Mechanistic interpretation of base-catalyzed depolymerization of polystyrene

Oh Sang Woo; Nancy Ayala; Linda J. Broadbelt

doi:10.1016/S0920-5861(99)00235-7

Mechanistic interpretation of base-catalyzed depolymerization of polystyrene

Oh Sang Woo, Nancy Ayala, Linda J. Broadbelt^*

^*Corresponding author for this work

Chemical and Biological Engineering

Research output: Contribution to journal › Conference article › peer-review

88 Scopus citations

Abstract

The effect of a base catalyst, MgO, on the decomposition of polystyrene was studied through degradation of both a monodisperse polymer (number average molecular weight =50,500 g/mol) and a polystyrene mimic, 1,3,5-triphenylhexane (TPH), to determine the potential of applying base catalysts as an effective means of polymer recycling. The presence of the catalyst increased the decomposition rate of the model compound but decreased the degradation rate of polystyrene as measured by evolution of low molecular weight products. Although the model compound results suggest that the rate of initiation was enhanced in both cases by the addition of the catalyst, this effect is overshadowed for the polymer by a decrease in the 'zip length' during depropagation due to termination reactions facilitated by the catalyst. Due to the small size of the model compound, this effect does not impact its observed conversion since premature termination still affords a quantifiable low molecular weight product. A decrease in the selectivity to styrene monomer in the presence of MgO was observed for both polystyrene and TPH. Reconciliation of our results with those of Zhang et al. [Z. Zhang, T. Hirose, S. Nishio, Y. Morioka, N. Azuma, A. Ueno, H. Ohkita and M. Okada, Industrial and Engineering Chemistry Research, 34 (1995) 4514.] based on differences in the reactor configuration used is discussed.

Original language	English (US)
Pages (from-to)	161-171
Number of pages	11
Journal	Catalysis Today
Volume	55
Issue number	1-2
DOIs	https://doi.org/10.1016/S0920-5861(99)00235-7
State	Published - Jan 5 2000
Event	Proceedings of the 1998 2nd World Congress on Environmental Catalysis - Green Chemistry - Miami, FL, United States Duration: Nov 15 1998 → Nov 20 1998

Funding

The authors would like to thank Dr. Joyce Brockwell for the guidance and the use of laboratory equipment without which the synthesis of 1,3,5-triphenylhexane would not have been possible. The authors would also like to thank Sarah Vos for synthesizing the model compound for our experimental study. This work was supported by the MRSEC program of the National Science Foundation (DMR-9632472) at the Materials Research Center of Northwestern University. The support of the Engineering Research Equipment Grant Program of the National Science Foundation (CTS-9622375) and the office of solid Waste Research is also gratefully acknowledged.

ASJC Scopus subject areas

Catalysis
General Chemistry

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10.1016/S0920-5861(99)00235-7

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title = "Mechanistic interpretation of base-catalyzed depolymerization of polystyrene",

abstract = "The effect of a base catalyst, MgO, on the decomposition of polystyrene was studied through degradation of both a monodisperse polymer (number average molecular weight =50,500 g/mol) and a polystyrene mimic, 1,3,5-triphenylhexane (TPH), to determine the potential of applying base catalysts as an effective means of polymer recycling. The presence of the catalyst increased the decomposition rate of the model compound but decreased the degradation rate of polystyrene as measured by evolution of low molecular weight products. Although the model compound results suggest that the rate of initiation was enhanced in both cases by the addition of the catalyst, this effect is overshadowed for the polymer by a decrease in the 'zip length' during depropagation due to termination reactions facilitated by the catalyst. Due to the small size of the model compound, this effect does not impact its observed conversion since premature termination still affords a quantifiable low molecular weight product. A decrease in the selectivity to styrene monomer in the presence of MgO was observed for both polystyrene and TPH. Reconciliation of our results with those of Zhang et al. [Z. Zhang, T. Hirose, S. Nishio, Y. Morioka, N. Azuma, A. Ueno, H. Ohkita and M. Okada, Industrial and Engineering Chemistry Research, 34 (1995) 4514.] based on differences in the reactor configuration used is discussed.",

author = "Woo, {Oh Sang} and Nancy Ayala and Broadbelt, {Linda J.}",

note = "Funding Information: The authors would like to thank Dr. Joyce Brockwell for the guidance and the use of laboratory equipment without which the synthesis of 1,3,5-triphenylhexane would not have been possible. The authors would also like to thank Sarah Vos for synthesizing the model compound for our experimental study. This work was supported by the MRSEC program of the National Science Foundation (DMR-9632472) at the Materials Research Center of Northwestern University. The support of the Engineering Research Equipment Grant Program of the National Science Foundation (CTS-9622375) and the office of solid Waste Research is also gratefully acknowledged.; Proceedings of the 1998 2nd World Congress on Environmental Catalysis - Green Chemistry ; Conference date: 15-11-1998 Through 20-11-1998",

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N2 - The effect of a base catalyst, MgO, on the decomposition of polystyrene was studied through degradation of both a monodisperse polymer (number average molecular weight =50,500 g/mol) and a polystyrene mimic, 1,3,5-triphenylhexane (TPH), to determine the potential of applying base catalysts as an effective means of polymer recycling. The presence of the catalyst increased the decomposition rate of the model compound but decreased the degradation rate of polystyrene as measured by evolution of low molecular weight products. Although the model compound results suggest that the rate of initiation was enhanced in both cases by the addition of the catalyst, this effect is overshadowed for the polymer by a decrease in the 'zip length' during depropagation due to termination reactions facilitated by the catalyst. Due to the small size of the model compound, this effect does not impact its observed conversion since premature termination still affords a quantifiable low molecular weight product. A decrease in the selectivity to styrene monomer in the presence of MgO was observed for both polystyrene and TPH. Reconciliation of our results with those of Zhang et al. [Z. Zhang, T. Hirose, S. Nishio, Y. Morioka, N. Azuma, A. Ueno, H. Ohkita and M. Okada, Industrial and Engineering Chemistry Research, 34 (1995) 4514.] based on differences in the reactor configuration used is discussed.

AB - The effect of a base catalyst, MgO, on the decomposition of polystyrene was studied through degradation of both a monodisperse polymer (number average molecular weight =50,500 g/mol) and a polystyrene mimic, 1,3,5-triphenylhexane (TPH), to determine the potential of applying base catalysts as an effective means of polymer recycling. The presence of the catalyst increased the decomposition rate of the model compound but decreased the degradation rate of polystyrene as measured by evolution of low molecular weight products. Although the model compound results suggest that the rate of initiation was enhanced in both cases by the addition of the catalyst, this effect is overshadowed for the polymer by a decrease in the 'zip length' during depropagation due to termination reactions facilitated by the catalyst. Due to the small size of the model compound, this effect does not impact its observed conversion since premature termination still affords a quantifiable low molecular weight product. A decrease in the selectivity to styrene monomer in the presence of MgO was observed for both polystyrene and TPH. Reconciliation of our results with those of Zhang et al. [Z. Zhang, T. Hirose, S. Nishio, Y. Morioka, N. Azuma, A. Ueno, H. Ohkita and M. Okada, Industrial and Engineering Chemistry Research, 34 (1995) 4514.] based on differences in the reactor configuration used is discussed.

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JO - Catalysis Today

JF - Catalysis Today

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T2 - Proceedings of the 1998 2nd World Congress on Environmental Catalysis - Green Chemistry

Y2 - 15 November 1998 through 20 November 1998

ER -

Mechanistic interpretation of base-catalyzed depolymerization of polystyrene

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