like CO2 and undergoes depolymerisation
Table 3
Results of 1H-NMR for the bio-oils from the pyrolysis of olive residue obtained un
Type of hydrogen Chemical shift
(ppm)
Bio
atm
Aromatic 9.0–6.5 8.
Phenolic (OH) or olefinic proton 6.5–5.0 4.
Hydroxyl groups or ring-joinmethylene
(Ar–CH2–Ar)
4.5–3.3 18.
CH3ICH2 and CH a to an aromatic ring 3.3–2.0 19.
CH2 and CH h to an aromatic ring (napthenic) 2.0–1.6 9.
h-CH3, CH2 and CH g to an aromatic ring 1.6–1.0 23.
CH3 g or further from an aromatic ring 1.0–0.5 17.
reactions involving no significant carbohydrate loss. Chemical
bonds preconditioned in the main constituents of biomass
sample begin to break at temperatures higher than approxi-
mately 200 -C. Breakdown of hemicellulose, which is less
thermally stable constituent, takes place at lower temperatures
up to 300 -C forming gases like carbon monoxide and carbon
dioxide. At temperatures between 350 and 500 -C cellulose
breakdowns and lignin starts to decompose resulting in
charcoal, water and heavier tars. Between these temperatures,
tar also undergoes cracking to lighter gases and repolymerisa-
tion to char. At higher temperatures, gasification reactions take
place forming hydrogen enriched gaseous products and char
undergoes further degradation by being oxidized to CO2, CO
and H2O. According to these reactions it can be said that
relatively low pyrolysis temperatures around 400 -C favours
char formation. Temperatures up to 600 -C maximise the
production of bio-oils and temperatures above 700 -Cmaximise gaseous products while minimising char formation.
For different biomass samples, pyrolysis temperatures that have
given the highest liquid product yield were determined to be
the temperatures between 500 and 550 -C [1,6,7,10,12,18,19].
3.2. Effect of sweeping gas flow rate on product yields
The role of sweeping gas during pyrolysis is to affect the
residence time of the gas produced as a result of pyrolysis
reactions by removing the products from the hot zone to
minimise secondary reactions such as thermal cracking,
repolymerisation and recondensation and to maximise the liquid
yield. The product yields of pyrolysis in relation to the nitrogen
flow rate are given in Fig. 3 for the heating rate of 7 -C/min and
pyrolysis temperature of 500 -C. It was observed that pyrolysis
conversion has increased in small amounts and there was no
obvious influence on the yield of water and char as the rate of
nitrogen increased. Indeed, the highest bio-oil yield of 39% was
achieved with a nitrogen flow rate of 200 cm3/min.
3.3. Effect of steam velocity on product yields
The chemistry of biomass is very complicated. But generally
it is assumed that biomass has three major carbon containing
constituents: cellulose, hemicellulose and lignin. Previous
studies showed that while the first degradation of the carbon in
biomass starts at about 200 -C, volatiles start to be evolved
[19–21]. If steam is in the media as an oxidizing agent, it causes
der three atmospheres at 500 -C
-oil under normal
osphere (%)
Bio-oil under nitrogen
atmosphere (%)
Bio-oil under steam
atmosphere (%)
23 8.92 4.53
4 7.18 4.8
69 18.64 12.84
12 17.20 16.78
20 17.50 8.07
31 15.44 38.69
05 15.12 14.29
(c)
(b)
(a)Tra
nsm
ittan
ce
4000 3500 3000 2500 2000 1500 1000 500
Wavenumbers
Fig. 6. FT-IR spectra of (a) bio-oil under normal atmosphere, (b) its aliphatic
subfraction, and (c) its aromatic subfraction.
Table 4
Results of the column chromatography for the three bio-oils
Bio-oil Pentane solubles Subfractions (wt.%)
Aliphatic Aromatic Polar
Normal 51.3 32.6 25.6 41.8
Nitrogen 55.9 34.5 27.5 38.0
Steam 68.4 41.0 22.4 36.6
A.E. Putun et al. / Fuel Processing Technology 87 (2005) 25–32 29
some reactions that are occurring on the surface of the biomass
sample and/or with the volatile products. Those parallel
reactions lead to a higher proportion of H2 formation. The
homolytic cleavage of a hydrogen molecule produces two
hydrogen free radicals. Free radicals are usually highly reactive
and unstable and often involved in chain reactions leading to a
formation of cracked molecules, which favors the production of
condensable gases forming light tars. Also, steam removes
carbon from the surface thus creating a char with a more porous
structure. In this manner, using steam as the oxidizing agent
increases formation of liquid products with decreasing char and
gas yields when compared with sweeping gas or static pyrolysis.
Previous studies on steam pyrolysis for different biomass
samples and oil shales show that water vapour strongly
influences the distribution of products and favors the formation
of liquid products at the expense of solid and gaseous products
[11,13,19,22,23]. Fig. 4 shows the product yields of olive
residue obtained in the presence of steam flowing at three
different velocities: 0.6, 1.3 and 2.7 cm/s. The results of the
experiments under steam atmosphere show that the oil yield of
steam pyrolysis is higher than that of normal and nitrogen
atmosphere pyrolysis. The conversion increased from 72.8% to
74.6% while water vapour velocity increased from 0.6 cm/s to
2.7 cm/s. Maximum oil yield was attained at the final pyrolysis
temperature of 500 -C and water vapour velocity of 1.3 cm/s as
42.12%.
3.4. Bio-oil characterisation
Previous studies have shown that biomass pyrolysis oils
contain a very wide range of complex organic chemicals
[10,11,19,22–24].
The elemental compositions, calorific values and the
average chemical compositions of the oils characterised under
normal, sweeping gas and steam atmospheres are listed in
Table 2. Heinze retort oil is characterised with a higher H/C
Table 5
Elemental compositions and calorific values of subfractions from column chromato
Component Normal (%) Sweeping ga
Aliphatic Aromatic Polar Aliphatic
C 82.22 74.33 65.49 82.25
H 12.43 9.89 9.33 13.47
N 0.11 0.28 2.12 0.08
Oa 5.24 15.5 23.06 3.20
H/C 1.81 1.596 1.71 1.94
Calorific value
(MJ/kg)
44.80 36.62 31.45 47.01
a By difference.
ratio than the olive residue and bio-oils under static atmosphere
and nitrogen atmosphere seem to have a lower H/C ratio than
the oil under steam atmosphere. The results show that water
vapour is a reactive agent that reacts with the pyrolysis
products. Water vapour may stabilise the radicals obtained in
the thermal decomposition of the fuel increasing the yield of
volatiles [12]. Further comparison of H/C ratios of pyrolysis
oils with conventional fuels indicates that the H/C ratios of the
oils obtained in this study lie between those of light and heavy
graphy for the bio-oils obtained at 500 -C
s (%) Steam (%)
Aromatic Polar Aliphatic Aromatic Polar
73.93 68.42 86.77 76.63 61.11
9.82 9.24 13.74 9.78 8.44
0.33 0.493 0.18 0.12 0.468
15.91 21.84 – 13.47 29.98
1.59 1.62 1.92 1.53 1.66
36.31 32.54 49.18 37.60 27.44
(c)
(b)
(a)
4000 3500 3000 2500 2000 1500 1000 500Wavenumbers
Fig. 7. FT-IR spectra of (a) bio-oil under sweeping gas atmosphere, (b) its
aliphatic subfraction, and (c) its aromatic subfraction.
(c)
(b)
(a)
4000 3500 3000 2500 2000 1500 1000 500
Wavenumbers
Fig. 8. FT-IR spectra of (a) bio-oil under steam atmosphere, (b) its aliphatic
subfraction, and (c) its aromatic subfraction.
A.E. Putun et al. / Fuel Processing Technology 87 (2005) 25–3230
petroleum products. Also, calorific values indicate that the
energy contents of the oils are very close to that of petroleum
[17].
Fig. 5 shows the 1H-NMR spectra of bio-oils obtained at
optimum conditions under static, sweeping gas and steam
atmospheres and Table 3 gives the results of the hydrogen
distribution. 1H-NMR spectra of the bio-oils indicate that the
aromaticity of the bio-oil from steam pyrolysis was lower than
the static atmosphere pyrolysis. CH2 and CH h to the aromatic
ring (naphthenic) protons have nearly the same value for static
atmosphere and steam atmosphere bio-oils. CH3 g or further
from the aromatic ring protons and CH3ICH2 and CH a to the
aromatic ring protons (centred at 2.65) are in close amounts for
the three oils. h-CH3, CH2 and CH g to the aromatic ring
protons are higher than the other protons for static and steam
oils and have the highest value for steam oil. The results show
that larger proportions of aliphatic structural units exist in the
bio-oil from steam pyrolysis.
The results of the column chromatography of the oils are
given in Table 4. Pyrolysis oils under normal and nitrogen gas
atmospheres consist of nearly the same amount of n-pentane
solubles and this value is significantly higher for steam bio-oil.
Weight percent of aliphatic subfraction for steam bio-oil is also
significantly higher than that of two other bio-oils due to the
restrictions to repolymerisation and recondensation. It can be
seen that the aromaticity of steam bio-oil is lower than the two
oils as shown in 1H-NMR spectra.
Elemental analyses were conducted to each subfraction and
the results are given in Table 5. Calorific values of aliphatic
subfractions are significantly higher than that of aromatic and
polar subfractions, and aliphatic subfraction from steam bio-oil
has the highest calorific value as expected. The carbon content
is also higher for aliphatic subfractions where oxygen content
decreases in negligible amounts. H/C ratios are also given in
Table 5; the ratios between 1.81 and 1.92 for the aliphatic
subfractions are nearly same for petroleum products.
FT-IR spectra of the oils under three atmospheres and their
corresponding aliphatic and aromatic subfractions are given in
Figs. 6–8. The O–H stretching vibrations between 3150 and
3400 cm�1 indicate the presence of phenols and alcohols.
m/e = 57Abundance
1000000
1200000
800000
600000
400000
200000
0Time→ 4.00 6.00 8.00 10.00 12.00 14.00 16.00 18.00 20.00 22.00 24.00 26.00 28.00 30.00
(c)m/e = 55
Abundance
50000
100000
150000
200000
300000
250000
A.E. Putun et al. / Fuel Processing Technology 87 (2005) 25–32 31
The figures show that no peaks exist between these wave
numbers for the aliphatic subfractions of the bio-oils and this
indicates that aliphatic subfractions do not contain oxygenated
compounds like bio-oils. The C–H stretching vibrations
between 2800 and 3000 cm�1 and C–H deformation
vibrations between 1350 and 1475 cm�1 indicate the presence
of alkanes. The CfH stretching vibrations with absorbance
between 1650 and 1750 cm�1 indicate the presence of
ketones or aldehydes. The absorbance peaks between 1575
and 1675 cm�1 represent CfC stretching vibrations indicative
of alkenes and aromatics.
A gas–liquid chromatogram of the aliphatic subfractions
of bio-oils obtained under static and water vapour atmo-
spheres and their selected ion current chromatograms for the
alkenes (m/e =55) and alkanes (m/e =57) are shown in Figs.
9 and 10. The straight chain alkanes and alkenes range
between C10–C29 for oil under static atmosphere and
between C10–C28 for oil under steam atmosphere. Distribu-
tion of straight chain alkanes exhibit a maximum on the
m/e = 57
m/e = 55
Abundance1000000
900000
800000
700000
600000
500000
400000
300000
200000
100000
0
Abundance220000
200000
180000
140000
160000
120000
100000
80000
60000
40000
20000
0
Abundance
1000000
1500000
2000000
2500000
3000000
3500000
4000000
5000000
5500000
4500000
500000
Time→ 5.00 10.00 15.00 20.00 25.00 30.00 35.00 40.00 45.00 50.00 55.00 60.00 65.00 70.00
(c)
Time→ 5.00 10.00 15.00 20.00 25.00 30.00 35.00 40.00 45.00 50.00 55.00 60.00 65.00 70.00
(b)
Time→ 5.00 10.00 15.00 20.00 25.00 30.00 35.00 40.00 45.00 50.00 55.00 60.00 65.00 70.00
(a)
C29
C14
C10
Fig. 9. GC/MS chromatogram of aliphatic subfraction of bio-oil under normal
atmosphere.
Time→ 4.00 6.00 8.00 10.00 12.00 14.00 16.00 18.00 20.00 22.00 24.00 26.00 28.00 30.00
(b)
Time→ 4.00 6.00 8.00 10.00 12.00 14.00 16.00 18.00 20.00 22.00 24.00 26.00 28.00 30.00
(a)
0
Abundance
1000000
2000000
3000000
4000000
5000000
6000000
7000000
0
C10
C13
C27
Fig. 10. GC/MS chromatogram of aliphatic subfraction of bio-oil under steam
atmosphere.
range of C10–C14 and C11–C13 for oils under static and
steam atmospheres, respectively. The results of this chro-
matogram have showed that aliphatic subfraction of the bio-
oil has a similar distribution of straight chain alkanes with
standard diesel.
Table 6 gives the results of elemental analyses of the
solid products obtained under optimum conditions. Carbon
Table 6
Elemental compositions and calorific values of the solid products obtained
under different atmospheres at 500 -C
Component Normal
atmosphere (%)
Sweeping gas
atmosphere (%)
Steam
atmosphere (%)
C 69.34 74.60 83.91
H 2.10 1.938 2.41
N 1.47 1.53 1.654
O 27.09 21.93 12.02
H/C 0.36 0.31 0.34
Molar formula CH0.36N0.018O2.92 CH0.31N0.018O0.22 CH0.34N0.0169O0.108
Calorific value
(MJ/kg)
21.60 24.75 29.69
A.E. Putun et al. / Fuel Processing Technology 87 (2005) 25–3232
content and calorific values are the important parameters for
chars when they are used as either activated carbons or solid
fuels. Indeed, slow pyrolysis seems to be a suitable way
when high yields of the carbon-enriched solid product (char)
are required. Char can be directly used as a fuel or
submitted to further processing to produce more value-
added chemicals, such as activated carbons. It can be seen
from the table that char obtained under steam atmosphere is
more useful for these purposes since its calorific value is
higher than that of the two other chars. The char can also
be used as a fuel when mixed with the liquid product
[1,5,25].
4. Conclusions
This study deals with the fixed-bed pyrolysis of a biomass
sample, olive residue, under different atmospheres in order to
obtain synthetic liquid fuels. The experimental studies showed
that pyrolysis temperature and atmosphere have important roles
on the bio-oil yield and composition.
As it is consistent with the literature, final temperature of the
pyrolysis reactions has a great influence on the product yields.
The oil yield was found to be 27.26% at a final pyrolysis
temperature of 500 -C with a heating rate of 7 -C/min.
Bio-oil yield increased by 19.13 wt.% when nitrogen with a
flow rate of 100 cm3/min was used as the inert gas to sweep the
products from hot zone.
It is known that the presence of steam increases the oil
yields significantly while char and gas product yields decrease.
The maximum bio-oil yield, 42.12%, was reached under steam
atmosphere when steam velocity was 1.3 cm/s.
Bio-oils obtained under optimum conditions were then
fractionated into chemical classes by column chromatography
and the oil and the subfractions analysed by elemental analyzer,1H NMR, FT-IR and GC/MS. The results of the instrumental
analyses are in consistency with chromatography, confirming
that aromaticity of bio-oil under steam atmosphere is signifi-
cantly lower than that of the bio-oils under normal and nitrogen
atmospheres. GC/MS and FT-IR results show that aliphatic
subfractions are a mixture of alkanes and alkenes. H/C ratios and
characterisation of the oils confirm that the aliphatic subfractions
are similar to the currently utilised transport fuels.
Acknowledgments
The authors are grateful to ‘‘Anadolu University Scien-
tific Research Projects Council’’ for the financial support of
this work through the project 010213.
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