1.
 Effect of Variation of Molecular Weight for the Pyrolysis of Polystyrene
 

      


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305-600    100 (2002 8 30 , 2003 3 25 )

Effect of Variation of Molecular Weight for the Pyrolysis of Polystyrene

Yu Mee Kim, Byoung Tae Yoon, Seong Bo Kim, Sang Bong Lee and Myoung Jae Choi^†

Advanced Chemical Technology Division, Korea Research Institute of Chemical Technology, 100 Jang-dong, Yuseong-gu, Daejeon 305-600, Korea

(Received 30 August 2002; accepted 25 March 2003)



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Abstract−Oil formation rate, composition of crude oil and formation of side products such as α-methyl styrene, ethyl ben- zene, benzene, toluene, dimer and trimer on thermal degradation of polystyrene were affected by various factors. Especially, melting temperature and melting time gave an important influence on formation of oil and composition of crude oil. Also, com- position of formed crude oil showed a siginificant difference on reaction time. These results were caused by changes of aver- age molecular weight of degraded polystyrene. Decrease of molecular weight by cracking gave a decrease of yield of styrene and an increase of formation of α-methyl styrene, ethyl benzene, benzene, toluene. Reaction kinetic study and degradation mechanism to styrene on polystyrene were also briefly discussed.

Key word: Pyrolysis, Polystyrene, Styrene, Molecular Weight, Ethylbenzene

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†To whom correspondence should be addressed.

E-mail: mjchoi@krict.re.kr

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Table 1. Effect of reaction temperature on the pyrolysis of polystyrene Reaction temperature(^oC) 350 360 370 380 390 Formation of oil(ml/min) 0.84 1.32 2.88 4.19 6.86

Product oil(%) 66.5 77.5 85.0 89.0 95.0

Residue(%) 32.0 20.6 13.7 9.3 3.5

Carbon(%) 1.5 1.9 1.3 1.7 1.5

Chemical composition of oil(wt%)

Styrene monomer(wt%) 67.37 67.74 70.30 71.07 70.68 α-methyl styrene(wt%) 3.87 3.45 2.84 2.60 2.29

Toluene(wt%) 4.29 3.77 2.46 2.77 1.96

Benzene(wt%) 0.24 0.23 0.19 0.16 0.21

Ethylbenzene(wt%) 1.90 1.68 1.09 0.92 0.78

Others(wt%) 22.33 23.13 23.22 22.48 24.08

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Table 2. Composition of pyrolyzed oil formed from thermal degradation of polystyrene at 380^oC

Reaction time(min) 30 60 90 120 150

Styrene monomer(wt%) 73.8 67.8 63.8 59.6 57.2 α-methyl styrene(wt%) 1.25 1.47 1.92 2.62 4.21

Toluene(wt%) 1.70 1.67 1.60 1.72 2.42

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Ethylbenzene(wt%) 0.15 0.50 0.15 0.06 0.32

Others(wt%) 23.0 28.4 32.4 35.9 35.7

Fig. 4. Changes of average molecular weights for reaction time.

Fig. 5. Changes of average molecular weight on melting temperature.

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reaction temperature.

Table 3. Effect of molecular weight on the pyrolysis of waste EPS at 380^oC

Average molecular weight 94,000 119,000 134,000 150,000 164,000 180,000 189,000 195,000

Styrene monomer(wt%) 66.70 66.41 69.19 67.85 64.57 62.96 61.97 61.02

α-methyl styrene(wt%) 4.63 3.85 2.47 3.61 3.87 4.03 4.47 4.59

Toluene(wt%) 1.98 2.82 0.95 1.67 1.71 2.00 3.36 3.61

Benzene(wt%) 0.11 0.12 0.12 0.12 0.15 0.13 0.12 0.12

Ethylbenzene(wt%) 1.56 1.50 0.34 0.86 1.05 1.15 2.25 2.76

Others(wt%) 25.02 25,30 26.95 26.00 24.66 24.73 27.84 27.91

Fig. 7. Reaction constants on various melting temperatures.

Fig. 8. Reaction pathways on the formation of styrene monomer from thermodegradation of polystyrene.

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