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Pyrolysis analysis of different Cuban natural fibres by TGAand GC/FTIR

A. Gonzalez a, M. Penedo b, E. Mauris b, M.J. Fernandez-Berridi a,*, L. Irusta a, J. Iruin a

aDepartment of Polymer Science and Technology, University of the Basque Country. P.O. Box 1072, 20080 San Sebastian, SpainbDepartment of Chemical Engineering, University of Oriente, Santiago of Cuba, Cuba

a r t i c l e i n f o

Article history:

Received 12 September 2007

Received in revised form

25 May 2010

Accepted 3 June 2010

Keywords:

Cuban biomass pyrolysis

Saccharum officinarum

Coffea arabica L

Coffea canephora

Nicotiana tabacum

Pinus cubensis

* Corresponding author. Tel.: þ34 94301819E-mail address: mj.fernandezberridi@ehu

0961-9534/$ e see front matter ª 2010 Elsevdoi:10.1016/j.biombioe.2010.06.004

a b s t r a c t

In this work, the pyrolysis of different Cuban biomass such as: sugar cane bagasse, coffee,

residue of tobacco and sawdust of pine has been studied. The pyrolysis was carried out at

different temperatures in a small furnace placed at the injection port of a gas chromato-

graph coupled to a Fourier transform infrared spectrometer (Py-GC/FTIR). Thermogravi-

metric analysis (TGA) was also carried out using a thermobalance. For tobacco residue,

pyrolysis yield of charcoal and liquid products decreases with pyrolysis temperature

(300e600 �C). When the pyrolysis is carried out at 300 �C charcoal yield is similar for

tobacco residue, sawdust of pine and husk of coffee (z40%) while for husk of coffee and

sugar cane bagasse the charcoal yield is lower but the yield of the liquid product is higher.

ª 2010 Elsevier Ltd. All rights reserved.

1. Introduction Pyrolysis plays an important role in the biomass trans-

Fast biomass pyrolysis is of rapidly growing interest in the

world as it offers significant economic advantages over

thermal conversion processes [1,2]. A renewed emphasis is

expected, especially in underdeveloped countries as Cuba, on

the production of chemicals and liquid products from

biomass, the use of agricultural wastes as feedstock and the

co-firing of coal and biomass materials.

In Cuba, direct applications of pyrolysis liquid products

have been obtained for the formulation of soaps used to

emulsify fuels [3,4]. Thus, using pyrolysis products water/

petroleum emulsions have been successfully stabilized.

Moreover, pyrolysis products can be used as emulsifiers in the

copper flotation process [5e7]. This application is at the

moment under study.

4; fax: þ34 943015270..es (M.J. Fernandez-Berriier Ltd. All rights reserved

formation process, so the knowledge of the mechanism is

crucial to predict the pyrolysis yield and composition as

a function of feedstock characteristics and process

conditions.

The pyrolysis liquid products are extremely complex and

may be composed of hundreds of organic compounds. The

main components of this pyrolysis fraction include acids,

phenols, ketones, aldehydes, ethers and some species of

aromatics. Different instrumentation can be used to study the

pyrolysis products of natural wastes. In literature, pyrolysis-

gas chromatography-mass spectroscopy has been success-

fully used to study the pyrolysis of cotton [8], pine wood [9],

paper [10] and others [11,12]. Pyrolysis products have also

been studied by thermogravimetry coupled with Fourier

Transform infrared spectroscopy [13e16].

di)..

b i om a s s an d b i o e n e r g y 3 4 ( 2 0 1 0 ) 1 5 7 3e1 5 7 71574

In this work, pyrolysis of different Cuban biomass was

carried out at different temperatures in an oven coupled to

a gas chromatograph, using an infrared detector (PyeGC/IR)

[17]. Thermogravimetric analysis (TGA) was also carried out

using a thermobalance. Pyrolysis yield and nature of themain

products as a function of the biomass and pyrolysis temper-

ature are discussed.

Fig. 1 e Thermogravimetric analysis of different biomass.

2. Materials and methods

2.1. Samples

The Biomass samples used as feedstock for experimental

runs were bagasse from the sugar cane industry, coffee 1

and coffee 2, residue of tobacco and sawdust of pine. The

sugar cane bagasse (Saccharum officinarum), was supplied by

the “Dos Rios” agroindustrial complex, located in Palma de

Soriano (20�2100700N75�9801400W), Santiago de Cuba. The

product was harvested and processed during the season

2006. The coffee-roasting factory of Santiago de Cuba

supplied the husk of coffee. The husk of Coffee 1 came from

Arabic coffee (Coffea Arabica L) before roasting and the husk

of coffee 2 came from a 70/30 wt. % mixture of Arabic and

Robusta (Coffea canephora) coffee after roasting. The

residue of tobacco (Nicotiana tabacum) was supplied by the

tobacco company “Empresa del tabaco de Santiago de

Cuba”, and is the residue of the dried tobacco leaves rejec-

ted in the tobacco elaboration process. Finally, the sawdust

of pine (Pinus cubensis), after eliminating the bark, was

collected in the sawmill of “Gran Piedra Baconao”

(20�0800500N75�5501600W) in Santiago de Cuba. All the samples

were sieved (<2.83 mm particle size) and dried at 110 �C for

2 h before use.

Fig. 2 e Residue percentage of tobacco as a function of

pyrolysis temperature.

2.2. Methods

2.2.1. Pyroysis/GC/FTIR equipmentPyrolysis was performed by depositing an amount of about

40 mg of the biomass onto a semi-continuous furnace pyrol-

ysis unit (Pyrojector SGE, Konik) coupled to a gas chromato-

graph (GC-14A Shimadzu) injector unit. An on line infrared

spectrometer (Magna 560, Nicolet) was used to characterise

gas chromatographic peaks.

The pyrolysis chamber was set at the head of the injector,

at different pyrolysis temperatures in the range of 300e600 �C.The pyrolysis chamber pressure was 180 kPa.

The chromatographic column was an Agilent 30 m DB-

waxetr capillary column of 0.53 mm internal diameter. The

temperatures of the injector, detector and transfer-line units

were set at 200 �C, and the following temperature program

was used for the GC oven: Isothermal at 38 �C for 10min, a first

temperature ramp (5 �C min�1) to 100 �C where it was main-

tained for 5 min, a second temperature ramp at 10 �Cmin�1 to

220 �C where it was kept for 21 min. Nitrogen was used as

carrier gas at a pressure of 177 kPa.

Aldrich vapour phase FTIR library was used to identify the

infrared spectra of the main pyrolysis products.

2.2.2. Thermogravimetric analysis (TGA)Thermogravimetric analysis (TGA) was performed in a TGAQ-

500 thermobalance, with a standard furnace coupling and

nitrogen flow of 50 cm3 min�1. Sample weight was approxi-

mately 15 mg. The Hi-Res method at 4 resolution (Res.) was

used to obtain the thermograms. According to this method,

the heating rate is kept constant (40 �C min�1) when the

derivative of the weight change is zero and is decreased down

to 0.001 �C min�1 when the derivative increases.

3. Results and discussion

All the samples were analyzed using a thermobalance from

room temperature to 600 �C under nitrogen, and the results

are displayed in Fig. 1. As can be seen, all the fibres start losing

weight at about 200 �C and their degradation behaviour is

Fig. 3 e Gram-Schmidt chromatograms of tobacco residue obtained at 300, 400, 500, and 600 �C pyrolysis temperatures.

b i om a s s a n d b i o e n e r g y 3 4 ( 2 0 1 0 ) 1 5 7 3e1 5 7 7 1575

a complex process where at least three different steps are

detected. However, the char yield varies from one sample to

another, the sugar cane bagasse being the one that gives the

lower content.

Tobacco residue was pyrolyzed at 300, 400, 500 and 600 �Cand the residual solid content was quantified gravimetrically.

The results of this calculation are shown in Fig. 2. As can be

seen, the yield of residual solid has a declining trend as

pyrolysis temperature increases from 300 to 600 �C.The volatile products at these pyrolysis temperatures were

analysed by GC/FTIR and Fig. 3 shows the corresponding

chromatograms, where all peaks have been identified by their

infrared spectra with the help of the computer library.

As can be seen, the pyrolysis products are very complex.

The main components include carbon dioxide, methane,

Table 1 e Chromatographic relative area of eachcomponent obtained in the tobacco pyrolysis at differenttemperatures.

Compound Relative area of identified components (%)

300 �C 400 �C 500 �C 600 �C

CO2

Acetaldehyde

Methane

Ammonium

33 45 46 55

Water 0.6 3.3 5.4 5.1

Acetol 1.1 1.3 1.4 0.8

Acetic acid 11.0 9.0 8.0 7.0

Formic acid 3.4 2.0 0.7 0.7

Nicotine 1.4 1.5 1.6 1.2

Others 6.5 5.0 5.2 3.9

aldehydes, acetic and formic acids, some nitrogenated

compounds (acetamide, formamide, propionamide, pyrrolidi-

none and nicotine), phenol, ketones and esters, which are in

accordance with those reported in literature [13,18].

The area of each chromatographic peak has been used to

perform a semi quantitative analysis. The char content,

obtained by gravimetricmethods, has been taken into account

in order to calculate the percentage of each component at all

the temperatures. The percentage of gaseous products has

been calculated as a whole as they appear under the same

chromatographic peak. In addition under the nameof “others”

all minor contributions, whose retention time are between 30

Fig. 4 e Yields of the tobacco pyrolysis products at different

temperatures.

Fig. 5 e Gram-Schmidt Chromatograms obtained for different biomass at 300 �C.

b i om a s s an d b i o e n e r g y 3 4 ( 2 0 1 0 ) 1 5 7 3e1 5 7 71576

and 40 min have also been grouped. Table 1 summarizes the

obtained results. As can be observed, the percent of products

of low molecular weight (gases) and water increases with

pyrolysis temperature, meanwhile the yield of the rest of the

products decreases with temperature.

The compounds of Table 1 have been grouped according to

the physical state at environment conditions as gas, liquid

and char. Fig. 4 shows the yield of each group as a function of

pyrolysis temperature.

The decrease of char residue as a function of pyrolysis

temperature is consistent with the overall increase of the

volatile matter. However, the higher increase of the gas

Fig. 6 e Product yields for different biomass at 300 �C.

products in relation with the decrease of the char must be due

to an additional decomposition of the liquid organic

compounds as temperature increases.

The rest of waste samples were pyrolyzed at 300 �C and the

corresponding chromatograms are shown in Fig. 5. According

to the peak identification, the main degradation products,

common to all samples, include carbon dioxide, methane,

aldehydes, and acids. In addition, caffeine has been detected

as the peak at 57min for the cases of coffee samples. However,

it must be pointed out that pine sawdust shows a much

simpler chromatogram, compared with the rest of samples,

where the organic liquid fraction is lower and water and CO2

are the main degradation products. Grouping the different

components according to their physical state at environment

conditions, the relative content of each group is summarized

in Fig. 6.

Each biomass sample shows different devolatilization

behaviour during the pyrolysis. Among biomass samples

sugar cane bagasse shows the largest yield of liquid and very

low yields of gas and coal meanwhile sawdust of pine gives

rise to the higher yield of gas and water.

4. Conclusions

Themain products obtained fromCuban tobacco pyrolysis are

carbon dioxide, methane, acetic and formic acids, nitro-

genated compounds (acetamide, formamide, propionamide,

pyrrolidinone and nicotine), phenol, ketones and esters.

Moreover, the yield of charcoal and organic liquid products

decreases with pyrolysis temperature. The main components

obtained from the pyrolysis of the rest of biomass carried out

at 300 �C are very similar to those obtained in tobacco pyrol-

ysis. However, charcoal yield is similar for tobacco residue,

sawdust of pine and husk of coffee 2 meanwhile for husk of

b i om a s s a n d b i o e n e r g y 3 4 ( 2 0 1 0 ) 1 5 7 3e1 5 7 7 1577

coffee 1 and sugar cane bagasse the charcoal yield is lower but

the yield of organic liquid product is higher.

Acknowledgements

The authors express their thanks to the University of the

Basque Country for its continuous support through the

Consolidated Groups Program.

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