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TOLEDO (SPAIN)RECYCLING OF PLASTIC WASTE BY CO-PYROLYSIS WITH OLIVE RESIDUEIN AUTOCLAVE REACTOR
A. Aboulkas 1,2, K. El harfi 1,2, M. Nadifiyine1, M. Benchanaa1
1 Laboratoire de Recherche sur la Réactivité des Matériaux et l’Optimisation des Procédés «REMATOP», Département dechimie, Faculté des Sciences Semlalia, Université Cadi Ayyad, BP 2390, 40001 Marrakech, Maroc
2 Laboratoire Interdisciplinaire de Recherche en Sciences et Techniques, Faculté polydisciplinaire de Béni-Mellal, UniversitéSultan Moulay Slimane, BP 592, 23000 Béni-Mellal, Maroc.
e-mail: a.aboulkas@yahoo.fr

Abstract
Solid wastes compromise biomass and plastics in terms of energy recuperation. Pyrolysis is the promising process inthermochemical conversions. In this study, co-pyrolysis of olive residue and high density polyethylene (HDPE) mixtures(50:50, w/w) was executed in autoclave reactor. Co-pyrolysis runs were performed using pyrolysis temperatures between
400 and 600 °C with heating rates of 2 to 20 °C/min to generate modified bio-oil-.It is interesting to note that the highest
bio-oil yield was obtained at 500 °C with a heating rate of 10 °C/min. These bio-oil exhibited higher carbon and hydrogencontents, significantly lower oxygen contents, and lower water contents, acid values and viscosities than olive residue
bio-oil.

Keywords: Bio-oil; Co-pyrolysis; Olive residue; Plastic waste; HDPE

1. Introduction
Plastics consumption has increased rapidly
throughout the world. The rising cost of petroleum isincreasing the price of both polymers and fuels, creating ahuge opportunity to recycle these plastic wastes orconvert them to fuels. Biomass/plastic co-pyrolysis offers
one route to liquid fuels. Pyrolysis is a chemical recycling
process that breaks organic macromolecules into small
molecules at high temperatures in the absence of oxygen
via free radical degradation pathways [1,2]. Biomass is a
mixture of hemicellulose, cellulose, lignin and minor
amounts of other organics which each pyrolyses ordegrades at different rates and by various mechanisms
and pathways. Lignin decomposes over a wider
temperature range compared to cellulose andhemicellulose, which rapidly degrade over narrower
temperature ranges, hence the apparent thermal stabilityof lignin during pyrolysis. The rate and extent of
decomposition of each of these components depends on
the process parameters such reactor (pyrolysis)
temperature, biomass heating rate and pressure [3].
Polyolefins contain higher hydrogen and carbon content
than biomass and no oxygen. Therefore, plastic/biomass
co-pyrolysis may upgrade the bio-oil properties byincreasing the carbon and hydrogen contents while
reducing the oxygen present. The elemental content ofpolyolefin plastics contains more hydrogen (approximately
14% higher) and carbon than biomass. Therefore, plastics
produce liquid products with higher hydrogen and carbon
content than biomass thermal degradation products [3,4].
The objective of the research was reported here to
produce upgraded bio-oil with lower oxygen and higher

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carbon and hydrogen contents by performing relatively
fast, co-pyrolyses of plastics with the olive residue.

2. Materials and Methods
Olive residue was obtained from the solid productof traditional olive oil process (Maasra in Morocco). Airdried olive residues were ground to obtain a uniform
material of an average particle size (0.2 mm). The
samples of HDPE were provided by Plador (Marrakech,Morocco). The OR:HDPE (1:1 mass ratio) mixture wasblended by tumbling for 30 min in order to achieve
homogeneity.
The co-pyrolysis experiments were performed in a 150
ml stainless steel autoclave reactor, with a sweep gas(nitrogen) connection. The autoclave is equipped apressure release system limiting the pressure to a
maximum of 300 bar. The reactor was heated externallyby an electric furnace and the initial nitrogen gas
pressure is 6 bar

3. Results and Discussion
3.1. Influence of the heating rate
Table 1 shows the yield of oil, gases andconversion from the pyrolysis of the olive residue, HDPEand their mixture (1:1) in relation to heating rate from 2 to20 °C min-1 to a final pyrolysis temperature of 500 °C in
the autoclave reactor. It can be seen that there was anincrease in oil from 2-10 °C min-1 after which the yield ofoil decreased as the heating rate was increased to 20 °C
min-1. The yield of the conversion and gases increased
progressively throughout as the heating rate increased

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6th International Symposium on Feedstock Recycling of Polymeric Materials

from 2 to 20 °C min-1, while there was a corresponding
progressive decrease in char.
Table 2: Effect of heating rate on product yields attemperature of 500 °C.
Heating rate (°C/min)
Conversion
Olive
Oil
residue
Gas
Conversion
HDPE
Oil
Gas
Conversion
Olive
residue
Oil-HDPE
Gas

2
64.3
42.9
21.4
97.3
88.6
8,7
85,8
72,75
10,35

5
65.5
43.8
21.7
98.4
88.5
9,9
86,95
73,15
11,1

10
66.4
45.6
21.9
99.3
88.3
11
87,85
73,95
11,2

1567.545
22.5
99.4
87.8
11,688,4573,412,35

20
68.6
43.8
24.8
99.6
87.4
12,289,172,613,8

3.2. Influence of the pyrolysis temperature
In the second group of experiments performed in theautoclave, for pyrolysis temperature between 400 and 600°C at a heating rate of 10 °C min-1, the product yields ofpyrolysis of the sugarcane bagasse in relation to thetemperature are given in Table 2.
At the lowest pyrolysis temperature examined of 400 °C,
the oil yield was low, this data reflecting incomplete
pyrolysis. As the temperature was increased the oil yield
increased until it reached a maximum at 500 °C, after
which there was a decrease in oil yield at 600 °C. There
was a progressive increase in conversion and gas yieldand conversion degree from 400 °C to 600 °C, while thechar decrease as the temperature of pyrolysis increased.

References[1] D.S. Achilias, C. Roupakias, P. Megalokonomos, A.A.
Lappas, E.V. Antonakou. Chemical recycling of plastic
wastes made from polyethylene (LDPE and HDPE) andpolypropylene (PP). J Hazard Mat (2007) 536-542.
[2] V.I. Sharypov, N. Marin, N.G. Beregovtsova, S.V.
Baryshinkov, B.N. Kuznetsov, V.L. Cebolla, et al. Copyrolysis of wood biomass and synthetic polymer
mixtures. Part I: influence of experimental conditions on
the evolution of solids, liquids and gases. J Anal ApplPyrol (2002) 15–28.
[3] N. Marin, S. Collura, V.I. Sharypov, N.G.
Beregovtsova, S.V. Baryshnikov, B.N. Kutnetzov, et al.
Copyrolysis of wood biomass and synthetic polymers
mixtures. Part II: characterisation of the liquid phases. JAnal Appl Pyrol (2002) 41–55.
[4] V.I. Sharypov, N.G. Beregovtsova, B.N. Kuznetsov, L.
Membrado, V.L. Cebolla, N. Marin, et al. Co-pyrolysis ofwood biomass and synthetic polymers mixtures. Part III:
characterisation of heavy products. J Anal Appl Pyrol(2003) 325–40.

Table 2: Effect of temperature on product yields atheating rate of 10 °C/min.
Temperature (°C)
Conversion
Oil
Gas
Conversion
HDPE
Oil
Gas
Conversion
Olive
residue
Oil-HDPE
Gas
Oliveresidue

400
61,2
41,4
20,993,985
8,984,1571,45
9,9

450
64,443,821,7
95
85,6
9,4
84,75
71,85
10,1

500
66,4
45,6
21,9
99,3
88,3
11
87,95
73,95
11,2

525
67,1
45,3
22,9
99,6
86,1
11,7
88,85
74,85
11,2

550
67,4
45
23,5
99,7
84,2
13,4
89,45
70,55
16,1

600
67,7
43,8
24,9
99,7
82,1
16
91,55
70,45
18,3

4. Conclusions
At a reactor bed temperature of 500°C with aheating rate of to 10 °C/min, an oil yield of 73,95wt% ofdry feed was obtained for the mixture of olive residue andHDPE. The pyrolysis process temperature was found tohave influenced on the product yields. The results showthat co-pyrolysis of olive residue and HDPE is a good
option for producing bio-oils to be used as alternative topetroleum fuels and valuable chemical feedstocks.

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