5-7 OCTOBER

ISFR

2011

69

TOLEDO (SPAIN)

EFFECT OF CATALYSTS ON THERMOGRAVIMETRIC ANALYSIS OF OLIVE STONE
A. Marcilla1, A. N. Garcia1, M.V. Pastor1, A.J. Sanchez2 and D.M. Gomez2
1Chemical Engineering Department, University of Alicante, 03080 Alicante, P. Box 99, Spain
2 Acciona Infraestructuras. Technological Center I+D+I, Valportillo II, nº 8, 28080 Alcobendas, Madrid, Spainemail2:e-mail1: antonio.marcilla@ua.es
dianamaria.gomez.lozano@acciona.esAbstract
Thermogravimetric analysis of two olive stone (OS) samples of different particle size were carried out with the aim to study
possible differences due, not only to heat transfer but also to a possible variation of the composition and segregation of thefractions during sieving. Furthermore, ZnCl2, CoCl2 and MnCl2 were used in order to study the effect of these catalysts on
their thermal degradation. The results obtained show a displacement of the decomposition process to lower temperatures
when different catalysts were used as well as changes on the sharpness of the decomposition peaks. ZnCl 2 seems to be themost active catalyst followed by CoCl2. Their behavior on the thermal decomposition was more remarkable that the results
obtained with MnCl2.

Keywords: thermogravimetric analysis, olive stone, effect of ZnCl2, CoCl2 and MnCl2, particle size

1. Introduction

2. Materials and Methods

Nowadays, Spain is the first country in the ranking of
global production of olive oil with an average annual
production of 700000-800000 tons [1]. Olive stone
represents about a quarter of the total fruit and it is rich inpolysaccharides (cellulose and hemicellulose). So, thepossibility of using olive stone, which would otherwise bediscarded, in the production of biofuels becomes
important.

The material employed in this study was olive stonewhich was supplied by region manufacturers. The
sample was milled, sieved and dried. Experiments werecarried out with two different particle sizes (1.5 < dp <1.25 mm and dp < 0.21 mm) to observe possible
differences between them.

The study of the different fractions of lignocellulosic
materials (hemicellulose, cellulose and lignin) may giveinformation about the behavior of the raw material inaccordance with the different proportions of itscomponents [2].
Thermogravimetric analysis of lignocellulosic material
reveals different decomposition regimes. The first peak inthe decomposition rate at lower temperatures can beassociated with pyrolysis of hemicellulose and the peakat higher temperatures is associated with cellulose
decomposition. However, the wide range oftemperatures, where lignin decomposes, hinders theappearance of a peak attributable to its component. So,
this fraction usually overlaps with hemicellulose andcellulose peaks.
The aim of this work is to study the effect of threedifferent catalysts (ZnCl2, CoCl2 and MnCl2) at different
impregnation degrees on the thermal degradation of two
different particle sizes of olive stone.

interiores libro.indd 69

The samples were impregnated with a solution of aknown concentration of three different catalysts (ZnCl2,CoCl2 and MnCl2) commercially available. The facility ofimpregnation of biomass with small particle size washigher than that of the large sizes. The impregnation
percentages were in the range 2-15%.
A Perkin Elmer TGA7 apparatus was employed for thedynamic pyrolysis experiments. The heating rate used
was 10 ºC/min from 30 ºC to a final temperature of 700ºC in an inert atmosphere of N2 with a flow rate of 20ml/min.

3. Results and Discussion
Figure 1 shows TG and DTG curves for both particle
sizes studied without catalysts. As can been seen, large
differences were found out between them. DTG curve ofsmall particle size presented differences in size andshape of the characteristic peaks respect to the DTG
curve of large particle size. Furthermore, TG curves
showed a difference in the residue obtained between
each particle size about 10%. The studies carried out
showed that these differences obtained were due, notonly to the heat transfer because of the particle size, butalso to the different composition of each size due to apossible composition differences in the particles

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70

6th International Symposium on Feedstock Recycling of Polymeric Materials% Mass-2

OS (1.5 < dp < 1.25 mm)
OS (dp < 0.21 mm)

60-440-6200100-80100200300
400500Temperature (ºC)

600

080

OS (dp < 0.21 mm) + CoCl2
OS (dp < 0.21 mm)

60-440-620700-20% Mass/min

080% Mass/min

100

only changes from 310 to 274 ºC being more acute andmarked, while the second one moves from 360 to 351 ºC
losing sharpness. Besides, it is important to note the twopeaks appearing at temperatures between 100-200 ºC.

% Massdepending on the size achieved during the milling andsieving process.

-80100200300400500600700Fig. 1. TG/DTG curves of both particle size of OS

Temperature (ºC)

The catalyst which appeared to be more active wasZnCl2 as Figures 2 and 3 show, which represent bothparticle size and concentrations studied (about 15 and
6% for small and large particle size respectively). As canbe seen in these Figures, the catalyst produced adisplacement of the decomposition process to lower
temperatures and changes in the size and shape ofcharacteristic peaks. DTG curves showed lesspronounced peaks which were advanced about 100 ºC
respect to the sample without catalyst .

Fig. 4. TG/DTG curves OS (dp < 0.21 mm) with CoCl2 (10%)

100% Mass-440-6200100
OS (dp < 0.21 mm) + ZnCl2
OS (dp < 0.21 mm)

60-2-440-6200% Mass/min% Mass80

100200

300

400

500

600

700

Temperature (ºC)

080-260-440-620-8OS (1.5 < dp < 1.25 mm) + ZnCl2
OS (1.5 < dp < 1.25mm)

00100

200

300
400
500
Temperature (ºC)

% Mass/min% MassFig. 2. TG/DTG curves OS (dp < 0.21 mm) with ZnCl2(15%)

100-10600700

Fig. 3. TG/DTG curves OS (1.5 < dp < 1.25 mm) withZnCl2 (6%)
The behaviour of CoCl2 is similar to ZnCl2 although in thiscase, the advancement of the process is somewhat lower(between 60 and 90 ºC). These results are presented inFigure 4 corresponding to the small particle size.
The catalyst MnCl2 appeared to be the less active asshows Figure 5 where the first peak of decompositioninteriores libro.indd 70

100200300400500Temperature (ºC)

600700Fig. 5. TG/DTG curves OS (dp < 0.21 mm) with MnCl2(12%)

4. Conclusions
The results reached indicate that the processes of millingand sieving of the biomass can produce a segregation ofits components leading to thermogravimetrical curves
that depend on the particle size of biomass.

-80-8
00-2

60

% Mass/min

0
OS (dp < 0.21 mm) + MnCl2
OS (dp < 0.21 mm)

80

Thermogravimetric analysis carried out after
impregnating olive stones with ZnCl2, CoCl2 and MnCl2
show that ZnCl2 presents a high activity reducing thedecomposition temperature significantly. Although MnCl2
produces a low reduction of degradation temperature,comparing with the other catalysts, it can modify theprocess by acting on the different components in adifferent way.

Acknowledgements
Finnancial support for this investigation has been
provided by CDTI (Project Ingenio 2010-CDTI-BioSosCEN-2009-1040) and by Ministry of Science andInnovation. Local investment fund for employment.
Government of Spain.

References[1] http://www.oleohispana.com[2] J.A. Caballero, R. Font, A. Marcilla. Comparative
study of the pyrolysis of almond shells and their fractions,holocellulose and lignin. Product yields and kinetics.
Thermochimica Acta 276 (1996) 57-77

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