PYROLYSIS OF TETRA PACK PACKAGING
Ahmet Korkmaz 2 , Jale Yanik 2 , Mihai Brebu 1 and Cornelia Vasile 1
1“Petru Poni” Institute of Macromolecular Chemistry, 700487 Iasi, ROMANIA
2Ege University, Faculty of Science, Chemistry Department, 35100 Izmir,TURKEY(1) Introduction
Aseptic packages along with milk and juice cartons are recycled throughhydropulping process that separates the thin layers of plastic and Al from cellulose
fibers. However humidity and impurities affect products’ quality. Wu and Chang
studied the kinetic of thermal decomposition of Tetra Pack by using TGA andfound that the total reaction rate was a summation of individual behavior of LDPE
and Kraft paper.[1] In this work the pyrolysis of Tetra Pack packaging in various
conditions has been investigated as an alternative treatment.
(2) Experimental and analytical sections
Tetra Pack samples were collected from waste. The composition was of 63
wt% paper cardboard (Kraft cellulose), 30 wt% PE and 7 wt% Al. TG/DTA analysisof different layers separated from Tetra Pack was performed in N 2 atmosphere andheating rate of 10 °C/min to find decomposition temperatures and possible
interactions between components. Pyrolysis was carried out by semi-batch
operation in N 2 atmosphere.The reactor was heated with 5 ºC/min up to the desired
temperature of 400, 500 or 600 °C at which it was held for 1 hour. Stepwise
pyrolysis was performed by maintaining the reactor at 350 °C for one hour thenheating it up to 500 °C for another one hour. The volatile products were swept fromthe reactor by N 2 gas to collection traps cooled in water-ice bath. The condensed
aqueous and organic phase (wax + tarry compounds) were separated bycentrifugation. Solid residue consisted of coke and aluminum that were separated
by sinking in water. Pyrolysis products were characterized by chromatographic
and spectroscopic methods described elsewhere.[2](3) Results and Discussion
TG showed that cardboard layers have a main degradation step at 200 – 400°C, at lower temperature than PE layer that degrades at 380 – 515 °C; however
there is a small overlapping region (380 – 400 °C) of the two temperature ranges.
DTG curve of cardboard shows a long tail in the temperature range of PEdegradation. Therefore some interactions could occur between PE and cardboard(especially its residue from the main degradation step). Above 105 °C the DTG
curve of Tetra Pack shows two degradation steps at 200 - 500 °C, the first one fordecomposition of cardboard layers and the second one for decomposition ofpolyethylene. It seems that aluminum had no effect on decomposition of thesecomponents.
Wax yield in semi-batch pyrolysis of Tetra Pack sharply increased and theamount of char decreased with increasing temperature up to 500 °C but noconsiderable change in product yield was observed with further increase oftemperature at 600 °C (Table 1). Stepwise pyrolysis showed clear separation of
aqueous phase, tar and most part of gases resulted from degradation of cardboard
in the first pyrolysis step (at 350 °C) while PE wax was collected from the second
pyrolysis step. The total yield of products from stepwise pyrolysis was close tothat from semi-batch pyrolysis at 500 °C but both were slightly different from thetheoretical one calculated based on product yield from degradation of Tetra Pack
components. Therefore small interactions occur mainly during degradation of PElayer and the second step of cardboard degradation leading to less wax, char andtar and more aqueous phase.
Table 1. Influence of process parameters on the pyrolysis yields (wt%) of Tetra
Pack waste
cardboarPEd
500 °C

Th.
mix.

500

Tetra Pack
*Tetra Pack stepwise

semi-batch

500

400°C°Co

23.9

23.3

32.6

C

500 o C 600 o C

step Iostep II

total

350 C

500 o C

23.9

19.9

2.3

22.2

31.8

29.6

32.8

-

32.8

Gas

29.9

18.4

24.4

Aqueous39.4-

24.8Tar

3.1-

1.9

2.0

1.5

0.7

1.1

-

1.1

Wax-

73.1

21.9

4.8

17.9

20.4

-

18.7

18.7

18.4

18.4

6.8

6.8

phase

Char

27.6

Al foil
*

8.5

20.2

29.7

18.6

18.4

7.0

6.9

7.0

Theoretical mixture as in Tetra Pack: cardboard 63%, PE 30%;

46.2

**

**

decomposed

instep II of pyrolysis

The gas composition from the stepwise pyrolysis of Tetra Pack is given in
Table 2. The gas products from the first pyrolysis step at low temperature of350 °C consisted largely of CO x compounds, main gaseous products fromdegradation of cellulose. In the second step at 500 °C, which corresponds to PE
degradation, the major gaseous products were H 2 , C 1 , C 2 and C 3 hydrocarbons.
However the presence of CO and CO 2 gases in this step is a proof of degradationof cardboard residue resulted in the first pyrolysis step. As most part of gaseous
products was formed in the first pyrolysis step and contains a high content ofCorresponding author: Mihai Brebu“Petru Poni” Institute of Macromolecular Chemistry, 700487 Iaşi, Romania
Tel.: +40232217454; Fax: +40232211299, E-mail: bmihai@icmpp.rocarbon oxides, it can be said that the obtained gases from Tetra Pack pyrolysis did
not have a high calorific value. However they could provide some part of theenergy requirements for a pyrolysis plant.
Table 2. Composition of the gas products (mol %) from the stepwise pyrolysis ofTetra PackPyrolysis stepCOCO 2

H2

C1

C2

C3

C4C5C6

Step I – 350 °C

34.79

52.70

5.86

2.60

1.60

1.16

0.78

0.27

0.24

Step II – 500 °C

4.87

2.12

32.08

28.02

15.00

9.45

5.62

2.86

0.01

Wax quality depends on pyrolysis conditions and purity. Its averagemolecular weight and molecular weight distribution increases with pyrolysis
temperature and after purification – Table 3. The most polydisperse waxes wereobtained at 600 o C and by stepwise procedure.
Table 3. Average molecular weight and polydispersity index of the pyrolysis
waxes
MwMn

Polydispersity
index

Semi-batch, 400 °C

403

356

1.134

Semi-batch, 500 °C

443

378

1.172

Semi-batch, 500 °C (washed with520

436

1.193

Semi-batch, 600 °C

844

6631.273

Stepwise

847

676

1.253

Polyethylene, semi-batch, 500 °C

5314581.159

acetone)(4) Conclusions
Pyrolysis of Tetra Pack wastes was performed studying the effect ofpyrolysis temperature and procedure on the yields of products. Gas and liquidproducts (aqueous phase and tar) from degradation of cellulose as well as
polyethylene wax were obtained. The aluminum was quantitatively recovered byseparation from carbon residue in char.
(5) References
1. C.H. Wu, H.S. Chang, “Pyrolysis of tetra pack in municipal solid waste”, J. Chem.
Technol. Biotechnol. 76 (2001) 779-792.

2. C. Vasile, M. A. Brebu, M. Totolin, J. Yanik, T. Karayildirim, H. Darie, “Feedstock Recycling fromthe Printed Circuit Boards of Used Computers”, Energy & Fuels 22 (2008) 1658–1665.

Corresponding author: Mihai Brebu“Petru Poni” Institute of Macromolecular Chemistry, 700487 Iaşi, Romania
Tel.: +40232217454; Fax: +40232211299, E-mail: bmihai@icmpp.ro