PARTⅠ PYROLYSISCOMPARING PYROLYSIS BEHAVIOR
OF VIRGIN AND WASTE PLASTICS
J.M.N. Van Kasteren*1, Q. Zhou 1,2, A.H.A. Verberne3
1. Eindhoven University of Technology, TU/e Innovationlab, PO Box 513, 5600 MB
Eindhoven, The Netherlands
E-mail: J.M.N.v.Kasteren@tue.nl
2. Center for Degradable and Flame-Retardant Polymeric Materials (ERCEPM-MoE),
College of Chemistry, State Key Laboratory of Polymer Materials Engineering, Sichuan
University, Chengdu 610064, China
3. Ingenia Consultants & Engineers, PO Box 9550, 5602 LN Eindhoven, The Netherlands
1. Introduction
Pyrolysis of polymers is often regarded as the most promising technology for resource
recovery from waste polymer materials[1].Quite a lot of research work on the pyrolysis ofindividual and mixed plastics into liquid products has been reported[2]. However, in case ofwaste plastics, additives as well as “weak bonds” caused by aging might change the pyrolysis
behavior when compared to virgin plastics. Moreover, many new catalysts have beendeveloped for the pyrolysis of plastics [3]. Although most of them showed quite high catalytic
cracking abilities for virgin plastics, the feasibility to be used for waste plastics should beproved. In this paper, preliminary work has been done in order to compare the pyrolysis
behavior of virgin and waste plastics.
2. Experimental
The pyrolysis of polymers was carried out in a glass reactor (20 ml volume) by batch
operation. In a typical pyrolysis run, about 1.3 g of materials and 0.065 g catalysts (forcatalytic pyrolysis reaction) were added to the reactor and reacted at 430 °C until no liquid
was produced. The pyrolysis oils were obtained using a Shimadzu GC 17A gas
chromatography equipped with a Shimadzu GCMS-QP5000 mass selective detector (GC/MS)
and a 25 m × 0.25 mm × 0.4 µm Chrompack capillary column.
3. Results and discussion
As for pyrolysis behaviors of HDPE, HDPE waste produces higher liquid yield andlower residue yield compared with that of virgin HDPE (Tab.1). Moreover, the liquid
distribution is similar to the virgin one with a wide and evenly distributed carbon number
distribution (C5-C34) (Fig.1). HDPE waste are composed of granules with different colors.
After pyrolysis, clear yellowish liquid product has been obtained that owns similar appearancewith that of liquid from virgin HDPE. Moreover, it can be observed that the blue dyes were- 101 -The 5th ISFR (October 11-14, 2009, Chengdu, China)
left in residue. The HDPE waste probably owns higher amounts of “weak bonds” such ascarboxyl and hydoxyl groups due to the aging process under natural environment or thesegroups may be formed during processing of polymer, which is beneficial to the thermal
degradation of HDPE.
In addition, SiO2-Al2O3 showed similar catalytic cracking ability for both virgin HDPEand HDPE waste, i.e., increased liquid yield and decreased residue yield; narrower and lighter
liquid carbon number distribution (C5-C16), indicating the additives in HDPE waste such asdyes would not affect the catalytic cracking activities of SiO2-Al2O3.
PP waste showed much higher liquid yield and lower residue yield than those of HDPE
waste due to the methyl group in PP molecular chain. Compared with virgin PP, PP wasteowns a slightly lower liquid yield and higher residue yield (Tab.1). However it has to beconsidered that inorganic filling materials may also be the cause of increase in residue
amounts. The additives such as antioxidants in PP waste maybe responsible for the inhibited
thermal degradation behavior of PP. Moreover, SiO2-Al2O3 showed similar catalytic cracking
ability for virgin PP and PP waste, suggesting only minor influence of the additives in PP for
the catalytic cracking abilitiy of the SiO2-Al2O3.
For pyrolysis behaviors of polystyrene (PS), waste PS produced higher liquid yield(89.23 wt%) and lower gas yield (1.54 wt%) than those of PS. Moreover, waste PS had muchhigher heavier liquid components (trimer). In addition, similar with virgin HIPS, SiO2-Al2O3
showed few catalytic cracking effects for PS waste.
Tab. 1 Product Yields from thermal and catalytic pyrolysis of virgin and waste HDPE, PP and PS
Product yield (wt. %)Materials
LiquidGas

Residue

HDPE

34.85

10.61

54.55

HDPE waste

46.92

10.77

42.31

PPPP Waste

80.77
72.31

12.31
13.08

6.92
14.62

HIPS

79.39

7.63

12.98

Waste PS

89.23

1.54

9.23

HDPE- SiO2-Al2O373.85

21.15

5.00

HDPE waste- SiO2-Al2O3
PP- SiO2-Al2O3

73.08
73.85

21.15
10.77

5.77
10.38

PP waste- SiO2-Al2O3

70.77

17.31

11.92

PS

79.39

7.63

12.98

PS-SiO2-Al2O3

83.21

1.53

15.27

PS Waste

89.23

1.54

9.23

PS Waste /SiO2-Al2O3

86.92

5.77

7.31

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25

105

HDPE waste
HDPE

HDPE+SiO2-Al2O3

Amount (wt%)

Amount (wt%)

HDPE waste+SiO2-Al2O3
201510500
6 8 10 12 14 16 18 20 22 24 26 28 30 32 34

6 8 10 12 14 16 18 20 22 24 26 28 30 32 34

Carbon Number

Carbon Number

251520PP waste
PP

Amount (wt%)

Amount (wt%)

2025105500

6 8 10 12 14 16 18 20 22 24 26 28 30 32 34

6 8 10 12 14 16 18 20 22 24 26 28 30 32 34

Carbon Number

Carbon Number

55

55

50

PS waste
PS

35
30
2520
15
10

Amount (wt%)

Amount (wt%)

PPwaste-SiO2-Al2O3

15

1050
45
40

PP-SiO2-Al2O3

45
40

PS-SiO2-Al2O3
PS waste-SiO2-Al2O3

35
30
25
20
15105500
6 8 10 12 14 16 18 20 22 24 26 28 30 32 34

6 8 10 12 14 16 18 20 22 24 26 28 30 32 34

Carbon Number

Carbon Number

Fig.1 Liquid product distribution from thermal and catalytic
pyrolysis of virgin and waste HDPE, PP and PS
4. Conclusions(1) HDPE waste owns a higher pyrolysis activities than those of virgin HDPE. The liquid
product distribution is similar with that of virgin HDPE. SiO2-Al2O3 showed similar catalytic
cracking ability for both virgin HDPE and HDPE waste.

- 103 -The 5th ISFR (October 11-14, 2009, Chengdu, China)(2) PP waste owns a slightly lower pyrolysis activities than those of virgin PP. Moreover,
SiO2-Al2O3 showed similar catalytic cracking ability for both virgin PP and PP waste,suggesting the additives in PP didn’t affect the catalytic cracking abilitiy of the SiO2-Al2O3.
(3) Waste PS produced higher liquid yield and lower gas yield than those of virgin HIPS.
Moreover, waste PS had much higher heavier liquid components. Similar with virgin HIPS,
SiO2-Al2O3 showed few catalytic cracking effects for PS waste.
References[1] W. Kaminsky, F. Hartmann, Angew. Chem. Int. Edit. 2000, 39, 331.
[2] P. T. Williams, E. A. Williams, J. Anal. Appl. Pyrolysis. 1999, 51, 107.
[3] Q. Zhou, Y. Z. Wang, C. Tang, Y. H. Zhang, Polym. Degrad. Stab, 2003, 80(1), 23.

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