Depolymerization Reactions of <i>cis</i>-Polyisoprene and Scrap Rubber in Supercritical Toluene

Dhawan, Jagdish C.; Bencsath, Aladar; Legendre, Richard C.

doi:10.1021/bk-1992-0514.ch030

Cited by 9 publications

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“…The attractive features of SCFs for coal and biomass processing also motivated research into using SCFs in polymer decomposition. Dhawan et al (1991Dhawan et al ( , 1993 investigated the thermolysis of a styrene-butadiene copolymer in SC toluene and tetralin and the thermolysis of cispolyisoprene and scrap rubber in SC toluene. They also reported results from the reaction of SC toluene, tetralin, and their mixtures.…”

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confidence: 99%

“…They also showed that secondary reactions that form polycondensates are remarkably suppressed relative to pyrolytic depolymerization of the same materials. Dhawan et al (1991Dhawan et al ( , 1993 identified over 100 different products in their depolymerization reactions, and many of these arose from reactions of the polymer with the SCF solvents used in their studies.…”

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confidence: 99%

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Reactions at supercritical conditions: Applications and fundamentals

et al. 1995

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Reactions at supercritical conditions: Applications and fundamentals

et al. 1995

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“…Koll and Metzger used supercritical acetone to study the degradation of cellulose and chitin 1. Dhawan et al decomposed polyisoprene and waste rubber using supercritical toluene 2. Watanabe et al compared the results of general thermolysis with those of supercritical fluid degradation 3.…”

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confidence: 99%

Characteristics and kinetics of degradation of polystyrene in supercritical water

Kwak

Shin

Bae

et al. 2006

J of Applied Polymer Sci

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ABSTRACT:The degradation of polystyrene (PS) in subor supercritical water was carried out at reaction temperatures ranging from 370°C to 420°C and pressures of 240 to 320 bar. At 370°C, where water is in a subcritical state, the degradation was in equilibrium in about 5 min, whereas at 380°C and 390°C, where water is in a supercritical state, it was completed in 15 and 3 min, respectively. The equilibrium conversion in the supercritical state (100 wt %) was higher than that in the subcritical water (ca. 80 wt %). The dependence on time of selectivity for the degradation products-styrene monomer, styrene dimer, styrene trimer, toluene, ethyl benzene, isopropyl benzene, and triphenyl benzene-were investigated at 400°C and 280 bar. As the reaction proceeded, selectivity for styrene monomers, dimers, and trimers decreased, whereas that for toluene, ethyl benzene, and isopropyl benzene increased because of the difficulty of decomposing the benzene rings and phenyl radicals. Triphenyl benzene increased with reaction time for the same reason. With increasing temperature, selectivity for the styrene monomers and dimers decreased slightly, whereas selectivity for toluene and ethyl benzene increased a little. The kinetic behavior of PS in supercritical water along with supercritical acetone and n-hexane were investigated. The degradation processes of PS in such supercritical fluids could be formulated by the first-order kinetic law at the initial stage of the reaction. The activation energy for the degradation in supercritical water was evaluated to be 157 kJ/mol compared to an activation energy of 132 kJ/mol in the supercritical n-hexane.

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Depolymerization of polyethyleneterephthalate in supercritical methanol

Kim

Hwang

Bae

et al. 2001

J of Applied Polymer Sci

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ABSTRACT:The depolymerization of polyethyleneterephthalate (PET) in supercritical methanol was carried out using a batch-type autoclave reactor. The total conversion and the yield of dimethylterephthalate (DMT) increased with rising temperature. The final yield of DMT at 300°C and 310°C reached 97.0% and 97.7%, respectively. The yield of DMT was markedly increased when the methanol density was 0.08 g/cm 3 , and leveled off at higher densities. A kinetic model to describe the depolymerization of PET in supercritical methanol was proposed, where the scission of one ester linkage in PET by a methanol molecule produces one carboxymethyl group and one hydroxyl group. The values of the forward reaction rate constant at different temperatures were determined by comparing the observed time dependence of carboxymethyl group concentration with that calculated by the proposed model. The activation energy was evaluated to be 49.9 kJ/mol, a value close to a literature value (55.7 kJ/mol).

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Depolymerization Reactions of cis-Polyisoprene and Scrap Rubber in Supercritical Toluene

Cited by 9 publications

References 0 publications

Reactions at supercritical conditions: Applications and fundamentals

Reactions at supercritical conditions: Applications and fundamentals

Characteristics and kinetics of degradation of polystyrene in supercritical water

Depolymerization of polyethyleneterephthalate in supercritical methanol

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